accommodation and sediment supply controls on clastic parasequences a meta analysis this study combines data from many published case studies to undertake a quantitative characterization of clastic parasequences with the aim to determine how accommodation sediment supply and autogenic sediment storage dynamics are recorded in their sedimentary architecture and stacking patterns results of this study are used to critically evaluate the validity of paradigms and models that are routinely used to explain and predict trends in the anatomy and arrangement of parasequences data on 957 parasequences from 62 case studies of clastic shallow water successions were coded in a relational database which includes outcrop and subsurface datasets of ancient and quaternary examples these units cover the preserved records of both river dominated deltas and wave dominated coasts representing shoreline transits over a breadth of timescales likely of both local and regional extent the role of extant accommodation rates of creation of accommodation and rates of sediment supply in determining parasequence architecture is assessed through analysis of relationships between i proxies of these variables at different scales rates of aggradation and progradation facies belt shoreline trajectories systems tract type parasequence set stacking patterns parasequence progradation angle and stratigraphic rise size of feeder rivers and ii parameters that describe the geometry and stacking style of parasequences and associated shallow water sand bodies statistical analyses of database outputs indicate which proxies of accommodation sediment supply and accommodation sediment supply ratio are significant as predictors of parasequence architecture and allow for interpretations of the importance of allogenic and autogenic factors the principal results of this study reveal the following i parasequence thickness varies as a function of water depth accommodation generation and erosional truncation and these variations are also reflected across types of systems tracts and parasequence sets ii the dip length of parasequence sand bodies demonstrates scaling with measures of accommodation sediment supply ratio at multiple scales partly in relation to the possible effect of sediment supply on progradation rates iii in systems tracts stratigraphic trends in parasequence stacking due to autogenic mechanisms or to acceleration or deceleration in relative sea level fluctuations are not revealed quantitatively iv some association is seen between the abundance of deltaic or river dominated parasequences and progradational stacking v positive but modest correlation is observed between measures of river system size and the dip length of shallow marine parasequence sand bodies the resulting insights can be applied to guide sequence stratigraphic interpretations of the rock record and the characterization of sub seismic stratigraphic architectures of subsurface successions

biostratigraphic units and tectonism in mid cretaceous foreland of wyoming colorado and adjoining areas abstract chronolithologic units and unconformities in mid cretaceous formations of the central rocky mountains region indicate widespread marine transgressions and regressions as well as recurrent deformation of the foreland in the western interior during cenomanian turonian and coniacian times 88 96 ma the stratigraphic record of the widely recognized cenomanian and early turonian transgression middle turonian end page 856 regression and late turonian and coniacian transgression was modified in several areas by episodes of slight uplift and attendant erosion the most evident tectonism was in western montana during the middle to late cenomanian 93 94 ma in western wyoming and adjoining areas during the early turonian to earliest middle turonian 90 91 ma in north central colorado eastern wyoming and northwestern wyoming in the early late turonian 89 8 ma and in northeastern colorado wyoming and southwestern montana in the late late turonian 89 3 ma crestlines of most of the swells trend generally either northwest or northeast the tectonism of the mid cretaceous foreland corresponds in age to displacements of thrusts in the sevier orogenic belt of southwestern wyoming and southeastern id ho furthermore much of the foreland deformation probably reflects episodes of eastward thrusting in the thrust belt end of article last page 857

climate control of decadal scale increases in apparent ages of eogenetic karst spring water abstract water quantity and quality in karst aquifers may depend on decadal scale variations in recharge or withdrawal which we hypothesize could be assessed through time series measurements of apparent ages of spring water we tested this hypothesis with analyses of various age tracers 3h 3he sf6 cfc 11 cfc 12 cfc 113 and selected solute concentrations dissolved oxygen do no3 mg and so4 from 6 springs in a single spring complex ichetucknee springs in northern florida over a 16 yr period these springs fall into two groups that reflect shallow short group 1 and deep long group 2 flow paths some tracer concentrations are altered with cfc 12 and cfc 113 concentrations yielding the most robust apparent ages these tracers show a 10 20 yr monotonic increase in apparent age from 1997 to 2013 including the flood recession that followed tropical storm debby in mid 2012 this increase in age indicates most water discharged during the study period recharged the aquifer within a few years of 1973 for group 2 springs and 1980 for group 1 springs inverse correlations between apparent age and do and no3 concentrations reflect reduced redox state in older water positive correlations between apparent age and mg and so4 concentrations reflect increased water rock reactions concentrated recharge in the decade around 1975 resulted from nearly 2 m of rain in excess of the monthly average that fell between 1960 and 2014 followed by a nearly 4 m deficit to 2014 this excess rain coincided with two major el nino events during the maximum cool phase in the atlantic multidecadal oscillation although regional water withdrawal increased nearly 5 fold between 1980 and 2005 withdrawals represent only 2 5 of ichetucknee river flow and are less important than decadal long variations in precipitation these results suggest that groundwater management should consider climate cycles as predictive tools for future water resources

significance of clay mineral assemblages in the antarctic ocean abstract typical examples from different morphological and geological settings in the antarctic ocean are reviewed in order to discuss the value of clay mineral assemblages for reconstructing the glacial history of antarctica the paleoceanographic history of the antarctic ocean and the sedimentary processes at the antarctic continental margin the significance of clay minerals for paleoenvironmental reconstructions strongly varies with both the position of the sites under investigation and the age of the sediments in late mesozoic to paleogene sediments clay mineral assemblages are sensitive tools for reconstructing climatic conditions for example the shift from smectite dominated assemblages to illite and chlorite dominated assemblages in the earliest oligocene clearly documents the transition from chemical weathering conditions under a warm and humid climate to physical weathering under cooler conditions submarine elevations such as maud rise and kerguelen plateau give the best record for direct paleoclimatic and paleoceanographic studies at the proximal sites of the continental slope and shelf as well as in the deep sea the paleoclimatic information normally is masked by a variety of processes resulting in sediment redistribution at those sites in contrast the clay mineral assemblages bear a wealth of information on different sedimentary processes after the establishment of a continental east antarctic ice sheet physical weathering prevailed variations in the clay mineral records predominantly reflect the influence of different sediment sources resulting from different glacial hydrographic or gravitational transport processes because these sedimentation processes are generally linked to climatic variations the clay mineral assemblages in most of the neogene and quaternary sediments provide indirect paleoclimatic information the processes are best documented in the clay mineral composition in those areas where changes in source regions with distinct petrographic differences are expected and where distances from the source region are low

recharge of the upper chalk aquifer at a site in hampshire england 2 solute movement abstract this paper describes a field experiment to study the movement of solutes through the unsaturated zone of the chalk using soil physical techniques to calculate water fluxes and sequential soil coring to measure solute concentrations with depth and time deuterium oxide was used as a tracer to follow water movement nitrate leaching beneath spring barley was calculated below the root zone approximately 40 kg ha 1 yr 1 of nitrate nitrogen were leached beyond root depth 1 m in the two study years at concentrations of between 20 and 75 mg l 1 and at a downward velocity of 0 85 m yr 1

migration of dynamic subsidence across the late cretaceous united states western interior basin in response to farallon plate subduction backstripped cross sections of the late cretaceous succession across central utah colorado and southern wyoming in the western interior basin united states reveal a component of continuously evolving long wavelength residual subsidence in addition to subsidence driven by the sevier thrust belt and associated sediment loads the loci of maximum rates of this residual subsidence moved eastward from ca 98 to 74 ma in phase with the west to east passage of the farallon slab as reconstructed from tomography based on quantitative inverse models these new subsidence data allow testing of existing subduction models and confi rm the dynamic subsidence origin of the western interior basin furthermore regional variations in subsidence rates suggest a possible defi cit of negative buoyancy mantle loading inside the slab beneath colorado supporting the hypothesis that the thickened slab represents a subducted oceanic plateau this paper documents how the cretaceous stratigraphy records the timing patterns and position of underlying mantle processes during farallon slab subduction the new data also reveal patterns indicative of the commencement of the laramide orogeny in the western united states

mineralogy of the upper albian sediments from the kirchrode i borehole with special emphasis on the clay mineralogy abstract the mineralogy of a 245 m thick section of upper albian marly clay stones to clayey marlstones from the kirchrode i borehole lower saxony basin of nw germany has been studied by x ray diffractometry infrared spectrometry chemical analysis and microscopy the investigations were carried out on bulk samples and grain size fractions the mineralogy of the sediments is characterised by biogenous carbonates mainly calcite by terrigenous detrital components and diagenetic minerals often enriched in concretions the calcite content fluctuates considerably between 20 and 50 most probably because of changes in the marine palaeoenvironment illite montmorillonite and kaolinite are the predominant clay minerals but in changing portions chlorite and alkali feldspars were detected only in traces mixed layer minerals such as illite smectites i s are also present in higher amounts in the lower part and less in the upper part of the core reworked upper carboniferous mudstones and siltstones are interpreted to have delivered part of the well crystallised illite kaolinite chlorite and quartz montmorillonites and mixed layer minerals together with kaolinite and illite may be inherited from weakly consolidated jurassic sediments aptian and albian claystones and marlstones and from palaeosols the increase in the proportion of montmorillonite among the clay minerals in the upper part of the upper albian may be due to redistribution of volcanic sediments after either terrestrial or submarine alteration of volcanic ash volcanic activity is known in this area e g the middle to upper albian flammenmergel at the southern margin of the lower saxony basin and around the north atlantic throughout aptian albian time but in the kirchrode i core ash fall was identified as a source for montmorillonite in only one layer namely at 87 25 m where high zr and nb concentrations were also found the mineralogical composition of the concretionary material is generally a mixture of biogenous calcite siliciclastic debris quartz and clay minerals and microcrystalline diagenetically formed fe mn carbonates rhodochrosite siderite and carbonate fluorapatite francolite rhodochrosite is more abundant in the lower part mn siderite in the upper part of the core concretions with fluorapatite francolite occur sporadically

underground renewal time and mixing of the main mineral waters of tunisia a multi tracer study bottled waters are increasingly popular in tunisia most of them come from groundwaters thus raising the question of the long term availability of the mineral groundwater resources water collected from production springs or wells of eleven mineral waters of tunisia among the main commercial brands were analyzed for tritium 3h helium 3 sf6 cfcs and carbon 14 tracer tracer plots indicate that all of the groundwaters of our data set are a mixture of modern rainwater with older groundwater flow waters that are beyond the time scale of the transient tracers 14c data suggest that the age of these old waters which constitute the main water reservoir is of the order of radiocarbon half life or more most of the studied sites have groundwater renewal times in the range 50 150 years for the sites where tracer concentrations are the most diluted by old waters this value logically increase to several centuries

residence time mineralization processes and groundwater origin within a carbonate coastal aquifer with a thick unsaturated zone this study aims at establishing groundwater residence times identifying mineralization processes and determining groundwater origins within a carbonate coastal aquifer with thick unsaturated zone and lying on a granitic depression a multi tracer approach major ions sio2 br ba sr2 18o 2h 13c 3h ne ar combined with a groundwater residence time determination using cfcs and sf6 allows defining the global setting of the study site a typical mineralization conditioned by the sea sprays and the carbonate matrix helped to validate the groundwater weighted residence times from using a binary mixing model terrigenic sf6 excesses have been detected and quantified which permits to identify a groundwater flow from the surrounding fractured granites towards the lower aquifer principally the use of cfcs and sf6 as a first hydrogeological investigation tool is possible and very relevant despite the thick unsaturated zone and the hydraulic connexion with a granitic environment

the offshore bar revisited a new depositional model for isolated shallow marine sandstones in the cretaceous frontier formation of the northern uinta basin utah u s a abstract shallow marine sandstone bodies isolated within marine mudrock successions are still incompletely understood a robust understanding of such bodies is of interest not only scientifically but also in order to facilitate successful exploration for and production of petroleum and other natural resources such bodies are preserved in the turonian frontier formation of the northern uinta basin in utah and colorado u s a where they have been previously interpreted as the products of offshore bars a reappraisal of these bodies in the uppermost frontier formation herein defined as the turonian ashley valley member reveals three northeast southwest elongate incised highstand forced regressive and lowstand offshore sandstone bodies partially to fully encased in offshore marine mudrock these bodies are herein named the buckskin hills kane hollow and raven ridge sandstones from oldest to youngest five lithofacies were identified from 47 measured outcrop sections located along the western and southern margins of dinosaur national monument they are 1 marine shelf claystones and siltstones 2 lower upper offshore marine admixed siltstone and sandstone 3 lower upper offshore thin bedded sandstones and siltstones 4 distal lower shoreface heavily bioturbated very fine grained sandstone and 5 transgressive lag conglomerate wireline logs from 112 drillhole locations throughout the uinta basin were calibrated with nearby outcrop locations to construct cross sections and net sandstone isochore maps from these regionally traceable horizons flooding surfaces and internal erosion surfaces facilitated an analysis of stacking patterns development of a stratigraphic framework and a depositional environment interpretation overall the ashley valley member preserves a basinward offlapping stacking pattern indicative of shoreline progradation in response to the late turonian greenhorn global eustatic regression that was interrupted by two high frequency transgression regression cycles this nested cyclicity cannot be explained by global eustasy alone and instead is suggestive of a secondary allogenic control likely related to western cordilleran foreland basin wcfb geodynamic driving mechanisms as a result the ashley valley member provides an example of tectonic forcing on stratal stacking patterns highlighting the importance of intrabasinal tectonic processes on dispersal patterns and high frequency relative base level fluctuations within the wcfb stratigraphic record

natural cf4 and sf6 on earth the occurrence of cf4 and sf6 in natural fluorites caf2 is reported contents are found to be typically 200 2000 ppt mass for cf4 and 50 100 ppt mass for sf6 cf4 and sf6 were also detected in granites where fluorite is an accessory mineral cf4 and sf6 thus possess a large reservoir in the continental crust that by degassing can sustain natural atmospheric background levels of 40 ppt mole and up to 0 01 ppt mole respectively the article also discusses how natural sf6 may cause interference in hydrological tracer studies

controls on preferential recharge to chalk aquifers summary there is evidence that under certain conditions rapid preferential recharge via the fracture network can occur in chalk aquifers this has potentially important implications for contaminant migration through the chalk unsaturated zone cuz and for groundwater flooding in chalk catchments in the case of groundwater flooding deficiencies in modelling aquifer response have been attributed to inadequate representation of flow processes in the cuz in this paper we consider two complementary approaches for assessing controls on preferential recharge to chalk aquifers an empirical approach and a physically based modelling approach we show that the main controls on preferential recharge to chalk aquifers are the characteristics of rainfall events in terms of duration and intensity the physical properties of the near surface and the antecedent soil moisture in the near surface we demonstrate a number of deficiencies when past models of the cuz are applied to the problem of simulating preferential recharge notably that the assumption of instantaneous equilibrium between fractures and matrix is not valid particularly during extreme recharge events in order to simulate preferential recharge fractures and matrix must be modelled as separate but interacting domains this was achieved using a dual continua model the model was computationally demanding but was able to reproduce observed behaviour including apparently hysteretic soil moisture characteristic relationships in the near surface and rapid preferential recharge fluxes in response to high intensity rainfall events

variability of lowstand wedges and their distinction from forced regressive wedges in the mesaverde group southeast wyoming the debate on the geometry and origin of shelf sandbodies has evolved from a discussion of how sands and gravels managed to move from shorelines far out onto muddy shelves to an acceptance that many of these sandbodies did not originate on the shelf but were simply resident there after a fall and subsequent rise of sea level in the efforts to reinterpret these sandstones there has been some tendency to underestimate how varied they can be data from eight such shelf sandstone tongues campanian in southeast wyoming are used to illustrate how variable lowstand prograding wedges can be and how these should in addition be distinguished from forced regressive wedges the depositional environments encountered in these two types of wedges are surprisingly different and the lowstand wedges which are frequently tidally influenced show a greater affinity with the overlying transgressive tract than with the preceding wave dominated forced regressive shoreface deposits

evidence for crustal degassing of cf4 and sf6 in mojave desert groundwaters dissolved tetrafluoromethane cf4 and sulfur hexafluoride sf6 concentrations were measured in groundwater samples from the eastern morongo basin emb and mojave river basin mrb located in the southern mojave desert california both cf4 and sf6 are supersaturated with respect to equilibrium with the preindustrial atmosphere at the recharge temperatures and elevations of the mojave desert these observations provide the first in situ evidence for a flux of cf4 from the lithosphere a gradual basin wide enhancement in dissolved cf4 and sf6 concentrations with groundwater age is consistent with release of these gases during weathering of the surrounding granitic alluvium dissolved cf4 and sf6 concentrations in these groundwaters also contain a deeper crustal component associated with a lithospheric flux entering the emb and mrb through the underlying basement the crustal flux of cf4 but not of sf6 is enhanced in the vicinity of local active fault systems due to release of crustal fluids during episodic fracture events driven by local tectonic activity when fluxes of cf4 and sf6 into mojave desert groundwaters are extrapolated to the global scale they are consistent within large uncertainties with the fluxes required to sustain the preindustrial atmospheric abundances of cf4 and sf6

upper cretaceous vernal delta of utah depositional or paleotectonic feature a conspicuous seaward bulge of the middle to late turonian shoreline of the cretaceous seaway in northeastern utah and southwestern wyoming has been identified by previous authors as the vernal delta strata of the frontier formation and the ferron sandstone member of the mancos shale that form the vernal delta consist largely of fluviodeltaic facies the delta however is not recognizable as a locus of turonian sedimentation there is no isopach thick associated with it the vernal data is a large feature encompassing an area of at least 6250 mi sup 2 16 187 km sup 2 a comparison between the depositional setting and paleogeography of northeastern utah during the late cretaceous and a present day area on the east flank of the andes in colombia indicates strong similarities further comparison suggests that feature the size of the vernal delta could not have been produced by a single river the vernal delta overlies the ancestral uinta mountain uplift an area where cenomanian marine shales were entirely removed by what appears to have been submarine erosion during early turonian time when the shoreline prograded eastward across this area during middle uronian time the sediment load caused the area to subside but at a rate slowermore than rates of subsidence to the north and south this differential subsidence is the cause of the shoreline bulge although it includes deltaic facies the vernal delta is not a delta per se but a feature produced as the result of interaction between sedimentation and gentle tectonic movement of the ancestral uinta mountain uplift less

baseline geochemical conditions in the chalk aquifer berkshire u k a basis for groundwater quality management the chalk aquifer is the most important british aquifer and is also important over much of northern europe aquifer protection requires a sound knowledge of the baseline conditions and how these might vary or have varied with time this detailed geochemical study of a representative area of chalk in berkshire u k includes a consideration of several components 1 the inputs from the atmosphere 2 the interstitial water of the soil and the unsaturated zone 3 the interstitial water in the confined and unconfined sections of the aquifer and 4 the saturated mainly fissure flow along the hydraulic gradient which forms an important water supply of the thames valley region atmospheric inputs form an important source of some elements but the dominant chemical characteristics of the chalk groundwater are acquired during percolation through the soil and the upper unsaturated zone during saturated flow downgradient the chemistry is modified mainly by incongruent reactions of the carbonate matrix and by redox reactions and only to a minor extent by exchange reactions and mixing with residual saline connate water the incongruent reaction of carbonate results in a marked increase in the mg ca ratio and the sr and 13c contents of the groundwater with increased residence time oxygen concentrations are reduced mainly by oxidation of fe2 and the onset of reducing conditions allows dissolved fe2 to increase and rapid denitrification to occur the salinity profile through the confined chalk confirms that residual connate water up to one fifth sea water concentration still remains at depth and this accounts for some salinity increase in the confined groundwater resulting from fissure water pore water diffusional exchange timescales for groundwater movement have been established using tritium radiocarbon and indirectly using inert gas ratios and stable isotope ratios on balance it is concluded that all abstracted water is of holocene age although inert gas temperatures indicate cooler climatic conditions for recharge for some of the confined groundwater the implications for development and aquifer protection are discussed especially the prospect of natural in situ denitrification problems of fe solubility and the recognition of groundwater of different maturities

a tracer investigation into the importance of fissure flow in the unsaturated zone of the british upper chalk abstract the displacement and recovery of surface applied 15 no 3 2 h and cl in the unsaturated zone of the british upper chalk was followed over a 4 year period recovery of cl in the chalk matrix under the treated plot was equivalent to 110 of that applied that of 2 h was 57 in the treated plot lateral flow of 2 h was evident from cores taken outside the plot and if this is included together with 2 h estimated to have been lost by evapotranspiration the recovery approached 100 recovery of 15 no 3 was 100 1 year after tracer application falling to 9 4 after 4 years no evidence of denitrification was obtained from background no 3 cores and it was concluded that the shortfall in no 3 recovery was due to uptake by grass from depths of 50 70 cm the tracer profiles and recoveries were not consistent with significant vertical macrofissure flow but the lack of seasonal periodicity in background 2 h profiles suggested that some microfissure flow could be occurring the displacement of the tracer peaks when considered with the estimates of recharge indicated that only 50 of the water filled matrix was conducting flow

heterogeneous behaviour of unconfined chalk aquifers infer from combination of groundwater residence time hydrochemistry and hydrodynamic tools chalk groundwater is an important aquifer resource in france and also in much of northwestern europe large areas between the paris basin the london basin denmark and the northwest of germany as it is intensively exploited for human use with a large proportion reserved for drinking water the improvement of the knowledge on chalk aquifer hydrodynamical functioning and groundwater geochemistry is essential for the management of this resource to achieve this aim we developed a methodology based on a combination of hydrodynamic hydrochemistry and groundwater dating tools a study site of about 500 km2 was selected in ne france where chalk outcrops at 15 sampling points including boreholes and rivers mainly from chalk aquifer drainage groundwater geochemistry were monitored monthly for 2 years from june 2017 to june 2019 groundwater level in boreholes were monitored hourly with in situ water loggers in addition two sampling campaigns for the analysis of cfcs and sf6 have been conducted in boreholes in high and low water level periods to define the groundwater residence time the aquifer at the majority of sampling sites has an inertial behavior with respect to recharge as no impact of individual rainfall event was observed rapid piezometric response following rainfalls was observed at one site suggesting the presence of locally highly developed fracture network contrariwise high spatial and temporal heterogeneities of geochemistry was observed on the study area according to the mixing process piston flow exponential or binary mixing defined at each sampling site groundwater dating indicated rather heterogeneous ages ranging from less than 20 years to more than 50 years a combination of hydrogeological setting residence time and land use information was used to explain the hydrochemical heterogeneities highlighting the main factors governing the chalk groundwater geochemistry including water level fluctuation thickness of the unsaturated zone superficial formations distribution of fracture network aquifer river relations and human activities a conceptual model was proposed to clarify the hydrogeosystem functioning of unconfined chalk aquifers the proposed methodology can be used for the study of other worldwide aquifers chalk or not with the aim to provide appropriate recommendations in terms of water management

a first study of sf6 as a transient tracer in the southern ocean abstract halogenated transient tracers such as the chlorofluorocarbons cfc 11 cfc 12 and cfc 113 are commonly used in oceanographic studies these compounds enter the ocean via the atmosphere and their transient atmospheric concentrations make them valuable as oceanic tracers the trends of rapidly rising atmospheric concentrations of these tracers are however broken and the oceanic signal becomes increasingly more difficult to decipher there is a need for a new transient tracer to complement the existing suit of tracers especially for recently ventilated water masses one compound that looks promising in this respect is sulphur hexafluoride sf 6 an inert gas whose atmospheric concentration is rising rapidly in this paper the use of sf 6 as a transient tracer in recently ventilated waters is discussed and the method for determination of sf 6 in seawater is described tracer data from a section in the atlantic sector of the southern ocean along 6 e from 60 s to 40 s occupied during january 1998 are presented the antarctic polar front found close to 50 s was studied with a densely sampled section down to 400 m depth and sf 6 cfc 12 ratios are used to deduce ventilation ages and dilution factors a comparison of apparent ages derived from a variety of tracers is presented together with the uncertainties in these estimates this work demonstrates that sf 6 is a useful and valuable transient tracer for waters ventilated during the last 20 years

orinoco and amazon river sediment input to the eastern caribbean basin abstract carbonate and mineralogic analyses of piston cores from aves ridge eastern caribbean basin reveal climatically modulated relationship among quaternary carbonate deposition and terrigenous sediment influxes from the orinoco and amazon rivers low carbonate content and dark sediment color extending into the pleistocene suggest considerable dilution of pelagic components by terrigenous sediment on the western flank of aves ridge which is characterized by a southwest thickening sedimentary wedge contrary to typical trends observed in the more distal areas of the central basin west of aves ridge carbonate content is lowest during interglacial climates and highest during glacial climates a high clay mineral input correlates with interglacial climate however the orinoco tracer mineral pyrophyllite is low during interglacials and high during glacials the observed trends suggest that amazon sediment influx to the eastern caribbean is highest during interglacials or times of high sea level the amazon influx is promoted by deposition on the shelf and westward coastal transport of sediment during high sea level and reduced by shelf edge deposition and loss to the amazon canyon during low sea level the orinoco influx is similarly modulated but it undergoes a relative and possibly absolute increase during low sea level because of proximity to the depositional site the terrigenous dilution produces the reversal of carbonate trends however total sediment accumulation rates on southernmost aves ridge remain higher during glacials possibly as a result of increased carbonate production caused by upwelling

spatial heterogeneity of high resolution chalk groundwater geochemistry underground quarry at saint martin le noeud france chalk groundwater is an important aquifer resource in france because it accounts for a production of 12 million m3 y 1 with a large proportion reserved for drinking water processes occurring in the unsaturated zone uz and the overlying superficial formations have a high impact on chalk groundwater geochemistry and require better understanding the study site is a former underground chalk quarry located near beauvais france that extends over 1200 m in length at a depth ranging from 20 to 30 m the water table intersects the cavity creating 15 underground lake that give access to the chalk groundwater lakes geochemistry has been studied water samples were collected in july 2013 and major ion concentrations were analyzed uz and clay with flints thickness above each lake were estimated qualitatively using an electromagnetic sensor em31 and underground gps the results unexpectedly showed that groundwater quality varied widely in spatial terms for both allochthonous and autochthonous ions e g hco3 ranged from 2 03 to 4 43 meq l 1 no3 ranged from 0 21 to 1 33 meq l 1 principal component analysis indicated the impact of agricultural land use on water quality with the intake of no3 as well as so42 cl and ca2 chalk groundwater geochemistry is compared with the nature and structure of the uz we highlight correlations 1 between thick clay with flints layers and the ions mg2 and k and 2 between uz thickness and na in conclusion this paper identifies various ion sources agriculture clay with flints and chalk and demonstrates different processes in the uz dissolution ionic exchange and solute storage

advances in modelling groundwater behaviour in chalk catchments groundwater in chalk catchments is a major resource that also helps support internationally important habitats and ecosystems its dual porosity and dual permeability properties coupled with large scale structural features such as hard rock layers and marls produce a highly complex hydrogeological system recent impacts from groundwater flooding as well as vulnerability to drought have raised questions over the ability of traditional approaches to model these aquifers current work on near surface hydrological processes has highlighted the importance of the soil and weathered zone for controlling recharge rates in addition karst like features sedimentary deposits and valley bottom processes govern stream aquifer interaction and present a challenge in their representation in any modelling system methods that have and are being developed to incorporate these features and their use in modelling chalk catchments are described these are required in order to address major challenges such as groundwater flooding and drought impacts both of which could become more frequent and intense as a result of climate change

experimental investigation of solute transport in unsaturated fractured rock an experiment is designed to perform tracer tests in an unsaturated fractured rock with a horizontal fracture data from an intact and an artificial sandstone sample was collected and used to discuss the effect of the fracture on tracer migration the delay time of the tracer in the fracture was further determined in terms of the fracture aperture involved an alternative electrical conductivity or electrical resistance method was developed to measure the change in the tracer concentration with time and space the method causes no disturbance to the flow and concentration fields and is convenient to use the test results show the fluctuations in the tracer concentrations and there were 2 3 peak values of concentration in the monitored sections related to the heterogeneity of the water content and pore distribution also the fracture was found to delay migration of the tracer before it is filled with the tracer solution and quicken the velocity of migration afterwards this results in accumulation of the tracer near the fracture furthermore the delay time of the tracer increases with fracture aperture in a nonlinear manner

foreland basin structural growth recorded in the turonian ferron sandstone of the western interior seaway basin usa tectonic forcing of stratigraphic architecture is likely in foreland basins tectonic driving forces are increasingly being invoked to explain stratigraphic patterns in the cretaceous western interior seaway basin of north america yet the evidence is largely circumstantial and the details of driving forces remain elusive in this paper i show direct stratigraphic evidence for syndepositional growth of a structural arch with at least 50 m of relief during accumulation of the upper turonian ferron sandstone in south central utah united states progressive growth of the arch was superimposed on several high frequency stratal cycles that were driven by a more regionally extensive process geodynamic or eustatic and that produced laterally amalgamated sandstone bodies in a depositional strike parallel orientation north south all of this stratigraphy was then truncated by a more or less planar erosion surface sequence boundary that can be traced physically over at least 67 km north south this surface was later tilted northward such that the upper member of the ferron sandstone thins progressively southward from 50 to 10 m over 67 km the facies juxtapositions revealed by the ferron sandstone could if seen in exposure of limited lateral extent be wrongly interpreted as recording regionally extensive relative sea level drops and potentially used in error as evidence for substantial eustatic sea level falls during the turonian the folding and tilting documented in this study can be clearly attributed to geodynamic and or tectonic driving forces likely related to migration of a forebulge

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

dating groundwater with trifluoromethyl sulfurpentafluoride sf5cf3 sulfur hexafluoride sf6 cf3cl cfc 13 and cf2cl2 cfc 12 1 a new groundwater dating procedure using the transient atmospheric signal of the environmental tracers sf5cf3 cfc 13 sf6 and cfc 12 was developed the analytical procedure determines concentrations of the four tracers in air and water samples sf5cf3 and cfc 13 can be used to date groundwaters in some environments where the cfcs and sf6 have previously failed because these new tracers have increasing atmospheric input functions no known terrigenic source and are believed to be stable under reducing conditions sf5cf3 has a dating range from 1970 to modern the mixing ratio mole fraction in north american air has increased from the detection limit of 0 005 parts per trillion ppt to the 2006 mole fraction of about 0 16 ppt no evidence was found for degradation of sf5cf3 in laboratory anaerobic systems the solubility of sf5cf3 was measured in water from 1 to 35 c groundwater samples that contained large amounts of terrigenic sf6 did not contain terrigenic sf5cf3 cfc 13 is a trace atmospheric gas with a dating range in groundwater of about 1965 to modern cfc 13 has been used primarily in very low temperature refrigeration thus groundwater environments are less likely to be contaminated with nonatmospheric sources as compared to other widely used cfcs because of the low solubility of sf5cf3 and cfc 13 in water an excess air correction must be applied to the apparent ages the new dating procedure was tested in water samples from wells and springs from maryland virginia and west virginia

a depositional model for offshore deposits of the lower blue gate member mancos shale uinta basin utah usa depositional models that use heterogeneity in mud dominated successions to distinguish and diagnose environments within the offshore realm are still in their infancy despite significant recent advances in understanding the complex and dynamic processes of mud deposition six cored intervals of the main body of the mancos shale the lower blue gate member uinta basin were examined sedimentologically stratigraphically and geochemically in order to evaluate facies heterogeneity and depositional mechanisms unique sedimentological and geochemical features are used to identify three offshore environments of deposition the prodelta the mudbelt and the sediment starved shelf prodelta deposits consist of interlaminated siltstone and sandstone and exhibit variable and stressed trace fossil assemblages and indicators of high sedimentation rates the prodelta was dominated by river fed hyperpycnal flow mudbelt deposits consist of interlaminated siltstone and sandstone and are characterized by higher bioturbation indices and more diverse trace fossil assemblages ripples scours truncations and normally graded laminations are abundant in prodelta and mudbelt deposits indicating dynamic current conditions mudbelt sediment dispersal was achieved by both combined flow above storm wave base and current enhanced and wave enhanced sediment gravity flows below storm wave base sediment starved shelf deposits are dominantly siltstone to claystone with the highest calcite and organic content bioturbation is limited to absent sediment starved shelf deposits were the result of a combination of shelfal currents and hypopycnal settling of sediment despite representing the smallest volume sediment starved shelf deposits are the most prospective for shale hydrocarbon resource development due to elevated organic and carbonate content sediment starved shelf deposits are found in either retrogradational to aggradational parasequence sets or early distal aggradational to progradational parasequence sets bounding the maximum flooding surface an improved framework classification of offshore mudstone depositional processes based on diagnostic sedimentary criteria advances our predictive ability in complex and dynamic mud dominated environments and informs resource prospectivity

mechanisms of groundwater recharge and pesticide penetration to a chalk aquifer in southern england abstract in order to assess the potential for enhanced agrochemical contamination of shallow groundwaters a field study was established on the upper chalk in hampshire uk two instrumented sites 380 m apart were established on a hillslope one on the interfluve with a deep water table 18 m depth the other on the dry valley bottom where the groundwater was close to the surface 4 m depth hourly measurements of water potentials in the unsaturated zone to 3 0 m depth identified very different groundwater recharge processes between the two sites in response to the same storm event on the interfluve site with the deep water table only matrix flow through the chalk unsaturated zone at 3 m depth was identified in contrast at the dry valley bottom with a shallow water table both rapid preferential flow and matrix flow processes were observed at a 3 m depth the correlation between groundwater depth measurements and unsaturated profile moisture content measurements demonstrated the importance of the capillary fringe in sustaining a higher moisture content in the unsaturated zone at the shallow groundwater site the resulting reduced water storage capacity for vertical drainage fluxes meant that little water was required to wet the shallow profile before rapid preferential flow events demonstrated by rapid water potential responses occurred however where the groundwater was deeper intermediate storage sites located on chalk surfaces and at chalk ped block contact points remained empty and unsaturated water potential profiles showed that rainfall pulses were attenuated as these sites absorbed the downward water fluxes consequently preferential events at these deep groundwater sites are rare the importance of these intermediate storage sites in controlling recharge processes is highlighted the potential mass load of pesticide transported to the shallow groundwater in preferential events during 1996 7 was determined using bromide tracer studies water balance calculations and measured groundwater pesticide concentrations an estimated 0 1 of the applied pesticide reached the shallow groundwater along preferential pathways in 1996 7 calculations under a worst case scenario showed that this value did not increase beyond 0 2 of pesticide applied

the last big marine transgression of the western interior seaway almond formation development from barrier spits across south wyoming abstract the stratigraphic response to marine shoreline transgressions have been debated for the last six decades a particularly interesting aspect is that transgressive ravinement often removes evidence of the shoreline itself until there is turnaround to regression to elucidate this topic we present a high resolution chronostratigraphic study of an overall transgressive coastline documented with evidence from over 1450 wells covering an area of 6200 km2 to define the fundamental sandbodies and relevant stratigraphic surfaces the mapping of 15 elongate sandstone units stacked into 6 reservoirs shows that there was a spectacular westward rising of back stepping barrier spits sourced by long shore currents mobilizing sand from a delta to the north each fundamental barrier spit unit bsu is a 6 12 metres thick regressive southward elongate and narrowing sandbody generated by longshore drift of sandy sediment each barrier sand body and its related overlying transgression is estimated to represent some 20 ky strong transgressive ravinement events periodically flooded the barrier spits and shifted the deposition westward in four to 35 km steps westward transgressive stepping across and into a structurally generated embayment progressively dampened wave energy with each backstep morphologically there were two endmember sandbody types 1 narrow drum stick like sandbodies built mostly by longshore accretion i e true barrier bars and 2 broader and more extensive regressive belts of sandstone that resemble strandplains the former display typically longer backsteps across lagoonal areas whereas the latter show a more aggradational stacking arrangement which evidences a quasi balance between accommodation and sediment supply there is no evidence of a smooth and continuous transgression controlling sandstone deposition and preservation a hybrid punctuated transgression model that considers the alternation of long term coastal retrogradation and short lived barrier spit development by longshore accretion and seaward progradation is the most appropriate model for creating and preserving upper almond sandbodies

tetrafluoromethane in the deep north pacific ocean 1 dissolved tetrafluoromethane cf4 has been measured for the first time in the north pacific ocean surface water collected during calm weather is near equilibrium with the modern atmosphere deep water isolated from atmospheric exchange for centuries is near equilibrium with the preindustrial atmosphere after accounting for an expected 5 addition of this low solubility gas due to air injection during high latitude deep water formation these results strongly suggest that dissolved cf4 is conservative in seawater and that the oceanic imprint of anthropogenic increases in atmospheric cf4 can be used as a time dependent tracer of ocean ventilation and subsurface circulation processes although the continental lithosphere is a source of natural atmospheric cf4 we find no evidence of an oceanic lithospheric cf4 input into deep pacific waters the estimated upper limit of a potential oceanic lithospheric cf4 flux to the global atmosphere is on the order of 4 of that from the continental lithosphere

analysis of water level response to rainfall and implications for recharge pathways in the chalk aquifer se england summary water table response to rainfall was investigated at six sites in the upper middle and lower chalk of southern england daily time series of rainfall and borehole water level were cross correlated to investigate seasonal variations in groundwater level response times based on periods of 3 month duration the time lags in days yielding significant correlations were compared with the average unsaturated zone thickness during each 3 month period in general for cases when the unsaturated zone was greater than 18 m thick the time lag for a significant water level response increased rapidly once the depth to the water table exceeded a critical value which varied from site to site for shallower water tables a linear relationship between the depth to the water table and the water level response time was evident the observed variations in response time can only be partially accounted for using a diffusive model for propagation through the unsaturated matrix suggesting that some fissure flow was occurring the majority of rapid responses were observed during the winter spring recharge period when the unsaturated zone is thinnest and the unsaturated zone moisture content is highest and were more likely to occur when the rainfall intensity exceeded 5 mm day at some sites a very rapid response within 24 h of rainfall was observed in addition to the longer term responses even when the unsaturated zone was up to 64 m thick this response was generally associated with the autumn period the results of the cross correlation analysis provide statistical support for the presence of fissure flow and for the contribution of multiple pathways through the unsaturated zone to groundwater recharge

modelling the baseline geochemistry of groundwater in a chalk aquifer considering solid solutions for carbonate phases the chalk aquifer of champagne france baseline geochemistry has been determined using a solid solution approach for the modelling of calcite dissolution the water rock interactions are modelled by the speciation code chess from field data and ca mg and sr aqueous concentrations in groundwater the stoichiometries of solid solutions are defined in each stratigraphic unit of the chalk aquifer from bulk geochemistry and chalk mineralogy of samples taken from boreholes the initial mineralisation of water at the bottom of the unsaturated zone and the characterisation of the theoretical evolution of groundwater chemistry along the flow lines associated with incongruent calcite dissolution are calculated from this approach

recharge of the upper chalk aquifer at a site in hampshire england 1 water balance and unsaturated flow abstract measurements of the annual cycle of changes in water content and potential in the 40 m thick unsaturated zone of upper chalk at a site in southern england are described measured evaporation continued at the penman potential rate until the soil moisture deficit reached 175 mm this suggested that a root constant of 200 mm would be more appropriate than the much lower values generally used the field capacity concept could not be reconciled with the timing of renewed water recharge and the reasons for this are discussed the mechanisms of water flow through the unsaturated zone of the chalk are examined and it is shown that at this upper chalk site matrix flow is the dominant recharge mechanism

eifelian givetian middle devonian high paleolatitude storm and wave dominated shallow marine depositional systems from the bidouw subgroup bokkeveld group of south africa abstract the sedimentology of the eifelian givetian middle devonian bidouw subgroup in the clanwilliam sub basin of south africa has been reassessed four distinct lithofacies associations are recognized a d and are representative of the deposits of offshore os offshore transition zone to distal lower shoreface otz dlsf proximal lower shoreface plsf and upper shoreface beach usf beach paleoenvironments these paleoenvironments are arranged as several t r controlled storm and wave dominated shallow marine depositional systems the presence of storm and wave dominated shallow marine depositional systems in the bidouw subgroup as well as the preceding emsian eifelian early middle devonian ceres subgroup provides an alternative explanation to storm and wave dominated delta and mixed wave and tide dominated delta models that have previously been proposed for the bokkeveld group sequence stratigraphic analysis of the bidouw subgroup suggests that although sedimentation occurred during two large scale second order transgressive events the succession was predominantly regressive third order and fourth order transgressive regressive t r sequences are more numerous with respect to the preceding ceres subgroup suggesting that the driver for t r cyclicity and relative sea level change was more active during the eifelian givetian than in the emsian eifelian of south africa these data are important since relative sea level change and its effects on paleoenvironmental change at high paleolatitudes during the devonian period are poorly known

composition of clays along the continental shelf off israel contribution of the nile versus local sources the eastern mediterranean sedimentary regime is dominated by sediment transport from the nile river and its delta but recent studies have also suggested a certain contribution of clay fraction from streams to the continental shelf and slope off israel in the present study we focused on clay fraction deposition along the inner 40 1000 m water depth shelf of israel in order to substantiate and quantify its different sources for this purpose detailed xrd mineralogical determinations as well as chemical compositions of the clay 2 m fraction of marine and continental sediments were used the clay mineral composition of israeli stream sediments is variable with no distinct spatial or temporal trend but within a limited assemblage this clay assemblage is made up of illite smectite is phases 70 90 kaolinite 5 25 and illite 10 and is similar to that of the nile however it is clearly distinguished by the type of the is phases which are derived mainly from mesozoic outcrops and recent sediments soils and are less expandable than those of the nile which are derived mainly from weathered basalt the nile derived component is depleted in the marine clay fraction along the israel coast evidenced by a decrease of is expandability and the fe2o3 al2o3 ratio and an increase in the k2o al2o3 mgo al2o3 and cao al2o3 ratios the depletion is well pronounced north of tel aviv where the largest coastal plain stream flows to the sea a northward increase of carbonates in the clay fraction and particularly of the bioskeletal component is indicated by the ratios of mgo and sr to cao the contribution of the local streams to the shallow shelf marine clay fraction is estimated to be about 50 a minor contribution of desert dust is identified by the relative increase in kaolinite in the marine sediments south of tel aviv

residence time of chalk groundwaters in the paris basin and the north german basin a geochemical approach the comparative geochemical and isotopic study of confined and unconfined chalk groundwaters of the paris basin and the n german basin proves a significant chemical evolution during groundwater flow from the recharge zones to the deep confined aquifer different time dependent geochemical parameters have been tested as dating tools cation ratios sr2 ca2 mg2 ca2 n no 3 noble gas contents as paleotemperature indicators ne ar kr xe radiogenic he 13c 14c 18o 2h 3h cation ratios and 13c show the importance of incongruent dissolution processes in the chalk aquifer water rock interactions were taken into account in a multi step dissolution model to determine radiocarbon groundwater ages the oldest waters in the confined part of the paris basin chalk with maximum 14c ages of 14 000 a b p contain pleistocene recharge components as can be shown by a stable isotope depletion and noble gas temperatures significantly lower than in recent groundwaters chalk waters at the lagerdorf site in northern germany show a distinct stratification with respect to residence times and hydrochemistry

on the geological significance of clastic parasequences abstract parasequences recognized in clastic sedimentary successions of shallow marine origin are considered by some geologists to be the fundamental building blocks of depositional sequences even though problems in their definition and application have been identified by others who instead advocate their abandonment as formal sequence stratigraphic units to elucidate the geological significance of clastic parasequences and inform the debate on their use in stratigraphy a quantitative characterization of the geometry facies characteristics and timescale of deposition of 1163 parasequences has been undertaken based on a synthesis of data from outcrop and subsurface studies that are available in the scientific literature through a database compilation the attributes of the studied parasequences are analysed with respect to the interpreted geological origin of the units and with consideration of sources of bias and uncertainty particular emphasis is placed on assessing the following i the importance of heuristics and of data types and coverage in the recognition of parasequences ii differences in parasequence characteristics observed across deltaic and shoreface depositional systems and between the quaternary and the ancient rock record iii possible explanations for the range in timescales of deposition of parasequences and iv the role of autogenic dynamics on the development of deltaic parasequences partly based on a comparison with the recent evolution of modern deltas the results demonstrate that parasequence definition and physical correlation suffer from subjectivity and that significant variability exists in the spatio temporal and architectural attributes of clastic parasequences this gives rise to uncertainty that affects the use of parasequences as a framework for comparison of the architecture of packages of strata originating via shoreline regression this uncertainty must be considered when using analogue data for subsurface predictions or when attempting comparative studies of clastic successions

the significance of flow in the matrix of the chalk unsaturated zone the significance of flow in the matrix of the chalk unsaturated zone in comparison with flow in fractures has been the subject of much debate in this article important elements of the literature are discussed in detail and several simple modelling analyses based on steady state flow are presented a study of the sensitivity of solute spreading to fracture spacing in models that ignore matrix flow shows that this latter assumption is generally incompatible with observed solute profiles unless unrealistically small fracture spacings are assumed the effect of air phase continuities e g bedding planes on matrix flow has also been examined these discontinuities are frequently interrupted by points of connectivity between matrix blocks an issue therefore is the relationship between connectivity and its effect on inter block conductance a simple analysis of the laplace equation shows that just 1 connectivity represents an effective pathway equivalent to 18 of the local rock hydraulic conductivity obviously when there is no fracture flow solute spreading is significantly reduced however dual permeability model simulations show that matrix flow reduces solute spreading in the presence of persistent fracture flow all of the above studies suggest that flow in the matrix of the chalk unsaturated zone is significant and that ignoring it may result in a serious misunderstanding of the system

clay mineral distribution in surface sediments of the south atlantic sources transport and relation to oceanography abstract surface samples mostly from abyssal sediments of the south atlantic from parts of the equatorial atlantic and of the antarctic ocean were investigated for clay content and clay mineral composition maps of relative clay mineral content were compiled which improve previous maps by showing more details especially at high latitudes large scale relations regarding the origin and transport paths of detrital clay are revealed high smectite concentrations are observed in abyssal regions primarily derived from southernmost south america and from minor sources in southwest africa near submarine volcanoes of the antarctic ocean south sandwich bouvet island smectite contents exhibit distinct maxima which is ascribed to the weathering of altered basalts and volcanic glasses the illite distribution can be subdivided into five major zones including two maxima revealing both south african and antarctic sources a particularly high amount of mg and fe rich illites are observed close to east antarctica they are derived from biotite bearing crystalline rocks and transported to the west by the east antarctic coastal current chiorite and well crystallized dioctaedral illite are typical minerals enriched within the subantarctic and polarfrontal zone but of minor importance off east antarctica kaolinite dominates the clay mineral assemblage at low latitudes where the continental source rocks west africa brazil are mainly affected by intensive chemical weathering surprisingly a slight increase of kaolinite is observed in the enderby basin and near the filchner ronne ice shelf the investigated area can be subdivided into ten large scale clay facies zones with characteristic possible source regions and transport paths clay mineral assemblages of the largest part of the south atlantic especially of the western basins are dominated by chlorite and illite derived from the antarctic peninsula and southernmost south america and supported by advection within the circumantarctic deep water flow in contrast the east antarctic provinces are relatively small assemblages of the eastern basins north of 30 s are strongly influenced by african sources controlled by weathering regimes on land and by a complex interaction of wind river and deep ocean transport the strong gradient in clay mineral composition at the brazilian slope indicate a relatively low contribution of tropically derived assemblages to the western basins

infiltration processes in karstic chalk investigated through a spatial analysis of the geochemical properties of the groundwater the effect of the superficial layer of clay with flints summary in the paris basin in upper normandy france the chalk plateaus are covered with thick deposits of loess and clay with flints from a few meters to approximately 40 m thick locally a perched groundwater is sometimes observed in the superficial layers in which evapotranspiration processes seem to occur this study s objective was to understand the effects of the thick clay with flints layers on the infiltration processes to achieve this we adopted a spatial approach comparing the maps of the geochemical properties of the chalk groundwater and the maps of the thickness of clay with flints the french national groundwater database ades acces aux donnees des eaux brgm provided the mean geochemical properties in the chalk aquifer of upper normandy this database was used to prepare maps of the environmental tracers ca 2 hco 3 mg 2 cl na no 3 and so 4 2 the data are spatially well organized using principal component analysis pca these maps were compared with the maps of the thickness of clay with flints a focus on the coastal basins northern upper normandy shows a very strong spatial correlation between the maps of clay with flints thickness and all of the maps of the major ions the thickness of clay with flints is negatively correlated with the autochthonous ions hco 3 and ca 2 and is positively correlated with the allochthonous ions cl na so 4 2 and no 3 these results highlight that the thickness of clay with flints controls recharge two types of infiltration processes are proposed 1 thicker clay with flints allows storage in the perched groundwater which allows evapotranspiration resulting in high concentrations of allochthonous ions and a decrease in the dissolution potential of water and low concentrations of autochthonous ions the infiltration of the perched groundwater is thus delayed and concentrated 2 thinner clay with flints causes the infiltration to be more diffuse with low evapotranspiration and thus low concentrations of allochthonous ions in the chalk groundwater more there is more dissolution and higher concentrations of autochthonous ions in the chalk groundwater

deep water renewal in lake issyk kul 1 the deep water renewal rates of lake issyk kul are studied using the time dependent anthropogenically produced tracers sulfur hexafluoride sf 6 chlorofluorocarbons cfcs and tritium helium 3 sf 6 and the cfcs are used to calibrate a mixing model from which the vertical age distribution is calculated and found to be comparable to the sf 6 apparent ages based on this model the mean age of the water below 100 m depth is 6 1 yrs the mean oxygen consumption rate for the same depth range is 6 4 mol kg 1 yr 1 and the mean remineralization rates for nitrate phosphate and silicate are 0 53 0 003 and 0 67 mol kg 1 yr 1 respectively

mechanisms of water storage and flow in the unsaturated zone of the chalk aquifer abstract it is known that the volumes of water draining from some chalk catchments in recessions are significantly greater than can be explained by gravity drainage from fissure porosity the most likely source of this water is slow drainage from the matric porosity above the water table this paper suggests that the location of this storage is in the irregularities on the fissure surfaces studies of resin impregnated blocks of chalk failed to reveal the presence of hydrologically significant microfissures or macropores that could be the source of additional drainage ultrasonic measurements at varying values of effective stress show no indication of changes in the acoustic transmission properties that could be attributed to closure of microfissures drainage and mercury intrusion measurements indicate that there is significant storage on block surfaces the drainage measurements confirm that the storage is of the order of magnitude about 0 3 needed to explain the slow drainage this additional storage explains why the water table is slow to respond after recharge events and why the chalk is resilient to drought the presence of storage in the unsaturated zone implies that the position of the water table may not be an accurate indicator of groundwater resources the concept of filling and draining of irregularities on fissure surfaces also leads to a new model for the generation of fissure flow in the unsaturated zone of the chalk this suggests that fissure flow can be generated at any depth in the profile and in a sequence of uniform vertical permeability is likely to originate near the water table rather than high in the unsaturated zone

evaluating an unconfined aquifer by analysis of age dating tracers in stream water the mean transit time mtt is a fundamental property of a groundwater flow system that is strongly related to the ratio of recharge rate to storage volume however obtaining samples for estimating the mtt using environmental tracers is problematic as flow weighted samples over the full spectrum of transit times are needed samples collected from the base flow of a gaining stream in the north carolina coastal plain west bear creek that were corrected for exchange with the atmosphere yielded environmental tracer concentrations sf6 and cfc 11 very similar to flow weighted values from nine or ten streambed piezometers that directly sampled groundwater during low streamflow at higher streamflow on the falling limb of the hydrograph stream tracer concentrations after correction for gas exchange were significantly higher than the flow weighted mean from piezometers consistent with dominance of the stream tracer signal by transient influx of surface water and or younger subsurface water the apparent mtt derived from sf6 in low flow stream water samples was 26 years suggesting a groundwater recharge rate of about 210 mm yr that is consistent with vertical profiles obtained by sampling nested piezometers in the aquifer when sampled under low flow conditions when streamflow consists of a high component of groundwater discharge west bear creek appears to act as a flow weighted integrator of transit times and streamflow samples can provide fundamental information regarding groundwater recharge rate and mtt our study suggests that watershed scale evaluation of some groundwater flow systems is possible without utilizing monitoring wells

evidence for rapid groundwater flow and karst type behaviour in the chalk of southern england with the growing importance of groundwater protection there is increasing concern about the possibility of rapid groundwater flow in the chalk of southern england and therefore in the frequency and distribution of karstic features pumping test data although useful in quantifying groundwater resources and regional flow give little information on groundwater flow at a local scale evidence for rapid groundwater flow is gathered from other less quantifiable methods nine different strands of evidence are drawn together tracer tests observations from chalk caves chalk boreholes that pump sand descriptions of adits the nature of water level fluctuations the chichester flood the nature of the surface drainage geomorphological features and the presence of indicator bacteria in chalk boreholes although the evidence does not prove the widespread existence of karstic features it does suggest that rapid groundwater flow should be considered seriously throughout the chalk rapid groundwater flow is generally more frequent close to palaeogene cover and may also be associated with other forms of cover and valley bottoms

geochemistry and mineralogy of the nw aegean sea surface sediments implications for river runoff and anthropogenic impact abstract surface sediments of the nw aegean sea were analyzed for clay mineral composition 94 samples organic c and carbonate content and major and minor elements 112 samples illite is the most abundant clay mineral followed by smectite chlorite and kaolinite clay minerals are preferentially deposited within the continental shelf and slope environment due to the prevailing cyclonic circulation and the formation of flocs in the rivers pro delta areas the spatial distribution of major lithogenic elements si al ti fe is substantially biased by the presence of relict sands located in the central eastern part of the thermaikos gulf continental shelf biogenic elements ca sr are noticeably pronounced on the northern flank of the north sporades islands organic c content and minor elements cu zn as and pb are enriched markedly over the thessaloniki bay and gulf suggesting substantial human impact deriving largely from untreated or partly treated domestic and industrial effluents the terrigenous component of the elements is preferentially contributed from the axios river zn and pb the aliakmon river cr co ni cu and as and to a lesser extent from the pinios river v co ni and cu a considerable part of the metals originates in ultra mafic and volcanic formations which are abundant in the rivers catchment basins carbonate content exhibits great variability with the highest values observed in biogenic sediments of the sporades basin in the latter area mn and fe oxides and hydroxides were found as coatings on calcite the coatings were enriched in cr co ni zn as mo and pb due to adsorption or ion exchange during early diagenesis the combined influence of the river systems the thessaloniki metropolis and the diverse sedimentological background generates great patchiness in the distribution of major and minor elements

geochemical and mineralogical variations in the upper mercia mudstone group late triassic southwest britain correlation of outcrop sequences with borehole geophysical logs the mercia mudstone group comprises up to 1200m of predominantly red mudstones and siltstones laid down in rift related basins during a period of regional subsidence the mudstones are commonly dolomitic and contain horizons of sulphate and halide salts up to 150m of undifferentiated red mudstones of norian and rhaetian age late triassic were examined in coastal outcrops in devon and somerset southwest britain and mineralogical and stable isotopic studies were carried out in order to identify any subtle changes in the succession gamma ray measurements were taken at outcrop to provide correlation with published borehole logs in which the mercia mudstone group has been subdivided on the basis of gamma ray and sonic response one of the borehole subdivisions was identified at outcrop within a sequence of otherwise undifferentiated red mudstones and was related to a transition in clay mineral assemblage and stable isotopic composition over 20 to 30 m of section the red mudstones below this transition have a higher proportion of magnesian clay minerals and enriched carbonate oxygen isotope compositions indicating deposition from mg 2 rich marine derived waters clay mineral assemblages in the succeeding red mudstones are dominated by illite and oxygen isotopic compositions are relatively depleted indicating a greater influence of k rich continental derived waters

natural fluorinated organics in fluorite and rocks results of measurements of fluorinated compounds in gasses extracted from igneous and metamorphic rocks are reported a new extraction method analogous to a pepper mill for geological samples is described it permits extraction at low temperatures and ensures a rapid transfer of extracted gases from active surfaces to cryogenic pre concentration loop values for cf4 cf3cl cf2cl2 cfcl3 chf3 sf6 and nf3 in fluorites granites basalts and other igneous and metamorphic rocks are reported it is proposed that trifluoroacetic acid tfa that was recently discovered in various environmental archives could also origin from similar geogenic sources

evidence for a shallow highly permeable zone in the chalk of hampshire u k abstract studies of the chalk in the u k in the last 10 15 years have shown that it is generally the top 20 50 m below the water table which provides most of the aquifer yield an investigation in hampshire in connection with a river augmentation scheme using seasonal groundwater abstraction shows the chalk in the area to have a particularly thin and well developed 6 m thick zone possessing both high transmissivity and storativity evidence is put forward to support its existence

processes of water movement through a chalk coombe deposit in southeast england the processes of water movement through the coombe deposit in a chalk dry valley near eastbourne in southeast england were investigated using simple methods based on regular weekly measurements of rainfall soil water content and soil water potential the drainage flux recharge through the soil was determined using the water balance method during the winter and the zero flux plane zfp method after the appearance of the zfp in the spring the unsaturated hydraulic conductivity was derived applying darcy s law in a novel way using the measured potential gradients and weekly drainage fluxes the derived conductivity characteristics were adequate to identify the flow mechanisms to illustrate the difference in behaviour between the horizons of the soil profile and to give some indication of pore water velocities the mean daily drainage flux at 2 85 m depth during the recharge period from 10 october 1980 to 29 may 1981 was 1 6 mm d 1 weekly mean rates of up to 3 7 mm d 1 were observed but peak short term rates must have considerably exceeded this figure it was shown that in the lower part of the coombe deposit when drainage fluxes are large much of the flux passes through a very small proportion of the wetted cross sectional area of the soil this gives rise to pore water velocities of at least 3 m d 1 at a depth of 2 85 m and 0 5 m d 1 between 0 5 m and 2 5 m depth these results show that pollutants may be moved very rapidly through the profile in this and similar material the core sampling techniques normally used to monitor pollutant movement in the chalk are unlikely to succeed in detecting this movement not only because it is transient but also because it occupies only a very small proportion of the water filled pores

sedimentation and environmental conditions in the inner skagerrak outer oslofjord abstract sedimentological mineralogical geochemical and some geotechnical properties of holocene clay and silt sediments of the inner skagerrak and outer oslofjord are reported close to the norwegian coast the sea bottom has an irregular relief reflecting the rough features of the crystalline basement here the sediment thickness varies from 0 to 50 m at water depths greater than 150 m the sediment layer becomes thicker and continuous generally the sedimentation rates in the oslofjord and inner skagerrak are high normally 1 2 mm yr areas with higher deposition as well as with non deposition and or erosion occur the inner fjord sediments have high contents of illite and chlorite reflecting that they have been derived from the glacial deposits of scandinavia these clay minerals are also present in the outer fjord and skagerrak sediments which in addition contain smectite and kaolinite that originate from the mesozoic and cenozoic sediments in denmark southern sweden and or from sediments within the north sea basin these clay minerals are transported to the inner skagerrak mainly by the jutland and baltic currents the diagenetic zonation of most bottom sediments consists of an oxic layer on top of an incipient reducing anoxic non sulphidic layer in the oxic top layer of the skagerrak sediments diagnetic calcite grows on foraminiferal tests at depth the calcite dissolves zinc has been used as element reflecting anthropogenic pollution the flux of zinc to the oslofjord skagerrak sediments started to increase about 120 140 years ago today the most polluted waters are locked fjords and coastal waters inside the archipelago as the isostatic rebound still goes on in scandinavia the polluted sediment particles will not deposit in the river but in the fjord and coastal areas except for a few near shore areas and restricted fjord basins the degree of pollution is low

unsaturated flow and solute transport through the chalk tracer test and dual permeability modelling a tracer test was carried out in the unsaturated chalk at the fleam dyke research site in cambridgeshire uk to investigate the role of the chalk fractures and matrix in unsaturated flow and solute transport the experiment under natural rainfall conditions involved distributing deuterated water on a grass covered lysimeter a cube of volume 125 m3 and on an adjacent 4 m 4 m field plot tracer migration was monitored through regular core sampling and collection of lysimeter drainage water the presence of occasional secondary peaks in sampling of the vertical tracer profile suggested the occurrence of fracture flow allowing some tracer to bypass the chalk matrix however in the 15 months following application none of the tracer was detected in the lysimeter drainage at 5 m depth modelling of the tracer results was undertaken with the 1 d numerical transient dual permeability model macro 5 0 initially developed for macroporous soils modelling results showed that macro 5 0 could reliably simulate transient recharge through the chalk the simulations suggested that fracture flow is important at the site but that it is only initiated at 1 m depth or deeper the extent of fracture flow appeared to be highly variable in different layers of the profile varying between 40 and 85 of the cumulative flux mainly depending on the saturated hydraulic conductivity of the matrix diffusion between the fractures and the matrix tended to equalize solute concentrations in both flow domains although solute bypass through the fractures occurred in some chalk strata besides diffusive exchange the modelling stressed the importance of advective exchange of solutes the results suggest that the chalk aquifer at the fleam dyke site is only moderately vulnerable to pollution even though for moderate rainfall conditions some bypass flow was possible

transient simulations of flow and transport in the chalk unsaturated zone chalk is a fractured porous medium composed of matrix blocks bounded by interconnected fractures furthermore there are a number of commonly observed and apparently contradictory phenomena these include a fast water table response slow solute migration and very little solute dispersion to the authors knowledge no unified physically based numerical model has been able to reconcile all of these points in this paper these issues were addressed through the development of a transient dual permeability model of flow and transport the behaviour of the model was explored through a hypothetical scenario the one dimensional model featured a fixed water table at 10 m depth a recharge time series derived using the penman grindley model in conjunction with daily precipitation and monthly potential evaporation data from the kennet valley berkshire was applied at the top of the model a conservative solute that could be tritium chloride or nitrate was applied to the recharge for 1 year subsequent years involved the input of clean water the simulations suggested that although transient effects have been previously neglected overlying soil and gravelly chalk layers are likely to cause significant attenuating effects on flow such that most flow occurs through the matrix fracture flow was found to be episodic and infrequent and represented between 17 and 30 of the annual recharge

the importance of sea level fluctuations in the formation of linear conglomerate bodies carrot creek member of cardium formation cretaceous western interior seaway alberta canada abstract the raven river member of the cardium formation turonian upper cretaceous in the carrot creek area of alberta contains two coarsening upward sequences of marine mudstones and sandstones the lower sequence coarsens from black mudstones into bioturbated fine grained sandstones and is capped by a gritty siderite horizon which probably indicates a pause in deposition the sandstones of the upper sequence contain hummocky cross stratification suggesting open marine deposition below fairweather wave base the two sequences are scoured to variable depths by a major erosion surface which has a relative relief of up to 20 m a structure map and three dimensional mesh diagrams of this surface suggest four topographic elements a relatively high terrace a bevel at which und rlying beds are truncated and a series of bumps and hollows these are interpreted to represent a remnant erosional topography which gradually fades away into the final topographic element the smooth basin plain the erosion surface is covered with conglomerate assigned to the carrot creek member of the cardium the conglomerate thickness reaches about 20 m against the bevel and in some of the hollows but usually thins to a veneer on the terrace on top of the bumps and on the distal basin floor the conglomerate bodies are relatively long and narrow and trend northwest southeast they are overlain by marine mudstones of the dismal rat member the elongate conglomerate bodies appear at first sight to be another case of western interior seaway offshore bars encased in marine mudstones many tens of kilometers seaward of time equivalent shoreline deposits however the erosion surface indicates that the conglomerates are not genetically part of the underlying coarsening upward sequence we propose a rapid relative lowering of sea level following deposition of the hummocky cross stratified sandstones the shoreline advanced many kilometers northeastward into the basin and during stillstand wave erosion cut a new shoreface profile the bevel during this lowstand incised rivers supplied gravel to the shoreface waves worked the gravel alongshore against the bevel and into the erosional hollows subsequent transgres ion spread some gravel southwestward back across the terrace storms transported gravel stringers into the transgressive muds accumulating in the hollows other erosional surfaces of this type exist in alberta at the cardium viking and bad heart horizons and in new mexico at the gallup tocito horizon suggesting that sea level changes and shoreface incision may be an alternative explanation for other long narrow offshore bars encased in marine shales

high resolution sequence stratigraphy and implications for cretaceous glacioeustasy of the late cretaceous gallup system new mexico u s a

integrating 40ar 39ar u pb and astronomical clocks in the cretaceous niobrara formation western interior basin usa this study revises and improves the chronostratigraphic framework for late turonian through early campanian time based on work in the western interior u s and introduces new methods to better quantify uncertainties associated with the development of such time scales building on the unique attributes of the western interior basin which contains abundant volcanic ash beds and rhythmic strata interpreted to record orbital cycles we integrate new radioisotopic data of improved accuracy with a recently published astrochronologic framework for the niobrara formation new 40ar 39ar laser fusion ages corresponding to eight different ammonite biozones are determined by analysis of legacy samples as well as newly collected material these results are complemented by new u pb zircon chemical abrasion isotope dilution thermal ionization mass spectrometry ages from four biozones in the study interval when combined with published radioisotopic data from the cenomanian turonian boundary paired 206pb 238u and 40ar 39ar ages spanning cenomanian to campanian time support an astronomically calibrated fish canyon sanidine standard age of 28 201 ma stage boundary ages are estimated via integration of new radioisotopic data with the floating astrochronology for the niobrara formation the ages are determined by anchoring the long eccentricity bandpass from spectral analysis of the niobrara formation to radioisotopic ages with the lowest uncertainty proximal to the boundary and adding or subtracting time by parsing the 405 k y cycles the new stage boundary age determinations are 89 75 0 38 ma for the turonian coniacian 86 49 0 44 ma for the coniacian santonian and 84 19 0 38 ma for the santonian campanian boundary the 2 uncertainties for these estimates include systematic contributions from the radioisotopic measurements astrochronologic methods and geologic uncertainties related to stratigraphic correlation and the presence of hiatuses the latter geologic uncertainties have not been directly addressed in prior time scale studies and their determination was made possible by critical biostratigraphic observations each methodological approach employed in this study new radioisotopic analysis stratigraphic correlation astrochronology and ammonite and inoceramid biostratigraphy was critical for achieving the final result

tracking selenium in the chalk aquifer of northern france sr isotope constraints groundwater at the southern and eastern edges of france s paris basin has a selenium content that at times exceeds the european framework directive s drinking water limit value of 10 g l to better understand the dynamics of the chalk groundwater being tapped to supply the city of lille and the se origins we used a combination of geochemical and isotopic tools strontium isotopes coupled with ca sr mg sr and se sr ratios were used to identify the main groundwater bodies and their mixings with the mg sr ratio constraining a ternary system groundwater in the agricultural aquifer recharge zone represents a first end member and displays the youngest water ages of the catchment along with the highest strontium isotopic signature 0 7084 and low se contents anaerobic groundwater constitutes a second major end member affected by water rock interactions over a long residence time with the lowest strontium isotopic signature 0 7079 and the lowest se content its low sf6 content confirming the contribution of old water se rich groundwater containing up to 30 g l of se represents a third major end member with an intermediate sr isotopic ratio and is mainly constrained by the clayey se rich formation overlying the chalk aquifer the spatial and temporal se variability in the groundwater is clearly linked to the presence of this formation identified as tertiary and also to the hydrological conditions saturation of the se rich clays by oxygenated groundwater enhances se mobility and also sr adsorption onto the clays this multi tool study including sr isotopes successfully identified the se origins in the aquifer and has led to a better understanding of the regional mixing and processes affecting the chalk groundwater

tectonic activity as a significant source of crustal tetrafluoromethane emissions to the atmosphere observations in groundwaters along the san andreas fault abstract tetrafluoromethane cf 4 concentrations were measured in 14 groundwater samples from the cuyama valley mil potrero and cuddy valley aquifers along the big bend section of the san andreas fault system safs in california to assess whether tectonic activity in this region is a significant source of crustal cf 4 to the atmosphere dissolved cf 4 concentrations in all groundwater samples but one were elevated with respect to estimated recharge concentrations including entrainment of excess air during recharge c r e 30 fmol kg 1 h 2 o indicating subsurface addition of cf 4 to these groundwaters groundwaters in the cuyama valley contain small cf 4 excesses 0 1 9 times c r e which may be attributed to an in situ release from weathering and a minor addition of deep crustal cf 4 introduced to the shallow groundwater through nearby faults cf 4 excesses in groundwaters within 200 m of the safs are larger 10 980 times c r e and indicate the presence of a deep crustal flux of cf 4 that is likely associated with the physical alteration of silicate minerals in the shear zone of the safs extrapolating cf 4 flux rates observed in this study to the full extent of the safs 1300 km 20 100 km suggests that the safs potentially emits 0 3 1 10 1 kg cf 4 yr 1 to the earth s surface for comparison the chemical weathering of 7 5 10 4 km 2 of granitic rock in california is estimated to release 0 019 3 2 10 1 kg cf 4 yr 1 tectonic activity is likely an important and potentially the dominant driver of natural emissions of cf 4 to the atmosphere variations in preindustrial atmospheric cf 4 as observed in paleo archives such as ice cores may therefore represent changes in both continental weathering and tectonic activity including changes driven by variations in continental ice cover during glacial interglacial transitions

hydrological processes in the chalk unsaturated zone insights from an intensive field monitoring programme as part of the nerc lowland catchment research programme locar the pang lambourn catchments berkshire uk have been extensively instrumented to provide an improved understanding of the hydrological processes in the unsaturated zone of the chalk a subject of much debate over the past 30 years to quantify the movement of water through the unsaturated zone it is necessary to measure matric potential and water content as well as input and output fluxes from precipitation evapotranspiration and groundwater recharge previous studies have indicated the need for fine temporal resolution data to monitor this system effectively due to the challenges faced in meeting this objective a monitoring scheme was designed that combines a variety of instrumentation to provide the required range accuracy and spatial and temporal resolution of data this paper firstly presents an overview of the monitoring programme and a critical discussion of the instrumentation used subsequently the field data are used to characterise the hydrological properties of the unsaturated zone and to gain insight into recharge processes the interpretation of the data presented in this paper indicate that in the chalk unsaturated zone at west ilsley matrix flow is the dominant recharge mechanism

the geochemistry and mineralogy of marine sediments from the eastern indian ocean abstract chemical mineralogical and smear slide analyses of marine sediments from the eastern indian ocean have revealed at least eight sediment groups in the region the bay of bengal contains sediments derived from the himalayan range indian subcontinent sri lanka and west burma sediments from the indian subcontinent are carried south passing the eastern abyssal plain of sri lanka and then turn west this sediment path can be identified by a1 fe and smectite distributions the principal sediment source to the andaman sea is the irrawaddy river in the central indian and wharton basins hydrogenous sediments contain additional material slumped from java and sumatra and wind blown from western australia