conduit enlargement in an eogenetic karst aquifer summary most concepts of conduit development have focused on telogenetic karst aquifers where low matrix permeability focuses flow and dissolution along joints fractures and bedding planes however conduits also exist in eogenetic karst aquifers despite high matrix permeability which accounts for a significant component of flow this study investigates dissolution within a 6 km long conduit system in the eogenetic upper floridan aquifer of north central florida that begins with a continuous source of allogenic recharge at the santa fe river sink and discharges from a first magnitude spring at the santa fe river rise three sources of water to the conduit include the allogenic recharge diffuse recharge through epikarst and mineralized water upwelling from depth results of sampling and inverse modeling using phreeqc suggest that dissolution within the conduit is episodic occurring only during 30 of 16 sampling times between march 2003 and april 2007 during low flow conditions carbonate saturated water flows from the matrix to the conduit restricting contact between undersaturated allogenic water with the conduit wall when gradients reverse during high flow conditions undersaturated allogenic recharge enters the matrix during these limited periods estimates of dissolution within the conduit suggest wall retreat averages about 4 10 6 m day in agreement with upper estimates of maximum wall retreat for telogenetic karst because dissolution is episodic time averaged dissolution rates in the sink rise system results in a wall retreat rate of about 7 10 7 m day which is at the lower end of wall retreat for telogenetic karst because of the high permeability matrix conduits in eogenetic karst thus enlarge not just at the walls of fractures or pre existing conduits such as those in telogenetic karst but also may produce a friable halo surrounding the conduits that may be removed by additional mechanical processes these observations stress the importance of matrix permeability in eogenetic karst and suggest new concepts may be necessary to describe how conduits develop within these porous rocks

origin and morphology of limestone caves limestone caves form along ground water paths of greatest discharge and solutional aggressiveness flow routes that acquire increasing discharge accelerate in growth while others languish with negligible growth as discharge increases a maximum rate of wall retreat is approached typically about 0 01 0 1 cm yr determined by chemical kinetics but nearly unaffected by further increase in discharge the time required to reach the maximum rate is nearly independent of kinetics and varies directly with flow distance and temperature and inversely with initial fracture width discharge gradient and pco2 most caves require 104 105 yr to reach traversable size their patterns depend on the mode of ground water recharge sinkhole recharge forms branching caves with tributaries that join downstream as higher order passages maze caves form where 1 steep gradients and great undersaturation allow many alternate paths to enlarge at similar rates or 2 discharge or renewal of undersaturation is uniform along many alternate routes flood water can form angular networks in fractured rock anastomotic mazes along low angle partings or sponge work where intergranular pores are dominant diffuse recharge also forms networks and spongework often aided by mixing of chemically different waters ramiform caves with sequential outward branches are formed mainly by rising thermal or h2s rich water dissolution rates in cooling water increase with discharge co2 content temperature and thermal gradient but only at thermal gradients of more than 0 01 c m can normal ground water co2 form caves without the aid of hypogenic acids or mixing artesian flow has no inherent tendency to form maze caves geologic structure and stratigraphy influence cave orientation and extent but alone they do not determine branch work versus maze character

the origin of solutes within the groundwaters of a high andean aquifer abstract this paper investigates the origin of solutes within the groundwaters of the monturaqui negrillar tilopozo mnt aquifer system within the high andes of the atacama desert that discharges into the salar de atacama key questions include the relative significance of volcanic hydrothermal processes and evaporitic brine recycling over solute supply as well as the pathways of solute ingress to the mnt aquifer system groundwaters were analysed for elemental major minor and trace and isotopic 18o 2h 13c dic 34s so4 87sr 86sr constituents to which various hydrochemical and multivariate statistical methods have been applied groundwaters are all classified as thermal and show increasing temperatures 27 35 c and concentrations of hco3 4 4 10 4 mmol l 1 dissolved inorganic carbon dic with increasing proximity to volcano socompa resulting from an increasing mass flux of steam and magmatic co2 pco2 0 016 to 0 10 atm 13c co2 9 3 to 3 6 v pdb boiled off a deep hydrothermal reservoir superimposed upon this gradational and relatively smooth spatial increase in heat and mass flow is a sharp structurally controlled increase in tds 826 3632 mg l 1 and a concomitant change in 34s so4 0 79 to 4 9 v cdt and 87sr 86sr values 0 707375 0 706859 associated with the inflow of evaporitic solutes evaporitic inputs are chemically and isotopically distinct from localised secondary hydrothermally derived solutes with major minor and trace element data suggesting an origin within a highly oxidising alkaline evaporitic lake receiving dilute inflows enriched in volcanic fumarolic sulfur mineralisation probably from volcanoes socompa salin or pular that delimit the eastern topographic extent of the aquifer system the conceptual model presented in this paper proposes that basal leakage of evaporitic brines from active salar s within the high altiplano volcanic arc are actively entrained by sub regional groundwater flow and conveyed to the mnt aquifer system where they mix with solutes derived from localised secondary hydrothermal gas water rock interaction this work provides detail on the origin and processes controlling the solute composition of groundwater inflows to the salar de atacama within the volcanically active and hyperarid atacama desert and may be of significance to conceptual models of evaporitic brine evolution recycling of evaporitic brines and hydrothermalism in arid regions

hydrology and alkalinity regulation of soft florida waters an integrated assessment natural waters in ridge provinces of florida and southeast georgia were classified geographically by degrees of cultural disturbance and according to the dominant hydrologic and biogeochemical processes controlling chemistry the ionic composition of lakes upland streams and surficial aquifer water table springs in relatively undeveloped catchments reflects the geographic variations in bulk deposition corrected for evapotranspiration na cl plus a slight gain net watershed mobilization of mg and partial to nearly complete losses net retention of nitrate sulfate ca and k recharge to the floridan aquifer in infertile forested sandy ridge provinces of northern florida contains 360 580 mol co2 on the basis of indirect geochemical evidence sulfate retention appears less important in lake sediments than in the region s highly weathered ferruginous kaolinitic sand soils silica concentrations in upland streams and water table springs closely reflect the predicted equilibrium between kaolinite and gibbsite along with other evidence the si concentrations in ridge lakes indicate that seepage inflow is much more important than assumed in baker et al s 1988 regional model lakes and streams are acidified either by humic acids or nonmarine sulfate but rarely by both as reflected by the significant inverse correlation between these two components contrary to previous reports there is no significant difference in alkalinity for culturally undisturbed lakes in the northern trail versus southern highlands ridge areas

geochemical and isotopic evidence of a groundwater source in the corral canyon meadow complex central nevada usa major inorganic ions and stable carbon and oxygen isotopes in stream water groundwater groundwater seeps and springs were measured in the corral canyon meadow complex and watershed in the toquima mountains of central nevada usa the purpose of the study was to determine whether stream water or groundwater was the source of water that supports vegetation in the meadow complex water samples from the watershed and meadow complex were mixed cation hco3 type stream water sampled at different locations in the meadow complex showed variations in temperature ph and specific conductance the cation anion proportions for stream water were similar to groundwater groundwater seeps and runoff from the meadow complex stable oxygen isotope ratios for stream water 17 1 to 17 6 versus vsmow and groundwater and groundwater seeps in the meadow site 17 0 to 17 7 versus vsmow were similar and consistent with a local meteoric origin dissolved inorganic carbon dic and the 13cdic for stream water 12 1 to 15 0 versus vpdb were different from that of groundwater from the meadow complex 15 3 to 19 9 versus vpdb suggesting different carbon evolution pathways however a simple model based on cation 13cdic suggests that stream water was being recharged by shallow groundwater groundwater seeps and runoff from the meadow complex this leads to the conclusion that the source of water that supports vegetation in the meadow complex was primarily groundwater the results of this study suggest that multiple chemical and stable carbon isotope tracers are useful in determining the source of water that supports vegetation in meadow complexes in small alpine watersheds copyright 2004 john wiley sons ltd

strontium isotopes as tracers of groundwater induced floods the somme case study france major ions trace elements and o h and sr isotopes have been determined for surface water and groundwater in the somme catchment northern france the present study using a coupled hydrological and geochemical stable and sr isotopes approach focuses on the interactions between ground and surface water stable water isotopes 18o 2h show that all waters have a purely local origin from precipitation without significant evaporation or water rock interaction as all points plot close to the general meteoric water line water chemistry in the different catchments shows large variations in major element contents plotting na vs cl contents and mg2 no3 k so42 sr2 concentrations reveals a slight variations in groundwater composition b agricultural input into surface waters and c some similarities between ground and surface waters suggesting the former to be responsible for the chemical signature of the dissolved river load strontium isotope ratios measured in groundwater range from 0 70769 to 0 70808 clearly higher than that of chalk matrix water 0 707337 variations of sr isotope signatures in groundwater from the chalk aquifer are significant and help identifying different groundwater bodies the different signatures in groundwater are better explained by matrix heterogeneity which can present lateral facies variations than by a strong anthropogenic influence the sr isotope compositional range in surface waters is very wide varying from 0 70775 to 0 70816 and defining a trend towards a more radiogenic sr isotope signature with high sr contents and high mg sr ratios the relationship between 87sr 86sr and the mg sr ratios allows different end members to be defined the rivers are influenced by anthropogenic disturbance even during flood periods and river water has geochemical characteristics very similar to those of groundwater indicating a strong influence from groundwater feeding the rivers

hydrodynamic and isotopic investigations for evaluating the mechanisms and amount of groundwater seepage through a rockslide dam this study addresses the influence of landslide dams on surface water drainage and groundwater flow in the study area of scanno lake and sagittario river central italy a limestone rockslide avalanche formed a lake which has an outlet that is occasionally active showing infiltration into the rockslide dam several springs are present at the lake s base and are partly fed by seepage through the rockslide debris piezometric surveys discharge measurements pumping tests and chemical analyses are tools used to build a conceptual model of the groundwater flow and to evaluate the flow through the rockslide debris seasonal water isotopic signatures validate the assumed model showing a mixing of infiltration recharge and groundwater seepage throughout the rockslide debris various recharge areas have been found for springs pointing out those directly fed by the rockslide debris aquifer hypotheses about seasonal groundwater mixing between the regional carbonate aquifer and the rockslide debris aquifer are supported by isotope results seasonal changes in groundwater table level due to recharge and surface losses from seasonal outlet have been correlated with isotopic groundwater composition from the rockslide debris aquifer and the downstream springs this relationship highlights the role of the rockslide dam body on the hydrodynamics of the studied area relationships between surface waters and groundwater in the area have been completely understood on the basis of water isotopic fingerprinting finally obtaining a complete evaluation of groundwater renewable resources and its regimen copyright 2010 john wiley sons ltd

geochemical and statistical evidence of recharge mixing and controls on spring discharge in an eogenetic karst aquifer summary information about sources of recharge distributions of flow paths and the extent of water rock reactions in karst aquifers commonly result from monitoring spring chemistry and discharge to investigate the relationship between spring characteristics and the complexities of karst aquifers we couple variations in surface and groundwater chemistry to physical conditions including river stage precipitation and evapotranspiration et within a sink rise system through a 6 km portion of the upper floridan aquifer ufa in north central florida principal component analysis pca of time series major element compositions suggests that at least three sources of water affect spring discharge including allogenic recharge into a swallet diffuse recharge through a thin vadose zone and water upwelling from deep within the aquifer the deep water source exerts the strongest influence on water chemistry by providing a majority of na mg2 k cl and so 4 2 to the system anomalously high temperature at one of several monitoring wells reflects vertical flow of about 1 m year mass balance calculations suggest diffuse recharge and deep water upwelling can provide up to 50 of the spring discharge however their contributions depend on head gradients between the conduit and surrounding aquifer matrix which are influenced by variations in precipitation et and river stage our results indicate that upwelling from deep flow paths may provide significant contributions of water to spring discharge and that monitoring only springs limits interpretations of karst systems by masking critical components of the aquifer such as water sources and flow paths these results also suggest the matrix in eogenetic aquifers is a major pathway for flow even in a system dominated by conduits

the combined use of 87sr 86sr and carbon and water isotopes to study the hydrochemical interaction between groundwater and lakewater in mantled karst abstract the hydrochemical interaction between groundwater and lakewater influences the composition of water that percolates downward from the surficial aquifer system through the underlying intermediate confining unit and recharges the upper floridan aquifer along highlands in florida the 87sr 86sr ratio along with the stable isotopes d 18o and 13c were used as tracers to study the interaction between groundwater lakewater and aquifer minerals near lake barco a seepage lake in the mantled karst terrane of northern florida upgradient from the lake the 87sr 86sr ratio of groundwater decreases with depth mean values of 0 71004 0 70890 and 0 70852 for water from the surficial aquifer system intermediate confining unit and upper floridan aquifer respectively resulting from the interaction of dilute oxygenated recharge water with aquifer minerals that are less radiogenic with depth the concentrations of sr2 generally increase with depth and higher concentrations of sr2 in water from the upper floridan aquifer 20 35 g l relative to water from the surficial aquifer system and the intermediate confining unit result from the dissolution of sr bearing calcite and dolomite in the eocene limestone dissolution of calcite 13c 1 6permil is also indicated by an enriched 13cdic 8 8 to 11 4 in water from the upper floridan aquifer relative to the overlying hydrogeologic units 13cdic groundwater downgradient from lake barco was enriched in18o and d relative to groundwater upgradient from the lake indicating mixing of lakewater leakage and groundwater downgradient from the lake the 87sr 86sr ratio of groundwater and aquifer material become less radiogenic and the sr2 concentrations generally increase with depth however sr2 concentrations are substantially less than in upgradient groundwaters at similar depths the lower sr2 concentrations result from the influence of anoxic lakewater leakage on the mobility of sr2 from clays based on results from mass balance modeling it is probable that cation exchange plays the dominant role in controlling the 87sr 86sr ratio of groundwater both upgradient and downgradient from lake barco even though groundwater from the three distinct hydrogeologic units displays considerable variability in sr concentration and isotopic composition the dominant processes associated with the mixing of lakewater leakage with groundwater as well as the effects of mineral water interaction can be ascertained by integrating the use of stable and radiogenic isotopic measurements of groundwater lakewater and aquifer minerals

formation of phreatic caves in an eogenetic karst aquifer by co2 enrichment at lower water tables and subsequent flooding by sea level rise formation of extensive phreatic caves in eogenetic karst aquifers is widely believed to require mixing of fresh and saltwater extensive phreatic caves also occur however in eogenetic karst aquifers where fresh and saltwater do not mix for example in the upper floridan aquifer these caves are thought to have formed in their modern settings by dissolution from sinking streams or by convergence of groundwater flow paths on springs alternatively these caves have been hypothesized to have formed at lower water tables during sea level low stands these hypotheses have not previously been tested against one another analyzing morphological data and water chemistry from caves in the suwannee river basin in north central florida and water chemistry from wells in the central florida carbonate platform indicates that phreatic caves within the suwannee river basin most likely formed at lower water tables during lower sea levels consideration of the hydrological and geochemical constraints posed by the upper floridan aquifer leads to the conclusion that cave formation was most likely driven by dissolution of vadose co2 gas into the groundwater sea level rise and a wetter climate during the mid holocene lifted the water table above the elevation of the caves and placed the caves tens of meters below the modern water table when rising water tables reached the land surface surface streams formed incision of surface streams breached the pre existing caves to form modern springs which provide access to the phreatic caves phreatic caves in the suwannee river basin are thus relict and have no causal relationship with modern surficial drainage systems neither mixing dissolution nor sinking streams are necessary to form laterally extensive phreatic caves in eogenetic karst aquifers dissolution at water tables potentially driven by vadose co2 gas offers an underappreciated mechanism to form cavernous porosity in eogenetic carbonate rocks copyright 2012 john wiley sons ltd

contaminant sequestration in karstic aquifers experiments and quantification 1 a karstic aquifer typically has significant secondary porosity consisting of an interconnected system of caves or conduits conduit borne contaminants can enter the contiguous limestone matrix remain inside for a longer time than in the conduit and subsequently be flushed out this retention or sequestration can significantly influence the fate of contaminants within the aquifer and alter the shape of the breakthrough curve the mechanisms involved in sequestration have been identified and quantified by analysis of the breakthrough curves generated by a set of laboratory experiments in which a conduit porous limestone matrix and conservative contaminant were simulated by a porous walled pipe chamber of closely packed glass beads and salt respectively experiments were conducted with both active and passive transfer of water between conduit and matrix simulating differing hydrogeologic regimes in active transfer the primary control parameter is the volume of water transferred sequestration is primarily due to advection with the effects of diffusion and dispersion being minimal in passive transfer the control parameters are the conduit reynolds number and the duration that contaminant resides in the conduit sequestration is caused by the combined effects of the conduit pressure drop pressure variation due to bedform and diffusion active and passive transfer can be unified by analyzing the ratio of the scale of pressure variation to the conduit length in accordance with the resolved mechanisms a variety of models have been constructed to recover solute distributions in the matrix and to regenerate breakthrough curves these analyses and models provide a potential approach to investigate contaminant migration in karstic aquifers

chemical evolution of groundwater near a sinkhole lake northern florida 1 flow patterns age of groundwater and influence of lake water leakage leakage from sinkhole lakes significantly influences recharge to the upper floridan aquifer in poorly confined sediments in northern florida environmental isotopes oxygen 18 deuterium and tritium chlorofluorocarbons cfcs cfc 11 ccl3f cfc 12 ccl2f2 and cfc 113 c2cl3f3 and solute tracers were used to investigate groundwater flow patterns near lake barco a seepage lake in a mantled karst setting in northern florida stable isotope data indicated that the groundwater downgradient from the lake contained 11 67 lake water leakage with a limit of detection of lake water in groundwater of 4 3 the mixing fractions of lake water leakage which passed through organic rich sediments in the lake bottom were directly proportional to the observed methane concentrations and increased with depth in the groundwater flow system in aerobic groundwater upgradient from lake barco cfc modeled recharge dates ranged from 1987 near the water table to the mid 1970s for water collected at a depth of 30 m below the water table cfc modeled recharge dates based on cfc 12 for anaerobic groundwater downgradient from the lake ranged from the late 1950s to the mid 1970s and were consistent with tritium data cfc modeled recharge dates based on cfc 11 indicated preferential microbial degradation in anoxic waters vertical hydraulic conductivities calculated using cfc 12 modeled recharge dates and darcy s law were 0 17 0 033 and 0 019 m d for the surficial aquifer intermediate confining unit and lake sediments respectively these conductivities agreed closely with those used in the calibration of a three dimensional groundwater flow model for transient and steady state flow conditions

bank storage in karst aquifers the impact of temporary intrusion of river water on carbonate dissolution and trace metal mobility abstract storms can trigger changes in river stage that alter the hydraulic gradients between rivers and adjacent aquifers in eogenetic carbonate karst aquifer systems storms enable river water to intrude 1 km into the adjacent aquifer systems for days to weeks this process is similar to bank storage of streams in siliciclastic sediments but can have longer temporal and larger spatial scales river intrusion triggers changes in mineral saturation states and redox conditions in the aquifer due to the input of low ph low specific conductivity spc and high dissolved organic carbon doc flood water to assess the effects of river intrusion into karst aquifers we measured spc temperature ph redox state and concentrations of dissolved major and trace elements through an intrusion event at madison blue spring in northern florida usa river water displaced groundwater in the conduit at least 1 km into the aquifer and flowed into the pores of the unconfined aquifer matrix distinct cl concentrations between river water and groundwater provide estimates for mixing fractions the location and magnitude of oxidation of organic matter in the subsurface controlled trace metal concentration redox state and saturation state of the water with respect to calcite sical organic matter oxidation in the phreatic conduits was limited by the terminal electron acceptors teas present in the conduit water calcite dissolution and trace metal sorption were limited by the lower surface area to porosity ratios in the conduits than the matrix organic matter oxidation was enhanced in the matrix by mixing with matrix waters with available do and no3 resulting in greater co2 production and calcite dissolution than in the conduit after the intruded river water discharged conditions remained more reducing in the aquifer than baseflow conditions due to the reduction of do and no3 in the matrix water the organic matter transported into the aquifer during river intrusion drives carbonate dissolution alters redox state and impacts trace metal mobility impacting groundwater and surface water quality

groundwater in sudan an improved understanding of wadi directed recharge abstract like many dryland regions around the world the butana region of sudan is almost entirely dependent on groundwater and its main source of recharge comes from the highly variable 150 200 mm yr rain that arrives mostly during a three month rainy season these rains cause ephemeral wadis to flow and flood and provide a critical component of shallow aquifer replenishment this study uses water table fluctuations along a 20 km wadi reach and chemical and stable isotopic tracers in 27 shallow in the 1980s conjunctive use of major and trace geochemistry isotope and physical hydrology in the study of wadi recharge was only beginning to gain traction as a sub discipline and the study of edmunds et al 1987 in the abu delaig area paved the way for hydrogeochemical studies in unmonitored dryland catchments around the world thirty years on from that study the local population has grown tenfold water extraction has increased to accommodate mining and an upstream dam has been built this study conducted in a 400 km2 subset of the original lower atbara basin study answers a previously unanswered question about wadi recharge to the deeper nubian sandstone aquifer unit and offers a unique three decade perspective on groundwater development in a rural arid environment expanding beyond its margin of groundwater sustainability

sources of recharge at abu delaig sudan abstract various components of the water cycle in and around abu delaig a small town in a semiarid region of sudan have been investigated with geochemical and isotopic techniques to determine the sources of groundwater recharge rain samples total deposition during storms contain significant concentrations of dissolved solids for a continental site mean 4 6 mgl 1 for 1982 1985 the heaviest rains important for recharge tend to have the lowest chlorinities and are also the most negative isotopically wadi floods generally have lower chlorinity than the rainfall indicating the proportionally lower amounts of dust in the more intense rainfall events shallow ground waters at abu delaig have relatively evolved compositions higher mg ca ratios compared with rainfall and wadi floods yet they also contain tritium and retain isotopic signatures similar to the local rainfall they also have a distinctive chemistry compared with the deeper ground waters in the region and recharge from the former to the latter is considered to be insignificant ground waters in the unsaturated zone are saline and have isotopic compositions highly enriched in heavy isotopes compared with rainfall indicating strong evaporation the chloride balance indicates that mean recharge rates are 0 2 1 3 mm year 1 through the interfluve areas it is concluded that the only significant replenishable resources at abu delaig are from wadi recharge during floods and that direct regional recharge is insignificant fluctuations in the water table however lead to solutes from the lower unsaturated zone contributing to the chemistry of the shallow ground waters elsewhere it is possible that wadi recharge may be a possible route for deeper replenishment but this needs to be demonstrated by dedicated experiments

magnetotactic bacteria and single domain magnetite in hemipelagic sediments remanent magnetism in marine sediments has been used extensively over the past twenty years to calibrate the geological time scale study geomagnetic reversals and secular variation and measure the rates of seafloor spreading although these sediments may contain different magnetic minerals magnetite is the most commonly observed and magnetically stable phase and its size shape and post depositional fate affect the magnetic remanence of the sediments biogenic magnetites are single domain with a high natural magnetic remanence nrm and have been suggested as a significant source of magnetic remanence in marine sediments we have studied surface sediments from the santa barbara basin and report the occurrence of living magnetotactic bacteria and the deposition of biogenic ultra fine grained single domain magnetite using a novel extraction technique transmission electron microscopy and squid magnetometry we show that these bacteria and the magnetite they produce are the major source of stable remanent magnetism in these sediments

sediment carbon fate in phreatic karst part 2 numerical model development and application abstract the authors develop a numerical model to elucidate time distributed processes controlling sediment carbon fate in phreatic karst sediment carbon processes simulated in the new numerical model include in conduit erosion and deposition sediment carbon transport surficial fine grained laminae evolution carbon pool mixing microbial oxidation and the understudied process of sediment carbon exchange during equilibrium transport the authors perform a model evaluation procedure that includes generalized likelihood uncertainty estimation to quantify uncertainty of the model results modeling results suggest that phreatic karst conduits sustain sediment transport activity long after surface storm events cease the sustained sediment transport has the potential to shift the baseflow sediment yield of the phreatic karst to be on par with stormflow sediment yield the sustained activity is suggested to promote the exchange of sediment carbon between the water column and subsurface karst deposits during equilibrium sediment transport conditions in turn the sediment carbon exchange impacts the mixing of new and old carbon pools and the flux of carbon from phreatic karst integrated numerical model results from this study support the concept that phreatic karst act as a biologically active conveyor of sediment carbon that temporarily stores sediment turns over carbon at higher rates than surface streams and recharges degraded carbon back to the fluvial system the numerical modeling method adopted in this paper shows the efficacy of coupling carbon isotope fingerprinting with water quality modeling to study sediment carbon in phreatic karst

using ground penetrating radar to investigate a subsurface karst landscape in north central florida abstract doline formation in karst areas has been a major concern in florida recently there has been increased interest in investigating the subsurface conditions that influences preferential flow in these karst landscapes this information is necessary to improve transport and fate models of contaminants in addition there is interest in knowing if the formation and expansion of dolines can be predicted by studying subsurface conditions and flow patterns the soils on the newberry limestone plain are typically sandy above a thin or absent phosphatic clayey hawthorne formation underlying this formation is the crystal river limestone a field survey with ground penetrating radar gpr was conducted on the newberry limestone plain at a site with recently formed dolines the objectives were i to investigate the subsurface materials ii to ascertain subsurface landscape variability iii to relate the subsurface landscapes to subsurface flow patterns and iv to predict doline growth and formation in the study area the results of this study indicated that the subsurface features presence of clay over limestone location of solution pipes and paleo dolines are variable in general the subsurface landscape does not follow the surface topography subsurface solute movement can be estimated in these landscapes assuming the clay layer that drapes the limestone acts as an aquatarde thus subsurface modeling of flow at the study site is improved locations of paleo dolines and solution pipes were obvious in the radar data predictions though of future doline formation and growth at the study site were difficult with gpr fracture patterns e g dips in the limestone can be evaluated and weak zones where paleo dolines have formed can be identified this study would not have been possible without the use of the gpr the radar was able to obtain continuous information on 16 of the site to a depth of 3 m a highly detailed soil survey using conventional methods would have provided only 0 8 coverage of the site

simple transport models for karst systems abstract tracer tests are useful field methods with a wide range of applications in karst aquifers the measured tracer breakthrough curve at a karst spring allows the estimation of the important transport properties of the karst system the breakthrough curve is typically characterized by a long tailing and a low tracer recovery that is not captured by the classical one dimensional advection dispersion model partitioning models are often used and require a large number of parameters in the present work simplified transport models are proposed to simulate the typical karst breakthrough curve the model setup consists of a karst conduit that is interacting laterally with the surrounding matrix the solute transport in both the conduit and matrix are governed by the one dimensional advection dispersion equation and the resulting mathematical model consists of a coupled system of differential equations the laplace transform method is used to derive the transport models for various flow and boundary conditions the models are in terms of four physically meaningful parameters that represent the advection and dispersion properties of the flow in the conduit and matrix algebraic relationships to estimate the model parameters are also derived in terms of the key features of the breakthrough curves the main advantage of the proposed models are their simple formulation and ability to capture the long tailing of the breakthrough curve in terms of just a few parameters application of the models to two real karst aquifers demonstrate their effectiveness in simulating the observed breakthrough curves and estimating the key transport parameters

borehole magnetostratigraphy absolute age dating and correlation of sedimentary rocks with examples from the paris basin france total and cea have conceived and developed two new logging tools which allow continuous precise and accurate in situ magnetic measurements within weakly magnetized sedimentary rocks encountered in uncased industry drilled wells the combination of these magnetic measurements permits for the first time continuous determination of natural remanent magnetization nrm polarities occurring in the logged section the resulting well magnetostratigraphic sequence wms which may be recognized from well to well magnetostratigraphic correlations may also be correlative to a geomagnetic polarity time scale gpts or reference magneto stratigraphic scale rms given adequate dating tie points and lack of noticeable remagnetizations application of this method to the upper jurassic formation in four wells of the paris basin has yielded promising results for both stratigraphic and near absolute age correlations as well as determination of facies diachronisms the comparison of results obtained from magnetic measurements and from sequence stratigraphy analysis shows that third order sequence boundaries may be correlative to geomagnetic reversals but may also be diachronous in wells 80 km or less apart the potential of borehole magnetic measurements as presented in this paper is still under investigation however these encouraging initial results show that this new investigating and dating method could be of great help in the analysis of subsurface stratigraphy by extending the concepts of magnetostratigraphy from the outcrops and laboratory directly into borehole logging

anomalous magnetic properties in rocks containing the mineral siderite paleomagnetic implications sampling and magnetic measurement of a 1 m bed in a new road cut of the upper cretaceous austin chalk northeastern texas has yielded anomalous magnetic results initial measurement of the anisotropy of magnetic susceptibility ams indicated unusually high anisotropies and low bulk susceptibilities characteristic of a magnetocrystalline anisotropy which might be expected for siderite feco3 natural remanent moments nrm for these samples were low 1 10 4 a m2 and directions were typical for samples which had acquired a normal geomagnetic field overprint at the site periodic remeasurement of the nrm yielded an increase in moment for some samples and periodic reversals of rm in a direction parallel or antiparallel to the ambient field in the laboratory isothermal remanent moments of these samples saturates at low induction values 200 mt ams remeasurement over a period of weeks to months revealed a general decrease in the anisotropy magnitudes an increase in susceptibility and a change in principal axis orientations these data were compared with heating oxidation experiments on austin chalk siderite ore and clastic sediments with siderite cements all of these results are consistent with the x ray diffraction and mossbauer data which indicate the presence of siderite in the austin chalk samples the mossbauer spectra of the samples obtained at room temperature and 78 k indicate the presence of approximately 80 pyrite 10 siderite and 10 of a clay component possibly chlorite when only the iron bearing mineral components are considered after sampling exposure to the air and subsequent oxidation in the laboratory the siderite in austin chalk samples appears to have altered to fe2o3 maghemite or fe3o4 magnetite increasing the magnetic moment and changing the nrm and ams directions in the samples the continuing changes appear to reflect a conversion from the less stable fe2o3 to fe2o3 hematite or oxidation of fe3o4 to fe2o3 we infer from our study that oxidation of siderite bearing limestone e g during the formation of unconformities or due to low magnitude tectonic events may produce a very stable secondary magnetic moment in the rock such changes may be very important when interpreting paleomagnetic data from limestones

a conceptual model for groundwater circulation using isotopes and geochemical tracers coupled with hydrodynamics a case study of the lez karst system france abstract geochemical and isotopic tracers 18o 2h 87sr 86sr and 13ctdic were used to constrain origins and chemical evolution of groundwater in a mediterranean karst system the lez spring is the main perennial outlet of this karst system and supplies the metropolitan area of montpellier southern france with drinking water groundwater samples were collected at the lez spring and surrounding springs and wells under different hydrodynamic conditions during two hydrological years from june 2008 until may 2010 the results show that multiple hydrological compartments interact through an important network of fractures and faults they notably reveal connections between the main jurassic limestone aquifer and the overlying cretaceous valanginian compartment and between the surface and deep levels of the karst system isotopic tracers provided information about atmospheric recharge origins lithological signatures and chemical evolution of waters long residence time groundwaters issued from deep layers have a triassic hydrochemical fingerprinting being enriched in 13ctdic and characterized by high concentrations in cl as well as high sr ca mg ca and 87sr 86sr ratios evidences suggest that these waters mix with waters from the lower layers of the main jurassic aquifer constitute an intermediate storage compartment prone to rise through piston flow mechanism a two end member hydrograph separation based on ec tds was used to determine the proportion of the deep compartment s contribution to the lez spring outflow on average over the study period the main aquifer compartment and the deep aquifer compartment are estimated to contribute 92 6 and 7 4 of groundwater flow at the lez spring respectively

using 222rn to examine groundwater surface discharge interaction in the rio grande de manati puerto rico 222rn was used in the karst drainage basin of the rio grande de manati in puerto rico to study groundwater surface flow relationships locations of groundwater influx along two sections of the rio grande de manati were identified the 222rn measurements were used together with stream discharge data in a mass balance equation to quantify the groundwater inputs the investigation established that both of the sections of the rio manati surveyed not only gained groundwater but lost surface flow it was calculated that the river gained about 1 2m3s 1 and lost 0 5m3s 1 to the aquifer between ciales and united states geological survey gauging station 5 between united states geological survey gauging stations 6 and 7 groundwater influx and stream flow loss occurred simultaneously with groundwater inputs equalling surface discharge losses of 4m3s 1 the study successfully demonstrated the innovative application of 222rn as a geochemical tracer in examining groundwater surface flow relationships in a karst system

confronting surface and groundwater balances on the la rochefoucauld touvre karstic system charente france 1 the touvre spring is the only outlet of a large karstic system the la rochefoucauld karst located in the west of france this system is particularly interesting from a modeler s point of view for it allows to investigate how karstic losses and gains can be accounted for within a rainfall runoff model indeed this spring is fed by the losses of three rivers which are themselves gaged after recharging the karstic aquifer this setting is exceptional in that simulations of surface catchment losses estimated by the gr4j rainfall runoff model can be compared with measurements of spring discharge at the outlet of the karstic system it provides an opportunity to test the estimates of catchment leakages which are often suspected but seldom measurable against observations we show here that the conceptualization of surface losses in the gr4j rainfall runoff model yields simulated leakage volumes that are consistent with the spring flow volumes and that provided a routing store is added to gr4j to account for the specific retarding behavior of the karstic aquifer an integrated model can be proposed to represent the behavior of the whole system adequately the touvre case study shows that a parsimonious empirical rainfall runoff representation of a karstic system is possible it also provides an independent corroboration for the conceptualization of surface catchment leakages proposed in the gr4j rainfall runoff model

changes in the isotopic and chemical composition of ground water resulting from a recharge pulse from a sinking stream abstract the little river an ephemeral stream that drains a watershed of approximately 88 km 2 in northern florida disappears into a series of sinkholes along the cody scarp and flows directly into the carbonate upper floridan aquifer the source of water supply in northern florida the changes in the geochemistry of ground water caused by a major recharge pulse from the sinking stream were investigated using chemical and isotopic tracers and mass balance modeling techniques nine monitoring wells were installed open to the uppermost part of the aquifer in areas near the sinks where numerous subterranean karst solution features were identified using ground penetrating radar during high flow conditions in the little river the chemistry of water in some of the monitoring wells changed reflecting the mixing of river water with ground water rapid recharge of river water into some parts of the aquifer during high flow conditions was indicated by enriched values of delta 18 o and delta deuterium 1 67 to 3 17 per mil and 9 2 to 15 6 per mil respectively elevated concentrations of tannic acid higher more radiogenic 87 sr 86 sr ratios and lower concentrations of 222 rn silica and alkalinity compared to low flow conditions the proportion of river water that mixed with ground water ranged from 0 10 to 0 67 based on binary mixing models using the tracers 18 o deuterium tannic acid silica 222 rn and 87 sr 86 sr on the basis of mass balance modeling during steady state flow conditions the dominant processes controlling carbon cycling in ground water are the dissolution of calcite and dolomite in aquifer material and aerobic degradation of organic matter

river spring connectivity and hydrogeochemical interactions in a shallow fractured rock formation the case study of fuensanta river valley southern spain in upland catchments the hydrology and hydrochemistry of streams are largely influenced by groundwater inflows at both regional and local scale however reverse conditions groundwater dynamics conditioned by surface water interferences although less described may also occur in this research the local river spring connectivity and induced hydrogeochemical interactions in intensely folded fractured and layered cretaceous marls and marly limestones fuensanta river valley s spain are discussed based on field observations tracer tests and hydrodynamic and hydrochemical data the differential flow measurements and tracing experiments performed in the fuensanta river permitted us to quantify the surface water losses and to verify its direct hydraulic connection with the fuensanta spring the numerical simulations of tracer breakthrough curves suggest the existence of a groundwater flow system through well connected master and tributary fractures with fast and multi source flow components furthermore the multivariate statistical analysis conducted using chemical data from the sampled waters the geochemical study of water rock interactions and the proposed water mixing approach allowed the spatial characterization of the chemistry of the springs and river stream waters draining low permeable cretaceous formations results corroborated that the mixing of surface waters as well as calcite dissolution and co2 dissolution exsolution are the main geochemical processes constraining fuensanta spring hydrochemistry the estimated contribution of the tributary surface waters to the spring flow during the research period was approximately 26 53 fuensanta river and 47 74 convento stream being predominant the first component during high flow and the second one during the dry season the identification of secondary geochemical processes dolomite and gypsum dissolution and dedolomitization in fuensanta spring waters evidences the induced hydrogeochemical changes resulting from the allogenic recharge this research highlights the usefulness of an integrated approach based on river and spring flow examination dye tracing interpretation and regression and multivariate statistical analysis using hydrochemical data for surface water groundwater interaction assessment in fractured complex environments worldwide whose implementation becomes critical for an appropriate groundwater policy

high resolution study on the hydrochemical variations caused by the dilution of precipitation in the epikarst spring an example spring of landiantang at nongla mashan china in addition to rainfall high resolution measurements of water level ph specific conductivity and temperature of landiantang epikarst spring at nongla mashan county in guangxi province china were recorded in summer rainy season by using a data logger with time interval of fifteen minutes water from the spring issues along a karst conduit during the rainstorms in summer it was found that the ph and temperature of landiantang spring increased while its specific conductivity decreased as hco3 ca2 and mg2 are the dominant ions linear relationships between concentrations of those ions and specific conductivity were developed according to the ion concentrations from the linear relationships the saturation indexes of calcite sic the saturation indexes of dolomite sid and co2 partial pressure log text p text co text 2 of the spring were calculated results indicated that the log text p text co text 2 of the spring during the rainstorms was lower than that without rain and its sic and sid was also lower combined with the characteristics of the epikarst zone it was inferred that the above results were caused by the dilution of rainwater because overland flow with high ph due to neutralization of carbonate rock dusts in the air to rainwater and low specific conductivity traveling through the conduit rapidly during rainstorms showed greater influences on the hydrochemical variations of the epikarst spring

geomagnetic polarity in the early cretaceous and jurassic knowledge of the polarity history of the earth s magnetic field during the mesozoic stems primarily from oceanic m sequence magnetic anomalies certain of these anomalies have been biostratigraphically dated from sediments immediately overlying basaltic basement at deep sea drilling project d s d p sites within the m sequence the biostratigraphic control is such that these age estimates are generally imprecise and moreover the sediment ages represent only minimum ages for the basaltic basement itself magnetostratigraphy in sedimentary land sections provides improved age estimates for magnetozones which can then be correlated with m sequence anomalies magnetostratigraphy provides not only enhanced dating of the ocean floor and resolution of the behaviour of the geomagnetic field during the cretaceous and jurassic oceanic quiet zones but also a world wide correlation tool for sedimentary stratigraphy the middle cretaceous is characterized by a long period of normal polarity extending from the early aptian to the early campanian reversed magnetozones corresponding to oceanic anomalies m 0 m 1 and m 3 have been palaeontologically dated as early aptian middle barremian and early barremian respectively magnetozones corresponding to oceanic anomalies m 5 to m 15 are hauterivian to valanginian in age but have not been individually associated with stage boundaries mainly due to poor biostratigraphic control in italian pelagic limestone sections of this age however magnetozones corresponding to oceanic anomalies m 16 to m 22 have been individually correlated to lower berriasian and tithonian palaeontological zones and extrapolation of this correlation gives an age for anomaly m 25 close to the oxfordian kimmeridgian boundary the jurassic 9quiet zone in the oceans is recognized in land sections as an extended period of predominantly normal polarity and although poor biostratigraphic control in this interval limits our knowledge of its duration we consider that it extended through the oxfordian and callovian stages the bathonian and older jurassic stages are characterized by mixed polarity a precise correspondence of magnetozones to ammonite zonations and stage boundaries is only available for the aalenian to pliensbachian interval where the frequency of reversal was apparently very high

mineralogical controls on the engineering behavior of hydrothermally altered granites under uniaxial compression effective engineering characterization of granites altered through processes of kaolinization is critical for safe extraction and design of slopes for the china clay industry in south west england by considering this important issue representative samples taken from a range of decomposition grades of altered granite were used to assess the controlling influence of changes in mineralogy on uniaxial compressive strength elastic modulus dry density and ultrasonic velocity dramatic reduction in uniaxial compressive strength occurs between alteration grades ii and iii analysis of acoustic emission data constrained by evaluation of scanning electron microscope sem images and strain gauge deformation readings has been used to identify crack propagation stages during uniaxial compression quantitative evaluation of mineralogy was determined from x ray diffraction xrd analysis of representative samples in order to establish relationships between mineralogy such as kaolinite and uniaxial compressive strength for the different alteration grade material the results of the testing confirm that the degree of alteration or kaolinization and associated changes in mineralogy of the granite is directly related to reduction in uniaxial compressive strength and dry density