application of the parasequence concept to the paleoproterozoic record of the northern fennoscandian shield abstract paleoproterozoic ca 2450 to 2000 ma sedimentary sequences covering archean blocks of the fennoscandian shield outcrop as discontinuous belts in northwest russia eastern and northern finland northern sweden and northern norway this fragmentary distribution hampers conventional correlations more robust inter basin correlations can be established by applying principles of sequence stratigraphy to particularly well preserved sections such as the kovasinvaara formation kainuu belt and the rukatunturi quartzite formation kuusamo belt exposed in northern finland in the east puolanka group kainuu belt depositional systems fluvial high wave energy shoreline tidally influenced shoreline inner shelf define four transgressive systems tracts followed by highstand periods rocks in the kuusamo belt ca 130 km to the north display a similar stratigraphic evolution extensive tidal deposits in these areas record periods of high sea level the sets of identified parasequences in both areas are retrogradational and indicates migration of shoreline landwards enable the deeper water tidal channel fill deposits to occur at the top of an overall transgressive system tracts parasequences identified in this study are related to high frequency cycles of relative sea level change major sequences reflect lower order fluctuations related to heterogeneous lithospheric subsidence as the eustatic origins for individual boundaries become more firmly established it may be possible to proceed to more detailed correlations between coeval sequences deposited on other early precambrian cratons

travertine precipitation in the paleoproterozoic kuetsjarvi sedimentary formation pechenga greenstone belt ne fennoscandian shield abstract precambrian travertines tufas and speleothems either formed rarely or they have not been identified in previous studies in the absence of high pco2 soils in paleoproterozoic karst solution and speleothem formation occurred by processes distinct from those commonly found in present day low temperature karst environments however the high pco2 atmosphere could itself have encouraged karst formation the paleoproterozoic kuetsjarvi sedimentary formation of the pechenga greenstone belt nw russia includes abundant terrestrial carbonate precipitates these precipitates were sampled from a drillcore representing a complete section of the ca 120 m thick formation and were investigated for c and o isotopes acid soluble elemental contents and petrography the newly obtained results were used to constrain the origins of the precipitates and to illuminate different terrestrial carbonate types the investigated drillcore includes abundant small scale cavities and veins which are commonly filled with dolomite and quartz dolomite crusts are found both in the cavities and on bedding erosional surfaces dolomite cements coat uneven surfaces and surficial rock fragments the surficial dolomite crusts form distinct and discrete layers whereas the cements do not the cavity and vein fills are likely post depositional in origin whereas the surficial dolomite crusts and dolomite cements are likely syn depositional precipitates the investigated precipitates often show 13c values lower than those reported from their host rocks suggesting the influence of an external carbon source petrographic features and geochemical data suggest dissolution and precipitation of carbonate material originating from deep sourced co2 bearing fluids likely at high earth surface temperatures

transience of seawater intrusion in response to sea level rise 1 understanding seawater intrusion swi induced by sea level rise slr is important for the future management of many coastal aquifers only simplified steady state sharp interface analyses of generalized slr swi exist in the literature and the important issue of associated time scales has been neglected we employ numerical modeling in order to explore the transience of dispersive slr swi in common unconfined coastal aquifer settings an instantaneous slr is adopted to compare with the instantaneous sea level drop sld case of a previous sld swi analysis temporal asymmetry between the swi responses to slr and sld is observed a slr swi simulation series indicates that toe representative response times time to reach 95 of new steady state range from decades to centuries for a 1 m slr significant discrepancies between the representative response times of various swi quantitative indicators e g toe position wedge center of mass are observed this demonstrates that the indication of steady state swi conditions depends upon the monitoring approach and thus holds implications for studies reporting that swi steady state has been attained we adopt 100 years as a typical planning time frame and compare 100 year and steady state slr swi as expected the simplified steady state sharp interface solution overpredicts the 100 year landward toe shift in most cases however some simulations exhibit temporary overshoot of the steady state interface position this is in contradiction to the presumption that steady state swi is the worst case steady state sharp interface estimates appear to be at best useful as initial approximations of slr swi given that they span 40 250 of 100 year dispersive interface results for the cases considered

transient investigation of saltwater upconing in laboratory scale coastal aquifer abstract the objective of this research was to examine the response of seawater intrusion and retreat to freshwater abstraction from a well in laboratory scale coastal aquifer under transient conditions this has been done experimentally and numerically through qualitative and quantitative analysis the laboratory experiments were completed in a two dimensional laboratory tank for two beads sizes namely 1090 m and 780 m the seawat code was used for the numerical simulations the experimental results showed that the vulnerability of the pumping well to salinization was higher for the low permeability aquifer whereby the saltwater upconing process was observed at an abstraction rate 40 smaller in the lower permeability aquifer compared to the high permeability aquifer in the lower permeability scenario the inland penetration of the saline plume was up to 41 larger than in the higher permeability scenario for an equivalent pumping rate increment in addition the process of decay after the abstraction had ceased of the wedge was slower in the lower permeability aquifer which suggests a slower retreat of the wedge the qualitative comparison of the shape of the saline plume and the quantitative comparison of the transient toe length data between experimental and numerical results showed excellent agreement the flow velocity field analysis revealed that the local reduction of the magnitude of the flow velocity along the upper part of the interface was a major factor contributing to the saltwater upconing mechanism

dating the termination of the palaeoproterozoic lomagundi jatuli carbon isotopic event in the north transfennoscandian greenstone belt abstract existing radio isotopic age constraints indicate that the global palaeoproterozoic lomagundi jatuli large positive carbonate carbon isotopic excursion with 13 c values 5 occurred between 2 2 and 2 06 ga in the north transfennoscandian greenstone belt of the kola peninsula nw russia northern norway and finland the lomagundi jatuli event is recorded in the carbonate rocks of the umba and kuetsjarvi sedimentary formations in the imandra varzuga and pechenga greenstone belts in both areas thick mafic volcanic units umba and kuetsjarvi volcanic formations overlie the carbon isotopic excursion bearing sedimentary units overlying and younger sedimentary units contain carbonate rocks with 13 c values typically ranging between c 1 and 3 signalling the termination of the lomagundi jatuli excursion two new u pb id tims isotope dilution thermal ionisation mass spectrometry zircon dates constrain this termination in both successions the lower unit of the il mozero sedimentary formation is a cross and parallel bedded volcaniclastic greywacke derived largely from erosion of the underlying umba volcanic formation it has yielded detrital zircons with 207 pb 206 pb dates as young as 2055 5 2 3 ma which is a maximum age for deposition and is inferred to date part of the underlying umba volcanics in pechenga the kolosjoki sedimentary formation was intersected by a drill hole obtained by the icdp international continental scientific drilling program supported far deep fennoscandian arctic russia drilling early earth project drilling programme zircons from a mafic fine tuff in this drill core have yielded a 207 pb 206 pb age of 2056 6 0 8 ma this age is interpreted as an eruption age contemporaneous with sedimentation the new age determinations overlap each other within uncertainty and is within error of previously published detrital zircon ages of 2058 2 ma from the kolosjoki sedimentary formation and 2049 28 ma from the kuetsjarvi volcanic formation combined these indicate that the lomagundi jatuli excursion terminated across fennoscandia by 2056 6 0 8 ma and may correlate with similar termination ages in fennoscandia and the transvaal south africa

variable density flow and solute transport simulation of regional aquifers containing a narrow freshwater saltwater transition zone variable density flow and solute transport simulation of aquifer systems containing narrow transition zones between freshwater and saltwater requires particular attention to certain aspects of the numerical method and its application to be successful typically only cases involving wide transition zones have been simulated with variable density transport models possibly because of inaccuracies in the modeling approaches used the major components of a successful approach are threefold first functionally consistent approximation of terms involved in fluid velocity calculations is necessary in the case of galerkin finite element methodology a significant modification is required to the standard approach in order to achieve consistency second the simulator must be verified in a particular series of tests the usual tests using henry s problem for verification of density dependent transport simulators are inadequate to check for consistency of the velocity approximations and for the accuracy of simulating flow driven by bouyancy forces third adequately fine spatial discretization is required when applying the simulator for spatial stability of the numerical transport solution and to allow accurate representation of narrow transition zones and the effects of low transverse dispersivity the effectiveness of this approach is demonstrated through simulation of the flow of fresh and saline groundwater in the layered basalt aquifer of southern oahu hawaii the transition zone in this regional flow system is narrow except near the discharge area where it is broadly dispersed simulation of this common situation with an inconsistent approximation gives grossly incorrect results while simulation with a consistent model provides a robust tool for analysis of system hydrology

numerical modelling of saltwater up coning comparison with experimental laboratory observations summary in this study previous interpretations of the density dependent flow and transport processes induced by pumping freshwater above denser saltwater in four laboratory sand tank experiments are extended using numerical modelling the numerical model captured the transition in dispersiveness of up coning plumes observed in the laboratory i e highly dispersive at early times tending to sharp interfaces after saltwater reaches the well this demonstrates the applicability of the velocity dependent dispersion of the modelling code in all four experiments head dependent flux boundary conditions were used to simulate the sand tank side boundary conditions the experimentally derived boundary conductance values indicate non linear variations in the resistance to flow through side inflow ports between the different experiments nonetheless linear boundary head inflow relationships adequately reproduced laboratory up coning the numerical model was able to reproduce the laboratory results within a reasonable level of accuracy and with minimal calibration of model parameters for three of the four experiments this serves to validate those particular laboratory observations the double peak up coning observed late in the fourth laboratory experiment was not reproduced by the model further analysis considering adsorption of the rhodamine tracer is suggested to explore the cause of this effect numerical modelling results were compared to an existing sharp interface analytical solution which corresponded well with the numerical modelling results for early stages of the four up coning experiments despite the dominant influence of dispersion at early times

early proterozoic regolith at pasvik ne norway palaeoenvironmental implications for the baltic shield regolith occurs at a number of localities along the northern margin of the early proterozoic pechenga greenstone belt marking a profound stratigraphic unconformity at the base of the 10 km thick petsamo supergroup the age of regolith formation can be bracketed between 2 453 42 ga sm nd and 2 330 36 ga rb sr regolith is developed on a varied substrate of archaean rocks including early proterozoic layered gabbros 2 45 ga the best example of the regolith occurs in the pasvik valley at brattli norway analogues are widespread on the baltic shield at the base of early proterozoic greenstone belts showing a low degree of chemical weathering and carbonatisation fluviatile deposits overlying the brattli regolith preserve unweathered pyrite magnetite boulders and terrigenous pyrite grains these features are considered to relate an arid or semi arid palaeoenvironment possibly with some deficiency of oxygen in the atmosphere hydrosphere system a systematic and well preserved regolith or palaeosaprolite at the base of the petsamo supergroup is proof that the northern boundary of the pechenga greenstone belt is a fundamental first order unconformity this places constraints on geotectonic modelling of this early proterozoic rift basin

pumping management of coastal aquifers using analytical models of saltwater intrusion 1 analytical models of saltwater intrusion in coastal aquifers of finite size are developed and utilized in an optimization methodology for determining the optimal pumping rates the models are based on the sharp interface approximation and the ghyben herzberg relation the governing equations are expressed in terms of a single potential and are solved analytically using the method of images to account for the aquifer boundaries the analytical models consider ambient flow and surface recharge the results are compared to numerical simulations indicating a good match as the number of images is increased the objective of optimization is to maximize the total pumping from the aquifer and a set of constraints protect the wells from saltwater intrusion the constraints are expressed using the analytical saltwater intrusion models two different constraint formulations are investigated the toe constraint formulation protects the wells from saltwater intrusion by not allowing the toe of the interface to reach the wells this formulation results in a nonlinear optimization problem which is solved using sequential quadratic programming sqp the potential constraint formulation on the other hand protects the wells by maintaining a potential at the wells larger than the toe potential this formulation results in a linear optimization problem which is solved using the simplex method several simulation runs indicate that the optimal solution is very sensitive to variations of recharge rates hydraulic conductivity heterogeneities etc the linear programming formulation besides being computationally simpler provides a safer solution than the nonlinear formulation

spinifex biogeochemical expressions of buried gold mineralisation the great mineral exploration penetrator of transported regolith a major challenge for mineral explorers is to efficiently detect mineralisation beneath the weathered cover that extends across the landscape determination of the elemental composition of plants biogeochemical exploration can aid in the detection of buried ore deposits due to their root penetration through the weathered cover at the coyote prospect in western australia a range of plant species were sampled traversing a buried au orebody here it is shown that the soft spinifex triodia pungens accumulated important pathfinder elements related to the mineralisation which produced a multi element surficial expression of the underlying ore deposit spinifex grasses are one of the most widespread grasses over the australian continent and have vertical root systems that can extend for many 10s of metres through sedimentary cover and interact with buried mineral deposits and alteration zones in the underlying substrate spinifex biogeochemistry therefore has potential to be a low cost low environmental impact sampling medium for mineral exploration programs across large parts of arid australia the examination of similar grasses from other semi arid and arid regions from around the world therefore also warrants further investigation

petrology and geochemistry of xenoliths from the northern baltic shield evidence for partial melting and metasomatism in the lower crust beneath an archaean terrane lower crustal xenoliths entrained in a paleozoic ultramafic lamprophyre breccia pipe on elovy island kola peninsula russia represent some of the oldest lower crustal material yet investigated from europe the xenoliths vary from feldspar poor garnetrich rocks which resemble eclogites to feldspar rich garnet granulites quartz rich felsic granulites as well as pyroxenites and amphibole rich rocks are also present the mafic granulites eclogites represent a suite of gabbros and norites that is related by olivine fractionation the igneous protoliths may have formed in a manner analogous to lower crustal rocks from most other european xenolith localities i e by basaltic underplating but magmatic cumulates are not in evidence the kola lower crust was subjected to one or more metasomatic events which introduced up to 45 phlogopite and or amphibole into both eclogites granulites and pyroxenites the resulting rocks have strong enrichments in rb ba and k indicating that the lower crust is not uniformly depleted in lil and heat producing elements siliceous 65 sio2 and mafic 50 sio2 lithologies coexist in migmatitic xenoliths which provide evidence for partial melting processes and restite formation in mafic metaigneous lower crust the relationship if any between partial melting and metasomatism is unclear

the thermal and geodynamic evolution of the lapland granulite belt implications for thermal structure of the lower crust during granulite facies metamorphism the tectono thermal history of the lapland granulite belt is considered within the framework of a combined superplume plate tectonic model on the basis of new geochronological and petrological data the high grade metamorphic events were linked with plume related extensional episodes at 2 44 ga m0 2 0 1 95 ga m1 1 95 1 92 ga m2 and 1 92 1 91 ga m3 the last m4 high grade event at 1 89 1 87 ga corresponds to the final collision p t parameters of metamorphism during m1 event ranged from 960 to 860 c and from 14 0 to 10 3 kbar they decreased from the lower to the upper part of the belt during the m2 event from 860 c at 12 4 kbar and to 800 c at 5 8 kbar during the m3 event from 770 c at 10 7 kbar to 640 c at 4 8 kbar and during the m4 event from 650 c at 8 4 kbar to 550 c at 4 5 kbar upward displacement of a hot tectonic slice during the m4 stage caused inverted metamorphic zoning in the autochthonous rocks and a clockwise p t evolution within the melange zone at the base of lgb 1 the internal thermal gradient within the lower crust during events m2 and m3 was 1 8 2 3 c km and during the m4 event it fell to 4 5 c km the agreement of thickness estimates of the granulite ensemble obtained from seismic and petrological data attests to the lithostatic natur eo f

groundwater flow regime within the gambier embayment of the otway basin australia evidence from hydraulics and hydrochemistry a conceptual groundwater flow model for the cainozoic sequence of the gambier embayment of the otway basin south australia is developed using hydraulic head distribution environmental isotopes and hydrochemical data local flow cells occur within the upper sequence of the gambier unconfined aquifer and are recognised by local relief of the water table and as rapid lateral variations in chloride 14c 2h and 18o concentrations indicating that regional flow is not dominant in the upper portion of the unconfined aquifer these localised systems are topographically controlled and have developed in response to undulating stranded coastal dune ridges of the bridgewater formation recharge areas correspond to dune highs while discharge is focused towards the lower lying interdunal regions total dissolved solids concentrations are controlled by evapotranspiration processes during recharge and ion ratios are modified by water rock interactions within the groundwater system groundwaters are more dilute in the southern section of the basin where the surplus of precipitation over evapotranspiration in the winter months is greater than that in the northern section of the basin a regional flow system with interaquifer mixing has developed within the confined dilwyn aquifer system recharge to the dilwyn aquifer has been identified downgradient from the basin margin via downward leakage from an intermediate flow system within the gambier unconfined aquifer to the deeper regional flow system of the confined dilwyn aquifer interaquifer mixing appears to be geologically controlled in the south by the elevated gambier axis and in the north by the kanawinka fault downgradient of the zero head difference line lateral flow appears to be the dominant transport mechanism within the dilwyn aquifer as indicated by constant chloride concentrations monotonic decrease in radiocarbon concentration and more negative 2 and 18 o composition

palaeoproterozoic accretionary processes in fennoscandia abstract accretionary processes contributed to major continental growth in fennoscandia during the palaeoproterozoic mainly from 2 1 to 1 8 ga the composite svecofennian orogen covers c 1 10 6 km 2 and comprises the lapland savo fennia svecobaltic and nordic orogens it is a collage of 2 1 2 0 ga microcontinents and 2 02 1 82 ga island arcs attached to the archaean karelian craton between 1 92 and 1 79 ga andean type vertical magmatic additions especially at c 1 89 and c 1 8 ga were also important in the continental growth the palaeoproterozoic crust is the end product of accretionary growth continental collision and orogenic collapse preserved accretional sections are found in areas where docking of rigid blocks has prevented further shortening the pirkanmaa belt represents a composite accretionary prism and other preserved palaeosubduction zones are identified in the gulf of bothnia and the baltic sea areas in the southern segment of the lapland savo orogen collision between the archaean continent lower plate and the palaeoproterozoic arc microcontinent assembly upper plate produced a special type of lateral crustal growth the archaean continental edge decoupled from its mantle during initial collision and overrode the arc and its mantle during continued collision

a widespread positive 13ccarbanomaly at around 2 33 2 06 ga on the fennoscandian shield a paradox carbon isotope measurements carried out on 201 carbonate samples from the early proterozoic of the kola peninsula n karelia and norway yield 13c pdb spanning 20 5 to 11 a general 13c secular trend shows that prior to 2 33 ga values are typically normal marine averaging around 3 0 between 2 33 and 2 06 ga in jatulian time there follows a rapid excursion to positive 13c of around 6 post jatulian time is characterized by 13c of sedimentary carbonates fluctuating between 5 and 3 also it is remarkable for the first pronounced development of diagenetic carbonates which have 13c between 14 and 6 the c 6 positive 13c shift with a duration of about 270 myr coincides with a maximum in the diversity and abundance of stromatolites and with widespread development of red beds but does not coincide with the maximum of buried corg mass the fennoscandian shield represents the largest isotoically anomalous carbonate province yet reported and the positive 13c excursion together with a series of major global palaeoenviromental changes seems to be more intense than the precambrian cambrian transition events however it is still not clear what kind of mechanism this phenomenon could be attributed to an increase of the ronov ratio and or broecker ratio and other possible models are discussed as the target for future investigations

experimental observations of saltwater up coning summary the proper management of coastal aquifers commonly requires an understanding of the behaviour of saltwater plumes underlying production wells the current understanding of saltwater up coning i e the pumping induced rise in the freshwater saltwater interface is based predominantly on theoretical constructs of salinity and flow responses to groundwater pumping plus a limited number of field scale and laboratory investigations there is a need to produce direct observations of saltwater up coning given the considerable and inherent uncertainties associated with the prediction of density dependent flow and dispersive solute transport behaviour in this study time series observations of saltwater up coning were made using controlled sand tank experiments of a two dimensional aquifer cross section a range of mixed convection ratios was tested by invoking different groundwater abstraction rates and saltwater densities the temporal development of up coning was characterised in terms of the height of the interface apex the width of the salt plume and the salinity of the pumping well experimental results were compared to an existing sharp interface analytical solution and close agreement was obtained for two of the cases higher freshwater saltwater density differences and lower pumping appeared to induce the largest deviations from theoretical up coning dispersive transport processes dominated during phases of near well up coning causing gradual increases in pumped water salinity although plumes became non dispersive after the interface made contact with the bore an interesting departure from the classical up coning shape was obtained for the situation of highest saltwater density and lowest pumping in which up coning occurred as an almost horizontal interface for the majority of the experiment eventually producing a double apex shape as the interface neared the well the experimental results could form a useful basis for the testing of density dependent groundwater flow and transport models since they offer controlled laboratory analogues of saltwater up coning

pechenga ferropicrites and other early proterozoic picrites in the eastern part of the baltic shield ti poor komatiites and ti rich picrites exist among the widely occurring primitive mgo rich volcanics in the early proterozoic successions of the kola peninsula both have been encountered in the imandra varzuga belt but only picrites are found in the pechenga complex the picritic rocks are divided into two types the first type restricted to the kolasjoki and pilgujarvi suites and the tominga series is called ferropicrite due to its exceptionally high total iron content which usually exceeds 14 feotot the second type found in the south pechenga series and in the umba and panarechka suites has more typical iron content and geochemically resembles suisaarian picrites from southern karelia ferropicrites occur as pillow lavas lava breccias tuffs massive lavas and up to 50 m thick differentiated spinifex textured flows in addition to high feotot contents these rocks are characterized by low al2o3 contents and by high concentrations of tio2 zr and other incompatible elements they are strongly lree enriched and have immobile trace element characteristics similar to within plate transitional or alkali basalts it is shown that with regard to both the major and trace element compositions the parental magma of the ni bearing intrusions of the pilgujarvi suite is similar to ferropicrite suggesting that the emplacement of the intrusions took place contemporaneously with ferropicritic volcanism the high incompatible element contents of the ferropicritic rocks rule out a genetic relationship with associated tholeiitic basalts proposed geotectonic settings for the pechenga area including an intracratonic rift zone a passive continental margin an oceanic island arc a mature continental volcanic arc and a collisional suture zone are discussed the presence of ti rich picritic rocks does not support a subduction related environment

sedimentary and volcanic facies recording the neoarchaean continent breakup and decline of the positive δc excursion abstract the palaeoproterozoic kalix greenstone belt at the northern end of the bothnian bay in sweden comprises three groups the lower group a ca 3000 m thick unit of subaerially erupted tholeiitic intraplate basalts interbedded with fluviatile conglomerates represents the volcano sedimentary succession deposited in a rift setting these units are truncated by a break up unconformity above which is the middle group an 800 m thick succession of dolograinstones stromatolitic dolostones arenites volcanoclastic and mafic volcanic rocks stromatolite morphologies and the occurrence of distinctive sedimentary structures including planar and herringbone cross bedding hummocky cross stratification symmetrical and asymmetrical ripples desiccation cracks and tepees indicate markedly variable depositional environments associated with transition from a marine influenced rifted margin to a rimmed carbonate shelf sedimentation was accompanied by subaerial mafic volcanism and syndepositional tectonics the upper group a more than 2000 m thick unit of deep water shales was deposited on the drowned carbonate platform of the middle group in response to tectonically enhanced subsidence this study provides a detailed palaeoproterozoic depositional history of the fennoscandian shield from rifting to passive margin development associated with both dispersal of the neoarchaean supercontinent and decline of the proterozoic positive isotopic excursion of 13 c 12 c in sedimentary carbonates in contrast to many previously reported 13 c rich palaeoproterozoic carbonates which were deposited in non marine to restricted or partly restricted settings the carbonate facies reported herein were well connected to the oceanic realm and thereby represent a good opportunity to test restricted marine versus open marine models for how the carbon cycle functioned in deep time

sequence stratigraphy of the siliciclastic east puolanka group the palaeoproterozoic kainuu belt finland abstract the 2300 2600 m thick palaeoproterozoic east puolanka group within the central fennoscandian shield records four major transgressions on the cratonic margin within the approximate time period 2 25 2 10 ga stacking of siliciclastic facies in parasequences and parasequence sets provides data to evaluate oscillation of relative sea level and subsidence on different temporal scales the lowermost part of the passive margin prism is characterized by alluvial plain to shallow marine sediments deposited in incised valleys the succeeding highstand period is recorded by ca 250 m of progradational parasequence sets of predominantly rippled and horizontally laminated sandstones representing stacked wave dominated shoreline units in sequence 1 capped by a hiatus or in some places by a subaerial lava as relative sea level rose again sand rich barrier beach complexes developed with microtidal lagoons and inlets corresponding to a retrogradational parasequence set this was followed by a highstand period with aggradation and progradation of alluvial plain and coastal sediments grading up into wave tide influenced shoreline deposits in sequence 2 in sequence 3 the succeeding mudstones represent tidal flat deposits in a back barrier region with continued transgression the parasequences stacked retrogradationally each flooding episode being recorded by increasingly deeper water deposits above low angle cross bedded sandstones of the swash zones the succeeding highstand progradation is represented by alluvial plain deposits the next transgressive systems tract overlying an inferred erosional ravinement surface is recorded by a retrogradational parasequence set dominated by low angle cross stratified swash zone deposits in sequence 4 the large scale trough cross bed sets in these parasequences represent sand shoals and sheets of the inner shelf system the overall major transgression recorded in the lowermost part of the palaeoproterozoic cratonic margin succession was related to first to second order sea level changes probably due to increasing regional thermal subsidence of the lithosphere following partial continental breakup the stratigraphic evolution can be related to changes of relative sea level with a frequency of ca 25 million years probably propagated by episodic thermal subsidence the parasequences identified here are related to high frequency cycles of relative sea level change due to low magnitude eustatic oscillations

vertical carbon 14 profiles for resolving spatial variability in recharge in arid environments summary groundwater age tracers are often measured to help constrain estimates of groundwater recharge especially in arid environments where other methods are unsuitable however multiple processes can influence the shape of vertical tracer profiles in an aquifer including 1 variation in tracer input concentrations from the unsaturated zone 2 the role of diffusion in transporting tracer into the aquifer when fluxes are low and 3 spatial variability in recharge this study demonstrates the influence of spatially variable recharge and spatially variable carbon 14 14 c activities in the unsaturated zone on vertical 14 c profiles in groundwater through groundwater flow and solute transport modelling we demonstrate that recharge estimated from single point measurements of 14 c may be wrong more than an order of magnitude when unsaturated zone 14 c activities and recharge vary spatially we then present a case study from the ti tree basin in arid central australia where detailed profiles of 14 c activity in unsaturated zone gas and groundwater have been measured and spatial variability in unsaturated zone 14 c is observed ranging from 54 to 106 pmc above the watertable through modelling our data we show that when unsaturated zone 14 c activities are known measurement of the 14 c profile can help constrain estimates of recharge and its spatial variability this approach improves our understanding of groundwater flow in the ti tree basin by showing mountain front recharge to be an important mechanism

groundwater recharge dams in arid areas as tools for aquifer replenishment and mitigating seawater intrusion example of alkhod oman groundwater depletion and seawater intrusion constitute major challenges along coastal aquifers in arid areas this paper assesses the role of groundwater recharge dams constructed to replenish aquifers and fight seawater intrusion with reference to alkhod dam oman sited 7 km from the coast on a gravely unconfined aquifer water table rise in piezometers located downstream from the dam shows regular patterns correlating with magnitude of wadi flow whereas upstream piezometers show irregular patterns controlled release of water captured by the dam optimizes water percolation and enhances artificial recharge which was estimated in the wet years 1997 2003 and 2005 as 15 22 and 27 mm3 respectively using water table fluctuation method recharge contributed 40 60 of the total annual abstraction groundwater salinity increased in the 1980s and 1990s and the saline freshwater interface advanced inland but has receded partially after 1997 highest rainfall and completely after 2005 indicated by reduction in electrical conductivity and thickening of freshwater lens the recession is attributed to the dam s induced recharge and reduction of pumping in 2004 following the commissioning of barka desalination plant integrating artificial recharge with groundwater resources management is therefore an effective measure to replenish aquifers in arid areas and mitigate seawater intrusion along the coasts

vertical leakage in sharp interface seawater intrusion models of layered coastal aquifers summary previous sharp interface studies of seawater intrusion swi adopt various approaches to the treatment of vertical fluxes in regions where alternating saltwater and freshwater are found in overlying aquifers in this study we compare dispersive modeling and sand tank experiments to the results of sharp interface models to evaluate assumptions regarding vertical fluxes in coastal multi aquifer systems the sand tank experiments one transient and two steady state cases consist of two coarse sand layers separated by a lower permeability layer of fine sand vertical freshwater leakage in sharp interface models is treated in one of three ways case 1 upward freshwater leakage flows only into freshwater in the aquifer above bypassing any overlying saltwater case 2 no upward freshwater leakage occurs if there is overlying saltwater case 3 freshwater leaks into any overlying saltwater without modifying the saltwater salinity sharp interface models over predicted the toe position of the saltwater wedge in both the experiments and numerical models regardless of the vertical leakage assumption in agreement with previous studies nonetheless case 1 produced improved prediction of the sand tank results relative to cases 2 and 3 freshwater leakage fluxes in areas where the interface was absent were reasonably well represented by all three sharp interface leakage assumptions compared to those of the dispersive model in regions where saltwater overlies freshwater the upward freshwater fluxes predicted by dispersive modeling were found to be consistently closest to the upward freshwater flux of case 1 compared to cases 2 and 3 saltwater to saltwater leakages from the dispersive models were poorly represented by the sharp interface models vertical flux assumptions were then evaluated for idealized field scale situations and case 1 again best matched the dispersive modeling results streamlines from dispersive modeling show that upward freshwater leakage tends to flow around and bypass overlying saltwater this matches optimally the assumption of case 1 we conclude that case 1 is the ideal approach to the treatment of upward freshwater fluxes in sharp interface models of multiple aquifer systems whereas cases 2 and 3 may create unrealistic swi predictions especially for situations where overlying aquifers are separated by a layer of low conductance

carbon 14 and stable isotope data for an area in the murray basin its use in estimating recharge measurements of the carbon 14 concentration of water in 33 boreholes in a saline unconfined aquifer in southern australia have been interpreted to show that local recharge under natural conditions has a mean annual value which falls between 0 1 and 0 2 mm yr 1 the chloride concentration of groundwater is log normally distributed suggesting that its source is rainfall the estimate of mean annual recharge to the aquifer made using chloride is 0 25 mm yr 1

2000 ma sulphide concretions from the productive formation of the pechenga greenstone belt nw russia genetic history based on morphological and isotopic evidence abstract two hundred and fifty nine sulphide samples from black shales of the productive formation belonging to the palaeoproterozoic 2000 ma petsamo supergroup in the kola region nw russia have been analysed for their sulphur isotope ratio the sulphide bearing black shales were formed in a non euxinic basin within an oceanic rift environment the rocks have undergone greenschist facies metamorphism the black shales are marked by very high s corg ratios and a strong positive correlation between corg and s r 0 70 with zero intercept on the sulphur axis different generations of sulphide concretions have been distinguished by means of concretional analysis individual isotope study of synsedimentary sulphide layers and sulphides from early middle and late diagenetic catagenetic sulphide concretions yields trends which suggest bacterial sulphate reduction as the concretion forming process the overall spread of 34 s from 8 3 to 24 9 indicates 34 s sulphate sulphide between 29 and 4 given a seawater sulphate at around 21 the first order trend is a progressive enrichment in 34 s with increase of burial two major populations of sulphides have been distinguished the first concretions and perhaps thin layers formed in an open system with respect to seawater sulphate and has a limited 34 s range of 2 7 to 3 8 this is coupled with extensive formation of diagenetic carbonate beds marked by 13 c of 8 7 to 12 5 the second population lenses thin layers concretions and microconcretions in carbonate nodules formed in a closed system and is characterized by a high fe2 s2 ratio and progressive development of a rayleigh distillation process which drove 34 s from 8 3 up to 24 9 the high fe2 s2 and possibly change in ph parameter resulted in pyrrhotite rather than in pyrite associated abundant carbonate nodules have 13 c in the range 8 2 to 14 1 overall low 34 s sulphate sulphide and the high s corg ratio are consistent with one stage bacterial sulphate reduction in a non euxinic basin the observed 34 s sulphate sulphide of 29 as maximum is within the pure sulphate reducing bacteria range of 4 46 advanced isotopic modification involving the oxidative part of the sulphur cycle has not been detected based on the data available one can not exclude the presence of a third population of sulphides thin massive layers with 34 s from 2 5 to 0 3 which might have inorganic origin and formed from an exhalative source

reconstructing the shape of large synformal folds based on the solution of the 2d non linear magnetic inverse problem abstract this paper deals with a new approach to reconstructing the shape of a poorly exposed synform that folds strongly magnetic layers the approach is based on the solution of the 2d non linear magnetic inverse problem in areas best suited for 2d modeling the interpretation model consists of two parts i a geometric model imitating a synform cross section and ii a set of elementary layers of a fold characterized by anisotropic magnetic susceptibility the main task is to determine the deepest point of magnetic layers and the direction and amount of their dip it can be solved by a selection of optimal model parameters from a set of random numbers with a priory model constraints the solution is an iterative process which defines intervals of geometrical model parameters that correspond to minimal values of the misfit between observed and modeled magnetic fields the proposed approach is characterized by a stability of the determination of reference fold points coordinates which is sufficient to confidently answer a number of questions important for the geologist these include whether a synformal fold is upright inclined or overturned determining the depth of its trough line which combined with the fold outline on the ground surface allows an evaluation of the hinge line curvature as an example the large paleoproterozoic serpovidny isoclinal synformal anticline in the keivy terrane of the northeastern fennoscandian shield has been chosen according to field observations this synform is a giant sheath fold consisting of the poorly exposed strongly magnetic core and weakly magnetic limbs the 3d morphology of the serpovidny fold reconstructed using the new approach is shown to be very close to the geometry determined from field observations thereby this study favors the conclusion based the sheath geometry of the serpovidny isoclinal synformal anticline that an alpine type tectonics operated in the paleoproterozoic

sequence stratigraphy of the karelian formations 2 4 2 0 ga of the fennoscandian shield significance of major unconformities abstract established sequence stratigraphy for the palaeoproterozoic sedimentary sequences of the karelian formations of the fennoscandian shield illustrate first and second order base level cycles within a synrift to cratonic margin transition the stacking of siliciclastic facies in sequences and parasequence sets in the east puolanka group provide data to evaluate changes of relative sea level and basin subsidence in four third order sequences within a second order cycle in the kainuu belt the sedimentary sequences of the autochthonous part of the belt are up to 4700 m in total thickness the sedimentary sequences show the effects of very long duration first order cyclicity of sea level with a duration of ca 400 ma as part of the progressive development of a rifted neoarchaean continent attenuation of continental crust during rifting and breakup of the continent raised relative sea level from the autochthonous part of the kainuu belt three major basin evolution stages are recognized synrift transitional and initial passive margin each expressed by unconformity bounded second order cyclicity of duration more than 100 ma basal mafic volcanics and alluvial to glacial siliciclastics some 400 700 m thick of the kurkikyla and honkajarvi groups represent synrift deposits of a second order basin fill sequence related to a continental scale fragmentation of the crust ca 2 4 2 3 ga ago many of the shallow intra cratonic basins subsided below sea level some being affected by a major continental glaciation the subsequent peneplanation was dominated by an intensive period of subaerial chemical weathering apparently of the extent of an entire craton and identified as the next major unconformity the following second order sequence of deposits from quartz arenitic alluvial fans and broad braided alluvial plains of the korvuanjoki group up to 1400 m thick was deposited in half grabens still in a relatively stable cratonal setting and corresponding to the incipient stage in the development of a continental margin stacked highstand sequences were then encountered and extensive erosion and deep incised valleys were formed during the falling stage of relative sea level within the next unconformity bounded second order 2300 2600 m thick sequence of a passive margin prism of the east puolanka group ca 2 25 2 10 ga four third order cycles were identified defined by variable system tracts and sequence boundaries formed during a falling stage of relative sea level these sequences record lowstand and transgressive systems tracts followed by pronounced highstand systems tracts the sparse parasequence sets identified in these sequences are related to high frequency cycles of relative sea level change deposition was related to the increasing tectonic flexure and episodic regional subsidence of the cratonic margin followed later by distal shelf mudstones carbonates and deeper water deposition that rimmed much of the continental margin

the great whirl observations of its seasonal development and interannual variability 1 in situ measurements are used together with sea surface height data to study the development and variability of the great whirl gw a large quasi stationary anticyclone that appears off the coast of somalia during the southwest monsoon season we find that anticyclonic circulation indicative of the gw appears on average in april almost two months before the onset of the southwest monsoon winds this early initiation is coincident with the arrival of annual rossby waves at the western boundary with the onset of the monsoon winds in early june the gw proper intensifies quickly remaining at its peak throughout july august and september and dissipating about one month after the winds have died the gw is present for an average 166 30 days per year and the position of its northern flank close to 9 n coincides with the latitude of zero wind stress curl the intraseasonal variability of the gw is intense as a result of mutual advection with one to three flanking cyclones which accompany the gw 70 of the time and tend to circulate clockwise around it there is no consistent seasonal pattern for the development or dissipation of the gw although movement to the southwest is common toward the end of the season the gw of 1995 deepened from 200 m in june to over 1000 m in september and strengthened from a swirl transport of 10 to 60 sv cool waters in its core resulted from advection via the somali current and some local vertical mixing

laboratory scale investigation of saltwater intrusion dynamics 1 experiments were completed in a laboratory scale porous media tank to study the transport patterns of a saltwater wedge in a freshwater aquifer three types of experiments were performed to develop 1 steady state salt wedge data observed under different hydraulic gradient conditions 2 transient salt wedge data observed under intruding wedge conditions and 3 transient salt wedge data observed under receding wedge conditions furthermore flux measurements were made to quantify the flow characteristics of three distinct steady state experiments the saltwater intrusion model seawat was used to simulate these data sets the model results along with the experimental data are presented as benchmark problems for testing density coupled groundwater flow models a worthiness analysis was completed to test the sensitivity of these experimental problems to density coupling effects the results of our analysis show that the proposed benchmark is a more robust alternative to the traditional henry problem these new experimental data sets can be used to assess the performance of saltwater intrusion models under both steady state and transient conditions

management of coastal aquifers based on nonlinear optimization and evolutionary algorithms abstract a method of assessing the optimum pumping rates of coastal aquifers based on nonlinear optimization and evolutionary algorithms ea is developed the objective is to maximize the total pumping rate while protecting the wells from sea water intrusion the formulation of the constraints is based on numerical simulation of the freshwater flow equations the simulation model is based on the sharp interface and the ghyben herzberg approximation and is applicable to unconfined aquifers and steady state flow the single potential formulation of water resour res 12 1976 1165 is followed and the governing equations are solved numerically using finite differences the numerical model can handle aquifers of complex shapes nonuniform hydraulic conductivity nonuniform distribution of surface recharge etc the constraints are nonlinear with respect to the decision variables resulting in a nonlinear optimization problem two optimization methods are investigated specifically sequential quadratic programming sqp and evolutionary algorithms ea sqp requires less computer time than ea but can get stuck on local optimum solutions the simulation and optimization methodology is applied to a real unconfined coastal aquifer in the greek island of kalymnos for determining the optimal pumping rates while protecting the wells from sea water intrusion

the paleoproterozoic 2 5 1 7 ga midcontinent rift system of the northeastern fennoscandian shield versus the early proterozoic pechenga varzuga belt a case of back arc spreading discussion two papers have appeared simultaneously the paleoproterozoic 2 5 1 7 ga midcontinent rift system of the northeastern fennoscandian shield in the canadian journal of earth sciences cjes smolkin 1997 and the early proterozoic pechenga varuga belt a case of back arc spreading in precambrian research sharkov and smolkin 1997 it is of interest that although the two papers were published simultaneously they were submitted and accepted at different times sharkov and smolkin submitted 6 march 1995 accepted 14 august 1996 smolkin submitted 19 april 1996 accepted 28 november 1996 it is difficult to believe that smolkin was either unaware of or had quickly forgotten the sharkov and smolkin article there is however no reference to either article in the other both papers have been devoted to the same topic namely the palaeotectonic significance of the palaeoproterozoic ca 2 5 1 8 ga pechenga imandra varzuga and the granulite belts on the fennoscandian shield it is apparent already from the titles that these articles are in conflict with each other though using essentially the same data this is not totally unknown in science but in this case as the same author that is smolkin is the sole author of the one and the second author of the other it is at best highly unusual in the one paper sharkov and smolkin 1997 the importance of subduction and islandarc construction in the pechenga varzuga belt is emphasized though in the other paper it is ignored smolkin 1997 subduction and island arc construction is an integral part of the geotectonic modelling of this region as shown by mints 1993 mints et al 1996 and indeed our own work melezhik et al 1994a melezhik and sturt 1994 1995 in fact the idea of subduction and collisional tectonics as being important processes in the later stages of development in this belt was already present in the literature during the 1980 s e g berthelsen 1984 marker 1985 berthelsen and marker 1986 there are a number of other disagreements between these two papers one of these is a palaeotectonic interpretation of tholeiitic basalts of the pilgujarvi volcanic formation named matert by smolkin and sharkov these tholeiitic basalts have been considered analogous to normal mid oceanic ridge basalt nmorb since kremenetsky and ovchinnikov 1986 published their first results on rare earth elements see also melezhik and sturt 1994 although they ignore the previous work sharkov and smolkin 1997 have however taken the nmorb signature of these rocks as a key element in arguing for the presence of ca 2 0 ga oceanic crust beneath the pechega belt these tholeiites are also known to have enrichment in fe ti k rb ba e g predovsky et al 1974 hanski 1992 and in some cases light rare earth elements lree melezhik et al 1994a they are also known by their spatial and temporal associations with ferropicrites hanski and smolkin 1989 that are enriched in fe ti first series transition metal incompatible elements and lree hanski and smolkin 1989 these geochemical features have been assigned by smolkin 1997 to contamination of both tholeiitic basalts and ferropicrites by continental crustal material and interpreted as the presence of continental crust beneath the pechenga belt and will be discussed later however before discussing other apparent inconsistencies between these two articles we would like to address a number of questions to dr smolkin and make some comments concerning the article published in the canadian journal of earth sciences smolkin 1997

2 45 ga break up of the archaean continent in northern fennoscandia rifting dynamics and the role of inherited structures within the archaean basement abstract constraints from restoration of minor rift related faults preserved from subsequent palaeoproterozoic overprint along the southern margin of the perapohja belt northern fennoscandia indicate local ne sw extension directions prevailed at the time of 2 44 ga rifting of the archaean continent this palaeostress field is attributed to pull apart setting of the perapohja belt at a left overstepping zone of major sinistral n s trending deformation zones consequently the variably overprinted nw se trending structures of the perapohja belt including the nw se central graben were originally generated as normal faults the proposed setting is compatible with a conducted reconnaissance sandbox analogue model where the orientation of the major normal faults was controlled by the ambient stress field within the step over zone between strike slip faults by contrast the faults bounding e w to ene wsw trending basement horsts are the result of reactivation of older basement structures underlying the pull apart basin based on the results we infer that the final break up of the archaean continent in northern fennoscandia utilized the 2 44 ga rift related nw se trending crustal anisotropy parallel with dyke swarms with pre existing archaean n s trending structures reactivated as second order shear zones in between the voluminous syn rift 2 5 2 4 ga and later pulses of mafic magmatism 2 32 1 98 ga are considered indicative of active type rifting which onset was controlled by a mantle plume centred within a supercraton formed by the superior hearne and karelian kola cratons the presented model supports the continuity of the archaean craton beyond the caledonian orogen towards north west and explains its segmentation suggesting a model for the localization of the palaeoproterozoic supracrustal belts of northern fennoscandia moreover this paper provides an approach to understand the basement cover relationships and the structural signatures within these relatively shallow supracrustal belts which are highly prospective for mineral deposits

petrography and the ree composition of apatite in the paleoproterozoic pilgujarvi sedimentary formation pechenga greenstone belt russia the first globally significant phosphorous rich deposits appear in the paleoproterozoic at around 2 ga however the specific triggers leading to apatite precipitation are debated we examine phosphorous rich rocks up to 8 wt p2o5 in 1 98 1 92 ga old pilgujarvi sedimentary formation pechenga greenstone belt russia phosphates in these rocks occur as locally derived and resedimented sand to gravel pebble sized grains consisting of apatite cemented muddy sediments phosphatic grains can be subdivided into four petrographic types a d each has a distinct ree signature reflecting different early to late diagenetic conditions and or metamorphic overprint pyrite containing petrographic type d which typically has a flat ree pattern negative ce anomaly and positive eu anomaly is the best preserved of the four types and best records conditions present during apatite precipitation type d phosphatic grains precipitated under sub oxic basinal conditions with a significant hydrothermal influence these characteristics are similar to zaonega formation phosphates of nw russia s onega basin and consistent with phosphogenesis triggered by the development of anoxic sulfidic sub oxic redoxclines at shallow sediment depth during the paleoproterozoic

impacts of cave air ventilation and in cave prior calcite precipitation on golgotha cave dripwater chemistry southwest australia abstract speleothem trace element chemistry is an important component of multi proxy records of environmental change but a thorough understanding of hydrochemical processes is essential for its interpretation we present a dripwater chemistry dataset pco2 alkalinity ca sicc mg and sr from an eight year monitoring study from golgotha cave building on a previous study of hydrology and dripwater oxygen isotopes treble et al 2013 golgotha cave is developed in quaternary aeolianite and located in a forested catchment in the mediterranean type climate of southwest western australia all dripwaters from each of the five monitored sites become supersaturated with respect to calcite during most of the year when cave ventilation lowers pco2 in cave air in this winter ventilation mode prior calcite precipitation pcp signals of increased mg ca and sr ca in dripwater are attributed to stalactite deposition a fast dripping site displays less evolved carbonate chemistry implying minimal stalactite growth phenomena which are attributed to minimal degassing because of the short drip interval 30 s we employ hydrochemical mass balance modelling techniques to quantitatively investigate the impact of pcp and co2 degassing on our dripwater initially we reverse modelled dripwater solutions to demonstrate that pcp is dominating the dripwater chemistry at our low flow site and predict that pcp becomes enhanced in underlying stalagmites secondly we forward modelled the ranges of solution mg ca variation that potentially can be caused by degassing and calcite precipitation to serve as a guide to interpreting the resulting stalagmite chemistry we predict that stalagmite trace element data from our high flow sites will reflect trends in original dripwater solutes preserving information on biogeochemical fluxes within our system by contrast stalagmites from our low flow sites will be dominated by pcp effects driven by cave ventilation our poorly karstified system allows us to highlight and quantify these in cave pcp processes which are otherwise masked at sites where karstification is more developed and hydrogeology is more complex our modelling also shows enhanced co2 source production in the unsaturated zone that is attributed to deeply rooted vegetation and increasing bioproductivity which we link to forest recovery after fires impacted our site during 2006 ce

impact of layered heterogeneity on transient saltwater upconing in coastal aquifers abstract this research investigated the effect of layered heterogeneity on transient saltwater upconing in a laboratory scale coastal aquifer the experiments were conducted in a 2d laboratory flow tank and the response of the saltwater wedge to pumping was analysed in a heterogeneous aquifer system where a low permeability layer was constructed in the middle of the aquifer the seawat code was used for validation and to perform additional simulations to explore the sensitivity of the critical pumping rate and the critical time to the main parameters characterising the low permeability layer which included its permeability thickness and position the experimental results showed that the presence of layered heterogeneity noticeably altered the shape and the intrusion length of the upconing wedge without inducing a change in the abstraction rate triggering saltwater upconing mechanism compared to the homogeneous case the numerical results of the layered aquifer provided excellent agreement with the experimental data for both the transient toe length and the shape of the steady state saltwater wedges the sensitivity analysis revealed that the critical pumping rate and the critical time was found to decrease considerably with decreasing hydraulic conductivity and thickness of the middle layer which evidences the higher vulnerability of such layered aquifer systems to the saltwater upconing in comparison to idealised homogeneous systems the results nonetheless showed that varying the position of the interlayer induced very little change on the critical pumping rate but the critical time would tend to decrease as the low permeability layer was moved deeper away from the pumping well particularly for smaller middle layer thickness

subaerial exposure surfaces in a palaeoproterozoic 13c rich dolostone sequence from the pechenga greenstone belt palaeoenvironmental and isotopic implications for the 2330 2060 ma global isotope excursion of 13c 12c abstract this article reports the discovery of numerous subaerial exposure surfaces which occur in the ca 2200 ma kuetsjarvi sedimentary formation ksf from the pechenga greenstone belt ne fennoscandian shield russia the formation was accumulated within an intraplate rift and is composed of fluviatile deltaic siliciclastic deposits and lacustrine dolostones the dolostones are enriched in 13 c 13 c 6 6 to 7 6 v pdb 18 o 16 7 to 21 5 v smow which is in general assigned to a global perturbation of the carbon cycle the lacustrine dolostone unit contains desiccated and in situ brecciated carbonate beds subaerial erosion and dissolution surfaces epikarst surficial silicification silcretes and hot water spring travertines the dissolution surfaces marked by formation of a few centimetre thick vuggy non laminated dolomicrite capped by silicified nodular zone resemble modern calcretes which formed by capillary rise of surface waters per ascensum calcrete following saturation of the regolith zone under arid or semi arid conditions abundant red iron stained superficial dolocrete implies the existence of an o 2 rich atmosphere rezolith black pebbles alveolar septal structures microcodium and other fabrics associated with plant roots and input of terrestrial organic matter which are typical for post cretaceous pedogenic calcretes have not been identified alfa fabrics can be applied to describe dolocretes though rhombic calcite crystals are lacking neither 13 c depletion nor 13 c enrichment has been documented in the dolocrete which suggests no contribution of co 2 derived from soil or from any other c org rich sources enriched in 12 c and apparent lack of biological uptake of 12 c during formation of the dolocrete both petrographic and carbon isotope data do not support earlier assertions that palaeoproterozoic subaerial surface was colonised by microbial mats a few samples have high 18 o values up to 30 despite diagenetic and metamorphic resetting of the oxygen isotope system suggesting evaporation during formation of the superficial dolocrete such documented episodes of subaerial exposure formation of hot water travertines superficial dolocrete and silcrete suggest that there must have been frequent decoupling between the kuetsjarvi depositional system and the bordering sea this imposes an additional restriction on the use of the isotopic composition of the ksf dolostones for reconstruction of the 13 c carb global secular curve

a density dependant finite element model for analysis of saltwater intrusion in coastal aquifers summary saltwater intrusion is a serious problem in coastal regions all over the world it is one of the processes that degrade water quality by raising salinity to levels exceeding acceptable drinking water standards it may occur due to human activities and or by natural events over abstraction is considered the main cause of saltwater intrusion moreover climate change and sea level rise speed up saltwater intrusion this paper presents the development and validation of a coupled transient finite element model for simulation of fluid flow and solute transport in saturate and unsaturated soils with application to study saltwater intrusion in coastal aquifers the model includes coupling of water flow air flow heat flow and solute transport furthermore transient density dependent flow is included in the model and the dependency of dispersion on velocity is considered different mechanisms that govern solute transport in porous media including advection diffusion dispersion adsorption chemical reactions and biological degradation are included in the model the governing equation of the solute transport is solved together with three balance equations for water flow air flow and heat transfer the nonlinear system of governing differential equations is solved using the finite element method in the space domain and a finite difference scheme in the time domain the model is validated by application to a standard case study from the literature henry s problem and then applied to predict saltwater intrusion in a coastal aquifer the results of the model predictions are presented and discussed

early proterozoic palaeomagnetic data from the pechenga zone north west russia and their bearing on early proterozoic palaeogeography summary an early proterozoic palaeomagnetic signature c 2125 ma verified by a positive conglomerate test is recorded in the kuetsyarvi formation pechenga group north west russia but the majority of the palaeomagnetic directions observed in the pechenga group lithologies reflect a low grade remagnetization event probably linked with the late precambrian baikalian orogeny which affected north west russia and northern norway secondary pyrrhotite is the dominant remanence carrier in the uppermost formations of the pechenga group palaeomagnetic poles from the kuetsyarvi formation differ somewhat or partially overlap with coeval palaeomagnetic poles from other tectonomagmatic provinces in northern fennoscandia but it is premature at this stage to speculate on intraplate movements during the early proterozoic besides the kuetsyarvi formation probably developed during an early phase of intracontinental rifting along the northern margin of fennoscandia similar to the present day east african rift hence younger intercontinental rifting possible seafloor spreading and subsequent convergence would remain undetected by our palaeomagnetic data palaeolatitude estimates from the kuetsyarvi formation suggest that the pechenga region was located in latitudes of around 20 to 30 during the 2100 2200ma interval these low latitude estimates are supported by the sedimentary record in the pechenga region which is characterized by red beds and evaporites comparison of fennoscandian palaeomagnetic poles with coeval poles from the slave and superior cratons laurentia questions previously publicized supercontinental configurations a close relationship between fennoscandia and early proterozoic laurentian provinces is conceivable from palaeomagnetic data but given the lack of longitudinal control as well as the choice of hemisphere such postulates are tentative at best on purely palaeomagnetic grounds

a review of single sample based models and other approaches for radiocarbon dating of dissolved inorganic carbon in groundwater abstract numerous methods have been proposed to estimate the pre nuclear detonation 14c content of dissolved inorganic carbon dic recharged to groundwater that has been corrected adjusted for geochemical processes in the absence of radioactive decay 14c0 a quantity that is essential for estimation of radiocarbon age of dic in groundwater the models approaches most commonly used are grouped as follows 1 single sample based models 2 a statistical approach based on the observed curved relationship between 14c and 13c data for the aquifer and 3 the geochemical mass balance approach that constructs adjustment models accounting for all the geochemical reactions known to occur along a groundwater flow path this review discusses first the geochemical processes behind each of the single sample based models followed by discussions of the statistical approach and the geochemical mass balance approach finally the applications advantages and limitations of the three groups of models approaches are discussed the single sample based models constitute the prevailing use of 14c data in hydrogeology and hydrological studies this is in part because the models are applied to an individual water sample to estimate the 14c age therefore the measurement data are easily available these models have been shown to provide realistic radiocarbon ages in many studies however they usually are limited to simple carbonate aquifers and selection of model may have significant effects on 14c0 often resulting in a wide range of estimates of 14c ages of the single sample based models four are recommended for the estimation of 14c0 of dic in groundwater pearson s model ingerson and pearson 1964 pearson and white 1967 han plummer s model han and plummer 2013 the iaea model gonfiantini 1972 salem et al 1980 and oeschger s model geyh 2000 these four models include all processes considered in single sample based models and can be used in different ranges of 13c values in contrast to the single sample based models the extended gonfiantini zuppi model gonfiantini and zuppi 2003 han et al 2014 is a statistical approach this approach can be used to estimate 14c ages when a curved relationship between the 14c and 13c values of the dic data is observed in addition to estimation of groundwater ages the relationship between 14c and 13c data can be used to interpret hydrogeological characteristics of the aquifer e g estimating apparent rates of geochemical reactions and revealing the complexity of the geochemical environment and identify samples that are not affected by the same set of reactions processes as the rest of the dataset the investigated water samples may have a wide range of ages and for waters with very low values of 14c the model based on statistics may give more reliable age estimates than those obtained from single sample based models in the extended gonfiantini zuppi model a representative system wide value of the initial 14c content is derived from the 14c and 13c data of dic and can differ from that used in single sample based models therefore the extended gonfiantini zuppi model usually avoids the effect of modern water components which might retain bomb pulse signatures the geochemical mass balance approach constructs an adjustment model that accounts for all the geochemical reactions known to occur along an aquifer flow path plummer et al 1983 wigley et al 1978 plummer et al 1994 plummer and glynn 2013 and includes in addition to dic dissolved organic carbon doc and methane ch4 if sufficient chemical mineralogical and isotopic data are available the geochemical mass balance method can yield the most accurate estimates of the adjusted radiocarbon age the main limitation of this approach is that complete information is necessary on chemical mineralogical and isotopic data and these data are often limited failure to recognize the limitations and underlying assumptions on which the various models and approaches are based can result in a wide range of estimates of 14c0 and limit the usefulness of radiocarbon as a dating tool for groundwater in each of the three generalized approaches single sample based models statistical approach and geochemical mass balance approach successful application depends on scrutiny of the isotopic 14c and 13c and chemical data to conceptualize the reactions and processes that affect the 14c content of dic in aquifers the recently developed graphical analysis method is shown to aid in determining which approach is most appropriate for the isotopic and chemical data from a groundwater system

constraining spatial variability in recharge and discharge in an arid environment through modeling carbon 14 with improved boundary conditions carbon 14 14c has been widely used to estimate groundwater recharge rates in arid regions and is increasingly being used as a tool to assist numerical model calibration however lack of knowledge on 14c inputs to groundwater potentially limits its reliability for constraining spatial variability in recharge in this study we use direct measurements of 14c in the unsaturated zone to develop a 14c input map for a regional scale unconfined aquifer in the ti tree basin in central australia the map is used as a boundary condition for a 3 d groundwater flow and solute transport model for the basin the model is calibrated to both groundwater 14c activity and groundwater level and calibration is achieved by varying recharge rates in 18 hydrogeological zones we test the sensitivity of the calibration to both the 14c boundary condition and the number or recharge zones used the calibrated recharge rates help resolve the conceptual model for the basin and demonstrate that spatially distributed discharge through evapotranspiration is an important part of the water balance this approach demonstrates the importance of boundary conditions for 14c transport modeling 14c input activity for improving estimates of spatial variability in recharge and discharge

new isotopic and geochemical data from the palaeoproterozoic pechenga greenstone belt nw russia implication for basin development and duration of the volcanism abstract the north pechenga group of the pechenga greenstone belt comprises a thick supracrustal succession developed within a time interval of ca 500 ma in the early part of the palaeoproterozoic era it records several important global events leading to the onset of modern style earth system but the temporal evolution of the belt is still insufficiently established new nd isotope data clearly indicate an abrupt change from a strong crustal signature in the lower two volcanic units to a depleted mantle like signature in the upper two volcanic units which conforms with the coeval shift of the volcanism from subaerial to submarine indicating a significant thinning of the lithosphere due to continental rifting the timing of the change in the geotectonic regime can be bracketed between 2058 6 ma u pb data and 2018 54 ma sm nd data in situ ion microprobe analyses of zircon grains from a thin felsic tuff member in the upper part of the succession pilgujarvi volcanic formation produced an age of 1988 3 ma which is within error the same as has been reported previously for the ferropicritic magmatism that produced the pechenga ni cu ores it is concluded that the upper 3 km thick volcanic pile dominated by tholeiitic basalts and minor ferropicrites was generated within a short time span unresolvable with current geochronological tools geochemical and isotopic data suggest that the felsic tuffs were generated from a ferropicritic parental magma via extensive fractional crystallisation and the presence of gneiss xenoliths in the tuffs reveals that this happened in a magma chamber located in the underlying archaean basement thus although the mafic subaqueous volcanism of the upper part of the belt does not bear nd isotopic or trace element evidence for contamination with ancient crustal material the rifting of the basement did not yet proceed to a total break up of the archaean craton

co2 dynamics in the amargosa desert fluxes and isotopic speciation in a deep unsaturated zone 1 natural unsaturated zone gas profiles at the u s geological survey s amargosa desert research site near beatty nevada reveal the presence of two physically and isotopically distinct co2 sources one shallow and one deep the shallow source derives from seasonally variable autotrophic and heterotrophic respiration in the root zone scanning electron micrograph results indicate that at least part of the deep co2 source is associated with calcite precipitation at the 110 m deep water table we use a geochemical gas diffusion model to explore processes of co2 production and behavior in the unsaturated zone the individual isotopic species 12co2 13co2 and 14co2 are treated as separate chemical components that diffuse and react independently steady state model solutions constrained by the measured 13c in co2 and 14c in co2 profiles indicate that the shallow co2 source from root and microbial respiration composes 97 of the annual average total co2 production at this arid site despite the small contribution from deep co2 production amounting to 0 1 mol m 2 yr 1 upward diffusion from depth strongly influences the distribution of co2 and carbon isotopes in the deep unsaturated zone in addition to diffusion from deep co2 production 14c exchange with a sorbed co2 phase is indicated by the modeled 14c profiles confirming previous work the new model of carbon isotopic profiles provides a quantitative approach for evaluating fluxes of carbon under natural conditions in deep unsaturated zones

chemostratigraphy of carbonates from the minas supergroup quadrilatero ferryifero iron quadrangle brazil a stratigraphic record of early proterozoic atmospheric biogeochemical and climactic change the ca 2 42 ga old gandarela formation overlies the finely laminated caue banded iron formation bif of the itabira group minas supergroup brazil and consists of red carbonate facies bif grading upsection into buff dolomites and limestones which are locally stromatolitic carbonates of the gandarela formation have 1 3 c values ranging narrowly from 1 6 to 0 4 permil versus pdb n 93 the cercadinho formation at the base of the overlying piracicaba group is a thick arenaceous succession with rare thin carbonates that have 1 3 c values ranging from 3 3 to 5 4 permil n 12 stromatolitic dolomites of the overlying fecho do funil formation have pb pb carbonate age 2 11 0 11 ga babinski and others 1995 that provide the minimum age for this unit and 1 3 c values ranging from 5 6 to 7 4 permil n 69 at present we find no evidence in brazil for the any of the three early paleoproterozoic glacial events recognized in 2 45 to 2 22 ga sedimentary successions in north america given the radiometric constraints however it is possible that geological and geochemical traces of these ice ages are missing along the unconformity between the gandarela and cercadinho formations if correct carbonates of the gandarela formation may provide a record of the carbon isotope composition of the seawater prior to any of the paleoproterozoic ice ages combined with other available 1 3 c data results from the gandarela formation suggest that seawater preceding the ice ages was not significantly enriched in 1 3 c on the other hand the carbon isotopic signature of the cercadinho carbonates and chemical composition of the cercadinho arenites are consistent with deposition after the end of the glacial epoch and likely during the early stage of ca 2 22 to 2 1 ga carbon isotope excursion the 1 3 c values of marine carbonates of the fecho do funil formation are consistent with carbon isotope record of contemporaneous carbonate successions worldwide providing additional evidence for a global biogeochemical anomaly at ca 2 22 to 2 1 ga these compositional and isotopic changes allow integration of the minas supergroup into the global record of the paleoproterozoic evolution as well as correlation with other successions of similar age

laboratory scale saltwater behavior due to subsurface cutoff wall artificial subsurface barriers are among several countermeasures proposed to control seawater intrusion into coastal aquifers we performed experimental and numerical studies to investigate the dynamics of residual saltwater trapped in the storage area upon installation of cutoff walls experimental results showed that after wall installation the residual saltwater wedge initially flattened causing its toe to advance and then gradually retreated before being completely removed from the reservoir behind the cutoff wall the seawat model predicted the behavior of the advancing saltwater intrusion wedge and the retreating residual saltwater after cutoff wall installation flow patterns showed that dispersed saltwater flowed with the freshwater discharge along the mixing zone and over the cutoff wall eventually all remaining saltwater in the storage area was flushed out experimental and numerical results showed that a shorter cutoff wall achieved a faster removal rate of residual saltwater than a higher wall simulations of shorter cutoff wall heights show that a minimum height limit on the cutoff wall is needed to achieve complete removal of residual saltwater residual saltwater will be flushed if the wall height exceeds the thickness of the saltwater wedge at that position

multiple causes of earth s earliest global glaciation in the context of earth system evolution the causal factors driving the palaeoproterozoic huronian global glaciations occupy a central position the rise of o2 at 2320 ma which eliminated most of the methane was not apparently a single cause triggering the glaciation at c 2450 ma mantle plume driven continental uplifts led to the emplacement of voluminous continental flood basalts in low latitudes that were subsequently dissected by rifting major topographical features and continental drainage patterns were most likely similar to those in younger continental flood basalt provinces and would have enabled deep weathering and erosion of extensive basalt covered continental areas intense consumption of atmospheric co2 by silicate weathering of fresh basaltic surfaces would have been further amplified by a constant organic carbon burial rate these factors similar to those of younger glacial periods in combination with the diminished ch4 greenhouse led to an onset of global cooling at the million year timescale

processes operating during the initial stage of magma chamber evolution insights from the marginal reversal of the imandra layered intrusion russia the 13 m thick marginal zone of the 3 5 km thick mafic imandra layered intrusion ili consists of fine grained pigeonite gabbros that are chilled against the underlying host andesitic basalts but reveals a non chilled highly irregular upper contact with orthopyroxenites of the overlying layered series the marginal zone shows pronounced reverse compositional trends from the bottom to the very top and can therefore be referred to as a marginal reversal in particular the mg number of pyroxenes and the an content of plagioclase as well as the whole rock mgo mg number and normative an content show a systematic upward increase whereas all incompatible components e g tio2 k2o p2o5 rb ba zr y ree reveal an upward decrease similar reverse compositional trends are characteristic of intratelluric phenocrysts of plagioclase and inverted pigeonite that occur throughout the entire marginal zone the marginal zone is abruptly terminated by the overlying coarse grained orthopyroxenites which are interlayered with massive chromitite of the layered series the boundary between these two major units of the ili represents a sharp break in terms of grain size chemical composition and crystallization sequence it is noteworthy that the fine grained pigeonite gabbros of the marginal zone are distinguished by much lower concentrations of all incompatible elements than the coarse grained orthopyroxenite of the layered series the data indicate that filling of the chamber started with evolved phenocryst bearing liquids that probably represent the leading fractionates of parental basaltic magma that crystallized against the sidewalls of a deep conduit system the formation of the marginal zone from these evolved liquids was interrupted by the emplacement of a large batch of parental magma that reached the chamber without much fractionation en route to crystallize into the layered series the origin of the marginal reversal is best explained by the three increase model which implies that rocks becomes more primitive inwards in response to 1 an inward increase in the extent of primitivity of successively intruding magma pulses 2 an inward increase in the degree of chemical equilibrium among the phases and 3 an inward increase in the proportion of crystallizing cumulus minerals the notable distinction in incompatible element abundances between the marginal zone and the layered series is attributed to fundamentally different regimes of magma flow during their formation the crystallization of the marginal zone was dominated by fast flowing 0 5 5 m s intruding magmas that favoured the effective removal of evolved liquids from in situ growing crystals and the generation of incompatible element depleted mesoto adcumulates fine grained pigeonite gabbro in contrast the formation of the layered series was associated with a slow flowing 0 5 5 km a thermally convecting magma that was much less effective in stripping evolved liquid from the crystallizing minerals and therefore gave rise to incompatible element enriched orthocumulates coarse grained orthopyroxenites the proposed sequence of magma replenishment and rock forming processes may be common during the initial stage of the development of basaltic magma chambers

sulfur isotopic trends and iron speciation from the c 2 0 ga pilgujarvi sedimentary formation nw russia abstract sulfide sulfur isotope values and iron speciation data are reported here for sediments from the 2 0 ga old pilgujarvi sedimentary formation pechenga greenstone belt nw russia sulfides are abundant throughout the c 1400 m thick turbiditic sandstone siltstone shale succession and present as pyrite and pyrrhotite a stratigraphic trend is discernible with respect to sulfide mineralogy and sulfur isotopic compositions changing up section from highly to less variable and positive 34 s values the occurrence of pyrrhotite particularly high in the upper part of the section is thought to be the result of decomposition of pyrite during low grade metamorphism this is evidenced by the crystallographic habit and sulfur isotopic composition of the different sulfide minerals the 34 s of both sulfur species is quite variable in the lower part of the formation 9 5 to 18 7 while the upper part displays a smaller fluctuation in 34 s 4 4 13 3 the pyrrhotite is generally depleted in 34 s by approximately 3 6 average isotopic difference between pyrrhotite and pyrite compared to the pyrite this shift in the sulfur isotopic composition results from thermal decomposition of pyrite the overall spread in 34 s is indicative for the microbial reduction of sulfate but 34 s values suggest a sulfate limited environment in the upper part of the formation we note however that the sulfate limitation is restricted to the pore water realm caused by high sedimentation rates that inhibited a sufficiently high sulfate flux from the overlying water column into the sediment based on iron speciation data a previous characterization of the depositional environment as non euxinic can be specified more precisely we note that the siliciclastic succession of the pilgujarvi sedimentary formation was deposited under anoxic and ferruginous water column conditions derived from high ratios of fe hr fe t and low ratios of fe py fe hr

discussion about the validity of sharp interface models to deal with seawater intrusion in coastal aquifers analytical models have been exhaustively used to study simple seawater intrusion problems and the sustainable management of groundwater resources in coastal aquifers because of its simplicity easy implementation and low computational cost most of these models are based on the sharp interface approximation and the ghyben herzberg relation and their governing equations are expressed in terms of a single potential theory to calculate critical pumping rates in a coastal pumping scenario the ghyben herzberg approach neglects mixing of fresh water and seawater and implicitly assumes that salt water remains static therefore the results of the analytical solutions may be inaccurate and unacceptable for some real complex case studies this paper provides insight into the validity of sharp interface models to deal with seawater intrusion in coastal aquifers i e when they can be applied to obtain accurate enough results for that purpose this work compares sharp interface solutions based on the ghyben herzberg approach with numerical three dimensional variable density flow simulations for a set of heterogeneous groundwater flow and mass transport parameters and different scenarios of spatially distributed recharge values and spatial wells placement the numerical experiment has been carried out in a 3d unconfined synthetic aquifer using the finite difference numerical code seawat for solving the coupled partial differential equations of flow and density dependent transport this paper finds under which situations the sharp interface solution gives good predictions in terms of seawater penetration transition zone width and critical pumping rates additionally the simulation runs indicate to which parameters and scenarios the results are more sensitive copyright 2013 john wiley sons ltd

pumping optimization in saltwater intruded coastal aquifers this paper investigates the hydraulic issues of pumping well optimization in saltwater intruded coastal aquifers the well field includes freshwater outflow pumping wells and a recharge canal the objective is to maximize the total pumping rate subject to the constraint of no intrusion of the saltwater front into the wells analytical solutions are presented for one well two well and one well with recharge canal problems for problems involving multiple pumping wells a structured messy genetic algorithm is used to search for the optimal solution

tectonic stratigraphic and geochemical comparisons between ca 2500 2440ma mafic igneous events in the canadian and fennoscandian shields abstract palaeoproterozoic mafic igneous rocks 2500 2440 ma are exposed in the form of layered intrusions dykes and volcanic rocks in the southern canadian shield and the fennoscandian shield both igneous events were associated with episodes of continental rifting the tectonic and regional geological evolution of the two regions during the palaeoproterozoic are strikingly similar further comparisons of the mineralogical and stratigraphic characteristics of the layered intrusions the east bull lake suite in the canadian shield and the fennoscandian suite in the fennoscandian shield show additional similarities earlier investigations have identified possible parental magmas from mafic dykes for each of the layered intrusion suites these include the so called streich dykes associated with the east bull lake suite and the viianki dykes with the fennoscandian suite the viianki dykes are more primitive in composition mg 0 66 0 78 relative to the streich dykes mg 0 62 0 65 and probably represent primary mantle derived magmas geochemical modelling suggest that these two parental magmas cannot be related through fractional crystallization the differences in ree characteristics la yb cn 3 6 9 1 for viianki dykes 3 6 3 7 for streich dykes and selected incompatible element ratios can however be accounted for by either differential amounts of upper crustal contamination or different degrees of partial melting from a similar garnet bearing mantle source the data suggest that the viianki dyke parental magmas may have been produced by a degree of partial melting that was more than a factor of two lower than that which gave rise to the more primitive parent of the streich dyke magmas we conclude that these early palaeoproterozoic igneous events in the southern canadian shield and the fennoscandian shield could have been derived from a similar mantle source that was characterized by partial melt extraction of amorb and enrichment by subduction like lree enriched fluids during the archaean

identifying global vs basinal controls on paleoproterozoic organic carbon and sulfur isotope records abstract paleoproterozoic sedimentary successions are important archives of the redox evolution of earth s atmosphere and oceans efforts to unravel the dynamics of our planet s early oxygenation from this archive rely on various geochemical proxies including stable carbon and sulfur isotopes however ancient metasedimentary rocks often experienced early and late stage bio geochemical processes making it difficult to discern primary environmental signals from bulk rock 13corg and 34s values such complexity in carbon and sulfur isotope systematics contributes to uncertainty about the redox structure of paleoproterozoic oceans a currently popular idea is that following the great oxidation event global changes led to low oxygen environments and temporally fluctuating ocean redox conditions that lasted until the neoproterozoic the volcano sedimentary rocks of the onega basin have figured prominently in this concept particularly the exceptionally organic rich rocks of the 1 98 ga zaonega formation however a growing body of evidence shows that local depositional processes acted to form the 13corg and pyrite 34s records of the zaonega formation thus calling for careful assessment of the global significance of these isotope records placing new and existing organic carbon and sulfur isotope data from the zaonega formation into the context of basin history and by comparing those results with key paleoproterozoic successions of the francevillian basin gabon the pechenga greenstone belt nw russia and the animikie basin canada we show that the stratigraphic 13corg and pyrite 34s trends can be explained by local perturbations in biogeochemical carbon and sulfur cycling without requiring global drivers despite their temporal disparity we also demonstrate that individual successions share certain geological traits e g magmatic and or tectonic activity hydrocarbon generation basin restriction suggesting that their pyrite 34s and 13corg trends were governed by common underlying mechanisms e g similar basinal evolution and biogeochemical feedbacks and are not necessarily unique to certain time intervals we further show that pyrites in these successions that are most likely to capture ambient seawater sulfate isotopic composition have consistent 34s values of 15 18 which hints at remarkable stability in the marine sulfur cycle over most of the paleoproterozoic era

kolosjoki sedimentary formation a record in the aftermath of the paleoproterozoic global positive δ13c excursion in sedimentary carbonates abstract the kolosjoki sedimentary formation of the pechenga greenstone belt north eastern fennoscandia records the aftermath of the paleoproterozoic global positive 13 c excursion in sedimentary carbonates the lomagundi jatuli isotope excursion the goals of this research were to provide detailed new data on the 13 c trend in the kolosjoki sedimentary formation and generate a secular 13 c curve for the time period immediately succeeding the lomagundi jatuli isotope excursion for these purposes sedimentary carbonate samples from two new drillcores representing the kolosjoki sedimentary formation were collected in total 88 whole rock samples and 67 micro drilled subsamples ca 1 3 mg were analyzed for the isotope composition of c and o the whole rock elemental abundances and for the composition of the acid soluble fraction the kolosjoki carbonate rocks are dolostone or calcitic dolostone mg ca 0 50 0 67 with minor limestone mg ca 0 04 0 06 only weak correlation was observed between the mn sr ratios and the 13 c and 18 o values and the carbonate samples have likely retained their near primary 13 c values the sedimentary carbonate rocks show first low 13 c values at 2 to 1 and then a subtle upward increasing 13 c trend from ca 1 to 3 the increasing 13 c trend is interpreted to record a recovery from a 13 c minimum following the lomagundi jatuli isotope excursion

the correlation between the palaeoproterozoic orogens and granulite belts in the baltic shield and north america craton a suggested model of palaeoproterozoic plate tectonics abstract the earth s archaean history was completed with the formation of the first supercontinent pangaea 0 at ca 2 5 ga ago the main tectonic units of the younger palaeoproterozoic crust in the north atlantic realm include the collision and accretional orogens and in some cases the granulite thrust nappe belts three cycles of geodynamic activities are known in palaeoproterozoic at 2 5 2 33 ga 2 25 1 9 ga and 1 9 1 82 ga not only the starting and final events of the palaeoproterozoic megacycle with the corresponding extension and compression stages but also each cycle of evolution of the collision orogens including both pechenga imandra varzuga trans hudson cape smith new quebec and other suture belts and lapland snowbird queen maud granulite thrust nappe belts and of accretional orogens svecofennian penokean wopmay are strongly correlatable the palaeoproterozoic plate tectonic evolution appears unique in the absence of 1 general dispersal of the archaean supercontinent and 2 manifestation of subduction related magmatism in the accretional orogens along the craton margins of the north atlantic realm during 2 45 to 1 93 ga i e for about 600 ma an exception from the above generalization is the reported intrusion of calc alkaline granitoid complex cutting the lower part of the huron supergroup along the passive margin of the superior craton during 2 39 2 33 ga it is presumed that during palaeoproterozoic the oceanic crust in the oceanic hemisphere underwent rapid recycling that was accompanied by unusually slow wilson type evolution within the supercontinent that was probably nowhere disrupted in full rapid recycling of oceanic crust appears possible if the mid ocean ridges mors are presumed to lie above the sea level this might have prevented hydration of oceanic lithosphere which inhibited evolution of calc alkaline magmas this particular model of global tectonics during the palaeoproterozoic may be styled as microocean tectonics to distinguish it from the archaean microplate tectonics and the phanerozoic plate tectonics

geochemical and tectono magmatic evolution of the volcano sedimentary rocks of pechenga and other greenstone fragments within the kola greenstone belt russia abstract the early proterozoic volcano sedimentary pechenga and imandra varzuga regions form the two larger fragments within the kola greenstone belt a prominent feature of the north eastern baltic shield this belt also contains three smaller fragments at polmak pasvik and ust ponoy the geology of the larger fragments consists of an older northern and a younger southern part separated by prominent conformable deformation zones accordingly the 2350 1850 ma lithological succession of the pechenga greenstone fragment is subdivided into the northern 2550 1905 ma and southern pechenga complexes 1905 1700 ma likewise the imandra varzuga fragment comprises the northern and southern imandra varzuga complexes the relatively better known northern pechenga complex is subdivided into four units which in turn are subdivided into 11 formations in contrast southern pechenga complex comprises only one unit subdivided into four volcano sedimentary and two volcanic formations both the volcanic and volcaniclastic components of these complexes are characterised by magmatic compositions ranging from basaltic andesite to trachybasalt trachyandesite basalt ferropicrite basalt picrite basalt andesite picrite basalt and andesite dacite rhyolite the gabbro wehrlite intrusions hosting the pechenga ni cu sulphide deposits lower down in the stratigraphy are petrogenetically related to ferropicritic volcanics volcanic rocks of the southern pechenga complex extruded from six autonomous contemporaneous volcanic centres the volcanic rocks belong to two geochemical cycles each starting with tholeiitic and ending with calc alkaline magmas these changes reflect magmatic responses to major tectonic phases of crustal rifting and closure changes in the sr and nd isotope ratios indicate that the magmatic melts originated in various deep mantle and mantle crustal source areas a systematic gradual geochemical change is observed between subsequent volcanic formations notwithstanding the fact that the deposition of such volcanic formations is commonly interrupted by sedimentary events changes in the magmatic source were therefore gradual and the magmatic processes were continuous the kola greenstone belt formed as an intracontinental rift kalevian rifting event that has undergone a complex tectono metamorphic evolution during the karelian orogenic megacycle 2550 1700 ma of the northern baltic shield the history of two complete tectono magmatic cycles the lapponian cycle and the svecofennian cycle within this megacycle is recorded in the volcano sedimentary successions of the pechenga fragment the complete lapponian cycle is embodied within the volcanic sequence of the imandra varzuga fragment where the composition of the volcanic and volcano sedimentary rocks range from tholeiitic and boninitic basalts to basaltic andesites calc alkaline rhyodacite boninitic picrite basalts and basaltic andesites subalkalic trachybasalts and trachyandesites here the subsequent svecofennian cycle is represented by tholeiitic basalts and ferropicrites followed al rich basalts and concluded by dacite rhyolites trachyandesites and trachytes during the final phases of the kalevian rifting event tholeiitic and ferropicritic magmas were generated from two distinct mantle sources the tholeiitic magma was derived from a subabyssal depleted mantle source in contrast the ferropicritic magma came from an abyssal metasomatically enriched mantle source the larger degree of mantle contamination in the latter was probably critical in the formation of the ni cu ores of the pechenga gabbro wehrlite intrusions

carbon dioxide respiration in the deep vadose zone implications for groundwater age dating in the deep vadose zone at the dalmeny site subsurface gas samples were collected and analyzed for co2 and the 13c and 14c ratios of that co2 high concentrations of co2 depleted in 14c near the water table necessitate the use of an open system model of calcite dissolution to match observed dissolved inorganic carbon 14c ratios just below the water table groundwater age dating models assuming closed system calcite dissolution predict incorrect groundwater age dates at the dalmeny site these results and our field observations suggest that such errors may generally occur where deep vadose generation of nonmodern co2 is not accounted for in groundwater age dating exercises

first geochronological constraint for the palaeoproterozoic lomagundi jatuli δ13c anomaly in the tandilia belt basement argentina rio de la plata craton abstract geochronological data of palaeoproterozoic carbonates with 13c values between 5 and 16 suggest that the positive carbon isotope excursion of the global lomagundi jatuli event lje occurred mostly between 2220 and 2060 ma in the southern portion of the rio de la plata craton the lje was recorded in calcite diopside marble of the tandilia belt basement the marble was found at the san miguel area as part of a metamorphic rock assemblage mainly composed of gneisses and migmatites formed during the transamazonian orogeny the latter represents the maximum magmatic and metamorphic activity in the tandilia belt basement the marble derived from a calcareous siliciclastic sedimentary marine sequence was intruded by leucogranites that provoked the san miguel skarn formation first u pb la icp ms age of 2206 14 ma obtained from titanites of the skarn also placed the metasomatic processes into the transamazonian orogeny in addition this age corresponds to the minimum age for the marble s protolith deposition which matches with the beginning of the lje worldwide these new data would favor the correlation between the san miguel marble and the montevideo formation marble of the tandilia terrane uruguay within the rio de la plata craton and not with the paso severino formation of the piedra alta terrane which is at least 60 ma younger new 13c determinations in calcite crystals from the marble allowed the lowest and the highest carbon values 3 19 and 6 90 respectively to be obtained the lowest values are within the range of normal marine carbonates between 5 and 5 despite having been altered by contact metamorphism while the highest values are typical of the lje carbonates in this sense the early deposition of the carbonate protolith within the lje together with the effect of post depositional metamorphic processes would justify the wide range of values shown by the isotopic ratios of c

1 92ga kimberlitic rocks from kimozero nw russia their geochemistry tectonic setting and unusual field occurrence abstract the kimozero body is inferred to represent the oldest known diamond bearing kimberlite it was emplaced into a basaltic sequence as a gently dipping sheet like unit comprising several rock varieties with textures indicating a supracrustal origin minor subvolcanic bodies are represented by several narrow dykes and diatremes which formed during at least two intrusive phases the kimberlitic rocks have been exposed to extensive interactions with hydrous and co 2 rich fluids which led to extreme changes in the chemical compositions of the rocks making it difficult to identify their origin geochemical data indicate a within plate anorogenic tectonic setting of the kimozero magmatic body trace element compositions show that the rocks have a clear geochemical affinity to orangeite micaceous group ii kimberlite and olivine lamproite nd and sr isotope compositions of the kimozero rocks show that they were derived from a mantle source resembling bulk silicate earth new zircon u pb isotope data indicate emplacement age of the kimberlite at 1 92 ga suggesting that the rocks were associated with a late stage of paleoproterozoic rifting of the karelian craton related to the formation and growth of the svecofennian ocean

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

a multilayered sharp interface model of coupled freshwater and saltwater flow in coastal systems model development and application a quasi three dimensional finite difference model that simulates freshwater and saltwater flow separated by a sharp interface has been developed to study layered coastal aquifer systems the model allows for regional simulation of coastal groundwater conditions including the effects of saltwater dynamics on the freshwater system vertically integrated freshwater and saltwater flow equations incorporating the interface boundary condition are solved within each aquifer leakage through confining layers is calculated by darcy s law accounting for density differences across the layer the locations of the interface tip and toe within grid blocks are tracked by linearly extrapolating the position of the interface the model has been verified using available analytical solutions and experimental results application of the model to the soquel aptos basin santa cruz county california illustrates the use of the quasi three dimensional sharp interface approach for the examination of freshwater saltwater dynamics in regional systems simulation suggests that the interface today is still responding to long term pleistocene sea level fluctuations and has not achieved equilibrium with present day sea level conditions

carbon isotope record for the onset of the lomagundi carbon isotope excursion in the great lakes area north america carbonate units of the chocolay group in the lake superior area usa and the gordon lake formation of the correlative upper huronian supergroup ontario canada were deposited after the last paleoproterozoic glacial event and an episode of intense chemical weathering the huronian supergroup contains at the base 2 45 ga volcanics and is intruded by the 2 22 ga nipissing diabase dykes and sills while the chocolay group is bracketed in age between 2 29 and 2 20 ga the lomagundi 2 22 2 1 ga carbon isotope excursion started after the paleoproterozoic glacial epoch and before a plume breakout event at 2 22 ga therefore the chocolay and upper huronian carbonates were deposited either before or during the onset of the lomagundi event notably thin carbonates of the basal gordon lake formation and thick carbonate succession of the kona dolomite in the northeastern exposures of the chocolay group record 13 c values as high as 9 5 versus v pdb similar to other successions deposited during the lomagundi event both units contain pseudomorphs and molds after sulfates this observation suggests that seawater sulfate contents rose dramatically in association with the onset of the lomagundi event and the rise of atmospheric oxygen carbonates in the western and southern exposures of the chocolay group randville and bad river dolomites and saunders formation previously assumed to be equivalent to the gordon lake formation and kona dolomite have carbon isotope values close to 0 based on basin analysis we infer that these carbonate units were deposited during a negative carbon isotope excursion after the lomagundi event started and are slightly younger than the kona dolomite and gordon lake formation this interpretation implies that the carbonate platform in the great lakes area transgressed to the west over shallow marine and fluvial deposits the negative carbon isotope excursion in the lake superior area might correspond to similar 13 c values of the mooidraai dolomite in the griqualand west basin south africa supporting correlation between paleoproterozoic successions of north america and south africa and the notion of three global glaciations in the paleoproterozoic era carbonates of the mille lacs group trout lake glen township and denham formations in minnesota have 13 c values ranging from 1 2 to 2 5 combined with geochronologic constraints these data suggest that these units were deposited after the lomagundi excursion and are related to the rifting event that led to development of the so far unrecognized 2 0 ga passive margin in the lake superior area 2006 elsevier b v all rights reserved

a review of temporal constraints for the palaeoproterozoic large positive carbonate carbon isotope excursion the lomagundi jatuli event abstract the palaeoproterozoic lomagundi jatuli event is one of the largest magnitude and earliest known positive carbonate carbon isotope excursions preserving 13 c values between 5 and 16 and even higher it is recorded in sedimentary rocks on all continents bar antarctica and spans stratigraphic thicknesses ranging from several to many tens of metres this unique positive 13 c interval signals fundamental changes in the global carbon cycle and is a key event in earth system evolution following oxygenation of earth s atmosphere here we present a comprehensive review of the age constraints on the lomagundi jatuli event the first such effort in two decades this new chronology compilation focuses on the u pb and re os chronometers and demonstrates that global synchronicity of the lomagundi jatuli event is permissible an interpretation supported by the apparent wide dispersion of lomagundi jatuli event bearing successions in the most recent palaeoproterozoic plate reconstructions assuming the lomagundi jatuli event is synchronous worldwide then the bounds on its duration range from a maximum of 249 9 myr 2306 9 ma to 2057 1 ma to a minimum of 128 9 4 myr 2221 5 ma to 2106 8 ma

1 9 1 8 ga old strike slip megashears in the baltic shield and their plate tectonic implications abstract the tectonic evolution of the ca 2 0 1 75 ga old svecokarelian fold belt is reviewed and evidence is presented for large scale intraplate strike slip movements along ductile megashears after the formation of the kola collision suture and the neighbouring granulite tanaelv thrust belt around 1 9 ga ago dextral shearing was initiated along n s trending megashears subsequent anticlockwise rotation of the initially nne ssw oriented principal compressive stress caused dextral shearing along a nw se trending megashear and reversal in the sense of shearing in the n s trending ones further anticlockwise stress rotation to a total of about 120 brought an end to sinistral shearing along the n s megashears around 1 8 ga ago and caused reversal to sinistral slip along the nw se megashear both the older 1 9 1 85 ga and younger 1 84 1 8 ga parts of this evolution are recorded within the karelian province and its southwestern margin where consolidation of the lithosphere took place shortly after 1 9 ga ago in the svecofennian province where crustal accretion did not start until around 1 9 ga ago the older movements may have caused synaccretional crustal folding but with increasing consolidation the deformation was concentrated along megashears although it is still not possible to interrelate the function of active subduction zones and intraplate megashears the evolution traced so far provides support for plate tectonic interpretations of the early proterozoic geodynamics of the baltic shield

links between palaeoproterozoic palaeogeography and rise and decline of stromatolites fennoscandian shield through a review of literature and new data we have documented two major events in the palaeoproterozoic history of stromatolites as indicated by palaeontological and palaeoenvironmental studies with a time resolution of between 40 and 200 ma we confirm semikhatov and raaben s and awramik s albeit approximately maximum in diversity and abundance of stromatolites between 2330 and 2060 ma ago jatulian diversification we suggest that this taxonomic diversity was driven by a major phase of cratonisation formation of the karelian carbonate platform and numerous rift related shallow water carbonate basins supersaturated with ca 2 mg 2 and co2 the jatulian stromatolite explosion is synchronised with a positive 13ccarb shift of jatulian age carbonates we also document stromatolite decline which occurred on the fennoscandian shield somewhere between 2060 and 1900 ma ago this decline both in abundance and in taxonomic diversity is interpreted as having been caused by the first phase of oceanisation the oceanisation led to the considerable reduction in ecological niches that could be utilised by cyanobacteria the post jatulian decline of stromatolites coincides with an abrupt downward 13corg shift from 19 to 38 and is roughly coeval with the appearance of the first eukaryotic algae documented elsewhere the systematics of the fennoscandian diversity of palaeoproterozoic stromatolites is identical to that reported from india and china and reveals a dissimilarity with abundance and diversity patterns in australia and northern america

paleoproterozoic mafic dyke swarms of the belomorian province eastern fennoscandian shield abstract paleoproterozoic mafic igneous rocks 2450 1970 ma are exposed in the form of layered intrusions dykes and volcanic rocks in the karelian kola and murmansk provinces and in the form of dykes and small intrusions in the belomorian province eastern fennoscandian shield the age and sequence of mafic dyke emplacement during the paleoproterozoic are very similar in these regions further comparisons of geochemical characteristics of mafic dyke swarms in the belomorian province and neighboring cratons show considerable similarities at least three distinct groups of paleoproterozoic mafic dykes exist in the belomorian province of the eastern fennoscandian shield they are i early mg tholeiitic dykes ii ca 2 44 2 36 ga high mg gabbronorites and iii ca 2 12 fe tholeiitic dykes research into mafic dykes of the belomorian province and their comparison with paleoproterozoic dyke swarms of the karelian kola and murmansk provinces has provided evidence for at least two extensive shared magmatic events dated to ca 2 5 2 4 ga and ca 2 1 ga in the paleoproterozoic in the eastern fennoscandian shield confirming that the belomorian province does not represent a paleoproterozoic suture but rather a deep eroded inner part of the lapland kola orogen foreland

an assessment of the importance of some parameters for seawater intrusion in aquifers and a comparison of dispersive and sharp interface modelling approaches abstract the problem considered is that of determining the location and shape of the steady interface in a coastal aquifer discharging fresh water to the sea for homogeneous isotropic aquifers the location of the interface is obtained by the boundary integral method for an abrupt interface model these results are compared with the distribution of salt in the dispersion zone where the two fluids meet as determined by a finite difference solution of the flow and convective dispersion equations considerations are restricted to a rectangular section of isotropic homogeneous aquifer and examples are limited to those showing the effects of different convection to dispersion ratios including anisotropic dispersion different fresh water flow gradients and different relative densities of seawater these examples give an indication of the relative accuracy of the abrupt interface model for different ratios of convection to dispersion and enable the influence of various parameters on the shape and extent of the dispersion zone to be studied

general geology and evolutionary history of the early proterozoic polmak pasvik pechenga imandra varzuga ust ponoy greenstone belt in the northeastern baltic shield abstract the early proterozoic polmak pasvik pechenga imandra varzuga ust ponoy greenstone belt is situated in the northeastern part of the baltic shield and is discontinuously developed over a length of ca 1000 km it comprises five main zones which are separated by longitudinal and a number of transverse syndepositional faults each zone contains a number of lithostratigraphic units at the rank of groups that are subdivided into several sedimentary and volcanic formations with a total thickness over 16 000 m the sequence comprises a series of sedimentary volcanic rhythms usually separated by stratigraphic breaks marked by palaeo weathering the groups are separated by major disconformities which may mark record rift inversion or orogenic episodes at least seven distinctive lithostratigraphic markers occur in the belt including two komatiitic volcanic series separated by immature conglomerates two red coloured proto evaporitic formations separated by the alkaline volcanics and two different black shale formations perhaps the main characteristic of the belt is the apparently long history of sedimentary volcanic development at the same site spanning a time period of 2500 to 1800 ma a three stage rift development model is considered 1 an intracontinental rift stage 2500 2100 ma separated by the major inversion 2400 2330 ma and comparable with present day afar triangle and east african rifts 2 a transitional from intracontinental to to intercontinental rift stage 2100 1970 ma with possible short lived spreading about 1990 1970 ma 3 a collision related intercontinental rift stage 1970 1800 ma followed by the svecofenian orogeny 1800 1700 ma the observed distribution of platinum group elements pge mineralization is related to layered gabbro norite complexes fedorova and panskie tundry gora general skaya intrusions dated at 2470 ma which are apparently co magmatic and coeval with the first komatiitic volcanic series seidorechka formation found in the eastern part of the belt only the major chromite occurences are connected with a layered gabbro norite intrusion imandra lopoloth which is co magmatic and coeval between 2440 2330 ma with the second komatiitic volcanic series rusinga polisarka akhmalahti and malbekk formations the ni cu deposits of the belt are connected with a differentiated gabbro werhlite complex which is co magmatic and coeval ca 1970 ma with the specific fe and ti rich ferropicrites with komatiitic affinities

assessment of sharp interface approach for saltwater intrusion prediction in an unconfined coastal aquifer exposed to pumping water over exploitation becomes a common problem in coastal aquifers as it disarranges the dynamic equilibrium of saltwater and freshwater and causes saltwater intrusion swi mathematical simulations become a necessary tool nowadays to predict swi under future pumping scenarios this study aims to assess the validity of sharp interface approach for an unconfined coastal aquifer subjected to pumping by comparison with sand tank observation and dispersive approach results the comparison was in terms of 1 transient movement of saltwater toward the well screen and 2 prediction of well salinity in times the sharp interface approach produced acceptable results although it over predicted the toe position of saltwater wedge salinity of extracted water was less predicted by sharp interface modeling the sharp interface approach was then applied for a synthetic field scale unconfined aquifer in steady condition with different pumping rates and well placements to explore the sensitivity of the modeling the results were compared with salinity contours of dispersive modeling the sharp interface approach produced better result for higher pumping rates where the saltwater was reached to the well screen additionally the results of fully penetrating wells compare to partially penetrating one and also closer location of well to shoreline matched better with the dispersive modeling outputs in real cases where the saltwater may wend a long distance toward the well screen the sharp interface modeling weakly matched with the dispersive modeling specially in terms of well salinities that is attributed to wider mixing zone

evolution of dissolved inorganic carbon in groundwater recharged by cyclones and groundwater age estimations using the 14c statistical approach abstract the canning basin is the largest sedimentary basin in western australia and is located in one of the most cyclone prone regions of australia despite its importance as a future resource limited groundwater data is available for the basin the main aims of this paper are to provide a detailed understanding of the source of groundwater recharge the chemical evolution of dissolved inorganic carbon dic and provide groundwater age estimations using radiocarbon 14 c dic to do this we combine hydrochemical and isotopic techniques to investigate the type of precipitation that recharge the aquifer and identify the carbon processes influencing 14 c dic 13 c dic and dic this enables us to select an appropriate model for calculating radiocarbon ages in groundwater the aquifer was found to be recharged by precipitation originating from tropical cyclones imparting lower average 2 h and 18 o values in groundwater 56 9 and 7 87 respectively water recharges the soil zone rapidly after these events and the groundwater undergoes silicate mineral weathering and clay mineral transformation processes it was also found that partial carbonate dissolution processes occur within the saturated zone under closed system conditions additionally the processes could be lumped into a pseudo first order process and the age could be estimated using the 14 c statistical approach in the single sample based 14 c models 14 c 0 is the initial 14 c dic value used in the decay equation that considers only 14 c decay rate a major advantage of using the statistical approach is that both 14 c decay and geochemical processes that cause the decrease in 14 c dic are accounted for in the calculation the 14 c dic values of groundwater were found to increase from 89 pmc in the south east to around 16 pmc along the groundwater flow path towards the coast indicating ages ranging from modern to 5 3 ka a test of the sensitivity of this method showed that a 15 error could be found for the oldest water this error was low when compared to single sample based models this study not only provides the first groundwater age estimations for the canning basin but is the first groundwater dating study to test the sensitivity of the statistical approach and provide meaningful error calculations for groundwater dating

tracking lateral δ13ccarb variation in the paleoproterozoic pechenga greenstone belt the north eastern fennoscandian shield abstract the kuetsjarvi sedimentary formation ksf records the global paleoproterozoic ca 2200 2100 ma positive 13 c excursion of sedimentary carbonates this event is here called as the lomagundi jatuli isotopic excursion in this study lateral 13 c carb variation in the ksf and local basinal factors amplifying global 13 c carb value were investigated and a secular 13 c curve for the ksf was constructed sedimentary carbonate samples from a new drillcore drillcore 5a from the ksf were analysed for 13 c 18 o and selected major and trace elements the 13 c values of the samples vary from 5 to 8 vpdb and the 18 o values from 18 to 10 vpdb most of the samples have retained their primary c isotopic composition as they do not show correlation between the mn sr ratios and the 13 c and 18 o values the new results were compared to those previously obtained from another drillcore drillcore x from the ksf ca 25 km along strike from drillcore 5a both cores show a similar kind of generally upward decreasing trend in 13 c excluding some negative and positive spikes in drillcore x and samples close to a contact with a fe picrite dyke in drillcore 5a a secular 13 c curve of the ksf was constructed based on the least altered 13 c data from the cores 5a and x the secular 13 c curve of the ksf may represent the latest part of the lomagundi jatuli isotopic excursion

factors affecting carbon 14 activity of unsaturated zone co2 and implications for groundwater dating summary unsaturated zone processes may influence the carbon 14 14 c activity of infiltrating groundwater and thus introduce error in derived groundwater residence times however unsaturated zone 14 c activities are rarely measured and there is little understanding of how they may vary spatially in a groundwater basin in this study we measured 14 c activity in unsaturated zone gas at five sites with different watertable depths 8 2 31 5 m in the arid ti tree basin central australia we observed a relatively uniform decrease in 14 c activity of unsaturated zone gas with depth at most sites with variation in unsaturated zone depths leading to variation in 14 c activities directly above the watertable at each site ranging from 54 to 106 percent modern carbon pmc through modelling we show that the profiles are influenced by co 2 production at different depths from sources with different isotopic ratios including production of modern co 2 in the root zone and production of old co 2 above the watertable scenario modelling showed that these processes are independent of recharge when recharge is low 0 10 mm y 1 but that higher recharge rates 100 mm y 1 result in more advective transport of atmospheric co 2 to the watertable the variation in 14 c above the watertable was more sensitive to watertable depth and shallow and deep co 2 production rates these findings offer insight into how unsaturated zone 14 c activities may vary spatially and provide guidance as to when 14 c depletion in unsaturated zone co 2 may become important for groundwater dating particularly in arid settings

modes of seawater intrusion during transgressions analytical methods and numerical experiments are used to study salinization of groundwater in response to sea level rise the system that is studied involves a saturated porous medium with an inclined upper surface the upper surface is progressively inundated during sea level rise to simulate transgression the landward migration of the shoreline four modes of seawater intrusion are distinguished 1 horizontal intrusion for slow transgression and a relatively high permeability substrate 2 vertical intrusion by seawater fingering for fast transgression and a sand silt substrate 3 vertical intrusion by diffusion for fast transgression and a low permeability clay substrate 4 vertical intrusion by combined diffusion and low salinity fingering for fast transgression and a clay layer at the seafloor overlying an aquifer these four modes are characterized by the development of very distinctive transition zones between the fresh and salt groundwater domains an analytical expression is derived for the critical transgression rate which separates horizontal mode 1 from dominantly vertical modes 2 4 intrusion for modes 3 and 4 salinization significantly lags behind sea level rise the results are consistent with observations of fossil fresh brackish groundwater beneath many continental shelves and shallow seas

fractionation of carbon and oxygen isotopes in 13c rich palaeoproterozoic dolostones in the transition from medium grade to high grade greenschist facies a case study from the kola superdeep drillhole samples from the kola superdeep drillhole 12 262 m a deep drillhole 1060 m and from the surface seaprated by only around 10 km provided a unique opportunity for direct tracing of 13 c and 18 o changes through a low to high grade greenschist facies transition within impure 13 c rich palaeoproterozoic dolostones the least altered dolostones have 13 c of 9 and 18 o of 22 the metamorphic transition is expressed by dolomite calcite 1 quartz k feldspar tremolite calcite 2 dolomite calcite 1 and defined by 13 c depletion of calcite 2 c 3 0 calcite 1 1 0 2 0 and dolomite 18 o shows a considerable resetting in all carbonate components by around 6 caused by a rayleigh distillation process coupled with isotopic exchange between the carbonates and fluids with an external source of oxygen the retrograde alteration is expressed by the formation of quartz chlorite veinlets within tectonically bound zones of brecciated and sheared dolostones the maximum 18 o depletion in dolomite 9 and calcite 1 c 4 were probably controlled by infiltration into permeable zones of external fluids associated with retrograde alteration 13 c remains largely unaffected

proterozoic zircon ages from lower crustal granulite xenoliths kola peninsula russia evidence for crustal growth and reworking lower crustal garnet granulite xenoliths from beneath the kola karelian domain of the fennoscandian shield russia were brought to the surface in devonian lamprophyre diatremes to establish the relationships between processes in the lower crust and geological events recorded in the upper crust zircons from two of these xenoliths were dated by ion microprobe one xenolith contains mainly primary magmatic zircon grains that yielded an average age of 2 47 ga the kola karelia domain formed part of a large basaltic igneous province in the earliest proterozoic c 2 45 ga thus such xenoliths probably represent deep seated equivalents of this magmatism a second garnet granulite xenolith contained only internally featureless zircons most of these yielded concordant ages between 1 77 1 61 ga this age distribution indicates that at c 1 7 ga the protolith was migmatized during an event that may be related to emplacement of granites and pegmatites in the region however two zircon grains in the second xenolith gave much younger ages of 1 47 and 1 45 ga this spread in the ages is related to an unknown younger event around 1 4 ga or perhaps later when the c 1 7 ga migmatite zircons were reset to variable degrees these zircon ages are evidence for the complex evolution of the lower crust recording multiple events some of which are not currently expressed on the surface

early paleoproterozoic archean dykes and gneisses in russian karelia of the fennoscandian shield new paleomagnetic isotope age and geochemical investigations abstract we present here new palaeomagnetic isotopic age and geochemical data from archean and early palaeoproterozoic rocks in the eastern fennoscandian shield we have studied ne sw trending gabbronorite dyke sets and their host archean basement rocks in the vodlozero block near the 2449 ma burakovka layered intrusion in southern russian karelia both dyke sets are genetically related to the burakovka intrusion the other ca 25 km long avdeev dyke locating a few kilometers south from the burakovka intrusion yields a stable single component remanence direction that is in agreement with the direction previously obtained from the burakovka intrusion another ne sw trending dyke 0 8 m wide shalskiy diabase dyke about 30 km south of the burakovka intrusion yields a similar remanence direction as the avdeev dyke the overall mean remanence direction has a palaeopole at plat 12 3 n plong 243 5 e a 95 15 4 4 sites 28 samples the thin shalskiy diabase dyke transects a similarly ne sw trending 500 m wide coarse grained gabbronorite dyke which has now been dated by sm nd method as 2608 56 ma geochemically all the dykes are quite similar showing slight calc alkaline affinity and low tio 2 and high sio 2 with moderate mgo and low cr and ni furthermore the dykes are geochemically identical to the 2 45 ga dyke swarm in the northern karelian province the remanence direction of the thin shalskiy diabase dyke differs significantly from the high temperature and high coercivity remanence component of the unbaked archean gabbronorite dyke which yields a palaeopole at plat 22 7 n plong 222 1 e dp 8 2 dm 16 2 five samples on the basis of different remanence directions of the diabase dyke and the unbaked archean gabbronorite dyke the baked contact test for the diabase dyke is positive in addition to the high temperature and high coercivity component of the baked and unbaked archean gabbronorite dyke in low temperatures and coercivities we isolated a similar component as in the diabase dyke a comparable remanence component was also obtained from the archean basement at ca 8 km from the dykes we propose that in the studied area the archean basement and the archaean dyke were partly remagnetized due to emplacement and subsequent uplift and cooling of the large burakovka layered intrusion and related dykes at about 2 40 ga ago this interpretation lends support from a new 40 ar 39 ar dating of hornblende from another area lake paajarvi area in northern karelia there a negative baked contact test was previously obtained for the remanence of the dated ca 2 45 ga dyke rocks related to the ca 2 45 ga oulanka layered intrusion the 40 ar 39 ar dating of the unbaked archean basement which yields the same remanence component as the dykes shows a plateau age of ca 2 6 ga but in addition it also shows resetting of the basement at ca 2 4 ga ago the dating thus supports reactivation and partial remagnetization of the archean basement at ca 2 4 ga ago our new palaeomagnetic results from the burakovka dykes and the new 40 ar 39 ar dating from the lake paajarvi area give support to our previous interpretation that at lake paajarvi area the remanence component suggested to be 2 4 ga despite to negative baked contact test is indeed of this age therefore it is implied that the results can be used for continental reconstructions

chemistry of unsaturated zone gases sampled in open boreholes at the crest of yucca mountain nevada data and basic concepts of chemical and physical processes in the mountain boreholes open to the unsaturated zone at the crest of yucca mountain nevada were variously sampled for co2 including 13c and 14c ch4 n2 o2 ar cfc 11 cfc 12 and cfc 113 from 1986 to 1993 air enters the mountain in outcrops principally on the eastern slope is enriched in co2 by mixing with soil gas and is advected to the mountain crest where it returns to the atmosphere the cfc data indicate that travel times of the advecting gas in the shallow tiva canyon hydrogeologic unit are 5 years the 14c activities are postbomb to depths of 100 m indicating little retardation of 14co2 in the shallow flow systems the 14c activities from 168 to 404 m in the topopah spring hydrogeologic unit are 85 90 pmc at borehole usw uz6 the cfc data show that the drilling of usw uz6 in 1984 has altered the natural system by providing a conduit through the paintbrush nonwelded unit allowing flow from topopah spring outcrops in solitario canyon on the west to usw uz6 upward in the borehole through the paintbrush to the shallow tiva canyon flow systems and out of the mountain

time response of the water table and saltwater transition zone to a base level drop 1 this paper investigates the effect of a drainage base level drop on the groundwater system in its vicinity using theoretical analysis simulations and field data we present a simple and novel method for analyzing the effect of a base level drop by defining two characteristic times that describe the response of the water table and the transition zone between the fresh and saline water the dead sea was chosen as a case study for this process because of the lake s rapid level drop rate during a continuous lake level drop the discharge attains a constant value and the hydraulic gradient remains constant we describe this new dynamic equilibrium and support it by theoretical analysis simulation and field data using theoretical analysis and sensitivity tests we demonstrate how different hydrological parameters control the response rate of the transition zone to the base level drop in some cases the response of the transition zone may be very rapid and in equilibrium with the water table or alternatively it can be much slower than the water table response as is the case in the study area

alkaline rocks and carbonatites of northwestern russia and northern norway linked wilson cycle records extending over two billion years 1 tectonic analysis reveals a previously unidentified link between alkaline rocks and carbonatites arcs forming the kola alkaline and carbonatite province kacp in arctic russia and arcs of the seiland igneous province sip in the northern caledonides of finnmark norway we here conclude that the rocks of the two provinces have been derived by decompression melting of deformed alkaline rocks and carbonatites darcs under rifts and within the underlying lithospheric mantle preserved within the paleoproterozoic lapland kola suture zone lksz and its extension beneath the allochthons of the norwegian caledonides the lksz projects under the caledonide allochthons to the postulated site of eruption of the arcs of the sip in an intra continental rift at a place where an ocean was soon to open we suggest that the sip arcs formed in this intra continental rift by decompression melting involving darcs that had lain in the underlying lithospheric mantle within the along strike extension of the lksz for more than one billion years thrusting and metamorphism during the scandian collision between laurentia and baltica transformed the sip arcs into darcs that occupy the immediate footwall to the suture zone between laurentia and baltica at the collision the sip rocks were carried south southeastwards from their then location on the outermost continental margin of baltica to their current location in the highest level of a sandstone dominated nappe complex the arcs and darcs of kola and finnmark provide independent evidence of the operation of two complete wilson cycles of the opening and the closing of oceans in the region