simulation of preferential flow in three dimensional heterogeneous conductivity fields with realistic internal architecture subsurface flow is primarily controlled by the distribution of hydrogeological properties spatially correlated random fields currently the primary means of describing heterogeneity in these properties underutilizes the existing knowledge of geological systems a new computer code the braided channel simulator bcs 3d is used to geometrically simulate the spatial heterogeneity of hydrogeological properties using representations of surface topography to estimate the three dimensional arrangement of subsurface units four methods of assigning conductivity were used to generate conductivity fields as a basis for saturated flow simulation variograms measured for each of the conductivity fields give no indication of underlying discrete structure however particle tracking simulations showed that flow occurred along paths of preferentially high hydraulic conductivity results indicate that in systems where the contrast in conductivity is sufficiently great the location and magnitude of flow is constrained by discrete internal structure additionally geometrical simulation techniques such as bcs 3d can be used to produce property fields that embody these discrete geological structures

sedimentary architecture and 3d ground penetrating radar analysis of gravelly meandering river deposits neckar valley sw germany sedimentological outcrop analysis and sub surface ground penetrating radar gpr surveys are combined to characterize the three dimensional sedimentary architecture of quaternary coarse grained fluvial deposits in the neckar valley sw germany two units characterized by different architectural styles are distinguished within the upper part of the gravel body separated by an erosional unconformity i a lower unit dominated by trough shaped depositional elements with erosional concave up bounding surfaces that are filled by cross bedded sets of mainly openwork and filled framework gravel and ii an upper unit characterized by gently inclined sheets of massive and openwork gravels with thin sandy interlayers that show lateral accretion on a lower erosional unconformity the former is interpreted as confluence scour pool elements formed in a multi channel possibly braided river system the latter as extensive point bar deposits formed by the lateral migration of a meandering river channel the lateral accretion elements are locally cut by chute channels mainly filled by gravels rich in fines and by fine grained abandoned channel fills the lateral accretion elements are associated with gravel dune deposits characterized by steeply inclined cross beds of alternating open and filled framework gravel floodplain fines with a cutbank and point bar morphology cover the gravel deposits the gpr images revealing the three dimensional geometries of the depositional elements and their stacking patterns confirm a change in sedimentary style between the two stratigraphic units the change occurred at the onset of the holocene as indicated by 14 c dating of wood fragments and is related to a re organization of the fluvial system that probably was driven by climatic changes the integration of sedimentological and gpr results highlights the heterogeneity of the fluvial deposits a factor that is important for modelling groundwater flow in valley fill aquifers

rapid deposition of sand and gravel mixtures downstream of a negative step the role of matrix infilling and particle overpassing in the process of bar front accretion an experimental flow channel was used to investigate the rapid deposition of sand and gravel mixtures downstream of a negative step hydraulic processes give rise to the quasi simultaneous accumulation of openwork gravels matrix filled contact framework and dilated framework gravels the resultant structure is analogous to a bar front in gravel bed streams flow conditions were non uniform but steady in time whereas open and closed gravel fabrics are usually interpreted as representing deposition from unsteady flows for example a varying discharge regime consideration of the percentage of sand in the deposits indicated that in terms of packing the sediments may be considered as a simple binary mixture with partial framework dilation occurring with sand percentages in excess of c 32 despite dilation for sand percentages less than 50 structural stability of the foreset gravels was maintained so that the bar front exhibited a distinct brinkpoint and a planar slip face at the angle of initial yield which made an angular contact with the base of the flume for sand percentages in excess of 80 individual gravel clasts were completely supported by sand the original structural stability was lost so that the bar front eroded by reverse currents assumed a tangential contact with the flume base below the angle of initial yield the brinkpoint was rounded and indistinct in addition to altering the bar front slope increasing the quantity of sand in the bed sediments had a major influence on the dip of gravel particles on the foresets in all experimental runs a surface sand seal with openwork gravels beneath developed upstream of the brinkpoint the mechanics of sand seal formation require further investigation however an overpassing mechanism was noted to be very important in sorting gravel particles rolling over the brinkpoint a published mathematical model describing the overpassing mechanism was found to be appropriate to the present experimental observations

terrestrial magma ocean origin of the moon a conceptual framework for the origin of the moon must explain both the chemical and the mechanical characteristics of the earth moon system to be viable the classic concept of an oblique giant impact explains the large angular momentum and the lack of a large iron rich core to the moon but in this scenario it is difficult to explain the similarity in the isotopic compositions of the earth and moon without violating the angular momentum constraint here we propose that a giant solid impactor hit the proto earth while it was covered with a magma ocean under the conventional collision conditions we perform density independent smoothed particle hydrodynamic collision simulations with an equation of state appropriate for molten silicates these calculations demonstrate that because of the large difference in shock heating between silicate melts and solids rocks a substantial fraction of the ejected moon forming material is derived from the magma ocean even in a highly oblique collision we show that this model reconciles the compositional similarities and differences between the moon and earth while satisfying the angular momentum constraint moon formation by a giant impact ejecting material from a magma ocean on earth reconciles geochemical and dynamical constraints on its formation according to numerical simulations

hydrogeologic facies models to delineate large scale spatial trends in glacial and glaciofluvial sediments recent interest in contaminant transport in ground water has led hydrogeologists to the conclusion that predicting the movement of solutes requires information on the distribution of spatial trends and heterogeneities in porous media description of spatial trends has long been of interest to sedimentologists who have produced a large body of geologic information on the subject in this paper facies models are used to construct conceptual models of hydrogeologic facies for glacialmeltwater stream sediment and till these hydrogeologic facies models which delineate large scale trends in heterogeneity are appropriate for use in designing hydrogeologic field tests and for estimating input to regional ground water flow and transport models this paper treats each facies as a homogeneous anisotropic hydrogeologic unit the models presented herein conceptualize the hydrogeologic relationships among facies and illustrate one method of converting the apparent chaos in nature into an orderly system that can be tested scientifically and modeled mathematically the principles used to create conceptual models of hydrogeologic facies for the types of sediment considered in this paper can be extended to other sedimentary environments it should be recognized however that such models do not address the small scale heterogeneity present within individual facies additional basic research is required to measure hydraulic conductivity variation within representative hydrogeologic facies and to develop statistical descriptions to represent the variations such detailed descriptions of hydraulic conductivity may be necessary to describe ground water flow at a local scale for analysis of contaminant transport

application of seismic stratigraphy and sedimentology to regional hydrogeological investigations an example from oak ridges moraine southern ontario canada hydrogeological models need to be supported by a clear understanding of the subsurface geology to provide effective assessment flow modelling or management of groundwater regimes this paper illustrates how geophysical and sedimentological data can be used to significantly improve watershed scale hydrostratigraphic models by advancing our understanding of the subsurface through regional hydrogeological investigations in the greater toronto area the example of a 3 km shallow seismic reflection survey that traverses a buried channel within bowmanville creek watershed oak ridges moraine ontario illustrates a basis for linking geophysical and sedimentological properties to regional hydrostratigraphic parameters seismic reflection methods plus seismic stratigraphy and a well constrained three dimensional geological framework have helped to i identify regional hydrostratigraphic units ii define properties and trends of these units facies iii improve depositional models that assist hydrogeological

ground penetrating radar a near face experience from washington county arkansas digital ground penetrating radar gpr is an emerging technology for detecting locating and or mapping features in the shallow subsurface it has application to geology civil engineering environmental science engineering soil science and many other fields this case history describes a high quality gpr survey performed in very close proximity to a vertical limestone rock face at a roadcut site in northwest arkansas the configuration allowed interpretation of the gpr results with the maximum of amount of geologic control the rock face itself our experience suggests that gpr has significant potential as a high resolution tool for mapping shallow structure and stratigraphy in carbonate rocks

physical state of the very early earth abstract the earliest surface environment of the earth is reconstructed in accordance with the planetary formation theory formation of an atmosphere is an inevitable consequence of earth s formation the atmosphere near the close of accretion is composed of 200 300 bars of h2 and h2o and several tens of bars of co and co2 either by the blanketing effect of the proto atmosphere or heating by large planetesimal impacts a magma ocean is formed during accretion we can distinguish three stages for the thermal evolution of the magma ocean and proto crust stage 0 is characterized by a super liquidus or completely molten regime near the surface at this stage the surface of the earth is covered by a super liquidus magma ocean no chemical differentiation is expected during this stage once the energy flux released by planet formation decreases to the 200 w m2 level the super liquidus magma ocean then disappears within a time interval of 1 m y this is the transition from stage 0 to 1 stage 1 is characterized by a partially molten magma ocean in the magma ocean consisting of 20 30 partial melt heat transport is controlled by melt solid separation a type of compositional convection rather than thermal convection chemical differentiation of the mantle mainly occurs in this stage once the energy flux drops to the 160 w m2 level more than 90 of water vapor in the proto atmosphere condense to form the proto oceans several tens of bars of co and co2 remain in the atmosphere just after formation of the oceans water oceans are occasionally evaporated by large impacts after each such event recondensation of the ocean takes several hundred years although the surface is covered by a chilled proto crust it is short lived because of extensive volcanic resurfacing activity as well as meteorite impacts resurfacing this stage ends when the energy flux drops to 0 1 1 w m2 level the duration time of stage 1 is estimated to be several hundred million years the best estimate is about 400 m y stage 2 is characterized by solid state convection this stage continues to the present day one of the most important change on the proto earth is the transition from stage 1 to 2 which occurs several hundred million years after the earth formation long lived crust is formed only after this transition

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

using two and three dimensional georadar methods to characterize glaciofluvial architecture abstract the threat of pollution in the shallow subsurface has led to an increasing need to understand how complex heterogeneities in gravel aquifers influence groundwater transport to characterize these heterogeneities we have conducted extensive two dimensional 2 d and three dimensional 3 d ground penetrating radar gpr or georadar surveys in two quarries within the rhine valley of northeastern switzerland the quarries comprised gravel and sand deposited in a proglacial braided river system that followed the maximum wurm stage glaciation after the surveys the terrace walls beneath the two study sites were photographed as they were being excavated by combining information extracted from the 2 and 3 d georadar images with the outcrop photographs it was possible to correlate georadar facies with the various glaciofluvial architectural elements the dominant elements were scour pools formed at or near the confluences of two stream channels and horizontally bedded and massive gravel sheets deposited during moderate to high water flow conditions and exposed during low flow conditions architectural elements were generally elongated parallel to the mean flow directions of the ancient river system variations in the strike of their long axes reflected lateral and vertical changes in the local flow direction time slices showed structural trends not evident on 2 d georadar images and photographs data interpretation was quicker more complete and less ambiguous when georadar facies analyses were based on a combination of georadar vertical profiles and time slices than when based on georadar vertical profiles alone

hydraulic tomography analog outcrop study combining travel time and steady shape inversion summary travel time and steady shape inversions are complementary methods for tomographic aquifer characterization in this work a combined procedure is presented that facilitates determination of spatial hydraulic conductivity and specific storage distributions in heterogeneous groundwater systems the procedure is applied to a highly heterogeneous sedimentary aquifer analog that is implemented as a two and three dimensional case study in a numerical flow model by interpreting the observations from multiple simulated short term pumping tests the main hydraulic features of the analog are successfully reconstructed the final results demonstrate the encouraging potential of the combined procedure for identifying the dominant structural elements and composition of sedimentary aquifers however limits derived from the test design of hydraulic travel time tomography in our synthetic case study prevented us from resolving small scale 10 cm in size variability of hydraulic conductivity with high discrepancies up to 5 orders of magnitude a better reconstruction of the aquifer hydraulic parameters is expected by utilizing a larger amount of measurements which involve more test and observation intervals although such a test design would be less feasible for field applications still this newly combined scheme is very attractive for an up scaled reconstruction on the sub meter scale for the present case study representative parameter values could be estimated in a computationally efficient way

the cenozoic lower rhine basin rifting sedimentation and cyclic stratigraphy in the cenozoic the lower rhine basin formed as a rift at the southeastern terminus of the dutch german central graben while the rhenish massif was uplifted the study focusses on the marginal marine and fluvial fill of the lower rhine basin a basin model is developed support for this study was given by extensive industry outcrop and well data by new stratigraphical and sedimentological observations the ingression and subsequent regression of the cenozoic north sea is analysed using the concept of base level cyclicity as the geohistory of the basin was complex a subsidence curve is constructed furthermore an attempt is made to trace the simultaneous uplift of the rhenish massif

geostatistical simulation and numerical upscaling to model ground water flow in a sandy gravel braided river aquifer analogue abstract an integrated approach combining sedimentological geostatistical and numerical analyses has been applied to model groundwater flow through a glaciofluvial braided stream gravel sand aquifer of pleistocene age exposed in a gravel pit in the eastern piedmont northern italy the aquifer under investigation consists of a stack of braided bar and minor channel fills and scour fills where different gravel sand bedforms migrated it represents an analogue of buried sediments which host some of the most important aquifer complexes and water resources of northern italy the work has been performed with three main steps 1 drawing and discretization of the geological models of two orthogonal exposures and estimate of conductivity of every facies 2 geostatistical simulation of the 3d facies heterogeneity based on semivariogram analysis of the geological models 3 application of a 3d numerical model of flow to upscale the conductivity field semivariogram analysis developed from facies indicator functions has shown that a the variability in the data set in the horizontal direction is a representation of the oriented distribution of the sedimentary facies corresponding to the average n s elongation of sediment units according to the paleoflow direction b the vertical correlation length approximates the average thickness of the bedsets bounded by fourth order erosional surfaces unit bars scour fill and small channel fill associations and may represent the thickness of an individual hydrostratigraphic unit c the conductivity and facies distributions are more variable in the vertical direction than in the horizontal one with a ratio between vertical and horizontal ranges of about 1 8 the 3d conductivity distribution within the considered deposits has been determined using a sequential indicator simulation whereas transition probability analysis has been used to confirm the correlation model obtained with semivariogram analysis and to check the result of the simulation the equivalent hydraulic conductivity tensor has been computed with finite difference modeling of groundwater flow for cubic blocks of the aquifer analogue with side length of about 13 m at this scale the medium is almost homogeneous but anisotropic with the lowest values of hydraulic conductivity in the vertical direction and the greatest values along the elongation of the sedimentary units i e almost parallel to average paleoflow

dynamics of core formation and equilibration by negative diapirism 1 we investigate dynamically the timing and metal silicate equilibration processes during core formation by negative diapirism using numerical modeling in 3 d axisymmetric geometry we follow the sinking of iron rich diapirs through a viscous silicate mantle we carried out a parameter study in which shear heating as well as several viscous rheologies are considered and systematically varied general scaling laws are derived for the diapir sinking velocity as well as for the silicate melt generation and distribution around the diapir using these scaling laws we show that metal diapirs of a radius 1 100 m sinking through a partially molten silicate mantle can chemically equilibrate within the timescales suggested by geochemical constraints therefore negative diapirism can contribute significantly to metal silicate equilibration processes during core formation

ground penetrating radar used to assess aggregate in catastrophic flood deposits northeast alberta canada coarse grained aggregate deposited by a catastrophic flood located north of fort mcmurray alberta was examined using ground penetrating radar gpr and lithostratigraphic logging techniques gpr transects were acquired from an upper scoured zone of flood deposits sedimentary structures cross beds and plane beds within the coarse sand and gravel and determinations of depth to bedrock sediment thickness of the aggregate were recognized in the gpr profiles by their varying dielectric properties fine grained conductive underlying oil sand till or glaciolacustrine sediment silt and clay attenuated the radar signal the sedimentary structures mapped from the gpr transects were confirmed in adjacent trench exposures we suggest that gpr is an efficient methodology for determining volumes of aggregate reserves thicknesses of aggregate deposits and mapping sedimentary structures of high energy fluvial sediments key words aggregate ground penetrating radar alberta spillway

distribution of strain signatures in quaternary sediments regional municipality of waterloo ontario canada a geodatabase of deformation structures with over 300 field observations and 53 attribute fields was compiled to assess the significance of soft sediment deformation in quaternary sediments in the regional municipality of waterloo as they relate to existing depositional models and regional ice sheet dynamics the regional distribution of morphologically diverse deformation structures is interpreted to reflect localized ice margin fluctuation as well as extensive gravity driven deformation associated with rapid sedimentation sediment remobilization or melting of buried or supporting ice in a glaciolacustrine setting deformation was often observed in coarse grained sediment and included attenuated and chaotic bedding shear folds dikes and reverse and normal faulting it ranged in scale and complexity from an isolated centimetre scale occurrence to entire metre scale outcrops exhibiting multiple types of deformation at various scales some of the deformation was observed in clusters of several square k

overturn and evolution of a crystallized magma ocean a numerical parameter study for mars 1 early in the history of terrestrial planets the fractional crystallization of a magma ocean can lead to a mantle stratification characterized by a progressive enrichment in heavy elements from the core mantle boundary to the surface such configuration is gravitationally unstable it causes mantle overturn and the formation of a stable chemical layering using simulations of thermo chemical convection we analyzed the consequences of overturn and subsequent layering on mantle dynamics assuming mars scaling parameters we found that the time needed to achieve chemical homogenization via convective mixing scales exponentially with the buoyancy ratio inline image which measures the relative importance of chemical to thermal buoyancy in addition when using a strongly temperature dependent viscosity the formation of a stagnant lid prevents the uppermost crystallized layers from sinking into the mantle in order to obtain their subduction an yielding mechanism must be invoked 2 in the context of mars evolution our results suggest that complete chemical mixing is unlikely to take place within time scales comparable with the planet s age magma ocean freezing could be thus responsible for the long term preservation of compositional heterogeneities as required by meteoritic evidence the lack of a surface highly enriched in incompatible elements and of a high density lid is difficult to reconcile with a stagnant lid regime operating throughout mars history an episode of surface mobilization induced by compositional overturn can resolve this difficulty provided that inline image is large enough too large buoyancy ratios however tend to suppress convective heat transport rendering it problematic to explain the late volcanic history of mars

metal silicate fractionation in the growing earth energy source for the terrestrial magma ocean based on the homogeneous accretion model of planets thermal evolution of the growing earth has been studied after the surface of the growing earth starts melting owing to the blanketing effect of the primordial atmosphere gravitational differentiation between metallic and silicate materials takes place in its upper region the differentiation would give rise to a large amount of gravitational energy release as well as layered structure inside the proto earth a part of released energy would be transported outward by convection considering the effects of gravitational fractionation and convection we have pursued numerically the evolution of the growing earth our results show that gravitational differentiation can supply energy large enough to keep the whole silicate layer in the molten state and that half of the released energy is conveyed outward by convective heat transport in the growing stage the temperature distribution in the silicate layer always lies between liquidus and solidus temperatures except in an uppermost thin zone the thermal structure obtained favors a notion of the primordial magma ocean and of chemical differentiation of mantle the structure of the growing earth which is composed of the central protocore the metallic layer and the silicate layer magma ocean would become gravitationally unstable and overturn to form a metallic core energy released by this overturn would not affect the structure of the upper magma ocean too much but undifferentiated primordial materials which come from the protocore would add to mantle materials through the overturn and this would help explain the isotopic mantle heterogeneity presently observed

chemical stratification of the mantle formed by melting in the early stage of the terrestrial evolution abstract the accretional growth of the earth necessarily involved a molten zone in the outer layer magma ocean of the growing earth resulting in downwards extraction of the molten iron alloy i e core formation the primary stratification resulted from melting in the accretional stage of the earth and consisted of an fe core a perovskite rich lower mantle and a partially molten ultrabasic upper mantle in which the melt was concentrated in two regions near the surface of the cooling gravitational differentiation and crystallization in the magma ocean should give rise further to a finer stratification the upper mantle composed of two layers the upper olivine rich layer and the lower majorite garnet rich layer and the lower mantle with a perovskite rich composition both the 400 and 670 km discontinuities of the present mantle may be the chemical boundary the geophysical constraints of the mantle i e the seismic wave velocity and density profiles favor such a stratified mantle

a systematic classification of glacial and periglacial environments facies and deposits abstract several aspects of the deposits formed in the glacial and periglacial environments are presented in order to establish a framework that can be used in various disciplines dealing with sedimentation under glacial and periglacial conditions the almost unlimited number of different deposits are grouped into 37 types that are all described briefly most of them are also illustrated by field examples mainly from poland these 37 types are grouped within 23 facies belonging to 3 continental glacial 3 continental periglacial and 3 marine periglacial subenvironments all environments subenvironments facies and deposits are defined and presented with a hierarchic code that enables unambiguous definition attention is paid to both the general characteristics of the various deposits as they have been described by previous investigators and to specific deposits that have been studied by the present authors the factors influencing peri glacial sedimentation are discussed briefly

influence of depositional setting and sedimentary fabric on mechanical layer evolution in carbonate aquifers abstract carbonate aquifers in fold thrust belt settings often have low matrix porosity and permeability and thus groundwater flow pathways depend on high porosity and permeability fracture and fault zones methods from sedimentology and structural geology are combined to understand the evolution of fracture controlled flow pathways and determine their spatial distribution through this process bed parallel pressure solution surfaces ps1 are identified as a fracture type which influences fragmentation in peritidal and basinal carbonate and upon shearing provides a major flow pathway in fold thrust belt carbonate aquifers through stratigraphic analysis and fracture mapping depositional setting is determined to play a critical role in ps1 localization and spacing where peritidal strata have closer spaced and less laterally continuous ps1 than basinal strata in the peritidal platform facies units with planar lamination have bed parallel pressure solution seams along mudstone laminae in contrast burrowed units of peritidal strata have solution seams with irregular and anastamosing geometries laminated units with closely spaced bed parallel solution seams are more fragmented than bioturbated units with anastamosing solution seams in the deeper water depositional environment pelagic settling and turbidity currents are the dominant sedimentation processes resulting in laterally continuous deposits relative to the peritidal platform environment to quantify the fracture patterns in the basinal environment mechanical layer thickness values were measured from regions of low to high bed dip the results define a trend in which mechanical layer thickness decreases as layer dip increases a conceptual model is presented that emphasizes the link between sedimentary and structural fabric for the peritidal and basinal environments where solution seams localize in mud rich intervals and the resulting pressure solution surface geometry is influenced by sedimentary geometry i e stacked fining upward cycles burrows planar laminations in both facies types laterally continuous ps1 can behave as mechanical layer boundaries as layer parallel slip increases to accommodate shear strain in the fold thrust belt more ps1 behave as mechanical layer boundaries

structural and tidal models of titan and inferences on cryovolcanism titan saturn s largest satellite is subject to solid body tides exerted by saturn on the timescale of its orbital period the tide induced internal redistribution of mass results in tidal stress variations which could play a major role for titan s geologic surface record we construct models of titan s interior that are consistent with the satellite s mean density polar moment of inertia factor obliquity and tidal potential love number k2 as derived from cassini observations of titan s low degree gravity field and rotational state in the presence of a global liquid reservoir the tidal gravity field is found to be consistent with a subsurface water ammonia ocean more than 180 km thick and overlain by an outer ice shell of less than 110 km thickness the model calculations suggest comparatively low ocean ammonia contents of less than 5 wt and ocean temperatures in excess of 255 k i e higher than previously thought thereby substantially increasing titan s potential for habitable locations the calculated diurnal tidal stresses at titan s surface amount to 20 kpa almost comparable to those expected at enceladus and europa tidal shear stresses are concentrated in the polar areas while tensile stresses predominate in the near equatorial midlatitude areas of the sub and anti saturnian hemispheres the characteristic pattern of maximum diurnal tidal stresses is largely compliant with the distribution of active regions such as cryovolcanic candidate areas the latter could be important for titan s habitability since those may provide possible pathways for liquid water ammonia outbursts on the surface and the release of methane in the satellite s atmosphere

hierarchical dynamic stratigraphy in various quaternary gravel deposits rhine glacier area sw germany implications for hydrostratigraphy the approach of dynamic stratigraphy aims to understand genetic processes that form stratigraphic units in a hierarchy of spatial and temporal scales this approach was used to investigate quaternary gravel deposits in terms of their sedimentology and in order to characterize the various sedimentary units in terms of their hydrogeological properties facies analysis within 62 gravel pits laboratory permeability measurements of field samples and geophysical surveys 3 d georadar 2 d seismic reflection led to the detection and classification of sedimentary heterogeneity according to the following six scales whereby each scale can be translated into defined hydrostratigraphic units 1 particles and pores micro scale that reflect depositional and diagenetic fluid dynamics as well as source material behaviour e g grain size roundness lithological composition this was found to be important for the hydrogeochemistry of groundwater in gravel aquifers e g higher sorption capacity of carbon rich limestone particles for organic pollutants 2 strata meso scale contain the recognition of sorting fabric texture and stratinomic features which can give an indication of transport and depositional dynamics five major lithofacies groups for example were distinguished within fluvial gravel bed deposits their variable hydraulic properties led to their subdivision into 12 hydrofacies types they form the smallest mappable hydrostratigraphic units which may result in either preferred pathways for fluid flow or flow barriers 3 depositional elements macro scale enable reconstruction of sedimentary geomorphic elements and their dynamics within a depositional system e g gravel bed braided river systems are dominated by gravel sheet gravel dunes and scour pool depositional elements hydrostratigraphically the architecture of depositional elements influences the hydraulic connectivity and local permeability structure distribution within an aquifer body five types of depositional elements in fluvial gravel bed deposits were distinguished and their geometries dimensions quantified 4 facies bodies mega scale composed of a stack of depositional elements and strata recording distinct environmental systems and their dynamics e g a coarse grained prograding delta system hydrostratigraphically facies bodies represent major compartments of an aquifer six major types of meltwater controlled facies bodies were identified in the study area 5 genetic sequences mega scale reflect the shifts of depositional environments caused by allocyclic changes e g glacial advance recorded by a coarsening upward sequence or autocyclic changes of landscape shaping events these sequences may form separate hydrostratigraphic units or aquifer storeys 6 basin fill giga scale comprising the lateral and vertical stacking of facies bodies and genetic sequences controlled by either long term glacier dynamics or short term flood events the regional distribution of permeable gravel units and for example less permeable diamicts builds the larger scale hydrostratigraphy

mapping the architecture of glaciofluvial sediments with three dimensional georadar three dimensional 3 d ground penetrating radar georadar mapping offers new opportunities for determining the geometries and facies of surficial sedimentary units to investigate the potential of this high resolution technique and at the same time study the architecture of quaternary glaciofluvial deposits georadar data have been collected on a dense grid established across a sequence of braided river gravels and sands in northeastern switzerland results of this survey are striking 3 d images that provide many more details and much more reliable information on the heterogeneities of the shallow underground than are afforded by conventional georadar profile data continuous subhorizontal and oblique reflections can be traced throughout vertical sections and horizontal slices of the georadar data block to a depth of approx 15 m clearly defined are the dominant flow direction of the ancient braided river system the boundaries between different sedimentary facies and the level of the ground water table trough fill sediments and subhorizontal channel deposits observed on 7 m high quarry walls can be followed confidently in the subsurface the orientation shape and size of the troughs and the strike and dip of the cross bedding are all well resolved

geochemical influences on h40 1 bacteriophage inactivation in glaciofluvial sands geochemical heterogeneities may cause spatial variations in virus inactivation rates resulting from interactions with minerals leading to differences in natural disinfection capacity within an aquifer column studies investigating the interaction of the bacteriophage h40 1 with natural sands sampled from the kappelen test site kappelen bern switzerland indicated that inactivation rates are higher for adsorbed bacteriophages than for those suspended in groundwater moreover breakthrough curves obtained from field based tracer tests at kappelen indicated that the adsorbed h40 1 is inactivated in situ at comparable rates statistical analyses of mineralogical data failed to demonstrate significant spatial variations in aquifer composition either across the site or with depth in contrast hydrochemical analyses of groundwater samples collected at kappelen demonstrated that iron reducing groundwater occurs below aerobic waters tracer breakthrough curves indicate that h40 1 survival is not affected by variable redox conditions investigation results suggest that spatial geochemical variability does not significantly affect h40 1s inactivation rate at kappelen

early evolution of the earth accretion atmosphere formation and thermal history atmospheric and thermal evolution of the earth growing by planetesimal impacts was modeled by taking into account the blanketing effect of an impact induced h2o atmosphere and the temperature dependence of h2o degassing when the water content of planetesimals is larger than 0 1 by weight and the accretion time of the earth is less than 5 107 years the surface of the accreting earth melts and thus a magma ocean forms and covers the surface the formation of a magma ocean will result in the initiation of core mantle separation and mantle differentiation during accretion once a magma ocean is formed the surface temperature the degree of melting in the magma ocean and the mass of the h2o atmosphere are nearly constant as the protoplanet grows further the final mass of the h2o atmosphere is about 1021 kg a value which is insensitive to variations in the model parameter values such as the accretion time and the water content of planetesimals that the final mass of the h2o atmosphere is close to the mass of the present oceans suggests an impact origin for the earth s hydrosphere on the other hand most of the h2o retained in planetesimals will be deposited in the solid earth free water within the proto earth may affect differentiation of the proto mantle in particular the mantle feo abundance and the incorporation of a light element in the outer core

transition metal partitioning between lower mantle and core materials at 27 gpa partitioning of transition metals v cr mn fe co and ni between mg perovskite magnesiowustite and metallic iron has been studied at 27 gpa and 1700 1900 c v cr and mn are strongly enriched in mg perovskite and magnesiowustite whereas fe co and ni are strongly concentrated in metallic iron under the present experimental condition using these data on partitioning we tested models of core mantle separation in the primordial earth abundances of v cr and fe in the upper mantle are consistent with a model of the upper mantle formed by olivine accumulation and or majorite fractionation in the primordial earth after the core segregation under the core mantle equilibrium however depletion of mn and overabundances of co and ni in the mantle remain unexplained by this model other processes such as vaporization of mn before or during accretion and the equilibrium partitioning of co and ni between minerals and iron in the deep lower mantle may account for the observed abundances of these elements in the mantle

geological modeling for simulation studies reservoir heterogeneity is hierarchical in nature and different levels of reservoir heterogeneity need to be quantified by the reservoir geologist for numerical simulation studies at the largest scale field scale sand body continuity and interconnectedness are the most important parameters at the scale of a reservoir or a genetic sand body areal permeability trends presence and distribution of permeability baffles vertical profiles of permeability and presence of directional permeability within a sand body are the most critical parameters at a smaller scale the influence of cross bedding on displacement processes is shown to be significant and in fact should be assessed to obtain more meaningful results from larger scale simulation models the examples given show some of the effects of the different scales of heterogeneity on fluid flow patterns these examples indicate the degree of detail that must be considered at different scales if simulations are to give meaningful results

introduction to the special issue on aquifer sedimentology problems perspectives and modern approaches abstract progress towards a better understanding of groundwater circulation and transport processes in aquifers demands a multidisciplinary approach to a host of unresolved problems although much progress has been made within recent years in interpreting the dynamic character of groundwater systems many key issues remain to be addressed in particular several areas demand attention the role of sedimentological information heterogeneity in groundwater and transport models the scaling up of observations from outcrop scale to larger scales and the integration of geological and geophysical information of different quality into the description of an aquifer structure still nowadays many of the heterogeneities cannot be recognized directly because of the limitation of measurement techniques this is probably one of the reasons for the limited application of aquifer sedimentology and geophysics in practical cases in order to consolidate expand and make a larger number of people aware of the contribution of modern aquifer sedimentology including modelling and ultra high resolution geophysical methods several lines of intervention were identified 1 a better collaboration of the different disciplines on site specific applied problems 2 development of new modelling techniques combining data of different quality 3 development of optimizing tools position and number of wells additional geophysical methods baysian techniques 4 development of a common language among sedimentologists and hydrogeologists to overcome communication problems

a numerical three dimensional conditioned unconditioned stochastic facies type model applied to a remediation well system in this study a three dimensional stochastic facies based aquifer model was developed the model can be used to numerically simulate flow and solute transport in heterogeneous groundwater aquifers the stochastic generation process can be conditioned by using available facies information in one vertical plane or two orthogonal vertical ones in this study the information was obtained from a facies interpretation of a vertical georadar profile in a natural gravel formation in switzerland in the domain outside the known profile unconditioned lenses and layers were generated at random according to statistical information on coherent sedimentary structures based on observations in adjacent gravel pits jussel et al 1994a the method was applied to a single extraction well designed to capture an initially block shaped contaminant plume a total of 80 conditioned and unconditioned synthetic aquifers was generated the flow and transport simulations were performed using a finite element flow model and a random walk transport model the results are presented as the ensemble of integral solute mass recovery curves of single realizations one would expect conditioning to reduce the bandwidth of the recovery curves representing the uncertainty but the results show that the bandwidth even increased this effect was attributed to a discrepancy in the mean volumetric fraction of the different facies types in the conditioned and the unconditioned cases moreover a simulation using a homogeneous model with constant equivalent flow and transport parameters overestimated the remediation efficiency the influence of a linear reversible equilibrium sorption on the remediation well efficiency was taken into account by an uncorrelated random field of the retardation factor based on values from the literature however the impact of the variability in hydraulic conductivity clearly exceeded the effect of the variability in the retardation factor

ground penetrating radar of northern lacustrine deltas ground penetrating radar gpr was used in several selected deltaic sedimentary environments to better understand subsurface stratigraphy and reconstruct former depositional environments the profiles provide high resolution continuous subsurface data on facies thickness and depths orientation of major sedimentary structures postdepositional failure planes and depth of peat deposits field experiments were carried out on six river deltas records from four of the deltas exhibit sedimentary facies a record from one delta shows a possible slump and records from another delta reveal the thickness and stratigraphic relationships of peat deposits the delta types are i sandy wave influenced ii sandy immature wave influenced steeper middle and lower shoreface iii sandy braided and iv gravelly fan foreset in areas of limited subsurface control stratigraphic logs from drill core cutbank exposure or geophysical logs radar profiles can provide big picture perspectives of the subsurface

the primodial terrestrial magma ocean and its implication for stratification of the mantle fractional crystallization behaviour of a magma ocean extending to lower mantle depths was deduced from estimations of melting relations for the deep mantle and the density relationships between ultrabasic liquid and mantle minerals the accretional growth of the earth necessarily involves a molten zone magma ocean in the outer layer of the growing earth the fractionation by melting during accretion results in primary stratification composed of a molten ultrabasic upper mantle magma ocean a perovskite rich lower mantle and an iron core a certain amount of al2o3 and cao was removed from the magma ocean and retained in the lower mantle due to eclogite fractionation in the early stage of accretion and the perovskite fractionation in the later stage of accretion models of the stratification of the upper mantle arising from fractional crystallization of the magma ocean and subsequent convective disturbance were deduced on the basis of estimations of melting relations for the deep mantle and the density relationships between the ultrabasic liquid and mantle minerals the stratification of the mantle which is consistent with geophysical constraints is as follows the upper mantle is composed of two layers the upper olivine rich layer and the lower garnet rich layer with a thickness around 200 km and the lower mantle with a perovskite rich composition in this model both the 400 and 650 km discontinuities are the chemical boundaries

hydrogeophysical imaging of alluvial aquifers electrostratigraphic units in the quaternary po alluvial plain italy the integration of surface geological and geomorphological information with borehole point data and geophysical e g geoelectrical images of the subsurface yields spatially consistent representations of alluvial aquifers heterogeneity at different scales from depositional systems to basin fills such an approach requires a conceptual framework to match the stratigraphic units with their evidence from ground based dc resistivity methods to effectively fill the gaps between sparse borehole data and to obtain valid representations of sedimentary heterogeneities such an approach is applied to characterize two sites of the quaternary aquifers of the central po plain italy which represent 1 the middle upper pleistocene braided to meandering river depositional systems sitting on southalpine crust and 2 their down current counterparts where they are involved by the latest uplift and deformation due to the tectonic activity of the apennine frontal thrusts electrical resistivity was considered as a proxy of the litho textural properties of hydrofacies and their major hierarchical association at depth and was interpreted in accordance with the depth decreasing resolution of ground based resistivity methods thus it was possible to identify the geophysical signature of hydrostratigraphic units through electrostratigraphic units i e sedimentary volumes identified by resistivity contrasts that spatially preserve the vertical polarity hydrostratigraphy and electrostratigraphy were then joined together through a site specific relationship between electrical resistivity and hydraulic conductivity which takes into account the prevailing process of current conduction the litho textural properties of hydrofacies and the groundwater electrical conductivity at the scales of aquifer systems and complexes this approach permitted to establish the conceptual framework to match hydrostratigraphy electrostratigraphy average hydrodynamic properties and distribution of heterogeneities

architectural element analysis within the kayenta formation lower jurassic using ground probing radar and sedimentological profiling southwestern colorado abstract a well exposed outcrop in the kayenta formation lower jurassic in southwestern colorado was examined in order to delineate the stratigraphy in the subsurface and test the usefulness of ground probing radar gpr in three dimensional architectural studies two fluvial styles are present within the kayenta formation sandbodies within the lower third of the outcrop are characterized by parallel laminations that can be followed in the cliff face for well over 300 m these sandbodies are sheet like in appearance and represent high energy flood deposits that most likely resulted from episodic floods the remainder of the outcrop is characterized by concave up channel deposits with bank attached and mid channel macroforms their presence suggests a multiple channel river system the gpr data collected on the cliff top together with sedimentological data provided a partial three dimensional picture of the paleo river system within the kayenta formation the 3 d picture consists of stacked channel bar lenses approximately 50 m in diameter the gpr technique offers a very effective means of delineating the subsurface stratigraphy its high resolution capabilities easy mobility and rapid rate of data collection make it a useful tool its shallow penetration depth and limitation to low conductivity environments are its only drawbacks

fundamental thermodynamic relations and silicate melting with implications for the constitution of d we describe fundamental thermodynamic relations helmholtz free energy as a function of volume and temperature for solids and liquids simple physically based expressions which contain all thermodynamic information about a system the solid fundamental relation consists of debye and birch murnaghan finite strain theory combined in the mie gruneisen framework the liquid fundamental relation is derived by taking the high temperature limit of the solid expression we derive the liquid equation of state which contains only four parameters from the liquid fundamental relation and show that it successfully describes measurements of liquid alkali metals water and liquid diopside over a wide range of pressure and temperature we find optimal fundamental relation parameters for diopside enstatite ilmenite and perovskite and find the solid relation to be in excellent agreement with data including heat capacities thermal expansion and mgsio3 phase equilibria we then combine the liquid and solid fundamental relations to calculate the melting curves of diopside enstatite and perovskite which are found to be in excellent agreement with experiment all predicted melting curves have dt dp slopes which decrease steadily with pressure eventually becoming negative because of liquid crystal density inversion our predicted melting temperature of perovskite in the d region 3750 k at the base of the mantle is thousands of degrees lower than previous estimates yet it is consistent with experimental data the predicted melting curve although consistent with the lack of widespread melting in the lower mantle is much lower than recently proposed geotherms in the d layer at the base of the mantle by combining our results with seismic observations of the deep mantle we propose that the d layer consists of magnesiowustite and silica in the form of stishovite or its recently discovered high pressure modification

thermal evolution of a growing mars 1 we developed a new numerical model which can simulate the thermal history and metal silicate separation of a growing mars in this model the thermal disturbance caused by planetesimal impacts is calculated for each impact event by taking into account the effects of shock heating crater excavation and isostatic rebound a metallic blob is assumed to form at the base of a magma pond if an impact site is heated above the melting temperature sinking of the metal blobs is traced assuming stokes velocity their coalescence during sinking is treated by a monte carlo approach a series of simulations is carried out assuming that mars is formed by the runaway growth from a swarm of planetesimals as was suggested by recent numerical simulations of the planetary accretion process our numerical results show that 1 no global magma ocean is formed during accretion 2 metal silicate separation takes place without global scale melting and 3 instead of a metallic core a metal rich layer is formed at the late stage of accretion

an electrostratigraphic cross section across the central po plain bearings on subsurface geology and hydrostratigraphy a 72 km long n s cross section was surveyed with direct current resistivity soundings through the quaternary clastic infill of the apennine foredeep in the po plain of lombardy northern italy the aims are 1 to test the potential of dc resistivity methods at the regional scale 2 to draw the electrostratigraphic picture of the basin fill down to the pre quaternary substratum 3 to refine and test the methodology and concepts of hierarchic electrostratigraphy at the basin scale 4 to contribute to characterize the regional hydrostratigraphy of a relevant hydrogeological basin 163 resistivity versus depth profiles with a maximum investigation depth of 450 m were obtained from vertical electrical soundings to draw the electrostratigraphic cross section the polarity of the resistivity contrast across resistivity interfaces i e resistive over conductive layers or vice versa was considered and the discontinuities were correlated according to the persisting pattern from north to south doing so the hierarchic assemblage of four major electrostratigraphic boundaries and the five intervening groups of electrostratigraphic units esus was established the resulting picture was compared to the available subsurface reconstructions from the literature using the 1 d borehole data only to check the geophysical image at some random sample sites the results show that the electrostratigraphic picture captures the geological and hydrostratigraphic complexity of the subsurface of the basin comparing well with the available direct subsurface geological and hydrostratigraphic reconstructions at the regional scale of the cross section two hierarchic orders of esus and correlative boundaries could be drawn first order groups and second order individual esus while the lowermost third order rank the electrolayer is recognized at the single ves sites only

transport modeling in heterogeneous aquifers 1 statistical description and numerical generation of gravel deposits transport of solutes in groundwater is decisively influenced by the heterogeneity of the aquifer the goal of the present work is the numerical generation of synthetic heterogeneous aquifer models based on a statistical description of heterogeneities in gravel aquifers large unweathered outcrops in several gravel pits in northeastern switzerland were investigated in this context on the basis of sedimentological observations it was possible to specify distinct sedimentary structures appearing as lenses or layers all structures have been identified in each of the investigated outcrops by inspecting and analyzing photographs of the outcrops it was possible to estimate the probability density functions pdf of the geometrical attributes of the sedimentary structures disturbed and undisturbed samples were taken from these structures to estimate the pdf of their hydraulic properties that is the hydraulic conductivity and the porosity the information obtained is used to generate distinct numerical realizations by unconditional stochastic simulation of synthetic aquifers having the same statistical properties with respect to hydraulic conductivity and porosity as the investigated deposits

thermal and chemical evolution of the terrestrial magma ocean abstract the earth is likely to have experienced a magma ocean stage during accretion thermal and chemical evolution of magma ocean is investigated based on a one dimensional two phase flow heat and mass transfer model differentiation at lower mantle pressure depends on the type of magma ocean and surrounding atmosphere if the magma ocean is formed by the blanketing effect of a solar type proto atmosphere extensive differentiation proceeds at lower mantle pressure if the magma ocean is formed by the blanketing effect of an impact induced steam atmosphere no differentiation at lower mantle pressure is likely if a very deep magma ocean is formed by a giant impact whether differentiation proceeds at lower mantle pressure or not depends on grain size viscosity of melt and or properties of a transient atmosphere on the contrary chemical differentiation likely proceeds at upper mantle pressure irrespective of magma ocean type a shallow magma ocean can remain for 100 200 my without any heating processes

sedimentary and hydraulic characterization of a heterogeneous glaciofluvial deposit application to the modeling of unsaturated flow abstract flows in the unsaturated zones of alluvial deposits are often poorly understood at the scale of structures such as stormwater infiltration basins the heterogeneous nature of the sediment inherent to this type of formation can lead to preferential flows the difficulty of quantifying them lies in obtaining hydrodynamic parameters representative of the soil structure in situ when the latter is inaccessible this study proposes a method of estimating the hydrodynamic parameters of the lithofacies composing a glaciofluvial deposit east lyon france and their integration in a 2d flow model to model flow in the unsaturated zone the approach developed comprises a sedimentological study based on the miall code carried out to determine the analogy between the lithofacies of the study site and those of two glaciofluvial reference sites currently in the process of formation chamonix france breidamerkurjokull iceland thereby permitting easy access to all the lithofacies identified on the study site the water retention and hydraulic conductivity curves were obtained on the reference sites by using beerkan type infiltration tests for finely textured materials completed by the arya and paris model and data from the literature for coarser materials thus hydrofacies corresponding to all the lithofacies were characterized these hydrofacies were used to model a drainage phase on the study site at the scale of a trench 13 50 m long 2 50 m deep the model highlighted the importance of the role played by the spatial distribution of hydrofacies on flows with a pronounced capillary barrier effect of the very coarse lithofacies and a sand lens leading to funneled flows by assuming that there is a direct link between the sedimentary lithological heterogeneity and the unsaturated hydrodynamic properties of the materials composing its different structures it was possible to perform a detailed hydrodynamic characterization of the unsaturated zone that could then be used to model flows and in particular highlight preferential flows

relating electrical conduction of alluvial sediments to textural properties and pore fluid conductivity electrical conductivity of alluvial sediments depends on litho textural properties fluid saturation and porewater conductivity therefore for hydrostratigraphic applications of direct current resistivity methods in porous sedimentary aquifers it can be useful to characterize the prevailing mechanisms of electrical conduction electrolytic or shale conduction according to the litho textural properties and to the porewater characteristics an experimental device and a measurement protocol were developed and applied to collect data on eight samples of alluvial sediments from the po plain northern italy characterized by different grain size distribution and fully saturated with porewater of variable conductivity the bulk electrical conductivities obtained with the laboratory tests were interpreted with a classical two component model which requires the identification of the intrinsic conductivity of clay particles and the effective porosity for each sample and with a three component model the latter is based on the two endmember mechanisms surface and electrolytic conduction but takes into account also the interaction between dissolved ions in the pores and the fluid grain interface the experimental data and their interpretation with the phenomenological models show that the volumetric ratio between coarse and fine grains is a simple but effective parameter to determine the electrical behaviour of clastic hydrofacies at the scale of the representative elementary volume

aquifer architecture analysis using ground penetrating radar triassic and quaternary examples s germany applying the concept of analogue studies long used in reservoir characterization outcrop analogues in two aquifer units of southern germany have been investigated upper triassic keuper alluvial sandstones stubensandstein and quaternary glaciofluvial gravels architectural element analysis of the outcrops is combined with ground penetrating radar profiles derived a few meters behind the outcrop walls such calibration is used to better understand the three dimensional sedimentary architecture many sedimentary units at the same time represent hydraulic flow units and are characterized by specific radar signatures this approach leads to promising results not only in unconsolidated aquifers but also in fully consolidated sedimentary rocks our studies will lead to a database with which more realistic predictions of the hydraulic behaviour of sedimentary aquifers systems needed for numerical hydrogeological simulations will be possible

british shore platforms and ice sheets during the past few years views about the relative ages and modes of formation of fossil rock platforms and cliffs in scotland have changed considerably1 3 i suggest further changes here and present a model of rock platform relationships which involves an interglacial set of platforms a glacial set and a late glacial feature interpretations of the glaciation of the outer hebrides have recently been completely revised this revision has major implications for the glaciation of the inner hebrides which in turn has wider implications

facies analysis in the lower greensand using ground penetrating radar this paper presents the results of a ground penetrating radar survey in the woburn sands formation lower greensand group near leighton buzzard a total of almost 4 km of survey has been acquired to investigate the internal structure of the sands the radar survey achieved a resolution on the order of tens of centimetres with penetration up to 10 m and revealed a variety of horizontal dipping and curved reflectors the reflections are interpreted using seismic interpretation methodology two scales of unconformity defined radar sequences are described first order radar sequence boundaries can be identified at the termination of primary reflectors second order radar sequence boundaries can be identified at the terminations of both primary reflectors and first order surfaces first order radar sequence boundaries are interpreted as reactivation surfaces within bedforms which are produced by changes in bedform geometry in response to a change in hydraulic regime or superimposed bedforms second order surfaces are interpreted as the product of bedform migration reflection character and geometry are described and form the basis of a ground penetrating radar facies analysis nine different radar facies have been identified these are interpreted as large sets of planar cross stratification sets of trough cross stratification cosets of cross stratification tidal bundles clay drapes diagenetic concretions and possibly bioturbated sands a reconstruction of the bedforms suggests that they were formed by very large curved crested dunes these interpretations are checked against outcrop as the sands are excavated in working sand pits

transport modeling in heterogeneous aquifers 2 three dimensional transport model and stochastic numerical tracer experiments statistical information on the coherent sedimentary structures of highly heterogeneous gravel deposits jussel et al this issue is used to investigate numerically the transport of conservative tracers the data are the basis for a numerical generation of synthetic aquifer models whose statistical distributions of the sedimentary structures and their hydraulic conductivity and porosity correspond to the findings in the investigated deposits a three dimensional finite element flow model and a corresponding random walk transport model were developed for this purpose because of the large number of finite elements needed the solution algorithm is optimized for applications on vector type computers in order to minimize the discretization errors a special interpolation technique is applied to the determination of the local velocity vector ten stochastic numerical transport experiments over a transport distance of 100 m were carried out with synthetic gravel aquifer models they allow the mean tracer velocity the effective hydraulic conductivity and the dispersion parameters to be estimated these estimates are compared with estimates of these parameters from current theories for the flow and the tracer transport in random correlated anisotropic hydraulic conductivity fields

melting temperature distribution and fractionation in the lower mantle abstract the melting curve of perovskite mgsio3 and the liquidus and solidus curves of the lower mantle were estimated from thermodynamic data and the results of experiments on phase changes and melting in silicates the initial slope of the melting curve of perovskite mgsio3 was obtained as d t m d p 77 k gpa 1 at 23 gpa the melting curve of perovskite was expressed by the kraut kennedy equation as t m k 917 1 29 6 v v 0 where tm 2900 k and p 23 gpa and by the simon equation p gpa 23 21 2 t m k 2900 1 75 1 the liquidus curve of the lower mantle was estimated as t liq 0 9 t m perovskite and this gives the liquidus temperature tliq 7000 500 k at the mantle core boundary the solidus curve of the lower mantle was also estimated by extrapolating the solidus curve of dry peridotite using the slope of the solidus curve of magnesiowustite at high pressures the solidus temperature is 5000 k at the base of the lower mantle if the temperature distribution of the mantle was 1 5 times higher than that given by the present geotherm in the early stage of the earth s history partial melting would have proceeded into the deep interior of the lower mantle estimation of the density of melts in the mgo feo sio2 system for lower mantle conditions indicates that the initial melt formed by partial fusion of the lower mantle would be denser than the residual solid because of high concentration of iron into the melt thus the melt generated in the lower mantle would tend to move downward toward the mantle core boundary this downward transportation of the melt in the lower mantle might have affected the chemistry of the lower mantle such as in the d layer and the distribution of the radioactive elements between mantle and core

can earth s rotation and tidal despinning drive plate tectonics abstract we re evaluate the possibility that earth s rotation contributes to plate tectonics on the basis of the following observations 1 plates move along a westerly polarized flow that forms an angle relative to the equator close to the revolution plane of the moon 2 plate boundaries are asymmetric being their geographic polarity the first order controlling parameter unlike recent analysis the slab dip is confirmed to be steeper along w directed subduction zones 3 the global seismicity depends on latitude and correlates with the decadal oscillations of the excess length of day lod 4 the earth s deceleration supplies energy to plate tectonics comparable to the computed budget dissipated by the deformation processes 5 the gutenberg richter law supports that the whole lithosphere is a self organized system in critical state i e a force is acting contemporaneously on all the plates and distributes the energy over the whole lithospheric shell a condition that can be satisfied by a force acting at the astronomical scale assuming an ultra low viscosity layer in the upper asthenosphere the horizontal component of the tidal oscillation and torque would be able to slowly shift the lithosphere relative to the mantle

heat partitioning in terrestrial planets during core formation by negative diapirism article i nfo we investigate the gravitational heat partitioning between silicate and metallic phases during core formation by negative diapirism in terrestrial planets we model the dynamic evolution of an iron diapir sinking through a solid silicate proto mantle our calculations include viscous heating and strong temperature and composition dependence of viscosity we show that the diapir mean temperature evolves towards an asymptotic value td which depends on the efficiency of viscous heating and heat transfer between the diapir and its surroundings and on the viscous rheology we derived a simple analytic model that captures the thermal evolution observed in our numerical experiments this model can be applied to determine the heat distribution within terrestrial planets with a large number of diapirs during their growth and early differentiation we show that the partitioning of core formation heating during negative diapirism depends strongly on the size distribution of the iron diapirs a large number of small sinking iron diapirs favors metal silicate heat exchange and leads to a relatively hot core which allows a sustainable dynamo as on earth a small number of large diapirs have the opposite effect and could correspond to a mars like planet with an early dynamo that is no longer active in all cases negative diapirism tends to leave the lowermost mantle significantly hotter than its upper part which could trigger large amounts of melting in the early deep mantle

simulation of braided channel topology and topography a computer code bcs was developed to simulate the three dimensional topographical expression of braided channel systems the model uses a random walk approach to simulate channel braiding and incorporates the hydraulic geometry of stream channels to assign width depth and velocity to each channel segment input parameters are directly related to observable geometric characteristics of a braided system such as channel system width depth and sinuosity thirty one measures of the degree or type of braiding were taken from the literature and used as calibration targets for the model all targets were matched for a portion of the ohau river new zealand this simulation technique can be used to assess quantitatively the distribution of channels with their associated hydraulic properties and visualize topographic surfaces associated with braided channel systems this information provides a foundation for probabilistic multiple realizations geometric simulation of three dimensional distribution of braided stream sediments 39 refs 4 figs 3 tabs

a re evaluation of metal diapir breakup and equilibration in terrestrial magma oceans abstract due to mechanisms such as impact heating early atmospheric thermal blanketing and radioactive heating the presence of at least one global magma ocean stage in the early histories of terrestrial planets seems unavoidable in such a context a key question to constrain the early thermo chemical evolution of the earth is how much iron diapirs provided by differentiated impactors emulsified during their sinking towards the bottom of an early magma ocean in the past years several workers have focused on this question using however various approaches and making different assumptions while most studies favor rapid breakup and equilibration of iron bodies during their sinking through the magma ocean recent work suggests that iron bodies of size comparable or greater than a few tens of kilometers may preserve most of their initial volume as they reach the bottom of a magma ocean therefore leading to metal silicate disequilibrium to clarify the discrepancies and the differences among studies i have conducted a series of numerical simulations and theoretical calculations to derive the conditions and the timing for the breakup of metal diapirs of any size sinking through a silicate magma ocean with a large range of plausible viscosity values the obtained breakup criterion is used to derive stable diapir sizes and their ability to equilibrate with the surrounding silicates i show that for plausible magma ocean viscosities diapirs with initial radii smaller than the thickness of a magma ocean rapidly break up into stable diapir sizes smaller than 0 2 m at which metal silicate equilibration is rapidly achieved

hotspots basalts and the evolution of the mantle the trace element concentration patterns of continental and ocean island basalts and of mid ocean ridge basalts are complementary the relative sizes of the source regions for these fundamentally different basalt types can be estimated from the trace element enrichment depletion patterns their combined volume occupies most of the mantle above the 670 kilometer discontinuity the source regions separated as a result of early mantle differentiation and crystal fractionation from the resulting melt the mid ocean ridge basalts source evolved from an eclogite cumulate that lost its late stage enriched fluids at various times to the shallower mantle and continental crust the mid ocean ridge basalts source is rich in garnet and clinopyroxene whereas the continental and ocean island basalt source is a garnet peridotite that has experienced secondary enrichment these relationships are consistent with the evolution of a terrestrial magma ocean

three dimensional high resolution fluvio glacial aquifer analog part 1 field study summary describing the complex structures that exist in many sedimentary aquifers is crucial for reliable groundwater flow and transport simulation however hardly any aquifer can be inspected in such detail that all decimeter to meter heterogeneity is resolved aquifer analogs serve as surrogates to construct models of equivalent heterogeneity and thus imitate those features relevant for flow or transport processes gravel pits found in excavation show excellent sections of the sedimentary sequence and thus offer direct insight into the structural and textural composition of the subsoil this paper describes an approach to also inspect the third dimension by mapping during the ongoing excavation it is possible to obtain a three dimensional representation of the subsurface within a short period of time a detailed description of a case study is presented and the findings from sedimentological hydrogeological and geophysical analyses are compared the gravel pit is located near the town of herten in southwest germany where relatively young unconsolidated fluvio glacial and fluvial sediments in the rhine basin are mined the excavated gravel body is built up by architectural elements typical for braided river deposits the study generated a high resolution data set of lithofacies hydrofacies and ground penetrating radar gpr profiles it represents the basis for a full three dimensional geostatistical reconstruction presented in the second part comunian et al 2011

high resolution aquifer analog of fluvial aeolian sediments of the guarani aquifer system the guarani aquifer system gas represents one of the biggest aquifers in the world and is the most relevant groundwater resource in south america for the first time by combining field and laboratory measurements a high resolution aquifer analog model of fluvial aeolian sediments of the gas in sao paulo state brazil is constructed three parallel sections of frontal outcrops 28 m 5 8 m and two parallel sections of lateral outcrops 7 m 5 8 m are recorded during open pit mining of sandy sediments and describe in detail the three dimensional distribution of the local lithofacies and hydrofacies variations of hydraulic conductivity k and porosity n are resolved on the centimeter scale and the most permeable units of the fluvial aeolian facies association are identified the constructed aquifer analog model shows moderate hydraulic heterogeneity and a mean k value of 1 36 10 4 m s which is greater than the reported range of k values for the entire gas in sao paulo state the results suggest that the examined sedimentary unit constitutes a relevant portion of the gas in sao paulo state in the context of groundwater extraction and pollution moreover the constructed aquifer analog is considered an ideal basis for future numerical model experiments aiming at in depth understanding of the groundwater flow and contaminant transport patterns at this gas portion or at comparable fluvial aeolian facies associations

noble gas constraints on the layered structure of the mantle several chemical models of mantle structure have been proposed1 6 based on isotopic data such as sr nd hf and pb in volcanic rocks from both oceanic and continental areas the most popular of these are two chemical models of the vertically layered mantle 1 that it is a depleted mantle from which mid oceanic ridge basalt morb is derived and 2 that it is a fertile mantle from which a mantle plume may arise1 5 however these models are almost always based on solid elements such as sr nd hf and pb isotopes and do not fully reflect the noble gas data because noble gases are liable to be lost from the solid earth when a mantle differentiation occurs on a global scale in the upper mantle the data on noble gas isotopes could give constraints on the structure of the mantle that differ from those by solid element isotopes based on a consideration 3he 4he and 40ar 36ar ratios of recent samples i argue here that the observed data suggest that mixing occurs between the source materials of a mantle plume and of morb the data seem to favour the model which assumes that the source of a typical mantle plume is deeper than that of morb

metal silicate partitioning of tungsten at high pressure and temperature implications for equilibrium core formation in earth abstract tungsten partitioning between liquid metal and liquid silicate d w from 1723 2673 k 0 5 18 gpa and over a wide range of metal and silicate compositions provides constraints on planetary core formation models we find that w partitioning is extremely sensitive to the carbon content of the metal alloy becoming about an order of magnitude more siderophile at carbon saturation activity composition corrections based on interactions between w c and fe c in metal solution shift calculated d w to more lithophile values and calculated oxygen fugacities fo2 to more oxidizing values than uncorrected data w exists as a highly charged cation in silicate solution displaying a mixture of oxidation states from 4 to 6 in experiments at fo2 of 0 5 2 log units below the iron wustite buffer at constant fo2 the average calculated valence decreases with pressure from 5 5 at 0 5 gpa to 4 at 11 18 gpa as a result of its high oxidation state w partitioning is strongly dependent on silicate melt polymerization and fo2 in contrast to some previous results we find that d w may decrease slightly in response to increasing temperature in the pressure range of our experiments pressure exerts a non monotonic effect d w increases with pressure up to 3 to 4 gpa but decreases at higher pressures previous models for the effects of pressure and temperature on w partitioning that conflict with our results appear to result from a conflation of the intensive parameters of pressure temperature and carbon content the mantle abundance of w could have been set by single stage metal silicate equilibration along the liquidus in a deep peridotite magma ocean at pressures from 20 50 gpa and at oxygen fugacities consistent with the mantle s present iron budget iw 2 to 2 5 equilibration at higher pressure is viable if the core forming metal contained a significant but not unreasonable abundance of carbon 2 wt recent continuous accretion models involving multi stage metal silicate equilibration in a deepening magma ocean with progressive oxidation of the silicate remain permissible given our new treatment of w partitioning data

survival of impact induced thermal anomalies in the martian mantle 1 a number of geophysical arguments point out the possibility that global mantle convection could have been extremely sluggish or even absent during a large part of martian history this implies that early mantle thermal anomalies produced during planetary formation might not have been quickly erased by vigorous convection one likely mechanism of early thermal inhomogeneity is large impacts at the end of heavy bombardment we suggest that tharsis province might be related to such an impact induced thermal anomaly rather than a convective plume the shape of the present day geoid for our preferred model is in good agreement with the geoid measured by mars global surveyor mgs