field scale water transport in unsaturated crystalline rock safe disposal of toxic wastes in geologic formations requires minimal water and gas movement in the vicinity of storage areas ventilation of repository tunnels or caverns built in solid rock can desaturate the near field up to a distance of meters from the rock surface even when the surrounding geological formation is saturated and under hydrostatic pressures a tunnel segment at the grimsel test site located in the aare granite of the bernese alps central switzerland has been subjected to a resaturation and subsequently to a controlled desaturation using thermocouple psychrometers tp and time domain reflectometry tdr the water potentials psi and water contents theta were measured within the unsaturated granodiorite matrix near the tunnel wall at depths between 0 and 160 cm during the resaturation the water potentials in the first 30 cm from the rock surface changed within weeks from values of less than 1 5 mpa to near saturation they returned to the negative initial values during desaturation the dynamics of this saturation desaturation regime could be monitored very sensitively using the thermocouple psychrometers the tdr measurements indicated that water contents changed dose to the surface but at deeper installation depths the observed changes were within the experimental noise the field measured data of the desaturation cycle were used to test the predictive capabilities of the hydraulic parameter functions that were derived from the water retention characteristics psi theta determined in the laboratory a depth invariant saturated hydraulic conductivity k s 3 0 x 10 11 m s 1 was estimated from the psi t data at all measurement depths using the one dimensional unsaturated water flow and transport model hydrus vogel er al 1996 for individual measurement depths the estimated k s varied between 9 8 x 10 12 and 6 1 x 10 11 the fitted k s values fell within the range of previously estimated k s for this location and led to a satisfactory description of the data even though the model did not include transport of water vapor

high resolution characterization of vadose zone dynamics using cross borehole radar characterization of the dynamics of moisture migration in the unsaturated zone of aquifers is essential if reliable estimates of the transport of pollutants threatening such aquifers are to be made electrical geophysical investigation techniques such as ground penetrating radar offer suitable methods for monitoring moisture content changes in the vadose zone moreover these tools permit relatively large measurement scales appropriate for hydrological models of unsaturated processes and thus they offer a distinct advantage over conventional measurement approaches ground penetrating radar when applied in transmission mode between boreholes can provide high resolution information on lithological and hydrological features the technique may be applied in tomographic mode and in a much simpler vertical profile mode both modes of measurement have been utilized using two boreholes 5 m apart located at a field site in the uk sherwood sandstone aquifer radar transmission measurements have been used to characterize the change in moisture content in unsaturated sandstone due to controlled water tracer injection continual monitoring of cross borehole radar measurements over an 18 month period has also permitted determination of travel times of natural loading to the system and has revealed the impact of subtle contrasts in lithology on changes in moisture content over time the time series of inferred moisture contents show clearly wetting and drying fronts migrating at a rate of approximately 2 m month 1 throughout the sandstone

estimation of permeable pathways and water content using tomographic radar data near surface environmental investigations often require monitoring of the spatial distribution of water content and identification of preferential fluid flow paths water content estimates are needed for example to model and predict pollutant transport through the vadose zone and to subsequently design an efficient and reliable remediation plan the characteristics of preferential flow paths as well as the location and geometry of these features are necessary to model and predict flow and transport in complex geological media such as fractured or strongly heterogeneous porous systems

silicic volcanism at an off axis geothermal field in the mariana trough back arc basin an abyssal hill site with localized high heat flow on the 3 m y old west flank of the active ridge in the mariana trough has sets of oblique fault scarps mapped by multi beam transits and clusters of 50 to 1 000 m diameter domes examined with a deep tow survey some of the domes including small 20 to 30 m high rocky knobs encrusted with manganese oxide crop out through the sediment cover but despite heat flow evidence that they are sites of hydrothermal discharge these bedrock features are fundamentally different from the hydrothermal mounds found on some mid ocean ridges dredging one dome recovered a rhyodacite pumice that we believe erupted at a depth of 2 600 3 600 m within the basin the siliceous rock may be an extreme differentiate of a tholeiitic magma but a more likely origin is partial melting of the basin s sedimentary fill

ground penetrating radar assisted saturation and permeability estimation in bimodal systems near surface investigations often require characterization of vadose zone hydraulic parameters conventional sampling or borehole techniques for estimating these parameters are costly time consuming and invasive all of which limit collection of hydrogeological data at a spacing needed for detailed site characterization incorporation of two or three dimensional densely sampled geophysical data with conventional hydrological data increases the amount of data available for the characterization and thus has the potential to significantly improve the hydraulic parameter estimates over those obtained from borehole data alone the hydraulic estimation procedure can be greatly improved by incorporating dielectric information potentially available from ground penetrating radar gpr a noninvasive high resolution geophysical method the procedures for collecting and processing gpr data in the format needed for the proposed estimation technique are relatively new and still a topic of research our method requires as a starting point the ability to estimate dielectric constants from gpr data numerical experiments were performed to investigate the general utility of the gpr assisted estimation technique under a range of conditions three bimodal systems were investigated each system being composed of a sand facies together with another facies with a larger clay volume fraction each facies was defined using characteristic values of clay content porosity and permeability using dielectric information and petrophysical relations degree of saturation and intrinsic permeability values at each location within the three systems were identified for bimodal systems a dielectric constant measurement corresponds to two possible values of saturation and intrinsic permeability at each location single values of saturation and intrinsic permeability were estimated from these values using the principle of maximum likelihood results from case studies demonstrate that a combination of gpr data with conventional borehole data significantly improves the estimates of saturation and has the potential to improve the estimates of permeability over those obtained from well bore data alone the proposed method should be especially advantageous for vadose zone characterization in areas favorable for gpr data acquisition where detailed hydraulic parameter information is required but the drilling of numerous boreholes is prohibited

spatial variability in biogenic gas accumulations in peat soils is revealed by ground penetrating radar gpr 1 we performed surface and borehole ground penetrating radar gpr tests together with moisture probe measurements and direct gas sampling to detect areas of biogenic gas accumulation in a northern peatland the main findings are 1 shadow zones signal scattering observed in surface gpr correlate with areas of elevated ch4 and co2 concentration 2 high velocities in zero offset profiles and lower water content inferred from moisture probes correlate with surface gpr shadow zones 3 zero offset profiles depict depth variable gas accumulation from 0 10 by volume 4 strong reflectors may represent confining layers restricting upward gas migration our results have implications for defining the spatial distribution volume and movement of biogenic gas in peatlands at multiple scales

electrical resistivity tomography of vadose water movement cross borehole electrical resistivity tomography ert was used to image the resistivity distribution before and during two infiltration experiments in both cases water was introduced into the vadose zone and the change in resistivity associated with the plume of wetted soil was imaged as a function of time the primary purpose of this work was to study the capabilities and limitations of ert to image underground structure and ground water movement in the vadose zone a secondary goal was to learn specifics of unsaturated flow in a complex geologic setting tomographs of electrical resistivity taken before infiltration image coarser well drained soils sands and gravels as more resistive zones whereas finer grained soils silts and clays which hold more water by capillarity are imaged as more conductive images of changes in resistivity during infiltration show growth of the water infiltration plume with time that is consistent with known geology in the ert images we see the effects of capillary barriers and infer differences between capillary driven flow through fine sediments and gravity driven flow through very permeable sediments images are consistent with numerical flow simulations using hydrological parameter values consistent with soil types inferred from well logs ert can be a useful tool to monitor movement of circuitous moisture fronts in a heterogeneous field setting that would go undetected by borehole measurements

monitoring rock freezing and thawing by novel geoelectrical and acoustic techniques automated monitoring of freeze thaw cycles and fracture propagation in mountain rockwalls is needed to provide early warning about rockfall hazards conventional geoelectrical methods such as electrical resistivity tomography ert are limited by large and variable ohmic contact resistances requiring galvanic coupling with metal electrodes inserted into holes drilled into rock and which can be loosened by rock weathering we report a novel experimental methodology that combined capacitive resistivity imaging cri ert and microseismic event recording to monitor freeze thaw of six blocks of hard and soft limestones under conditions simulating an active layer above permafrost and seasonally frozen rock in a nonpermafrost environment our results demonstrate that the cri method is highly sensitive to freeze thaw processes it yields property information equivalent to that obtained with conventional ert and offers a viable route for nongalvanic long term geoelectrical monitoring extending the benefits of the methodology to soft hard rock environments contact impedances achieved with cri are less affected by seasonal temperature changes the aggregate state of the pore water liquid or frozen and the presence of low porosity rock with high matrix resistivities than those achieved with ert microseismic monitoring has the advantage over acoustic emissions that events were recorded in relevant field distances of meters to decameters from cracking events for the first time we recorded about 1000 microcracking events and clustered them in four groups according to frequency and waveform compared to previous studies mainly on ice cracking in glaciers the groups are attributed to single or multiple stage cracking events such as crack coalescence

radar frequency dielectric dispersion in sandstone implications for determination of moisture and clay content 1 the relationship between dielectric permittivity water saturation and clay content for the sherwood sandstone from ne england was characterized as part of a wider study of the vadose zone moisture dynamics and pollution vulnerability of this aquifer dielectric permittivity was measured over the full range of saturation levels for various lithologies ranging from clean medium grained sandstone to fine grained sandstone containing up to 5 clay using a specially constructed dielectric cell dielectric constant kr is largely independent of frequency between 350 mhz and 1000 mhz below 350 mhz kr of fine grained clay rich sandstone shows frequency dispersion tests on physical models of the sandstone consisting of a fine fraction of ottawa sand and montmorillonite clay indicate that the clay minerals within the sandstone are responsible for its frequency dispersive behavior these tests also show that increasing pore fluid salinity increases dielectric dispersion at the lower end of the frequency range which indicates that this arises from the interfacial maxwell wagner mechanism associated with platy clay particles water saturated sand clay mixtures show very low dielectric constants at high frequencies over 650 mhz this effect is independent of salinity and probably results from the layered geometric arrangement of solids bound and free water within the swelling clay the complex refractive index method crim with a mineral dielectric constant of about 5 provides a good match to the water saturation versus dielectric constant data for all sherwood sandstone lithologies at frequencies between 350 and 1000 mhz and for clay poor sandstone at lower frequencies below 350 mhz the presence of a few percent of clay in some sherwood sandstone lithologies raises their crim best fit mineral dielectric constant substantially

profiles of chloride in matrix porewater as natural tracer for matrix diffusion in crystalline rocks abstract matrix porewater from low permeable grimsel granodiorite was successfully characterised using indirect methods applied to originally saturated core samples core samples were taken from a 17 m long borehole originating from a tunnel of the grimsel test site into the crystalline bedrock intersecting a tectonic shear zone with a water conducting fracture matrix porewater chloride profiles on the meter scale were determined on both sides of the water conducting fracture to evaluate transport processes within the bedrock formation a series of diffusive model calculations were performed which to fit the porewater data boundary and initial conditions were varied according to the geological conditions whereas other required parameters such as the connected porosity and pore diffusion coefficients were determined by laboratory experiments on the cores and extrapolated to in situ conditions the main conclusions can be summarized as follows 1 chloride porewater profiles at the meter scale can be simulated using diffusive transport models this provides evidence that diffusive exchange with active fractures occurs over a range of a few meters in the low permeable crystalline bedrock 2 the best fit of the diffusion profile was achieved by a model approach which takes asymmetric initial cl concentrations into account this indicates that prior to the activation of the present water conducting fracture the porewater system in the bedrock was already active showing a concentration gradient in chloride 3 the water conducting fracture was activated at least between 850 and 1700 years before present with a best fit 1200 years before present and 4 the hydraulic were affected by the construction of the rock laboratory 20 years ago resulting in a rapid dilution of the fracture groundwater by advection

measurements of water potential and water content in unsaturated cystalline rock a water desaturation zone develops around a tunnel in water saturated rock when the evaporative water loss at the rock surface is larger than the water flow from the surrounding saturated region of restricted permeability we describe the methods with which such water desaturation processes in rock materials can be quantified the water retention characteristic theta psi of crystalline rock samples was determined with a pressure membrane apparatus the negative water potential identical to the capillary pressure psi below the tensiometric range psi 0 1 mpa can be measured with thermocouple psychrometers tp and the volumetric water contents theta by means of time domain reflectometry tdr these standard methods were adapted for measuring the water status in a macroscopically unfissured granodiorite with a total porosity of approximately 0 01 the measured water retention curve of granodiorite samples from the grimsel test site central switzerland exhibits a shape which is typical for bimodal pore size distributions the measured bimodality is probably an artifact of a large surface ratio of solid voids the thermocouples were installed without a metallic screen using the cavity drilled into the granodiorite as a measuring chamber the water potentials observed in a cylindrical granodiorite monolith ranged between 0 1 and 3 0 mpa those near the wall in a ventilated tunnel between 0 1 and 2 2 mpa two types of three rod tdr probes were used one as a depth probe inserted into the rock the other as a surface probe using three copper stripes attached to the surface for detecting water content changes in the rock to air boundary the tdr signal was smoothed with a low pass filter and the signal length determined based on the first derivative of the trace despite the low porosity of crystalline rock these standard methods are applicable to describe the unsaturated zone in solid rock and may also be used in other consolidated materials such as concrete

soil moisture content estimation using ground penetrating radar reflection data abstract ground penetrating radar gpr reflection travel time data were used to estimate changes in soil water content under a range of soil saturation conditions throughout the growing season at a california winery data were collected during three data acquisition campaigns over an 80 by 180 m area using 100 mhz surface gpr antennas gpr reflections were associated with a thin low permeability clay layer located 0 8 1 3 m below the ground surface that was identified from borehole information and mapped across the study area field infiltration tests and neutron probe logs suggest that the thin clay layer inhibited vertical water flow and was coincident with high volumetric water content vwc values the gpr reflection two way travel time and the depth of the reflector at the borehole locations were used to calculate an average dielectric constant for soils above the reflector a site specific relationship between the dielectric constant and vwc was then used to estimate the depth averaged vwc of the soils above the reflector compared to average vwc measurements from calibrated neutron probe logs over the same depth interval the average vwc estimates obtained from gpr reflections had an rms error of 0 018 m3 m 3 these results suggested that the two way travel time to a gpr reflection associated with a geological surface could be used under natural conditions to obtain estimates of average water content when borehole control is available and the reflection strength is sufficient the gpr reflection method therefore has potential for monitoring soil water content over large areas and under variable hydrological conditions

cenozoic landforms and post orogenic landscape evolution of the balkanide orogen evidence for alternatives to the tectonic denudation narrative in southern bulgaria continental denudation is the mass transfer of rock fromsource areas to sedimentary depocentres and is typically the result of earth surface processes however a process known as tectonic denudation is also understood to expose deep seated rocks in short periods of geological timeby displacing largemasses of continental crust along shallow angle faults and without requiring major contributions from surface erosion some parts of the world such as the basin and range in theusa or the aegean province in europe have been showcased for their cenozoic tectonic denudation features commonly described as metamorphic core complexes or as supradetachment faults based on 22 new apatite fission track aft and 21 helium ahe cooling ages among rock samples collectedwidely from plateau summits and their adjacent valley floors and elaborating on inconsistencies between the regional stratigraphic topographic and denudational records this study frames a revised perspective on the prevailing tectonic denudation narrative for southern bulgaria we conclude that conspicuous landforms in this region such as erosion surfaces on basement cored mountain ranges are not primarily the result of paleogene to neogene core complex formation they result instead from ordinary erosion driven subaerial denudation rock cooling each time suggesting at least 2 km of crustal denudation has exposed shallow paleogene granitic plutons and documents a 3 stage wave of erosional denudation which progressed from north to south during themiddle eocene oligocene early tomiddlemiocene and late miocene denudation initially prevailed during the paleogene under a syn orogenic compressional regime involving piggyback extensional basins phase 1 but subsequently migrated southward in response to post orogenic upper plate extension driven by trench rollback of the hellenic subduction slab phase 2 rare insight given by the denudation pattern indicates that trench rollback progressed at amean velocity of 3 to 4 km ma the neogene horst and grabenmosaic that defines the modern landscape phase 3 has completely overprinted the earlier fabrics of phases 1 and 2 and has been the prime focus of tectonic geomorphologists working in the region the new narrative proposed here for linking the geodynamic evolution of se europe with surface landform assemblages raises issues in favour of better documenting the regional sedimentary record of existing paleogene basins which constitute a poorly documented missing link to the thermochronological evidence presented here

gondwanan late jurassic and cretaceous palaeosurfaces of the australian craton abstract cretaceous and especially early cretaceous marine transgressions played an important part in the evolution of the australian landscape they covered at least 40 of the present australian craton and about 45 of the entire present continent in so doing they preserved in unconformity extensive areas of the pre existing or gondwana landscape though substantial gondwana elements have been ehumed at the margins of the depositional basins as a result of the cainozoic stripping of the sedimentary cover clear examples are demonstrated in the isa highlands the peake and davenport ranges and the northermost flinders ranges the basinal areas subsided under the weight of water and sediment while adjacent land areas were uplifted flexure continentale or randschwelle those that were already of low relief were dissected and regoliths were eroded but substantial areas of the gondwana plains in etch form were preserved on divides as in the gawler and hamersley ranges others were reduced to low relief by rivers graded to cretaceous shorelines as in the southern and central flinders ranges elsewhere the gondwana landscapes were preserved more or less intact as in the western yilgarn craton the mt lofty ranges and possibly the higher ridges of the macdonnell ranges the nature of the gondwana landscape varied according to structure but inselberg landscapes were widely developed and have been exhumed for instance in the western pilbara and in the eastern musgrave block kulgera region the gondwana landscape was already complex with stratigraphic conditions suitable for the exhumation of archaean preterozoic and cambrian forms for instance already in place re exposure later took place so that very old elements form integral parts of the present landscape exhumed gondwana landscapes have been preserved by burial and the stripping of some of the etch forms may have taken place in the later cainozoic so that their survival poses few difficulties other etch surfaces like those of the gawler and the hamersley ranges demonstrably were stripped in the early cretaceous and eocene respectively and they like epigene earliest tertiary and mesozoic features call for explanation various factors like resistant bedrock unequal erosion surfaces which stand high and dry interior situation and reinforcement effects go some way to relieving though they do not resolve the problem

longitudinal and lateral dispersion in an unsaturated field soil lateral and longitudinal dispersion was quantified in a field soil under water unsaturated conditions the relatively mobile dye tracer brilliant blue fcf was applied as a line source and leached into the soil at two different rates of infiltration 4 and 24 mm d 1 respectively the resulting tracer plume was photographically recorded at vertical soil profiles excavated perpendicularly to the line source after 50 100 and 200 mm of cumulative infiltration an image analysis technique was used to determine two dimensional concentration distributions from the photographs average horizontal and vertical concentration distributions were analyzed using the two dimensional advection dispersipn equation model parameters were fitted to optimize the agreement between measured and modeled averaged concentration profiles in both horizontal as well as vertical directions dispersivities showed a dependency on flow rates and amount of cumulative infiltration but this dependency appeared to be related to the degree of irregularities of observed flow patterns large dispersivities were associated with higher degree of irregularities in the flow patterns and vice versa layer boundaries played a significant role for redirecting flow when flow rates were high and cumulative infiltration was large this study demonstrates 1 that more than just the vertical concentration profiles are needed to define the transport regime under unsaturated conditions and 2 that even subtle layer boundaries affect the lateral mixing regime and exert a marked influence on the transport in the main flow direction

a parallel probe saturation profiler a new technique for fast profiling of meltwater saturation in a seasonal snowpack we describe a parallel probe saturation profiler ppsp for accurate and fast profiling of liquid water saturations in a snowpack this device utilizes the absorption of electrical energy by water molecules under the action of an external electric field due to instantaneous rotations from initially random orientations to the orientation of the applied electric field our observations show that the height of first peak signal hfps i e the difference between the maxima and minima in the ppsp signal response time series is proportional to the liquid water content and the water saturation of snow the hfps corresponding to different liquid water contents were obtained from various naturally occurring snow types and were observed to be proportional to the water saturation of the snow irrespective of snow types for simultaneous measurements at corresponding depths in a snowpack a position encoder supports the ppsp this device was calibrated for various types of snow samples and was then tested on the snow covers under different climatic zones of the himalaya the operation of the ppsp is easy and fast the distribution of liquid water within a large snow cover can be estimated speedily using the ppsp with a vertical resolution of 7 mm

in situ porosity distribution using geophysical tomography a geotomograph of an in situ fractured granite rockmass has been quantitatively interpreted to yield estimates of porosity distribution this was accomplished by comparing the tomograph measured electromagnetic properties of the rock with laboratory measurements of the rock s electromagnetic properties at various known water contents these estimates of water content are interpreted as values of rockmass porosity because the formation is fully saturated

borehole time domain reflectometry in layered sandstone impact of measurement technique on vadose zone process identification the hydraulic behaviour of the vadose zone of a layered sandstone aquifer has been investigated using borehole based time domain reflectometry tdr both a commercially available portable packer tdr system trime b3l borehole packer probe and specially designed borehole emplaced tdr probes were used to monitor seasonal fluctuations in water content in the vadose zone of a layered sandstone over 1 year under natural rainfall loading the data show that the vadose zone contains seasonal perched water tables that form when downward percolating water reaches layers of fine grained sandstone and siltstone and causes local saturation the formation of perched water tables is likely to lead to lateral flow bypassing the less permeable finer layers this contrasts with behaviour inferred from previous studies of the same aquifer that used borehole radar and resistivity which suggested its vadose zone behaviour was characterized by uniform downwards migration of wetting fronts to investigate the impact of measurement technique on observed response the tdr data reported here were used to produce simulated zero offset profile zop borehole radar responses this simulation confirmed the limited ability of zop borehole radar to detect key vadose zone processes because the phenomenon of critical refraction minimizes the sensitivity of the results to high water content layers the ability of the resistivity method to detect perched water table responses is also limited because of the relatively large sampling volume of the technique the study illustrates that inappropriate technique selection results in hydrological process mis identification with serious consequences for the usefulness of data in hydrological modeling

ground penetrating radar for determining volumetric soil water content results of comparative measurements at two test sites ground penetrating radar gpr can provide information on the soil water content of the unsaturated zone in sandy deposits via measurements from the surface and so avoids drilling proof of this was found from measurements of radar wave velocities carried out ten times over 13 months at two test sites in the netherlands at these same locations and on the same dates soil water content was measured in access robes using a capacitance probe comparison of gpr and capacitance probe observations revealed that 1 the inferred absolute values of soil water content agree well this is remarkable because the soil water content is deduced entirely differently for the two methods 2 seasonal fluctuations in soil water content established for different general depth zones of radar waves correlate well with the fluctuations observed in the access tubes 3 the various methods to determine the propagation velocities of radar waves are complementary together they produce a realistic and reasonably complete image of the vertical distribution of the soil water content of the entire unsaturated zone high frequency 200 mhz direct groundwaves and refracted waves constitute a particularly attractive complementary combination which provides information on consecutive shallow zones in the underground i e the zones of major soil water content fluctuations 4 lateral variations established at one of the test sites where several access tubes have been placed in a transect also follow from the gpr measurements along that profile this non destructive determination of soil water content in practically continuous and detailed sections is one of the great assets of gpr opening the way to mapping preferential soil water flow paths

influence of seabed topography on the distribution of manganese nodules and associated features in the central indian basin a study based on photographic observations abstract the distribution of manganese nodules and associated rock outcrops and sediment cover in the central indian basin 10 16 s 73 82 e were studied from seabed photographs in relation to topographic features categorised as the crests of seamounts and abyssal hills their slopes valleys and abyssal plains the nodule coverages are high on the crests and slopes mean coverage 12 3 and 15 3 and low in the valleys and plains mean coverage 0 3 and 1 4 the occurrence of nodules is related to the rock outcrops and sediment cover which are in turn controlled by variations in seabed topography rock outcrops are exposed on crests and slopes sediment thickness increases from nil on the crests to very thin on the slopes and from thick to very thick in the plains and valleys high nodule concentration along the slopes and near the crests of the seamounts and abyssal hills is a result of the availability of rock fragments as nuclei which are derived from the rock outcrops however areas where nodules are absent are common in all the topographic settings

near surface wetting of a ponded basalt surface observations using time domain reflectometry abstract the changes in dielectric constant k a during an infiltration test on a fractured basalt surface in south eastern idaho were monitored using time domain reflectometry tdr because changes in k a were caused largely by changing amounts of water in the formation and to a small extent by diurnal and seasonal temperature fluctuations tdr served as a useful indicator of the moisture status in the formation our results indicate that wetting and drying were spatially variable within and immediately beyond a 7 8 m 2 pond various locations close to the surface responded to fast flow whereas others showed evidence of poor hydraulic communication with the surface data collected during a rainfall event which occurred a few days after ponding ceased indicated that this boundary condition evoked a similar hydrologic response to ponding this effort suggests that tdr is a useful tool for detecting moisture changes in fractured media

efficient three dimensional data inversion soil characterization and moisture monitoring from cross well ground penetrating radar at a vermont test site we extend our methodology for three dimensional parameter structure and value estimation and apply it to a vermont test site ground penetrating radar gpr cross well travel times are inverted for estimation of heterogeneous gpr soil velocities before and after a controlled release of salt water in the unsaturated zone the method which is based on an approximation of the extended kaiman filter in conjunction with data driven zonation automatically estimates not only distributed zone values but also the number of zones zone geometry and zone covariance resultant gpr velocity estimates are shown to reduce travel time estimation errors and to be consistent with independent cone penetrometer measurements at all five walls at the site comparison of velocity estimates before and after forced injection of salt water is used to detect and visualize soil moisture patterns in three dimensions by varying the cluster tolerance criterion in the data driven zonation process the user can obtain a desired resolution of heterogeneity number of zones used in the resultant model

diffusive transport of water in porous feldspars from granitic saprolites in situ experiments using ftir spectroscopy abstract a novel experimental cell was developed for in situ measurements of transport phenomena in porous media using fourier transform infrared ftir spectroscopy the technique was employed at ambient pressure in the temperatures range of 11 44 c to study the h 2 o d 2 o exchange between water saturated weathered feldspars bulk porosity of 5 19 vol for feldspar from granitic saprolites and a surrounding aqueous liquid such measurements are an important step for understanding internal weathering reactions of feldspars in soils and aquifers effective diffusion coefficients d eff for water in water saturated porous feldspars were determined assuming one dimensional diffusion in a quasi homogeneous medium the values of d eff vary from 7 2 10 10 to 1 9 10 11 m 2 s and are 1 2 orders of magnitude lower than the diffusion coefficients d of protons and molecular h 2 o in liquid water the activation energy for the h 2 o d 2 o exchange process in porous feldspars ranges from 7 8 to 18 8 kj mol the results imply that the effective diffusivity of water is mainly controlled by physical properties of the feldspars like porosity pore connectivity pore geometry and distribution perthitic feldspars with homogeneous pore distribution in the albitic lamellas have diffusional tortuosity factors x d d eff between 3 and 10 while alkali feldspars with inhomogeneously distributed and disconnected pores have much higher x values up to 129 diffusion anisotropy has been verified for a vein perthite with diffusion perpendicular to the lamellas being faster by 0 3 0 5 log units than within the lamellas it has to be emphasized that the study is based only on few selected feldspars including perthitic feldspar and additional work on samples with different weathering stages is needed to test the importance of the different parameters controlling diffusive transport in the pore system

a theoretical treatment of the effect of microscopic fluid distribution on the dielectric properties of partially saturated rocks1 microscopic fluid distribution can have a significant effect on the dielectric properties of partially saturated rocks evidence of this effect is found in the laboratory data presented by knight and nur in which different methods for controlling saturation produced very different results for the dependence of the dielectric response on water saturation in this study previously derived models for the dielectric response of a heterogeneous medium are generalized and the case of a pore space occupied by multiple pore fluids is considered by using various geometrical distributions of water and gas it is observed that both the pore geometry in which saturation conditions are changing and the gas water geometry within a given pore space are critical factors in determining the effective dielectric response of a partially saturated rock as an example data for a tight gas sandstone undergoing a cycle of imbibition and drying are analysed previous research has demonstrated that significantly different microscopic fluid distributions result from the application of these two techniques to control the level of water saturation by approximating these microscopic fluid distributions using simple geometrical models good agreement is found between experimental data and calculated dielectric properties

potential use of time domain reflectometry for measuring water content in rock abstract quantifying water movement through bedrock materials requires a technique which can accurately measure water content at precise locations within the medium time domain reflectometry tdr is widely used to measure the water content of soil and has a measurement sensitivity which is tightly confined to the area immediately surrounding the probes this study applies tdr to the measurement of water content in rocks the technique was evaluated using sandstone and welded tuff in a series of laboratory experiments a block of each rock type was instrumented with a series of evenly spaced tdr probes each block was first saturated with water and then allowed to air dry the water content was determined gravimetrically using the tdr over a period of several weeks the results indicate that the tdr technique can be used to determine the water content of rock with an accuracy comparable with that reported for the technique used in soils

reconstruction of palaeoinfiltration during the holocene using porewater data laxemar sweden abstract the interaction between fracture groundwater and crystalline rock matrix was explored by extracting the porewater residing today in the low permeability saturated rock matrix about 100 m below surface concentrations of the natural tracers cl 18 o 2 h in the porewater along a 11 m long profile from a water conducting fractured deformation zone into the intact rock matrix are the result of superimposed changes in the fracture groundwater composition the tracer profiles have evolved by diffusive exchange of the porewater in the rock matrix with groundwater flowing in fractures of high and low transmissivity since the retreat of the last weichselian glacier from the laxemar investigation area sweden numerical simulations indicate the necessity of a diachronic arrival of surface infiltration signals in the two fractures at the sampling location and of heterogeneous transport properties in the rock matrix as determined for the individual rock samples stringent conclusions regarding the palaeoinfiltration conditions can only be obtained when at least two tracers with independent source terms i e salinity and temperature moisture source are simulated simultaneously quantification of the porewater fracture groundwater interaction allows modification of the different evolutionary stages of the palaeoinfiltration conditions over holocene times most prominently this suggests the absence of any influence of brackish water from the yoldia sea and littornia sea in the area and the requirement for warmer climate precipitation from 8 ka to 4 5 ka bp coinciding with the holocene thermal maximum the ability to interpret the natural tracer profiles in accordance with independent geological hydrological and climatic constraints indicates that matrix diffusion in crystalline rocks is effective over decametres within timescales of 10 14 ka the impact of matrix diffusion on the fracture groundwater composition will become measurable over these timescales especially in low transmissivity fractures these data demonstrate that porewater indeed acts as an archive for palaeohydrologic variations although the resolution is still limited

correlation between occurrence of manganese nodules and rocks in a part of the central indian ocean basin abstract the distribution of manganese nodules and rocks in the deep sea is controlled by topography as shown by a study of three topographic highs in the central indian ocean basin topographic highs are dominated by encrustations slopes and flanks by exposed nodules and abyssal hills by nodules buried under a thick sediment cover fresh basalts occur at the summits of the abyssal hills and weathered basalts and pumice occur on the slopes and on the abyssal plains bottom photographs show rock outcrops on the summits thin sediment cover 10 cm on the plains the availability of rock fragments as nuclei and the thin sediment cover enables accretion of more abundant nodules up to 15 5 kg m2 on the slopes and flanks six phases of nodule distribution have been identified with respect to the different topographic domains rock outcrops and sediment thickness

liquid phase structure within an unsaturated fracture network beneath a surface infiltration event field experiment 1 we conducted a simple field experiment to elucidate structure i e geometry of the liquid phase water resulting from ponded infiltration into a pervasive fracture network that dissected a nearly impermeable rock matrix over a 46 min period dyed water was infiltrated from a surface pond while electrical resistance tomography ert was employed to monitor the rapid invasion of the initially dry fracture network and subsequent drainage we then excavated the rock mass to a depth of 5 m mapping the fracture network and extent of dye staining over a series of horizontal pavements located directly beneath the pond near the infiltration surface flow was dominated by viscous forces and the fracture network was fully stained with increasing depth flow transitioned to unsaturated conditions and the phase structure became complicated exhibiting evidence of fragmentation preferential flow fingers irregular wetting patterns and varied behavior at fracture intersections ert images demonstrate that water spanned the instrumented network rapidly on ponding and also rapidly drained after ponding was terminated estimates suggest that our excavation captured from 15 to 1 or less of the rock volume interrogated by our infiltration slug and thus the penetration depth from our short ponding event could have been quite large

ash layers and pumice in the central indian basin relationship to the formation of manganese nodules abstract manganese nodules in areas of biosiliceous sedimentation in the central indian basin cib have three main types of nuclei 1 fragments of altered ash layer 2 felsic pumice and 3 indurated residual sediments red clay type morphological variations among nodules are due to the form of the nuclei the type of accretionary process diagenetic or hydrogenetic accretion and thickness of the crust piston cores in the same areas sampled up to four tephra layers interstratified in red clay all of which underlie condensed series of pliocene to recent siliceous oozes the in situ tephra layers and fragments of tephra in the core of the nodules are similar in composition they are completely altered to smectite and smectite zeolite tephra horizons are 10 35 mm thick and have sharp contacts with the red clay rare earth element ree patterns zr hf and nb content and ti al ratios strongly suggest that this altered volcaniclastic material originated as distal fallout from the indonesian volcanic arc iva and was deposited in late neogene time positive ce ce anomalies indicate that alteration of this tephra may have occurred at the sediment water interface prior to burial under hydrogenous conditions rhyolite pumicelapilli are water laid and are variably replaced by fe mn oxides inducing a higher metal content in the bulk nodules pumice constitutes one of the main types of nuclei of diagenetic nodules that are found in the deep sea troughs and plains where biosiliceous deposits are thick petrological characteristics of the pumice suggest that volcanic eruptions from toba in northern sumatra are the most likely source tectonic deformation of the indian plate may have affected the sedimentary sequence causing uplift and outcrop of ash layers on the topographic highs and slopes eroded fragments of these ash layers and waterlaid pumice fragments have contributed significantly to the large extent of mn nodules in the cib

effects of drilling and stress release on transport properties and porewater chemistry of crystalline rocks the experimental verification of matrix diffusion in crystalline rocks largely relies on indirect methods performed in the laboratory such methods are prone to perturbations of the rock samples by collection and preparation and therefore the laboratory derived transport properties and fluid composition might not represent in situ conditions we investigated the effects induced by the drilling process and natural rock stress release by mass balance considerations and sensitivity analysis of analytical out diffusion data obtained from originally saturated large sized drillcore material from two locations drilled using traced drilling fluid for in situ stress released drillcores of quartz monzodiorite composition from the aspo hrl sweden tracer mass balance considerations and 1d and 2d diffusion modelling consistently indicated a contamination of 1 of the original pore water this chemically disturbed zone extends to a maximum of 0 1 mm into the drillcore 61 8 mm x 180 1 mm corresponding to about 0 66 of the total pore volume 0 77 vol in contrast the combined effects of stress release and the drilling process which have influenced granodioritic drillcore material from 560 m below surface at forsmark sweden resulted in a maximum contamination of the derived porewater cl concentration of about 8 the mechanically disturbed zone with modified diffusion properties covers the outermost similar to 6 mm of the drillcore 50 mm x 189 mm whereas the chemically disturbed zone extends to a maximum of 0 3 mm based on mass balance considerations and to 0 15 mm to 0 2 mm into the drillcore based on fitting the observed tracer data this corresponds to a maximum of 2 4 of the total pore volume 0 62 vol being affected by the drilling fluid contamination the proportion of rock volume affected initially by drilling fluid or subsequently with experiment water during the laboratory diffusion and re saturation experiments depends on the size of the drillcore material and will become larger the smaller the sample used for the experiment the results are further in support of matrix diffusion taking place in the undisturbed matrix of crystalline rocks at least in the cm range

time lapse imaging of saline tracer transport in fractured rock using difference attenuation radar tomography 1 accurate characterization of fractured rock aquifer heterogeneity remains one of the most challenging and important problems in groundwater hydrology we demonstrate a promising strategy to identify preferential flow paths in fractured rock using a combination of geophysical monitoring and conventional hydrogeologic tests cross well differenceattenuation ground penetrating radar was used to monitor saline tracer migration in an experiment at the u s geological survey fractured rock hydrology research site in grafton county new hampshire radar data sets were collected every 10 min in three adjoining planes for 5 hours during each of 12 tracer tests an innovative inversion method accounts for data acquisition times and temporal changes in attenuation during data collection the inverse algorithm minimizes a combination of two functions the first is the sum of weighted squared data residuals second is a measure of solution complexity based on an a priori space time covariance function subject to constraints that limit radarattenuation changes to regions of the tomograms traversed by high difference attenuation ray paths the time series of tomograms indicate relative tracer concentrations and tracer arrival times in the image planes from these we infer the presence and location of a preferential flow path within a previously identified zone of transmissive fractures these results provide new insights into solute channeling and the nature of aquifer heterogeneity at the site index terms 0910 exploration geophysics data processing 0915 exploration geophysics downhole methods 1829 hydrology groundwater hydrology 1832 hydrology groundwater transport 1894 hydrology instruments and techniques keywords radar tomography fractured rock ground penetrating radar geophysics hydrogeophysics

sphincs a system for cataloguing and interpreting seabed photographs of nodules abstract sphincs seabed photograph interpretation and cataloguing system facilitates acquisition storage retrieval and processing of data from seabed photographs of manganese nodules data retrieved from seabed photographs include operational details latitude longitude depth film colour status of operation camera settings aperture altitude area covered observations on seabed features microrelief biota rock exposure sediment characteristics seabed minerals and measurement of various parameters of nodules size coverage abundance visual observations are followed by estimation of dimensions of nodules with digitisers and by corrections based on empirical relationships determined from grab samples at the photographic sites this permits interpretation of the thickness of sediment cover the data are catalogued and stored in specially developed formats the use of dbase iii in sphincs allows easy retrieval and reference by users from various disciplines

the indian ocean nodule field petrotectonic evolution and ferromanganese deposits abstract the indian ocean nodule field ionf is significant from several points of view roughly bordered by 10 s to 16 30 s and 72 e to 80 e and located within the central indian ocean basin ciob the field hosts the world s second largest and second high grade manganese nodule deposit after the equatorial nodule belt in the north pacific ocean moreover the crust underlying this field is characterised by unique morphotectonic signatures owing to its formation between 60 and 49 ma under three variable spreading conditions fast intermediate and slow from the indian ocean ridge system iors the nodule field has been surveyed both extensively more than 0 4 million km2 area and intensively comprising of a large geophysical data set and geological sample inventory during the last two decades several morphotectonic features such as seamounts hills ridge normal lineaments and ridge parallel lineations have disturbed the apparently smooth topographic gradient 1 7000 of the seafloor here variations in the rate of spreading and formation of new oceanic crust along the ridge crest during more than one episode of india eurasia collision are imprinted in the ionf based on the nature of the ridge parallel lineations which are related to the rate of crustal accretion the field is divided in to four sectors a b c and d from north to south sectors a and c were formed at a fast rate of spreading 90 95 mm year half rate and sectors b and d were formed at an intermediate 55 mm year and slow 26 mm year rates respectively the predominance of tensional stress in sectors a and c caused asymmetrical flexuring of the seafloor resulting in widely spaced faults and folds with low amplitude and large wavelength in contrast the seafloor flexuring in sector d are closely spaced long symmetrical and of high amplitude the timing and intensity of the collision of india with eurasia is constrained by the variable intensity of these flexures suggesting probably a soft touch at 58 ma and the hard collision at about 51 ma the nodule field hosts several seamounts both as isolated entities and in linear chains which are arranged parallel to the flow lines along the direction of absolute motion of the indian plate the distribution morphology and growth patterns of a majority of these seamounts are related to spreading rate suggesting their formation at the ridge crest however many of the seamounts show more than one stage of growth with local intraplate volcanism contributing to the enlargement of the larger ancient seamounts varieties of volcanics such as tholeiitic basalts spilites ferrobasalts and pumice occur within the ionf the alteration of some of these volcanics has resulted in palagonitisation of the glass and formation of zeolites subsequently during its journey away from the ridge crest to the abyssal areas the crust underlying the nodule field witnessed intraplate volcanism this is evident from the addition of younger rocks at the base of the ancient seamounts inconsistent growth of volcanoes eruption of ferrobasalt corresponding to the areas of high amplitude magnetic zones and presence of volcanogenic hydrothermal materials vhm of 10 ka age these findings collectively hint that the ionf is geodynamically unstable and may have been volcanically active in the recent past during the last 8 ma growth of authigenic ferromanganese deposits in the form of manganese nodules and crusts has occurred in the nodule field the deposits occur at an average water depth of 5000 m the basinal geomorphology intraplate tectonic deformations and volcanic eruptions considerably influence the formation development morphology mineralogy and composition of these deposits the data show that the large seamounts reverse faults and fracture zones fzs supply rock fragments as seeds for the nodule formation the hydrogenous precipitation from the overlying water column is the primary source of metal accumulation in the nodules the secondary relatively weak intraplate eruptions along the base of ancient seamounts or lineaments subsurface igneous activity and diagenetic remobilisation of metals have also played significant role in the growth and enrichment of the deposit based on a large data set we estimate the contribution of various physico chemical parameters and model the probable conditions of formation of the ferromanganese deposits in the ionf the model also hints at the location where the resource exploitation should be rewarding

constitutive relationships and pore structure of undisturbed fracture zone samples with cohesionless fault gouge layers multiphase flow processes in fractured rocks are of major importance for the remediation of subsurface contamination for engineering petroleum reservoirs and for the safety analysis of nuclear waste repositories we developed procedures for determining the water retention curve gas permeability function and pore structure of undisturbed fracture zone samples with cohesionless fault gouge layers in the laboratory mylonitic samples were taken at grimsel test site switzerland intrinsic permeabilities of the fault gouge layers were 5 orders of magnitude higher and significant desaturation occurred at capillary pressure heads about 10 times lower than in the surrounding granodiorite thus showing that at this site gas flow would take place mainly in the fracture zone the measured water retention and gas permeability data were well represented by parametric models designed for porous media gas flow could only be detected at water saturations below about 0 8 thus showing strong phase interference at high water saturations to relate these findings to the pore structure of the samples a qualitative and quantitative description of the pore space was obtained at different scales using fluorescent resin imbibition and image analysis techniques results show that the fracture zone consists of a continuous and interconnected fracture network that is filled with a porous medium like material thus explaining the applicability of the above mentioned models and the rather strong phase interference

spatial correlation structure estimation using geophysical and hydrogeological data the large spatial variability of hydraulic properties in natural geologic systems over a wide range of scales and the difficulty of collecting representative and sufficient hydraulic property measurements using conventional sampling techniques render estimation of spatial correlation parameters difficult further compounding the estimation problem is the observation that the integral scale estimate is a function of the measurement support scale to mitigate these problems we investigate the use of tomographic geophysical data in combination with hydrogeological data in the spatial correlation estimation procedure two synthetic case studies were investigated where the scale of the geophysical measurements were varied relative to the scale of the hydrogeological properties the spatial correlation structure parameter estimation procedure was performed in the spectral domain where analysis of data having different support scales and spatial sampling windows was facilitated comparison of the spatial correlation structure parameters estimated from measured data with those of the synthetic aquifers revealed which type of data tomographic hydrogeological or a combination of both was most effective for recovering spatial correlation statistics under different sampling heterogeneity conditions these synthetic case studies suggest that collection of a few tomographic profiles and interpretation of these profiles together with limited well bore data can yield correlation structure information that is otherwise obtainable only from extensive hydrological sampling

rock moisture measurements techniques results and implications for weathering rock moisture is an important factor for the intensity and distribution of frost weathering processes however quantitative measurements are scarce which is partly due to the lack of reliable measurement techniques this paper presents five different techniques for obtaining rock moisture data while collecting rock pieces and two dimensional geoelectric measurements allow determination of the spatial moisture distribution the temporal variability can be derived from conductivity and time domain reflectometry records computer simulations using rock properties and climatic records as input data render it possible to clarify the important aspects that are responsible for the moisture distribution it proved to be advisable to use several methods to check and validate the results the results obtained in study areas in the bavarian alps make it clear that direct rainfall is the main source of rock moisture the influence of snow is limited to the immediate vicinity of the snow fields and is not equally pronounced at different times and positions rock moisture levels are higher in summer than they are in winter since in winter less water is supplied in liquid form northerly exposed rockwalls are generally more moist than those exposed in a southerly direction which is due to the different insolation as well as to the wind direction during rainfall in every position the rock is on average wetter on the inside than it is on the surface this means that shallow frost cycles as typical for south exposed sites are not affecting weathering since they take place at a depth level that is mostly dried out numerous spatial and temporal patterns of rockfall found in the same study areas can be explained through variations in rock moisture thus the moisture content of the rock is considered to be one of the major controlling factors of the frost shattering rate copyright 2005 john wiley sons ltd

application of time domain reflectometry to determination of volumetric water content in rock time domain reflectometry tdr is a widely used technique for measuring soil water content to examine its applicability to rock the authors applied tdr to a variety of rocks in the laboratory the obtained relationships between the apparent dielectric constant and the volumetric water content showed a behavior that can be partly explained by the effect of gaps between the tdr probe and rock for rocks with an effective porosity smaller than that of soil the well known model presented by topp et al 1980 for soil tended to overestimate the water content for such rocks it was determined that an individual calibration was needed for accurate determination of water content if no experimental calibration is possible frequently used mixing models may be used to establish the calibration function our investigations suggest that tdr showed the potential for measuring the apparent dielectric constant of rock and further for determining water content in rock

velocity variations and water content estimated from multi offset ground penetrating radar the common midpoint cmp processing technique has been shown to be effective in improving the results of ground penetrating radar gpr profiling when radar data are collected with the cmp multioffset geometry stacking increases the signal to noise ratio of subsurface radar reflections and results in an improved subsurface image an important aspect of cmp processing is normal moveout velocity analysis our objectives are to show the effect of multiple velocity analyses on the stacked radar image and particularly to demonstrate that this velocity information can also be used to determine subsurface water content most gpr surveys are very limited in spatial extent and assume that within the survey range radar velocity structure in the shallow subsurface can be adequately approximated by a single velocity function in data processing in this study we show that variation in radar velocity can be quite significant and that the stacked profile improves as the number of velocity analysis locations is increased interval velocities can be calculated from the normal moveout velocities derived in the cmp velocity analysis with some reasonable assumptions about subsurface conditions necessary for radar propagation interval velocity can be converted to an estimate of volumetric water content therefore by collecting gpr data in the multioffset cmp geometry not only is the radar profile improved but it also allows for an interpretation of subsurface variation in water content we show the application of these techniques to multioffset gpr data from the chalk river test area operated by atomic energy of canada limited