continental ichnofossil assemblage from the upper silurian of laurentia the bloomsburg formation of eastern pennsylvania abstract few unequivocal silurian examples of continental ichnofossils have been reported in eastern pennsylvania the upper silurian bloomsburg formation consists of fluvial deposits that have yielded a low diversity ichnofauna described here the rarity of reported silurian continental ichnofauna the quality of the recovered ichnofossil specimens as well as the richly descriptive sedimentary and palaeontological context makes this discovery significant by expanding our understanding of continental ichnodiversity and affirming ichnotaxa reported elsewhere the bloomsburg formation ichnofauna now suggests the possibility that there was a cosmopolitan global ichnofauna of relatively low ichnodiversity in continental especially fluvial paleoenvironnments during the late silurian the fluvially deposited bloomsburg formation is characterized by erosively based fining up sequences from medium grained sandstone to mudstones channel fills are dominated by ripple laminated strata and thinner graded beds floodplain deposits are characterized by thinly laminated graded beds consisting of fine grained siltstones to mudstones thicker laminated mudstones contain reduction halos around ribosome traces mudcracks and some well developed bk horizons of calcisols the bloomsburg fluvial systems thus were low gradient systems that built extensive floodplain deposits and were transitional between low and high sinuosity fluvial systems the strata contain a low diversity invertebrate ichnofauna that includes 1 sinuous traces palaeophycus 2 bilobate oval traces rusophycus 3 slightly sinuous traces with a medial ridge and scratches cruziana 4 two rows of parallel circular or ellipsoid depressions diplichnites 5 substrate penetrating burrows not identified and 6 traces of fossil plant roots palaeophycus and substrate penetrating burrows are the dominant ichnofossils in the bloomsburg formation the bloomsburg formation ichnofauna adds an important datapoint in western laurentia to the distribution of the biota of the freshwater ecosystem of the late silurian it also well represents the epifaunal arthropod ichnofauna of the diplichnites ichnoguild of the scoyenia ichnofacies developed in fluvial environments during the silurian to devonian

a stable isotope study of the migmatitic rocks in the ballachulish contact aureole scotland the highest grade pelitic and semipelitic rocks of the ballachulish aureole are dominantly potash feldspar cordierite biotite hornfelses with widely variable amounts of quartz plagioclase andalusite sillimanite and corundum together with accessory phases on a microscopic scale these hornfelses show textural evidence of the presence of melt whilst on a mesoscopic scale they contain a variety of leucosomes oxygen isotope studies have been carried out on both whole rocks and mineral separates in order to 1 assess the sources of molten and volatile constituents and 2 determine the extents of isotopic homogenization and equilibration data from localities with both restricted and extensive evidence of leucosomes and melt development are compared as well as one locality with petrographic evidence of melt incursion from the igneous complex the whole rock 18o values of the leucosomes 10 5 14 9 are in general similar to the immediately adjacent mesosomes 9 9 14 5 which are typically cordierite and feldspar rich hornfelses isotopic evidence is thus consistent with an in situ partial melt origin for the leucosomes without the substantial addition of externally derived components in the area of extensive melt development the chaotic zone it is possible there was addition of an h2o rich fluid phase 6 13 wt from the igneous complex which resulted in a slight lowering of 18o values by 0 5 1 0 quartz mineral separates were used to assess the degree of local isotopic homogenization in the extensively molten area chaotic zone there is extensive homogenization between rock layers quartz 18o usually within 1 0 whilst in less molten areas 18o quartz has a range of c 3 0 the greater homogenization in the chaotic zone is attributed to the increased degree of melting and infiltration of h2o rich fluid from the igneous complex

phase relationships in buchan facies series pelitic assemblages calculations with application to andalusite staurolite parageneses in the mount lofty ranges south australia low pressure medium to high temperature buchan type regional metamorphism of pelitic rocks in the mount lofty ranges south australia is defined by the development of biotite staurolite andalusite fibrolite prismatic sillimanite and migmatite zones k feldspar makes its first appearance in the prismatic sillimanite zone and here we restrict our discussion to lower grade assemblages containing prograde muscovite concentrating particularly on well developed andalusitestaurolite parageneses in general the spatial distribution and mineral chemical variation of these assemblages accord with the predictions of petrogenetic grids and p t and t xfe pseudo sections constructed from the internally consistent data set of holland and powell 1990 in the system kfmash assuming a h2o 1 although analysed white mica compositions are systematically more aluminous than predicted importantly the stability ranges of most critical assemblages predicted by these grids and pseudo sections coincide closely with p t estimates calculated using the data set of holland and powell 1990 from the mount lofty ranges assemblages with the exception of mn in garnet and zn in one staurolite cordierite muscovite assemblage non kfmash components do not significantly appear to have affected the stability ranges of the observed assemblages an apparent local reversal in isograd zonation in which andalusite first appears down grade of staurolite suggests a metamorphic field gradient concave towards the temperature axis and together with evidence for essentially isobaric heating of individual rocks is consistent with the exposures representing an oblique profile through a terrain in which heat was dissipated from intrusive bodies at discrete structural levels

silurian vegetation stature and density inferred from fossil soils and plants in pennsylvania usa silurian fossil plants range from small vascular plants rhyniophytes to moderately large fungi nematophytes but give little idea of the stature rooting depth and plant density of vegetation on land silurian to earliest devonian palaeosols from the bloomsburg formation show unusually deep bioturbation of several distinct kinds surface ground parallel rhizomes of vascular land plants to 20 cm deep are penetrated by burrows like those of millipedes to 80 cm but the deepest stratum down to 2 m below the surface has features interpreted as bioturbation by fungal hyphae and rhizines plant like axes associated with palaeosols are evidence of vegetation with three distinct tiers above ground as inferred from diameters using allometric scaling equations nematophytes germanophyton psygmophylloides up to 1 3 m tall formed a tier above herbaceous vascular land plants 30 cm and ground cover 2 with spacing 20 cm that closed canopy in seasonally dry wetland palaeosols comparable with modern marsh vegetation vascular land plants of well drained soils in contrast were scattered with bare earth between wetland ground cover was thus more extensive than cover of well drained soils and precursor lichens facilitated early evolution of vascular land plants supplementary material tables of mineral and grain size proportions major element chemical analyses and plant spacing and size are available at http www geolsoc org uk sup18848

demarcating saline water intrusion pathways using remote sensing gis and geophysical techniques in structurally controlled coastal aquifers in southern india application of remote sensing and geographical information system gis with the help of ground truth studies like vertical electrical soundings ves and water quality measurements gave a comprehensive picture on saline water intrusion pathways in the structural controlled aquifers of uppanar and cauvery river systems located in sirkazhi and mannanpandal coastal areas of southern india the detailed geomorphic units and lineaments were mapped using irs liss iii 1 50 000 scale and srtm elevation digital data under gis environment the area is mainly alluvial deposits of holocene age and classified into three major geomorphic units i e fluvial fluviomarine and marine geomorphic units the identified lineaments are mostly trending north northeast nne south southwest ssw northeast ne southwest sw northwest nw southeast se east west ew and east northeast ene west southwest wsw directions some of them are potential for fresh groundwater occurrence and movement the lineaments trending ne sw nne ssw and ene wsw act as pathways for saline water intrusion to the inland the lineament l1 nne ssw trending conformed as a sinisterly shifted fault played a significant role in saline water intrusion the area within the parallel lineaments l2 and l3 oriented ene wsw direction indicates low topography beach ridges paleo channel sinuosity large aerial extent of tidal flats and backwater inundation all the above geomorphic units gave indirect evidence of land subsidence which was confirmed with the help of sub surface geo electrical signals obtained through ves and in situ groundwater quality measurements integrating all the above results the saline water spread and fresh water pockets were identified

strontium and oxygen isotope decoupling in the hercynian trois seigneurs massif pyrenees evidence for fluid circulation in a brittle regime systematic shifts of oxygen isotopic compositions in the higher grade parts of the high temperature low pressure hercynian metamorphic sequence exposed in the trois seigneurs massif have previously been explained as a result of an influx of surface derived water during the prograde part of the metamorphic cycle it has been suggested that this caused a regional lowering of 87sr 86sr in the metamorphic sequence mapping of strontium isotopic compositions across a 15 m meta carbonate horizon in the higher grade pelite psammite sequence shows that strontium isotopic compositions were homogenised over length scales of metres or less during the hercynian metamorphism which brought the carbonate and pelite psammite to oxygen isotopic equilibrium with a common fluid comparison of model pre hercynian 87sr 86sr profiles across the carbonate based on a depositional diagenetic age of 450 ma and initial 87sr 86sr ratio of 0 7086 given by 10 m length scale averaging with the post hercynian 87sr 86sr profile calculated from analysed 87sr 86sr and rb sr compositions implies strontium isotopic diffusion distances of ca 0 4 m in the carbonate and ca 7 m in the pelite psammite the limited sr isotopic diffusion distance of 0 4 0 7 m within the carbonate is compatible with pervasive oxygen isotopic exchange over distances restricted to 4 15 m if fluid strontium concentrations were between 4 and 50 ppm the strontium isotopic transport distances are not compatible with pervasive oxygen isotopic alteration over the observed 5 km regional scale either the flow was perfectly layer parallel or more probably the regional scale alteration of oxygen took place by fluid circulation in the brittle regime early in or prior to the hercynian metamorphic event flow along cracks with incomplete diffusive exchange between fluid and wall rock would allow greater decoupling of oxygen and strontium isotopic transport than pervasive advective transport with local fluid solid equilibrium

organic markers as source discriminants and sediment transport indicators in south san francisco bay california sediment samples from nearshore sites in south san francisco bay and from streams flowing into that section of the bay have been characterized in terms of their content of biogenic and anthropogenic molecular marker compounds the distributions input sources and applicability of these compounds in determining sediment movement are discussed by means of inspection and multivariate analysis the compounds were grouped according to probable input sources and the sampling stations according to the relative importance of source contributions a suite of polycyclic aromatic hydrocarbons pahs dominated by pyrene fluoranthene and phenanthrene typical of estuarine environments worldwide and suites of mature sterane and hopane biomarkers were found to be most suitable as background markers for the bay a homologous series of long chain n aldehydes c12 c32 with a strong even over odd carbon number dominance in the higher molecular weight range and the ubiquitous n alkanes n c24 c34 with a strong odd over even carbon number dominance were utilized as terrigenous markers several ratios of these terrigenous and bay markers were calculated for each station these ratios and the statistical indicators from the multivariate analysis point toward a strong terrigenous signal in the terminus of south bay and indicate net directional movement of recently introduced sediment where nontidal currents had been considered to be minimal or nonexistent and tidal currents had been assumed to be dominant

arthropod trackways from the early devonian of south wales a functional analysis of producers and their behaviour abundant arthropod trackways assigned to diplichnites gouldi are described from the lower old red sandstone early devonian lochkovian of pant y maes quarry brecon beacons south wales the trackways are preserved on bedding planes of finely laminated planar and rippled siltstones the sedimentology of the succession indicates that these units represent bar top and marginal deposits in a braided fluvial setting two trackway types are recognized type a and b comparisons with contemporaneous myriapodous producers favour kampecarid and eoarthropleurid myriapods respectively functional analysis of the trackways indicates that the producers were not using the most efficient stable walking techniques but instead utilized in phase swimming stroke like gaits together with their occurrence on rippled surfaces and lateral displacement of some trackways attributed to currents this indicates that they were produced sub aqueously

a hydrogeochemistry and multi isotope sr o h and c study of groundwater salinity origin and hydrogeochemcial processes in the shallow confined aquifer of northern yangtze river downstream coastal plain china abstract economically developed coastal areas have a high water demand and their groundwater resources can be threatened by salinization many methods and tracers have been used to discriminate the source of salinization because a single method does not yield reliable results in this paper the shallow confined coastal plain aquifer north of the downstream yangtze river in china is used as a case study to investigate the origin of the salinity and the relevant geochemical processes for this aquifer multiple environmental tracers of major ions minor ions br i and isotopes 18 o 2 h 13 c 87 sr 3 h 14 c were used so as to provide reliable conclusions the tds distribution of the aquifer has an increasing trend from below 500 mg l in the inland areas to more than 20 000 mg l around the southeast coastline the water chemical type evolves from hco 3 ca to cl na as the tds increases the results suggest that the groundwater salinity is influenced by seawater intrusion the seawater proportions in the groundwater samples range from 0 07 to 94 41 and show the same spatial distribution pattern as tds the 3 h and 14 c values show that the highest salinity was mainly caused by a seawater transgression around 6000a b p the aquifer is also affected by other hydrogeochemical processes base exchange has enriched ca 2 and depleted k and na sulfate reduction has reduced the concentration of so 4 2 and enriched hco 3 and iodine rich organic matter decomposition has enriched the concentration of i the iodine enrichment also suggests paleo seawater intrusion in addition the precipitation of carbonate minerals has decreased the concentration of ca 2 mg 2 and hco 3 albeit to a limited extent

an introduction to the rhynie chert the terrestrialization of life has profoundly affected the biosphere geosphere and atmosphere and the geological magazine has published key works charting the development of our understanding of this process integral to this understanding and featuring in one of the geological magazine publications is the devonian rhynie chert konservat lagerstatte located in aberdeenshire scotland here we provide a review of the work on this important early terrestrial deposit to date we begin by highlighting contributions of note in the geological magazine improving understanding of terrestrialization and palaeozoic terrestrial ecosystems we then introduce the rhynie chert the review highlights its geological setting the caledonian context of the rhynie basin and its nature at the time of deposition of the cherts which host its famous fossils there follows an introduction to the development of the half graben in which the cherts and host sediments were deposited the palaeoenvironment this represented and the taphonomy of the fossils themselves we subsequently provide an overview of the mineralization and geochemistry of the deposit and then the fossils found within the rhynie chert these include six plant genera which continue to provide significant insights into the evolution of life on land a range of different fungi with recent work starting to probe plant fungus interactions lichens amoebae and a range of unicellular eukaryotes and prokaryotes algae and cyanobacteria and finally a range of both aquatic and terrestrial arthropods through continued study coupled with methodological advances rhynie fossils will continue to provide unique insights into early life on land

ichnology and depositional environment of the middle devonian valentia island tetrapod trackways south west ireland abstract nine tetrapod trackways are described from the middle devonian continental valentia slate formation on the north eastern coast of valentia island in county kerry ireland the trackways occur at three sites dohilla coosadillisk and culoo head the latter two being recorded for the first time morphological and taphonomic analyses of the trackways suggest they were made by populations of similar tetrapods but of varying size body length 0 5 to 1 m width 0 15 to 0 30 m that moved in some cases by terrestrial locomotion and in others possibly by a slow paddling gait while the substrate was submerged by very shallow floodwater sedimentological facies analysis of the trackway bearing sequences has been carried out for the first time and shows that the preserved trackways are associated with the late stages of 1 a principal river channel margin coosadillisk 2 a minor floodplain drainage channel culoo head and 3 a sand rich crevasse splay medial alluvial ridge environment dohilla the valentia island tetrapods inhabited marginal environments of proximal river channels 170 km northwards into the continent from postulated shallow marine habitats as they evolved this capability over a potential 4 5 million year period during the middle devonian

the origin of high sulfate concentrations and hydrochemistry of the upper miocene pliocene quaternary aquifer complex of jifarah plain nw libya the high uncontrolled groundwater extraction in jifarah plain nw libya causes a modification of natural flow systems inducing seawater intrusion and causing groundwater quality deterioration the principal aim of this study is to identify the hydrogeochemical processes in this coastal aquifer in order to verify the main sources of sulfate concentration increase that occurs in the system in order to achieve this aim water samples were collected from 134 sampling wells in the study area and analyzed for the major cations and anions physical and chemical parameters were measured such as water level electrical conductivity ph and temperature the analytical results obtained in the hydrochemical study were interpreted using piper diagram ion correlations with na cl so4 2 cl and tds in conjunction with calculation of the ionic deviations of the conservative freshwater seawater mixture and saturation indices using the phreeqc 2 16 software the large so4 2 anomaly observed in groundwater near the coast was explained by the presence of seawater intrusion and upconing of deep saline water in these areas this conclusion is based on high chloride concentrations the inverse cation exchange reactions and the lower piezometric level compared to sea level inland in sabratah the high so4 2 values are related to gypsum dissolution from the upper miocene formation in the lower part of the upper aquifer these locally high so4 2 concentrations in the south of the study area show overall increase in the upstream direction which also suggests the dissolution of evaporites from the mountain aquifers in the south high so4 2 concentration is also related to the effect of the scattered sebkha deposits in some areas along the coast

first steps on land arthropod trackways in cambrian ordovician eolian sandstone southeastern ontario canada basal terrestrial deposits in the cambrian ordovician nepean formation potsdam group near kingston ontario contain arthropod produced trackways that extend the record of the first arthropod landfall back by as much as 40 m y the presence of large simple cross beds and of wind produced structures including adhesion ripples and wind ripple lamination indicates that the host strata were deposited in an eolian dune field probably in a marginal marine setting the trackways were preserved mainly as undertracks and record the activities of large amphibious arthropods possibly euthycarcinoids

textural and isotopic development of marble assemblages during the barrovian style m2 metamorphic event naxos greece a detailed petrological analysis of the marble assemblages observed within the m2 metamorphic complex on naxos is presented two distinct periods of mineral growth are documented the first is associated with prograde m2 metamorphism and the second with retrograde m2 metamorphism occurring during ductile extensional thinning of the complex the textural and miner alogical characteristics and the carbon and oxygen isotope compositions of each generation are described and the p t xco2 conditions at which these two mineral generations were stable and the compositions of the fluids present during metamorphism are characterised whereas the low variance and stable isotope compositions of prograde siliceous dolomite assemblages are consistent with internally buffered fluid evolution the retrograde mineral generation is shown to have grown as a result of the infiltration of a water rich fluid phase that transported silica al2o3 na2o and feo into the host rocks this observation together with the stable isotope compositions of the retrograde calcite and the fact that occurrences of veins of this type are limited to marbles in the highest grade areas t 600 c of the metamorphic complex suggests that the fluids responsible for vein formation were generated during the crystallisation of melts as the metamorphic complex cooled from peak temperatures the existence of this second generation of minerals has significant implications for previous studies of heat transport by fluid flow on naxos because many of the unusually low 18o compositions of pelites at high grades may be ascribable to the effects of interaction with retrograde m2 fluids rather than with prograde fluids

low pressure regional metamorphism in the omeo metamorphic complex victoria australia the omeo metamorphic complex forms the southern end of the wagga metamorphic belt which is the main locus of palaeozoic low pressure metamorphism in the lachlan fold belt south eastern australia it comprises metamorphosed ordovician quartz rich turbidites originally derived from precambrian cratonic rocks prograde regional metamorphism occurred in the early silurian very soon after sedimentation had ceased the sequence of metamorphic zones with increasing grade is chlorite biotite cordierite andalusite k feldspar and sillimanite k feldspar migmatites occur in the sillimanite k feldspar zone but large bodies of s type granite were derived from rocks underlying the exposed ordovician sequence p and t estimates for the highest grade rocks are t 700 c and p 3 5 kbar indicating a very high p t gradient of 65 c km the high heat flow during prograde metamorphism probably resulted from a combination of a thermal anomaly persisting from a pre metamorphic back arc basin environment and intrusion of hot mantle derived magmas into the lower and middle crust regional retrograde metamorphism coincided with a general reheating of the crust in the siluro devonian accompanied by intrusion of many i type plutons and resetting of the k ar dates of some earlier plutons the omeo metamorphic complex was exposed to erosion at this time

the retrograde p t t path for low pressure granulites from the reynolds range central australia petrological constraints and implications for low p high t metamorphism several aspects of the petrogenesis of low pressure granulite facies rocks from the reynolds range central australia are contentious including a the shape of the retrograde p t time path and whether it is an artefact of repeated thermal events at different p t conditions b the type of regional metamorphism and c the causes of metamorphism granulite facies rocks from the reynolds range group experienced three major periods of mineralogical equilibration metapelitic rocks underwent dehydration melting reactions to form migmatites under peak m2 p t conditions of c 5 0 5 3 kbar and c 750 800 c metapsammitic rocks that did not melt during m2 show spectacular garnet orthopyroxene intergrowths that developed at c 3 5 3 7 kbar and c 700 750 c after penetrative regional deformation but prior to amphibolite facies rehydration in discrete strike parallel zones rehydration occurred within the sillimanite stability field at p t conditions close to the granite solidus c 3 2 3 4 kbar and 650 700 c subsequently the terrane cooled into the andalusite stability field geochronological constraints suggest that a peak m2 conditions were reached at c 1594 ma b the garnet orthopyroxene intergrowths in unmelted metapsammites probably developed between c 1594 ma and c 1586 ma and c upper amphibolite facies rehydration occurred between c 1586 ma and 1568 ma the lack of petrological evidence for multiple dehydration and rehydration of the rocks suggests that the three episodes of mineralogical recrystallization can be linked to yield a single continuous retrograde p t t path of minor initial decompression c 1 5 kbar from the m2 peak followed by cooling c 100 c to the granite solidus over a period of c 26 ma late kyanite bearing shear zones that dissect the terrane are unrelated to this event and formed during the c 300 400 ma alice springs orogeny the shape of the p t t path and the duration of m2 metamorphism suggests that advective heating was not the major cause of high grade metamorphism and that some other longer lived heat source such as the burial of anomalously radiogenic pre tectonic granites is required

the value of iodide as a parameter in the chemical characterisation of groundwaters abstract brackish and saline groundwaters can severely constrain the use of fresh groundwaters their chemical characterisation is important in understanding the hydraulic conditions controlling their presence in an aquifer major ions are frequently of limited value but minor ions can be used iodide in groundwater is particularly significant in many environments due to the presence of soluble iodine in aquifer matrix materials iodide is found in groundwaters in parts of the english chalk aquifer in concentrations higher than are present in modern seawater its presence is considered as a indication of groundwater residence and is of use in the characterisation of fresh as well as saline waters under certain circumstances modern seawater intrusion into aquifers along english estuaries produces groundwaters which are easily identified due to iodide enrichment from estuarine muds in other environments iodide concentrations are of value in distinguishing between groundwaters in limestones and shaly gypsiferous rocks as shown by a study in qatar while in an alluvial aquifer study in peru iodide has been used to identify groundwaters entering the aquifer from adjacent granodiorites

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

solute recycling an emerging threat to groundwater quality in southern india summary groundwater from crystalline aquifers is abstracted at large rates for paddy irrigation in southern india resulting in widespread over exploitation of the resource detailed field studies at watershed scale have shown that basin closure is happening i e groundwater contribution to base flow has stopped and irrigation return flow can contribute to as much as half of the aquifer recharge studies in other semi arid regions have shown that irrigation return flow through a process known as solute recycling can contribute significantly to aquifer salinisation to evaluate the impact of this process in the southern india context a lumped reservoir model has been designed in order to simulate long term trends of piezometric levels and solute concentrations at watershed scale the model is applied to the well studied watershed of maheshwaram 53 km2 located 40 km south of hyderabad it can reproduce qualitatively watershed average groundwater levels and chloride concentrations inferred since 2001 that shows a progressive buildup simulation of the period 2010 2044 indicates that forecasted reservoir concentrations are very sensitive to aquifer mixing efficiency in the case of complete mixing base flow that activates after rainy years may export significant solute mass and level off aquifer concentration to acceptable levels in the more realistic case of incomplete mixing diluted base flow will export less solute and progressive solute mass buildup continues throughout the simulation period to end up with concentrations close to the ones that makes water no longer suitable for irrigation final aquifer concentrations may become even higher with scenarios that accelerate the lowering of the water table such as higher pumping rates decrease in daily rainfall or increase in daily evaporation these simulations show that solute recycling may have a significant negative impact on groundwater quality in southern india especially in aquifers located in semi arid hard rock areas where the main source of irrigation is provided by groundwater

hydrochemical and isotopic characterisation of groundwaters to define aquifer type and connectivity in a subtropical coastal setting fraser coast queensland physico chemical parameters major ion chemistry and isotope composition of surface and groundwaters were determined in forested coastal catchments and adjacent coastal plains results showed obvious characterisation related to physical and hydrological setting and highly variable spatial differences reflecting the complexities of these areas all these coastal waters are dominated by na cl and fall on a common dilution line hydrochemical grouping is largely due to anionic differences cl so4 and hco3 although na and mg ratios also vary six major hydrochemical facies were determined for groundwaters compositional differences are largely related to aquifer material and level of confinement for coastal groundwaters important are tidal effects and proximity to the shoreline differentiation for surface waters is mainly by drainage morphology flow regime plus proximity to the coast connectivity between water bodies is reflected by minor base flow to catchment streams including with flood plain wetlands but mostly occurs in low lying zones where there is mixing of fresh and saline water within surface water and subterranean estuaries or by seawater intrusion enhanced by overuse oxygen and hydrogen isotopic data for confined and semi confined groundwaters along the coast indicates local recharge fresh surface waters in the elevated catchments are shown to be sourced further inland plus have experienced evaporation

application of ert and gpr for demarcating the saline water intrusion in coastal aquifers of southern india to investigate the pathways for saline water intrusion into fresh water aquifers the electrical resistivity tomography ert and ground penetrating radar gpr have been pooled for nagapattinam area of southern india the study area has two river sub basins uppanar river basin urb and cauvery river basin crb ert carried out in urb shows very low resistivity ranging from 0 003 to 1 5 m at shallow depth indicating saline water whereas the resistivity ranges away from the river stream are 1 7 5 0 m cauvery river basin shows resistivity range varying from 3 6 to 150 m indicating a salt fresh water mix similarly few gpr profiles were carried out along ert profiles to confirm the saline water intrusion and its pathway besides the hydrochemical study reveals the same signature of saline and fresh water zones in both river basins water samples collected during field investigation show high total dissolved solids tds content near urb and crb river course ert data was correlated with gpr data to distinguish fresh and saline water zones more accurately urb has more saline water zones at shallow depth nearer to river course and intermediate depth of saline water zones away from the river course while crb is having fresh water towards the inland

exploring the aftermath of the cambrian explosion the evolutionary significance of marginal to shallow marine ichnofaunas of jordan the middle cambrian hanneh member of the burj formation and the middle to upper cambrian umm ishrin formation of the dead sea area jordan contain well preserved and abundant ichnofaunas trace fossils are present in a wide variety of depositional environments from tide dominated shelf to prodelta delta front and interdistributary bay tidal flats twelve trace fossil assemblages have been identified within a number of sequence stratigraphic settings namely early transgressive subtidal dune and bar complex late transgressive isolated dune patches and dune field abandonment highstand deltaic progradation and forced regressive deltaic progradation these ichnofaunas provide information that helps us to understand the nature of cambrian ecosystems in the aftermath of the cambrian radiation the jordan ichnofaunas display evidence of firm ground conditions at or near the sea bottom these include 1 well preserved scratch marks in most cruziana and rusophycus ichnospecies 2 adhering gyrolithes polonicus burrows and 3 unlined passively filled diplocraterion isp penetrating into underlying mudstone whereas the diplocraterion isp occurrences are a classic example of the glossifungites ichnofacies linked to erosional exhumation the firmground g polonicus is associated to a maximum flooding surface with no erosion involved the trace fossil suites dominated by trilobite structures are firmground examples of the cruziana ichnofacies raising issues with respect to the substrate affinities of this ichnofacies which is typically considered indicative of softgrounds our study underscores evolutionary controls on this ichnofacies suggesting that lower paleozoic occurrences which are dominated by trilobite trails and trackways reflect firm substrates and younger ones represent the typical softground examples the occurrence of abundant bilobate trace fossils scratch marks and trackways in interdistributary bay tidal flats within a braidplain delta complex in the umm ishrin formation provides evidence that arthropods were able to foray into marginal marine brackish water settings during the cambrian analysis of the tiering structure indicates relatively simple communities and limited use of the infaunal ecospace low energy fully marine and marginal marine ichnofabrics are dominated by shallow tier deposit and detritus feeding trace fossils deep tier structures of detritus feeders are present in ichnofabrics from fully marine low energy settings whereas deep tier trace fossils of suspension feeders are dominant in high energy subtidal zones

non tetrapod trace fossils from the middle devonian tetrapod tracksite at zachelmie quarry holy cross mountains poland abstract the middle devonian eifelian dolomites exposed in the zachelmie quarry holy cross mountains southern poland contain the earliest fossil record of tetrapods low diversity but unique assemblages of trace fossils characterize the track bearing interval within the lower complex of the wojciechowice formation the reconstructed environment of the trace fossil rich beds includes ephemeral lakes and or shallow water lagoons separated from an open marine area by sparsely vegetated islands and spits the most abundant non tetrapod trace fossils from these beds are large horizontal to vertical burrows and dish circular to oval shaped shallow depressions the burrows are abundant on the upper surfaces of thick dolomicritic beds especially in some palaeosol levels but they are also associated with tetrapod trackways large semi aquatic or terrestrial animals e g arthropods or vertebrates most likely produced these burrows the circular to oval shaped depressions observed on a large surface and other smaller isolated blocks from the same stratigraphical level are interpreted as fish feeding nesting resting traces piscichnus sanctacrucensis isp nov is proposed as a new ichnospecies of the oval shaped fish trace fossil from the middle devonian of poland a single medium sized undichnia specimen a fish swimming trace is associated with the piscichnus traces the described trace fossils provide new insight into the palaeoecology and taphonomy of the middle devonian tetrapod tracksite from poland and clarify remaining controversies regarding the interpretation of some poorly preserved trace fossils from the zachelmie quarry

differentiation of palaeomarine and modern seawater intruded salinities in coastal groundwaters of karaikal and tanjavur india based on inorganic chemistry organic biomarker fingerprints and radiocarbon dating abstract hydrosalinity evolution is examined in the karaikal and tanjavur coastal aquifers situated about 300 km south of madras tamil nadu india ancient and modern sources of solutes in groundwaters have been differentiated using hydro geochemical data environmental radioisotope dates and organic biomarkers results from different techniques show consistently that the pliocene aquifer possesses characteristic palmitoleic and oleic acid biomarkers apparent 14 c ages of more than 20 000 years and high i cl ratio the modern marine estuarine intruded groundwaters in the alluvial aquifer display relatively younger apparent 14 c ages modern to 3000 years enriched potassium ion low i cl ratio and contain vaccenic and hopanoic acid biomarkers and they also tend to display transient changes in chemical characteristics these results have practical importance with regard to identifying and controlling seawater intrusion in coastal areas

ichnological signatures of shallow freshwater lakes in the glacial itarare group mafra formation upper carboniferous lower permian of parana basin s brazil abstract the upper carboniferous lower permian glacigenic deposits of the itarare group parana basin are widely known and cover an extensive area in the southern brazil these deposits consist of different arrangements of massive shales diamictites rhythmites and fine to medium grained sandstones with trough cross stratification five genetically distinct thickening locally coarsening upward successions of regular rhythmites can be distinguished in the mafra rio negro region santa catarina and parana states southern brazil representing the landward portion of an incised valley filled during deglaciation a low diversity invertebrate ichnofauna composed of a freshwater shallow burrow dominated suite and trackway dominated suite occurs in these rhythmites the freshwater shallow burrow dominated suite is composed of cochlichnus anguineus cruziana cf problematica gordia arcuata gordia marina hormosiroidea meandrica rusophycus cf carbonarius and treptichnus pollardi as well as undichnia consulca and intermittent rusophiciform traces it represents a mermia ichnocoenosis and occurs in the rhythmites of the upper sets commonly overlapped by d gouldi and d biformis in palimpsest preservation d gouldi and d biformis compose the trackway dominated suite which occur in all ichnofossiliferous paired mudstone siltstone of the basal sets of the rhythmite succession and in almost all of the upper sets it represents an atypical scoyenia ichnocoenosis and is generally preserved over microbially induced wrinkle structures the rhythmic deposition suggests distal underwater gravity flow deposits filling shallow lakes or ponds in depressed areas the siltstones deposited by melting currents and the mudstones by sediment fall out after the flux ceased the abundant wrinkle structures suggest quiet waters the overlying deposits bearing a brackish water ichnofauna and marine fossils suggest a coastal setting connected with the sea although atypical the occurrence of a scoyenia ichnocoenosis in almost all ichnofossiliferous rhythmite couplets preserved over wrinkle structures or overlapping mermia ichnocoenosis suggests that these shallow lakes were episodically dried up at least partially the present data allow interpreting the regular ichnofossiliferous rhythmites of the mafra formation as deposited in shallow lakes or ponds developed in outwash plains at the landward side of a fjord embayment during deglaciation

early cambrian metazoans in fluvial environments evidence of the non marine cambrian radiation davies and gibling 2012 1 raise concerns that sediments hosting trace fossils in the early cambrian middle member of the wood canyon formation which we have interpreted as fluvial may be marine in origin they suggest that in the absence of body fossils or specific minerals it may not be

cambrian ordovician orogenesis in himalayan equatorial gondwana an early paleozoic tectonic event the kurgiakh orogeny has long been known from the western tethyan himalaya and it is conspicuously recorded by an angular unconformity between cambrian marine shelf deposits and coarse ordovician conglomerate as well as widespread granitic plutons although the lateral extent of this event is poorly known two regions in the central and eastern himalaya the kumaon of india and klippen of bhutan contain conglomerate units that may be correlative with this event in the kumaon the ralam formation which contains a basal polymictic conglomerate unit with detrital zircon grains as young as ca 512 ma is overlain by sandstone containing the arthropod walking trace diplichnites gouldi an ichnospecies known from ordovician and younger strata the late early cambrian trilobite redlichia sp recovered from the underlying martoli group indicates that the conglomerate is post early cambrian and based on stratigraphic analysis also likely records the kurgiakh orogeny in central bhutan the lower paleozoic succession contains conglomerate units with monomictic quartz sandstone clasts and less mature sandstone matrix these units have also been assigned to a variety of ages but rocks that apparently underlie these strata contain the furongian late cambrian zonal trilobite kaolishania granulosa here we show that detrital zircon ages of a conglomerate clast no grains younger than ca 781 ma are distinctly older than those of the matrix which contains a large peak at 490 500 ma thus these conglomerate units are also potential lateral correlatives of the ordovician conglomerate deposits of the western himalaya our paleontological and geochronologic data suggest that the kumaon and bhutan conglomerate units and possible equivalents in tibet correlate with those of the western himalaya this increases their known along strike extent by over 1000 km bringing the total extent to 1200 km thus the kurgiakh orogeny spanned much of the himalayan orogen along the northern gondwanan margin and reflected a widespread tectonic reorganization of the peri gondwanan realm to andean type margins recent work indicates that it also likely extended into the lhasa block and both the north and south china blocks this event was associated with widespread ca 500 ma arc related plutonism recorded in the himalaya and with abundant detrital zircon grains of that age in younger himalaya strata based on current fossil data the duration of the hiatus associated with the cambrian ordovician boundary which separates pre and postdeformational strata ranges from 22 to 36 m y available geochronological data do not provide greater constraint if the event was close in age to the depositional age of the ordovician molasse then the main phase of tectonic uplift erosion and deposition may have been much later than the presumed cambrian ordovician boundary interval age of ca 485 ma

water fluxed melting of the continental crust a review abstract water fluxed melting also known as fluid or water present melting is a fundamental process in the differentiation of continents but its importance has been underestimated in the past 20 years during which research efforts focused mostly on dehydration melting reactions involving hydrate phases in the absence of a separate aqueous phase the presence of a free aqueous phase in anatectic terranes influences all major physical and chemical aspects of the melting process from melt volumes viscosity and ability to segregate from rock pores to melt chemical and isotopic composition a review of the literature shows that melting due to the fluxing of aqueous fluids is a widespread process that can take place in diverse tectonic environments active tectono magmatic processes create conditions for the release of aqueous fluids and deformation driven transient high permeability channels capable of fluxing high temperature regions of the crust where they trigger voluminous melting water fluxed melting can be either congruent in regions at the water saturated solidus or incongruent at suprasolidus p t conditions incongruent melting reactions can give rise to peritectic hornblende or to nominally anhydrous minerals such as garnet sillimanite or orthopyroxene in this case the presence of an aqueous phase is indicated by a mismatch between the large melt fraction generated and the much smaller fractions predicted in its absence the relatively small volumes of aqueous fluids compared to that of rocks imply that melting reactions are generally rock buffered fluids tend to move upwards and down temperature however there are cases in which pressure gradients drive fluids up temperature potentially fluxing suprasolidus terranes crustal regions at conditions equivalent to the water saturated solidus represent a natural impediment to the up temperature migration of aqueous fluids because they are consumed in melting reactions in this case continued migration into supra solidus terranes take place through the migration of water rich melts thus melts become the transport agent of water into supra solidus terranes and responsible for water fluxed melting other processes such as the relatively rapid fluid migration through fractures also allow regional aqueous fluids to by pass the water saturated solidus fluid trap and trigger melting above solidus conditions when aqueous fluids or hydrous melts flux rocks at supra solidus conditions they equilibrate with the surroundings through further melting decreasing water activity and giving rise to undersaturated melts it is in these conditions that hornblende or anhydrous peritectic phases are stabilized unlike dehydration melting the melt fraction generated in this case is not limited by the water contained in hydrous minerals but by the volume of water added to the system unlike melting at the water saturated solidus these melts are capable of rising without freezing and do give rise to upper crustal granitic bodies

evolution of the freshwater ecosystem the fossil record abstract the freshwater ecosystem may be as old as most life although freshwater life is taxonomically impoverished in comparison with marine and terrestrial biotas and ultimately derived from them it cannot be assumed that freshwater communities have necessarily been less complex in the geologic past than they are today although it is clear they have undergone a number of major changes freshwaters contain not only their own ancient and peculiar groups some with ancestries as far back as the middle paleozoic but they have been a theater for adaptive radiation of more recent immigrants from the land or sea and a way station for still other groups that passed through both from sea to land and the reverse this review summarizes first fossil records in freshwaters for many of these organisms and examines the question of the changing complexity of the freshwater ecosystem through time by looking at the fossil record of continental aquatic habitats

short paper the subaerial setting of the ordovician borrowdale volcanic group english lake district most ordovician volcanic rocks of southern britain were produced in volcanic island settings and the borrowdale volcanic group bvg of the lake district has traditionally been interpreted in this way however a review of lithofacies associations in the bvg indicates a subaerial environment pyroclastic surge deposits thin welded tuff beds lava flow morphologies abundant erosional unconformities and fluviatile and laharic facies indicate widespread subaerial emplacement volcano tectonic subsidence aided preservation of subaerial facies although a preservation bias favoured lacustrine deposits erosional unconformities above subaerial aggradational volcanic sequences are to be expected so the sub windermere group unconformity does not necessarily imply tectonic uplift

the nature and distribution of fluids during amphibolite facies metamorphism naxos greece on the basis of fluid inclusion evidence pervasive influx of deep seated co2 rich fluids has been invoked to account for mid to upper amphibolite facies m2b metamorphism on the island of naxos cyclades greece in this paper mineral devolatilization and melt equilibria are used to constrain the composition of both syn and post peak m2b fluids in the deepest exposed levels of the metamorphic complex the results indicate that peak m2b fluids were spatially and compositionally heterogeneous throughout the high grade core of the complex whereas post peak m2b fluids were generally water rich the observed heterogeneities in syn m2b fluid composition are inconsistent with pervasive co2 flushing models invoked by previous workers on the basis of fluid inclusion evidence it is likely that few co2 rich fluid inclusions on naxos preserve fluids trapped under peak metamorphic conditions it is suggested that many of these inclusions have behaved as chemically open systems during the intense deformation that accompanied the uplift of the metamorphic complex a similar process may explain the occurrence of some co2 rich fluid inclusions in granulite facies rocks

on the causes of 18 o depletion and 18 o 16 o homogenization during regional metamorphism the east humboldt range core complex nevada previous stable isotope studies at lizzies basin revealed that metasedimentary rocks are 18o depleted relative to protolith values particularly in the lower parts of the section lower zone where the rocks are also isotopically homogeneous on a scale of hundreds of meters quartz 18o 9 0 to 9 6 per mil in contrast metasedimentary rocks at higher levels at lizzies basin upper zone are less 18o depleted and more heterogeneous in 18o in order to understand more fully the isotopic evolution of this terrane a series of detailed meter scale traverses across various metamorphic and igneous lithologies were completed at lizzies basin and at the structurally higher angel lake locality traverses in the lizzies basin lower zone and in the lower parts of angel lake angel lake lower sequence across various silicate lithologies including abundant granitoids reveal similar degrees of homogeneity although the average 18o values are higher at angel lake in contrast traverses which include substantial thicknesses of marble and calc silicate gneiss and very little granitoid have more heterogeneous quartz 18o values 11 9 to 13 4 per mil and also have a higher average 18o 12 9 per mil than observed elsewhere the scale of 18o 16o homogeneity in quartz observed at lizzies basin and angel lake meters to hundreds of meters requires fluid mediated isotope exchange which accompanied tertiary metamorphism there is a correlation between the degree of 18o depletion in metasedimentary rocks 18o 16o homogenization between lithologies and the proportion of granitoids leucogranites in particular within any part of the section and a corresponding anticor relation with the proportion of marble this points to a causal relationship whereby the leucogranites as well as the tertiary hornblende diorite and biotite monzogranite acted as both a relatively low 18o reservoir and a source of fluids to enhance exchange while the marbles hindered isotope deplction and homogenization by acting as relatively high 18o reservoirs and impermeable layers material balance calculations help delineate the plausible mechanisms of exchange between granitoids and metasediments single pass infiltration of magmatic fluids from the granitoids is not capable of reproducing all of the observations fluidmediated exchange by convective recirculation of magmatic fluids on a scale of meters is the mechanism which explains all of the observations the generalized model for the isotopic evolution of the east humboldt range core complex provides and excellent opportunity to establish the main causes and controlling factors of 18o depletion and 18o 16o homogenization during regional metamorphism

oxygen isotopic study of late mesozoic cooling of the mount barcroft area central white mountains eastern california the middle jurassic barcroft mafic granodiorite and late cretaceous ternary minimum mcafee creek granite are important components of the igneous arc sited along the sw north american margin bulk rock analyses of 11 samples of the metaluminous i type barcroft comagmatic suite have an average 18o value of 7 4 0 6 all values 1 four barcroft specimens average end 3 6 1 8 87sr 86sr 0 707 0 001 the pluton consists of petrochemically gradational ca amphibole rich gabbro diorite granodiorite metadiorite and rare alaskite aplite for most of the pluton oxygen isotope exchange of quartz feldspar s biotite and ca amphibole accompanied local deuteric alteration eight specimens of slightly peraluminous granitic rocks of the muscovite bearing mcafee creek series have an average 18o of 8 6 0 5 four mcafee type samples average end 7 8 1 7 87sr 86sr 0 711 0 004 for both plutons bulk rock evidence of exchange with near surface water is lacking suggesting 5 10 km cooling depths barcroft minerals exhibit regular oxygen isotopic partitioning from high to low 18o in the sequence quartz plagioclase k feldspar amphibole biotite along the se margin of the pluton quartz and biotite in lower cambrian quartzites are higher in 18o and show slightly larger fractionations than igneous analogues exchange with fluids derived from these heated contact metamorphosed country rocks increased bulk 18o 16o ratios of barcroft border rocks and constituent plagioclase subsolidus tremolite actinolite especially of granitic dikes transecting the wall rocks oxygen isotope thermometry for seven barcroft pluton quartz amphibole and six quartz biotite pairs indicate apparent subsolidus temperatures averaging 519 49 c quartz plagioclase pairs from two barcroft granodiorites yield values of 519 and 515 c a quartz biotite pair from a quartzite adjacent to the barcroft pluton yields an apparent temperature of 511 c in agreement with estimates based on contact metamorphic parageneses except for its se margin barcroft pluton silicates evidently exchanged oxygen isotopes under local deuteric conditions compatible with ca amphibole thermobarometric analyses areal distributions for quartz plagioclase quartz amphibole and quartz biotite pairs reveal that putative annealing temperatures are lowest in ne trending axial portions of the barcroft body so it simply cooled inwards intrusion 70 million years later by the mcafee creek granite had no discernable effect on 18o values of barcroft minerals and bulk rocks

ordovician volcano tectonics in the english lake district although the major late caledonian acadian deformation of the british slate belts south of the iapetus suture took place in early devonian time two intra ordovician unconformities are present in the lower palaeozoic succession of nw england which have been interpreted as due to regional compressional events these unconformities are at the base and top of the caradocian borrowdale volcanic group bvg and have been associated respectively with a pre bvg orogenic cycle affecting the early ordovician skiddaw group sg and with pre bala folding of the bvg a problem has been that no consistent sets of minor structures attributable to these deformations have been demonstrated in the skiddaw group recent advances in understanding of the volcanic history of the lake district lead to a radical reinterpretation of the significance of these two unconformities in the pre bala intra caradocian deformation of the bvg flexuring is now seen to be much less important than volcano tectonic faulting and block tilting associated with caldera collapse and the eruption of voluminous ash flows in the upper part of the pile foundering of the volcanic edifice accounts for the preservation of this thick subaerial sequence beneath the overstepping late ordovician marine deposits more tentatively we suggest that the unconformity beneath the borrowdale volcanic group reflects regional uplift due to buoyancy effects associated with the generation of andesitic melt by iapetus subduction and its rise through the over riding wedge of continental lithosphere several such mechanisms have been proposed to account for the topographic elevation of present day continental margin magmatic arcs the new model removes the evidence for ordovician n s regional compression from the geological record of nw england and this has geotectonic implications the evidence for late ordovician collision is weakened and the direction of iapetus subduction beneath southern britain may not have been southward

fluid absent melting and the roles of fluids in the lithosphere a slanted summary abstract the presence or absence nature and compositions of lithospheric fluids are crucial factors in the evolution of igneous and metamorphic rocks despite this confusion still surrounds perceptions of the degrees of fluid involvement in many geological settings however experimental and field investigations constrain these roles and we are able to make some valid generalizations studies of prograde metamorphism have highlighted the spatial heterogeneity of fluid concentrations in many crustal environments this commonly indicates internal lithological control of volatile activities under fluid present conditions crustal fluids do not appear to mix readily fluid flow is generally structurally or lithologically controlled the transition from amphibolite to granulite facies is characterized by a decrease in ah2o as well as a temperature increase in many terranes these phenomena correlate with the appearance of migmatites some granulites are not migmatitic but have chemical and mineralogical characteristics of melt depleted restites this indicates efficient extraction of melts incongruent melting reactions involving the breakdown of crystalline hydrates in crustal rocks produce granitoid melts plus denser restites that are nearly or actually anhydrous experimental and theoretical treatments of fluid absent melting show that micas and amphiboles decompose at 700 to 900 c for mid to lower crustal pressures the melts resemble the compositions of s and i type granitoids pervasive aqueous fluids could not generally have been present during this melting since exposed granulite terranes are not characterized by high melt proportions and the magmas themselves are water undersaturated likewise the general presence of very h2o poor pervasive fluids is unlikely since this would allow only subsolidus dehydration at normally attainable crustal temperatures in this case the amphibolite granulite transition is possible at relatively low temperatures and the resultant rocks would not contain evidence of in situ melting the granulite granite connexion and effective crustal differentiation seem viable only during high temperature fluid absent metamorphism data on continental geotherms show that the lower crust is not entirely granulitic granulites are produced in regions of anomalously high heat flow the mantle connexion thus inferences on the nature of the lower crust should not be entirely based on studies of exposed granulite terranes mineral assemblages in eclogites also indicate widespread internal buffering of volatile activities and probable fluid absent conditions mantle derived basaltic magmas too are volatile bearing and it is plausible that volatile fixing phases also occur in the mantle volatiles may largely be introduced into the mantle through subduction processes and only released during the melting attending the breakdown of hydrous minerals as in the crust

the role of water retention in the anatexis of metapelites in the bushveld complex aureole south africa an experimental study highly restitic metapelites occur at the contact of the rustenburg layered suite bushveld complex on the basis of previous experimental studies the high 60 degrees of melting required to form these restites via fluid absent processes could not have occurred at the maximum temperatures estimated in the aureole 800 c we have investigated their formation by partial melting experiments using a medium grade and a low grade metapelitic hornfels from the aureole that are isochemical except for water content 1 2 and 4 4 wt h2o respectively the partial melting experiments 700 1000 c at 3 kbar demonstrate strongly contrasting behaviour for the two samples for the higher grade starting composition only minor melting occurred up to 800 c 50 required a temperature of 1000 c in contrast for the lower grade starting composition extensive melting 50 65 and the presence of a similar restite assemblage to that observed in the aureole rocks was achieved in all experiments run at temperatures 750 c in the absence of fluid infiltration the results suggest that during rapid heating in the innermost parts of high temperature contact aureoles extensive partial melting may occur at relatively low temperatures if the fluid from the low grade protolith is still resident in the system this locally renders metapelitic rocks less dehydrated and hence more fertile than if heating had been slower

an extended episode of early mesoproterozoic metamorphic fluid flow in the reynolds range central australia the products of metamorphic fluid flow are preserved in zones within the marbles and metamorphosed semipelites of the upper calcsilicate unit in the granulite portion of the late palaeoproterozoic reynolds range group northern arunta block central australia the zones of retrogression characterized by minerals such as wollastonite grossular and clinohumite local resetting of oxygen isotopic compositions and local major element metasomatism were channelways for water rich fluids derived from granulite facies metapelites u th pb isotopic ages measured by the shrimp ion microprobe on zircon and monazite from a granulite facies semipelite an early semiconcordant aluminous quartz rich fluid flow segregation and a late discordant quartz rich segregation record some of the extended thermal history of the area zircon cores from the semipelite show its likely protolith to be an igneous rock 1812 11 ma old itself derived from a source containing zircon as old as 2 2 ga low th u overgrowths on the zircon grew during granulite facies metamorphism at 1594 6 ma monazite cooled to its blocking temperature at 1576 8 ma zircon cores from the semiconcordant segregation are dominantly 2 3 ga old indicating that the source of the fluids was not the particular metamorphosed semipelite studied two generations of low th u overgrowths on the zircon give indistinguishable ages for the older and younger of 1589 8 and 1582 8 ma respectively the monazite age is the same 1576 12 ma zircon from the late discordant segregation gave 1568 4 ma fluid flow occurred for at least 18 3 ma and ended 26 3 ma after the peak of metamorphism suggesting a very slow cooling rate of 3 c ma 1 the last regional high grade metamorphism in the reynolds range occurred at 1 6 ga not 1 78 ga as previously thought the high grade event at 1 78 ga is a separate event that affected only the basement to the reynolds range group

fluid rock interaction during low pressure polymetamorphism of the reynolds range group central australia marbles and metapelites from the reynolds range group central australia were regionally metamorphosed at low pressure during m at 6 go m ranged in grade from gnenschist to granulite fades along the length of the reynolds range and overprinted l 78 ga granites and their contact aureoles in the reynolds range group metasediments at all m 2 grades the marbles and metapelites have highly variable oxygen isotope ratios marbles 5i8o carb 14 20 o metapelites b180 6 14 o similarly l 78 ga granites have highly variable oxygen isotope ratios 8i8o 5 13 o with the lowest values occurring at the granite margins in all rock types the lowest oxygen isotope values are consistent with the infiltration of channelled magmatic and or meteoric fluids the variable lowering of oxygen isotope values resulted from pre mi2 contact metamorphism and fluid rock interaction around the l 78 ga granites in contrast mineral assemblages in the marbles define a trend of increasing xco with increasing grade from 0 05 gnenschist fades to 0 71 0 granulite fades this together with the lack of regionally systematic resetting of oxygen isotope ratios implies that there was little fluid rock interaction during prograde regional metamorphism key word law pressure polymetamorphism fluids stable isotopes petrology

hydrogeochemistry and quality of groundwater of coastal unconfined aquifer in amol ghaemshahr plain mazandaran province northern iran groundwater of the unconfined aquifer 1 100 sq km of a two tier coastal aquifer located in the amol ghaemshahr plain mazandaran province northern iran is classified into fresh and brackish water types fresh groundwater fgw samples n 36 are characterized by ca2 na mg2 k and hco3 cl so4 2 no3 spearman s rank correlation coefficient matrices factor analysis data values of the c ratio av 0 89 and cai and values of the molar ratios of ca2 hco3 ca2 so4 2 mg2 hco3 and mg2 so4 2 indicate that the ionic load in the fgw is derived essentially from carbonic acid aided weathering of carbonates and aluminosilicates saline sea water trapped in the aquifer sediments now admixed with the groundwater and ion exchange reactions values of the cai and na cl molar ratio suggest that the part of the ca2 mg2 content in 23 fgw samples is derived from clay minerals of the aquifer matrix and part of the na content in 20 12 and 3 fgw samples is derived respectively from alkali feldspar weathering clay minerals of the aquifer matrix and rain water and or halite brackish groundwater bgw samples n 4 contain cl as the dominant anion and their average total ionic concentration 38 65 meq l is 1 79 times higher than that of the fgw samples 21 50 meq l bgw pockets were generated by non conservative mixing of fgw with the upconed saline water from the underlying saline groundwater zone of the semi confined aquifer along bore wells involved in excessive extraction of groundwater from the unconfined aquifer groundwater belongs essentially to high salinity low sodium irrigation water class

reactivity of organic matter in aquifer sediments geological and geochemical controls reduction rates in aquifers are commonly carbon limited but little is known about the molecular composition and degradability of sedimentary organic matter som in aquifer sediments the composition source and degradation status of som in aquifer sediments of fluvio glacial pleistocene and shallow marine pliocene origin were determined using flash pyrolysis gas chromatography mass spectrometry incubation experiments 106 d were used to assess the reactivity of som towards molecular oxygen a dominance of lignin derived components and long chain odd over even predominant alkanes indicate that terrestrial higher land plants were the main source of som even in the shallow marine sediments while bacterial lipid derived hopanoids and iso and anteiso c15 and c17 fatty acids indicate a minor contribution of microbial biomass no compositional difference was observed between som present in the fine 63 m and coarse fraction 63 2000 m a significant part of som was not present as low molecular weight compounds but was macromolecularly bound for the fluvio glacial sediments a relatively higher abundance of resistant macro molecular compounds was in agreement with stronger signs of aerobic lignin alkane and hopanoid oxidation the more degraded status of som in the fluvio glacial sediments was consistent with their significantly lower som mineralization 2 6 during incubation as compared with the shallow marine sediments 9 14 the reactivity towards oxygen of som was controlled by the extent of past aerobic oxidation not the age of som but the extent of oxygen exposure during syn and postdepositional conditions seems most important in affecting the degradation status of som in aquifer sediments and thus their ability to reduce oxidants copyright 2004 elsevier ltd

death near the shoreline not life on land ordovician arthropod trackways in the borrowdale volcanic group uk the borrowdale volcanic group of northern england hosts late ordovician arthropod trackways that are frequently cited as the earliest unequivocal evidence for animal life on land and provides a key geological locality for our understanding of myriapod evolution and terrestrialization original fieldwork at the site has identified four additional bedding surfaces that yield 121 new trackways of a total 158 known individuals permitting better sedimentological and paleoecological contextualization of the trackways contrary to published claims none of the trackways occur in sandstones but are invariably preserved on dacitic tuff bedding planes trackway morphology comprises either short straight segments with discernable footprint impressions diplichnites long looping traces suggesting dragging and footprint amalgamation diplopodichnus or transitional forms morphometric comparison of the diplopodichnus with fossil and recent mortichnia death traces suggests they record immediate pre mortem locomotion of dying myriapods and modern analogue reveals mechanisms by which abundant volcanic ash would have elevated arthropod mortality rates sedimentary structures including wave ripples bedding sags and detached large scale ball and pillow structures show that the tuffs were deposited subaqueously one instance where trackways intermittently traverse 3 5 cm tracts of subaerially exposed wave ripple crestlines attests that the tracemakers were capable of surviving out of water over limited distances the low diversity ichnofauna has greater similarity with other cambrian and ordovician sites recording semi subaqueous pioneer tracemakers than it does with the earliest fully terrestrial ichnofaunas from the silurian and devonian

late ordovician glaciation initiated by early land plant evolution and punctuated by greenhouse mass extinctions abstractlate ordovician hirnantian glaciation indicated by periglacial paleosols tillites and glacial pavements in saharan africa has been attributed to advances in weathering and carbon sequestration due to evolution of early land plants in the same way that devonian permian glaciation has been attributed to evolution of forests and quaternary glaciations to evolution of grasslands two problems for carbon cycle explanations of this glaciation are an hirnantian co2 greenhouse estimated at 4035 ppmv from mass balance models and possibly related hirnantian mass extinctions this estimate of high co2 is a 10 m yr average here evaluated against high resolution sequences of paleosols that give estimates not only of co2 but also of paleoclimate and vegetation through the late ordovician katian paleosols of the eastern united states show increases in depth and in degree of carbon consumption and storage comparable with those preceding glaciation of the devonian permian and quaternary early thalloid l

a pre caldera plateau andesite field in the borrowdale volcanic group of the english lake district the 6 km thick ordovician borrowdale volcanic group is readily divisible into a lower 2 2 2 7 km thick predominantly pre caldera succession dominated by basalt andesite and dacite sheets and an upper succession of caldera related ignimbrites and volcaniclastic sedimentary rocks of c 3 km thickness the lower borrowdale volcanic group rocks here included within a single lithostratigraphical unit the birker fell formation affords a well exposed section through a pre caldera sequence the birker fell formation is dominated by andesites which comprise 60 of the stratigraphy thin sequences of reworked volcanic detritus are commonly interbedded with the andesites locally there are thicker units of volcaniclastic sedimentary rocks interpretation of the stratigraphy and eruptive history of the formation has been aided by the recognition of some distinctive lithological units including 1 a 200 600 m thick sequence of weakly parallel bedded basaltic tuffs resting on the pre volcanic basement 2 a 200 600 m sequence of single flow unit aa basalts 3 dacite flows and ignimbrites up to 1100 m thick in the middle and upper parts of the formation and 4 aphyric to pyroxene phyric simple and compound flows of basalt 50 400 m thick locally present in the uppermost parts analysis of the facies comprising the birker fell formation indicates that it was emplaced as a sub aerial plateau andesite sequence formed by the coalescence of products erupted from a number of centres or fissures in an extensional subsiding volcano tectonic rift zone volcano tectonic faulting and eruption of thick ignimbrites locally influenced development of this field

discovery of abundant arthropod trackways in the lower devonian muth quartzite spiti india implications for the depositional environment abstract arthropod trace fossils are described from the lower devonian muth quartzite spiti india a sequence virtually devoid of faunal evidence trace fossils which are abundant and often well preserved mainly consist of arthropod trackways some burrows are present too the ichnogenera of the trackways include numerous palmichnium and rarer diplichnites the first can probably be assigned to eurypterids and the second is probably related to myriapods sedimentological observations point to deposition of the muth quartzite in a foreshore backshore environment this combination of eurypterid and myriapod trackways is a spectacular indication of early terrestrialization

the link between oxygen isotope resetting partial melting and fluid flow in metamorphic terrains a correlation between the style of partial melting and synmeta morphic fluid flow exists in metapelites from the mount lofty ranges reynolds range and omeo zone australia mount lofty ranges migmatites comprise granitic leucosomes in rocks that are still biotite rich with no indications of other mafic minerals being formed along with the melts by contrast in the reynolds and omeo migmatites garnet cordierite and or spinel formed along with the melts oxygen isotope data are most consistent with the mount lofty ranges undergoing significant fluid rock interaction during regional metamorphism which may have fluxed fluid present partial melting by contrast regional metamorphic fluid flow in the reynolds range and omeo zone was limited leading to partial melting via fluid absent reactions the style of melting reactions may help to constrain the timing of isotopic resetting and fluid flow in metamorphic terrains which is currently a contentious issue

stable isotope evidence for regional scale fluid migration in a barrovian metamorphic terrane vermont usa we measured the c and o isotopic composition of carbonate minerals in the waits river formation eastern vermont to determine the extent of fluid infiltration during regional metamorphism over an approx 2000 km2 area in a deep seated 25 km barrovian terrane from a petrologic study of this terrane ferry proposed the existence of a large regional metamorphic hydrothermal system with two first order features 1 on the scale of the entire terrane fluid flow was focused into the axes of two major antiforms of regional extent 2 on a smaller scale about 100 km2 flow was further focused around synmetamorphic granitic plutons that intruded along the axes of the antiforms we find isotopic evidence for both the regional hydrothermal activity along the antiforms and the more intense fluid flow around synmetamorphic plutons the evidence for hydrothermal activity around the plutons is large heavy isotope depletions up to 6 9 in 18ocarb and 13ccarb in diopside zone rocks adjacent to the plutons these isotopic shifts are greater than can be explained solely by prograde metamorphic reactions we find two lines of evidence for the more diffuse regional flow that was focused into axes of the antiforms first 18ocarb and 13ccarb within individual outcrops become increasingly homogeneous with increasing grade towards antiform axes indicating that the rocks equilibrated with a permeating fluid second there are depletions in 18o near the margins of the waits river formation which can be interpreted as a dispersed advective infiltration front displaced toward the antiform axes these fronts were modelled using eq 13 of bickle and baker and imply time integrated fluid of 105 106 cm3 cm2 which are consistent with values derived by ferry from measured progress of prograde devolatilization reactions

national scale evaluation of groundwater chemistry in korea coastal aquifers evidences of seawater intrusion pollution of groundwater by seawater intrusion poses a threat to sustainable agriculture in the coastal areas of korea therefore seawater intrusion monitoring stations were installed in eastern western and southern coastal areas and have been operated since 1998 in this study groundwater chemistry data obtained from the seawater intrusion monitoring stations during the period from 2007 to 2009 were analyzed and evaluated groundwater was classified into fresh 3 000 s cm according to ec levels among groundwater samples n 233 56 7 and 37 were classified as the fresh brackish and saline respectively the major dissolved components of the brackish and saline groundwaters were enriched compared with those of the fresh groundwater the enrichment of na and cl was especially noticeable due to seawater intrusion thus the brackish and saline groundwaters were classified as ca cl and na cl types while the fresh groundwater was classified as na hco3 and ca hco3 types the groundwater included in the na cl types indicated the effects of seawater mixing ca2 mg2 na k so4 2 and br showed good correlations with cl of over r 0 624 of these components the strong correlations of mg2 so4 2 and br with cl r 0 823 indicated a distinct mixing between fresh groundwater and seawater the ca cl and hco3 cl ratios of the groundwaters gradually decreased and approached those of seawater the mg cl na cl k cl so4 cl and br cl ratios of the groundwaters gradually decreased and were similar to or lower than those of seawater indicating that mg2 na k so4 2 and br as well as cl in the saline groundwater can be enriched by seawater mixing while ca2 and hco3 are mainly released by weathering processes the influence of seawater intrusion was evaluated using threshold values of cl and br which were estimated as 80 5 and 0 54 mg l respectively according to these criteria 41 50 of the groundwaters were affected by seawater mixing

the sedimentary record of carboniferous rivers continuing influence of land plant evolution on alluvial processes and palaeozoic ecosystems abstract evidence from modern rivers and the deep time geological record attests to the fundamental importance of plant life for the construction of physical habitats within fluvial environments data from an extensive literature review and original fieldwork demonstrates that many landforms and geomorphic features of modern river systems appear in the palaeozoic stratigraphic record once terrestrial vegetation had adopted certain evolutionary advances for example stable point bars are associated with the onset of rooted plants in the siluro devonian and avulsive and anabranching fluvial systems become common at the same time as extensive arborescent vegetation in the carboniferous in this paper we demonstrate a correlation between the diversification of physical fluvial environments and the expansion of terrestrial fauna and flora with an emphasis on the culmination of these trends within carboniferous alluvial systems many extrinsic factors have been considered as possible controls on the evolutionary timelines of terrestrialization for organisms however a fundamental prerequisite for achieving terrestrial biodiversity was the variety of physical habitats especially riparian systems available for newly evolved organisms in association with abundant lowland meandering systems the widespread appearance across carboniferous alluvial plains of fixed channel and anabranching reaches created further physical landforms for colonization and would have promoted increasingly complex hyporheic flow regimes furthermore the associated increase in arborescent vegetation and supply of large woody debris to inland and coastal rivers would have created a wealth of microhabitats for continental organisms we argue that the expanding extent and diversity of physical alluvial niches during the palaeozoic is an underappreciated driver of the terrestrialization of early continental life the study of the deep time fossil and stratigraphic record also illustrates that vegetation is a fundamental prerequisite for the creation of biogeomorphic alluvial landforms and physical habitats and microhabitats

salinization properties of a shallow groundwater in a coastal reclaimed area yeonggwang korea the need for more agricultural or residential land has encouraged reclamation at the coastal areas of korea since 1200 ad approximately the groundwaters of these reclaimed areas could be expected to reveal hydrogeochemical properties different from those of areas directly affected by seawater intrusion the purpose of this study therefore was to examine the salinization of shallow groundwater in a coastal reclaimed area and to identify the effect of land reclamation on groundwater quality major cations and anions iodide total organic carbon d 18o and 13c were measured to assist the hydrogeochemical analysis chloride d and 18o data clearly show that the na cl type water results from mixing of groundwater with seawater in particular the d and 18o of ca mg cl no3 type groundwaters are close to the meteoric water line but na cl type waters enriched in chloride are 18o enriched with respect to the meteoric water line meanwhile carbon isotopic data and i cl ratios strongly suggest that there are various sources of salinity the 13c values of na cl type groundwaters are generally similar to those of ca mg cl no3 type waters which are depleted in 13c with respect to seawater i cl ratios of na cl type groundwater are 10 100 times higher than that of seawater because the reclamation has incorporated a large amount of organic matter it provides optimum conditions for the occurrence of redox processes in the groundwater system therefore the salinization of groundwater in the study area seems to be controlled not only by saltwater intrusion but also by other effects such as those caused by residual salts and organic matter in the reclaimed sediments

non marine arthropod traces from the subaerial ordovician borrowdale volcanic group english lake district arthropod trace fossils are described from the borrowdale volcanic group a sequence otherwise devoid of faunal evidence two forms both made by the same probably myriapod like organism are assigned to the ichnogenera diplichnites and diplopodichnus the lithologies preserving the trace fossils are non marine and may have been deposited in a freshwater lacustrine environment some of the traces were probably made in temporarily emergent conditions the change from one form of trace to the other reflects drying out of the substrate the trace fossils probably record some of the earliest freshwater arthropods before the widespread colonization of land by the group

origin of salinity in a multilayered aquifer with high salinization vulnerability the kaluvelly watershed is a coastal area tamil nadu india where water abstraction has resulted in a dramatic fall in the level of the water table and a piezometric depression in the most exploited aquifer the vanur aquifer in addition intensification mechanization of agriculture may have affected the quality of recharge water an initial hydrodynamic study showed that the vanur aquifer is highly vulnerable to salinization due to potential seawater intrusion and our aim was to determine the source of salinity recorded in the groundwater of this multilayered aquifer our approach involved the use of existing boreholes and of a moderate number of samples with the aim of developing appropriate water resource management techniques major elements 18o 16o 2h 1h and 87sr 86sr ratios were measured in rainwater surface water and groundwater collected during five sampling campaigns over a two year period geochemical data indicate that the vanur aquifer is recharged and that small mixings between aquifers fluctuate according to monsoon intensity there was no evidence of seawater intrusion the range of recorded salinity originated mainly from water rock interaction but a disconnection of some deeper parts of the aquifer was apparent strontium isotopic ratios in the recharge area suggest an anthropogenic influence possibly related to fertilizer use a high so4 cl ratio was observed in the aquifer in the deeper parts the influence of a formation containing lignite is hypothesized whereas near the surface sulphate may partly originate from fertilizer use and fossil fuel combustion water isotopic data suggest that the origin of precipitation in this region has been unchanged for several hundreds or thousands of years

identification of a holocene aquifer lagoon system using hydrogeochemical data abstract the hydrogeochemical characteristics of the cabo de gata coastal aquifer southeastern spain were studied in an attempt to explain the anomalous salinity of its groundwater this detritic aquifer is characterised by the presence of waters with highly contrasting salinities in some cases the salinity exceeds that of seawater multivariate analysis of water samples indicates two groups of water g1 and g2 group g1 is represented in the upper part of the aquifer where the proportion of seawater varies between 10 and 60 whilst g2 waters taken from the lower part of the aquifer contain 60 70 seawater in addition hydrogeochemical modelling was applied which reveals that the waters have been subject to evaporation between 25 and 35 there was a good agreement between the modelled results and the observed water chemistry this evaporation would have occurred during the holocene in a coastal lagoon environment the resulting brines would have infiltrated into the aquifer and due to their greater density sunk towards the impermeable base the characteristics of this water enabled us to reconstruct the interactions that must have occurred between the coastal aquifer and the lagoon and to identify the environmental conditions that prevailed in the study area during the middle holocene

a subaerial arthropod trackway from the upper silurian clam bank formation of newfoundland trackways are reported for the first time from silurian rocks in newfoundland they occur in the clam bank formation of the port au port peninsula at least one of the trackways represents one of the earliest known occurrences of a large subaerial arthropod trace fossil it is preserved in hyporelief in a red fine grained sandstone the trackway diplichnites dawson 1873 consists of two parallel series of clearly defined imprints it is attributed to a myriapod similar to the lower devonian eoarthropleura the sandstone contains halite pseudomorphs that indicate that the sediment horizon had been subject to desiccation immediately prior to the formation of the trackway the arthropod walked on a red siltstone deposited in an alluvial flats environment analysis of the trackway suggests that the arthropod was approximately 23 cm long and had 17 pairs of walking appendages it appears that a high geared gait with a ratio of forestroke backstroke of 8 2 was used in walking across the substrate that is ap

caradoc brachiopods from the leinster terrane se ireland a lost piece of the lapetus puzzle the recent re collection and examination of brachiopod dominated faunas from many localities in the duncannon group of the leinster terrane of se ireland has resulted in an improved age definition of the assemblages and a reassessment of their biogeographical affinities the assemblages are almost all soudleyan to longvillian caradoc in age and provide some constraint on the duration of volcanism related to subduction which may have ceased in the mid caradoc at this time they were part of a single anglo welsh province which occupied the seas around the eastern avalonia plate the province was composed of well established species from earlier baltic immigrations together with endemics connections with the scoto appalachian and mediterranean provinces are evident also

source of groundwater salinity in coastline aquifers based on environmental isotopes portugal natural vs human interference a review and reinterpretation environmental stable 18o 2h 13c and radioactive 3h and 14c isotopes together with geochemical data were used to identify the origin of salinization in different environments three case studies from sedimentary basins of continental portugal are presented i two at the meso cenozoic portuguese southern border algarve basin and ii one at the lower tagus lower sado basin central portugal with a new data interpretation groundwater salinization occurs in all three cases and may reach values of several grams of total dissolved solids per liter above accepted limits for drinking water the source of this high mineralization could be a seawater intrusion ancient or modern b dissolution from diapiric structures intruding on the aquifer systems c brine dissolution at depth and d evaporation of irrigation water the results obtained have provided an effective label for seawater and freshwater to enable seawater intrusion to be traced as well as the identification of other processes that might be responsible for groundwater salinization such as salt minerals dissolution and ion exchange

degradation of groundwater quality in coastal aquifer of sabratah area nw libya overextraction of groundwater is widely occurring along the coast where good quality groundwater is at risk due to urbanization tourist development and intensive agriculture the sabratah area at the northern central part of jifarah plain northwest libya is a typical area where the contamination of the aquifer in the form of saltwater intrusion gypsum anhydrite dissolution and high nitrate concentrations is very developed fifty groundwater samples were collected from the study area and analysed for certain parameters that indicate salinization and pollution of the aquifer the results demonstrate high values of the parameters electrical conductivity sodium potassium magnesium chloride and sulphate which can be attributed to seawater intrusion the intensive extraction of groundwater from the aquifer reduces freshwater outflow to the sea creates drawdown cones and lowering of the water table to as much as 30 m below mean sea level irrigation with nitrogen fertilizers and domestic sewage and movement of contaminants in areas of high hydraulic gradients within the drawdown cones probably are responsible for the high nitrate concentration towards the south of the region seawater intrusion and deep salt water upconing result in general high so4 2 concentrations in groundwater near the shoreline where localized so4 2 anomalies are also due to the dissolution of sebkha deposits for few wells in the nearby sebkhas upstream the increase in so4 2 concentrations in the south is ascribed to the dissolution of gypsum at depth in the upper aquifer

stable isotopic evidence for large scale seawater infiltration in a regional metamorphic terrane the trois seigneurs massif pyrenees france oxygen isotopic analyses of 95 metamorphic and igneous rocks and minerals from a hercynian metamorphic sequence in the trois seigneurs massif pyrenees france indicate that all lithologies at higher metamorphic grades than the andalusite in isograd have relatively homogeneous 18o values the extent of homogenization is shown by the similarity of 18o values in metacarbonates metapelites and granitic rocks 11 to 13 and by the narrow range of oxygen isotopic composition shown by quartz from these lithologies these values contrast with the 18o values of metapelites of lower metamorphic grade 18o about 15 homogenization was caused by a pervasive influx of hydrous fluid mass balance calculations imply that the fluid influx was so large that its source was probably high level groundwaters or connate formation water hydrogen isotopic analyses of muscovite from various lithologies are uniform and exceptionally heavy at d 25 to 30 suggesting a seawater origin many lines of petrological evidence from the area independently suggest that metamorphism and anatexis of pelitic metasediment occurred at depths of 6 12 km in the presence of this water rich fluid the composition of which was externally buffered deep penetration of surface waters in such environments has been hitherto unrecognized and may be a key factor in promoting major anatexis of the continental crust at shallow depth three types of granitoid are exposed in the area the leucogranites and the biotite granite quartz diorite are both mainly derived from fusion of local paleozoic pelitic metasediment because all these rocks have similar whole rock 18o values 11 to 13 the post metamorphic biotite granodiorite has a distinctly different 18o 9 5 to 10 0 and was probably derived from a deeper level in the crust rare mafic xenoliths within the deeper parts of the biotite granite quartz diorite also have different 18o 8 0 to 8 5 and possibly represent input of mantle derived magma which may have provided a heat source for the metamorphism