saline tracer visualized with three dimensional electrical resistivity tomography field scale spatial moment analysis 1 cross well electrical resistivity tomography ert was used to monitor the migration of a saline tracer in a two well pumping injection experiment conducted at the massachusetts military reservation in cape cod massachusetts after injecting 2200 mg l of sodium chloride for 9 hours ert data sets were collected from four wells every 6 hours for 20 days more than 180 000 resistance measurements were collected during the tracer test each ert data set was inverted to produce a sequence of 3 d snapshot maps that track the plume in addition to the ert experiment a pumping test and an infiltration test were conducted to estimate horizontal and vertical hydraulic conductivity values using modified moment analysis of the electrical conductivity tomograms the mass center of mass and spatial variance of the imaged tracer plume were estimated although the tomograms provide valuable insights into field scale tracer migration behavior and aquifer heterogeneity standard tomographic inversion and application of archie s law to convert electrical conductivities to solute concentration results in underestimation of tracer mass such underestimation is attributed to 1 reduced measurement sensitivity to electrical conductivity values with distance from the electrodes and 2 spatial smoothing regularization from tomographic inversion the center of mass estimated from the ert inversions coincided with that given by migration of the tracer plume using 3 d advective dispersion simulation the 3 d plumes seen using ert exhibit greater apparent dispersion than the simulated plumes and greater temporal spreading than observed in field data of concentration breakthrough at the pumping well

durango apatite fission track dating using length based age corrections and neutron fluence measurements by natural thorium thin films and natural u doped glasses calibrated through natural uranium thin films abstract in this work we present an approach for neutron fluence measurements based on natural thorium thin films and natural uranium doped glasses calibrated through natural uranium thin films to be used for dating with the fission track method ftm this neutron dosimetry approach allows the employment of ftm even when dating is carried out using low neutron thermalization facilities besides it makes possible the determination of the th u ratio of the mineral to be dated durango apatite which is often employed in ftm as an age standard was analyzed this apatite presented a fairly high th u ratio 29 9 1 7 th fissions were 18 12 and 10 of the total for irradiations where thermal to fast neutron flux ratios were 2 4 4 4 and 5 2 respectively these results show that th fission must be considered for this apatite when not well thermalized irradiation facilities are used the ratio between spontaneous and induced track length ls li close to 0 89 indicates a certain amount of rejuvenation of the age of durango apatite therefore its apparent age should be corrected the application of a technique based on track length measurements produced a corrected age of 29 7 1 1 ma consistent with the independent reference age of this apatite 31 4 0 5 ma this result represents a support for viability of the neutron dosimetry approach studied in this work for ftm

integration of hydrological and geophysical data beyond the local scale application of bayesian sequential simulation to field data from the saint lambert de lauzon site quebec canada adequate characterization of aquifer heterogeneity is critically important for the sustainable use protection and remediation of groundwater resources the combined use of hydrological and geophysical measurements is arguably the most effective means of achieving this objective in this regard significant progress has been made on the quantitative integration of geophysical and hydrological data at the local scale however the extension of such approaches to larger more regional scales remains a major research challenge in this paper we demonstrate the application of a recently developed regional scale hydrogeophysical data integration approach which is based on bayesian sequential simulation to a field database from quebec canada consisting of low resolution surface based geoelectrical measurements as well as high resolution direct push and borehole based measurements of the electrical and hydraulic conductivities the results of our study which involved the integration of data along an approximately 250 m long survey line confirm that this novel methodology with suitable adaptation is fully applicable to field data and has the potential of providing realistic estimates of the spatial distribution of hydraulic target parameters at the regional scale equally importantly through the generation of multiple stochastic realizations the methodology allows for quantitative assessment of the uncertainty associated with the inferred subsurface models which in turn is essential for interpreting subsequent predictions of the flow and transport characteristics of the studied region

phanerozoic low temperature evolution of the uruguayan shield along the south american passive margin the crystalline basement of uruguay was assembled during the brasiliano orogeny in the neoproterozoic era and was later affected by discrete tectonic activity a new multi method low temperature dataset including u th he ages from both zircon and apatite t t modelling and k ar dating of fine sericite fractions and fault gouge reveal a detailed post orogenic geological history spanning the phanerozoic eon the juxtaposition of the terranes that compose the area was achieved in the ediacaran period and post collision was marked by intense exhumation in which the crystalline basement reached near surface conditions by the early to mid palaeozoic regional subsidence promoted sedimentation in the parana basin until the permian covering and reheating much of the basement that is at present exposed afterwards deposition and volcanism were mostly confined to its current limits regional exhumation of the shield during the permo triassic exposed much of the northern portion of the basement and the south was further affected by the opening of the south atlantic ocean during the mesozoic little exhumation affected the uruguayan shield during the cenozoic as reflected in its modest topography the reactivation of inherited neoproterozoic structures influenced the development of mesozoic basins and the present day landscape supplementary material supplementary data sample locations u th he data and k ar data are available at https doi org 10 6084 m9 figshare c 3702043

the role of fission track dating in discrimination of provenance determination of single crystal ages by fission track dating analysis of zircons and subordinately apatites within a detrital heavy mineral assemblage together with frequency distribution and radial plot analysis of the measured ages permits identification of different age modes synopses are presented of published fission track provenance studies in north central victoria northeastern tasmania barbados the rockall trough the english wealden mexico utah and the central alps from authors

stochastic reservoir characterization using prestack seismic data reservoir characterization must be based on information from various sources well observations seismic reflection times and seismic amplitude versus offset avo attributes are integrated in this study to predict the distribution of the reservoir variables i e facies and fluid filling the prediction problem is cast in a bayesian setting the a priori model includes spatial coupling through markov random field assumptions and intervariable dependencies through nonlinear relations based on rock physics theory including gassmann s relation the likelihood model relating observations to reservoir variables including lithology facies and pore fluids is based on approximations to zoeppritz equations the model assumptions are summarized in a bayesian network illustrating the dependencies between the reservoir variables the posterior model for the reservoir variables conditioned on the available observations is defined by the a priori and likelihood models this posterior model is not analytically tra

use of high resolution geophysical data to characterize heterogeneous aquifers influence of data integration method on hydrological predictions 1 the integration of geophysical data into the subsurface characterization problem has been shown in many cases to significantly improve hydrological knowledge by providing information at spatial scales and locations that is unattainable using conventional hydrological measurement techniques the investigation of exactly how much benefit can be brought by geophysical data in terms of its effect on hydrological predictions however has received considerably less attention in the literature here we examine the potential hydrological benefits brought by a recently introduced simulated annealing sa conditional stochastic simulation method designed for the assimilation of diverse hydrogeophysical data sets we consider the specific case of integrating crosshole ground penetrating radar gpr and borehole porosity log data to characterize the porosity distribution in saturated heterogeneous aquifers in many cases porosity is linked to hydraulic conductivity and thus to flow and transport behavior to perform our evaluation we first generate a number of synthetic porosity fields exhibiting varying degrees of spatial continuity and structural complexity next we simulate the collection of crosshole gpr data between several boreholes in these fields and the collection of porosity log data at the borehole locations the inverted gpr data together with the porosity logs are then used to reconstruct the porosity field using the sa based method along with a number of other more elementary approaches assuming that the grid cell scale relationship between porosity and hydraulic conductivity is unique and known the porosity realizations are then used in groundwater flow and contaminant transport simulations to assess the benefits and limitations of the different approaches

long term landscape evolution and post rift reactivation in the southeastern brazilian passive continental margin taubate basin zircon zft and apatite aft fission track low temperature thermochronology was applied at the brazilian passive continental margin in order to understand and reconstruct the post rift evolution since the breakup of southwestern gondwana the thermochronological data obtained from samples of both the precambrian basement and the paleogene to neogene sedimentary rocks from the continental rift of southeastern brazil provided zft ages between 148 15 and 64 6 ma and aft ages of 81 8 29 3 ma these data clearly indicate syn and post rift reactivations during the early cretaceous with great emphasis on paleogene to neogene times integrating the results of older thermochronological studies the reactivation of the southeastern brazilian margin can be described in three main phases related to the rift to post rift evolution of se brazil in general zft and aft data yield spread values that become younger as samples are closer to the reactivated neoproterozoic shear zones and might reflect source area exhumation the analysis of zft and aft data allowed interpretations regarding the main phases that occurred in the study area related to the thermotectonic and tectono stratigraphic evolution in southeastern brazil

bayesian method for hydrogeological site characterization using borehole and geophysical survey data theory and application to the lawrence livermore national laboratory superfund site a stochastic bayesian approach for combining well logs and geophysical surveys for enhancing subsurface characterization is presented the main challenge we face is in creating the bridge to link between ambiguously related geophysical surveys and well data the second challenge is imposed by the disparity between the scale of the geophysical survey and the scale of the well logs our approach is intended to integrate and transform the well log data to a form where it can be updated by the geophysical survey and this tends to be a convoluted process our approach starts with generating images of the lithology conditional to well logs each lithology image is then used as the basis for generating a series of shaliness images conditional to well log data shaliness images are converted to resistivity images using a site specific petrophysical model relating between shaliness resistivity and lithology to create the necessary interface with the cross well resistivity survey the lithology and resistivity images are then updated using cross well electromagnetic resistivity surveys we explored the limits of the approach through synthetic surveys of different resolutions and error levels employing the relationships between the geophysical and hydrological attributes which are weak nonlinear or both the synthetic surveys closely mimic the conditions at the llnl superfund site we show that the proposed stochastic bayesian approach improves hydrogeological site characterization even when using low resolution resistivity surveys

probabilistic petrophysical properties estimation integrating statistical rock physics with seismic inversion a joint estimation of petrophysical properties is proposed that combines statistical rock physics and bayesian seismic inversion because elastic attributes are correlated with petrophysical variables effective porosity clay content and water saturation and this physical link is associated with uncertainties the petrophysical properties estimation from seismic data can be seen as a bayesian inversion problem the purpose of this work was to develop a strategy for estimating the probability distributions of petrophysical parameters and litho fluid classes from seismics estimation of reservoir properties and the associated uncertainty was performed in three steps linearized seismic inversion to estimate the probabilities of elastic parameters probabilistic upscaling to include the scale changes effect and petrophysical inversion to estimate the probabilities of petrophysical variables andlitho fluid classes rock physics equations provide the linkbetween reservoir properties and velocities and lin

evolution of the walvis ridge rio grande rise hot spot system implications for african and south american plate motions over plumes crystallization ages of volcanic rocks dredged or drilled from the walvis ridge ten sites and the rio grande rise one site have been determined by the 40ar 39ar incremental heating technique the fundamentally age progressive distribution of these basement ages suggests a common hot spot source for volcanism on the island of tristan da cunha along the walvis ridge and rio grande rise and for the formation of the continental flood basalts located in namibia africa and brazil south america the walvis ridge rio grande rise volcanic system evolved along a section of the south atlantic spreading axis as the african and south american plates migrated apart astride or in close proximity to an upwelling plume reconstructions of the spatial relationship between the spreading axis the tristan hot spot and the evolving walvis ridge rio grande rise volcanic feature show that at about 70 ma the spreading axis began to migrate westward away from the hot spot the resulting transition to intraplate hot spot volcanism along the walvis ridge and associated termination of rio grande rise formation also involved a northward migration of previously formed african seafloor over the hot spot rotation parameters for african motion over fixed hot spots i e absolute motion have been recalculated such that the predicted trail of the tristan hot spot agrees with the distribution of radiometric and fossil basement ages along the walvis ridge african absolute motion has been extended to the south and north american plates by the addition of relative motion reconstruction poles

heterogeneity patterns of quaternary glaciofluvial gravel bodies sw germany application to hydrogeology abstract the architecture of sedimentary bodies determines the heterogeneity of many aquifers thus for environmental risk assessment and quantification of clean up efficiencies determination of the spatial distribution of hydraulic properties is required in this study outcrop analogues of glaciofluvial gravel bed deposits are used for a process based analysis of sedimentary heterogeneities which in turn are transformed into hydraulic parameters three scales of heterogeneities are distinguished a the lithofacies scale is formed by unique transport and depositional processes that form the fundamental building blocks hydrofacies types b the depositional element scale shows distinct geometrical characteristics internal structure and bounding surfaces and determines the local distribution of lithofacies and hence the correlation structure of permeabilities c the architectural scale of gravel bodies is formed by the stacking of depositional elements which is controlled by the dynamics of aggrading paleofluvial systems comparison of numerous gravel pits in sw germany revealed three major architectural patterns of glaciofluvial gravel bodies that can be distinguished statistically by the preservation of depositional elements as well as the frequency of lithofacies types the facies analysis results in three conceptual facies models of proglacial river systems which are regionally classified as main intermediate and minor discharge types based on calculated and laboratory measured hydraulic properties of the various lithofacies types detailed outcrop wall maps were digitized into polygons of defined hydrofacies types by using the gis system arc info the two dimensional fields of hydraulic properties were then transferred into a numerical model of groundwater flow modeling results clearly illustrate that the three heterogeneity patterns of gravel bodies also have distinguishable hydraulic response characteristics

stochastic fracture simulation using pixel based multiple point geostatistics by integrating seismic radial anisotropy and well data applications in two hydrology sites we propose a pixel based multiple point simulation algorithm for stochastic simulation of near surface fractures using seismic radial anisotropy as secondary information the method borrows information from the training image of the fracture and anchoring within the secondary radial anisotropy data using wavelet based multiple point simulation framework the simulation was performed sequentially by sampling from the conditional cumulative density function ccdf of fracture conditioning to radial anisotropy for faster computation instead of calculating ccdf at each unknown location a limited number of ccdfs are calculated the patterns of the multiple point representation are extracted from the training image and are classified into multiple classes using the wavelet decomposition analysis each class is represented by a class prototype and ccdf during simulation the conditioning data are compared with the class prototypes and a random sample is generated from the ccdf of the best match class we validated the proposed simulation method using a synthetic fracture dataset a sensitivity analysis was also performed to show the impact of correlation between fracture and radial anisotropy and the resolution of the radial anisotropy results demonstrated that the reproduction of the fracture depends on its correlation with the radial anisotropy it was also observed that fracture reproduction is proportional to the resolution of the radial anisotropy we successfully applied our proposed model to two hydrogeological sites in which seismic radial anisotropy was obtained using the dispersion analysis of the surface wave

dating topography of the sierra nevada california using apatite u th he ages the upward motion of rock masses relative to the earth s surface has been documented for most of the main mountain belts using thermochronological and petrological techniques more fundamental to the physical processes of mountain building however is the motion of the earth s surface itself which remains elusive here we describe a technique for estimating the age of topographic relief by mapping the low temperature thermal structure imparted by river incision using the ages of apatites determined from their uranium thorium and helium contents the technique exploits horizontal variations in temperature in the shallow crust that result from range normal river drainages because cooling beneath ancient river valleys occurs earlier than beneath intervening ridges our results from the sierra nevada california indicate that two of the modern transverse drainages the kings and the san joaquin had developed deep canyons by the late cretaceous period suggesting that the high topography of the range is 50 60 million years older than generally thought

apatite fission track analysis apatite fission track aft analysis has been widely used during the past 30 years to constrain the low temperature thermal histories of many igneous metamorphic and sedimentary rocks in a wide range of geological settings applicable geological settings include orogenic belts rifted margins faults sedimentary basins cratons and mineral deposits the types of geologic problems that can be addressed include the timing and rates of tectonic events sedimentary basin evolution the timing of hydrocarbon generation and ore mineralization the absolute age of volcanic deposits the effects of major climatic changes on the near surface geothermal gradient and long term landscape evolution early work by naeser 1967 and wagner 1968 1969 first established the basic procedures that enabled the fission track dating method to be applied routinely to these geologic problems fleischer et al 1975 summarized the early studies of the broader discipline of nuclear track detection in different solid state materials more recent comprehensive overviews of fission track applications have been provided by naeser and mcculloh 1989 wagner and van den haute 1992 gallagher et al 1998 van den haute and de corte 1998 dumitru 2000 and gleadow et al 2002 etched natural fission tracks in several apatite grains are shown in figure 1 successful aft analysis is limited by the following 1 the availability of apatite from which useful aft data can be obtained often due to a lack of apatite of sufficient grain size and quality within available rock types or alternatively the lack of available rock samples due to minimal outcrop exposure or other reasons 2 economic considerations in terms of the time and money required to obtain sufficient aft data 3 the inherent limitations of aft data to resolve geological thermal history information often related to limited numbers of accumulated spontaneous fission tracks due to

spatial and temporal uplift history of south america from calibrated drainage analysis a multi disciplinary approach is used to analyze the cenozoic uplift history of south america residual depth anomalies of oceanic crust abutting this continent help to determine the pattern of present day dynamic topography admittance analysis and crustal thickness measurements indicate that the elastic thickness of the borborema and altiplano regions is 10 km with evidence for sub plate support at longer wavelengths a drainage inventory of 1827 river profiles is assembled and used to investigate landscape development linear inverse modeling enables river profiles to be fitted as a function of the spatial and temporal history of regional uplift erosional parameters are calibrated using observations from the borborema plateau and tested against continent wide stratigraphic and thermochronologic constraints our results predict that two phases of regional uplift of the altiplano plateau occurred in neogene times regional uplift of the southern patagonian andes also appears to have occurred in early miocene times the consistency between observed and predicted histories for the borborema altiplano and patagonian plateaux implies that drainage networks record coherent signals that are amenable to simple modeling strategies finally the predicted pattern of incision across the amazon catchment constrains solid sedimentary flux at the foz do amazonas observed and calculated flux estimates match suggesting that erosion and deposition were triggered by regional andean uplift during miocene times

quantitative integration of hydrogeophysical data conditional geostatistical simulation for characterizing heterogeneous alluvial aquifers high resolution geophysical parameter information as it can be provided for example by crosshole georadar and seismic tomography has proven to provide useful spatial information to complement traditional hydrological methods such as core analyses logging techniques and tracer or pumping tests quantitative integration of these diverse database components is one of the major challenges in the field of high resolution hydrogeophysics because of their different scales of measurement and the usually weak petrophysical relations among the measurements in this study we systematically explore the usefulness of a conditional stochastic simulation approach based on simulated annealing for this purpose first we generate a realistic model of an alluvial aquifer consisting of a 2d scale invariant porosity field on the basis of this model we generate synthetic neutron porosity logs and crosshole georadar tomographic surveys we then use the proposed geostatistical simulation approach to integrate this hydr

the chronology and tectonic style of landscape evolution along the elevated atlantic continental margin of south africa resolved by joint apatite fission track and u th sm he thermochronology atlantic type continental margins have long been considered passive tectonic settings throughout the entire postrift phase recent studies question the long term stability of these margins and have shown that postrift uplift and reactivation of preexisting structures may be a common feature of a continental margin s evolution the namaqualand sector of the western continental margin of south africa is characterized by a ubiquitously faulted basement but lacks preservation of younger geological strata to constrain postrift tectonic fault activity here we present the first systematic study using joint apatite fission track and apatite u th sm he thermochronology to achieve a better understanding on the chronology and tectonic style of landscape evolution across this region apatite fission track ages range from 58 3 2 6 to 132 2 3 6ma with mean track lengths between 10 9 0 19 and 14 35 0 22 m and mean u th sm he sample ages range from 55 8 31 3 to 120 6 31 4ma joint inverse modeling of these data reveals two distinct episodes of cooling at approximately 150 130ma and 110 90ma with limited cooling during the cenozoic estimates of denudation based on these thermal histories predict approximately 1 3 km of denudation coinciding with two major tectonic events the first event during the early cretaceous was driven by continental rifting and the development and removal of synrift topography the second event during the late cretaceous includes localized reactivation of basement structures as well as regional mantle driven uplift relative tectonic stability prevailed during the cenozoic and regional denudation over this time is constrained to be less than 1 km

porosity estimation in the fort worth basin constrained by 3d seismic attributes integrated in a sequential bayesian simulation framework abstractthe accurate inference of reservoir properties such as porosity and permeability is crucial in reservoir characterization for oil and gas exploration and production as well as for other geologic applications in most cases direct measurements of those properties are done in wells that provide high vertical resolution but limited lateral coverage to fill this gap geophysical methods can often offer data with dense 3d coverage that can serve as proxy for the variable of interest all the information available can then be integrated using multivariate geostatistical methods to provide stochastic or deterministic estimate of the reservoir properties our objective is to generate multiple scenarios of porosity at different scales considering four formations of the fort worth basin altogether and then restricting the process to the marble falls limestones under the hypothesis that a statistical relation between 3d seismic attributes and porosity can be inferred from well logs a bayesian sequential

estimating depth of investigation in dc resistivity and ip surveys in this paper the term depth of investigation refers generically to the depth below which surface data are insensitive to the value of the physical property of the earth estimates of this depth for dc resistivity and induced polarization ip surveys are essential when interpreting models obtained from any inversion because structure beneath that depth should not be interpreted geologically we advocate carrying out a limited exploration of model space to generate a few models that have minimum structure and that differ substantially from the final model used for interpretation visual assessment of these models often provides answers about existence of deeper structures differences between the models can be quantified into a depth of investigation doi index that can be displayed with the model used for interpretation an explicit algorithm for evaluating the doi is presented the doi curves are somewhat dependent upon the parameters used to generate the different models but the results are robust

hotspot tracks and the early rifting of the atlantic abstract many hotspot tracks appear to become the locus of later rifting as though the heat of the hotspot weakens the lithosphere and tens of millions of years later the continents are split along these weakened lines examples are the west coast of greenland east coast of labrador madeira hotspot the south coast of mexico north coast of honduras guyana hotspot and the south coast of west africa north coast of brazil st helena hotspot a modern day analog of a possible future rift is the snake river plain where the north american continent is being pre weakened by the yellowstone hotspot track this conclusion is based on reconstructions of the motions of the continents over hotspots for the past 200 million years the relative motions of the plates are determined from magnetic anomaly isochrons in the oceans and the motion of one plate is chosen ad hoc to best fit the motions of the plates over the hotspots however once the motion of this one plate is chosen the motions of all the other plates are prescribed by the relative motion constraints in addition to the correlation between the predicted tracks and sites of later continental breakup exposed continental shields correlate with the tracks their exposure may be the result of hotspot induced uplift which has led to erosion of their former platform sediment cover

uplift and denudation of the central alaska range a case study in the use of apatite fission track thermochronology to determine absolute uplift parameters apatite fission track thermochronology aftt on granitic samples collected in the central alaska range in conjunction with geologic constraints from basins to the north nenana basin and south cook inlet of the range is used to constrain the timing amount rate and pattern of surface uplift rock uplift and denudation since the late miocene the conversion from a thermal frame of reference apatite fission track data to an absolute frame of reference with respect to mean sea level which requires constraining the paleoland surface elevation the paleomean annual temperature and the paleogeothermal gradient is evaluated and shown to be viable in the context of an exhumed apatite partial annealing zone paz apatite ages at denali mount mckinley range from 16 ma near the summit 6 km elevation to 4 ma at 2 km elevation a distinctive break in slope in the apatite age profile at an elevation of 4 5 km also marked by a change in confined track length distributions marks the base of an exhumed apatite paz rock uplift and denudation are greatest at denali decreasing southward away from the mckinley strand of the denali fault system as shown by progressively older apatite ages 7 35 ma from a suite of samples along the kahiltna glacier a correlative decrease in topography occurs southward from the fault the central alaska range lies within an arc defined by the denali fault with the highest peaks including denali concentrated at the arc apex patterns of rock uplift and denudation within the central alaska range mimic topography between early and late miocene and possibly earlier the central alaska range was most likely an area of relative tectonic and thermal stability rock uplift denudation and mean surface uplift of the denali region began by the late miocene 5 6 ma being 8 5 km 5 7 km and 2 8 km respectively at average rates of 1 5 km m y 1 km m y and 0 5 km m y the amount of rock uplift denudation and surface uplift decreases to 3 km 2 km and 1 km at little switzerland some 45 km south of the denali fault we conclude that the topographic and rock uplift patterns of the central alaska range the shape and proximity of the mckinley strand of the denali fault to these patterns the timing of the onset of rock uplift and denudation at 5 6 ma and a significant change in relative plate motion between north america and the pacific plates circa 5 6 ma are all inherently related

evidence of post gondwana breakup in southern brazilian shield insights from apatite and zircon fission track thermochronology abstract apatite and zircon fission track thermochronology studies are applied to basement and sedimentary rocks from the sul rio grandense shield to unravel the tectonic history of the onshore southernmost brazilian margin the sul rio grandense shield is a major geotectonic feature of southernmost brazil that includes paleoproterozoic basement areas and neoproterozoic fold belts linked to the brasiliano pan african orogeny crustal reworking and juvenile accretion events related to this cycle were dated in the region between 900 and 500 ma and were responsible for the assembly of southwestern gondwana in southeastern south america apatite fission track aft ages range from 340 33 to 77 6 ma and zircon fission track zft ages range from ca 386 to 210 ma based on thermal history modeling the most part of the samples record an early cooling event during the carboniferous which reflect the main tectonic activity of the final stages of the gondwanides at the pacific margin of west gondwana subsequently the permo triassic cooling event is related to the last stages of the gondwanides with convergence along the southern border of western gondwana and consequent reactivation of n s and ne sw trending basement structures the onset of initial breakup of southwestern gondwana with opening of the south atlantic ocean is mostly recorded in the eastern terrain and zft ages show that the temperature during this period was high enough for total or at least partial resetting of fission tracks in zircon the last cooling event of the sul rio grandense shield records the final breakup between south america and africa which began during the late cretaceous however the cenozoic rapid cooling episode probably is a result of plate adjustment after breakup and neotectonic reactivation of faults associated with south atlantic rift evolution

stochastic inversion of tracer test and electrical geophysical data to estimate hydraulic conductivities 1 quantifying the spatial configuration of hydraulic conductivity k in heterogeneous geological environments is essential for accurate predictions of contaminant transport but is difficult because of the inherent limitations in resolution and coverage associated with traditional hydrological measurements to address this issue we consider crosshole and surface based electrical resistivity geophysical measurements collected in time during a saline tracer experiment we use a bayesian markov chain monte carlo mcmc methodology to jointly invert the dynamic resistivity data together with borehole tracer concentration data to generate multiple posterior realizations of k that are consistent with all available information we do this within a coupled inversion framework whereby the geophysical and hydrological forward models are linked through an uncertain relationship between electrical resistivity and concentration to minimize computational expense a facies based subsurface parameterization is developed the bayesian mcmc methodology allows us to explore the potential benefits of including the geophysical data into the inverse problem by examining their effect on our ability to identify fast flowpaths in the subsurface and their impact on hydrological prediction uncertainty using a complex geostatistically generated two dimensional numerical example representative of a fluvial environment we demonstrate that flow model calibration is improved and prediction error is decreased when the electrical resistivity data are included the worth of the geophysical data is found to be greatest for long spatial correlation lengths of subsurface heterogeneity with respect to wellbore separation where flow and transport are largely controlled by highly connected flowpaths

thermotectonic history of the southeastern brazilian margin evidence from apatite fission track data of the offshore santos basin and continental basement abstract the santos basin is the largest offshore sedimentary basin in the southeastern brazilian margin and originated by breakup of west gondwana in the early cretaceous we carried out a new thermochronological study by apatite fission track analysis from borehole samples of the santos basin and its continental basement to constrain the tectonic history of the southeastern brazilian margin apatite fission track central ages of the basement and borehole samples vary from 21 0 1 8 to 157 0 35 0 ma and from 6 5 1 1 to 208 0 11 0 ma respectively from thermal modeling the basement samples reached the maximum paleotemperatures during the final breakup of south america and africa the onshore basement and offshore basin record an early thermotectonic event during the late cretaceous linked to the uplift and denudation of the serra do mar and serra da mantiqueira maturation of the organic matter in the offshore basin is related with the progressive increase of the geothermal gradient due to burial the thermal modeling indicates that the oil generation window started at 55 25 ma the basement samples experienced the final cooling during the cenozoic with an estimated amount of denudation linked to the sedimentary influx in the offshore basin a rapid cooling during the neogene becomes evident and it is linked to the reactivation along precambrian shear zones and change of the paraiba do sul drainage system

flow regime and bedforms in a ridge and runnel system s e spain abstract during landward migration ridge and runnel systems are subjected to asymmetric oscillatory and or unidirectional flow regimes depending on the stage of development reached by these systems in the early stages of evolution when the ridge is situated in the upper shoreface the whole system is subjected to asymmetric oscillatory flow the runnel is under lower flow regime conditions and the ridge may be under upper or lower flow regime according to water depth and wave energy later when the ridge has migrated to a position on the foreshore the runnel is largely under a unidirectional lower flow regime while the ridge itself is under oscillatory upper flow regime when the ridge welds to berm it is largely emergent and exposed to high tide swash action under upper flow regime conditions the runnel is eventually filled with sand and transformed into a low lying area all these types grade laterally into each other one or more ridge and runnel systems can occur at the same time wave energy tide level and position of the ridge control the variations in the characteristics of the ridge and also the position of the zones of bedforms found at the upper shoreface

impact of rock physics depth trends and markov random fields on hierarchical bayesian lithology fluid prediction early assessments of petroleum reservoirs are usually based on seismic data and observations in a small number of wells decision making concerning the reservoir will be improved if these data can be integrated and converted into a lithology fluid map of the reservoir we analyze lithology fluid prediction in a bayesian setting based on prestack seismic data and well observations the likelihood model contains a convolved linearized zoeppritz relation and rock physics models with depth trends caused by compaction and cementation well observations are assumed to be exact the likelihood model contains several global parameters such as depth trend wavelets and error parameters the inference of these is an integral part of the study the prior model is based on a profile markov random field parameterized to capture different continuity directions for lithologies and fluids the posterior model captures prediction and model parameter uncertainty and is assessed by markov chain monte carlo simulation base

post breakup tectonics in southeast brazil from thermochronological data and combined inverse forward thermal history modeling the continental margin of southeast brazil is elevated onshore tertiary basins and late cretaceous paleogene intrusions are good evidence for post breakup tectono magmatic activity to constrain the impact of post rift reactivation on the geological history of the area we carried out a new thermochronological study apatite fission track ages range from 60 7 1 9 ma to 129 3 4 3 ma mean track lengths from 11 41 0 23 mm to 14 31 0 24 mm and a subset of the u th he ages range from 45 1 1 5 to 122 4 2 5 ma results of inverse thermal history modeling generally support the conclusions from an earlier study for a late cretaceous phase of cooling around the onshore taubate basin for a limited number of samples the first detectable period of cooling occurred during the early tertiary the inferred thermal histories for many samples also imply subsequent reheating followed by neogene cooling given the uncertainty of the inversion results we did deterministic forward modeling to assess the range of possibilities of this tertiary part of the thermal history the evidence for reheating seems to be robust around the taubate basin but elsewhere the data cannot discriminate between this and a less complex thermal history however forward modeling results and geological information support the conclusion that the whole area underwent cooling during the neogene the synchronicity of the cooling phases with andean tectonics and those in ne brazil leads us to assume a plate wide compressional stress that reactivated inherited structures the present day topographic relief of the margin reflects a contribution from post breakup reactivation and uplift

boundary roughness and bedforms in the surf zone hydrodynamical models of the nearshore system frequently assume that a single friction coefficient is sufficient to represent flow conditions at a point in the surf zone furthermore models attempting to relate bed configuration to surf zone flows have relied primarily upon the wave orbital velocity as an indicator of potential bedforms and thus as the control on boundary roughness the data presented here point out potential errors arising from either of these approaches the results of a field experiment conducted at wendake beach ontario show that at a single location in an active surf zone the darcy weisbach friction coefficient f varied by approximately 250 in this case between 0 016 and 0 041 it is also shown that existing bedform models based upon primary wave motions alone do not accurately predict conditions at this study site for a relatively constant wave orbital velocity and velocity asymmetry it is found that changes in bed roughness as a result of bedform development are reflected mainly in the vertical profile of the longshore current velocity a sequence of bedforms from oscillatory ripples through flat bed is inferred from the data and found to be supported by diver observations and preserved primary sedimentary structures

improved resolution in bayesian lithology fluid inversion from prestack seismic data and well observations part 1 methodology the focus of our study is lithology fluid inversion with spatial coupling from prestack seismic amplitude variation with offset avo data and well observations the inversion is defined in a bayesian setting where the complete solution is the posterior model the prior model for the lithology fluid lf characteristics is defined as a profile markov random field model with lateral continuity each vertical profile is further given as an inhomogeneous markov chain model upward through the reservoir the likelihood model is defined by profile and it relates the lf characteristics to the seismic data via a set of elastic material parameters and a convolution model the likelihood model is approximated the resulting approximate posterior model is explored using an efficient block gibbs simulation algorithm the inversion approach is evaluated on a synthetic realistic 2d reservoir seismic avo data and well observations are integrated in a consistent manner to obtain predictions of the lf characteristics wi

an effective bayesian model for lithofacies estimation using geophysical data 1 a bayesian model coupled with a fuzzy neural network bfnn is developed to enhance the use of geophysical data in lithofacies estimation prior estimates are inferred from borehole lithofacies measurements using indicator kriging and posterior estimates are obtained by updating the prior using geophysical data the novelty of this study lies in the use of the fuzzy neural network for the inference of the likelihood function this allows spatial correlation of lithofacies as well as nonlinear cross correlation between lithofacies and geophysical attributes to be incorporated into lithofacies estimation the effectiveness of bfnn is demonstrated using synthetic data emulating measurements at the lawrence livermore national laboratory llnl site

generation of 3 d hydrostratigraphic zones from dense airborne electromagnetic data to assess groundwater model prediction error we present a new methodology to combine spatially dense high resolution airborne electromagnetic aem data and sparse borehole information to construct multiple plausible geological structures using a stochastic approach the method developed allows for quantification of the performance of groundwater models built from different geological realizations of structure multiple structural realizations are generated using geostatistical monte carlo simulations that treat sparse borehole lithological observations as hard data and dense geophysically derived structural probabilities as soft data each structural model is used to define 3 d hydrostratigraphical zones of a groundwater model and the hydraulic parameter values of the zones are estimated by using nonlinear regression to fit hydrological data hydraulic head and river discharge measurements use of the methodology is demonstrated for a synthetic domain having structures of categorical deposits consisting of sand silt or clay it is shown that using dense aem data with the methodology can significantly improve the estimated accuracy of the sediment distribution as compared to when borehole data are used alone it is also shown that this use of aem data can improve the predictive capability of a calibrated groundwater model that uses the geological structures as zones however such structural models will always contain errors because even with dense aem data it is not possible to perfectly resolve the structures of a groundwater system it is shown that when using such erroneous structures in a groundwater model they can lead to biased parameter estimates and biased model predictions therefore impairing the model s predictive capability

multivariate analysis of cross hole georadar velocity and attenuation tomograms for aquifer zonation 1 we have investigated the potential of combining cross hole georadar velocity and attenuation tomography as a method for characterizing heterogeneous alluvial aquifers a multivariate statistical technique known as k means cluster analysis is used to correlate and integrate information contained in velocity and attenuation tomograms cluster analysis allows us to identify objectively the major common trends in the tomographic data and thus to reduce the information to a limited number of characteristic parameter combinations the application of this procedure to two synthetic data sets indicates that it is a powerful tool for converting the complex relationships between the tomographically derived velocity and attenuation structures into a lithologically and hydrologically meaningful zonation of the probed region in addition these synthetic examples allow us to evaluate the reliability of further petrophysical parameter estimates we find that although absolute values of the tomographically inferred petrophysical parameters often differ significantly from the actual parameters the clustering approach enables us to reliably identify the major trends in the petrophysical properties finally we have applied the approach to a cross hole georadar data set collected in a well studied alluvial aquifer a comparison of the clustered tomographic section with well log data demonstrates that our approach delineates the hydrostratigraphic zonation

bayesian lithology fluid prediction and simulation on the basis of a markov chain prior model a technique for lithology fluid lf prediction and simulation from prestack seismic data is developed in a bayesian framework the objective is to determine the lf classes along 1d profiles through a reservoir target zone a stationary markov chain prior model is used to model vertical continuity of lf classes along the profile the likelihood relates the lf classes to the elastic properties and to the seismic data and it introduces vertical correlation because the seismic data are band limited an approximation of the likelihood model provides an approximate posterior model that is a markov chain the approximate posterior can be assessed by an exact and efficient recursive algorithm the lf inversion approach is evaluated on a synthetic 1d profile that is inspired by a north sea sandstone reservoir with a realistic wavelet colored noise model and a s n ratio of three in the seismic data the results are reliable the lf classes and the interfaces between zones are largely correct the prediction unce

heterogeneous aquifer characterization from ground penetrating radar tomography and borehole hydrogeophysical data using nonlinear bayesian simulations it is known that the heterogeneity of hydraulic conductivity drives the groundwater flow and the transport of contaminants however in conventional characterization methods the lack of densely sampled hydrological data does not permit us to describe the aquifer heterogeneity at an appropriate scale in this study we integrate ground penetrating radar gpr tomographic data with hydraulic conductivity logs to estimate the hydraulic conductivity of a heterogeneous unconsolidated aquifer at a decimetric scale between two boreholes the integration of these different data sets is achieved using a nonlinear bayesian simulation algorithm the prior hydraulic conductivity distribution is estimated under gaussian hypothesis by simple kriging of the hydraulic well data the likelihood of hydraulic conductivity given the relative permittivity and the electrical conductivity functions is obtained from a kernel probability density function estimator that describes the in situ relationship between the electric and the hydraulic properties measured along boreholes the proposed method is tested on a synthetic heterogeneous model of permeability to validate the methodology we show that permeability realizations obtained from the proposed algorithm present a higher correlation with the synthetic model than other classical simulation methods the method is then applied on data acquired over an unconsolidated aquifer located in saint lambert de lauzon quebec canada the data set consists of measurements from i gpr crosshole acquisition ii cone penetration testing with pressure measurement combined with soil moisture resistivity and iii a borehole electromagnetic flowmeter by using the presented bayesian approach we generated multiple hydraulic conductivity realizations that are in good agreement with the hydrogeological model of the area

field characterization and data integration to define the hydraulic heterogeneity of a shallow granular aquifer at a sub watershed scale providing a sound basis for aquifer management or remediation requires that hydrogeological investigations carried out to understand groundwater flow and contaminant transport be based on representative data that capture the heterogeneous spatial distribution of aquifer hydraulic properties this paper describes a general workflow allowing the characterization of the heterogeneity of the hydraulic properties of granular aquifers at an intermediate scale of a few km2 the workflow involves characterization and data integration steps that were applied on a 12 km2 study area encompassing a decommissioned landfill emitting a leachate plume and its main surface water receptors the sediments composing the aquifer were deposited in a littoral sublittoral environment and show evidence of small scale transitional heterogeneities cone penetrometer tests cpt combined with soil moisture and electrical resistivity smr measurements were thus used to identify and characterize spatial heterogeneities in hydraulic properties over the study area site specific statistical relationships were needed to infer hydrofacies units and to estimate hydraulic properties from high resolution cpt smr soundings distributed all over the study area a learning machine approach was used due to the complex statistical relationships between colocated hydraulic and cpt smr data covering the full range of aquifer materials application of this workflow allowed the identification of hydrofacies units and the estimation of horizontal hydraulic conductivity vertical hydraulic conductivity and porosity over the study area the paper describes and discusses data acquisition and integration methodologies that can be adapted to different field situations while making the aquifer characterization process more time efficient and less labor intensive

hydrogeophysical data integration at larger scales application of bayesian sequential simulation for the characterization of heterogeneous alluvial aquifers knowledge of the spatial distribution of hydraulic conductivity k within an aquifer is critical for reliable predictions of solute transport and the development of effective groundwater management and or remediation strategies while core analyses and hydraulic logging can provide highly detailed information such information is inherently localized around boreholes that tend to be sparsely distributed throughout the aquifer volume conversely larger scale hydraulic experiments like pumping and tracer tests provide relatively low resolution estimates of k in the investigated subsurface region as a result traditional hydrogeological measurement techniques contain a gap in terms of spatial resolution and coverage and they are often alone inadequate for characterizing heterogeneous aquifers geophysical methods have the potential to bridge this gap the recent increased interest in the application of geophysical methods to hydrogeological problems is clearly evidenced by the formation and rapid growth

denudation history of the bocaina plateau serra do mar southeastern brazil relationships to gondwana breakup and passive margin development abstract the bocaina plateau which is situated on the eastern flank of the continental rift of southeastern brazil is the highest part of the serra do mar topographic relief in this area is suggested to be closely related to its complex tectono magmatic evolution since the breakup of western gondwana and opening of the south atlantic ocean apatite fission track ages and track length distributions from 27 basement outcrops were determined to assess these hypotheses and reconstruct the denudation history of the bocaina plateau the ages range between 303 32 and 46 5 ma and are significantly younger than the stratigraphic ages mean track lengths vary from 13 44 1 51 to 11 1 1 48 m with standard deviations between 1 16 and 1 83 m contrasting ages within a single plateau and similar ages at different altitudes indicate a complex regional tectonothermal evolution the thermal histories inferred from these data imply three periods of accelerated cooling related to the early cretaceous continental breakup early cretaceous alkaline magmatism and the paleogene evolution of the continental rift of southeastern brazil the oldest fission track ages 200 ma were obtained in the serra do mar region suggesting that these areas were a long lived source of sediments for the parana bauru and santos basins

quantitative constraints on the rate of landform evolution derived from low temperature thermochronology in recent years the nature of the complex interactions between the solid earth and the overlying atmosphere has been the subject of much debate england and molnar 1990 whipple et al 1999 braun et al 1999 does erosion play an important role in the dynamics of mountain building is there a strong feedback into the balance of forces at the crustal scale from mass transport by erosional and depositional processes at the earth s surface or does erosion passively react to changes in the earth s surface topography to shape mountains with tectonic forces originating in the underlying convecting mantle dominating the dynamics of plate interactions and crustal deformation at convergent plate margins the answers to these fundamental questions lie in our ability to determine the rate at which surface processes can react to tectonic forcing whipple et al 1999 where erosion is efficient the coupling will be strong as the rate of change of surface loading by mass transport will be similar to the rate of creation of topography by crustal deformation this may lead to a concentration of deformation and thus exhumation in regions of intense erosion koons 1990 willett et al 1993 beaumont et al 2001 koons et al 2002 2003 braun and pauselli 2004 where erosion is relatively inefficient mountain building is the result of a balance between internal driving forces and those originating from the deflection of an upper free surface there is no feedback from erosional processes low temperature thermochronology such as u th he he or fission track ft dating in apatite and zircon provides information on the rate at which rocks cool as they are exhumed towards the cold earth surface duddy et al 1988 warnock et al 1997 farley 2000 reiners and farley 1999 because the

comparing contiguous high and low elevation continental margins new u th he constraints from south brazil and an integration of the thermochronological record of the southeastern passive margin of south america abstract the southeastern coast of south america is an example of the complexity of passive continental margins as it displays both high and low elevation segments despite sharing a similar pre rift geological history and structural configuration as such it is a prime candidate for investigating debated questions concerning the evolution of passive margins such as the tectonic mechanisms driving uplift their relationship to rifting and continental break up and why some margins are elevated when others are not in this contribution we present new u th he data from a low altitude portion of the south american passive margin in south brazil the sul rio grandense shield and interpret it in the context of the regional thermochronological record new results produce widespread apparent ages and reveal a complex exhumation history from the early paleozoic onwards including reheating during paleo mesozoic sedimentation for most of the study area however final exhumation was achieved at the latest during the rifting and early opening of the south atlantic ocean 135 ma to 100 ma in spite of the presence of major neoproterozoic shear zones the inherited ne sw structural framework seems not to have strongly influenced the thermochronological record the new data were integrated into a large compilation of apatite fission track and u th he results from southeast south america in order to compare regional trends and investigate possible tectonic controls in the exhumation history low elevation areas of the passive margin consistently record complex pre rift cooling histories while high elevation areas experienced significant upper cretaceous paleogene uplift associated with the reactivation of neoproterozoic shear zones because the inherited structural features of both segments are similar plate dynamics alone cannot be responsible for the variating response hence mantellic processes associated with post rift alkaline magmatism may have affected the contrasting exhumation histories this process was probably controlled by important south atlantic fracture zones

geostatistical inference using crosshole ground penetrating radar high resolution tomographic images obtained from crosshole geophysical measurements have the potential to provide valu able information about the geostatistical properties of unsaturat ed zonehydrologic statevariablessuchasmoisturecontent un der drained or quasi steady state conditions the moisture con tentwillreflectthevariationofthephysicalpropertiesofthesub surface which determine the flow patterns in the unsaturated zone deterministicleast squaresinversionofcrossholeground penetrating radargprtraveltimesresultinsmooth minimum variance estimates of the subsurface radar wave velocity struc ture whichmaydiminishtheutilityoftheseimagesforgeostatis tical inference we have used a linearized stochastic inversion technique to infer the geostatistical properties of the subsurface radar wave velocity distribution using crosshole gpr travel times directly expanding on a previous study we have deter minedthatitispossibletoobtainestimatesofglobalvarianceand mean velocity values of the subsurface as well as the correlation lengths describing the subsurface velocity structures accurate estimation of the global variance is crucial if stochastic realiza tions of the subsurface are used to evaluate the uncertainty of the inversion estimate we have explored the full potential of the geostatisticalinferencemethodusingseveralsyntheticmodelsof varying correlation structures and have tested the influence of different assumptions concerning the choice of covariance func tionanddatanoiselevel inaddition wehavetestedthemethod ology on traveltime data collected at a field site in denmark there inferred correlation structures indicate that structural dif ferences exist between two areas located approximately 10 m apart anobservationconfirmedbyagprreflectionprofile fur thermore the inferred values of the subsurface global variance and the mean velocity have been corroborated with moisture content measurements obtained gravimetrically from samples collectedatthefieldsite

migrating cretaceous eocene magmatismin the serra do mar alkaline province se brazil melts from the deflected trindade mantle plume department of geological sciences university of durham south road durham dh1 3le uk department of earth sciences university of cambridge downing street cambridge cb2 3eq uk department of physics the university newcastle upon tyne ne1 7ru uk department of geology mcmaster university 1280 main street west hamilton ont canada l8s 4m1 departmento de geoquimica e recursos minerais instituto de geociencias universidade de brasilia

estimating the hydraulic conductivity at the south oyster site from geophysical tomographic data using bayesian techniques based on the normal linear regression model this study explores the use of ground penetrating radar gpr tomographic velocity gpr tomographic attenuation and seismic tomographic velocity for hydraulic conductivity estimation at the south oyster site using a bayesian framework since site specific relations between hydraulic conductivity and geophysical properties are often nonlinear and subject to a large degree of uncertainty such as at this site we developed a normal linear regression model that allows exploring these relationships systematically although the log conductivity displays a small variation s 2 5 0 30 and the geophysical data vary over only a small range results indicate that the geophysical data improve the estimates of the hydraulic conductivity the improvement is the most significant where prior information is limited among the geophysical data gpr and seismic velocity are more useful than gpr attenuation

bayesian wavelet estimation from seismic and well data a bayesian method for wavelet estimation from seismic and well data is developed the method works both on stacked data and on prestack data in form of angle gathers the seismic forward model is based on the convolutional model where the reflectivity is calculated from the well logs possible misties between the seismic traveltimes and the time axis of the well logs errors in the log measurements and seismic noise are included in the model the estimated wavelets are given as probability density functions such that uncertainties of the wavelets are an integral part of the solution the solution is not analytically obtainable and is therefore computed by markov chain monte carlo simulation an example from sleipner field shows that the estimated wavelet has higher amplitude compared to wavelet estimation where well log errors are neglected and the uncertainty of the estimated wavelet is lower

rift to post rift evolution of a passive continental margin the ponta grossa arch se brazil low temperature thermochronology was applied at the brazilian passive continental margin in order to understand and reconstruct the post rift evolution since the break up of southwestern gondwana thermochronological data obtained from apatite fission track analysis of neoproterozoic metamorphic and paleozoic to mesozoic siliciclastic rocks as well as mesozoic dikes and alkaline intrusions from the ponta grossa arch provided ages between 66 2 1 3 and 5 9 0 8 ma these data clearly indicate a post rift reactivation during late cretaceous and paleogene times integrating the results of older thermochronological studies the reactivation of the southeastern brazilian margin could be described in three main phases related to the rift to post rift evolution of se brazil furthermore the spatial distribution of age data indicates the presence of two age groups a ne age group ne of curitiba with ages around 20 ma and a sw age group curitiba and nw with ages of around 50 ma the change of ages follows the nw se trending sao jeronimo curiuva fault zone that can be traced offshore into the southern end of the santos basin within the santos basin this lineament ends up to the salt occurrence in the south and seams to play a major role in the structural evolution of the santos basin and the rio grande rise sedimentological studies in the santos basin evidenced that the transport direction changed in miocene from wnw to wnw nnw during the oligocene and earlier the sediments were transported mainly from southeastwards to the direction of the curitiba area into the santos basin within the miocene an additional transport direction from an area north of curitiba developed

non gaussian gas hydrate grade simulation at the mallik site mackenzie delta canada abstract for the past decades gas hydrate reservoirs have beneficiated from an increasing attention in the academic and industrial worlds as a result there is a growing need to develop specific and comprehensive gas hydrate reservoir characterization methods this study explores the use of a stochastic bayesian algorithm to integrate well logs and 3d acoustic impedance in order to estimate gas hydrate grades product of saturation and total porosity over a representative volume of the mallik gas hydrate field located in the mackenzie delta northwest territories of canada first collocated log data from boreholes mallik 5l 38 and 2l 38 are used to estimate the statistical relationship between acoustic impedance and gas hydrate grades second conventional stochastic bayesian simulation is applied to generate multiple gas hydrate grade 3d fields integrating log data and lateral variability of 3d acoustic impedance these equiprobable scenarios permit to quantify the uncertainty over the estimation and identify zones where this uncertainty is greater contrary to conventional stochastic reservoir modeling workflows the proposed method allows integrating non gaussian and non linear distributions this permits to handle bimodal distributions without using complex stochastic transforms the results present gas hydrate grade values that are in accordance with well log data the relatively low standard deviation calculated at each pixel using all realizations suggests that gas hydrate grades is well explained by acoustic impedance and log data

3 d 40ar39ar geochronology in the parana continental flood basalt province new 40ar39ar analyses of borehole samples from the parana etendeka continental flood basalt province provide critical evidence of eruption rates in unexposed regions when combined with surface samples the new data clarify the duration of this major volcanic province new ages from both surface and borehole samples confirm a 10 12 million year duration of magmatism which post dates the tithonian mass extinction and provide a unique 3 dimensional picture of the spatial and temporal eruption of the lava pile chemically defined magma types are diachronous and the onset of magmatism occurred 500 1000 km inland migrating southeast towards the incipient south atlantic ocean calculated eruption rates increased from 0 03 km3 yr 1 between 138 and 135 ma through 0 13 km3 yr 1 between 135 and 133 ma to 0 21 km3 yr 1 between 133 and 131 ma supporting the notion that the rate of magmatism increased with time and proximity to the developing south atlantic after 131 ma the continental eruption rates dropped dramatically to 0 01 km3 yr 1 presumably because rifting had occurred and eruption centred in the oceanic rio grande rise with eruption rates of around 0 3 0 5 km3 yr 1 given the available constraints on the potential temperature of the plume thickness of the continental lithosphere and degrees of extension through time predicted melt production rates within the plume seriously underestimate the calculated eruption rates on the continent however the eruption rates can be reconciled if melting occurred by conductive heating of volatile enriched mantle the diachronous nature of the magma types supports the idea that melting occurred over a wide area and that the different magma types reflect different source regions rather than the temporal evolution of magmas from a single source given that 10 million years is appropriate to the timescales for conductive heating above the mantle plume it is suggested that these distinct source regions were located within the lithospheric mantle consistent with geochemical studies

field example of data fusion in site characterization application of data fusion to characterization of the fountain and lyons formations at a field site incorporates geologic knowledge geophysical log data cross hole seismic tomography hydraulic test data and observations of head to reduce uncertainty associated with subsurface interpretation these formations consist of channel and overbank deposits that have undergone variable diagenesis resulting in more hydrofacies than would have been encountered in the original unaltered deposits the disparate types of available data are integrated to yield a coherent hydrofacies classification through use of discriminant analysis and soft data techniques this data fusion improves definition of the complex hydrofacies and increases knowledge of their spatial correlation two hundred multiple indicator conditional stochastic simulations of the site are generated 100 with only hard data and 100 with both hard and soft data forward groundwater flow modeling using estimates of hydraulic conductivity from field testing yields smaller head residuals for realizations which include soft data inverse modeling is used to eliminate hydrofacies realizations that do not honor hydraulic data and to estimate hydrofacies hydraulic conductivity ranges for the hard and hard soft data ensembles inverse parameter estimation substantially decreases head residuals for both ensembles standard deviations of hydraulic conductivities estimated through inverse modeling are smaller when both hard and soft data are used to generate the simulations even though head residuals are similar within the two ensembles when these estimated hydraulic conductivities are used

post rift reactivation of the onshore margin of southeast brazil evidence from apatite u th he and fission track data abstract on the continental margin of southeast brazil there is good geological evidence for post rift tectonic reactivation in the form of onshore tertiary basins up to 800 m deep and cretaceous to paleocene alkaline intrusive bodies at the surface with the aim of constraining the mesozoic and cenozoic exhumation history of this region we present new apatite u th he ages on basement samples which one of us previously used for apatite fission track aft analysis the new he ages range from 115 5 2 2 ma to 47 0 6 4 ma whereas the aft ages range from 330 3 22 ma to 64 5 3 ma inverse thermal history modelling of all the data provides more detail on the post rift cooling history than do the aft data alone furthermore models incorporating radiation damage effects on he diffusion produce thermal histories that are more consistent with independent geological evidence than models without these effects the results imply that only a few samples record an early cooling phase around the time of opening of the south atlantic ocean the new u th he data also imply a late cretaceous phase of exhumation between 90 and 60 ma subsequently the region underwent slow cooling i e erosion rate two or three samples seem to indicate a period of rapid cooling during the neogene although this is at the limit of resolution of the methods the post rift cooling phases imply exhumation from depths between 2 and 5 km this activity we attribute to compression in the south american plate between the andean subduction zone and the mid atlantic ridge in southeast brazil compression acted on a crust that was thermally or mechanically susceptible to reactivation during the late cretaceous deformation in the study area was of regional extent whereas during the tertiary it concentrated along pre existing shear zones of the precambrian brasiliano orogeny

using bayesian simulations to predict reservoir thickness under tuning conditions mapping reservoir thickness from 3 d seismic data is a difficult task when the seismic response is dominated by tuning effects deterministic solutions may be considered when the acoustic properties of the reservoir and the encasing material are nearly constant when the acoustic properties are highly variable the dispersion of points observed in the tuning curves precludes a deterministic approach and a statistical method is preferred in this study we apply a recently developed nonlinear bayesian simulation technique to map the thickness of a reservoir associated with an intrusive rock in contrast to linear geostatistical techniques such as cokriging this method handles complex nonlinear relationships between thickness and multiple seismic attributes

hydrogeological characterization of the south oyster bacterial transport site using geophysical data a multidisciplinary research team has conducted a field scale bacterial transport study within an uncontaminated sandy pleistocene aquifer near oyster virginia the overall goal of the project was to evaluate the importance of heterogeneities in controlling the field scale transport of bacteria that are injected into the ground for remediation purposes geochemical hydrological geological and geophysical data were collected to characterize the site prior to conducting chemical and bacterial injection experiments in this paper we focus on results of a hydrogeological characterization effort using geophysical data collected across a range of spatial scales the geophysical data employed include surface ground penetrating radar radar cross hole tomography seismic cross hole tomography cone penetrometer and borehole electromagnetic flowmeter these data were used to interpret the subregional and local stratigraphy to provide high resolution hydraulic conductivity estimates and to provide information about the log conductivity spatial correlation function the information from geophysical data was used to guide and assist the field operations and to constrain the numerical bacterial transport model although more field work of this nature is necessary to validate the usefulness and cost effectiveness of including geophysical data in the characterization effort qualitative and quantitative comparisons between tomographically obtained flow and transport parameter estimates with hydraulic well bore and bromide breakthrough measurements suggest that geophysical data can provide valuable high resolution information this information traditionally only partially obtainable by performing extensive and intrusive well bore sampling may help to reduce the ambiguity associated with hydrogeological heterogeneity that is often encountered when interpreting field scale bacterial transport data

regional scale integration of multiresolution hydrological and geophysical data using a two step bayesian sequential simulation approach significant progress has been made with regard to the quantitative integration of geophysical and hydrological data at the local scale for the purpose of improving predictions of groundwater flow and solute transport however extending corresponding approaches to the regional scale still represents one of the major challenges in the domain of hydrogeophysics to address this problem we have developed a regional scale data integration methodology based on a two step bayesian sequential simulation approach our objective is to generate high resolution stochastic realizations of the regional scale hydraulic conductivity field in the common case where there exist spatially exhaustive but poorly resolved measurements of a related geophysical parameter as well as highly resolved but spatially sparse collocated measurements of this geophysical parameter and the hydraulic conductivity to integrate this multi scale multi parameter database we first link the low and high resolution geophysical data via a stochastic downscaling procedure this is followed by relating the downscaled geophysical data to the high resolution hydraulic conductivity distribution after outlining the general methodology of the approach we demonstrate its application to a realistic synthetic example where we consider as data high resolution measurements of the hydraulic and electrical conductivities at a small number of borehole locations as well as spatially exhaustive low resolution estimates of the electrical conductivity obtained from surface based electrical resistivity tomography the different stochastic realizations of the hydraulic conductivity field obtained using our procedure are validated by comparing their solute transport behaviour with that of the underlying true hydraulic conductivity field we find that even in the presence of strong subsurface heterogeneity our proposed procedure allows for the generation of faithful representations of the regional scale hydraulic conductivity structure and reliable predictions of solute transport over long regional scale distances

integration of diverse physical property models subsurface zonation and petrophysical parameter estimation based on fuzzy c means cluster analyses inversions of an individual geophysical data set can be highly nonunique and it is generally difficult to determine petrophysical parameters from geophysical data we show that both issues can be addressed by adopting a statistical multiparameter approach that requires the acquisition processing and separate inversion of two or more types of geophysical data to combine information contained in the physical property models that result from inverting the individual data sets and to estimate the spatial distribution of petrophysical parameters in regions where they are known at only a few locations we demonstrate the potential of the fuzzy c means fcm clustering technique after testing this new approach on synthetic data we apply it to limited crosshole georadar crosshole seismic gamma log and slug test data acquired within a shallow alluvial aquifer the derived multiparameter model effectively outlines the major sedimentary units observed in numerous boreholes and provides plausible estimates

consolidation and break up of the south american platform in southeastern brazil tectonothermal and denudation histories the different tectonic stages that occurred at the end of the proterozoic and during the phanerozoic have an important bearing on the tectonothermal history of the south american platform and its consolidation geochronological data u pb monazite 40ar 39ar whole rock and apatite fission track analysis from precambrian rocks of the southeastern brazilian coastline permit the modeling of a long term thermal history of the crust and constrain variable denudation rates using these data a temperature time diagram reflects a period of accelerated exhumation during the end of the brasiliano orogeny followed by long stability and reactivation of the platform during the rifting phase of the south atlantic ocean u pb zircon and monazite blocking temperature of ca 650 c data from a series of igneous bodies suggest that a tangential and transpressional tectonic regime occurred between 625 and 610 ma during the following escape tectonics between 610 and 590 ma the exhumation process indicates cooling rates of ca 12 c ma 40ar 39ar biotite ages between 540 and 510 ma ca 300 c and a corrected fission track age on apatites 100 c of 480 ma indicate an exhumation event related to block tectonics with huge vertical displacement along shear zones a long stabilization phase with low exhumation and cooling rate around 0 25 c ma was recorded from the cambro ordovician to the mesozoic at 65 ma an acceleration of the exhumation through denudation and reworking of the south american surface with cooling rate of 1 5 c ma is observed the uplift of the mantiqueira and serra do mar mountain ranges along the southeast brazilian coastline works as a climatic barrier provoking lateral erosional processes causing long term scarp retreat combined with intense but progressive denudation towards the continent a denudation of 2 5 to 4 km was calculated for such processes this lateral retreat of escarpments and flexural response can provide important insights regarding marginal isostatic uplift and the evolution of offshore sedimentary basins of southeast brazil