forearc strike slip displacement as an alternative to subduction erosion with examples from mexico and california sinistral nacimiento fault slip on the nacimiento fault of the central coast ranges of california has been variably interpreted as dextral sinistral or reverse the currently prevailing interpretation is that the nacimient

emplacement of sandstone intrusions during contractional tectonics abstract sandstone injections are created by the forceful emplacement of remobilized sand in response to increases in overpressure however the contribution provided by horizontal compressive stress to the build up in overpressure and the resulting emplacement of sand injection complexes is still to be substantiated by robust field observations an opportunity to address this issue occurs in central california where a large volume of sandstone intrusions record regionally persistent supra lithostatic pore pressure detailed fieldwork allows sandstone filled thrusts to be recognized and for the first time permits us to demonstrate that some sandstone intrusions are linked to contractional deformation affecting the western border of the great valley basin fluidized sand was extensively injected along thrust surfaces and also fills local dilatant cavities linked to thrusting the main aims of this paper are to provide detailed descriptions of the newly recognized syn tectonic injections and describe detailed cross cutting relationships with earlier sandstone injection complexes in the study area finally an evolutionary model consisting of three phases of sand injection is provided in this model sand injection is linked to contractional tectonic episodes affecting the western side of the great valley basin during the early middle cenozoic this study demonstrates that sand injections driven by fluid overpressure may inject along thrusts and folds and thereby overcome stresses associated with regional contractional deformation it is shown that different generations of sand injection can develop in the same area under the control of different stress regimes linked to the evolving mountain chain

mapping ocean observations in a dynamical framework a 2004 06 ocean atlas abstract this paper exploits a new observational atlas for the near global ocean for the best observed 3 yr period from december 2003 through november 2006 the atlas consists of mapped observations and derived quantities together they form a full representation of the ocean state and its seasonal cycle the mapped observations are primarily altimeter data satellite sst and argo profiles gcm interpolation is used to synthesize these datasets and the resulting atlas is a fairly close fit to each one of them for observed quantities especially the atlas is a practical means to evaluate free running gcm simulations and to put field experiments into a broader context the atlas derived quantities include the middepth dynamic topography as well as ocean fluxes of heat and salt freshwater the atlas is publicly available online www ecco group org this paper provides insight into two oceanographic problems that are the subject of vigorous ongoing research first regarding ocean circulation estimates

structure and evolution of the east sierran thrust system east central california 1 a belt of arc parallel northeast vergent contractional deformation the east sierran thrust system ests crops out for 150 km along the east side of the sierran continental margin arc the ests is nowhere wider than 20 km and it accommodated an estimated minimum of 9 3 km of horizontal shortening remarkably it experienced repeated episodes of broadly coaxial and coaxial planar contractional deformation beginning prior to 188 ma and continuing past 140 ma we postulate that the ests resulted primarily from episodic underthrusting of the back arc lithosphere beneath the east edge of the sierran arc facilitated by a buttressing effect of the arc as a result of this process rocks along the east flank of the batholith including the ests were episodically shortened against the arc buttress the ests experienced significant deformation during the nevadan orogeny indicating that contractional to transpressive deformation affiliated with this event affected the eastern wall rocks of the arc as well as its western wall rocks index terms 8102 tectonophysics continental contractional orogenic belts 9609 information related to geologic time mesozoic 8015 structural geology local crustal structure 9350 information related to geographic region north america keywords eastern california mesozoic structure cordilleran thrust system citation dunne g c and j d walker 2004 structure and evolution of the east sierran thrust system east central california tectonics 23 tc4012 doi 10 1029 2002tc001478

structural evolution within the luning fencemaker fold thrust belt nevada progression from back arc basin closure to intra arc shortening abstract the luning fencemaker fold thrust belt lftb of central nevada reflects major mesozoic shortening in the western us cordillera and involved contractional deformation in triassic and lower jurassic back arc basinal strata structural analyses in the santa rosa range in the northern lftb provide new insight into the evolution of this belt four phases of deformation are recognized in the santa rosa range d 1 involved tight to isoclinal folding cleavage development under low grade metamorphic conditions and reverse faulting this deformation phase reflects nw se shortening of 55 70 in the early and or middle jurassic d 2 structures are similar in orientation to d 1 but involved much less overall strain and are well developed only to the southeast d 2 appears to be related to thrusting along the eastern margin of the lftb in the middle and or late jurassic d 3 deformation reflects very minor shortening 4 deformation demonstrably occurred synchronously with emplacement of cretaceous granitoids dated at 102 ma u pb zircon based on syntectonic relations between d 4 structures and thermal metamorphism associated with intrusion and an upgrade in d 4 strain in the thermally softened metamorphic aureoles of the intrusions this last phase of deformation reflects minor regional ne sw shortening coupled with localized strain associated with pluton emplacement formation of the lftb structural province was accomplished during the d 1 and d 2 phases of deformation and most shortening occurred during the d 1 event this jurassic deformation led to structural closure of the back arc basin by top to the se tectonic transport and development of a largely ductile fold thrust belt subsequent deformation d 3 and d 4 is 50 m y younger and unrelated to development of the lftb the younger deformation reflects a combination of minor regional shortening interpreted to be related to the cretaceous sevier orogeny plus localized shortening related to emplacement of cretaceous intrusions

effects of sedimentary heterogeneity on groundwater flow in a quaternary pro glacial delta environment joining facies analysis and numerical modelling abstract we present the sedimentological survey of quaternary sediments developed in glacio fluvial to glacio lacustrine delta environments and exposed at an abandoned quarry in northern italy this outcrop is considered an analogue of sedimentary structures that could form a real aquifer we recognise the following sedimentary units i colluvial sediments with human artefacts less than 2 m thick ii gravelly sands with oversized pebbles 2 5 5 5 m thick bounded at the base by a roughly flat composite disconformity surface iii and iv gravelly sand foresets which form two bodies with different dips that are separated by an inclined almost planar erosional surface from past observations in the surrounding area and a geoelectrical survey we estimate that the minimum total thickness of the delta system is 20 m we have analysed the sedimentary characteristics of two well exposed areas which are located within units ii iii and iv and covering areas of 115 and 95 m2 using detailed sedimentological surveys along six vertical sections with the aid of a topographic survey we have reconstructed the distribution of textural units based on sedimentary facies and including information about grain size distribution sorting and packing we have constructed a sedimentary model for the two areas using orthogonal cells of 10 10 cm attributing the dominant textural unit to each cell the distribution of sedimentary textural units is used to estimate the distribution of hydraulic conductivity for the two areas of this aquifer analogue we have determined the hydraulic conductivity by assigning different values to the different textural units according to laboratory measurements of porosity and grain size distribution kozeny carman s equation and literature data we have modelled groundwater flow in the two areas approximating the balance equation with finite differences using a regular grid with 10 cm spacing and we have performed some numerical experiments first we have evaluated the equivalent conductivity tensor for the two areas secondly we have considered a coarse grid with 1 5 m spacing and at this scale we have analysed the validation of the discrete form of darcy s law usually introduced in finite difference modelling the results of the numerical experiments show the anisotropic behaviour of the medium especially for unit ii composed of sandy beds some of which lead to a preferential path for groundwater flow in the horizontal direction the deeper sedimentary units iii and iv are characterised by a lower anisotropy ratio for hydraulic conductivity because the layered structures of these units have different dips finally we show that the discrete form of darcy s law at a scale length of 1 5 m is a first order approximation only

ground penetrating radar and its use in sedimentology principles problems and progress abstract ground penetrating radar gpr also referred to as ground probing radar surface penetrating radar subsurface radar georadar or impulse radar is a noninvasive geophysical technique that detects electrical discontinuities in the shallow subsurface

spatial temporal pattern recognition of groundwater head variations for recharge zone identification abstract the delineation of groundwater recharge zones is crucial for the conservation of groundwater quality and quantity to objectively estimate groundwater recharge zones many field surveys are required that are costly in both time and money to facilitate the assessment of recharge zones with high efficiency and low expense this study proposes a fast filter approach based on empirical orthogonal function analysis and applies it in a synthetic case study and to taiwan s yilan plain in the synthetic case study we demonstrate that the proposed method can effectively identify the recharge area by considering the head variations driven by rainfall recharge for the case of yilan plain application the field investigations i e collected wellbore logs and electrical resistivity tomography ert surveys and a groundwater simulation model support the recharge zones estimated by the proposed method the study results show that within the estimated recharge zone all of the collected wellbore logs consist of coarse grains and thick and continuous high resistivity zones were shown in the ert profile images moreover the groundwater model indicates that the recharge within the estimated recharge zone is 57 6 of the total recharge despite that the area of the estimated zone is only 26 8 of the study area therefore the proposed method is shown to delineate recharge zones at low cost

mass and volume transport variability in an eddy filled ocean eddy activity in the north atlantic ocean produces fluctuations in ocean wide volume transport on the order of 20 106 cubic metres per second on multi year timescales such background noise makes it impossible to detect possible trends in the ocean circulation due to a changing climate without multi decadal observations in three spatial dimensions the possibility that the oceanic general circulation is undergoing changes as part or the cause of major climate shifts is being intensely discussed1 with some published results relying on data from moorings spanning the north atlantic ocean2 3 the circulation is however extremely noisy here i use existing estimates of the frequency and wavenumber content of geostrophic eddies in the ocean4 to show that variations in ocean wide integrated transport must appear even in the absence of a true long term trend expected fluctuations exceed 20 109 kg s 1 or 20 106 m3 s 1 and exhibit multi year timescales existing knowledge of the eddy field allows predictions of observed variability and produces lower bounds on the multi decadal timescale required to detect true trends of a large magnitude detecting and understanding the effect of climate change on the ocean circulation requires observations in three dimensions over long periods of time

oligocene and miocene paleogeography of central california and displacement along the san andreas fault recently completed sedimentologic and petrologic studies of oligocene and miocene strata in the temblor range san joaquin basin and santa cruz mountains la honda basin permit detailed reconstructions of paleogeography as well as new estimates of displacement along the san andreas fault during the oligocene and miocene the san joaquin and la honda basins were contiguous the southwestern margin of the san joaquin la honda basin was tectonically unstable and paleogeographically complex with several small deep sea fans fed by sediment derived from nearby subaerial uplifts of franciscan and granitic basement one of these deep sea fans represented by the temblor formation of the southern temblor range and the vaqueros sandstone of the central santa cruz mountains apparently has been displaced about 315 to 320 km by post early miocene post zemorrian about 23 ma right lateral slip along the san andreas fault this new estimate of displacement places an additional constraint on interpretations of san andreas slip history but ambiguities remain the time of initiation of san andreas displacement is poorly known and available data do not permit discrimination between a history of relatively continuous slip versus a history of episodic slip

shallow sub surface stratigraphy of interfluves inferred from vertical electric soundings in western ganga plains india the application of geophysical surveys such as vertical electric sounding ves for inferring shallow subsurface stratigraphy in the vast alluvial tract of india has been under utilized this paper is aimed at demonstrating the potential of resistivity methods for mapping alluvial stratigraphy in parts of the ganga plains where the availability of exposed sections is scarce and bore logs are very limited data was generated from 40 vertical electrical resistivity soundings in a stretch of w150 km in the interfluve areas between the ganga and yamuna rivers and yamuna and betwa rivers in the western ganga plains based on the available lithological data from cliff sections along the major and minor rivers draining the study area and a series of 7 drill cores along the transect the resistivity sounding data was calibrated to interpret the sub surface stratigraphy the data shows the vertical extension of the valley fills and interfluve sequences down to w100 m a high resistivity layer runs quite extensively across the interfluves and below the valley fills interpreted as a calcrete layer that may mark a major discontinuity patches of very low resistivity layers in valley fills as well as interfluves suggest the presence of saline aquifers this study demonstrates significant sub surface heterogeneity across the interfluves which is a manifestation of variable fluvial activity over a period in excess of 100 ka lateral continuity of the sandy aquifers is often broken by muddy deposits of the floodplains which form a dominant component of the interfluve sequence except for the locations close to major valleys there are no major sand bodies in the upper w100 m of the interfluves which suggests that the modern configuration of the valleys and interfluves in this region is of late quaternary antiquity a few buried sand bodies however are comparable to the dimensions of the minor rivers draining the interfluve surfaces

assimilation of rapid array observations into an ocean model experiments assimilating the rapid dataset of deep temperature and salinity profiles at 26 5 n on the western and eastern atlantic boundaries into a 1 global nemo ocean model have been performed the meridional overturning circulation moc is then assessed against the transports calculated directly from observations the best initialization found for this short period was obtained by assimilating the en3 upper ocean hydrography database prior to 2004 after which different methods of assimilating 5 day average rapid profiles at the western boundary were tested the model moc is strengthened by 2 sv giving closer agreement with the rapid array transports when the western boundary profiles are assimilated only below 900 m the approximate depth of the florida straits which are not well resolved and when the t s observations are spread meridionally from 10 to 35 n along the deep western boundary the use of boundary focused covariances has the largest impact on the assimilation results otherwise using more conventional gaussian covariances has a very local impact on the moc at 26 n with strong adverse impacts on the moc stream function at higher and lower latitudes even using boundary focused covariances only enables the moc to be strengthened for 2 years after which the increased transport of warm waters leads to a negative feedback on water formation in the subpolar gyre which then reduces the moc this negative feedback can be mitigated if en3 hydrography data continue to be assimilated along with the rapid array boundary data copyright 2012 royal meteorological society and crown in the right of canada

reassessment of the basal sauk supersequence boundary across the laurentian craton margin hinge zone southeastern california abstractin the death valley and mojave desert regions of southeastern california the contact separating the lower and middle members of the wood canyon formation wcf is currently interpreted as a regional scale unconformity coincident with the base of the sauk sequence regional mapping of this surface however reveals a nonconformable contact with underlying crystalline basement in cratonic settings and a relatively conformable contact atop a northwest thickening wedge of off craton strata that is capped by the lower member of the wcf consistent with an unconformity the progressive loss of three carbonate units within the lower member of the wcf has been attributed to incision by the base of the middle member wcf however fossil evidence and correlation based on carbon isotope compositions of each lower member wcf dolostone unit reject top down erosion to describe their loss and overall cratonward thinning results from multiple detailed measured stratigraphic sections of a conglomerate at the b

estimation of hydraulic parameters of shaly sandstone aquifers from geoelectrical measurements electrical and hydraulic conductivities of shaly sandstones are described using a capillary approach for a granular clay bearing material the clays are assumed to occur as shale shells uniformly coating the insulated sand grains the real and imaginary components of the complex electrical conductivity for this material model are written in terms of a unique solid matrix conductivity treated as a volumetric property above a critical salt concentration the conductive contribution of the shells is independent of the electrolyte salinity under this condition the equation for the bulk conductivity of the sandstone can be expressed in a simplified form however below the critical concentration the matrix conductivity is dependent on the conductivity of the water saturating the shaly component and can be expressed only by the complete equation the hydraulic conductivity for this model is expressed by a modified kozeny carman equation a new semi empirical equation relates the hydraulic conductivity for such rocks to their porosity formation resistivity factor and the electrical conductivity of its solid matrix these combined properties are described as the lithoporosity factor in this new formulation the petrophysical parameters involved are easily determined from the electrical geophysical measurements the performance of this equation is firmly tested with experimental laboratory data available in the literature its application is then extended to estimate the hydraulic parameters of a shaly sandstone aquifer in bahia brazil using either the borehole or the surface geoelectrical data examples are given to emphasize the combined use of electrical resistivity and induced polarization measurements in computing hydraulic properties

estimation of aquifer hydraulic parameters from surficial geophysical methods a case study of keritis basin in chania crete greece summary knowledge of aquifer parameters is essential for the management of groundwater resources conventionally these parameters are estimated through pumping tests carried out on water wells few boreholes may be available and carrying out pumping tests at a number of sites may be costly and time consuming the application of geophysical methods in combination with pumping tests provides a cost effective and efficient alternative to estimate aquifer parameters a geophysical method is used to obtain aquifer characteristics that are estimated through the pumping tests a correlation is established between these parameters at other sites where pumping has not been carried out in this way the entire investigation area could be covered to characterize an aquifer system this study has been carried out in the keritis basin in chania crete greece where the aquifer characteristics are required for the management of groundwater in the region

high resolution seismic and resistivity profiling of a buried quaternary subglacial valley northern alberta canada high resolution seismic and resistivity profiles were acquired to assist in the delineation of a buried quaternary subglacial valley the existence of which was first discovered by drilling one aspect of this valley is the glacial sediments that host substantial methane at shallow depths 50 m or less geophysical well logs indicate that the glacial sediments in this area generally have lower compressional wave speeds v p 10 m than adjacent undisturbed cretaceous age rocks which have v p 2200 m s and r 300 m valley the reflection profile reveals a complex series of events consistent with heterogeneous deposition one major reflection dips eastward across the valley the reflection character changes abruptly on either side of this event with dipping clinoform reflections beneath and nearly horizontal reflections above these may be related to changes in deposition processes beneath a retreating ice sheet as has been suggested by earlier workers the buried valley s basal reflections are complex and possibly reflect glaciotectonic deformation or block plucking the near surface methane gas is within but at the edge of the valley the methane gas saturated zone displays anomalously high resistivities both in the well logs and in resistivity tomography

two decades of the atlantic meridional overturning circulation anatomy variations extremes prediction and overcoming its limitations the zonally integratedmeridional volumetransport in the north atlantic atlantic meridionaloverturning circulation amoc is described in a 19 yr long ocean state estimate one consistent with a diverse global dataset apart from a weak increasing trend at high northern latitudes the amoc appears statistically stable over the last 19yr with fluctuations indistinguishable from those of a stationary gaussian stochastic process this characterization makes it possible to study using highly developed tools extreme values predictability and the statistical significance ofapparenttrends gaussianbehaviorisconsistentwith the central limittheorem for a process arising from numerous independent disturbances in this case generators include internal instabilities changes in wind and buoyancy forcing fields boundary waves the gulf stream and deep western boundary current transports the interior fraction in sverdrup balance and all similar phenomena arriving as summation effects from long distances and times as a zonal integral through the sum of the large variety of physical processes in the three dimensional ocean circulation understanding of the amoc if it is of central climate importance requires breaking it down into its unintegrated components over the entire basin

mesozoic and cenozoic extension recorded by metamorphic rocks in the funeral mountains california the funeral mountains metamorphic core complex like so many of these complexes in the north american cordillera contains early ductile structures related to mesozoic compressional tectonics that have been overprinted by structures related to later extension the core bounding detachment system formed in late miocene time and ductile extensional fabrics in its footwall have been viewed as evidence of a higher temperature stage in the same event integrated structural analysis and geochronology however indicate that ductile fabrics with a transport direction similar to the northwest direction of movement on the detachment are part of an older extensional event of late cretaceous age this event produced mylonitic fabrics a dominant foliation and well developed mineral and stretching lineations mesoscopic folds and a widespread crenulation lineation that developed during a late stage in this event also are consistent with northwest directed shear late cretaceous mylonitic fabrics are related to extensional shear zones within the core complex that have small stratigraphic offsets but may represent significant structural and metamorphic discontinuities rocks in the footwall of the shear zones experienced mid crustal depths that cannot be explained by the overburden available if the funeral mountains core rocks represent an intact block of mesozoic crust instead it appears that a significant section of mid crustal material may have been excised in late cretaceous time by the combined monarch canyon and chloride cliff shear zones as the result of gravitational instability of an overthickened crust in our interpretation this early extension was made possible by a waning of compression within the mesozoic thrust belt combined with a high regional heat flow due to the sierran arc this early extension took place 50 m y before development of the core bounding detachment system movement on which took place at low enough temperatures that deformation was predominantly brittle with some calc mylonite fabric development the youngest structures in the core are normal faults that cut the detachment and indicate a southwest transport direction orthogonal to those of both the earlier extensional events

estimated global hydrographic variability an estimate is made of the three dimensional global oceanic temperature and salinity variability omitting the seasonal cycle both as a major descriptive element of the ocean circulation and for use in the error estimates of state estimation historical hydrography recent data from the world ocean circulation experiment and argo profile data are all used root mean square vertical displacements in the upper 300 m of the ocean are generally smaller than 50 m except in energetic boundary currents and in the north atlantic subpolar gyre variability in temperature and salinity is strongly correlated below the top 100 m salinity contributions to sea surface height variability appear more significant at low latitudes than expected possibly resulting from advective and diffusive processes results are generally consistent with altimetric variability under two simple kinematic hypotheses and much of the observed structure coincides with known dynamical features a large fraction of the sea surface height variability is consistent with the hypothesis of dominance of the first baroclinic mode

unraveling histories of hydrothermal systems via u pb laser ablation dating of skarn garnet abstract skarns are one of the few direct genetic links between magma and base metals in ore deposits yet temporal relationships between skarns and their assumed causative plutons are rarely confirmed with radiometric formation ages skarns have been notoriously difficult to date directly due to a limited primary mineral assemblage generally garnet and pyroxene discrepancies in timescales of skarn formation versus pluton emplacement emphasize our tenuous understanding of temporal relationships between plutons and hydrothermal systems including the duration of hydrothermal activity and skarn mineral growth rates here we apply a new method for u pb dating grossular andradite grandite garnet via la icp ms and present the first comprehensive study to focus on u pb dates of primary skarn garnet we present u pb age constraints on garnets from multiple skarns within the jurassic and cretaceous arcs of the north american cordillera two case studies darwin and empire mountain skarns illustrate the effectiveness of the u pb grandite method by demonstrating that garnet u pb ages agree within error of the pluton and skarn hosted u pb zircon ages two additional study localities black rock and mojave skarns demonstrate the ability of grandite u pb ages to 1 directly identify a causative igneous event and 2 record timing of major tectonic events specifically extensional to trans tensional shifts in the jurassic mojave of california

uranium lead isotopic ages from the sierra nevada batholith california this study provides new information on the timing and distribution of mesozoic magmatic events in the sierra nevada batholithic complex chiefly between 36 and 37 n latitude u pb ages have been determined for 133 zircon and 7 sphene separates from 82 samples of granitoid rocks granitoid rocks in this area range in age from 217 to 80 m y triassic intrusions are restricted to the east side of the batholith jurassic plutons occur south of the triassic plutons east of the sierra nevada as isolated masses within the cretaceous batholith and in the western foothills of the range cretaceous plutons form a continuous belt along the axis of the batholith and occur as isolated masses east of the sierra nevada no granitic intrusions were emplaced for 37 m y east of the sierra nevada following the end of jurassic plutonism however following emplacement of the eastern jurassic granitoids regional extension produced a fracture system at least 350 km long into which the dominantly mafic calc alkalic independence dike swarm was intruded 148 m y ago the dike fractures probably represents a period of regional crustal extension caused by a redistribution of the regional stress pattern accompanying the nevadan orogeny intrusion of cretaceous granitic plutons began in large volume about 120 m y ago in the western sierra nevada and migrated steadily eastward for 40 m y at a rate of 2 7 mm y this slow and constant migration indicates remarkably uniform conditions of subduction with perhaps downward migration of parent magma generation or a slight flattening of the subduction zone such steady conditions could be necessary for the production of large batholithic complexes such as the sierra nevada the abrupt termination of plutonism 80 m y ago may have resulted from an increased rate of convergence of the american and eastern pacific plates and dramatic flattening of the subduction zone u pb ages of the giant forest alaskite sequence in sequoia national park are all in the range 99 3 m y indicating a relatively short period of emplacement and cooling for this nested group of plutons u pb ages of a mafic inclusion and its host granodiorite indicate that both were derived from a common source or that the mafic inclusion was totally equilibrated with the granodioritic magma comparison of isotopic ages determined by different methods such as zircon u pb sphene u pb hornblende k ar and biotite k ar suggests that zircon u pb ages generally approximate the emplacement age of a pluton however some plutons probably contain inherited or entrained old zircons and the zircons of some samples are disturbed by younger thermal and metamorphic events the ages reported here are consistent with u pb age determinations previously made on granitic rocks to the north stern et al 1981 the age distribution of granitic belts determined here is in general agreement with those established by k ar dating evernden and kistler 1970 but does not differentiate the five epochs of plutonism determined in their study

integrated geoelectrical survey for groundwater and shallow subsurface evaluation case study at siliyin spring el fayoum egypt siliyin spring is one of the many natural fresh water springs in the western desert of egypt it is located at the central part of el fayoum delta which is a potential place for urban developments and touristic activities integrated geoelectrical survey was conducted to facilitate mapping the groundwater resources and the shallow subsurface structures in the area twenty eight transient electromagnetic tem soundings three vertical electrical soundings ves and three electrical resistivity tomography ert profiles were carried out around the siliyin spring location the dense cultivation the rugged topography and the existence of infra structure in the area hindered acquiring more data the tem data were inverted jointly with the ves and ert and constrained by available geological information based on the inversion results a set of geoelectrical cross sections have been constructed the shallow sand to sandy clay layer that forms the shallow aquifer has been completely mapped underneath and around the spring area flowing of water from the siliyin spring is interconnected with the lateral lithological changes from clay to sand soil exploration of the extension of siliyin spring zone is recommended the interpretation emphasizes the importance of integrating the geoelectrical survey with the available geological information to obtain useful cheap and fast lithological and structural subsurface information

construction of the adjoint mit ocean general circulation model and application to atlantic heat transport sensitivity we first describe the principles and practical considerations behind the computer generation of the adjoint to the massachusetts institute of technology ocean general circulation model gcm using r giering s software tool tangent linear and adjoint model compiler tamc the tamc s recipe for fortran line by line generation of adjoint code is explained by interpreting an adjoint model strictly as the operator that gives the sensitivity of the output of a model to its input then the sensitivity of 1993 annual mean heat transport across 29on in the atlantic to the hydrography on january 1 1993 is calculated from a global solution of the gcm the kinematic sensitivity to initial temperature variations is isolated showing how the latter would influence heat transport if they did not affect the density and hence the flow over 1 year the heat transport at 29on is influenced kinematically from regions up to 20 o upstream in the western boundary current and up to 5 o upstream in the interior in contrast the dynamical influences of initial temperature and salinity perturbations spread from as far as the rim of the labrador sea to the 29on section along the western boundary the sensitivities calculated with the adjoint compare excellently to those from a perturbation calculation with the dynamical model perturbations in initial interior salinity influence meridional overturning and heat transport when they have propagated to the western boundary and can thus influence the integrated east west density difference our results support the notion that boundary monitoring of meridional mass and heat transports is feasible

subsurface magnetostratigraphy of pleistocene sediments from the po plain italy constraints on rates of sedimentation and rock uplift we used facies analysis to reconstruct the pleistocene sedimentary evolution of seven cores from the central northern po plain italy the cores record an overall regressive sequence consisting of shallow water marine and fl uvial deltaic deposits overlain by fully continental sediments we used magnetostratigraphy to date marine and fl uvial deltaic sediments to the early pleistocene and continental sediments to the middle late pleistocene sediment accumulation rates were 30 40 cm k y in the early pleistocene whereas relevant unconformities and or an overall reduction in sediment accumulation rates characterized the middle late pleistocene a simple airy compensation model was applied to restore actual sediments elevations to elevations at times of deposition expressed in meters above current sea level the correlation of isostatically corrected sedimentary facies to a sea level curve obtained from classic oxygen isotope studies shows that an event of rock uplift on the order of 70 120 m occurred in the middle late pleistocene literature studies of vegetational cyclicity used in conjunction with the sea level curve allowed us to link sedimentary facies to climate variability we propose that the onset of fully and persistently continental sedimentation occurred in response to the waxing of the fi rst major pleistocene glaciation in the alps currently correlated to marine isotope stage 22 at ca 0 87 ma and that the episode of uplift occurred at least in part as a consequence of erosion and crustal rebound of the alpine chain triggered by pleistocene glacialinterglacial cycles

estimated decadal changes in the north atlantic meridional overturning circulation and heat flux 1993 2004 results from a global 1 model constrained by least squares to a multiplicity of datasets over the interval 1992 2004 are used to describe apparent changes in the north atlantic ocean meridional overturning circulation and associated heat fluxes at 26 n the least squares fit is both stable and adequately close to the data to make the analysis worthwhile changes over the 12 yr are spatially and temporally complex a weak statistically significant trend is found in net north atlantic volume flux above about 1200 m which drops slightly 0 19 0 05 sv yr 1 1s v 10 6 m 3 s 1 but with a corresponding strengthening of the outflow of north atlantic deep water and inflow of abyssal waters the slight associated trend in meridional heat flux is very small and not statistically significant the month to month variability implies that single section determinations of heat and volume flux are subject to serious aliasing errors

influence of the 26 degrees n rapid mocha array and florida current cable observations on the ecco godae state estimate the incorporation of local temperature and salinity observations from the rapid climate change meridional overturning circulation and heatflux array rapid mocha as well as the cable estimates of volumetransport in the florida current fc is tested in the estimating the circulation and climateof the ocean global ocean data assimilation experiment ecco godae estimation system for their impact on the estimate of the meridional overturning circulation moc and the meridional heat transport in the atlantic an experimental setup covering the first deployment period of rapid mocha from march 2004 to march 2005 is used to test different strategies for incorporating these datasets incorporating both monthly meansofthefcdataandmonthlymeansoftherapid mochatemperatureandsalinitymeasurementsat the eastern and western boundaries of the basin as an observational constraint in a 1 yr experiment results in an adjustment to the referenceestimate whichdoes not include these datasets of approximately 1 sv 1 sv 10 6 m 3 s 21 in the moc at 268n and the adjacent latitudes approximately 6158 with a larger northward branch of the moc above 1000 m compensated by a larger flow in the southward branch of the moc between approximately 2000 and 3000 m the meridional heat transport from 268n to near 408n is approximately 0 05 pw larger than in the reference experiment

atlantic meridional heat transports in two ocean reanalyses evaluated against the rapid array 1 the atlantic meridional overturning circulation in two versions of the nemo 14 global ocean model has been compared with the rapid transport array at 26 n both model versions reproduce the mean moc strength well although the florida straits flows differ because the pathway of the gulf stream is not strongly constrained at this resolution both models however have a mean meridional heat transport of 1 07pw much lower than the 1 35pw from rapid observations in april 2004 october 2007 much of the heat transport discrepancy is due to lower transports in summer across the midocean bahamas africa section due to stronger southward geostrophic flows in the top 100 m where the water is warmest seasonal thermocline changes increase temperature differences across the basin driving stronger geostrophic shear but this effect is much weaker in the top 100 m of the rapid velocity data the effect accounts for a reduction of 1 1sv in moc and 0 1pw in heat transports the rest of the discrepancy comes from lower ekman transports from using erainterim winds instead of quikscat a smaller zonally varying eddy heat transport component estimated from repeat xbt sections in the observations and the southward throughflow in the model other differences in depth structure of the model moc and rapid observations are described but have much less impact on heat transports

geochemical constraints on the petrogenesis of the salinian arc central california implications for the origin of intermediate magmas article i nfo magmatic arcs are the primary locations where continental crust is distilled to an intermediate calc alkaline composition the root zones of continental arcs are thought to be the primary sites of magmatic differentiation yet few deeply exhumed arc sections are available for direct study the coast ridge belt of central coastal california provides an exceptional opportunity to directly observe the cumulative effects of melting mixing assimilation and homogenization related to construction of the latest cretaceous california arc we present new major and trace elementchemistry aswellasradiogenicisotopicratiosdeterminedoncoastridgebeltassemblagesrepresentative of 20 to 30 km crustal levels late cretaceous ca 93 to 81 ma gabbro diorite tonalite and granodiorite of the coast ridge belt are calc alkaline some exhibit cumulate characteristics and all show enriched isotopic composi tions sri 0 7061 to 0 7092 and end 1 4 to 5 9 rare earth element patterns in igneous and metaigneous rocks of the coast ridge belt suggest that they are sourced deeper than the 25 km paleodepth of the exposed sec tion but probably not significantly below 40 km underplating of basaltic melts derived from evolved lithospheric mantle provides the most satisfactory mechanism explaining geochemical and field evidence for partial melting and assimilation of metasedimentary framework rocks to yield gabbroic to dioritic magmas followed soon there afterby remelting to produce more silicic magmas we suggest that basaltic underplating provided a source of heat to the base of the salinian crust leading to thermal weakening and downward flow of melt fertile intra arc supracrustal assemblages thereby igniting the magmatic pulse that formed the salinian arc

detrital k feldspar pb isotopic evaluation of extraregional sediment transported through an eocene tectonic breach of southern california s cretaceous batholith abstract sedimentary provenance studies have come to be overwhelmingly based upon u pb geochronologic measurements performed with detrital zircon while alternative and potentially complementary approaches such as conglomerate clast studies and heavy mineral analysis have faded in importance measurement of pb isotopic compositions in detrital k feldspar is among the under utilized approaches available to ascertain sedimentary source regions while it has been long recognized that common pb isotope compositions recorded by k feldspar vary widely and reflect the crustal provinces from which the host basement rocks crystallized use of the approach has suffered due to a lack of appropriate statistical models and ground truth compositional data from source regions in this paper we 1 present high throughput la icpms analysis protocols needed to generate statistically meaningful detrital k feldspar pb isotope data sets 2 develop an interpretative approach based upon 208pb 206pb vs 207pb 206pb that incorporate information from the u and th decay systems into one two dimensional plot that is amenable to analysis using two dimensional kolmogorov smirnoff statistical tests 3 generate new pb isotopic data from basement rocks from southwestern north america to improve knowledge of the pb isotopic properties of potential source regions and 4 generate new pb isotopic data from lower eocene to lower miocene sedimentary rocks to evaluate changes in drainage patterns that occurred in response to deformation that affected the southern california margin through this case study we demonstrate how our new analytical and interpretative methods could be profitably applied to future geochemical and provenance studies and tectonically driven re organization of drainage patterns

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

petrology and diagenesis of the eocene butano sandstone la honda basin california the lower and middle eocene butano sandstone at least 1500 m and possibly as much as 3000 m thick was deposited as a submarine fan in a narrow restricted continental borderland setting its quartzofeldspathic composition suggests a local provenance from plutonic and metamorphic rocks of the salinian terrane it crops out in three belts of which the middle belt in the central part of the basin was buried the deepest and underwent the most significant diagenetic changes the central belt made up of middle fan deposits contains higher amounts of quartz and lower amounts of feldspar than the more proximal southern inner fan deposits and more distal northern outer fan deposits the presence of authigenic albite laumontite and pore filling kaolinite and chlorite suggests that decreases of feldspars mainly plagioclasej are related mainly to dissolution of plagioclase it is possible that at least 20 25 of the plagioclase with respect to total feldspar has been diagenetically dissolved in the butano sand

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

using ground penetrating radar and capacitively coupled resistivity to investigate 3 d fluvial architecture and grain size distribution of a gravel floodplain in northeast british columbia canada abstract this study combines ground penetrating radar gpr and capacitively coupled resistivity ccr for geophysical architecture analysis of a bar platform and channel bend on the floodplain of a poorly organized wandering gravel bed river an important objective of fluvial architectural analysis is linking fluvial style with preserved subsurface sedimentology however architectural analysis relies on opportunistic outcrops with locations or orientations that may not provide appropriate data gpr is a well established geophysical method that images reflections interpreted to represent bed geometry and bounding surfaces and is therefore ideal for imaging fluvial architecture unfortunately grain size information which is integral to architectural classification is more elusive using gpr resistivity data can be used as a proxy for sediment grain size when gpr and ccr are combined they offer an effective tool for geophysical fluvial architectural analysis five trenches provided direct observation of the subsurface sedimentology and are used to calibrate the two geophysical methods eight radar facies and one radar element are classified from the gpr survey and grouped into four categories horizontal and subhorizontal laterally continuous reflections group 1 clinoform reflections group 2 discontinuous reflections group 3 and concave up elements group 4 the 2 d resistivity data are combined in a gis to establish a 3 d resistivity model for the upper 5 m of the floodplain resistivity values correlate well with grain size and are categorized into fine grained 800 ohm m sediments in general resistivity values indicate coarse sediment in the bar platform and sand to fine grained material in the main channel and subordinate depressions resistivity profiles were extracted from the 3 d model along the gpr lines so that resistivity values could be directly compared to radar facies the shape and spread of the resistivity distributions provide dominant grain size as well as an indication of sediment sorting for individual radar facies in some cases the same radar facies is associated with markedly different grain sizes indicating different architectural elements i e horizontally bedded gravel verses horizontally bedded sand or fine grained sediment this demonstrates the utility of combining gpr and ccr insomuch as radar architecture alone is not diagnostic of fluvial architectural elements in this case study the bar platform and channel have a planform that might suggest a meandering fluvial style however gpr ccr results indicate that the dominant depositional process across the bar platform was vertical accretion of gravel sheets an architecture more consistent with a wandering gravel bed fluvial style lateral migration was limited to the outer downstream margin of the platform a location dominated by a mix of sand and gravel coarse gravel likely occupies the base of the main channel with fine grained sediment contributing to the remainder of the channel fill a four phase history is presented where the initial phase of development involves vertical accretion and migration of stacked gravel sheets during floods forming the core of the bar platform after flooding subsides and the interior bar emerges the channel becomes established and lateral migration becomes the dominant depositional process the evolution concludes with avulsion and eventual abandonment of the channel

structural development during flysch basin collapse the fencemaker allochthon east range nevada abstract during mesozoic deformation in north central nevada a thick succession of triassic siliciclastic and hemipelagic carbonate strata that were deposited in a deep water basin shortened against and overrode penecontemporaneous shallow water carbonates and interbedded siliciclastics at the eastern margin of the basin initial rheologic contrasts developed between lithologic units during shallow pretectonic burial localized displacements within fine grained poorly cemented units and along lithologic boundaries changes in theology during low pressure and low temperature deformation led to more brittle conditions possibly due to fluid expulsion and subsequent displacements truncated bedding structures in triassic strata suggest that the w facing slope of the shelf to basin transition localized thrusting collapse of the basinal strata against strata of the basin margin and formation of a thrust at the shelf to basin transition demonstrate the ability of stratigraphic declivities and associated rheologic contrasts to buttress deformation and localize thrusting

timely detection of changes in the meridional overturning circulation at 26 n in the atlantic it is investigated how changes in the north atlantic meridional overturning circulation moc might be reliably detected within a few decades using the observations provided by the rapid moc 26 n array previously detectability of moc changes had been investigated with a univariate moc time series exhibiting strong internal variability which would prohibit the detection of moc changes within a few decades here a modification of k hasselmann s fingerprint technique is used simulated observations are projected onto a time independent spatial pattern of natural variability to derive a time dependent detection variable the fixed spatial pattern of natural variability is derived by regressing the zonal density gradient along 26 n against the strength of the moc at 26 n within the coupled echam5 max planck institute ocean model s mpi om control climate simulation this pattern is confirmed against the observed anomalies found between the 1957 and the 2004 hydrographic occupations of the section onto this fixed spatial pattern of natural variability both the existing hydrographic observations and simulated observations mimicking the rapid moc 26 n array in three realizations of the intergovernmental panel on climate change ipcc scenario a1b are projected for a random observation error of 0 01 kg m 3 and only using zonal density gradients between 1700 and 3100 m depth statistically significant detection occurs with 95 reliability after about 30 yr in the model and climate change scenario analyzed here compared to using a single moc time series as the detection variable continuous observations of zonal density gradients reduce the detection time by 50 for the five hydrographic occupations of the 26 n transect none of the analyzed depth ranges shows a significant trend between 1957 and 2004 implying that there was no moc trend over the past 50 yr

a reappraisal of the early slip history of the san andreas fault central california usa the modern san andreas fault system california united states is widely considered to have formed in response to the initiation of pacific north american plate interaction ca 27 ma although there is general consensus on the magnitude and timing of neogene displacement along the san andreas system its paleogene history remains unresolved in particular 100 km of right lateral offset between mid cretaceous plutonic rocks of the northern salinian block and the western edge of sierra nevada basement remains unaccounted for after restoration of neogene displacement along strike slip faults of the san andreas system our detrital zircon data invalidate a key paleogene piercing point by demonstrating that displaced portions of the hypothesized middle eocene butano point of rocks submarine fan were never contiguous across the san andreas fault we instead show that the eocene provenance characteristics exhibited by northern salinian strata closely match those of the southern sierra nevada and northwestern mojave desert this implies that the northern salinian block was located at least 75 50 km farther south in eocene time than previously recognized our data require 1 pre 23 ma dextral slip along the san andreas fault in central california and or 2 slip along a predecessor fault that formed prior to pacific north american plate interaction this previously undocumented slip may indicate that significant pacific north american plate interaction propagated from the plate margin into the continental interior much earlier than conventionally believed alternatively late paleogene slip could predate the development of the modern plate boundary and represent inboard dextral strike slip displacement along the eastern margin of the salinian block similar to the deformation that occurs today along the strike slip sumatra fault system

monitoring the atlantic meridional overturning circulation the rapid climate change programme rapid has established a prototype system to continuously observe the strength and structure of the atlantic meridional overturning circulation moc at 26 5 n here we provide a detailed description of the rapid moc monitoring array and how it has evolved during the first four deployment years as well as an overview of the main findings so far the rapid moc monitoring array measures 1 gulf stream transport through florida strait by cable and repeat direct velocity measurements 2 ekman transports by satellite scatterometer measurements 3 deep western boundary currents by direct velocity measurements 4 the basin wide interior baroclinic circulation from moorings measuring vertical profiles of density at the boundaries and on either side of the mid atlantic ridge and 5 barotropic fluctuations using bottom pressure recorders the array became operational in late march 2004 and is expected to continue until at least 2014 the first 4 years of observations april 2004 april 2008 have provided an unprecedented insight into the moc structure and variability we show that the zonally integrated meridional flow tends to conserve mass with the fluctuations of the different transport components largely compensating at periods longer than 10 days we take this as experimental confirmation of the monitoring strategy which was initially tested in numerical models the moc at 26 5 n is characterised by a large variability even on timescales as short as weeks to months the mean maximum moc transport for the first 4 years of observations is 18 7 sv with a standard deviation of 4 8 sv the mechanisms causing the moc variability are not yet fully understood part of the observed moc variability consists of a seasonal cycle which can be linked to the seasonal variability of the wind stress curl close to the african coast close to the western boundary fluctuations in the gulf stream and in the north atlantic deep water nadw coincide with bottom pressure variations at the western margin thus suggesting a barotropic compensation ongoing and future research will put these local transport variations into a wider spatial and climatic context

continental depositional systems of the quaternary of the po plain northern italy abstract the po plain is a molasse foredeep bounded by two mountain chains apennines and alps apenninic thrusting is still active whereas the alpine one ended by early pliocene times the continental deposits form a veneer at the surface and form the topset of a prograding complex the po river divides the plain into two sectors with different sedimentary facies and body geometries to the south the alluvial fan and plain deposits are small embedded in clays and show elongate shapes to the north sedimentary bodies are laterally extensive tabular and with minor amounts of fine grained sediments this difference could be due to a different climatic conditions during quaternary ice ages on the two sides of the basin b different structural settings in the two sectors of the basin that produce a higher subsidence rate to the south c different lithologies in the source areas i e alps and apennines

long lived deformation history recorded along the precambrian thelon and judge sissons faults northeast thelon basin nunavut the ene striking thelon and judge sissons faults of south central nunavut are well preserved and record long lived dextral transcurrent movement with complex reactivation and fluid flow histories

slowing of the atlantic meridional overturning circulation at 25 n the atlantic meridional overturning circulation carries warm upper waters into far northern latitudes and returns cold deep waters southward across the equator its heat transport makes a substantial contribution to the moderate climate of maritime and continental europe and any slowdown in the overturning circulation would have profound implications for climate change a transatlantic section along latitude 25 n has been used as a baseline for estimating the overturning circulation and associated heat transport here we analyse a new 25 n transatlantic section and compare it with four previous sections taken over the past five decades the comparison suggests that the atlantic meridional overturning circulation has slowed by about 30 per cent between 1957 and 2004 whereas the northward transport in the gulf stream across 25 n has remained nearly constant the slowing is evident both in a 50 per cent larger southward moving mid ocean recirculation of thermocline waters and also in a 50 per cent decrease in the southward transport of lower north atlantic deep water between 3 000 and 5 000 m in depth in 2004 more of the northward gulf stream flow was recirculating back southward in the thermocline within the subtropical gyre and less was returning southward at depth

electrical properties of artificial clay bearing sandstone rocks which contain clay minerals often display electrical properties which cannot be predicted by bulk electrical properties of the constituents cohen 1981 interactions between clay minerals and groundwater can produce polarization phenomena decreases in resistivity and supposed nonlinear behavior

regional tectonics of the coso geothermal area along the intracontinental plate boundary in central eastern california three dimensional vp and vp vs models spatial temporal seismicity patterns and seismogenic deformation we synthesize the tectonics of the southern walker lane belt and coso range in central eastern california using regional earthquake data first we invert for three dimensional models of the v p and v p v s structure of the upper and middle crust using these models we also determine three dimensional vs and poisson s ratio models the changes in seismic velocities across the region are small except for low velocities in sedimentary basins and a 2 km positive elevation of the basement velocities v p 6 km s beneath the southern sierra nevada localized low v p and low v s zones beneath the central coso range image a geothermal reservoir at 0 to 3 km depth as well as distinct low velocity anomalies in the depth range of 8 to 12 km because the v p v s has average crustal values within this broader zone we interpret the anomaly to indicate a zone of few percent geothermal brines extending from 8 to 12 km depth in addition an embedded highly localized poorly resolved zone possibly as small as 1 km 3 of slightly above average v p v s and higher poisson s ratio is a tentative suggestion of a small volume percent of magma present at depth of 10 km second we relocated the seismicity in the region using absolute traveltimes and differential traveltimes determined from waveform cross correlation the relocated seismicity forms several spatially clustered lineaments along the southeast side of the sierra nevada and in the indian wells valley and vicinity of the coso geothermal field which coincide with mapped late quaternary faults in the region the base of seismicity shallows from a regional depth of about 11 to 5 km beneath the central coso range which we interpret as evidence for shallowing of the brittle ductile transition zone beneath the geothermal field in addition to abundant background seismicity two large earthquake swarms located 5 to 8 km to the west of coso occurred in april to may 1992 and may to june 2001 two dual main shock aftershock sequences also occurred as follows the 1994 sequence near ridgecrest and the later coso earthquake sequence from late 1996 to early 1998 with the pairs of main shocks spaced 47 days and 16 months apart respectively kinematic analysis of the focal mechanisms indicates that the crustal stress loading process varies across the region the low vp anomaly abundant seismicity and crustal thinning provide quantitative evidence for the coso region being an extensional releasing step over between two northwest striking dextral faults the little lake and airport lake fault zones to the south and the owens valley fault to the north

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

overview tectonic implications of cenozoic volcanism in coastal california cenozoic volcanic rocks of coastal california were erupted west of the magmatic arc trend related to subduction along the continental margin two assemblages representing discrete pulses of mid tertiary oligocene miocene and mid miocene volcanism occupied relatively compact tracts as restored palinspastically prior to disruption and dispersal by tectonic displacements within the neogene san andreas transform system a third assemblage records migratory post mid miocene volcanism at centers located progressively farther north the distribution and petrologic character of all three assemblages reflect slab window magmatism triggered by decompression melting of upwelling mantle paleogeographic reconstructions based on analysis of magnetic anomaly patterns offshore and restoration of on land features prior to san andreas transform slip and associated transrotational deformation indicate the paleotectonic positions of the cenozoic volcanic fields before structural disruption the pulses of mid tertiary and mid miocene volcanism were related to transient episodes of mantle upwelling generated successively by rise trench encounters associated with subduction of the vancouver farallon and monterey arguello plates respectively along the continental margin off southern california migratory post mid miocene volcanism in central california accompanied the incremental expansion of a growing slab window as the mendocino triple junction migrated northward along the continental margin mid miocene columbia river basalt volcanism in the pacific northwest was coeval with the mid miocene pulse of coastal volcanism and may have reflected tectonism induced by the final demise of offshore microplates to allow initial full integration of the san andreas transform as a coherent plate boundary columbia river volcanism may have stemmed from mantle perturbation caused by torsional deformation of the continental block in response to shear imposed by the pacific plate

late quaternary sequence stratigraphy as a tool for groundwater exploration lessons from the po river basin northern italy sequence stratigraphy typically used for hydrocarbon exploration in ancient strata can be applied to late quaternary successions to decipher complex spatial relations among their aquifers late pleistocene holocene strata of the po basin were investigated using a sequence stratigraphic approach to produce a high resolution model for guiding groundwater exploitation because facies tend to be diachronous across depositional basins facies analysis was done within the conformable intervals of strata revealed by sequence stratigraphy to accurately interpret and map coeval lateral facies relations volumetric assessments sand distribution mapping hydraulic characterization of facies and spatial variations of hydraulic parameters revealed two aquifer systems the lowstand systems tract lst and the highstand systems tract hst vertically separated by an aquitard the transgressive systems tract tst the lst aquifer consists of amalgamated fluvial sands average transmissivity 3 5 e 3 m2 s 37 7 e 3 ft2 s with considerable width 25 km 16 mi preferentially elongated downstream the widespread tst aquitard is dominated volumetrically 57 by low permeability estuarine deposits the hst aquifer average transmissivity 5 4 e 5 m2 s 58 1 e 5 ft2 s is 5 10 km 3 6 mi wide elongated parallel to the modern shoreline sequence stratigraphic analysis at the parasequence scale revealed an almost unprecedented level of detailed insight into aquifer or aquiclude dimensions and the complex distribution of hydraulic parameters in the subsurface showing that similar facies have different permeabilities depending on systems tract in contrast lithostratigraphic mapping obscures subsurface connectivity and directional trends and has minimal predictive power away from control these insights should be useful for guiding correlation and mapping of the deep subsurface and for hydrocarbon reservoir modelers

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

the terramare and the surrounding hydraulic structures a geophysical survey of the santa rosa site at poviglio bronze age northern italy abstract the terramara santa rosa is a middle and late bronze age archaeological site located in the po alluvial plain northern italy it is constituted of two moated villages delimited by earthen ramparts the peripheral structures of the site are sealed by fine textured flood plain deposits and they have not been fully explored through excavation due to their large extent because the shape of the villages and their relation to moats and the fluvial network are of paramount importance to understanding the landscape management and the use of water resources in the terramare civilisation a geophysical survey was planned to extend the results of the existing archaeological excavations to the site scale a frequency domain electro magnetic sounding fdem and electrical resistivity imaging eri covered an area of approximately 26 ha eri was conducted for a total length 9000 m despite the predominance of electrically conductive fine textured sediments electrical resistivity anomalies were observed and they were attributed to subtle lithological differences in the sedimentary context of the alluvial plain the geophysical interpretation after the calibration with the excavation data revealed the structures of the terramara and of the surrounding hydraulic network which are not visible at the surface due to flood plain deposits the santa rosa site was founded in a favourable geomorphological position on the top of a crevasse splay lobe of the adjoining po palaeo channel rising above the surrounding alluvial plain the terramara and their surroundings were delineated through an artificial modification of this pre existing crevasse splay lobe and a well targeted urban design with the objective of diverting water most likely from a palaeo channel of the po river through the digging of peripheral moats used to collect water around the site and to distribute it to the surrounding fields for irrigation the water management documented by this study in the terramara santa rosa can be considered as paradigmatic for the whole terramare civilisation which is therefore responsible of the introduction of the irrigated agriculture into western europe for the first time

hydrographic evolution in relation to neotectonics aided by data processing and assessment some examples from the northern apennines italy abstract geomorphological morphotectonic stratigraphical structural and geological data were collected in the area between the rivers scrivia and nure the po plain and the headwaters of the rivers trebbia aveto and borbera northern italy the data were used to implement databases and to computerise geo related thematic maps which are easily comparable and readily updated reaches of the borbera and lambro meridionale rivers that show anomalous diversions were investigated in detail several thematic maps geolithological geomorphological etc were constructed and overlain on the digital terrain model the results of the processing hillshade slope aspect drainage etc are important elements for identifying and reconstructing the main tectonic phases that have constrained the hydrography of the area

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

electrical resistivity ground imaging ergi a new tool for mapping the lithology and geometry of channel belts and valley fills efforts to map the lithology and geometry of sand and gravel channel belts and valley fills are limited by an inability to easily obtain information about the shallow subsurface until recently boreholes were the only method available to obtain this information however borehole programmes are costly time consuming and always leave in doubt the stratigraphic connection between and beyond the boreholes although standard shallow geophysical techniques such as ground penetrating radar gpr and shallow seismic can rapidly obtain subsurface data with high horizontal resolution they only function well under select conditions electrical resistivity ground imaging ergi is a recently developed shallow geophysical technique that rapidly produces highresolution profiles of the shallow subsurface under most field conditions ergi uses measurements of the ground s resistance to an electrical current to develop a two dimensional model of the shallow subsurface 200 m called an ergi profile ergi measurements work equally well in resistive sediments

offset along the san andreas fault of eocene strata from the san juan bautista area and western san emigdio mountains california analyses of eocene strata that rest on gabbroic basement rocks in the western san emigdio mountains and northernmost gabilan range indicate that the 2 sequences have been offset right laterally 305 320 km along the san andreas fault in both areas basal shallow marine conglomerate of penutian age grades upward into shale of ulatisian and narizian age that was deposited at bathyal water depths in a basin with access to open ocean additional similarities in the upper eocene and oligocene stratigraphic units suggest original contiguity of the depositional basins the inferred offset indicates that the salinian block was attached to western california by at least early eocene time the longer distances of northward transport of the salinian block that are suggested by preliminary paleomagnetic data from upper mesozoic granitic rocks and upper cretaceous and paleocene strata must have occurred during paleocene or earlier time

correlation of vertical electrical sounding and electrical borehole log data for groundwater exploration we have correlated the longitudinal unit conductance cl obtained from interpreted vertical electrical sounding data with the formation resistivity rt and the formation resistivity factor f obtained by carrying out electrical borehole logging interpreted geophysical data of eleven soundings and two electrical borehole log records are used for the analysis the geophysical data used were acquired in a sedimentary basin the study area is called lower maner basin located in the province of andhra pradesh india vertical electrical soundings were carried out using a schlumberger configuration with half current electrode separation varying from 600 1000 m for logging the two boreholes a widco logger model 3200 pls was used true formation resistivity rt was calculated from a resistivity log formation resistivity factor f was alsocalculatedatvariousdepthsusingrt values anappreciableinverserelationexists between the correlated parameters the borehole resistivity rt and the formation resistivity factor f decrease with the increase in the longitudinal unit conductance cl we have shown the use of such a relation in computing borehole resistivity rt and formation resistivity factor f at sites that posses only vertical electrical sounding data with a fair degree of accuracy validation of the correlation is satisfactory scope for updating the correlation is discussed significance and applications of the relation for exploration of groundwater namely to update the vertical electrical sounding data interpretation by translating the vertical electrical sounding data into electrical borehole log parameters to facilitate correlations studies and to estimate the porosity permeability k and water saturation sw of water bearing zones are discussed

a revised kinematic model for the relative motion between pacific oceanic plates and north america since the late cretaceous 1 the convergence between the pacific farallon and kula oceanic plates and the north american plate has provided a driving force for tectonic processes that have shaped the western margin of north america yet reconstructions of plate motion in the pacific basin have traditionally relied on the assumption of fixed hot spots in the last decade substantial cretaceous to paleogene motion between the pacific and atlantic hot spots has been recognized providing motivation to reevaluate the history of relative motion between pacific oceanic plates and north america by means of plate circuit reconstructions this paper presents new kinematic models based on two alternative plate circuits linking the pacific plate to north america since late cretaceous time when compared to models relying on fixity of pacific and indo atlantic hot spots our reconstructions suggest that the pacific kula and pacific farallon ridges were 600 1000 km closer to the western margin of north america and hence that the farallon and kula plates were smaller in late cretaceous to middle eocene time these findings cast significant doubt on the viability of a configuration of the farallon kula ridge that juxtaposes the kula plate with the southern part of the paleo north american margin during this time interval the results of our new reconstructions also suggest more oblique convergence between the farallon or kula plate and north america from the late cretaceous to the middle eocene related to the combination of dominantly northwest motion of the pacific plate and steady southwest motion of north america this provides an efficient mechanism for the coast parallel translation of some accreted terranes of north america it may also explain the structure of geological units in western north america such as the central belt of the franciscan complex which show a dominant coast parallel fabric formed during an interval coeval with the episode of oblique convergence

electrical resistivity hydraulic conductivity relationships in glacial outwash aquifers empirical field relationships between the apparent formation factors from surface resistivity soundings and hydraulic conductivity from pumping tests in fresh water granular aquifers usually show positive correlations these relationships can be adequately explained by theory if consideration is taken of in situ field conditions a sound theoretical basis for relating apparent formation factor to pertinent hydrogeophysical parameters in homogeneous isotropic sand is a three phase parallel resistor model which explicity includes parameters of porewater resistivity grain size and shape porosity tortuosity and intergranular surface conductance the veracity of the theoretical model is supported by data from laboratory tests the model demonstrates that intergranular surface conductance is an important factor at small grain sizes and high porewater resistivities operating to lower the apparent formation factor the model further shows that direct relationships between hydraulic conductivity and formation factor are weak in the normal range of porewater resistivity being strongly dependent on porosity when systematic variation of in situ porosity and aquifer layering effects are considered a simulated field curve relating the apparent formation factor to hydraulic conductivity is shown to compare favorably with the comparable curve from field data for thirteen pumping test sites in southern rhode island both theoretical and empirical results demonstrate a useful positive correlation between aquifer apparent formation factor and hydraulic conductivity quantitative interpretation however is imprecise because of nonuniqueness of interpretation and inherent variation in important aquifer parameters especially porosity

sedimentologic and isotopic constraints on the paleogene paleogeography and paleotopography of the southern sierra nevada california detrital zircon u pb provenance and stable isotopic studies of three paleogene southern sierra nevada california basins place new constraints on the paleoelevation history of the region age spectra from the paleocene witnet formation within the southernmost sierra nevada link these sediments to source terranes that were at or near sea level in the early cenozoic while age spectra from the paleocene goler formation east of the sierra nevada demonstrate isolation of southern sierra nevada basins from the continental interior and tapping of jurassic and triassic arc flank sources during the paleocene west of the sierra nevada strata of the eocene tejon formation are dominated by cretaceous zircons sourced from the sierran batholith goler formation carbonate 18 o suggests paleocene paleoelevations of 1 2 km for the central and southern sierra nevada taken together these data indicate a paleogene southern sierra nevada with modest elevations locally dissected to sea level by rift basins formed by late cretaceous lithospheric collapse these results place new limits on the amount of regional middle to late cenozoic elevation gain that may have resulted from the loss of dense mantle lithosphere from below the central and southern sierra nevada and point to possible north south variations in the topographic evolution of the sierra nevada

temporal variability of the atlantic meridional overturning circulation at 26 5 n the vigor of atlantic meridional overturning circulation moc is thought to be vulnerable to global warming but its short term temporal variability is unknown so changes inferred from sparse observations on the decadal time scale of recent climate change are uncertain we combine continuous measurements of the moc beginning in 2004 using the purposefully designed transatlantic rapid climate change array of moored instruments deployed along 26 5 n with time series of gulf stream transport and surface layer ekman transport to quantify its intra annual variability the year long average overturning is 18 7 5 6 sverdrups sv range 4 0 to 34 9 sv where 1 sv a flow of ocean water of 106 cubic meters per second interannual changes in the overturning can be monitored with a resolution of 1 5 sv

variability of the meridional overturning in the north atlantic from the 50 year gecco state estimation abstract the german partner of the consortium for estimating the circulation and climate of the ocean gecco provided a dynamically consistent estimate of the time varying ocean circulation over the 50 yr period 1952 2001 the gecco synthesis combines most of the data available during the entire estimation period with the ecco massachusetts institute of technology mit ocean circulation model using its adjoint this gecco estimate is analyzed here for the period 1962 2001 with respect to decadal and longer term changes of the meridional overturning circulation moc of the north atlantic a special focus is on the maximum moc values at 25 n over this period the dynamically self consistent synthesis stays within the error bars of h l bryden et al but reveals a general increase of the moc strength the variability on decadal and longer time scales is decomposed into contributions from different processes changes in the model s moc strength are strongly influenced by the southward communication of d

relating lithofacies to hydrofacies outcrop based hydrogeological characterisation of quaternary gravel deposits abstract a considerable part of today s drinking water supplies in europe and north america rely on clean groundwater from gravelly valley aquifers of quaternary age the sedimentary architecture the distribution of lithofacies and of architectural elements in such heterogeneous deposits are of fundamental importance for the analysis of groundwater flow and contaminant transport as the aquifers are not directly accessible for observation representative outcrop analogues were used to study the sedimentology on a local scale conventional sedimentological classification schemes were adapted for the purpose of hydrogeological evaluations measurements of hydraulic properties were then used to define a set of 5 hydrofacies from 23 possible sediment lithofacies a digital photographic mapping procedure was developed to allow fast data acquisition in the field the sedimentologically interpreted outcrops were stored in a gis style database and thus allow the output for further sedimentological or hydrogeological analysis

electrical resistivity surveys to delineate groundwater potential aquifers in peddavanka watershed anantapur district andhra pradesh india vertical electrical resistivity soundings were conducted in order to delineate groundwater potential aquifers in peddavanka watershed which is a catchment of about 398 km2 in anantapur district andhra pradesh india the main lithologic units in the watershed are quartzite limestone shale and alluvium ninety nine vertical electrical soundings were conducted using the schlumberger configuration covering the entire watershed the data were interpreted with the help of master curves and auxiliary point charts interpretations of ves were used to generate a top layer apparent resistivity contour map and longitudinal conductance map isoresistivity contour maps were prepared and interpreted in terms of resistivity and thickness of various sub surface layers using computer software surfer and isocontour diagrams depicting the depth to bedrock were prepared resistivity results were correlated with the existing lithology based on the depth to bedrock the thickness of the saturated layer and the resistivity of the second layer a groundwater potential map has been prepared in which good moderate and poor zones are classified the study reveals that the weathered and fractured portions in shale and limestone that occur in the southernmost and central portions of the watershed area constitute the productive water bearing zones categorized as good groundwater potential aquifers

electrical methods ves and ert for identifying mapping and monitoring different saline domains in a coastal plain region alt emporda northern spain summary the spatial variability through time of the degree of salinity of soils and groundwater is a major issue concerning the sustainable management of water resources the problem is accentuated in coastal plain areas where saline bodies of different origin coexist we present an extensive geoelectrical resistivity dataset collected in the alt emporda clastic coastal aquifer system ne spain integrating the results of field campaigns undertaken within a period of more than two decades the dataset is unique in the literature and comprises highly valuable information for the investigation of saline domains the joint application of vertical electrical sounding ves and electrical resistivity tomography ert methods allowed the identification of saline domains and monitoring their evolution through time geophysical data gathered during field campaigns in 1982 2002 and 2010 were calibrated and interpreted on the basis of soil and groundwater physico chemical analyses and hydrogeological stratigraphic and geomorphological data the results illustrate the potential of electrical resistivity methods at differentiating saline domains in coastal aquifer areas and at modelling their configuration and evolution although the ves data processing allows solving the one dimensional resistivity structure of the subsurface the inversion imposes a 1d layered model thus interpretation of two dimensional structures is subject to the interpolation between discrete measures in contrast ert data offer a continuous 2d image of the resistivity distribution both laterally and in depth given that the bulk resistivity of the medium is extremely sensitive to salt content the ert profiles permitted identifying and determining the geometry of hyper saline areas characterized by resistivities of less than 5 m the study demonstrates the efficiency of the electrical methods to map subsurface conductive zones and illustrates how the accurate knowledge of the hydrogeological pattern results critical to meet this objective