late archean quetico accretionary complex superior province canada the 1200 km long quetico subprovince consists of monotonous metagraywacke with derived migmatite and granite in thrust and or transcurrent fault contact with the adjacent wabigoon and wawa metavolcanic subprovinces imbrication of sedimentary wedges derived from volcanic arcs to the north and south produced a 10 100 km wide stratigraphically north facing pile thermal relaxation in the 20 m y following accretion of the southern arc resulted in melting of the accretionary pile to produce peraluminous granite and associated low pressure metamorphism

seasonal and interannual global surface mass variations from multisatellite geodetic data 1 monthly global surface mass distribution changes are estimated in the spherical harmonic domain with a complete spectrum up to degree and order 50 the estimates are derived by inverting gps displacement series measured at roughly 450 continuously tracking sites and ocean bottom pressure obp estimates of a data assimilated ocean circulation model from 1993 to 2004 the inversion uses a hybrid estimator after singular value decomposition of the normalized measurement equations with reduced reliance on a priori spectral information the results are then compared and combined with gravity recovery and climate experiment grace gravity data to provide enhanced spectral and geographic coverage high fidelity degree 1 surface mass variation coefficients are recovered corresponding to equivalent geocenter motion with better than 0 5 mm annual amplitude precisions in all three components a clear annual surface mass cycle occurs in both gps obp and grace derived results there is very good agreement among the low degree spherical harmonic coefficients and in global geographic pattern but with significant regional differences in amplitudes annual variations of average mass over the global oceans antarctica and greenland are then derived total surface mass over both antarctica and greenland peak in their respective summers due to increased atmospheric mass large interannual variations have also been found involving several continents in the 11 year gps obp solution the patterns of variation suggest that the recent satellite laser ranging slr observation of a reversal in trend of the earth s oblateness may be largely an interannual surface mass cycle with considerable contribution from the northern continents

degree 1 earth deformation from very long baseline interferometry measurements 1 the presence of degree 1 deformations in very long baseline interferometry vlbi measurements is detected for the first time we compare vlbi measurements with the deformation field predicted using a gps determined load moment degree 1 series in the center of figure frame have root mean square values up to 3 and 1 5 mm in the up and horizontal components respectively the predicted baseline series are compared with vlbi baseline series where there are 50 matching points for the period 1996 2001 14 baselines out of 35 are significantly correlated 5 significance level for the period 1985 2001 a sinusoidal fit to the gps load moment series predicts baseline series at all vlbi epochs 49 out of 110 baselines are significantly correlated 5 significance level comparison between annual signals estimated from the vlbi and predicted baseline series shows that degree 1 deformation most likely dominates the annual phase of the vlbi series

apparent geocenter oscillations in global navigation satellite systems solutions caused by the ionospheric effect of second order 1 the international reference ionosphere iri2007 and international geomagnetic reference field igrf2005 models are used to create a worldwide model of apparent global navigation satellite systems gnss site displacements due to unmodeled higher order ionospheric delays for different time seasons and phases of the solar activity cycle it is shown that diurnal and seasonal variability of the higher order ionospheric delays causes apparent oscillations of the geometric center of the earth s figure as determined by gnss the amplitude of the oscillations in the z direction reaches 2 5 mm for the semiannual and 3 5 mm for 11 year components when satellite orbits are considered fixed and degree 1 parameterization is used failure to account for the higher order ionospheric delay when performing precise orbit determination for space borne receivers flying above while the ground based fiducial network is located below the ionosphere will result in biases between the ground and the space segment such biases changing with time and location can cause difficulties in interpretation of results from satellite altimetry and satellite gravity missions as systematic biases in orbital parameters can be interpreted as manifestations of geophysical processes on the basis of the results presented it is recommended to introduce the modeling of the second order ionospheric delay in routine gnss processing for global geodetic networks especially in view of the forthcoming solar activity maximum

seasonal clockwise gyration and tilt of the australian continent chasing the center of mass of the earth s system from gps and grace as atmosphere ocean ice and terrestrial water are redistributed the center of mass cm of the earth s system moves and the accompanying loading yields global surface deformation in australia when gps surface displacements were corrected for local mass change hydrology atmosphere and ocean with grace data the residual gps data reveal a peculiar seasonal mode of continental deformation during the southern summer the entire continent coherently shifts northwest by 1 mm and the southeastern part is uplifted while the northwestern part is subsided by 2 3 mm and the opposite patterns of deformation are observed during the southern winter such characteristic deformation could be understood to be a result of the earth s elastic response to globally averaged surface mass load generally heavier in europe during southern summer and in the south pacific ocean during southern winter it was found that such deformation is even larger than local hydrology induced loading effects in horizontal motion over australia a simple method of determining locations of the cm was developed by combining gps and grace data the latter being insensitive to the cm motion but sufficiently accurate to remove the local hydrologic and atmospheric effects in gps data the cm signals are pronounced over systematic errors in gps and grace data the cm coordinates estimated by inversion of the australian gps dataset and grace agree with the geocenter motions determined by satellite tracking analysis this study suggests an independent way of monitoring the cm motion entirely based on two distinct geodetic measurements of gps and grace

well documented travel history of mesozoic pelagic chert in japan from remote ocean to subduction zone the mino tanba belt in southwest japan a segment of the cordilleran type orogenic chain of jurassic east asia is composed mainly of a middle upper jurassic subduction accretion complex in which triassic and lower jurassic bedded radiolarian cherts occur as large allochthonous units structurally interlayered with middle upper jurassic clastic rocks high resolution microfossil conodont and radiolaria research has identified very low average sedimentation rates of about 0 5 g cm 1000 yr in the chert units similar to those of modern pelagic sediments accumulated in open ocean environments judging from the low average sedimentation rate high purity of biogenic silica long duration of continuous deposition 50 m y and wide along strike extent 1000 km the bedded radiolarian cherts in the mino tanba belt are best understood as ancient pelagic sediments that accumulated in open ocean environments accordingly the alleged origin in smaller marginal basins is untenable upward lithologic change from bedded chert to overlying siliceous mudstone in the uppermost portion of chert sequences suggests the gradual landward approach of the oceanic plate toward a trench the tectonic interlayering of these cherts and coarse grained terrigenous elastics is a secondary feature that was added through duplexing underplating in the subduction zone on the basis of the primary stratigraphy and field occurrence of triassic bedded chert in the mino tanba belt newly proposed are an idealized oceanic plate stratigraphy and a generalized travel history of a cordilleran type bedded chert from its birth at a mid oceanic ridge to its demise at a subduction zone

upb zircon and rutile chronology of archean greenstone formation and gold mineralization in the val d or region quebec abstract u pb geochronology provides an absolute time framework for the evolution of the sigma gold deposit and surrounding rocks at val d or southern abitibi subprovince the bourlamaque batholith the largest pluton in the area gives a 2699 8 1 0 ma u pb zircon age this pluton cuts the val d or formation which hosts the mineralization a u pb zircon age of 2704 9 1 1 ma on a felsic volcanic rock the colombiere rhyolite 13 km east of the mine dates that formation the gold bearing quartz vein system at sigma is hosted by andesites and two generations of porphyry intrusions all metamorphosed to the greenschist facies the oldest porphyry porphyritic diorite shows the same deformation as the volcanic rocks and has a 2703 7 2 5 ma u pb zircon age the porphyritic diorite and volcanic rocks are cut by feldspar porphyry dykes which post date regional folding and have a 2694 0 2 2 ma u pb zircon age regional greenschist metamorphism has been dated directly with a u pb date of 2684 7 ma on rutile in the colombiere rhyolite the mineralization and hydrothermal alteration in the mine are superimposed on the metamorphic minerals hydrothermal rutile from an alteration halo around the veins in andesite has a 2599 9 ma u pb age textural evidence clearly indicates that the wall rock alteration and vein filling are contemporaneous and hence the vein system and gold mineralization appear to have developed at least 80 m y after the formation and metamorphism of host greenstones

surface mass redistribution inversion from global gps deformation and gravity recovery and climate experiment grace gravity data monitoring hydrological redistributions through their integrated gravitational effect is the primary aim of the gravity recovery and climate experiment grace mission time variable gravity data from grace can be uniquely inverted to hydrology since mass transfers located at or near the earth s surface are much larger on shorter timescales than those taking place within the deeper earth and because one can remove the contribution of atmospheric masses from air pressure data yet it has been proposed that at larger scales this may be achieved independently by measuring and inverting the elastic loading associated with redistributing masses e g with the global network of the international gps service igs this is particularly interesting as long as grace monthly gravity solutions do not yet match the targeted baseline accuracies at the lower spherical harmonic degrees in this contribution 1 we describe and investigate an inversion technique which can deal jointly with gps data and monthly grace solutions 2 previous studies with gps data have used least squares estimators and impose solution constraints through low degree spherical harmonic series truncation here we introduce a physically motivated regularization method that guarantees a stable inversion up to higher degrees while seeking to avoid spatial aliasing 3 we apply this technique to gps data provided by the igs service covering recent years we can show that after removing the contribution ascribed to atmospheric pressure loading estimated annual variations of continental scale mass redistribution exhibit pattern similar to those observed with grace and predicted by a global hydrology model although systematic differences appear to be present 4 we compute what the relative contribution of grace and gps would be in a joint inversion using current error estimates gps could contribute with up to 60 to degree 2 till 4 spherical harmonic coefficients and up to 30 for higher degree coefficients

three dimensional deformation analysis global vector spherical harmonic and local finite element representation abstract deformation elements which have global support such as tidal induced displacements are represented in terms of vector spherical harmonics in contrast local strain and local rotation are represented in terms of irregularly shaped three dimensional finite elements these geodetic finite elements reflect the structure of a geodetic network which is arbitrarily shaped various continuity classes are discussed numerical examples are presented

mode of mixture of oceanic fragments and terrigenous trench fill in an accretionary complex example from southern sakhalin abstract four modes of mixture of oceanic materials such as cherts limestones and basalts and terrigenous trench fill sediments are recognized in the cretaceous accretionary complexes in southern sakhalin far eastern pacific margin of the u s s r the first mode is a thin skinned stacking of pelagic bedded cherts with black shale due to duplex formation in association with shallow underplating or off scraping the second mode is a mixture of the uppermost part of the oceanic crust with terrigenous trench fill sediments due to olistostrome formation reconstruction of the original sequence in ascending order suggests that the basement is pillow basalt with overlying pelagic sediments of chert and limestone olistostrome caused by collapse of oceanic crust due to its bending before encountering a trench and finally trenchfill sediments of turbidite this sequence is imbricated by thrusting which appears to have occurred at the time of underplating the third mode is a tectonic mixing of oceanic fragments and terrigenous sediments due to shear which is related to underthrusting of the oceanic plate a reduction in the supply of trench fill sediments causes copious accretion of the upper part of oceanic crust the fourth mode is in situ basalt volcanism at the trench where thick baked margins of terrigenous shale are formed around the injected basalts this mode appears to represent a ridge trench encounter these four different modes of mixing seem to be usual in ancient accretionary complexes in orogenic belts

global geodesy using gps without fiducial sites baseline lengths and geocentric radii have been determined from gps data without the use of fiducial sites data from the first gps experiment for the iers and geodynamics gig 91 have been analyzed with a no fiducial strategy a baseline length daily repeatability of 2 mm 4 parts per billion was obtained for baselines in the northern hemisphere comparison of baseline lengths from gps and the global vlbi solution glb659 caprette et al 1990 show rms agreement of 2 1 parts per billion the geocentric radius mean daily repeatability for all sites was 15 cm comparison of geocentric radii from gps and sv5 murray et al 1990 show rms agreement of 3 8 cm given n globally distributed stations the n n 1 2 baseline lengths and n geocentric radii uniquely define a rigid closed polyhedron with a well defined center of mass geodetic information can be obtained by examining the structure of the polyhedron and its change with time

a review of the superior province of the canadian shield a product of archean accretion abstract the superior province consists of northern and southern high grade gneiss subprovinces and a central region of alternating granite greenstone and metasedimentary belts subprovinces are commonly fault bounded and display contrasting lithological assemblages metamorphic and structural styles geophysical characteristics and ages they are comparable to phanerozoic suspect terranes the middle and late archean rocks of the superior province are of mantle and juvenile crustal origin with little evidence of inheritance of components older than ca 3 1 ga high grade gneiss subprovinces are mainly deeper level equivalents of the supracrustal rich belts but one minnesota river valley is part of an older ca 3 6 ga terrane that was juxtaposed late in the tectonic history granite greenstone terranes are characterized by low grade volcano sedimentary sequences tholeiitic komatiitic submarine lava plain tholeiitic calc alkalic submarine to subaerial central complexes early platform type quartz arenite stromatolitic carbonate late timiskaming type shoshonitic alkalic volcanic fluvial sediment that range in age from ca 3 0 ga to 2 7 ga the volcanics represent oceanic island arc and continental arc volcanism the quartz arenite carbonate sequences deposition on relatively stable early formed ca 3 0 ga crust and the timiskaming type sequences deposition in pull apart basins developed along strike slip faults late archean ca 2 75 2 70 ga greenstone sequences occur throughout the superior province middle archean ca 3 0 2 8 ga sequences are common in northern and central superior province rare or absent in the south volcanism was accompanied by mafic to trondhjemitic plutonism the metasedimentary belts consist of variably metamorphosed volcanogenic turbidites with detrital zircons ranging in age from ca 3 0 ga to 2 7 ga the metasediments were deposited after major volcanism and probably represent accretionary prisms late archean orogenesis accompanied and followed by calc alkalic plutonism youngs southward from about 2 73 2 72 ga to 2 70 2 68 ga it involved large scale north south compression and dextral transpression and displays thin to thick skinned transitions the contemporaneity of events along the lengths of the belts and their southward younging coupled with the evidence of major compression are consistent with subduction driven oblique accretion of oceanic and continental volcanic arcs accretionary sedimentary wedges older microcontinental fragments etc in a convergent margin setting analogous to parts of the pacific rim differences eg abundance of komatiites and tonalitic plutonic suites are attributable to a hotter archean mantle

spinifex biogeochemical expressions of buried gold mineralisation the great mineral exploration penetrator of transported regolith a major challenge for mineral explorers is to efficiently detect mineralisation beneath the weathered cover that extends across the landscape determination of the elemental composition of plants biogeochemical exploration can aid in the detection of buried ore deposits due to their root penetration through the weathered cover at the coyote prospect in western australia a range of plant species were sampled traversing a buried au orebody here it is shown that the soft spinifex triodia pungens accumulated important pathfinder elements related to the mineralisation which produced a multi element surficial expression of the underlying ore deposit spinifex grasses are one of the most widespread grasses over the australian continent and have vertical root systems that can extend for many 10s of metres through sedimentary cover and interact with buried mineral deposits and alteration zones in the underlying substrate spinifex biogeochemistry therefore has potential to be a low cost low environmental impact sampling medium for mineral exploration programs across large parts of arid australia the examination of similar grasses from other semi arid and arid regions from around the world therefore also warrants further investigation

groundwater flow regime within the gambier embayment of the otway basin australia evidence from hydraulics and hydrochemistry a conceptual groundwater flow model for the cainozoic sequence of the gambier embayment of the otway basin south australia is developed using hydraulic head distribution environmental isotopes and hydrochemical data local flow cells occur within the upper sequence of the gambier unconfined aquifer and are recognised by local relief of the water table and as rapid lateral variations in chloride 14c 2h and 18o concentrations indicating that regional flow is not dominant in the upper portion of the unconfined aquifer these localised systems are topographically controlled and have developed in response to undulating stranded coastal dune ridges of the bridgewater formation recharge areas correspond to dune highs while discharge is focused towards the lower lying interdunal regions total dissolved solids concentrations are controlled by evapotranspiration processes during recharge and ion ratios are modified by water rock interactions within the groundwater system groundwaters are more dilute in the southern section of the basin where the surplus of precipitation over evapotranspiration in the winter months is greater than that in the northern section of the basin a regional flow system with interaquifer mixing has developed within the confined dilwyn aquifer system recharge to the dilwyn aquifer has been identified downgradient from the basin margin via downward leakage from an intermediate flow system within the gambier unconfined aquifer to the deeper regional flow system of the confined dilwyn aquifer interaquifer mixing appears to be geologically controlled in the south by the elevated gambier axis and in the north by the kanawinka fault downgradient of the zero head difference line lateral flow appears to be the dominant transport mechanism within the dilwyn aquifer as indicated by constant chloride concentrations monotonic decrease in radiocarbon concentration and more negative 2 and 18 o composition

assessing the precision in loading estimates by geodetic techniques in southern europe summary this paper investigates the precision of the estimation of geophysical fluid load deformation computed from grace space gravity gps vertical displacement and geophysical fluids models global circulation models gcms for ocean atmosphere and hydrology using the three cornered hat method this method allows the estimation of the variance of the errors of each technique when the same quantity is monitored by three instruments with independent errors appliedonanetworkofstations severalpointsofviewcanbeconsidered thetechnique level inordertodeterminetheerrorofeachtechnique grace gpsandgcms thesolution level allowingtocomparetheprecisionofthesametechniquewhendifferentstrategies models are used and the station level in order to emphasize local anomalies and geographical patterns in particular our results show a precision of the loading vertical displacement at the level of 1 mm when using grace or the fluid models and of 2 mm using gps we do not find significant differences between the precision of different solutions of the same techniques even when there are strong differences in the data processing

accretion of archean oceanic plateau fragments in the abitibi greenstone belt canada the arc arc collision model is often applied to the evolution of archean greenstone belts this model predicts concordant stratigraphic relations among the various lithologies evolving generally from komatiitic tholeiitic affinities toward calc alkalic affinities new geological data from the malartic composite block of the abitibi greenstone belt indicate that this volcanic pile rather than representing a conformable sequence is composed of four distinct mafic lithotectonic domains that are overlain by a calc alkalic sequence the mafic domains are thought to be examples of accreted archean oceanic plateau material that were deformed during their collage state the younger calc alkalic sequence represents extension related volcanism that erupted through the ac creted and deformed plateau material possibly as a consequence of ridge subduction in a regime of oblique convergence the relations described here may represent a common feature of archean terranes

predictions of crustal deformation and of geoid and sea level variability caused by oceanic and atmospheric loading summary in this paper we consider several small effects related to oceanic loading of the earth and atmospheric loading of the oceans non tidal ocean loading induces changes in oceanic bottom pressure which in turn deform the geoid and the nearby crust changes in bottom pressure are derived from estimates of sea surface height variability and density changes output from an oceanic general circulation model sea surface heights measured by the topex poseidon altimeter are also used to infer changes in bottom pressure we estimate that non tidal ocean loading can typically cause 5 mm of peak to peak 2 mm root mean square rms vertical motion at sites near the shore with displacements of up to 10 mm possible amplitudes of horizontal displacements are about one third those of vertical ones deformation associated gravity changes are usually of the order of 2 3 pgal however peak to peak changes of 5 pgal are also predicted loading induced geoid perturbations in mid ocean regions are typically 5 10 mm peak to peak 3 mm rms and can extend over a region of 20 in the case of atmospheric loading of the oceans we estimate the difference between the inverted barometer correction usually used to describe the ocean s response to atmospheric pressure and the complete equilibrium response there are two sources of this difference one is that the inverted barometer correction does not conserve oceanic mass we use national meteorological center nmc global pressure data to estimate the time dependent average change in pressure over the oceans a time series of the net pressure over the oceans contains an annual signal with a peak to peak amplitude of 1 2 mbar superimposed on a linear trend of 0 09 mbar yr the secular signal is caused by a redistribution of atmospheric mass from over continental land masses to the oceans we conclude that this effect introduces additional variability into the ocean s response to pressure at annual secular and multi year timescales with a total peak to peak amplitude of a few tens of millimetres the second difference between the inverted barometer response and the complete equilibrium response is due to gravitational forcing by the atmosphere and by the displaced mass in the solid earth and oceans caused by the atmospheric loading this effect is largest within about 1000 km of the coast and at high latitudes we use nmc pressure data to estimate the effect and find that it causes differences from the inverted barometer solution in those regions of up to 10 30mm peak to peak with values as large as 50 60 mm possible at certain locations the time dependence of this effect is negatively correlated with the inverted barometer response the effect causes an apparent reduction of the inverted barometer response by a few per cent within a few hundred kilometres of the coast with reductions of more than 6 7 per cent at a few places

large scale global surface mass variations inferred from gps measurements of load induced deformation 1 detrended crustal deformation measurements from a global network of up to 200 continuous global positioning system gps tracking sites are inverted for low degree and order n m 6 spherical harmonic series of surface mass variations an independent geophysical model of the atmosphere oceans and water and snow on land is also used to guide the spherical harmonic truncation and to evaluate aliasing errors in the results inversion uncertainties decrease significantly as spatial coverage and data quality improve with time especially in the last few years consequently gps inverted seasonal geocenter and low degree zonal harmonics converge to those determined by measurements from satellite laser ranging slr significant n 1 and non zonal variations have also been found

archaean plate tectonics revisited 1 heat flow spreading rate and the age of subducting oceanic lithosphere and their effects on the origin and evolution of continents a simple model which relates the rate of seafloor creation and the age of the oceanic lithosphere at subduction to the rate of continental accretion can successfully explain the apparent differences between archaean and phanerozoic terrains in terms of plate tectonics the model has been derived using the following parameters 1 the spreading rate at mid ocean ridges 2 the age of the oceanic lithosphere at the time of subduction 3 the area age distribution of the seafloor 4 the continental surface area as a fraction of the total surface area of the earth and 5 the erosion rate of continents as a function of continental surface area and the total number of continental masses observations in phanerozoic terranes suggest that there are profound differences in the nature and volume of subduction zone igneous activity depending upon the age of the oceanic lithosphere being subducted and the nature of the overriding plate that is either continental or oceanic the subduction of young oceanic lithosphere less than 50 m y old which is thermally buoyant appears to result in a reduced volume of igneous activity most of the igneous activity caused by subduction of young oceanic lithosphere is either siliceous plutonism or bimodal tholeiitic rhyolitic volcanism when very young lithosphere is being subducted 50 m y old appears to result in greater volumes of igneous activity including the eruption of andesitic magmas thus andesites could only begin to be abundant in the rock record when older oceanic lithosphere began to be subducted our model predicts that as the earth aged and as heat flow from the interior of the earth diminished the proportion of old oceanic lithosphere being subducted increased fundamentally changing the nature of subduction zone igneous activity and the rate of continental accretion if the subduction of old oceanic lithosphere results in an 8 10 times greater volume of subduction zone magmatism our model predicts or explains all of the following observed features of earth history 1 archaean terranes appear to record two periods of rapid continental accretion between 3 8 and 3 5 b y ago and between 3 1 and 2 6 b y ago 2 there are very few differences and many marked similarities between rocks from archaean terranes and equivalent rocks from phanerozoic terranes 3 the total continental area appears to have remained essentially constant for the past 2 b y 4 archaean andesites are comparatively rare and the relative abundances of mafic and siliceous rocks appear to change during the archaean and the proterozoic with siliceous volcanics becoming proportionately more abundant in the geologic record with time 5 plutonic tonalites and trondhjemites appear to have been relatively much more abundant during the archaean plate tectonics is thus shown to have evolved over time due to a gradually decreasing rate of creation of oceanic lithosphere meaning that archaean tectonics and phanerozoic tectonics are but two points on an evolutionary continuum

vertical carbon 14 profiles for resolving spatial variability in recharge in arid environments summary groundwater age tracers are often measured to help constrain estimates of groundwater recharge especially in arid environments where other methods are unsuitable however multiple processes can influence the shape of vertical tracer profiles in an aquifer including 1 variation in tracer input concentrations from the unsaturated zone 2 the role of diffusion in transporting tracer into the aquifer when fluxes are low and 3 spatial variability in recharge this study demonstrates the influence of spatially variable recharge and spatially variable carbon 14 14 c activities in the unsaturated zone on vertical 14 c profiles in groundwater through groundwater flow and solute transport modelling we demonstrate that recharge estimated from single point measurements of 14 c may be wrong more than an order of magnitude when unsaturated zone 14 c activities and recharge vary spatially we then present a case study from the ti tree basin in arid central australia where detailed profiles of 14 c activity in unsaturated zone gas and groundwater have been measured and spatial variability in unsaturated zone 14 c is observed ranging from 54 to 106 pmc above the watertable through modelling our data we show that when unsaturated zone 14 c activities are known measurement of the 14 c profile can help constrain estimates of recharge and its spatial variability this approach improves our understanding of groundwater flow in the ti tree basin by showing mountain front recharge to be an important mechanism

time variability of the earth s gravity field hydrological and oceanic effects and their possible detection using grace the grace satellite mission scheduled for launch in 2001 is designed to map out the earth s gravity field to high accuracy every 2 4 weeks over a nominal lifetime of 5 years changes in the gravity field are caused by the redistribution of mass within the earth and on or above its surface grace will thus be able to constrain processes that involve mass redistribution in this paper we use output from hydrological oceanographic and atmospheric models to estimate the variability in the gravity field i e in the geoid due to those sources we develop a method for constructing surface mass estimates from the grace gravity coefficients we show the results of simulations where we use synthetic grace gravity data constructed by combining estimated geophysical signals and simulated grace measurement errors to attempt to recover hydrological and oceanographic signals we show that grace may be able to recover changes in continental water storage and in seafloor pressure at scales of a few hundred kilometers and larger and at timescales of a few weeks and longer with accuracies approaching 2 mm in water thickness over land and 0 1 mbar or better in seafloor pressure

carbon 14 and stable isotope data for an area in the murray basin its use in estimating recharge measurements of the carbon 14 concentration of water in 33 boreholes in a saline unconfined aquifer in southern australia have been interpreted to show that local recharge under natural conditions has a mean annual value which falls between 0 1 and 0 2 mm yr 1 the chloride concentration of groundwater is log normally distributed suggesting that its source is rainfall the estimate of mean annual recharge to the aquifer made using chloride is 0 25 mm yr 1

repetitive cyclical volcanism in the late archean larder lake group near kirkland lake ontario implications of geochemistry on magma genesis abstract the larder lake group is the basal stratigraphic unit of the upper supergroup the younger magmatic cycle of the abitibi greenstone belt of the superior province three major suites of extrusive and hypabyssal rocks are recognized a a high magnesian suite of komatiite to mg basalt b a tholeiitic series with mg rich and fe rich basaltic varieties and c a low magnesian series of basalt to rhyodacite fourteen such subcycles were recognized in the boston iron range south of kirkland lake and are grouped in four major stratigraphic intervals the entire larder lake group magma series evolved from a peridotitic mantle source through various stages of partial melting and fractional crystallization lree enriched tholeiites are interpreted as the initial products of low degrees of melting of a chondritic mantle both magnesian suites show lree depleted patterns and identical zr y and zr ti ratios suggesting that their parental magmas were generated by partial melting of the residual mantle from which the tholeiitic melts had been previously derived the low magnesian suite which is genetically related to a komatiitic magma series includes compositions as silicic as rhyodacite

subprovince accretion tectonics in the south central superior province development of tectonic subprovinces as shear bounded granite greenstone and sediment dominated terranes during the late archaean is reviewed and interpreted from relationships between portions of

the great whirl observations of its seasonal development and interannual variability 1 in situ measurements are used together with sea surface height data to study the development and variability of the great whirl gw a large quasi stationary anticyclone that appears off the coast of somalia during the southwest monsoon season we find that anticyclonic circulation indicative of the gw appears on average in april almost two months before the onset of the southwest monsoon winds this early initiation is coincident with the arrival of annual rossby waves at the western boundary with the onset of the monsoon winds in early june the gw proper intensifies quickly remaining at its peak throughout july august and september and dissipating about one month after the winds have died the gw is present for an average 166 30 days per year and the position of its northern flank close to 9 n coincides with the latitude of zero wind stress curl the intraseasonal variability of the gw is intense as a result of mutual advection with one to three flanking cyclones which accompany the gw 70 of the time and tend to circulate clockwise around it there is no consistent seasonal pattern for the development or dissipation of the gw although movement to the southwest is common toward the end of the season the gw of 1995 deepened from 200 m in june to over 1000 m in september and strengthened from a swirl transport of 10 to 60 sv cool waters in its core resulted from advection via the somali current and some local vertical mixing

a 3500 ma plutonic and volcanic calc alkaline province in the archaean east pilbara block variably foliated predominantly granodioritic plutonic rocks from the northern part of the shaw batholith in the east pilbara archaean craton are dated at 3 499 22 ma 2 errors by a whole rock pb pb isochron these rocks intrude the surrounding greenstone sequence and their age is indistinguishable from that sequence high strain grey gneisses which occupy much of the western and southern shaw batholith are chemically and isotopically similar to the north shaw suite and are inferred to have been derived from this suite by tectonic processes felsic volcanics within the greenstones together with a major portion of the granitic batholiths apparently formed in a calc alkaline volcanic and plutonic province at 3 500 ma this volcanic and plutonic suite is similar to modern calc alkaline suites on the basis of major element rare earh element and most other trace element contents the archaean suite contrasts with modern equivalents only in having lower concentrations of hree and higher concentrations of ni and cr

a model of ocean crust accretion for the superior province canada abstract one of the keys to understanding the origin of archaean greenstone belts lies in the geological relationships between mafic and ultramafic greenstones felsic to intermediate volcanic rocks and terrigenous sediments traditional models for greenstone belt evolution have been based on in situ stratigraphic relationships most of these models for example an oceanic island arc developed on oceanic basement back arc basins and the recently popular plume model predict concordant stratigraphic relationships among the various greenstone belt lithologies however rather than being depositional in nature several authors have indicated that many of the relationships between the different lithologies in greenstone belts are in fact tectonic suggesting an allochthonous origin for most greenstone sequences all of these latter models make analogies to phanerozoic tectonic processes involving accretion of oceanic materials with volcanism related to both plate subduction and rifting in this paper we have evaluated the geological relationships between volcanic rocks and sediments in three regions in the superior province where the accretion of oceanic material can be documented and direct comparisons are made to geological processes in phanerozoic accretionary complexes in the malartic area in the southeastern abitibi subprovince 3 to 4 km thick slices of komatiite and tholeiite with intercalated terrigenous sediment are tectonically imbricated and are overlain by calc alkaline volcanics which postdate tectonic stacking in both the larder lake region of the southwestern abitibi belt and in the beardmore geraldton belt at the south eastern limit of the wabigoon belt slices of iron rich tholeiite and chemical sediments of an oceanic origin are tectonically imbricated with terrigenous sediment the malartic val d or area is considered to be an example of accretion of an archaean oceanic plateau while the larder lake and the beardmore geraldton regions are potentially typical of accretion of normal oceanic crust in an arc environment phanerozoic accretion of oceanic crust is accompanied by a step back in subduction and in this paper we suggest that oceanic crust accretion may have been the principal mechanism by which the locus of subduction migrated towards the south of the superior province asthenospheric upwelling associated with the isolated sinking plate may have been responsible for widespread late magmatism this scenario requires that magmas be erupted through previously accreted volcanic plutonic and sedimentary material furthermore later ridge subduction will result in transpressional tectonics and eruption of mafic sequences over mature and immature volcano plutonic sequences the combined result of the plate tectonic scenario envisaged would result in the well described cyclic stratigraphy of many granite greenstone sequences

gliding and overthrust nappe tectonics in the barberton greenstone belt abstract regional recumbent folds inverted stratigraphy nappes and olistostromes are described from the southern part of the 3 3 3 5 ga barberton greenstone belt overthrusting of thin rigid silicified slabs with minimum dimensions of 25 km2 and up to 500 m in thickness occurred over minimum distances of 86 km more ductile and coherent units were overfolded up to at least 2 km during their emplacement the glide planes on which these nappes travelled were zones of high fluid pressures related to hydrothermal fluid circulation patterns driven by heat sources from igneous intrusions the upwelling areas of the geothermal convection cells were sites of mud pools and hydrothermal vents which may mark the trailing edges pull aparts of the overthrust units progressive silica and carbonate precipitation due to decreasing temperatures within the zones of fluid migration distant from the areas of high heat flow probably acted as built in braking systems below the travelling slabs active sedimentation and metasomatism during this tectonism indicates a protracted history for the evolution of the greenstone belt the recognition of nappe and overthrust tectonics in the barberton belt processes which may have been commonplace in archaean terrains necessitates a re evaluation of the stratigraphy of this belt

snow load effect on the earth s rotation and gravitational field 1979 1985 a global monthly snow depth data set has been generated from the nimbus 7 satellite observations using passive microwave remote sensing techniques in this paper we analyze 7 years of data 1979 1985 to compute the snow load effects on the earth s rotation and low degree zonal gravitational field a uniform sea level decrease has been assumed in order to conserve water mass the resultant time series show dominant seasonal cycles the annual peak to peak variation in j2 is found to be 2 3 x 10 o that in j3 to be 1 1 x 10 o and believed to decrease rapidly for higher degrees the corresponding change in the length of day is 41 us the annual wobble excitation is 4 9 marc sec 109 o for the prograde motion component and 4 8 marc sec 28 o for the retrograde motion component the excitation power of the chandler wobble due to the snow load is estimated to be about 25 db less than the power needed to maintain the observed chandler wobble the superior quality of the satellite data over conventional data acquired by ground observations and modeling is demonstrated we also discuss the role of atmospheric water and the problems arising from the lack of snow load observations over the antarctic and greenland ice sheets

impacts of cave air ventilation and in cave prior calcite precipitation on golgotha cave dripwater chemistry southwest australia abstract speleothem trace element chemistry is an important component of multi proxy records of environmental change but a thorough understanding of hydrochemical processes is essential for its interpretation we present a dripwater chemistry dataset pco2 alkalinity ca sicc mg and sr from an eight year monitoring study from golgotha cave building on a previous study of hydrology and dripwater oxygen isotopes treble et al 2013 golgotha cave is developed in quaternary aeolianite and located in a forested catchment in the mediterranean type climate of southwest western australia all dripwaters from each of the five monitored sites become supersaturated with respect to calcite during most of the year when cave ventilation lowers pco2 in cave air in this winter ventilation mode prior calcite precipitation pcp signals of increased mg ca and sr ca in dripwater are attributed to stalactite deposition a fast dripping site displays less evolved carbonate chemistry implying minimal stalactite growth phenomena which are attributed to minimal degassing because of the short drip interval 30 s we employ hydrochemical mass balance modelling techniques to quantitatively investigate the impact of pcp and co2 degassing on our dripwater initially we reverse modelled dripwater solutions to demonstrate that pcp is dominating the dripwater chemistry at our low flow site and predict that pcp becomes enhanced in underlying stalagmites secondly we forward modelled the ranges of solution mg ca variation that potentially can be caused by degassing and calcite precipitation to serve as a guide to interpreting the resulting stalagmite chemistry we predict that stalagmite trace element data from our high flow sites will reflect trends in original dripwater solutes preserving information on biogeochemical fluxes within our system by contrast stalagmites from our low flow sites will be dominated by pcp effects driven by cave ventilation our poorly karstified system allows us to highlight and quantify these in cave pcp processes which are otherwise masked at sites where karstification is more developed and hydrogeology is more complex our modelling also shows enhanced co2 source production in the unsaturated zone that is attributed to deeply rooted vegetation and increasing bioproductivity which we link to forest recovery after fires impacted our site during 2006 ce

numerical simulations of global scale high resolution hydrological crustal deformations 1 high resolution load induced crustal deformations calculated from numerical models are tested for their ability to predict hydrologically induced station height variability as they are known to be large enough to affect epoch wise parameters obtained from the analysis of global geodetic networks loading contributions due to terrestrial water storage as given by global hydrological models are calculated on a 0 5 global regular grid with daily temporal resolution apart from the dominant seasonal variations the hydrological loading signal discloses also rapid changes exceeding 1 mm in several regions that can be associated with major precipitation events and river floods locally strong loading signals with exceptionally high amplitudes in many cases even with nonseasonal nature occur along the major river channels only high resolution loading calculations considering also the water mass anomalies stored in the model river flow can resolve the correct amplitudes in the surrounded area up to 100 km distance the comparison of the modeled hydrological surface deformation with gps station time series shows that high resolution hydrological loading estimates based on global scale models are able to explain a considerable fraction up to 54 of the observed vertical station movements caused by continental water storage variations

a review of single sample based models and other approaches for radiocarbon dating of dissolved inorganic carbon in groundwater abstract numerous methods have been proposed to estimate the pre nuclear detonation 14c content of dissolved inorganic carbon dic recharged to groundwater that has been corrected adjusted for geochemical processes in the absence of radioactive decay 14c0 a quantity that is essential for estimation of radiocarbon age of dic in groundwater the models approaches most commonly used are grouped as follows 1 single sample based models 2 a statistical approach based on the observed curved relationship between 14c and 13c data for the aquifer and 3 the geochemical mass balance approach that constructs adjustment models accounting for all the geochemical reactions known to occur along a groundwater flow path this review discusses first the geochemical processes behind each of the single sample based models followed by discussions of the statistical approach and the geochemical mass balance approach finally the applications advantages and limitations of the three groups of models approaches are discussed the single sample based models constitute the prevailing use of 14c data in hydrogeology and hydrological studies this is in part because the models are applied to an individual water sample to estimate the 14c age therefore the measurement data are easily available these models have been shown to provide realistic radiocarbon ages in many studies however they usually are limited to simple carbonate aquifers and selection of model may have significant effects on 14c0 often resulting in a wide range of estimates of 14c ages of the single sample based models four are recommended for the estimation of 14c0 of dic in groundwater pearson s model ingerson and pearson 1964 pearson and white 1967 han plummer s model han and plummer 2013 the iaea model gonfiantini 1972 salem et al 1980 and oeschger s model geyh 2000 these four models include all processes considered in single sample based models and can be used in different ranges of 13c values in contrast to the single sample based models the extended gonfiantini zuppi model gonfiantini and zuppi 2003 han et al 2014 is a statistical approach this approach can be used to estimate 14c ages when a curved relationship between the 14c and 13c values of the dic data is observed in addition to estimation of groundwater ages the relationship between 14c and 13c data can be used to interpret hydrogeological characteristics of the aquifer e g estimating apparent rates of geochemical reactions and revealing the complexity of the geochemical environment and identify samples that are not affected by the same set of reactions processes as the rest of the dataset the investigated water samples may have a wide range of ages and for waters with very low values of 14c the model based on statistics may give more reliable age estimates than those obtained from single sample based models in the extended gonfiantini zuppi model a representative system wide value of the initial 14c content is derived from the 14c and 13c data of dic and can differ from that used in single sample based models therefore the extended gonfiantini zuppi model usually avoids the effect of modern water components which might retain bomb pulse signatures the geochemical mass balance approach constructs an adjustment model that accounts for all the geochemical reactions known to occur along an aquifer flow path plummer et al 1983 wigley et al 1978 plummer et al 1994 plummer and glynn 2013 and includes in addition to dic dissolved organic carbon doc and methane ch4 if sufficient chemical mineralogical and isotopic data are available the geochemical mass balance method can yield the most accurate estimates of the adjusted radiocarbon age the main limitation of this approach is that complete information is necessary on chemical mineralogical and isotopic data and these data are often limited failure to recognize the limitations and underlying assumptions on which the various models and approaches are based can result in a wide range of estimates of 14c0 and limit the usefulness of radiocarbon as a dating tool for groundwater in each of the three generalized approaches single sample based models statistical approach and geochemical mass balance approach successful application depends on scrutiny of the isotopic 14c and 13c and chemical data to conceptualize the reactions and processes that affect the 14c content of dic in aquifers the recently developed graphical analysis method is shown to aid in determining which approach is most appropriate for the isotopic and chemical data from a groundwater system

crustal displacements due to continental water loading the effects of long wavelength 100 km seasonal variability in continental water storage on vertical crustal motions are assessed the modeled vertical displace ments arm have root mean square rms values for 1994 1998 as large as 8 mm with ranges up to 30 mm and are predominantly annual in character regional strains are on the order of 20 nanostrain for tilt and 5 nanostrain for hori zontal deformation we compare arm with observed global positioning system gps heights aro which include ad justments to remove estimated effects of atmospheric pres sure and annual tidal and non tidal ocean loading for 147 globally distributed sites when the aro time series are ad justed by arm their variances are reduced on average by an amount equal to the variance of the arm of the aro time series exhibiting a strong annual signal more than half

constraining spatial variability in recharge and discharge in an arid environment through modeling carbon 14 with improved boundary conditions carbon 14 14c has been widely used to estimate groundwater recharge rates in arid regions and is increasingly being used as a tool to assist numerical model calibration however lack of knowledge on 14c inputs to groundwater potentially limits its reliability for constraining spatial variability in recharge in this study we use direct measurements of 14c in the unsaturated zone to develop a 14c input map for a regional scale unconfined aquifer in the ti tree basin in central australia the map is used as a boundary condition for a 3 d groundwater flow and solute transport model for the basin the model is calibrated to both groundwater 14c activity and groundwater level and calibration is achieved by varying recharge rates in 18 hydrogeological zones we test the sensitivity of the calibration to both the 14c boundary condition and the number or recharge zones used the calibrated recharge rates help resolve the conceptual model for the basin and demonstrate that spatially distributed discharge through evapotranspiration is an important part of the water balance this approach demonstrates the importance of boundary conditions for 14c transport modeling 14c input activity for improving estimates of spatial variability in recharge and discharge

a new global mode of earth deformation seasonal cycle detected we have detected a global mode of earth deformation that is predicted by theory precise positioning of global positioning system sites distributed worldwide reveals that during february to march the northern hemisphere compresses and the southern hemisphere expands such that sites near the north pole move downward by 3 0 millimeters and sites near the equator are pulled northward by 1 5 millimeters the opposite pattern of deformation occurs during august to september we identify this pattern as the degree one spherical harmonic response of an elastic earth to increased winter loading of soil moisture snow cover and atmosphere data inversion shows the load moment s trajectory as a great circle traversing the continents peaking at 6 9 1022 kilogram meters near the north pole in winter indicating interhemispheric mass exchange of 1 0 1016 0 2 1016 kilograms

co2 dynamics in the amargosa desert fluxes and isotopic speciation in a deep unsaturated zone 1 natural unsaturated zone gas profiles at the u s geological survey s amargosa desert research site near beatty nevada reveal the presence of two physically and isotopically distinct co2 sources one shallow and one deep the shallow source derives from seasonally variable autotrophic and heterotrophic respiration in the root zone scanning electron micrograph results indicate that at least part of the deep co2 source is associated with calcite precipitation at the 110 m deep water table we use a geochemical gas diffusion model to explore processes of co2 production and behavior in the unsaturated zone the individual isotopic species 12co2 13co2 and 14co2 are treated as separate chemical components that diffuse and react independently steady state model solutions constrained by the measured 13c in co2 and 14c in co2 profiles indicate that the shallow co2 source from root and microbial respiration composes 97 of the annual average total co2 production at this arid site despite the small contribution from deep co2 production amounting to 0 1 mol m 2 yr 1 upward diffusion from depth strongly influences the distribution of co2 and carbon isotopes in the deep unsaturated zone in addition to diffusion from deep co2 production 14c exchange with a sorbed co2 phase is indicated by the modeled 14c profiles confirming previous work the new model of carbon isotopic profiles provides a quantitative approach for evaluating fluxes of carbon under natural conditions in deep unsaturated zones

degree 2 harmonics of the earth s mass load estimated from gps and earth rotation data a fluid mobile atmosphere and oceans surrounds the solid earth and upon its land surface lays a continually changing distribution of ice snow and ground water the changing distribution of mass associated with the motion of these surficial fluids changes the earth s rotation by changing its inertia tensor and changes the earth s shape by changing the load on the solid earth it has recently been demonstrated that large scale changes of the earth s shape and hence of the mass load causing the earth s shape to change can be measured using the global network of gps receivers here the degree 2 mass load coefficients determined from gps data are compared with those obtained from earth orientation observations from which the effects of tides winds and currents have been removed good agreement is found between these two estimates of the degree 2 mass load particularly at seasonal frequencies

underplated units in an accretionary complex melange of the shimanto belt of eastern shikoku southwest japan imbricated thrust stacks composed of melange and oceanic slabs occur in the shimanto belt eastern shikoku sw japan the melanges are divided into two types melange i consists of lenticular sandstone blocks surrounded by scaly shale matrix and melange ii is composed of blocks of oceanic material such as basalts cherts and red shale in a scaly matrix of shale melange ii is observed only near the boundaries between melange i and oceanic slabs the fabric of melange i indicates progressive deformation during underthrusting of originally coherent trench fill turbidites layer parallel extension characterizes early deformation and is divided into two stages an early stage formed during normal faulting and a subseguent stage formed perpendicular to the early extension the early extension is interpreted in terms of riedel shear associated with layer parallel shearing and tectonically induced loading normal to the layering the second extension is due to sticking thrust movement late deformation of melange i is represented by folding in association with layer parallel shearing this appears to be related to compression just before or during underplating of melange i beneath the accretionary prism layer parallel shear extends downward due to strain hardening of sheared sediments and then reaches to the base of the sediments subsequently the shear zone penetrates pelagic sediments and finally oceanic basement at this time melange ii is formed by the shearing an imbricated stack of melanges i ii and oceanic slabs forms duplexes during the underplating process the weak metamorphism of the melange complex in the study area suggests that underplating occurs at shallow depths where trench fill is thin

a complete spherical harmonic approach to luni solar tides summary in this work a spherical harmonic theory of ocean tides is presented the theory is based on laplace tide equations modified to include turbulence with constant eddy viscosity linearized bottom friction and oceanic loading and self gravitation variable bathymetry is also treated in harmonic terms and no flow boundary conditions are applied at continental coastlines the tide and boundary constraint equations are reduced to matrix form and solved by a weighted least squares procedure five zonal luni solar tides ranging in period from 14 days to 18 6 yr are investigated using the theory such tides have typically been difficult to compute using traditional numerical approaches the polar motion and changes in the length of day induced by these long period tides are calculated tidal solutions are compared extensively with results from other tidal theories and from recent satellite and sea level observations the greatest limitation to accurate prediction of zonal tides for any theory appears to be the marginal failure of all tide theories to conserve mass globally the use of additional mass constraints may be warranted

geochronological constraints on the tectonic evolution of a late archaean greenstone belt wabigoon subprovince northwest ontario canada abstract u pb isotopic age analyses have been carried out on zircon and titanite from rocks near the contact between the kakagi lake savant lake volcanic belt ksvb within the wabigoon subprovince and the english river subprovince in northwest ontario canada two tonalite gneisses intruded by mafic dykes at tannis lake and caribou lake have minimum zircon ages of 3051 ma and 3075 ma respectively this contrasts with a 2775 1 ma age on zircon from a felsic tuff located within a lower predominantly mafic volcanic sequence in the interior of ksvb these data combined with previous studies indicate that ksvb is presently flanked by older sialic crust in the sioux lookout and kashaweogama lake areas lower mafic volcanic sequences are unconformably overlain by sedimentary units that are in sheared contact with overlying calc alkaline volcanic units titanite and zircon analyses from clasts within a basal conglomerate indicate a maximum age for deposition of 2698 4 ma this late age is confirmed by a 2703 2 ma zircon age for an unconformably underlying porphyry intrusion one clast gives a zircon age of 2903 16 ma suggesting that the sediments were at least partly derived from older material in the english river subprovince data from previous studies show that the structurally overlying calc alkaline volcanic sequences are at least 30 ma older than the sediments the absence of zircon inheritance in all but the youngest ksvb sequences as well as geological and geochemical arguments suggest that the greenstone belt evolved largely in an ensimatic environment in isolation from older sialic material the intervening oceanic crust must therefore have been consumed by subduction which led to arc magmatism and eventual collision between the arc ksvb and continental material english river subprovince the sediments unconformably overlying the lowermost mafic volcanic sequences were deposited in a partly subaerial continental environment since chemical and textural evidence suggests the lower mafic volcanic sequences were deposited in an oceanic environment they must have been obducted onto the edge of a continental block this was perhaps followed by nappe and thrust emplacement on top of the sediments of calc alkaline sequences derived from earlier arc magmatism continued compression resulted in isoclinal folding of the supracrustal sequences into their present vertical positions

carbon dioxide respiration in the deep vadose zone implications for groundwater age dating in the deep vadose zone at the dalmeny site subsurface gas samples were collected and analyzed for co2 and the 13c and 14c ratios of that co2 high concentrations of co2 depleted in 14c near the water table necessitate the use of an open system model of calcite dissolution to match observed dissolved inorganic carbon 14c ratios just below the water table groundwater age dating models assuming closed system calcite dissolution predict incorrect groundwater age dates at the dalmeny site these results and our field observations suggest that such errors may generally occur where deep vadose generation of nonmodern co2 is not accounted for in groundwater age dating exercises

observations of annual variations of the earth s gravitational field using satellite laser ranging and geophysical models we have analyzed 6 years of satellite laser ranging slr data to the lageos 1 2 satellites to determine the annual variation of a set of spherical harmonic coefficients of the earth s gravity field complete to degree and order 4 half wavelength resolution of 5000 km we have compared these results to a suite of geophysical models describing annual variations of the gravity field due to changes in the distribution of mass in the atmosphere in the ocean and continental hydrology soil moisture and snow we find that spherical harmonic coefficients derived from the satellite observations and the aggregate of these geophysical models agree to about 1 mm rms in geoid height and have degree correlations that generally exceed the 90 confidence limit we found that the slr data could distinguish between two different hydrologic models but were unable to distinguish between competing models of atmosphere and ocean mass variation probably due to the small magnitude of the differences in these models and the small total magnitude of the ocean signal at the long wavelengths that can be observed by the satellite data the satellite results should improve considerably in 2001 with the launch of the gravity recovery and climate experiment grace which will allow the determination of the time variations of the earth s gravity field with a spatial resolution of about 300 km

a joint analysis of gps displacement and grace geopotential data for simultaneous estimation of geocenter motion and gravitational field this work is funded by the university of newcastle to support nasa s grace and grace follow on projects as an international science team member to the missions and by australian research council dp170100224 as well as nasa support to j sauber as a science team member

inversion of earth s changing shape to weigh sea level in static equilibrium with surface mass redistribution 1 we develop a spectral inversion method for mass redistribution on the earth s surface given geodetic measurements of the solid earth s geometrical shape using the elastic load love numbers first spectral coefficients are geodetically estimated to some degree spatial inversion then finds the continental surface mass distribution that would force geographic variations in relative sea level such that it is self consistent with an equipotential top surface and the deformed ocean bottom surface and such that the total ocean plus continental mass load has the same estimated spectral coefficients applying this theory we calculate the contribution of seasonal interhemispheric degree 1 mass transfer to variation in global mean sea level and nonsteric static ocean topography using published gps results for seasonal degree 1 surface loading from the global igs network our inversion yields ocean continent mass exchange with annual amplitude 2 92 0 14 1015 kg and maximum ocean mass on 25 august 3 days after correction for the annual variation in global mean vertical deformation of the ocean floor 0 4 mm amplitude we find geocentric sea level has an amplitude of 7 6 0 4 mm consistent with topex poseidon results minus steric effects the seasonal variation in sea level at a point strongly depends on location ranging from 3 to 19 mm the largest being around antarctica in mid august seasonal gradients in static topography have amplitudes of up to 10 mm over 5000 km which may be misinterpreted as dynamic topography peak continental loads occur at high latitudes in late winter at the water equivalent level of 100 200 mm

evolution of chemical and isotopic composition of inorganic carbon in a complex semi arid zone environment consequences for groundwater dating using radiocarbon abstract estimating groundwater age is important for any groundwater resource assessment and radiocarbon 14 c dating of dissolved inorganic carbon dic can provide this information in semi arid zone i e water limited environments there are a multitude of reasons why 14 c dating of groundwater and traditional correction models may not be directly transferable some include 1 the complex hydrological responses of these systems that lead to a mixture of different ages in the aquifer s 2 the varied sources origins and ages of organic matter in the unsaturated zone and 3 high evaporation rates these all influence the evolution of dic and are not easily accounted for in traditional correction models in this study we determined carbon isotope data for dic in water carbonate minerals in the sediments sediment organic matter soil gas co 2 from the unsaturated zone and vegetation samples the samples were collected after an extended drought and again after a flood event to capture the evolution of dic after varying hydrological regimes a graphical method han et al 2012 was applied for interpretation of the carbon geochemical and isotopic data simple forward mass balance modelling was carried out on key geochemical processes involving carbon and agreed well with observed data high values of dic and 13 c dic and low 14 c dic could not be explained by a simple carbonate mineral co 2 gas dissolution process instead it is suggested that during extended drought water sediment interaction leads to ion exchange processes within the top 10 20 m of the aquifer which promotes greater calcite dissolution in saline groundwater this process was found to contribute more than half of the dic which is from a mostly dead carbon source dic is also influenced by carbon exchange between dic in water and carbonate minerals found in the top 2 m of the unsaturated zone this process occurs because of repeated dissolution precipitation of carbonate that is dependent on the water salinity driven by drought and periodic flooding conditions this study shows that although 14 c cannot be directly applied as a dating tool in some circumstances carbon geochemical isotopic data can be useful in hydrological investigations related to identifying groundwater sources mixing relations recharge processes geochemical evolution and interaction with surface water

archean oceanic flake tectonics assuming that the archean mantle was hotter and the oceanic crust thicker than at present we estimate that the archean oceanic lithosphere had a sandwich rheology with the lower crust behaving as a soft ductile layer accordingly the archean oceanic lithosphere had a rheological structure similar to present day continental lithosphere but unlike present day oceanic lithosphere the thickness of the ductile layer is a decreasing function of age while its strength is an increasing function of age the buoyancy problem in archean subduction could be overcome by delamination of oceanic upper crust but mass balance calculation indicates that most archean oceanic crust must have been recycled where the right dynamic conditions existed for delamination oceanic flake tectonics may have been an important process leading to the preservation of oceanic upper crust in greenstone belts that are characteristic of archean terrains

stratigraphic and sedimentological evidence bearing on structural repetition in early archean rocks of the barberton greenstone belt south africa abstract the 3 5 3 3 ga old swaziland supergroup in the barberton greenstone belt south africa includes a lower predominantly volcanic unit the onverwacht group and an upper largely sedimentary section the fig tree and moodies groups although viljoen and viljoen concluded that the onverwacht group exceeds 15 km in stratigraphic thicknesses more recent workers have suggested that it represents a much thinner section of rocks repeated by folding and faulting our mapping indicates that the upper half of the group includes at least 8 km of unrepeated stratigraphic section inferences of structural repetition have arisen in part because a major shear zone is present in the upper half of the onverwacht group on the west limb of the onverwacht anticline shearing and the overturning of large blocks of the igneous sequence have combined with the later intrusion of felsic magma to produce a generally stratiform highly complex zone of deformation up to 2 km wide the displacement across the zone is unknown but the presence of unfaulted sections of this part of the stratigraphic sequence indicates that the gross stratigraphic arrangement of units within the group has not been significantly altered structures previously mapped as major fold hinges within the upper part of the onverwacht group can be shown to have formed by local deformation and reflect neither large scale folding nor structural repetition of the rocks several kilometers higher in the section rocks of the uppermost onverwacht and fig tree groups are stacked and repeated in a series of thrust nappes individual nappes extend for up to 15 km along strike and include as much as 900 m of allochthonous volcanic and sedimentary rocks they were apparently emplaced by faulting or gravity sliding at or near the earth s surface their formation involved the movement of sheets made largely up of sedimentary rocks along shear surfaces within underlying much weaker serpentinized ultramafic komatiites locally the sheets were deformed to form fold nappes the lower limbs of the fold nappes commonly show extreme attenuation and brittle deformation whereas the upper limbs are largely intact the thrust faults are the loci of small hypabyssal igneous bodies that appear to be co magmatic with a suite of upper fig tree volcanic rocks this style of faulting has not affected rocks of the overlying moodies group although estimates of the timing of deformation are as yet imprecise these features suggest that it occurred during a late fig tree phase of tectonism and volcanism

formation of an archaean continent about 30 of the earth is covered by continents but only about 10 small kernels of these continentsae known as archaean cratonsae are continental fragments formed before 2 5 gyr ago the kaapvaal craton of south africa which formed and stabilized between 3 7 and 2 7 gyr ago is one of the oldest reasonably sized examples of these continental fragments it consists of a mosaic of subdomains that have been welded together by processes similar to those of modern day plate tectonics the earliest subdomains may have owed their origin to the onset of efficient recycling from the earth s hydrosphere into the mantle

secular variation in greenstone sequence development emphasizing superior province canada abstract evidence from the superior province of the canadian shield suggests the existence of several distinct lithostratigraphic associations in greenstone belts 1 quartz arenite and carbonate bearing sequences 2 mafic ultramafic volcanic sequences 3 mafic to felsic volcanic cycles and 4 timiskaming type sequences of fluviatile sediments and calc alkaline to alkaline volcanics recently recognized quartz arenite bearing sequences in the sachigo and wabigoon subprovinces are from base to top quartz arenite stromatolite bearing carbonate oxide facies iron formation and komatiite or tholeiite primary structures in the quartz arenites indicate shallow water deposition and represent mature sedimentation granitoid provenance of these sediments is postulated based upon petrography of coarse arenites and clasts of associated conglomerates the few dated superior province quartz arenite bearing sequences are 2 85 ga the shallow water origin of the primary structures and biota and the areal extent of the quartz arenite and carbonate sequences invite comparison with platform sediments at passive margins platform sequences unconformably overlie 3 ga granitoid rocks and older mafic volcanics where original lower contacts are preserved in two localities mafic volcanic sequences contain sheet flows iron formations and deep water argillites based on physical volcanology and sedimentology these sequences are compared to modern deep water mafic plain and hawaiian volcanism they generally underlie mafic to felsic volcanic cycles and overlie platform sequences mafic sequences are 2740 2700 ma in age mafic to felsic volcanic cycles consist of deep water tholeiitic flows overlain by shallow water to subaerial intermediate to felsic pyroclastics and flows the facies style of volcanism petrography and geochemistry of the mafic to felsic cycles most closely resemble the characteristics of crust in continental magmatic arc systems this type of lithostratigraphic association varies in age from 2775 to 2700 ma in the superior province with minor exceptions timiskaming type sequences consist of fluviatile conglomerate immature arenites and wackes with subaqueous to subaerial volcanics of variable chemistry longitudinal and lateral variation within fault bounded basins is extreme and the sequences have generally been affected by only late stages of deformation the combination of rock types facies distribution the fault bounded nature of the repositories and the locus of sedimentation along zones of transcurrent displacement suggest timiskaming sequences are best compared with modern pull apart basins superior province timiskaming sequences are within the superior province platform sequences are the earliest postorogenic lithostratigraphic unit in greenstone belts followed by mafic plain sequences arc volcanics and pull apart basins we suggest that platform sequences based upon limited evidence are preceded by an orogeny and that pull apart basins represent a subsequent orogeny the lithostratigraphic units above have distinct metallogenic associations 1 platform sequences based upon compilation of several shields may contain detrital au and u and oxide facies iron formations associated felsic volcanics contain no recognized volcanogenic cu zn deposits in the superior province the following metallogenic associations are noted 2 mafic plain sequences contain komatiite flow related ni deposits cu ni and platinum group deposits are associated with flows and coeval intrusions 3 arc volcanic sequences contain volcanogenic cu zn sulphide deposits and scarce deposits of porphyry type cu mo and 4 timiskaming sequences and related plutonism are related to lode au

estimating geocenter variations from a combination of grace and ocean model output 1 in this study we estimate a time series of geocenter anomalies from a combination of data from the gravityrecoveryandclimateexperiment grace satellitemissionandthe outputfromoceanmodels amatrixequationisderivedrelating totalgeocentervariations to the grace coefficients of degrees two and higher and to the oceanic component of the degree one coefficients we estimate the oceanic component from two state of the art ocean models results are compared to independent estimates of geocenter derived from other satellite data such as satellite laser ranging and gps finally we compute degree one coefficients that are consistent with the processing applied to the grace level 2 gravity field coefficients the estimated degree one coefficients can be used to improve estimates of mass variability from grace which alone cannot provide them directly

single zircon age constraints on the tectonic juxtaposition of the archean abitibi greenstone belt and pontiac subprovince quebec canada abstract zircons from metasediments and granitoids in the high grade lacorne block within the low grade archean abitibi greenstone belt have been dated by the single zircon pb evaporation technique yielding 207pb 206pb minimum ages detrital zircons in the mature clastic metasediments of the lacorne block display a range of ages from 2691 8 ma to 3042 6 ma the younger zircon ages 2691 8 2695 4 2715 16 and 2719 4 ma thus impose an upper limit for deposition and indicate that the high grade lacorne block is not basement to the abitibi supracrustal sequence 2747 2680 ma existence of abundant 69 older detrital zircons 2750 ma suggests in turn that the abitibi supracrustal rocks are not the source of the lacorne sediments two generations of granitoids occur in the lacorne block an early monzodiorite monzonite granodiorite syenite series mmgs 2671 4 to 2675 24 ma and a younger s type garnet muscovite granite series gmg 2630 20 to 2655 8 ma this contrasts with granitoid magmatism in the abitibi greenstone belt which ended at 2675 ma the pontiac subprovince to the south of the abitibi greenstone belt shares all of the above features of the lacorne block including detrital zircon ages as well as the composition and timing of granitoid magmatism this is interpreted to indicate that the lacorne block was originally part of the same tectonic terrane as the pontiac subprovince after development of the mmgs magmatism 21670 2680 ma the pontiac subprovince locally underthrust the abitibi greenstone belt and crustal thickening promoted partial melting of underthrust pontiac metasediments to form the 2644 13 ma s type granites later differential uplift exposed the lacorne block as a high grade tectonic window in the abitibi greenstone belt

u pb zircon geochronology in the southwestern abitibi greenstone belt superior province the abitibi belt is the largest continuous greenstone belt in the superior province of the canadian shield it comprises several composite komatiitic tholeiitic calc alkalic and sedimentary sequences that are folded transected by major faults and intruded by various generations of plutonic rocks precise u pb geochronology has been carried out in the belt for the past decade to solve chronostratigraphic and metallogenetic problems this paper presents new zircon ages and reassesses previously published ones now refined by the addition of abraded and concordant zircon analyses volcanic and subvolcanic units of the timmins area yield the following ages 2727 1 5 ma for a tuff of the upper deloro formation 2703 1 5 ma for a tuff of the upper tisdale formation and 2698 4 ma for the krist fragmental assigned to the top of the tisdale formation the age of a dunite intrusive into the upper deloro formation is revised at 2707 3 ma whereas the aquarius diorite east of timmins yields a poorly define

effects of atmospheric pressure loading and seven parameter transformations on estimates of geocenter motion and station heights from space geodetic observations 1 variations in fluid loads such as the oceans and the atmosphere deform the surface of the earth the accuracy of station coordinates in particular heights that can be estimated depends on how well one can separate these surface deformations from the associated translational motion between the center of mass of the solid earth and the total earth cm we applied simulated atmospheric pressure loading effects to the coordinates of sites in the cm frame to explore to what level of accuracy both geocenter motion and accurate station coordinates can actually be recovered from geodetic analyses we found that standard seven parameter transformations three rotations three translations scale generally recover about 80 of the geocenter motion however the inclusion of a scale factor permits the aliasing of surface loading deformation introducing scale errors of up to 0 3 ppb and daily height errors as large as 4 mm this limits the geophysical studies that can be performed accurately using the results of geodetic analyses where the magnitudes of the signals are small e g tectonic movement of tide gauges uplift rates for interpreting glacial isostatic adjustment the quality of the geodetic results is extremely sensitive to the number and distribution of sites used to estimate the transformations and becomes worse when regional rather than global sets of sites are used if the scale factor parameter is omitted then the amount of aliasing of surface loading effects is reduced considerably and more accurate site velocities and geocenter motion estimates are achieved

passive ocean radial basis function approach to improve temporal gravity recovery from grace observations we present a state of the art approach of passive ocean modified radial basis functions mrbfs that improves the recovery of time variable gravity fields from grace as is well known spherical harmonics shs which are commonly used to recover gravity fields are orthogonal basis functions with global coverage however the chosen sh truncation involves a global compromise between data coverage and obtainable resolution and strong localized signals may not be fully captured radial basis functions rbfs provide another representation which has been proposed in earlier works to be better suited to retrieve regional gravity signals in this paper we propose a mrbf approach by embedding the known coastal geometries in the rbf parameterization and imposing global mass conservation and equilibrium behavior of the oceans our hypothesis is that with this physically justified constraint the grace derived gravity signals can be more realistically partitioned into the land and ocean contributions along the coastlines we test this new technique to invert monthly gravity fields from grace level 1b observations covering 2005 2010 for which the numerical results indicate that 1 mrbf based solutions reduce the number of parameters by approximately 10 and allow for more flexible regularization when compared to ordinary rbf solutions and 2 the mrbf derived mass flux is better confined along coastal areas the latter is particularly tested in the southern greenland and our results indicate that the trend of mass loss from the mrbf solutions is approximately 11 larger than that from the sh solutions and approximately 4 6 larger than that of rbf solutions

effect of annual signals on geodetic velocity 1 our analysis of global positioning system gps site coordinates in a global reference frame shows annual variation with typical amplitudes of 2 mm for horizontal and 4 mm for vertical with some sites at twice these amplitudes power spectrum analysis confirms that gps time series also contain significant power at annual harmonic frequencies with spectral indices 1 2 which indicates the presence of repeating signals van dam et al 2001 showed that a major annual component is induced by hydrological and atmospheric loading unless accounted for we show that annual signals can significantly bias estimation of site velocities intended for high accuracy purposes such as plate tectonics and reference frames for such applications annual and semiannual sinusoidal signals should be estimated simultaneously with site velocity and initial position we have developed a model to calculate the level of bias in published velocities that do not account for annual signals simultaneous estimation might not be necessary beyond 4 5 years as the velocity bias rapidly becomes negligible minimum velocity bias is theoretically predicted at integer plus half years as confirmed by tests with real data below 2 5 years the velocity bias can become unacceptably large and simultaneous estimation does not necessarily improve velocity estimates which rapidly become unstable due to correlated parameters we recommend that 2 5 years be adopted as a standard minimum data span for velocity solutions intended for tectonic interpretation or reference frame production and that we be skeptical of geophysical interpretations of velocities derived using shorter data spans

mafic and ultramafic amphibolites from the northwestern pontiac subprovince chemical characterization and implications for tectonic setting in the northwestern pontiac subprovince metavolcanic rocks are exposed within a metagraywacke sequence that is intruded by metamorphosed mafic dykes the metavolcanics are al undepleted komatiites la sm n 0 3 tb yb n 0 9 and tholeiitic fe basalts la sm n 0 8 and tb yb n 0 8 the nearly flat chondrite normalized distributions of high field strength elements hfse ti and p the constant zr y nb th ti zr and ti p ratios and the lack of depletion of hfse relative to rare earth elements ree in both ultramafic and mafic metavolcanics imply that crustal assimilation and magma mixing with crustal melts were not significant during differentiation and argue against the presence of subduction related magmatic components contemporaneous volcanism and sedimentation in the northwestern pontiac subprovince are unlikely the metavolcanics do not show any evidence of crustal contamination and likely represent a structurally emplaced disrupted assemblage chemically similar to early volcanics o

the quest for a consistent signal in ground and grace gravity time series recent studies show that terrestrial and space based observations of gravity agree overeurope in this paper we compare time series of terrestrial gravity including thecontribution due to surface displacement as measured by superconducting gravimeters sgs space based observations from grace and predicted changes in gravity derived fromtwo global hydrological models at 10 sg stations in central europe despite the fact that allobservations and models observe a maximum in the same season due to water storagechanges there is little agreement the sg time series even when they are separated bydistances smaller than the spatial resolution of grace we also demonstrate that grace andthe sg observations and the water storage models do not display significant correlation atseasonal periods nor at inter annual periods these findings are consistent with the fact thatthe sgs are sensitive primarily to mass changes in the few hundred meters surrounding thestation even if the hydrological models were perfect we show that we could not correct thesgs for these local effects that would allow comparisons with grace

kalref a kalman filter and time series approach to the international terrestrial reference frame realization the current international terrestrial reference frame is based on a piecewise linear site motion model and realized by reference epoch coordinates and velocities for a global set of stations although linear motions due to tectonic plates and glacial isostatic adjustment dominate geodetic signals at today s millimeter precisions nonlinear motions due to earthquakes volcanic activities ice mass losses sea level rise hydrological changes and other processes become significant monitoring these sometimes rapid changes desires consistent and precise realization of the terrestrial reference frame trf quasi instantaneously here we use a kalman filter and smoother approach to combine time series from four space geodetic techniques to realize an experimental trf through weekly time series of geocentric coordinates in addition to secular periodic and stochastic components for station coordinates the kalman filter state variables also include daily earth orientation parameters and transformation parameters from input data frames to the combined trf local tie measurements among colocated stations are used at their known or nominal epochs of observation with comotion constraints applied to almost all colocated stations the filter smoother approach unifies different geodetic time series in a single geocentric frame fragmented and multitechnique tracking records at colocation sites are bridged together to form longer and coherent motion time series while the time series approach to trf reflects the reality of a changing earth more closely than the linear approximation model the filter smoother is computationally powerful and flexible to facilitate incorporation of other data types and more advanced characterization of stochastic behavior of geodetic time series

land water contribution to sea level from grace and jason 1measurements 1 we investigate the effect of water storage changes in the world s major hydrological catchment basins on global and regional sea level change at seasonal and long term time scales in a joint inversion using grace and jason 1 data we estimate the time dependent sea level contributions of 124 spatial patterns fingerprints including glacier and ice sheet melting thermal expansion changes in the terrestrial hydrological cycle and glacial isostatic adjustment particularly for hydrological storage changes we derive fingerprints of the 33 world s largest catchment basins assuming mass distributions derived from the leading eofs of total water storage in the watergap global hydrological model wghm from our inversion we estimate a contribution of terrestrial hydrological cycle changes to global mean sea level of 0 20 0 04 mm yr with an annual amplitude of 6 6 0 5 mm for august 2002 to july 2009 using only grace data in the inversion and comparing to hydrological changes derived from grace data directly using a basin averaging method shows a good agreement on a global scale but considerable differences are found for individual catchment basins up to 180 hydrological storage change estimates in 33 basins from the grace jason fingerprint inversion indicate a trend 46 smaller and an annual amplitude 43 bigger compared to wghm derived storage changes mapping the hydrological trends to regional sea level reveals the strongest sea level rise along the coastlines of south america max 0 9 mm yr and west africa max 0 4 mm yr whereas around alaska and australia we find the hydrological component of sea level falling min 2 0 mm yr and 0 9 mm yr

evolution of dissolved inorganic carbon in groundwater recharged by cyclones and groundwater age estimations using the 14c statistical approach abstract the canning basin is the largest sedimentary basin in western australia and is located in one of the most cyclone prone regions of australia despite its importance as a future resource limited groundwater data is available for the basin the main aims of this paper are to provide a detailed understanding of the source of groundwater recharge the chemical evolution of dissolved inorganic carbon dic and provide groundwater age estimations using radiocarbon 14 c dic to do this we combine hydrochemical and isotopic techniques to investigate the type of precipitation that recharge the aquifer and identify the carbon processes influencing 14 c dic 13 c dic and dic this enables us to select an appropriate model for calculating radiocarbon ages in groundwater the aquifer was found to be recharged by precipitation originating from tropical cyclones imparting lower average 2 h and 18 o values in groundwater 56 9 and 7 87 respectively water recharges the soil zone rapidly after these events and the groundwater undergoes silicate mineral weathering and clay mineral transformation processes it was also found that partial carbonate dissolution processes occur within the saturated zone under closed system conditions additionally the processes could be lumped into a pseudo first order process and the age could be estimated using the 14 c statistical approach in the single sample based 14 c models 14 c 0 is the initial 14 c dic value used in the decay equation that considers only 14 c decay rate a major advantage of using the statistical approach is that both 14 c decay and geochemical processes that cause the decrease in 14 c dic are accounted for in the calculation the 14 c dic values of groundwater were found to increase from 89 pmc in the south east to around 16 pmc along the groundwater flow path towards the coast indicating ages ranging from modern to 5 3 ka a test of the sensitivity of this method showed that a 15 error could be found for the oldest water this error was low when compared to single sample based models this study not only provides the first groundwater age estimations for the canning basin but is the first groundwater dating study to test the sensitivity of the statistical approach and provide meaningful error calculations for groundwater dating

evolution of the south central part of the archean abitibi belt quebec part i stratigraphy and paleogeographic model the region comprises parts of the southern zone of the abitibi greenstone belt and of the bellecombe gneiss belt and the belleterre angliers greenstone belt the stratigraphic sequence of the abitibi belt consists of 1 a lower ultramafic division 2 a middle tholeiitic division and 3 an upper diverse division these divisions lap onto an older volcanic sequence to the north and west in the bellecombe belt sediments overlie the lower ultramafic division these sediments coarsen toward the abitibi belt and toward the stratigraphic top the volcanic rocks of the belleterre angliers belt overlie the sediments of the bellecombe belt five paleogeographic phases have been recognized during phase i a deep marine ultramafic lava plain covered the south part of the abitibi belt and the bellecombe belt faulting took place at the duparquet destor break during phase ii tholeiitic basalts formed a deep marine lava plain in the west of the abitibi belt whereas flows erupted mainly from central volcanic c

factors affecting carbon 14 activity of unsaturated zone co2 and implications for groundwater dating summary unsaturated zone processes may influence the carbon 14 14 c activity of infiltrating groundwater and thus introduce error in derived groundwater residence times however unsaturated zone 14 c activities are rarely measured and there is little understanding of how they may vary spatially in a groundwater basin in this study we measured 14 c activity in unsaturated zone gas at five sites with different watertable depths 8 2 31 5 m in the arid ti tree basin central australia we observed a relatively uniform decrease in 14 c activity of unsaturated zone gas with depth at most sites with variation in unsaturated zone depths leading to variation in 14 c activities directly above the watertable at each site ranging from 54 to 106 percent modern carbon pmc through modelling we show that the profiles are influenced by co 2 production at different depths from sources with different isotopic ratios including production of modern co 2 in the root zone and production of old co 2 above the watertable scenario modelling showed that these processes are independent of recharge when recharge is low 0 10 mm y 1 but that higher recharge rates 100 mm y 1 result in more advective transport of atmospheric co 2 to the watertable the variation in 14 c above the watertable was more sensitive to watertable depth and shallow and deep co 2 production rates these findings offer insight into how unsaturated zone 14 c activities may vary spatially and provide guidance as to when 14 c depletion in unsaturated zone co 2 may become important for groundwater dating particularly in arid settings

seasonal long term and short term deformation in the central range of taiwan induced by landslides seasonal movement of gps stations is often attributed to hydrological loading and other environmental factors for the first time we observe seasonal motion associated with slow moving landslides eight of 26 continuous gps cgps sites in the central range of taiwan show long term landslide induced motion at rates of 3 15 mm yr 20 60 of their tectonic interseismic velocities the directions of movements after heavy rains and in the wet season are consistent with the slope directions derived from a high resolution elevation model constructed by airborne lidar long term and seasonal interseismic motions are modulated by slow moving landslides seasonal motions of landslides at lushan show peak to peak amplitudes of 3 19 mm estimates of interseismic crustal strain can be biased if surface processes are not taken into account preliminary analyses indicate that rainfall and topography play strong roles in the occurrence of landslides discrimination between surface processes and motion that has a tectonic origin is the key to natural hazard assessments

chemistry of unsaturated zone gases sampled in open boreholes at the crest of yucca mountain nevada data and basic concepts of chemical and physical processes in the mountain boreholes open to the unsaturated zone at the crest of yucca mountain nevada were variously sampled for co2 including 13c and 14c ch4 n2 o2 ar cfc 11 cfc 12 and cfc 113 from 1986 to 1993 air enters the mountain in outcrops principally on the eastern slope is enriched in co2 by mixing with soil gas and is advected to the mountain crest where it returns to the atmosphere the cfc data indicate that travel times of the advecting gas in the shallow tiva canyon hydrogeologic unit are 5 years the 14c activities are postbomb to depths of 100 m indicating little retardation of 14co2 in the shallow flow systems the 14c activities from 168 to 404 m in the topopah spring hydrogeologic unit are 85 90 pmc at borehole usw uz6 the cfc data show that the drilling of usw uz6 in 1984 has altered the natural system by providing a conduit through the paintbrush nonwelded unit allowing flow from topopah spring outcrops in solitario canyon on the west to usw uz6 upward in the borehole through the paintbrush to the shallow tiva canyon flow systems and out of the mountain

present day secular variations in the low degree harmonics of the geopotential sensitivity analysis on spherically symmetric earth models 1 we predict present day rates of change of the long wavelength components of the earth s geopotential due to the late pleistocene glacial cycles hereinafter referred to as glacial isostatic adjustment or gia these predictions are generated using spherically symmetric self gravitating maxwell viscoelastic earth models previous studies have generally considered only zonal i e azimuthally independent harmonics or the so called coefficients we extend these efforts to focus on the nonzonal harmonics and explore the sensitivity of our predictions to changes in a variety of model inputs as an example we examine the influence on the gia predictions of ignoring rotational perturbations and assuming an elastically incompressible model and find that these assumptions can have a significant impact on the degree 2 order 1 coefficients while the other harmonics are generally affected by 10 though the gia predictions are generally insensitive to variations in lithospheric thickness and upper mantle viscosity reasonable variations in either lower mantle viscosity or the late pleistocene ice history will have a more significant effect mindful of upcoming dedicated gravity missions we show that predictions of the gia induced changes of the geoid can vary by at least 0 5 mm yr 1 over a plausible range of earth and ice models

changes in total ocean mass derived from grace gps and ocean modeling with weekly resolution 1 we derive changes in ocean bottom pressure obp and ocean mass by combining modeled ocean bottom pressure weekly grace derived models of gravity change and large scale deformation patterns sensed by a global network of gps stations in a joint least squares inversion the weekly combination allows a consistent estimation of geocenter motion loading mass harmonics up to degree 30 and a spatially uniform mass correction term which serves as a correction for forcing of the ocean model we provide maps and time series of ocean mass and bottom pressure variations furthermore we discuss the estimated geocenter motion and the estimated model correction our results indicate that the total ocean mass change is predominantly annual with a maximum amplitude corresponding to 7 4 mm in october which is in line with earlier work the mean ocean bottom pressure i e ocean plus atmospheric mass shows an annual amplitude of 8 7 mm and is shifted forward by about 1 5 months in addition the solution exhibits typical autocorrelation times of about 2 weeks a comparison with in situ bottom pressure time series in the southern indian ocean shows a good agreement with correlations of 0 7 0 8 based on these comparisons we see that our results monitor realistic submonthly variations which are strongest at high latitudes the addition of grace data in the inversion is found to improve these high latitude variations and enables better separability of the geocenter motion from other unknowns increasing the obp model error from 3 cm to 4 8 cm affects mainly the higher degree coefficients