osmotic generation of anomalous fluid pressures in geological environments osmotic pressures are generated by differences in chemical potential of a solution across a membrane but whether osmosis can have a significant effect on the pressure of fluids in geological environments has been controversial because the membrane properties of geological media are poorly understood anomalous pressures large departures from hydrostatic pressure that are not explicable in terms of topographic or fluid density effects are widely found in geological settings and are commonly considered to result from processes that alter the pore or fluid volume which in turn implies crustal changes happening at a rate too slow to observe directly yet if osmosis can explain some anomalies there is no need to invoke such dynamic geological processes in those cases here i report results of a nine year in situ measurement of fluid pressures and solute concentrations in shale that are consistent with the generation of large up to 20 mpa osmotic pressure anomalies which could persist for tens of millions of years osmotic pressures of this magnitude and duration can explain many of the pressure anomalies observed in geological settings they require however small shale porosity and large contrasts in the amount of dissolved solids in the pore waters criteria that may help to distinguish between osmotic and crustal dynamic origins of anomalous pressures

isotopic evidence for carbonate cementation and recrystallization and for tectonic expulsion of fluids into the western canada sedimentary basin carbon oxygen and strontium isotope data for calcites and dolomites from the devonian obed platform in alberta canada demonstrate that 1 both limestones and dolostones of the obed platform underwent significant deep burial cementation and recrystallization 2 calcites experienced more extensive geochemical alteration than did dolomites under deep burial conditions and 3 the fluids that facilitated deep burial carbonate diagenesis probably were partially derived from the rocky mountain fold and thrust belt the more extensive degree of recrystallization of calcite is shown especially by its higher 87 sr 86 sr ratios a lesser degree of 13 c depletion in dolomites indicates that dolomite recrystallization partially coincided with hydrocarbon oxidation evidence supporting interpretation 3 above includes fractures and vugs bearing late diagenetic calcite cements that have extremely high 87 sr 86 sr ratios including the highest ratios reported thus far for any diagenetic carbonates from western canada 0 7252 in carbonates values this high are found only in tectonic veins in proterozoic clastic rocks in the rocky mountains and in the obed platform about 100 km into the foreland basin the late diagenetic calcite cements also have highly depleted 13 c values minimum 27 1 relative to pdb peedee belemnite indicating incorporation of oxidized carbon from thermochemical sulfate reduction the process of carbonate cementation and recrystallization in strata of the obed platform probably occurred during deep burial maximum 5 7 km and was effected by a hot 100 c mixture of connate brines and hydrothermal or metamorphic fluids that were expelled from the rocky mountain fold and thrust belt during the laramide orogeny the data also suggest that 1 the common practice of using limestones to establish marine or original geochemical baselines for stable and radiogenic isotope interpretations must be conducted with caution and 2 replacement burial dolostones are quite resistant to burial recrystallization finally the geochemical trace of tectonically expelled fluids may be limited to about 100 km into the foreland basin implying that the volumes and or fluxes of fluids produced by tectonic expulsion are rather low

hydrogeological constraints on the formation of palaeoproterozoic banded iron formations banded iron formations are critical to track changes in archaean to palaeoproterozoic ocean chemistry with deposition triggered by water column iron oxidation recently however it was suggested that reduced iron minerals were the primary precipitates and these were subsequently oxidized by oxygen bearing groundwater if true this would cast doubt on our understanding of how banded iron formations were deposited and their ability to record early ocean chemistry here we present a hydrogeological box model based on the approximately 2 5 billion year old hamersley basin of western australia developed to evaluate the plausibility of secondary iron oxidation the box model calculates the time required for groundwater to flux enough oxygen through the basin to oxidize a given amount of ferrous iron less than 9 of nearly four million model iterations returned oxidation times less than the age of the basin successful simulations required simultaneously steep hydraulic gradients high permeability and elevated oxygen concentrations our simulations show that the postdepositional oxidation of large banded iron formations is unlikely except on a limited scale that is during secondary ore formation and that oxidized iron phases were probably the precursor to large palaeoproterozoic banded iron formations banded iron formations could not have formed by postdepositional oxidation according to four million hydrogeological box model iterations that failed to reproduce secondary oxidation on reasonable timescales

petroleum source rock identification of united kingdom atlantic margin oil fields and the western canadian oil sands using platinum palladium osmium and rhenium implications for global petroleum systems this study demonstrates that petroleum and source rocks are enriched in pt and pd to the ppb level and that the 187os 188os composition coupled with the pt pd value permits the fingerprinting of petroleum to its source oils from the united kingdom atlantic margin sourced from the upper jurassic kimmeridge clay fm as well as source rock samples have been analysed for pt and pd when the pt pd value is compared with 187os 188os calculated at the time of oil generation osg the values from both the known source and the oils are similar demonstrating that they can be used as an oil to source fingerprinting tool this inorganic petroleum fingerprinting tool is particularly important in heavily biodegraded petroleum systems where traditional fingerprinting techniques e g biomarkers are severely hampered e g the world s largest oil sand deposit the west canadian oil sands wcos this has caused the source of the wcos to be hotly debated with no present day consensus between inputs from potential source units e g exshaw and gordondale fms 187os 188os and pt pd fingerprinting of the oil sands shows that the majority of the petroleum have similar 187os 188os and pt pd values supporting the hypothesis of one principal source analysis of the potential source rocks establishes that the principal source of the oil sands to be from the jurassic gordondale fm with a minor exshaw fm input thus the combination of previously pioneered re os petroleum geochronology with 187os 188os and pt pd values of petroleum permits both a temporal and spatial understanding of petroleum systems

modeling secondary oil migration with core scale data viking formation alberta basin the viking formation in the alberta basin contains approximately 88 7 x 106 m3 5 579 x 108 bbl of recoverable oil which migrated more than 200 km as indicated by oil source rock correlation simulating the mechanisms controlling secondary oil migration hydrodynamics buoyancy and permeability heterogeneity is beneficial for exploration but it remains extremely difficult to predict oil occurrences although core scale petrophysical data for the viking formation are abundant 69 000 core plugs the extent of fracture permeability and permeability alteration due to diagenesis are unknown moreover sampling bias may affect the permeability distribution in unpredictable ways numerical simulations of oil migration were conducted using the highest core plug measurement of permeability from each borehole to obtain an upper bound on oil migration velocities this permeability model is not appropriate for simulating stratigraphic entrapment of oil but it does reveal that core scale data are in the appropriate range of magnitude to have allowed significant oil migration regional groundwater flow was essential for charging several of the largest and most distant oil fields in the viking formation maximum core plug permeability data are useful for modeling the extent of secondary oil migration and may have applications to fluid flow and transport modeling in other foreland settings

groundwater flow modelling of kwa ibo river watershed southeastern nigeria groundwater flow modelling of the kwa ibo river watershed in abia state of nigeria is presented in this paper with the aim of assessing the degree of interaction between the kwa ibo river and the groundwater regime of the thick sandy aquifer the local geology of the area comprises the quaternary to recent benin formation potential aquifer zones that were delineated earlier using geoelectrical resistivity soundings and borehole data for the area formed the basis for groundwater flow modelling the watershed has been modelled with a grid of 65 rows by 43 columns and with two layers lateral inflow from the north has been simulated with constant heads at the government college umuahia and outflow at usaka elegu in the south the kwa ibo river traverses the middle of the watershed from north to south the river stage data at umudike amawom ntalakwu and usaka elegu have been used for assigning surface water levels and riverbed elevations in the model permeability distribution was found to vary from 3 to 14 5 m day 1 natural recharge due to rainfall formed the main input to the aquifer system and abstraction from wells was the main output a steady state groundwater flow simulation was carried out and calibrated against the may 1980 water levels using 26 observation wells the model computations have converged after 123 iterations under the transient state calibration the highest rainfall and hence groundwater recharge over the 10 year study period was recorded in 1996 whereas the lowest was recorded in 1991 the computed groundwater balance of 55 274 m3 day 1 was comparable to that estimated from field investigations results from the modelling show that abstraction is much less than groundwater recharge hence there is the possibility for additional groundwater exploitation in the watershed through drilling of boreholes copyright 2008 john wiley sons ltd

osmotic model to explain anomalous hydraulic heads laboratory experiments have shown that compacted clays act as osmotic membranes when they separate aqueous solutions of unequal ionic concentration theoretically osmotically induced differential hydraulic pressure in groundwater systems can be relatively high the magnitude depends primarily upon concentration differences across the membrane type of ions type of clay and pore size in experiments thin compacted clay membranes commonly exhibit varying degrees of osmotic efficiency due to ion leak age through the clay in natural systems the membrane and the solution containers are not as distinct and well defined as they are in the laboratory moreover the membrane is commonly thick inhomogeneous and composite in a buried triassic basin at the savannah river plant near aiken south carolina it is suspected that osmosis causes the saline water in the basin center to be slightly geopressurized in relation to freshwater in the overlying coastal plain aquifer two wells have heads of 7 88 and 12 98 bars 114 3 and 188 3 psi above the head in the coastal plain aquifer the head in each of these wells approximates the osmotic equilibrium head calculated from solution concentration of water produced by each well 12 000 and 18 500 mg l respectively other wells penetrating the top and edge of the triassic basin probably penetrate a zone where ion leakage gives rise to less saline water thus these wells are not geopressurized

use of vertical profiles of δ18o to constrain estimates of hydraulic conductivity in a thick unfractured aquitard vertical distributions of 18o were used to constrain hydraulic conductivity k in a thick unfractured aquitard previous investigations utilizing permeability tests at a variety of scales keller et al 1989 indicated that bulk k at the site ranges from 3 5 0 11 m s to 1 2 10 10 m s advective displacements calculated on the basis of these k values lead to a wide range of predicted distributions of natural tracers after 11 000 years comparison of 18o distributions and simulated advection diffusion profiles provide a more precise constraint on advective displacement and hence on k the simulations cast in terms of a peclet number p v2t d ranging in value from 0 to 12 indicate that transport is diffusion controlled and that k is actually less than 1 2 10 11 m s p greater than 0 1 k 1 2 10 11 m s overestimates transport this result indicates that conventional permeability tests in very tight media tend to overestimate k in practical terms advective transport at the site is negligible and transport can be simulated with diffusion only p o

flow system controls of the chemical evolution of groundwater abstract isotopic and major ion analyses of 130 fresh and brackish groundwater samples reveal a strikingly consistent pattern of variation over 28 000 km 2 of the western canada sedimentary basin hydrodynamic interpretations based on drill stem tests and piezometric data reveal a pattern of broad regional flow from south to north however there is some evidence to suggest that patterns of groundwater flow have been influenced in the past by wisconsin glaciation all the permeable units appear to be recharged by meteoric water in the south where they outcrop or come close to the surface samples of groundwater collected down dip in each of six major sandstone units are progressively enriched in d 18 o na and cl for example the deepest waters of the artesian milk river aquifer are enriched by up to 70 and 15 with respect to the d and 18 o of the modern recharge waters the pattern of chemical evolution is strongly related to the hydraulic characteristics of individual units the isotopic composition is determined by the extent to which hydraulic conductivity has facilitated meteoric water flushing of connate water thus more permeable units and permeable zones within a unit tend to be isotopically lighter because of a more complete and more rapid invasion of meteoric water interestingly the largest conductivity values are found in some of the deepest units 1500 m consequently water in these deeper units have d and 18 o values which approach that of the recharge the major ion chemistry is controlled both by this process and a complex set of rock water interactions in addition to providing information about the chemical evolution of groundwater this study can begin to quantify the complex pattern of flushing in a large sedimentary basin

evaluating the sulfur isotopic composition of biodegraded petroleum the case of the western canada sedimentary basin abstract the sulfur isotopic composition 34s of petroleum is believed to be affected mainly by sulfur incorporation reactions into the sedimentary organic matter during the early diagenesis however secondary processes could affect the original 34s of oil under the effect of thermal maturity or of the microbial activity of biodegraded reservoirs in this study the different processes that may affect the 34s of in reservoir oils were assessed based on the sulfur content and isotopes of a series of oil and core samples coming from various reservoirs of the lower cretaceous mannville group western canada sedimentary basin wcsb based on the molecular study these samples appear to have reached various levels of maturity and biodegradation ranging from 0 to 6 5 on the biodegradation scale of peters and moldowan in addition mixing of organic matter coming from different source rocks was identified based on the comparison with extensive correlation studies performed in the wcsb investigation of the 34s shows a trend that seems a priori correlated to the level of biodegradation however a careful interpretation of molecular and sulfur isotope data leads to the conclusion that the observed 34s variations have rather to be ascribed to contributions of oils generated by various source rocks alternatively variations of 34s could neither be related to maturity differences nor to kinetic effects during organic sulfur compounds biodegradation in the case of some specific core samples showing a common origin based on biomarker study 34s variations might not be related to different sources but to secondary sulfur incorporation exchange processes occurring within the reservoir these processes would involve reduced sulfur species from bacterial sulfate reduction formed in situ or migrated into mannville reservoirs this hypothesis is supported by laboratory experiments showing sulfur exchange incorporation under plausible conditions for shallow reservoirs

the lunar regolith chemistry mineralogy and petrology the lunar regolith a several meter thick layer of unconsolidated debris forms the interface between the moon and its space environment the regolith forms from lithic sources by the destructional processes of comminution and the constructional processes of agglutinate formation in this manner a steady state soil can develop and will remain in a type of dynamic equilibrium until the system is disturbed by burial or mixing with new soil mixing takes place mainly on a local scale vertically through meters and horizontally over several kilometers lateral transport is a relatively inefficient process and therefore most of the lunar soil components were derived locally there is no evidence for preferential transport of the finer soil fractions relative to the coarser fractions the truly exotic derived at distances of tens of kilometers component is generally in low abundance 1 therefore remotely sensed data should provide a reasonably accurate picture of bedrock geology the chemical composition of the regolith varies with grain size the 10 m fraction is chemically fractionated from the bulk soil in most cases the 10 m fraction is enriched in al2o3 cao na2o k2o light rare earth elements and th and depleted in mgo feo mno and sc these systematics are largely a result of simple comminution with feldspar and friable mesostasis from local source rocks concentrating in the finest fraction there is evidence that agglutinate glass forms preferentially by fusion of the finest soil fractions therefore agglutinate glass like the 10 m soil fraction appears to be fractionated from bulk soil compositions highland soils are distinct from mare soils both chemically and petrologically soil samples collected near mare highland contacts are mixtures of the two lithologies mineral chemical systematics of monomineralic fragments in the lunar soil provide important clues to soil provenance they can in some cases sort out the highland mare contributions and in special cases can even further pinpoint a lithic source in theory lunar regolith cores can serve as solar probes recording the sun s activity over billions of years in practice this has generally not been the case the formation and evolution of most cores is still poorly understood for most we have not established how they formed for example how many depositional and erosional events were involved what the time span involved in the accretion of the sampled soil column was and how long that soil column has remained in situ without this information it is difficult if not impossible to read the sun s record more interdisciplinary studies on cores must be carried out before they can be used as solar probes

synthesis and model of formation water flow alberta basin canada based on a large amount of publicly available data several studies have previously examined the flow of formation waters in different parts of the alberta basin offering various interpretations as to the causes of the observed pressure regime and flow pattern however there has been no synthesis of these diverse studies on a basin wide basis accordingly these studies are critically reviewed in this paper and synthesized in a new basin scale model of the flow of formation waters in the alberta basin the proposed regional scale model has significant implications for understanding hydrocarbon migration pathways ore genesis the geothermal regime and deep waste disposal in the alberta basin several flow systems each one driven by a different mechanism are identified together with the main processes leading to the nonhydrostatic pressures observed in the basin two megahydrostratigraphic successions and associated flow systems are recognized the first succession corresponds to the pre cretaceous passive margin stage of basin development and consists of thick carbonate dominated aquifer systems separated by shaly aquitards and evaporitic aquicludes a northeastward basin scale flow system is driven by basin topography with recharge in montana and discharge in northeastern alberta southwest to northeast regional scale flow adjacent to the fold and thrust belt is probably the result of past tectonic processes the salinity of formation water in pre cretaceous aquifers is high and generally increases both northward and with depth this variability is the result of increased water rock reactions mineral solubility with increased temperatu e and of incomplete flushing by meteoric water as a result of salinity variations flow retarding buoyancy effects can be important the second megahydrostratigraphic succession corresponds to the post jurassic foreland stage of basin evolution and consists of thick shaly aquitard systems and relatively thin sandstone aquifers in the southwestern part of the basin flow in isolated aquifers is driven southwestward by erosional rebound in the thick intervening shales downdip toward the fold and thrust belt the salinity of formation waters in the post jurassic aquifers is low mixing of waters and interference between the major flow systems takes place along the pre cretaceous unconformity where successively older pre cretaceous aquifers subcrop from west to east flow in shallow lo al systems at the top of the sedimentary succession is driven by local topography

hydraulic and chemical pulse tests in a shut in chamber imbedded in an argillaceous formation numerical and experimental approaches hydraulic and chemical pulse tests were performed in four shut in chambers to obtain hydraulic and chemical parameters of the callovo oxfordian shale the osmotic tests i e chemical pulses were carried out by exchange of the formation water for a different solution either more or less concentrated two sets of two osmotic tests were done in march and october 2006 these osmotic tests are superimposed on a purely hydraulic response because of the drilling of the well causing a pressure drop the pressure records hydraulic and osmotic responses were interpreted using a 2 d model to obtain the hydraulic and chemical parameters the osmotic efficiency inferred for the callovo oxfordian shale is on the order of 0 012 for a concentration of 0 43 mol l 1 and 0 12 for a concentration of 0 086 mol l 1 these results suggest that the callovo oxfordian shale behaves as a weakly semipermeable membrane and only 0 1 0 15 mpa of the 0 2 0 5 mpa can be explained by these osmotic efficiency values

model near infrared optical constants of olivine and pyroxene as a function of iron content the imaginary coefficients of the complex index of refraction of olivine low ca orthopyroxene and high ca clinopyroxene are derived as a function of iron content and wavelength over the spectral region 0 4 to 2 5 m from reflectance spectra of powders and hapke radiative transfer theory reflectance spectra as a function of composition and grain size are computed and compared i find that while spectral effects of variations in these parameters are similar they are distinguishable variations in iron content do not explain all the observed spectral variations in the spectra of the samples investigated

structural evolution of the witch ground graben the witch ground graben is a nw se trending extensional basin in the central part of the northern north sea lying between the moray firth and the viking graben ne sw extension occurred from triassic to cretaceous times extension took place on listric normal faults along the sw margin with downthrow to the ne giving rise to the asymmetry of the basin one of the principal phases of fault controlled subsidence occurred in the lower cretaceous from the valanginian to albian compilation of biostratigraphic data from this interval shows the development of an increasing number of stratigraphic breaks across the basin from sw to ne these breaks increasing in time span also in this direction this is a result of rotation of the subsiding fault block on the listric extensional faults the rotation is recorded in dipmeter data and occurred in several distinct episodes the triassic the volgian and the valanginian to aptian in reconstructing a cross section of the basin the interpreted fault curvature is constrained by the observed rotation of bedding surfaces and the amount of extension across the listric faults is constrained by the observed basin subsidence a depth to decollement for the faults of 4 km below sea level and an extension across the basin of 40 are estimated

grain size evolution and fractionation trends in an experimental regolith the comminution of blocky planetary surfaces into fine grained regoliths was simulated by impacting a fragmental gabbro target 200 times with stainless steel projectiles diameter 6 35 mm mass 1 2g vi 1 35 km s initially the target fragments were 2 32 mm in size with a mean diameter of 15 2 mm which was reduced to 0 4 mm after 200 shots for the first 60 shots comminution was linear with cumulative kinetic energy and thus essentially linear with time the comminution efficiency however decreased at later stages this could be due to a change in fracture mechanism from predominantly intergranular to predominantly intragranular and or due to a change in partitioning of the projectile s kinetic energy from collisional fragmentation or large fragments at early times to cratering in a progressively finer grained medium at later stages mineral specific preferential comminution is abundantly observed in the modal make up of various grain size fractions plagioclase comminutes more readily than pyroxenes plagioclase initially present at 54 vol comprises typically 65 70 of the 125 250 m fraction pyroxenes initially at 33 are depleted to 20 25 this fractionation occurs in the earliest samples analyzed and is not a time dependent phenomenon bulk chemical analyses reveal a corresponding increase in al2o3 cao and na2o and a decrease in feo and mgo the finest grain sizes are generally the most severely affected by differential comminution similar if not exactly identical trends are abundantly documented for lunar soil samples these experimental findings illustrate that differential comminution is capable of producing fractionation in the finest grain sizes they diminish the need for prominent lateral and vertical transport of components otherwise foreign to a lunar soil sampling site as postulated by some workers on the basis of multivariate chemical mixing models

experimental support for a predictive osmotic model of clay membranes osmosis has been cited as a mechanism for explaining anomalously high fluid pressures in the subsurface clays and shales act as membranes and osmotic flux across these units may result in pressures sufficiently high to explain these anomalies the theoretical osmotic pressures as calculated solely from solution properties can be quite large however it is not yet resolved whether these geologic membranes are sufficiently ideal to generate such pressures

continental erosion and large scale relief a worldwide investigation of continental erosion is carried out by the study of large drainage basins on the basis of hydrological data environmental factors and basin relief distribution inside each basin mean geochemical and mechanical denudation rates are defined a multicorrelation analysis shows that the mechanical denudation rates ds are uncorrelated with environmental factors and correlated with mean basin elevation h while chemical denudation rates dd are insensitive to relief but correlated with mean annual precipitation furthermore two linear relationships between h and ds are detected 1 ds m 10 yr 419 10 6 h m 0 245 with v explained variance 95 1 this law concerns basins related to orogenies younger than 250 ma the negative intercept is interpreted as a continental sedimentation rate of 245 m m y an alternative model in which one invokes a critical elevation separating erosion from sedimentation is equally successful and leads to lower sedimentation rates 60 110 m m y for both models one derives from the slope of the adjustments erosion time constants on the order of 2 5 m y 2 ds m 10 yr 61 10 6 h m with v 86 5 this law concerns basins related to older orogenies the null intercept suggests the lack of continental storage because of the more important dispersion of the data the erosion time constant is calculated separately for each basin it ranges from 15 to 360 m y the tectonic implications of these results are discussed in particular the short time constant 2 5 m y agrees with orogenic uplift rates on the order of 1 mm yr observed in active mountain chains

organic maturity in the western canada sedimentary basin abstract organic maturity of strata in the western canada sedimentary basin has been investigated in numerous studies using petrological chemical and physical methods compilation of these data has facilitated a regional analysis of the maturity patterns and maturation history variation in maturity patterns can be divided into three levels basin wide 1st order regional 2nd order and local 3rd order first order variations are manifested by an overall increase in maturity of strata of the same age from east to west from the plains to the rocky mountain foothills and front ranges in response to progressively deeper burial and higher paleo geothermal gradients superimposed on this first order basinal scale variation in maturity are second and third order variations which reflect local differences in depth of burial conductive and advective heat transport or effects of thrust faulting maturity gradients in the axis of the basin are low averaging 0 10 log r omax km whereas in the front ranges and foothills the gradients are substantially greater average 0 25 log r omax km variations in maturity gradients reflect lower paleo geothermal gradients resulting from rapid sediment loading and subsequent unloading in the plains and higher conductive heat transport in the deformed belt the main component of maturity of most phanerozoic strata occurred during deep burial under upper cretaceous and or paleogene molasse in foredeeps developed in response to crustal loading during the easterly migration of the foreland fold and thrust belt as a result of the west to east propagation of deformation during the laramide orogeny deep burial maturation hydrocarbon generation and uplift occurred earlier in the foreland belt late cretaceous than in the plains to the east where the main component of maturity and hydrocarbon generation occurred as late as eocene in the plains because of the low maturity gradients a thick succession of strata currently is within the oil window in the deformed belt however higher maturity gradients have resulted in a thinner succession of strata within the oil window in response to higher paleo geothermal gradients strata in the deformed belt matured more quickly leading to more rapid hydrocarbon generation and migration than areas to the east in the southern part of the cordillera a significant component of maturation post dates structural deformation of the strata whereas in northeastern british columbia and adjacent parts of alberta maturity primarily pre dates structural deformation data from some deep bore holes and surface samples in the southern part of the cordillera provide evidence for maturity post dating or accompanying emplacement of major overthrust sheets tectonic burial in most areas however there is no clear evidence for the timing of maturity relative to faulting or evidence of frictional heating the maturity gradients and levels of maturity of surface and near surface strata in the western plains and rocky mountain foothills indicate that a succession several kilometres of paleogene strata were deposited in these regions foredeep and subsequently eroded in response to post laramide uplift

a slug test to assess the osmotic and hydraulic properties of argillaceous formations pulse tests in pressurized chambers represent a very efficient method to estimate the hydrodynamic properties of low permeability formations useful analytical solutions for purely hydraulic pulse test interpretation have been proposed in the present note an extension of the classical model by bredehoeft and papadopulos 1980 is developed for a single hydraulic and or chemical osmotic pulse test involving laplace transforms this solution is used to identify graphical variables in an osmotic pulse test record which can be used to estimate the relevant hydrochemical parameters

hydrogeology of formation waters northeastern alberta basin the hydrogeological study of formation waters in the northeastern part of the alberta basin defined as the area from 55 to 58 n and from 110 to 114 w is based on information from 12 475 wells 3187 formation water analyses 2531 drill stem tests and 452 030 core plug analyses because the study area covering approximately 76 000 km2 is located at the feather edge of the basin local topography and physiographic features particularly the athabasca river system exert a strong influence on the flow of formation waters in most of the aquifers generally temperature seems to be the main controlling factor on salinity distributions the salinity of formation waters increases in the vicinity of evaporitic beds and decreases close to the surface beca se of mixing with fresh meteoric water introduced through local flow systems the lower and middle devonian pre prairie aquifer systems beneath the regionally extensive prairie aquiclude are characterized by regional topographically driven flow updip to the northeast this updip flow is opposed by buoyancy forces caused by salinity increase with temperature downdip to the southwest the post prairie devonian aquifers are characterized by transitional flow regimes because of erosion at the sub cretaceous unconformity and outcrop at the athabasca river local physiographic influences are superimposed on basin scale regional flow in these aquifers hydraulic communication between the beaverhill lake cooking lake and grosmont aquifers is inferred in places caused by cooking lake reefs penetrating the intervening shales of the lower ireton aquitard finally the retaceous aquifers all can be described as having local flow regime characteristics with no buoyancy effects as a result of recharge in topographically high areas and discharge in low regions along the valleys of the athabasca river system the flow of formation waters in northeastern alberta played an important role in the formation of the huge athabasca oil sands deposits hydrocarbons that migrated into the area from the west were trapped into local reservoirs and biodegraded and washed by fresh meteoric water introduced by local flow systems environmentally the subsurface hydrogeology in the area imposes specific constraints on waste disposal in deep formations mostly because of the absence of a thick continuous regional aquitard and because most aquifers subcrop at shallow depth or crop out and discharge along the valleys of the athabasca river system and at the basin edge

dating penecontemporaneous dolomitization in carbonate reservoirs paleomagnetic petrographic and geochemical constraints the predominant dolomitization in the mississippian debolt formation western canada sedimentary basin was hypothesized to be early in three gas fields based on stable oxygen and carbon isotopic values and on strontium isotope ratios that are similar to postulated mississippian dolomite values and seawater ratios respectively as the absolute age could not be determined by this method paleomagnetism was used to place constraints on the age of the dolomitization the magnetic analyses on debolt specimens from the same wells revealed three magnetization components that could be tied to geologic diagenetic events 1 a low temperature 350 degreesc and coercivity 80 mt c component of primary or early diagenetic origin that is found mostly in the fine grained limestone and dolomitic muds the preservation of a primary or early diagenetic magnetization combined with the preservation of primary isotopic values indicates that little or no extrabasinal fluid flow is likely to have occurred thus in this particular area orogenically induced fluid flow cannot explain the presence of the cretaceous b magnetization consideration of the potential methods for forming this b component suggests that it is likely an in situ chemical remanence resulting from either hydrocarbon migration or dissolution and reprecipitation of fe rich minerals in the original pore fluids

analytical and numerical solutions for alternative overpressuring processes application to the callovo oxfordian sedimentary sequence in the paris basin france 1 previous studies that made use of basin models have shown that the normal geological evolution of the paris basin does not generate the observed albeit weak excess pressures in some shale layers of the basin other processes that may have created the overpressures currently neglected in such models are investigated here terms accounting for osmotic effects and tectonic stress changes are successively added to the diffusivity equation the effect of changes in outcrop boundary conditions is also calculated with a pseudo two dimensional analytical solution these solutions are applied to the callovo oxfordian shale formation in the eastern part of the paris basin france it is shown that a long term transient osmotic effect starting in the tertiary could explain in part the observed excess pressures in the callovo oxfordian shale assuming effective diffusion coefficients of 1 5 10 12 m2 s 1 in line with the measurements and a pore radius b around 20 a for the shales however because of the uncertainty on the value of the shale pore radius additional head measurements and osmotic experiments on samples should be made to fully establish the possibility of an osmotic process our study also shows that recent changes in hydrodynamic boundary conditions could also explain excess pressure distribution in this shale layer it is plausible that a combination of the two processes could best explain the distribution and intensity of the overpressures tectonic stress changes do not appear to be important it is shown that for such processes to maintain high pressures strong and recent increase in tectonic compressive stress would be required

stress field determinations in france by hydraulic tests in boreholes the stress field has been determined at eight different sites in france four in crystalline or metamorphic rocks four in sedimentary formations by hydraulic tests in boreholes for seven of these sites the complete stress field has been determined using the hydraulic tests on pre existing fractures htpf inversion method validity of the results is demonstrated by the good fit between a priori and a posteriori values for the data and by the low values of the a posteriori standard deviation on the unknowns for four sites results have been compared with those derived according to the hydraulic fracturing theory the two methods yield comparable results for the orientation of the maximum horizontal principal stress h a generally satisfactory fit for the magnitude of the minimum horizontal principal stress h but a very poor agreement for the magnitude of h this latter misfit has been attributed to the effect of fluid percolation prior to the actual opening of the fractures below a depth of 500 m a homogeneous h direction n150 e has been determined at the crystalline sites auriat echassieres le mayet de montagne chassoles all located in the northern massif central for three of these sites the vertical stress is significantly lower than the weight of overburden as computed from the rock density and the depth of the corresponding measurement at auriat and echassieres the stress field is consistent with a mostly strike slip faulting regime at le mayet de montagne and chassoles the maximum stress is vertical but nearly equal to h the stress field has been found to be much more heterogeneous at two of the four sites in sedimentary rocks because of the large variability in mechanical rock properties in such heterogeneous formations inversion with the htpf method must be limited to those data which pertain to the same rock horizon however because of its structure this heterogeneity does not restrict the possibility of defining large scale uniform principal stress directions all the results are consistent with the local seismotectonics

time to reach near steady state in large aquifers 1 a new analytical solution of the flow equation has been developed to estimate the time to reach a near equilibrium state in mixed aquifers i e having unconfined and confined portions following a large hydraulic perturbation near equilibrium is defined as the time for an initial aquifer perturbation to dissipate by an average 95 across the aquifer the new solution has been obtained by solving the flow system of a simplified conceptual model of a mixed aquifer using laplace transforms the conceptual model is based on two assumptions 1 the groundwater flow can be reduced to a horizontal 1 d problem and 2 the transmissivity a function of the saturated thickness is assumed constant on the unconfined portion this new solution depends on the storativity of the unconfined portion the lengths of the unconfined and confined portions and the transmissivity assumed to be constant and equal in both portions of the mixed aquifer this solution was then tested and validated against a numerical flow model where the variations of the saturated thickness and therefore variations of the transmissivity were either ignored or properly modeled the agreement between the results from the new solution and those from the numerical model is good validating the use of this new solution to estimate the time to reach near equilibrium in mixed aquifers this solution for mixed aquifers as well as the solutions for a fully confined or fully unconfined aquifer has been used to estimate the time to reach near equilibrium in 13 large aquifers in the world for those different aquifers the time to reach near equilibrium ranges between 0 7 kyr to 2 4 107 kyr these results suggest that the present hydraulic heads in these aquifers are typically a mixture of responses induced from current and past hydrologic conditions and thus climate conditions for some aquifers the modern hydraulic heads may in fact depend upon hydrologic conditions resulting from several past climate cycles

flow of variable density formation water in deep sloping aquifers review of methods of representation with case studies abstract distributions of freshwater hydraulic heads have been and continue to be used in the representation and analysis of groundwater flow including the flow of variable properties formation water in deep sloping aquifers because of variations in pressure temperature and salinity the flow of formation waters in sedimentary basins is driven by potential forces resulting from pressure and elevation topography differences by buoyancy resulting from density differences and by osmosis caused by temperature and concentration gradients because of variations in both fluid and rock properties it is not possible to define a flow potential to be used in representing and analysing the flow neither is there a force potential from which a flow driving force can be derived and which could be used in flow representation and analysis even if osmotic effects are neglected buoyancy still plays a role which in certain cases may be important in horizontal or near horizontal aquifers the lateral flow of variable density water is correctly represented by freshwater potentiometric surfaces and the vertical flow may be analysed using environmental hydraulic head distributions however the flow of formation waters in sedimentary basins is mostly along bedding in confined sloping aquifers in this case short of calculating and representing either the velocity or the impelling force distribution freshwater hydraulic heads remain the only tool available for representing and analysing the flow by neglecting buoyancy errors in flow strength and direction are introduced which become significant if a dimensionless driving force ratio exceeds a threshold value estimated to be around 0 5 the review of representation and analysis methods for the flow of variable properties formation water in deep sloping aquifers is illustrated with two case studies from the alberta and llanos sedimentary basins

lunar surface imaging polarimetry i roughness and grain size imaging polarimetry characterizes the physical nature of the lunar surface by the median size of the grains and by the roughness of the surface a video polarimeter was designed at observatoire de paris to produce at the telescope images of planetary surfaces in intensity degree of linear polarization flux of polarized light and other relevant photo polarimetric images with these images the median grain sizemdand mean roughness slope angle have been derived and mapped over characteristic lunar features the method is explained terrains of anomalous surface textures have been discovered the imbrian and eratosthenian mare surfaces worked by the long term accumulation of impacts and by space exposure produce a mature morphology characterized bymd 47 m and 10 irrespective of the composition of the material ejecta blankets around craters of copernican age or younger show smoother surfaces and larger grains pyroclastic deposits have the same roughness 10 but consist of grains too small to have been produced by mechanical impact comminution very specific terrain types have been discovered along the cliff of rupes recta and the crater birt which indicate clean rocks depleted of dust these anomalies may result from seismic action when an impact formed the recent nearby crater thebit a

development of rift basins illustrated by the structural evolution of the oseberg feature block 30 6 offshore norway the mesozoic tilted fault block in norwegian north sea block 30 6 containing the giant oseberg oil and gas field is used to illustrate basin development during the jurassic and cretaceous there is seismic evidence for an early rifting phase in the northern viking graben on which the jurassic cretaceous rifting phase early bathonian to berriasian is overprinted the oseberg structure is representative of other fault blocks bordering the northern viking graben axis planar normal faults and listric faults which were restricted to the rifting phase dominate both fault types exhibit syn fault sedimentation listric faulting is recognized on seismic sections by the differential tilting reverse drag antithetic faulting and a wedge shaped syn rift reflector package the initiation of rifting is dated by baselap onto pre rift reflectors and cessation is dated by an unconformity beneath the generally onlapping post rift sediments steeply dipping planar normal faults often active along previously established fault zones played a significant part in the post rift development of the basin the last movement on planar normal faults in the oseberg fault scarp becomes younger away from the rift axis and this produced the complex fault scarp visible on many seismic lines the topography defined by the post rift unconformity is a composite surface which formed in response to subsidence processes it is not the result of orogenic events such as the kimmerian 9orogeny9 footwall uplift associated with planar normal faults caused local unconformities in complex fault scarps and on fault block crests

bayesian inversion of a chloride profile obtained in the hydraulically undisturbed opalinus clay mass transport and paleo hydrological implications abstract the bdb 1 deep inclined borehole was drilled at the mont terri rock laboratory switzerland and enabled to acquire relevant data on porewater composition through the opalinus clay opa and its bounding formations petrophysical measurements were carried out and included water content water accessible porosity and grain density determination conservative anion profiles were obtained by aqueous leaching and out diffusion experiments performed on drillcore samples and revealed to be consistent with previous studies carried out at the rock laboratory level diffusive properties were also investigated using three experimental setups cubic out diffusion radial diffusion and through diffusion these transport parameters were used as a priori values in a bayesian inversion using a markov chain monte carlo method to interpret the chloride profile in the opalinus clay based on a peclet number analysis using the transport parameters formerly acquired a purely diffusive scenario enabled specifying the paleohydrogeological evolution of the mont terri site from the folding and thrusting of the jura mountains to present time and transport parameters

direct radiometric dating of hydrocarbon deposits using rhenium osmium isotopes rhenium osmium re os data from migrated hydrocarbons establish the timing of petroleum emplacement for the giant oil sand deposits of alberta canada at 112 5 3 million years ago this date does not support models that invoke oil generation and migration for these deposits in the late cretaceous most re os data from a variety of deposits within the giant hydrocarbon system show similar characteristics supporting the notion of a single source for these hydrocarbons the re os data disqualify cretaceous rocks as the primary hydrocarbon source but suggest an origin from older source rocks this approach should be applicable to dating oil deposits worldwide

hydrochemical signatures of deep groundwater circulation in a part of the himalayan foreland basin groundwater samples were analyzed from 71 springs and wells as part of a larger study in a region of compressional tectonic regime the study site covers the peshawar basin and surroundings in the himalayan foreland of pakistan the northern portion is mountainous and the water table is discontinuous in different intermontane valleys with abundant springs with normal and anomalous temperatures and composition the southern part is divided into isolated basins with a number of drilled deep and dug shallow wells hydrochemical signatures of elevated strontium sr sio2 boron b and the geothermometric signatures all indicate a deep circulation of the emerging groundwater moreover for several of the sample sites water chemical compositions measured spring and water well temperatures and reservoir temperatures calculated for spring waters all point to origin from deep horizons within the basin remarkable proximity of all the thermal and hydrochemical anomalies to major faults suggests that the waters ascended along these faults from greater depths the area is a natural western extension of the himalayan geothermal belt described in earlier literature for the eastern and central himalayas

basement heat flow in the western canada sedimentary basin abstract the effective thermal conductivity of the entire sedimentary succession is calculated at 487 locations in the western canada sedimentary basin based on net rock analyses and thermal conductivity values corrected for temperature and porosity effects an easterly trend of increasing values is caused by shallower burial depth and by a reduced proportion of low conductivity shales geothermal gradients calculated previously and corrected for pleistocene glaciations are used in estimating the basement heat flow after subtracting the heat generated by radioactive decay in the sedimentary strata the distribution of basement heat flow with values between 30 and 80 mw m 2 is linked with the complex structure of the basement which is comprised of archean blocks accreted terranes orogenic belts and magmatic arcs heat flow heat generation relations in alberta show that the reduced heat flow and the characteristic length scale for the uppercrust thermal layer are of the order of 35 mw m 2 and 6 km respectively

regional hydrogeology of the silurian and ordovician sedimentary rock underlying niagara falls ontario canada abstract due to concern over the potential for widespread groundwater contamination in the sedimentary rock underlying the niagara falls area this study was done to investigate the hydrogeology of the silurian and ordovician stratigraphy underlying the upper niagara river and the eastern niagara peninsula seven boreholes up to 150 m deep were drilled instrumented with multiple packer casing tested for permeability sampled for inorganic and organic solutes and monitored for hydraulic head to provide data for a conceptual model of regional groundwater flow results show that there are at least three distinct groundwater flow regimes in the bedrock the uppermost regime consists of fracture zones in the guelph and lockport formations within which hydraulic conductivity hydraulic head measurements and geochemical analyses indicate active groundwater circulation primarily discharging towards the niagara gorge and escarpment underlying the lockport formation are an overpressured high hydraulic head regime in the clinton upper cataract lower queenston formation and an underpressured low hydraulic head regime in the lower cataract upper queenston formation in both regimes geochemical analyses and permeability measurements indicate very old and saline groundwater which probably has undergone minimal migration since pre pleistocene time the implication based on the study so far is that potential groundwater contamination below the bottom of the lockport formation is probably not significant in the niagara falls area except adjacent to the niagara gorge where vertical permeability in the lower flow regimes may be enhanced

compositional variability of the marius hills volcanic complex from the moon mineralogy mapper m3 1 using the moon mineralogy mapper m3 we examine the marius hills volcanic complex for the first time from 0 46 to 2 97 m the integrated band depth at 1 m separates the mare basalts on the plateau in two units 1 a strong 1 m band unit of localized lava flows within the plateau that has similar olivine rich signatures to those of the nearby oceanus procellarum and 2 a weaker 1 m band unit that characterizes most of the basalts of the plateau which is interpreted as having a high calcium pyroxene signature domes and cones within the complex belong to the high calcium pyroxene plateau unit and are associated with the weakest 1 m band observed on the plateau this difference could be the result of higher silica content more opaque minerals and or a weaker olivine content of the magma finally the floor of marius crater has one of the strongest olivine rich signatures of the entire marius hills complex these compositional differences are indicative of the long and complex volcanic history of the region the first episode started before the emplacement of the surrounding basalts of the plateau and produced the high calcium pyroxene flows present on the plateau and their associated domes and cones the second episode occurred concurrently or slightly after the emplacement of the adjacent procellarum basalts and produced the olivine rich basalts seen within the plateau outside the plateau and in marius crater if the olivine content of the lava flows increases with time the olivine rich region on the floor of marius crater may represent one of the latest episodes of volcanism exposed on the marius hills complex

importance of thermo osmosis for fluid flow and transport in clay formations hosting a nuclear waste repository abstract three osmotic processes have been identified in clay rich media electro and chemo osmosis flows of water caused by salinity and electrical potential gradients have so far attracted almost exclusive attention but despite the recurring concern about the importance of thermo osmosis a flow of water driven by a temperature gradient in argillaceous media it remains largely neglected here we propose a new formalism for estimating the thermo osmotic permeability based on a theoretical analysis at the molecular and pore scale then upscaled we show that the thermo osmotic permeability can be estimated only from surface charge density temperature pore size and salinity the possible prominent role of thermo osmosis in compacted shale layers with a temperature gradient is then exemplified this first general estimate of the thermo osmotic permeability can be used to improve our understanding of the influence on fluid flow and pressure fields of the natural geothermal gradient in sedimentary basins which is required e g for safety assessments of nuclear waste repositories in shale layers

the effects of space weathering on apollo 17 mare soils petrographie and chemical characterization the lunar soil characterization consortium a group of lunar sample and remote sensing scientists has undertaken the extensive task of characterization of the finest fractions of lunar soils with respect to their mineralogical and chemical makeup these compositional data form the basis for integration and modeling with the reflectance spectra of these same soil fractions this endeavor is aimed at deciphering the effects of space weathering of soils on airless bodies with quantification of the links between remotely sensed reflectance spectra and composition a beneficial byproduct is an understanding of the complexities involved in the formation of lunar soil several significant findings have been documented in the study of the 2x whereas the abundance of agglutinitic glass increases by only 10 15 this is evidence for a large contribution from surface correlated nanophase fe0 to the is feo values particularly in the 10 m size fraction the surface nanophase fe0 is present largely as vapor deposited patinas on the surfaces of almost every particle of the mature soils and to a lesser degree for the immature soils keller et al 1999a it is reasoned that the vapor deposited patinas may have far greater effects upon reflectance spectra of mare soils than the agglutinitic fe0

role of aquitards in hydrogeochemical systems a synopsis abstract aquitards exert significant influence on the hydrogeochemistry of aquifer systems this influence is manifested somewhat differently depending on the relative position of aquitards within a system in the deeper regimes they are influential in the origin and distribution of brines and the development of geopressured zones in intermediate regimes they form multi layered aquifer systems and provide a source of reactive minerals and exchangeable ions in shallow regimes aquitards can influence the topography and drainage patterns this influences the relationship between the water table and the potentiometric surface of confined aquifers controls the rates of infiltration and discharge and controls whether the geochemical system is open or closed to exchange of carbon dioxide gas in coastal areas aquitards can determine the depth of the saltwater freshwater interface its distance from the shoreline and the position of the mixing zone that causes geochemical alteration of minerals and development of porosity

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

geothermal gradients hydrodynamics and hydrocarbon occurrences alberta canada using coal rank data and the demonstrated genetic link between the present hydrodynamic regime and geothermal gradient pattern it is possible to reconstruct the geothermal history of alberta over the past 60 m y palinspastic adjustment for tectonic compression caused by the major laramide thrusting shows that the predeformation isoreflectance lines increased logarithmically with depth in the late paleocene the geothermal gradient was about 23 c km 1 25 f 100 ft in the eastern alberta plains compared to about 30 c km 1 65 f 100 ft in the western alberta plains a regional trend opposite to the post laramide trends reconstruction of the early eocene surface indicates western uplands with geothermal gradients as low as 21 c km 1 15 f 00 ft and eastern lowlands with geothermal gradients of 27 c km 1 5 f 100 ft compared to the present situation this represents an enhanced topographic surface and a subdued geothermal gradient pattern the genetic relations of topography water table elevation hydrodynamic regime and geothermal gradient pattern in both the early eocene and the present conform to a model developed for any compacted sedimentary basin with subaerial relief in this model on a regional scale high topographic areas have high water table elevations with correspondingly high potentiometric surfaces these areas control the regional recharge of cold meteoric water and hence have low geothermal gradients areas of medium elevation exhibit regional lateral flow and intermediate geothermal gradients regional topographic lows correspond with low potentiometric surfaces and the regional discharge of warm formation waters from deep in the basin results in high geothermal gradients local topographic featur s cause perturbations in this picture study of both the regional pattern and fine detail of the early eocene and present topographic surfaces and geothermal gradient patterns shows the validity of the model the result of the second laramide orogenic pulse was therefore to reverse the geothermal gradient pattern resulting mainly from compaction flow and to impose a topographically controlled hydrodynamic regime with flow in the same direction but with a 9 c km 0 5 f 100 ft decreased geothermal gradient in western alberta and a 4 c km 0 2 f 100 ft increased geothermal gradient in eastern alberta as erosion proceeded during the tertiary the entire alberta basin warmed up until the present temperature regime was attained study of some major hydrocarbon occurrences shows a genetic link between the hydrocarbon occurrence and the present fluid regime which itself is controlled by the present topography for at least the significant upper cretaceous shallow gas reserves in southeastern alberta however their position may already have been determined as early as the beginning of the eocene by the topographic surface at that time therefore the extent to which the present topographic surface is responsible for hydrocarbon accumulation through gravity induced cross formational flow remains unknown because this process was operative as long ago as the early eocene what does not ap ear to be in doubt is the fact that gravity induced cross formational flow does control the hydrodynamic regime which in turn influences the geothermal gradient pattern and the accumulation of hydrocarbons

the structural evolution of the northern viking graben and its bearing upon extensional modes of basin formation recent advances in the understanding of rift basin formation coupled with the increasing public availability of seismic and well data across the northern viking graben 60 61 n have enabled a detailed analysis of its development two rifting episodes can be recognized late permian early triassic and bathonian ryazanian major regional unconformities thought to be primarily tectonic rather than eustatic in origin separate and subdivide the rifting episodes the earlier episode involved extension about a n s axis ensuing triassic mid jurassic thermal subsidence was accommodated on steep faults during the later episode a new ne sw fault trend was superimposed on pre existing patterns major block rotation marking active rifting ceased at the end of the ryazanian during the second post rift episode there was a progressive migration of active faulting towards the basin margins and as a result a widening with time of the area undergoing subsidence asymmetric subsidence of the central part of the basin was hinged at the western margin of the horda platform and accommodated to the nw on major faults within the tampen spur factors for the second rifting episode were calculated both by relating subsidence to extension and by measuring observed extension values calculated by both methods increase consistently towards the basin axis for both rifting and thermal subsidence phases but are greater for the latter phase subsidence patterns are similar for both rifting and thermal subsidence episodes so that there is vertical stacking of relatively thick sequences in the axis of the northern viking graben these factors preclude the application of models involving uniform and non uniform stretching and also preclude oblique extension depth dependent stretching is preferred

chemical and isotopic characterization of hydrocarbon gas traces in porewater of very low permeability rocks the example of the callovo oxfordian argillites of the eastern part of the paris basin abstract a methodology has been developed to determine chemical and carbon isotopic compositions of trace amounts of hydrocarbon gas compounds methane ethane propane iso and normal butane present as dissolved compounds in the porewater of the low permeability callovo oxfordian argillites in eastern paris basin france results indicate that the studied hydrocarbons contain significant amounts of ethane butane and propane in addition to methane carbon isotopic compositions reflect primarily thermogenic origin thermal cracking of organic matter and lack of any significant biodegradation because temperature did not exceed 50 c in the studied argillites investigated hydrocarbons must have originated in hotter deeper organic bearing formations possibly stephanian coals data supports the predominance of high maturity thermogenic gas in the upper part of the callovo oxfordian and low maturity thermogenic gas mixed with minor bacterially produced methane in the lower part of the formation a mixing between three end member gases models quite well the data one thermogenic gas with a low maturity 42 methane with a 13 c of 53 a gas with higher maturity 55 methane with a 13 c of 47 and a bacterial gas 99 45 methane with a 13 c of 80 this study illustrates that migration of hydrocarbon gases can take place in rocks with very low permeability and porosity such as compacted mudrocks given enough time it further suggests that the studied fluid migration and transfer in aquitards would help characterization and understanding of fluid movements in sedimentary basins as a complement to studies focused on water aquifers and hydrocarbon reservoirs chemical and isotopic composition of dissolved hydrocarbons in porewater can be used as natural tracers of fluid circulation in sedimentary basins in addition to more conventional tracers

supernormal fluid pressures in sedimentary rocks of southern ontario western new york state fluid pressures up to 1 7 times greater than hydrostatic have been measured in argillaceous paleozoic rocks of low permeability in southern ontario and western new york state these supernormal formation fluid pressures were measured at depths of 50 310 m using submersible pressure transducers with straddle packers and multiple packer casings isolating the test intervals measurements were obtained over periods of 7 46 months following casing installations the pressure measurements from 11 monitoring wells are compiled and supporting hydrogeologic data for 5 selected wells are used as examples to illustrate the occurrence of supernormal fluid pressures in the ordovician silurian and devonian sedimentary sequence of southern ontario and western new york state possible explanations for the occurrence of supernormal fluid pressures in sedimentary rock are evaluated considering the available geologic and hydrogeologic information obtained from the monitoring wells based on this review it is hypothesized

modeling subsurface flow in sedimentary basins groundwater flows that arise in sedimentary basins from the effects of topographic relief buoyant convection sediment compaction erosional unloading and combinations of these driving forces can be described using quantitative modeling techniques models can be constructed to consider the effects of heat and solute transport petroleum migration and the chemical interaction of water and rocks the accuracy of model predictions however is limited by the difficulty of predicting hydrologic properties of sediments on regional dimensions estimating past conditions such as topographic relief and knowledge of how physical and chemical processes interact over gelogic time scales progress in basin modeling will accelerate as hydrologic research efforts are better integrated with those of other specialities such as sedimentology rock mechanics and geochemistry

radiative transfer modeling of compositions of lunar pyroclastic deposits 1 while over 100 lunar pyroclastic deposits have been identified remotely their compositions remain poorly constrained in this work we determine the compositions of three lunar regional pyroclastic deposits which are likely to contain large amounts of glass and for which we have high quality ground based spectra the aristarchus plateau mare humorum and sulpicius gallus we use radiative transfer theory and employ measured optical constants of glasses to predict the bidirectional reflectance of a particulate glass surface as a function of fe and ti concentration particle size and maturity in order to find the best spectral match to the remotely observed deposits tools are not available to model the optical effects of the unusual geometries of the ilmenite laths in the black beads so we address their effects on spectra of the regional pyroclastic deposits using computational mixing we find that model spectra of pure glass as opposed to devitrified black beads provide good matches to all three regions radiative transfer modeling predicts iron contents of 21 20 and 17 wt feo for aristarchus humorum and sulpicius gallus respectively and suggests that all three regions are low in titanium a result supported by lunar prospector neutron spectrometer data however we find that a moderate ti glass mixed with a small fraction of black beads cannot be ruled out for the sulpicius gallus region

inverse modeling of annealing of fission tracks in apatite 2 application to the thermal history of the peace river arch region western canada sedimentary basin

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

possible effects of erosional changes of the topographic relief on pore pressures at depth formation fluid pressures are said to be anomalous or abnormal if they differ from hydrostatic for the depth considered explanations of the origin and maintenance of anomalies seldom include the possibility of delayed adjustment of subsurface pore pressures to erosional modifications of the topographic relief yet the present paper shows that it is entirely possible for subaerial erosion to generate pore pressure changes at great depths by cross formational energy transfer in realistic field conditions conversely pressures may survive changes in the topography and be in a transient state for hundreds to millions of years thus appearing anomalous at the time of observation according to calculations for the red earth region in alberta canada present pore pressures in the devonian immediately above the precambrian basement at a depth of approximately 1400 meters may have been induced originally by erosionally shaped topography during pliocene times 12 to 1 m y b p but be adjusting now to new boundary conditions created by the erosional exposure of the sub cretaceous unconformity a 12 adjustment may already have taken place during the last 300 thousand years leaving nearly 90 of pliocene age pressures to survive to date as slowly decaying transient pressure relicts of the geologic past in view of the possible erosional effects on pore pressures demonstrated in this paper the question of anachronous formation pressures may deserve consideration in problems related to deep basin hydrology including regional groundwater resource development migration and accumulation of hydrocarbons radioactive waste isolation dating of various geologic events and so on

characterization of transport properties of argillaceous sediments application to the callovo oxfordian argillite 1 we consider the case of a cylindrical cored specimen of a saturated argillaceous sediment located between two reservoirs filled with an electrolyte one of the boundaries of the sample is submitted to a sharp pressure or salinity change the migration of the resulting pressure or saline front through the core specimen is responsible for the apparition of an electrical field which is called the streaming potential the diffusion potential for a salinity gradient respectively the temporal variation of this electrical field is recorded with ag agcl nonpolarizable electrodes and used to monitor the evolution of the pressure or saline front between the two reservoirs there is a finite interval of time before which the steady state condition holds through the core in both cases the electrical potentials exhibit a relaxation with a relaxation time constant depending on the square of the length of the cylindrical core specimen and on its hydraulic or ionic diffusivity the experiments described here provide new methodologies to determine the hydraulic and ionic diffusivities of clay rich materials these experiments confirm also the predictions of a transport model developed recently for such materials and illustrate a powerful geophysical method to obtain transport properties not only in the laboratory but also in the field using a network of nonpolarizable electrodes to remotely monitor dissipation processes occurring inside the investigated system

regional hydrodynamics of the proposed high level nuclear waste repository sites in the texas panhandle abstract bedded salt in the palo duro basin area of the texas panhandle is being evaluated as possible host rock for a high level nuclear waste repository the two potential sites are underlain by three major hydrostratigraphic units a shallow freshwater aquifer system developed in the tertiary ogallala formation and the triassic dockum group a thick shale and evaporite aquitard developed in an upper permian evaporite sequence and a deep basin brine aquifer system predominantly developed in the wolfcamp series and the pennsylvanian system water level shut in pressure and specific gravity data from inventoried wells drill stem tests and long term pumping tests were used to construct potentiometric surfaces potentiometric profiles and pressure depth diagrams water in the ogallala and dockum aquifers predominantly flows horizontally and discharges to springs and wells equipotential patterns on potentiometric profiles indicate that some water may be moving downward from the ogallala into the dockum across an intervening confining unit as well as moving downward from the dockum across the shale and evaporite aquitard and into the deep basin aquifer system this is corroborated by the slope of pressure depth data which indicate the potential for regional downflow in the shale and evaporite aquitard equipotential patterns and pressure depth data indicate predominantly horizontal flow in the deep basin aquifer system which is influenced by permeability variations related to facies changes hydraulic gradients are flatter in the more permeable shelf shelf margin and fan delta facies and steeper in the less permeable deep basin facies

generation of high pore pressures in accretionary prisms inferences from the barbados subduction complex recent geological and geophysical exploration of several accretionary complexes reveals that pore pressures inside them are much higher than the hydrostatic values indirect inferences further suggest that such high pore pressures may be present inside most accretionary complexes in this study the mechanisms for generating excess pore pressures is investigated by focusing on the barbados ridge complex which is an end member of sediment rich accretionary prisms modeling is carried out using a two dimensional finite element procedure with constraints provided by the following data deep sea drilling project results on stratigraphy and lithology seismic results on sediment structure and thickness regional geology on tectonic history and laboratory measurements on mechanical properties of sediments coupling among the equations for fluid flow heat transfer and sediment deformation is made throughout the computation the results of the modeling predict that the principal decollement beneath the barbados ridge complex is a zone of high pore pressure high porosity and reversal in seismic velocity these characteristics may be responsible for the mechanical weakness of the decollement which allows continuous subduction of sediments below it and for its seismic signatures results of the modeling further suggest that tectonic overburden may be the most important mechanism for the generation of high pore pressures inside accretionary prisms the direct effect of tectonic compression is of secondary importance and the effect due to temperature increase with subduction is of little significance thrust faulting near the toe of accretionary prisms can disturb pore pressure patterns and produce localized highs rich sediment supply low permeability high subduction angle and high subduction velocity are all favorable factors in creating high pore pressures inside accretionary prisms

paleohydrology of variable density ground water flow systems in mature sedimentary basins example of the palo duro basin texas usa abstract the paleohydrology of mature sedimentary basins undergoing uplift and tilting deposition and erosion is studied by numerically modeling the flow of variable density ground water in regional flow systems consisting of both shallow freshwater aquifers and deep saline aquifers complex ground water flow patterns can exist when buoyancy forces dominate the hydraulic head gradients arising from topographic relief the relative magnitude of the two driving forces hydraulic gradient and buoyancy changes during the hydrodynamic development of a sedimentary basin that is undergoing topographic changes the relationship between the two driving forces and their effect on flow and transport is studied through coupled flow and solute transport simulations using an idealized model scenario modeling shows that increases in recharge rates can rapidly change hydrodynamic conditions from buoyancy dominated flow governed by variable density to gravity driven flow governed by topography because the dissolved mass responds much slower to changes in hydrologic boundary condition than does fluid pressure transient conditions occur whereby the solute distribution may not correspond to the simulated ground water flow pattern hydrodynamic scenarios were examined in the palo duro basin texas where observed fluid densities range between 1000 and 1150 kg m 3 the palo duro basin was affected by cenozoic uplift deposition and erosion causing modifications in topography and major changes in regional hydrodynamics during the last 15 myear although fluid pressures have largely equilibrated with topographic changes in the recent geologic past the distribution of dissolved mass evolves over a much longer time and the observed solute distribution in the basin as suggested by the geochemistry of the deep basin brines may represent some past state of the hydrodynamic system paleohydrologic simulations describe buoyancy dominated flow phenomena in the recent geologic past when the topographic relief across the basin was much lower than it is today prior to maximum basin uplift simulated flow patterns in the deep aquifers are characterized by convection cells in the western part of the basin where fluid densities increase with depth convection cells show clockwise fluid motion restricting recharge of shallow ground water to the upper part of the deep aquifers in the eastern part of the basin where fluid densities decrease with depth convection cells are characterized by counterclockwise fluid motion and reflect thermohaline convection with enhanced recharge due to continued basin uplift and subsequent erosional events buoyancy dominated flow phenomena diminish and the gravity driven flow component arising from topographic relief becomes dominant this study demonstrates that although present ground water flow circulation in the basin is not affected by the observed fluid densities the flow pattern history during cenozoic basin development is much more complex than that which would be expected from a gravity driven flow conceptualization assuming uniform fluid densities more important the model scenarios describe the interrelationship between geologic processes regional hydrodynamics and transport phenomena and its importance in explaining hydrologic and geochemical phenomena in sedimentary basins

a nontectonic origin for the present day stress field in the paris basin france the large scale stress patterns observed in intra plate areas are often considered to result from far field boundary forces that drive plate tectonics however no present day deformation has been detected in the french paris basin yet significant deviatoric stresses are measured in limestone formations observed above soft argillite layers encountered in this region further the pore pressure measured in the argillite is larger than that measured in the surrounding permeable zones these observations suggest a presently active source of stress in this sedimentary system we propose that this stress field is not related to tectonics but only to gravity acting on the series of visco elastic orthotropic geomaterials that fill up the basin this visco elastic response is linked to pressure solution effects activated by pore pressure transients related to climatic variations these pressure transients develop in the fracture system that affects some of the geomaterials and imply a time dependant deformation field with time constants related to those of climatic variations this model outlines the influence of time dependent material properties on the present day stress and pore pressure fields that prevail at various depths it may be considered as a possible loading mechanism for the analysis of intra plate seismicity

regional scale porosity and permeability variations peace river arch area alberta canada this study examines the large scale variability of porosity and permeability of the sedimentary rocks in the phanerozoic succession in the alberta part of the peace river arch area of the western canada sedimentary basin the study is based on about 450 000 core analyses at approximately 22 000 wells in an area of more than 165 000 km 2 plug scale porosity and permeability values are scaled up to the well scale by hydrostratigraphic unit resulting in two sets of about 16 000 values each for porosity and permeability unevenly distributed both areally and with depth the permeability frequency distributions are lognormal for most of the units or parts of the units the regional scale variability of porosity and permeability is quite high between 1 and 38 for porosity and 0 001 md and 3 d for permeability the clastic units of the foreland basin exhibit a relatively high correlation between permeability and porosity several areal trends and patterns are identified for groups of hydrostratigraphic units patterns that change gradually from one group to another it is hypothesized that the observed variability is caused by the dominance of the peace river arch carbonate deposition or compaction at various times throughout the evolution of the basin based on the predominant controlling factor the geological history can be divided into four periods arch influence during the early to middle devonian reefal carbonate deposition influence during the middle to late devonian passive margin influence during the late devonian to middle jurassic and orog nic influence since the middle jurassic

coupled fluid flow heat and mass transport and erosion in the alberta basin implications for the origin of the athabasca oil sands regional topography driven flow systems related to laramide tectonic rebound were simulated using two dimensional coupled fluid flow heat transport and solute transport numerical models to replicate present formation water salinity and temperature distributions and investigate the accumulation of the athabasca oil sands previous modelling of this system was replicated and it predicted repeated replacement of all basin formation water with freshwater during deposition of the oil sands due to high permeabilities to match present alberta basin temperature and salinity distributions model hydrostratigraphy permeabilities and heat fluxes were adjusted this revised model conducts fluids along the mannville aquifer rather than the upper devonian aquifer and replicates present salinity distributions assuming instantaneous uplift around 60 ma fluid fluxes in principal aquifers decrease by two orders of magnitude using new permeabilities resulting in primarily conductive heat transport thus genesis

polarimetry of moonlight a new method for determining the refractive index of the lunar regolith abstract we present a new method for remotely measuring the refractive index of the lunar regolith using polarised moonlight umov s law correlates the polarisation pmax of scattered moonlight and the albedo a of the scattering lunar regolith we discuss how deviations from this correlation have previously been linked to the so called polarimetric anomaly parameter pmax aa which was proposed by shkuratov and others as being related to variations in regolith grain size we propose a reinterpretation of that parameter we develop models of light scattering by regolith grains which predict that variation in the refractive index of regolith grains causes deviations from umov s law variations in other grain parameters such as grain size and degree of space weathering do not produce this deviation the models are supported by polarimetric measurements on powdered terrestrial materials of differing refractive index we derive a simple formula to express the relationship between refractive index and the deviation from umov s law and apply it to telescopic measurements of regions of the lunar surface we show that the aristarchus plateau and the marius hills regions both comprise materials of unusually low refractive index these results are consistent with recent estimates of the mineralogy of those areas picard and peirce craters in mare crisium are shown to contain material of low refractive index similar to highland regions as has been suggested by earlier studies of these craters

basin scale evolution of formation waters a diagenetic and formation water study of the triassic chaunoy formation paris basin abstract formation waters and their movements within basins are commonly attributed with responsibility for patterns of cementation and porosity loss within reservoirs and aquifers it is thus important to understand when and how waters move in the subsurface we have studied the evolution and movement of formation water in the triassic chaunoy formation of the paris basin nw europe to define the way in which the water has evolved and to interpret water movement patterns using mineral isotope and fluid inclusion data in conjunction with detailed formation water analyses the chaunoy formation is cemented with different types of dolomite calcite and quartz cement we have studied the evolution of waters in terms of oxygen carbon and strontium isotopes and salinity connate waters were meteoric in origin but strongly influenced by the proximity of a playa lake input of palaeo meteoric water which entered the chaunoy via eastern halite bodies resulted in highly saline formation water for the majority of the chaunoy formation from about 100 ma until and for some time after maximum burial saline waters spread into the aquifer initially taking a west north west trajectory and then switching to a west south west pattern in the eocene following the alpine orogeny and localised uplift of the basin margin the southern portion of chaunoy received fresh low salinity meteoric water it is likely that formation water was lost from the chaunoy in a more central part of the basin via sub vertical cross formational flow to the mid jurassic dogger formation to accommodate the influx of fresh water

sealing efficiency of shales the sealing efficiency of shale layers is studied through the hydraulic parameters which are required for sustaining overpressure during geologically significant periods assuming a 1d sedimentary complex composed of a sealing layer overlying a permeable one we give approximate solutions for the dissipation of a given initial overpressure the time constant for relaxation involves the thickness hydraulic conductivity and specific storage of the seal and also those of the permeable layer the values of the various hydraulic parameters are discussed it is argued first that the specific storage corresponding to plastic deformation during burial compaction is larger than the one which would correspond to elastic deformation when taking into account i plausible values for specific storage of the upper shale layer and ii the storage effect of the lower permeable layer it is found that a shale layer of several tens of m with an hydraulic conductivity of the order of 10 15 ms 1 maintains overpressure for 1 myr for such hydraulic parameter values in the absence of on going pressuring forces initial overpressures would decay with a time constant corresponding to a decrease by a factor e 2 7 of 1 myr this is interpreted as supporting a dynamic origin for observed abnormal pressures

determination of principal stress magnitudes using calcite twins and rock mechanics data abstract this paper proposes a new method for determining principal stress magnitudes based on the use of the deviatoric stress tensor determined from computer inversion of calcite twin data additional evaluation of the vertical stress weight of overburden or of the mean stress is enough to calculate the complete stress tensor we emphasize that the best reasoning consists of combining calcite twin analysis with rock mechanics data failure friction criteria because the determination of the six parameters of the absolute stress tensor is overconstrained