twenty years of groundwater evolution in the triassic sandstone aquifer of lorraine impacts on baseline water quality abstract the lorraine triassic sandstone aquifer ltsa which has already been the subject of a chemical and radioisotopic study 1979 is used to investigate the impacts of 20 a of large scale pumping on baseline water quality in parallel new sampling of the aquifer 2001 provides new inorganic geochemical data including trace elements that allow improving the knowledge of baseline conditions and hydrochemical functioning of a major sandstone aquifer the good correlation between 14 c activities temperature and depth along the main flow line indicate regular downgradient trends and possible water stratification unreactive tracers mainly stable isotope ratios 18 o and 2 h as well as c isotopes are used to define a timescale for the aquifer showing two groups of groundwater namely of modern and holocene age and late pleistocene age with a mixing zone baseline quality is then represented by a wide range of concentrations mainly the result of time dependent water rock interaction as already observed elsewhere in triassic sandstone aquifers some trace elements such as li rb cs which are not limited by solubility constraints show linear trends during saturated flow downgradient the chemistry is also specifically characterised by a regular increase in na and cl and locally so 4 as a result of evaporite dissolution related to overlying or basement limits the aquifer is mostly oxidising with a redox boundary marked by u decrease some 40 km from outcrop groundwater abstraction since the 1970s has created a strong lowering 10 150 m of the water table especially from 1970 to 1980 based on nine boreholes previously sampled in 1979 a decreasing evolution in radiocarbon content of the tdic together with significant evolution of 18 o content indicate that old groundwater has moved upgradient the major difference in terms of baseline evolution is observed using cl and na concentration and locally so 4 indicating an increasing influence of water circulation involving overlying or basement formations or of mixing with permian waters from the point of view of aquifer management the perceptible no 3 increase could provide information on the progress of any contamination under the aerobic conditions in addition the few key elements indicators of disequilibrium related to overlying or deep waters should be included in regular monitoring programmes

russell fault early strike slip fault of california coast ranges the subsurface russell fault is a controlling structure for oil fields in the cuyama basin in the southern salinian block of coastal california movement on the russell fault began at about 23 ma following deposition of the oligocene simmler formation in extensional basins bounded on the south by normal fault ancestors of the la panza and ozena reverse faults right lateral strike slip on the russell fault began with deposition of the soda lake shale member of the vaqueros formation the soda lake shale member and painted rock sandstone member of the vaqueros formation were deposited in west trending right stepping troughs while most of the right slip on the russell fault accumulated 23 19 ma pre vaqueros strata are offset 26 29 km but vaqueros isopachs are offset onl 3 7 km the whiterock bluff shale member of the monterey formation is dated as 16 5 14 ma the facies boundary between the whiterock bluff shale member and the branch canyon sandstone is offset 3 3 4 km coeval subsidiary faults near the russell fault in miocene strata at least as young as 11 ma also support distributed right lateral shear the russell fault is overlain unconformably by the morales formation which includes strata as old as 4 ma 1 m y north of russell ranch oil field the russell fault bifurcates into a western strand that joins the chimeneas fault and an eastern strand that is overridden by the big spring reverse fault the russell fault may continue to the southeast as the ozena fault and be offset across the big pine fault right slip began 6 7 m y after the predicted time of first contact of the pacific and north american plates slip rates were 6 5 7 mm yr during 23 19 ma 0 1 0 3 mm yr during 19 14 ma and 0 3 1 1 mm yr during 14 4 ma the sudden decrease in slip rate occurred as the basin deepened at the time of monterey formation deposition which began about 19 ma the relation of development of vaqueros basins containing soda lake shale member to strike slip on the russell fault suggests that a reconstruction of the early miocene strike slip tectonics of the southeastern coast ranges may permit exploration for other hidden vaqueros basins elsewhere in the salinian block

hydraulic resistance of submerged flexible vegetation the main research objective consisted in analysing the influence of roughness caused by aquatic vegetation av in particular submerged macrophytes on the overall flow field these plants are highly flexible and behave differently depending on the flow situation they also react substantially to the flow field and thus the roughness becomes variable and dynamic conventional flow formulas such as the manning or the strickler formula are one dimensional and based on integral flow parameters they are not suitable for quantifying the roughness of av because the flow is complex and more dimensional due to the variable behaviour of the plants therefore the present investigation concentrates on the definition of a characteristic hydraulic roughness parameter to quantify the resistance of av within this investigation laboratory experiments were carried out with three different types of av chosen with respect to varying plant structures as well as stem lengths velocity measurements above these plants were conducted to determine the relationship between the hydraulic roughness and the deflected plant height the deflected plant height is used as the geometric roughness parameter whereas the equivalent sand roughness based on the universal logarithmic law modified by nikuradse was used as hydraulic roughness parameter the influence of relative submergence on the hydraulic roughness was also analysed the analysis of the velocity measurements illustrates that equivalent sand roughness and zero plane displacement of the logarithmic law are correlated to the deflected plant height and are equally to this height

noble gases in crude oils from the paris basin france implications for the origin of fluids and constraints on oil water gas interactions in order to investigate the potential of noble gases to trace the dynamics of oil reservoirs we have analysed the abundance and isotopic composition of all noble gases he ne ar kr and xe in crude oils from the paris basin france using a new extraction and purification procedure the main oil reservoirs are presently located in the jurassic dogger limestone and in the triassic keuper sandstone but hydrocarbons originated from a common source rock formation located in the interbedded liassic sequence despite this common origin the abundance and isotopic ratios of the noble gases differ between the dogger and the keuper the isotopic compositions of kr and xe are indistinguishable from that of air 3he 4he ratios higher than those predicted from radiogenic production in the sediments or in the crust are attributed to the occurrence of mantle derived 3he in the basin each sedimentary sequence is characterised by well defined and homogeneous 21ne 22ne and 40ar 36ar ratios which average 0 0306 0 0008 and 312 10 for the dogger and 0 0367 0 0012 and 664 30 for the keuper respectively the main source of radiogenic noble gases appears to be the continental crust underlying the basin with possible regional contributions of noble gas isotopes produced in the sediments the helium and argon isotopic ratios of the dogger oils are very similar to those observed in geothermal waters flowing in the dogger aquifer throughout the basin demonstrating that noble gases in oils derive from associated groundwaters oil reservoirs in the paris basin therefore accumulate noble gases from wide regions of the continental crust through cross formational flow of groundwaters and subsequent partitioning into oil this observation implies that noble gases cannot be directly used to date oils but can provide time constraints if 1 water oil interactions are quantified and 2 the residence time as well as the noble gas characteristics of associated groundwaters are known oil water gas partitioning processes are well recorded in the fractionation of noble gas elemental abundance two distinct processes have been identified 1 accumulation of atmosphere derived ang and radiogenic noble gases both initially dissolved in groundwaters resulting in a positive correlation between absolute amount of ang and the extent of heavy noble gas fractionation and 2 subsequent fractional degassing resulting in a negative correlation between ang abundance and heavy noble gas fractionation degassing is particularly evident for the keuper oils and might have occurred in the reservoirs following hydrodynamic gas stripping the ang abundance in the dogger reservoirs requires that about one order of magnitude more water than presently observed has interacted with the oil given current estimates of the residence time for groundwaters in the dogger aquifer the duration of oil water interaction is in qualitative agreement with a palaeocene oligocene age for the major episode of secondary oil migration in the paris basin high xenon contents in keuper reservoirs suggest that they have experienced hydrodynamic interactions between flowing waters and oils for long time and that the trias might have reached hydrostatic condition only recently

progradational sequences in miocene shoreline deposits southeastern caliente range california abstract an exceptionally well exposed marine nonmarine transition in middle miocene strata exists in the southeastern caliente range california about 50 individual progradational sequences form a succession that ranges in thickness from approximately 1000 m where predominantly nonmarine to more than 2500 m where predominantly marine paleogeographic evidence in basalt flows near the top of the succession and in overlying fluvial deposits indicates that these middle miocene strata were deposited across a north northwest trending shoreline a complete progradational sequence typically is several meters to a few tens of meters thick and includes strata that represent three intertonguing stratigraphic units individual sequences generally rest on a thin gravel deposit interpreted as a transgressive lag on an erosional surface the gravel is overlain by structureless siltstone or fine grained sandstone deposited at water depths where the rate of faunal mixing exceeded that of production of structures by physical processes these rocks grade upward into bedded fine sandstone deposited closer to shore where physical processes exceeded bioturbation crossbedded lenses of coarse sand or fine gravel in the upper part of this facies suggest the presence of fairly long period surface waves the bedded fine sandstone is sharply ove lain by a cross bedded coarse sandstone facies that is interpreted as a combined offshore bar rip channel surf zone assemblage cross strata dip dominantly offshore suggesting substantial deposition from rip currents a secondary shoreparallel mode of cross strata direction suggests longshore currents produced by surface waves from the northwest the crossbedded coarse grained sandstone grades upward into planar bedded medium grained sandstone that is interpreted as a beach foreshore this facies grades upward through structureless medium grained sandstone into nonmarine or lagoonal red and green mudstone of the caliente formation the middle miocene succession was deposited in a subsiding basin that was otherwise remarkably stable tectonically the position of the strand line differed no more than a few kilometers through a period of 1 to 3 m y the average duration of the transgressive regressive cycles a few tens of thousands of years together with their distribution in groups of three or four in the lower two thirds of the succession is consistent with the pattern of long term climatic cycles produced by periodicity of the earth s solar orbit and may be related to eustatic sea level changes attendant to the development of the antarctic ice cap changes in the pattern of progradation in the upper part of the succession and nearby basaltic eruptions may have been precursors to the onset of movement along th san andreas fault in this area 12 14 m y ago

chlorine 36 dating of deep groundwater from northern sahara summary the continental intercalaire from sahara is one of the largest confined aquifers in the world in the northern part of the basin the depth of the aquifer ranges between 400 and 1800 m and the main flow direction is from west to east chlorine 36 analyses were performed on groundwater samples mainly collected along this flowpath they show a wide range of 36 cl contents from 8 to 99 10 15 at at 1 expressed as 36 cl cl atomic ratio in order to evaluate the epigene production measurements were also performed on chloride extracted by leaching from a soil profile near the recharge zone this showed that the contribution of epigene production remains limited a range of 36 cl cl ratios from 116 to 133 10 15 was adopted for groundwater recharging the aquifer including both meteoric production and epigene production for most of the samples collected along the main flowpath a significant decay effect was observed an attempt of dating was made by using an equation that takes into account radioactive decay of the meteoric epigene input deep production and chloride dissolution within the aquifer the calculated 36 cl residence time varies from 16 to 500 ka for the minimum ages and from 25 to 1200 ka for the maximum ages an increase of residence time is observed up to about 500 km from the recharge zone this corresponds to mean flow velocities of 0 2 0 5 m a 1 and to an average permeability of 1 1 0 6 10 5 m s 1 at the scale of several hundreds of kilometres

stable isotope conservation and origin of saline waters from the middle jurassic aquifer of the paris basin france abstract seventy nine samples of formation water from geothermal boreholes oil field and ground water wells tapping the dogger middle jurassic limestone reservoir of the paris basin have been analyzed for their 2h 18o tds bromide and chloride contents geostatistical mapping of 2h and of 18o contents and their variations with chloride content indicate that both isotopes have a common origin and a similar behaviour within the aquifer the 2h and 18o values increase progressively from the outcrops toward a zone where temperature cl and tds values are high the 2h and 18o values are very uniform in this zone and do not show any relation with formation temperature in contrast to what is generally observed in other sedimentary basins a discussion of isotopes exchange with the carbonate matrix for oxygen and with h2s for deuterium shows that such processes are not controlling the heavy isotope contents of groundwaters this is attributed to the relatively short residence time of groundwaters in the aquifer both 2h and 18o contents of groundwater may thus be considered as conservative tracers in the dogger aquifer of the paris basin and their initial contents are modified only by fluid mixings complex mixing processes account for stable isotope composition tds cl and br values of the dogger fluids all mixtures include a brine component meteoric water percolated and dissolved halite in the triassic aquifer secondary brine this saline solution mixed with some residual primary brine then migrated via vertical faults into the dogger aquifer such migration is found to be in agreement with data from fluid inclusions in late carbonate cements from the liassic and dogger strata the requirement that these units were exposed implies that meteoric invasion could not have occurred before the tertiary successive mixings of the brine with several types of meteoric waters depleted in heavy isotopes account for the present isotope and chemical compositions of the dogger fluids

the last climatic cycles in western europe a comparison between long continuous lacustrine sequences from france and other terrestrial records abstract during the last two decades numerous studies applied to various continental deposits have highly improved the knowledge of environmental changes in western europe during the last climatic cycles here we review a set of available data and try to correlate and compare the three long lacustrine sequences from france la grande pile les echets and le velay with other west european discontinuous limnic deposits fluvial systems and l ss accumulations limnic sequences provide the best records of the last interglacial and early glacial ca 125 75 kyr allowing a clear picture of environmental changes during this interval nevertheless there are divergent interpretations on the timing and climate regime of the last interglacial during the last glacial in the north atlantic deep sea cores and greenland ice cores short term abrupt climatic fluctuations bond events dansgaard oeschger events which are poorly or partly reflected on the continent have been recognised the classical subdivision in a lower ca 75 55 kyr very cold middle ca 55 29 kyr cold and upper pleniglacial ca 29 15 kyr very cold is confirmed both by limnic and terrestrial sequences in the rhine valley north eastern france belgium and the netherlands subcontinuous l ss accumulation river systems and associated periglacial features provide quantitative climate reconstructions that are compared with those obtained from limnic sequences interstadial events may be correlated with the major warm oscillations of the grip core during the upper pleniglacial no clear vegetation changes are apparent from lacustrine pollen sequences whereas thick l ss accumulations have registered a succession of climatic changes the timing of the lateglacial warming is now well documented from rare annually laminated lake sediments

carbon isotope exchange rate of dic in karst groundwater abstract the kinetics of isotopic exchange between dissolved inorganic carbon dic of groundwater and calcite of the matrix of karst aquifers of cyrenaica libya can be deduced from 13 c and 14 c data the aquifers are mostly confined and the majority of the wells do not show any occurrence of modern recharge in 1976 1980 in fact the tritium content was below 1 tritium unit tu in most sites assuming that the isotopic exchange takes place through a first order reaction such as 14 c radioactive decay it can be shown that a linear correlation occurs between ln a and ln m e p where a is the 14 c activity m and are the 13 c contents of matrix calcite and dic respectively and e p is the 13 c enrichment in caco 3 precipitation the slope of the correlation provides the half life of the isotopic exchange process for cyrenaica karst groundwater a half life of about 11 000 years is obtained i e about double that of 14 c radioactive decay the isotopic exchange kinetics also depends on the ratio between groundwater volume and the calcite surface exposed to the exchange process thus other aquifers will show different exchange half life values the cretaceous chalk aquifers of the paris basin france and lagerdorf germany give a half life of about 4000 years much shorter than that of cyrenaica which may be due to the high porosity i e to the large surface available for the isotope exchange process the berkshire chalk aquifer uk gives a half life of about 10 000 years much higher half lives above 20 000 years are obtained for two sandy aquifers in flevoland the netherlands and texas usa which could be explained by the low caco 3 content of the aquifer matrix the highest half life value about 40 000 years is obtained in an artesian limestone aquifer in florida usa

paleogeography of monterey formation cuyama basin california the cuyama basin is one of several discrete middle cenozoic basins that formed a continental borderland in the coastal california province during the miocene the monterey formation is lithologically and stratigraphically complex it varies widely in thickness up to 4 500 ft 1 400 m reflecting variable subsidence within the basin thinning over anticlines and the cox fault zone suggests structural movement occurred contemporaneously with sedimentation beginning in the late saucesian early miocene the age of the monterey formation also varies becoming younger to the northwest areas of maximum subsidence migrated from southeast cuyama valley to northwest northern la panza range schematic paleogeographic maps constructed on 4 time slices illustrate that the depositional history of the basin reflects these subsidence patterns and various depositional controls late saucesian relizian early miocene time is characterized by relatively low sea level maximum subsidence in the southeast and basinal sedimentation varying from calcareous biogenous sediments to sandy submarine fan deposits luisian early mohnian middle miocene patterns reflect high sea level maximum subsidence in the northwest and basinal sediments of a calcareous or siliceous biogenous nature finally the entire southern salinian block shoaled to shallow marine or nonmarine conditions by the end of mohnian late miocene time modified journal abstract

stable chlorine isotopes in arid non marine basins instances and possible fractionation mechanisms abstract stable chlorine isotopes are useful geochemical tracers in processes involving the formation and evolution of evaporitic halite halite and dissolved chloride in groundwater that has interacted with halite in arid non marine basins has a 37 cl range of 0 3 far greater than the range for marine evaporites basins characterized by high positive 1 to 3 near 0 and negative 0 3 to 2 6 are documented halite in weathered crusts of sedimentary rocks has 37 cl values as high as 5 6 salt excluding halophyte plants excrete salt with a 37 cl range of 2 1 to 0 8 differentiated rock chloride sources exist e g in granitoid micas but cannot provide sufficient chloride to account for the observed data single pass application of known fractionating mechanisms equilibrium salt crystal interaction and disequilibrium diffusive transport cannot account for the large ranges of 37 cl cumulative fractionation as a result of multiple wetting drying cycles in vadose playas that produce halite crusts can produce observed positive 37 cl values in hundreds to thousands of cycles diffusive isotope fractionation as a result of multiple wetting drying cycles operating at a spatial scale of 1 10 cm can produce high 37 cl values in residual halite chloride in rainwater is subject to complex fractionation but develops negative 37 cl values in certain situations such may explain halite deposits with bulk negative 37 cl values future field studies will benefit from a better understanding of hydrology and rainwater chemistry and systematic collection of data for both cl and br

vegetation modulated landscape evolution effects of vegetation on landscape processes drainage density and topography 1 topography acts as a template for numerous landscape processes that include hydrologic ecologic and biologic phenomena these processes not only interact with each other but also contribute to shaping the landscape as they influence geomorphic processes we have investigated the effects of vegetation on thresholds for channel initiation and landform evolution using both analytical and numerical approaches vegetation is assumed to form a uniform ground cover runoff erosion is modeled based on a power function of excess shear stress in which shear stress efficiency is inversely proportional to vegetation cover this approach is validated using data plant effect on slope stability is represented by additional cohesion provided by plant roots vegetation cover is assumed to reduce sediment transport rates due to physical creep processes rainsplash dry ravel and expansion and contraction of sediments according to a negative exponential relationship vegetation grows as a function of both available cover and unoccupied space by plants and is killed by geomorphic disturbances runoff erosion and landsliding and wildfires analytical results suggest that in an equilibrium basin with a fixed vegetation cover plants may cause a transition in the dominant erosion process at the channel head a runoff erosion dominated landscape under none or poor vegetation cover may become landslide dominated under a denser vegetation cover the sign of the predicted relationship between drainage density and vegetation cover depends on the relative influence of vegetation on different erosion phenomena with model parameter values representative of the oregon coast range ocr numerical experiments conducted using the channel hillslope integrated landscape development child model confirm the findings based on the analytical theory a highly dissected fluvial landscape emerges when surface is assumed bare when vegetation cover is modeled landscape relief increases resulting in hollow erosion dominated by landsliding interestingly our simulations underscore the importance of vegetation disturbances by geomorphic events and wildfires on the landscape structure simulated landscapes resemble real world catchments in the ocr when such disturbances are considered

a cross calibration of chlorine isotopic measurements and suitability of seawater as the international reference material abstract a collection of 24 seawaters from various worldwide locations and differing depth was culled to measure their chlorine isotopic composition 37cl these samples cover all the oceans and large seas atlantic pacific indian and antarctic oceans mediterranean and red seas this collection includes nine seawaters from three depth profiles down to 4560 mbsl the standard deviation 2 of the 37cl of this collection is 0 08 which is in fact as large as our precision of measurement 0 10 thus within error oceanic waters seem to be an homogeneous reservoir according to our results any seawater could be representative of standard mean ocean chloride smoc and could be used as a reference standard an extended international cross calibration over a large range of 37cl has been completed for this purpose 13 geological fluid samples of various chemical compositions and a manufactured ch3cl gas sample with 37cl from about 6 to 6 have been compared data were collected by gas source isotope ratio mass spectrometry irms at the paris reading and utrecht laboratories and by thermal ionization mass spectrometry tims at the leeds laboratory comparison of irms values over the range 5 3 to 1 4 plots on the y x line showing a very good agreement between the three laboratories on 11 samples the trend line between paris and reading universities is 37clreading 1 007 0 009 37clparis 0 040 0 025 with a correlation coefficient r2 0 999 tims values from leeds university have been compared to irms values from paris university over the range 3 0 to 6 0 on six samples the agreement between these two laboratories using different techniques is good 37clleeds 1 052 0 038 37clparis 0 058 0 099 with a correlation coefficient r2 0 995 the present study completes a previous cross calibration between the leeds and reading laboratories to compare tims and irms results anal chem 72 2000 2261 both studies allow a comparison of irms and tims techniques between 37cl values from 4 4 to 6 0 and show a good agreement 37cltims 1 039 0 023 37clirms 0 059 0 056 with a correlation coefficient r2 0 996 our study shows that for fluid samples if chlorine isotopic compositions are near 0 their measurements either by irms or tims will give comparable results within less than 0 10 while for 37cl values as far as 10 either positive or negative from smoc both techniques will agree within less than 0 30

the limited growth of vegetated shear layers 1 in contrast to free shear layers which grow continuously downstream shear layers generated by submerged vegetation grow only to a finite thickness because these shear layers are characterized by coherent vortex structures and rapid vertical mixing their thickness controls exchange between the vegetation and the overlying water experiments conducted in a laboratory flume show that the growth of these obstructed shear layers is arrested once the production of shear layer scale turbulent kinetic energy ske is balanced by dissipation of ske within the canopy this equilibrium condition along with a mixing length closure scheme was used in a one dimensional numerical model to predict the mean velocity profiles of the experimental shear layers the agreement between model and experiment is very good but field application of the model is limited by a lack of description of the drag coefficient in a submerged canopy

a phenomenological model for the flow resistance over submerged vegetation 1 the bulk velocity ub in streams is conventionally estimated from manning s equation but difficulties remain in parameterizing the roughness coefficient n when the streambed is covered with vegetation a two layer velocity model is proposed to determine n and ub for the submerged vegetation case the modeled n is derived as a function of flow and vegetation properties that can be inferred from remote sensing platforms such as canopy height leaf area density and flow depth the main novelty in the proposed formulation is that the shear stress is related to the mean velocity profile by considering both ejective and sweeping motions by dominant eddies the proposed model is tested against a large data set from the literature and is shown to perform well particularly for rigid vegetation poorer model performance for flexible vegetation can be partially attributed to the shape of the assumed mean velocity profile the roughness coefficient n is found to be robust to variations in the average spacing between canopy elements allowing the model to be applied to heterogeneous canopies

evolution of the southern san joaquin basin and mid tertiary transitional tectonics central california a cenozoic tectonic and sedimentary history is proposed for the southern san joaquin basin ssjb and tehachapi mountains that evolved adjacent to the plate margin off central california seismic reflection borehole field biostratigraphic and paleomagnetic data are integrated into geologic and fault structure maps cross sections and geohistory plots and are analyzed with previous work in the region to develop a model relating the sequence timing and distribution of complex tectonically linked events the largely buried structures and strata in the ssjb preserve an unusually complete record of the mid tertiary transition from convergent to transform plate boundary as well as the regional transition to contraction during the pliocene significant structural relief existing across both extensional and contractile features is preserved in the subsurface and an active fold thrust belt propagates basinward along the margin of the u shaped tejon embayment the cenozoic evolution of the ssjb reflects the regional deformation of central california as different tectonic events followed each other along the adjacent north american plate margin five oligocene miocene basin phases are identified in the ssjb 1 late oligocene early miocene extensional subsidence with high and low angle normal faulting accompanied by volcanism and deposition of coarse syntectonic conglomerates 2 middle miocene uplift 3 later mid miocene transtensional subsidence to lower bathyal depths 4 alternating subsidence and uplift until the late miocene and 5 flexural subsidence due to pliocene to recent contraction reconstructions of mid tertiary california place the southern san joaquin tehachapi extensional terrane as a paleotectonic block located between the western mojave terrane then to the east and the western california terrane then to the south and west regional extension occurred during a long transition period between convergent and transform boundaries along the north american plate margin significant slip along the san andreas transform postdates this extensional event its origin apparently coincided with a regional middle miocene uplift event indicating that the san andreas fault is younger than previously supposed the tertiary ssjb has subsided due to extension transtension crustal tilting and thrust related loading the maricopa subbasin floor is likely composed of ensimatic and mafic rocks like those along the west side of the sierra nevada and locally has subsided beyond 12 km in contrast the relatively stable tejon embayment underlain by sierran crystalline crust achieved its maximum subsidence in the miocene since pliocene time the ssjb has filled and continued to deepen after the basin was tectonically shut off from the pacific ocean

sea surface temperature variability in the north atlantic during the last two glacial interglacial cycles comparison of faunal oxygen isotopic and mg ca derived records climate variability in the northeast atlantic was investigated on glacial interglacial and millennial time scales during the last 200 000 years using sea surface temperature sst records derived from planktonic foraminiferal diversities and from mg ca measurements on globigerina bulloides paleoceanographical interpretations are supported by species composition analyses benthic and planktonic isotopic data as well as records of iceberg rafted debris ird differences of climate development are recognized for both interglacial and glacial periods temperature estimates indicate slightly warmer conditions up to 2 c during marine oxygen isotope stage mis 5e than during the holocene in contrast to the last glaciation when the sst minimum coincided with a minimum in solar insolation immediately before termination i during the penultimate glaciation a long sst minimum occurred at times of intermediate solar insolation well preceding the onset of termination ii this discrepancy between two glacial terminations may be explained by an inherently different orbital configuration characteristic for each glacial interval despite these differences between the two glacial trends the superimposed shorter lived climatic events reveal the same order of principal steps implying their common causal nature a direct comparison of faunal ssts with those retrieved from mg ca analysis shows that mg ca derived temperatures follow the general glacial interglacial trend however the latter appear to be largely overestimated supported by 18o data in g bulloides which show little response to millennial scale variability there seems to be a need for species dependent calibration experiments that also consider the different oceanographic settings this particular species can live in

vegetation change in a climatic cycle of early pleistocene age in the leffe basin northern italy abstract the plio pleistocene deposits of the leffe basin in the lombardian pre alps in italy first investigated in quarry and lignite mine shafts by lona in 1950 were recently cored the pollen record of part of this core reveals a sequence of four climatic cycles one of them which is about 1 6 ma old and particularly characteristic is discussed here a long interglacial stage can be identified by the dominance of pollen of deciduous trees of temperate climate it clearly shows a forest succession of a mixed oak forest of dry temperate climate followed by a strong development of a juglandaceae assemblage rich in arcto tertiary elements some of them indicating a wet climate in particular the carya peaks appear to be linked to a warm temperate 14 16 c mean annual temperature humid maritime climate with a long growth season if we compare them with modern and fossil analogs this stage is followed by a cooling leading to a long phase of wet coniferous forest this forest succession is subsequently interrupted by a brief period of open vegetation indicating a drier and colder continental climate followed by a new vegetational cycle the climate evolution is discussed in comparison with other recent pollen successions of uppermost pliocene age in the mediterranean area the cycle described is estimated to have lasted about 30 ka the entire leffe lacustrine succession records eight climatic cycles of moderate amplitude we suggest that this cyclicity has been induced by obliquity forcing correlation of the cold phases with the major glacial events of the southern alps as proposed by venzo 1950 and lona 1950 is excluded

modeling flow in coral communities with and without waves a synthesis of porous media and canopy flow approaches both canopy flow and porous media theories have been developed independent of one another to predict flow through submerged porous structures these approaches are very similar albeit with some key differences in how canopy resistance forces are parameterized canopy models provide a means of parameterizing the shear stresses that occur at the top of the canopy whereas porous media models can often provide a simpler and more tractable way of parameterizing turbulent form drag based on simple morphological metrics and empirical relationships already in the hydrology literature we developed a set of equations combining aspects of both models and applied this hybridized model to predict the flow structure within an experimental canopy formed by the branching coral porites compressa using model parameter values obtained from the literature results from the model predictions agreed well with direct measurements of flow speed and flow forces derived from particle image velocimetry under conditions of both unidirectional and wave driven oscillatory flow

single parameter model of vegetated aquatic flows coupled flows through and over permeable layers occur in a variety of natural phenomena including turbulent flows over submerged vegetation in this work we employ a two domain approach to model flow through and over submerged canopies the model amenable of a closed form solution couples the log law and the darcy brinkman equation and is characterized by a novel representation of the drag force which does not rely on a parametrization through an unknown drag coefficient this approach limits to one i e the obstruction permeability the number of free parameters analytical expressions for the average velocity profile through and above the canopies volumetric flow rate penetration length and canopy shear layer parameter are obtained in terms of the canopy layer effective permeability the model suggests that appropriately rescaled velocities in the canopy and surface layers follow two different scaling laws the analytical predictions match with the experimental data collected by ghisalberti and nepf 2004 and nepf et al 2007

sea surface temperature during the quaternary at odp sites 976 and 975 western mediterranean abstract based on the relative abundances of the planktonic foraminifera species found in quaternary samples from odp sites 976 alboran sea and 975 menorca rise and using a modern analog technique winter and summer sea surface temperatures were estimated frequency distributions of temperatures are asymmetrical more so at odp site 976 where there is a greater abundance of samples from the warm part of the temperature range during the quaternary there is a general tendency for temperatures to fall with an overall diminution of 1 c for the winters and of more than 2 c for the summers overall mean temperatures and those of the biostratigraphic intervals identified are higher at odp site 975 than at 976 when differences are statistically significant the q1 interval i e the oldest in the quaternary is colder than the upl i e terminal pliocene and the q2 interval the q3 interval is also colder than the q2 interval and the q4 interval i e the most recent interval differences between intervals general trends and the asymmetries of frequency distributions cannot be explained as linear responses to insolation the stratigraphic series from odp site 976 was dated by correlating the relative maxima and minima of the summer temperature series with those of insolation during the month of july at 65 n it was found that 26 2 of the variance of the time series of temperatures was concentrated in the harmonics related to precession and obliquity while 19 was located in those related to eccentricity there are indications of the need to add lags and leads to the age of temperature spikes with respect to insolation but such delays and leads cannot be quantified precisely

palaeoclimatic implications of the growth history and stable isotope delta o 18 and delta c 13 geochemistry of a middle to late pleistocene stalagmite from central western italy the age structure and stable isotope composition of a stalagmite cc i from an upland cave in central western italy were studied to investigate regional response to global climatic changes four growth phases are constrained by 28 thermal ionization and multi collector inductively coupled plasma mass spectrometry th u ages and reveal intermittent deposition through the period between marine isotope stage mis 11 and 3 similar to380 and similar to43 kyr most of the growth took place between similar to380 and similar to280 kyr a period punctuated briefly by a hiatus in deposition through the glacial maximum of mis 10 growth was terminated abruptly at 280 kyr just prior to the mis 8 glacial maximum with a present day chamber temperature of 7 5 degreesc the timing of hiatuses close to these glacial maxima point to freezing conditions at the time no deposition was recorded through the entirety of mis 7 and most of mis 6 whilst two minor growth phases occurred at similar to141 125 and similar to43 kyr growth at 141 kyr indicates temperatures 0 degreesc at a time when mis 6 ice volumes were close to their maximum high stable carbon isotope delta 13 c values similar to2 8parts per thousand to 3 1parts per thousand throughout the stalagmite s growth reflect a persistently low input of biogenic co2 indicating that the steep barren and alpine like recharge area of today ha s been in existence for at least the last similar to380 kyr during mis 9 the lowest delta 13 c values occur well after maximum interglacial conditions suggesting a lag in the development of post glacial soils in this high altitude karst the stable oxygen isotope delta 18 o trends match the main structural features of the major climate proxy records specmap vostok and devils hole suggesting that the delta 18 o of cc1 has responded to global scale climate changes whilst remarkable similarity exists between cc1 delta 18 o and regional sea surface temperature reconstructions from north atlantic core odp980 and southwest pacific marine core md97 2120 through the most detailed part of the cc1 record mis 9 8 the results suggest that cc1 and other stalagmites from the cave have the potential to capture a long record of regional temperature trends particularly in regards to the relative severity of pleistocene glacial stages c 2004 elsevier b v all rights reserved

miocene phosphate accumulation in the cuyama basin southern california abstract middle and upper miocene phosphatic strata in the cuyama basin of southern california contain approximately 6 4 10 9 metric tons 2 1 10 14 mol of phosphorus p that accumulated in slope and shelf strata at rates between 0 9 and 3 8 mol p cm 2 year 1 from 15 5 to 10 8 ma an estimated 63 of all phosphorus lies in a single third order sequence deposited between 14 8 and 13 ma the main impetus for this brief phosphogenic event was a 200 m relative sea level rise that resulted from strike slip faulting immediately east of the basin minor element and petrologic analyses suggest the overall increase in phosphorus accumulation correlates with less reducing conditions in the shallowly buried marine sediments on the slope and the expansion of phosphogenesis to the outer shelf both events were probably related to landward shifts of the pacific oxygen minimum zone and coastal upwelling centers during the relative sea level rise whereas these tectonic events were apparently local the phosphatic deposits of the cuyama basin clearly demonstrate that tectonism can strongly influence phosphate accumulation rates in marginal marine environments

coarse grained deltaic sedimentation in the miocene cuyama strike slip basin california coast ranges abstract the cuyama basin located in the southern coast ranges of california southwest of the san andreas fault developed early in the history of the san andreas transform system the miocene marine basin formed in a transtensional setting along a dextral strike slip fault of the transform system following oligocene non marine basin formation in an extensional setting the lower and middle miocene vaqueros formation in the northwestern part of the basin which represents the first of two transgressive regressive cycles is described here in terms of nine facies in two broad facies groups the 400 m thick soda lake shale member of the vaqueros comprises deep basin and starved basin facies a thin transgressive facies occurs locally at the base of the formation the overlying painted rock sandstone member of the vaqueros which is more than 2200 m thick and consists mostly of coarse grained sandstone and pebbly sandstone constitutes a delta complex of prodelta slope channel delta front tide influenced distributary channel interdistributary bay and fluvial channel facies the basinal depositional system consisted of turbidite mud and sand and hemipelagic and pelagic sediments of the basinal facies deposited in a rapidly subsiding basin the delta depositional system consisted of the delta complex facies that prograded into the deep basin and had a steep prodelta slope that extended to bathyal depths the delta is inferred to be a mixed fluvial wave dominated fan delta analogous in its delta front morphology and processes to a fjord delta in which coarse sediment delivered to the delta front by braided streams was transported down the prodelta slope into deep water by sediment gravity flows transgression and rapid deepening of the basin in the early miocene coincided with rapid tectonic subsidence deepening culminated with deposition of a starved basin facies or condensed section at the time of maximum transgression which was followed by the beginning of a regression and basin shallowing the overall basin history and geometry of the northwestern cuyama basin are typical of strike slip basins the initial rapid subsidence to bathyal depths at rates of more than 500 m m y in the early miocene is interpreted to be a result of extension at the releasing bend of a dextral strike slip fault

a method for climatic reconstruction of the mediterranean pliocene using pollen data pollen data from numerous sites around the mediterranean sea indicate that several important vegetation and climatic changes occurred during the pliocene these data are in good agreement with pollen records from northwest europe and with 18o curves from mediterranean and atlantic deep sea cores quantitative palaeoclimatic reconstructions from pliocene pollen data of the mediterranean region cannot be based on conventional modern analogue techniques as individual pliocene pollen spectra contain taxa representing temperate warm temperate and subtropical plants that do not grow together today instead we propose a new method that uses a climatic amplitude method modified to take partially into account the relative abundances of the taxa we applied this method to the pliocene garraf 1 palynological sequence from catalonia which provides a long continuous record of climatic change from 5 3 ma to the early pleistocene we estimate that annual temperatures were 1 to 5 c higher than today and the annual precipitation 400 to 1000 mm higher than today prior to the beginning of the late cenozoic glacial interglacial cycles in contrast temperature and precipitation both fell sharply during the glacial phases of the earliest glacial interglacial cycles

widespread cementation induced by inflow of continental water in the eastern part of the paris basin o and c isotopic study of carbonate cements abstract mesozoic limestones from the eastern part of the paris basin display mostly in strata rich in bioherms abundant macro cavities vugs and some connected micro fractures almost completely filled with euhedral calcite crystals late calcite spar the interparticle porosity of limestones is also filled with euhedral calcite spar cements similar to those observed in vugs and fractures and rarely displays the preservation of the structures typical of early marine cements these calcite spars both from vugs fractures infillings and from cemented porosity were studied in drilled cores cross cutting the kimmeridgian to bathonian series with the main objective of determining the nature and flow regime of the fluids responsible for the strong porosity reduction observed in that part of the paris basin mesozoic limestones the approach combined mineralogical and geochemical studies o and c stable isotopic compositions measured by conventional and sims methods with temperature estimates from fluid inclusion analyses the 13 c values of late calcite are close to those of the host limestones and correlate with the 13 c changes in host rocks indicating a local source of c by contrast late calcites from vugs fractures and also in the cemented interparticle porosity of limestones have 18 o values around 21 smow values which are distinct from those of bulk host limestones 25 to 27 the 18 o value of the fluid is estimated to be 6 8 to 2 5 for a crystallisation temperature between 32 and 42 c determined from fluid inclusion studies thus the parent fluid of cemented interparticle porosity and vug and fracture infillings likely contained a component of meteoric water in contrast to the previous belief that the reduction of porosity in those series was related to early marine diagenesis possible situations in which such meteoric fluid could have occurred are i a stage when the limestone aquifers were directly connected to surface water and or ii channelling of water from deeper zones in the basin through regional fault systems the o isotopic compositions of the calcite cements in the underlying 140 m thick callovo oxfordian argillites and those of the less recrystallised bathonian to kimmeridgian limestones are those expected for unmodified marine calcite 18 o ca 28 smow therefore from the isotopic point of view the callovo oxfordian argillites remained essentially unaffected by the paleo fluid circulation documented in the adjacent limestones series this indicates the argillites acted as an efficient permeability barrier in the past

chlorine transfer out of a very low permeability clay sequence paris basin france 35cl and 37cl evidence abstract the marine callovo oxfordian clay formation is found at a depth around 410m in the eastern part of the paris basin france it is a very low permeability formation investigated by the french agency for nuclear waste management andra to study the feasibility of a radioactive waste disposal examining hydrogeological and geochemical characteristics of the clay sequence may test confinement properties of this formation this study uses chlorine isotopes to investigate long term transport processes which may carry chemical elements out of the clay layer to the surrounding rocks detailed chlorine concentration and 37cl depth profiles are examined using pore waters and aquifer waters sampled in the clay formation and its surrounding aquifers the dogger at the bottom and the oxfordian kimmeridgian tithonian unit at the top they are discussed in terms of chlorine budget and hydrogeological processes clay pore waters and aquifer waters show strong chlorine concentration depletion a steep cl concentration gradient from the dogger at 500m in depth 2500 mg l to the oxfordian kimmeridgian tithonian aquifer near the surface 10 mg l is associated to a v shaped profile of the 37cl values modelling cl transport shows that a hydrodynamic dispersion process explains cl concentration and 37cl profiles in oxfordian limestone this process implies a mean upward flux of chloride in the 2 6 10 8 8 2 10 8 mole m2 yr range from the clay formation towards upper limestones where a westward advective flow disperses the chloride the modelling and knowledge of underground water transfer suggest a maximum effective cl hydrodynamic vertical dispersion coefficient vertical cl transport coefficient of 7 6 10 10 m2 s chlorine transfer through the callovo oxfordian clay since deposition 160my ago can be mainly described by the interplay of an early dilution and a later hydrodynamic dispersion event which has apparently erased most of the isotopic effects of diagenetic events such as early diffusion ion filtration etc

noble gases stable isotopes and radiocarbon as tracers of flow in the dakota aquifer colorado and kansas abstract a suite of chemical and isotope tracers dissolved noble gases stable isotopes of water radiocarbon and cl have been analyzed along a flow path in the dakota aquifer system to determine likely recharge sources ground water residence times and the extent of mixing between local and intermediate flow systems presumably caused by large well screens three water types were distinguished with the tracers each having a very different history two of the water types were found in south eastern colorado where the dakota is poorly confined the tracer data suggest that the first group recharged locally during the last few thousand years and the second group was composed of ground water that recharged earlier during a cooler climate presumably during the last glacial period lgp and mixed aged water the paleotemperature record archived in this groundwater system indicates that south eastern colorado was about 5 c cooler during the lgp than during the late holocene similar temperature changes derived from dissolved noble gases in other aquifer systems have been reported earlier for the south western united states the third water type was located down gradient of the first two in the confined dakota in western and central kansas groundwater residence time of this water mass is on the order of 10 4 10 5 yrs and its recharge location is near the colorado and kansas border down gradient of the other water types the study shows the importance of using multiple tracers when investigating ground water systems

establishing constraints on groundwater ages with 36cl 14c 3h and noble gases a case study in the eastern paris basin france abstract groundwaters from the tithonian kimmeridgian oxfordian and upper dogger aquifers within the eastern part of the paris basin france were characterised using 3 h 14 c and 36 cl and noble gases tracers to evaluate their residence times and determine their recharge period this information is an important prerequisite to evaluating the confinement properties of the callovo oxfordian clay formation sandwiched between the oxfordian aquifer and the dogger aquifer currently being investigated by the french nuclear waste management agency andra for radioactive waste disposal data presented in this paper are used to test 4 hypotheses 1 the oxfordian limestone is isolated from the overlying tithonian kimmeridgian surface aquifer this first hypothesis is supported by the presence of measurable 3 h activities in groundwaters from the surface aquifer 6 11 tu and by its absence in groundwaters derived from deeper aquifers 2 the callovo oxfordian clay sequence in the vicinity of the url serves as an effective barrier to advective flow and transport between the underlying upper dogger aquifer and the overlying oxfordian limestone aquifer this second hypothesis is supported by relatively low concentrations of cl 3 5 78 mg l 1 na 15 145 mg l 1 br 0 08 0 4 mg l 1 and 4 he rad 0 2 2 3 ccstp g 1 and slightly higher 36 cl cl ratios 2 7 59 10 15 at at 1 in groundwaters from the oxfordian aquifer compared to those from the upper dogger aquifer 345 4027 mgcl l 1 402 2390 mgna l 1 1 8 22 2 mgbr l 1 1 6 37 2 ccstp he g 1 1 5 10 15 at 36 cl at 1 cl 3 groundwaters from the oxfordian aquifer in the vicinity of url are pre holocene with residence times exceeding 10 ka geochemical and isotopic lines of evidence for this hypothesis include a 13 c values measured on oxfordian aquifer waters that are close to 13 c of the aquifer matrix reflecting strong isotopic exchange over several thousand years b noble gas temperatures that indicate recharge temperatures between 3 and 8 6 c lower by 2 7 c than the modern average temperature in this area c radiogenic 4 he concentrations between 0 16 10 5 and 2 3 10 5 ccstp g 1 of water about 2 3 orders of magnitude greater than the 4 he concentration of air equilibrated water 4 groundwater residence time for the upper dogger aquifer in the vicinity of the url probably exceed several hundred thousand years such long residence times are indicated by the accumulation of radiogenic he up to 37 10 5 ccstp g 1 assuming a closed system primary contributors to uncertainties in interpretation of the data presented in this paper are the lack of well defined 36 cl cl input ratio knowledge about the 4 he rad sources for oxfordian and dogger aquifers knowledge about transport processes occurring through the dogger aquifer and the extensive dilution of initial 14 c activities by dissolution exchange with aquifer matrix overall however although the data presented in this paper remain semi quantitative due to inevitable intrinsic limitations of the methods none contradict the hypotheses of long residence times and aquifer isolation in the vicinity of the url

the cuyama strike slip basin california u s a an exemplar of contrasting syntectonic and post tectonic strata abstract miocene strata in the cuyama basin of southern california exemplify syntectonic and post tectonic stratigraphic development in a strike slip basin integrated seismic well log and outcrop data provide a detailed portrayal of the seismic stratigraphy and sedimentary facies in the previously unstudied middle and upper miocene sequences results show sharp contrast among syntectonic and post tectonic strata from composition and texture of sediments to lateral distribution and thickness of facies seven post tectonic sequences were mapped across the basin sequences contain eolian to fluvial terrestrial facies wave and tide dominated nearshore facies biosiliceous dolomitic and phosphatic outer shelf and slope mudstones and shale rich submarine fans in basinal environments authigenic dolomites and phosphates are pervasive in outer shelf and slope facies and indicate the possibility of restricted sediment supply post tectonic sequences are thin but laterally continuous and they exhibit little depositional asymmetry minor erosion is distributed equally among regressive and transgressive relative sea level changes asynchronous changes in tectonism sediment supply and eustatic sea level change created dramatic differences among syntectonic and post tectonic sequences interbasinal tectonic quiescence led to the abrupt end of stratigraphic mismatches and the accumulation of sediment during brief episodic periods multiple points of progradation persisted through several million years of post tectonic basin development and highlight the importance of extrabasinal sediment supply to the development of all sequences the eventual loss of most accommodation space promoted the importance of eustatic sea level change and reduced the prominence of asymmetric facies and abrupt lateral facies changes

geochemical evidence for efficient aquifer isolation over geological timeframes aquitards layers of rock having low permeability have been suggested as potential long term reservoirs for toxic materials such as nuclear or chemical waste but information about the isolation properties of aquitard layers is essential to evaluate whether they can indeed be used safely as reservoirs here we investigate the long term mobility of groundwaters between two aquifers surrounding an aquitard layer in the eastern recharge area of the paris basin france using helium isotopes as a geochemical tracer the deeper trias sandstone aquifer which lies above the crystalline basement accumulates radiogenic 4he and primordial 3he from large regions of the crust and mantle at rates comparable to the degassing of the whole crust1 and of mid ocean ridges2 we show that the overlying carbonate dogger aquifer which is separated from the trias aquifer by an aquitard layer consisting of a 600 m succession of shales and clays is stagnant and has been extremely well isolated from the trias over the past several million years this finding together with previous studies at the centre of the paris basin3 4 shows that diffusive mass transfer across aquitards is negligible and that cross formational flow in basins takes place preferentially in faulted areas

geomagnetic modulation of the 36cl flux in the grip ice core greenland geomagnetic field strength is expected to affect the production rate of cosmogenic isotopes such as beryllium 10 carbon 14 or chlorine 36 chlorine 36 data from the greenland ice core project grip ice core agree well with a production rate calculation based on a paleomagnetic reconstruction for the past 100 000 years over both long and short term variations a chlorine 36 peak at 38 000 years ago previously found in the beryllium 10 record from the vostok ice core can be explained by a period of low geomagnetic field intensity

atmosphere derived noble gas evidence for the preservation of ancient waters in sedimentary basins hydrological modeling of the middle jurassic carbonate aquifer of the paris basin indicated fluid residence time from 1 k y to 100 k y whereas the chemistry of waters suggested longer residence time here we report independent water age estimates on the basis of atmosphere derived noble gas recharge paleotemperatures the calculated paleotemperatures range from 15 to 26 c and are related to the stable isotope composition and the salinity of the waters and the distance from the recharge the spatial distribution of the paleotemperatures suggests 1 occurrence of old saline waters in the center of the basin which infiltrated during the warmer climate interval in the tertiary eocene and 2 dilution by recent fresh waters early pleistocene flowing from the recharge these results strongly suggest that deep aquifers in sedimentary basins can store waters for very long periods of time in contrast to the conclusions reached from hydrological modeling

helium isotope fluxes and groundwater ages in the dogger aquifer paris basin the dogger aquifer of the paris basin has been shown to be first order homogeneous in its helium concentration and its helium isotopic ratio although slight differences are noted in relation to specific chemical water types the helium isotopic composition of the dogger aquifer contains a small component of mantle helium that is associated with a magmatic input although the heat accompanying this magma is small constraints on the age of the overlying albien aquifer are used to calculate the flux of helium out of the dogger this constraint allows a calculation of the residence time of waters in the dogger aquifer of 4 myr 50 which is significantly longer than estimates derived from hydrologic models and hydrologic testing it is possible that the hydrologic ages and the helium ages can be reconciled by a vertically layered dogger aquifer with gradients in he salinity and fluid flow vertical profiles of fluid composition helium concentration and permeability are required in the paris basin to resolve this question

the origin of helium in deep sedimentary aquifers and the problem of dating very old groundwaters noble gases inert elements having isotopes produced by the decay of long half life radionuclides offer a powerful approach for tracing fluid circulation and dating groundwaters the u th 4he water ages calculated from the accumulation rate in water of radiogenic 4he produced by decay of u and th contained in the aquifer rocks is frequently higher than the hydrological ages this discrepancy is generally interpreted by two contrasting models i heterogeneities of the aquifers which allow water stagnation and accumulation of large amounts of radiogenic 4he or ii addition of 4he produced in deeper regions of the continental crust in this contribution we propose that the apparent contrast between u th 4he ages and hydrological ages in the paris basin reflects the mixing of different types of water having different residence times we show using the helium isotopic signatures of waters that this mixing occurs between three aquifers the middle jurassic the triassic and the palaeozoic basement which have contrasting helium contents and heterogeneous chemical compositions and permeabilities the difference of radiogenic 4he 4 ratios between the aquifers of triassic and middle jurassic strongly suggests that a significant fraction of helium is produced in the aquifer rocks this implies residence times for groundwaters circulating in the middle jurassic carbonate aquifer much longer than those obtained from hydrological studies independent fluid age estimates based on the ground palaeotemperatures recorded in the same groundwaters by the atmospherederived noble gases seem to confirm the presence of very old groundwaters in the paris basin the estimation of the residence time of ancient groundwaters is the most challenging problem in basin hydrology e g chapman 1987 typical water residence times of 104 108 years outreach the range of half lives of most of the geochronometers available in hydrology e g 3h 14c and prolonged water rock interactions alter the chemical and isotopic signature of water preventing the identification of the fluid sources on the other hand hydrological modelling faces serious problems of estimating space and time variations of critical parameters such as the permeability due to the petro physical heterogeneities of the aquifers and fluid velocity estimates can be valid only on a local scale e g alexander et al 1987 because noble gases are inert and have isotopes produced by natural decay of long halflife radionuclides these elements have received increasing attention as tracers of groundwater movements in deep aquifers e g marine 1979 andrews et al 1982 1985 bottomley et at 1984 1990 torgersen clarke 1985 zaikowski et al 1987 ballentine et al 1991 stute et al 1992 marty et al 1993 o nions ballentine 1993 groundwaters contain noble gases derived from the atmosphere the crust and the mantle fig 1 studies on water dating are focused mainly on the crustal derived radiogenic noble gas component for obvious reasons although the mantle derived component has the capacity of tracing fluid sources oxburgh et al 1986 and the atmosphere derived component can provide independent estimates on the water residence times pinti et al 1997 in continental environments mantle derived noble gases are generally observed in regions of active volcanism or extensional tectonics ballentine et al 1991 the source is probably sub continental magma intrusion and underplating with successive episodic and tectonically controlled advective transport in the crust torgersen 1993 mantle derived helium can be easily identified from its isotopic signature indeed the mantle is enriched in primordial 3he as indicated by 3he 4he ratios greater than 10 5 whereas the atmospheric ratio is l a x 10 6 and crustalderived radiogenic helium has 3he 4he ratios in the range of 10 8 consequently the geographical distribution of the 3he 4he ratios in sedimentary fluids can be used to identify the fluids pinti d l marty b 1998 the origin of helium in deep sedimentary aquifers and the problem of dating very old groundwaters in parnell j ed 1998 dating and duration of fluid flow and fluid rock interaction geological society london special publications 144 53 68 by guest on january 5 2014 http sp lyellcollection org downloaded from

knowledge of the three french underground laboratory sites abstract from march 1994 to august 1996 andra conducted a large reconnaissance work on three sites for possible underground research laboratories these surveys highlighted for each site the presence of a geological formation the properties of which meet the requirements of the french fundamental safety rules on the east site the selected formation is a 130 m thick argillite layer on the gard site the layer is composed of close packed siltites which are 200 400 m thick on the vienne site a hercynian granodiorite batholith was found under a 160 m thick jurassic overdurden

noble gas composition of deep brines from the palo duro basin texas deep groundwaters in sedimentary basins can be sufficiently old 10 m y to have accumulated both radiogenic 4he and 40ar differences in the ratio of u th k for aquifer lithologies lead to variations for 4he40ar in the groundwater these variations can be used to resolve chronologically significant noble gas components application of a binary model to brine samples from the palo duro basin texas yields u th 4he residence times of 100 to 300 m y concentrations of two non radiogenic noble gases 20ne and 36ar provide information on the salinities of the water that recharged these aquifers

a 190 drop in atmosphere s δ14c during the mystery interval 17 5 to 14 5 kyr reconstructions of atmospheric 14c for the deglacial period reveal a 190 10 drop between 17 5 and 14 5 kyr before present during the mystery interval while it appears that the major contributor must be the mixing between an isolated low radiocarbon abyssal reservoir and the remainder of the ocean a combination of 14c measurements on coexisting benthic and planktic foraminifera shells and 13c 12c measurements on benthic foraminifera make it difficult to identify a sufficiently large volume for this reservoir an alternative scenario based on higher 14c production rates between about 38 and 18 kyr ago would escape the need for a large isolated reservoir prior to the mystery interval but instead would call for a better ventilated ocean afterwards the addition of 14c deficient sedimentary carbon appears not to be an important contributor while the unlikely explanation that the half life of 14c is 15 greater than the accepted value 5730 yr would eliminate the steady decrease in the 14c c over the last 40 kyr it would not explain the steep drop which occurred between 17 5 and 14 5 kyr

modeling complex flow structures and drag around a submerged plant of varied posture although vegetation is present in many rivers the bulk of past work concerned with modeling the influence of vegetation on flow has considered vegetation to be morphologically simple and has generally neglected the complexity of natural plants here we report on a combined flume and numerical model experiment which incorporates time averaged plant posture collected through terrestrial laser scanning into a computational fluid dynamics model to predict flow around a submerged riparian plant for three depth limited flow conditions reynolds number 65 000 110 000 plant dynamics were recorded through high definition video imagery and the numerical model was validated against flow velocities collected with an acoustic doppler velocimeter the plant morphology shows an 18 reduction in plant height and a 14 increase in plant length compressing and reducing the volumetric canopy morphology as the reynolds number increases plant shear layer turbulence is dominated by kelvin helmholtz type vortices generated through shear instability the frequency of which is estimated to be between 0 20 and 0 30 hz increasing with reynolds number these results demonstrate the significant effect that the complex morphology of natural plants has on in stream drag and allows a physically determined species dependent drag coefficient to be calculated given the importance of vegetation in river corridor management the approach developed here demonstrates the necessity to account for plant motion when calculating vegetative resistance

climate and groundwater recharge during the last glaciation in an ice covered region a multitracer study of a small aquifer in northern switzerland indicates that the atmosphere in central europe cooled by at least 5 c during the last glacial period the relation between oxygen isotope ratios 18o and recharge temperatures reconstructed for this period is similar to the present day one if a shift in the 18o value of the oceans during the ice age is taken into account this similarity suggests that the present day 18o temperature relation can be used to reconstruct paleoclimate conditions in northern switzerland a gap in calculated groundwater age between about 17 000 and 25 000 years before the present indicates that during the last glacial maximum local groundwater recharge was prevented by overlying glaciers

mixing layers and coherent structures in vegetated aquatic flows 1 to date flow through submerged aquatic vegetation has largely been viewed as perturbed boundary layer flow with vegetative drag treated as an extension of bed drag however recent studies of terrestrial canopies demonstrate that the flow structure within and just above an unconfined canopy more strongly resembles a mixing layer than a boundary layer this paper presents laboratory measurements obtained from a scaled seagrass model that demonstrate the applicability of the mixing layer analogy to aquatic systems specifically all vertical profiles of mean velocity contained an inflection point which makes the flow susceptible to kelvin helmholtz instability this instability leads to the generation of large coherent vortices within the mixing layer observed in the model at frequencies between 0 01 and 0 11 hz which dominate the vertical transport of momentum through the layer the downstream advection of these vortices is shown to cause the progressive coherent waving of aquatic vegetation known as the monami when the monami is present the turbulent vertical transport of momentum is enhanced with turbulent stresses penetrating an additional 30 of the plant height into the canopy

analytical solution of the depth averaged flow velocity in case of submerged rigid cylindrical vegetation a new model for the depth averaged velocity for flow in presence of submerged vegetation is developed the model is based on a two layer approach where flow above and through the vegetation layer is described separately vegetation is treated as a homogeneous field of identical cylindrical stems and the flow field is considered stationary and uniform it is demonstrated that scaling considerations of the bulk flow field can be used to avoid complications associated with smaller scale flow processes and that still the behavior of depth averaged flow over vegetation is described accurately the derived scaling expression of the average flow field is simple in form it follows fundamental laws of fluid flow and it shows very good agreement with laboratory flume experiments the new model can be used for quick evaluation of a river s hydraulic response in cases where vegetated floodplains are inundated

age and recharge pattern of water in the oligocene of the mazovian basin poland as indicated by environmental tracers abstract controversies exist about the recharge pattern age and renewal rate of water in the oligocene sands of the mazovian basin poland hydrodynamic modelling yields ages of about 1 5 ka whereas earlier estimates based on environmental tracer methods suggested from 30 ka to more than 200 ka this age discrepancy mainly resulted from apparent inconsistency of environmental isotope data and partly from unidentified flow paths sparse data and poor knowledge about the hydrodynamic parameters of the overlying pliocene sediments however in spite of 18 o and d values only slightly lighter than those typical for local holocene waters low inferred noble gas temperatures obtained within this study 0 3 4 9 c in comparison with the present air temperature of 7 5 c and low 14 c contents 0 7 pmc indicate a dominant role of glacial recharge the isotope shifts to heavier values and to the right of w m w l which decrease the difference between the holocene and glacial waters are caused by evaporation prior to recharge via numerous paleolakes and by admixture of ascending saline water though several earlier 36 cl analyses suggest ages of the order of 200 ka such great ages are excluded by 40 ar 36 ar ratios close to the atmospheric equilibrium and relatively low 4 he excess values obtained within the present study a good correlation of 4 he excess with cl content indicates its origin to be related mainly to local ascension of older waters and to be little depended on the radiogenic production within the aquifer or to the accumulation of crustal flux along the flow paths therefore the noble gas data have appeared to be indispensable for the identification of the glacial age of water far from erosion windows in spite of weak 18 o and d climatic signal and for confirmation of a conceptual model invoking significant vertical recharge by leakage through pliocene sediments