contrasting nature of petroliferous mesozoic cenozoic basins in eastern and western china onshore petroliferous basins of mesozoic cenozoic age in china include two distinct geographic geotectonic groups eastern extensional rifted basins and western compressional orogenic basins eastern basins are faulted depressions and crustal sags that formed where incipient intracontinental rifting thinned the crust and developed tilted fault blocks and half grabens bounded by normal faults western basins are flexural downbows that were depressed under the tectonic load of adjacent thrust sheets associated with the folded mountain ranges of central asia source beds in both groups of basins are dominantly dark lacustrine mudstones of terrestrial facies associations and reservoirs are mainly fluviodeltaic sandstones hydrocarbon traps in the eastern basins include e tensional rollover anticlines compactional drape anticlines diapiric salt domes buried hill highs in the substratum and stratal pinch outs on the flanks of buried highs simple or faulted anticlinal traps are dominant in the western basins multiple reservoir horizons are characteristic of oil fields in both groups of basins orogenic compression which developed the western basins is attributed to the successive collision of microcontinents with the southern edge of the composite eurasian continental mass crustal extension which developed the eastern basins is attributed to incipient rifting within and behind magmatic arcs along the margin of the pacific ocean basin

iceberg calving flux and mass balance of the austfonna ice cap on nordaustlandet svalbard 1 satellite radar interferometry 60 mhz airborne ice penetrating radar data and visible band satellite imagery were used to calculate the velocity structure ice thickness and the changing ice marginal extent of austfonna 8000 km2 and 2500 km3 the largest ice cap in the eurasian arctic ice cap motion is generally less than about 10 m a 1 except where faster flowing curvilinear features with velocities of several tens to over 200 m a 1 are present most drainage basins of austfonna have undergone ice marginal retreat over the past few decades at an average of a few tens of meters per year integrating margin change around the whole ice cap gives a total area loss of about 10 km2 a 1 iceberg flux from the marine margins of austfonna is about 2 5 0 5 km3 a 1 water equivalent about 45 of the total calving flux from the whole svalbard archipelago when mass loss by iceberg production is taken into account the total mass balance of austfonna is negative by between about 2 5 and 4 5 km3 a 1 this iceberg flux represents about 33 5 of total annual mass loss from austfonna with the remainder lost through surface ablation iceberg flux should be included in calculations of the total mass balance of the many large arctic ice caps including those located in the russian and canadian arctic that end in tidewater the neglect of this term has led to underestimates of mass loss from these ice caps and thus to underestimates of the contribution of arctic ice caps to global sea level rise

analysis of three component data from iris ida stations in the ussr abstract this paper presents results of backazimuth incidence angle and phase identification studies based on the three component polarization of 0 to 5 hz seismic signals recorded at the iris ida stations within the ussr a data set was built from the analysis of three component 3 c recordings from seismic stations at arti aru garm gar kislovodsk kiv and obninsk obn for the month of march 1989 approximately 260 events were studied at stations aru kiv and obn teleseisms dominated the sample of recordings station gar however recorded a larger set of events that included a significant number of local and regional events except for station obn all of the iris ida stations are located near major geologic structural boundaries that are characterized by significant lateral variation in the deep velocity structure these stations near boundaries show system atic deviations in estimates of backazimuth and angle of incidence at station gar both of these measurements were influenced by the structure polarization characteristics of seismic phases were studied individually for each station at stations obn and kiv the initial teleseismic p wave was characterized for the most part by prograde elliptical motion at aru and gar the motion was rectilinear regional s phases from hindu kush earthquakes recorded at gar were dominated by transverse horizontally polarized motion sh at kiv and aru lg motion was predominantly in a near horizontal plane a phase identification study was performed using discriminant analysis based on polarization parameters and frequency content two discriminants linear combinations of polarization and frequency measurements were able to separate arrival data into one of three groups of phases teleseismic p regional p and regional s at gar the first discriminant is correlated with polarization and separates arrivals with p wave characteristics from arrivals with s wave characteristics the second discriminant accentuates the differences in the frequency content of the arrivals and provides a good separation between regional and teleseismic phases backazimuth estimates were made for local regional and teleseismic events at gar and for teleseismic events at aru kiv and obn the unique structural environment of each station required that custom processing parameters be developed for each station the assumed particle motion rectilinear or elliptical used in the polarization computation the window length and the frequency band characteristic for each station were determinant factors backazimuth estimates within 25 of the theoretical value were obtained for about 70 of the events at most of the stations at gar systematic backazimuth errors caused by large lateral velocity discontinuities degraded the results corrections could be made to reduce these errors

secular gravity variation at svalbard norway from ground observations and grace satellite data the svalbard archipelago norway is affected by both the present day ice melting pdim and glacial isostatic adjustment gia subsequent to the last pleistocene deglaciation the induced deformation of the earth is observed by using different techniques at the geodetic observatory in ny alesund precise positioning measurements have been collected since 1991 a superconducting gravimeter sg has been installed in 1999 and six campaigns of absolute gravity ag measurements were performed between 1998 and 2007 moreover the gravity recovery and climate experiment grace satellite mission provides the time variation of the earth gravity field since 2002 the goal of this paper is to estimate the present rate of ice melting by combining geodetic observations of the gravity variation and uplift rate with geophysical modelling of both the gia and earth s response to the pdim we estimate the secular gravity variation by superimposing the sg series with the six ag measurements we collect published estimates of the vertical velocity based on gps and vlbi data we analyse the grace solutions provided by three groups csr gfz grgs the crux of the problem lies in the separation of the contributions from the gia and pdim to the earth s deformation to account for the gia we compute the response of viscoelastic earth models having different radial structures of mantle viscosity to the deglaciation histories included in the models ice 3g or ice 5g to account for the effect of pdim we compute the deformation of an elastic earth model for six models of ice melting extension and rates errors in the gravity variation and vertical velocity are estimated by taking into account the measurement uncertainties and the variability of the grace solutions and gia and pdim models the ground observations agree with models that involve a current ice loss of 25 km3 water equivalent yr 1 over svalbard whereas the space observations give a value in the interval 5 18 km3 water equivalent yr 1 a better modelling of the pdim which would include the precise topography of the glaciers and altitude dependency of ice melting is necessary to decrease the discrepancy between the two estimates

surface deformation induced by present day ice melting in svalbard summary the vertical movement of the earth s surface is the result of a number of internal processes in the solid earth tidal forces and mass redistribution in the atmosphere oceans terrestrial hydrosphere and cryosphere close to ice sheets and glaciers the changes in the ice loads can induce large vertical motions at intraseasonal to secular timescales the global positioning system gps and very long baseline interferometry vlbi antennas in ny a u lesund svalbard that started observations in 1991 and 1995 respectively observe vertical uplift rates on the order of 8 2m m yr 1 which are considerably larger than those predicted by postglacial rebound pgr models order 2 mm yr 1 the observations also indicate increased uplift rates starting some time in 2000 a local gps campaign network that has been reoccupied annually since 1998 reveals a tilting away from the neighbouring glaciers the svalbard glaciers have been undergoing melting and retreat during the last century with increased melting since about 2000 we compared the observed vertical motion to the motion predicted by loading models using a detailed ice model with annual time resolution as forcing the model predictions correlate well with the observations both with respect to the interannual variations and the spatial pattern of long term trends the regression coefficients for predicted and observed interannual variations in height is 1 08 0 38 whereas the regression coefficient for the predicted and observed spatial pattern turns out to be 1 26 0 42 estimates of the predicted secular trend in height due to pgr and present day melting are on the order of 4 8 0 3 mm yr 1 and thus smaller than the observed secular trend in height this discrepancy between predictions and observations is likely caused by the sum of errors in the secular rates determined from observations due to technique dependent large scale offsets and incomplete or erroneous models unaccounted tectonic vertical motion errors in the ice load history scale errors in the viscoelastic pgr models and the elastic models for present day melting

exhumational history of the north central pamir 1 the pamir plateau forms a prominent tectonic salient along the western end of the tibet tarim margin despite its tectonic significance relatively little is known about the timing of major cenozoic tectonic events in the pamir here we present new apatite and zircon u th he ages bulk rock geochemistry and al in hornblende barometry results from the karakul graben a prominent north south oriented rift basin located 50 km south of the main pamir thrust although cooling ages do not record the onset of extension graben bounding normal faults provide exposures of otherwise slowly eroding rocks which record two cenozoic thermal events existing geochronology and new results suggest that granitic rocks in the karakul region were shallowly emplaced cooled very quickly through 300 c and have experienced less than 10 km of exhumation since the late triassic a long period of relatively slow exhumation throughout much of the late mesozoic and cenozoic was punctuated by two periods of accelerated exhumation during the middle eocene 50 40 ma and early miocene 25 16 ma we interpret the first period of accelerated exhumation as a result of tectonic uplift and subsequent erosion due to the northward propagation of the india asia collision we attribute the second period of rapid exhumation to a renewed phase of tectonism and plateau uplift in the pamir perhaps related to a break off event along the down going indian plate at 25 ma or to the onset of slip along the nascent karakoram fault

basin evolution within and adjacent to the tien shan range nw china two late palaeozoic collisions produced the ancestral tien shan range extension following the younger collision preceded a phase of thermal subsidence associated with fluvial and lacustrine sedimentation throughout the jurassic cretaceous and early tertiary this thermal subsidence was interrupted by renewed movement on palaeozoic reverse faults caused by the mesozoic collisions at the southern margin of asia the india asia collision in the early tertiary has produced widespread thrusting in the tien shan which in turn is responsible for the formation of active foreland basins at the southern and northern margins of the range and similar basins within the range itself this compression produced uplift and relief and consequent erosion gave rise to alluvial fans braidplains and ephemeral lakes in an extremely arid environment

rock assemblages in central asia and the evolution of the southern asian margin by looking in detail at the rock record in central asia it is possible to map rock assemblages that are diagnostic of particular plate settings simplest of the assemblages include the rocks of the tadjik depression where mesozoic and paleogene sediments record the development of a south facing passive continental margin analysis of igneous activity in central asia and of the timing of deformation of these miogeoclinal rocks indicates that the paleotethyan ocean to the south was in the mesozoic subducting to the south beneath a migratory arc consisting of parts of iran afghanistan and the pamir only in the late tertiary does the tadjik depression develop a peripheral foreland assemblage which indicates any deformation of the miogeocline this presumably occurred as a result of the closing of the paleotethyan ocean and accretion of this portion of the arc to the southern margin of asia it appears unlikely that the depression passive margin sequence developed in a normal rift margin setting analysis of assemblages in the hercynian orogen tien shan to the north indicates that unlike the uralian section of the orogen the deformation here occurred due to the closure of a marginal basin and overthrusting of its basement rocks over a south facing arc thus considering depression basement composition it appears that the passive margin assemblage is superimposed over either a late paleozoic forearc or paleozoic ocean floor paleozoic rocks exposed north of the herat suture in afghanistan may require the forearc basement interpretation noting that the geometry of subduction and the timing of paleotethyan suturing seem to have varied along strike in the orogen a more complicated model of tectonic accretion is required

deglacial land emergence and lateral upper mantle heterogeneity in the svalbard archipelago i first results for simple load models summary the glacial isostatic adjustment following the removal of the pleistocene ice sheets furnishes basic information on the thickness of the earth s lithosphere and the viscosity of the subjacent mantle paper i is concerned with an elementary interpretation of the post glacial land emergence observed at a restricted set of six locations in the svalbard archipelago the interpretation is based on a three layer incompressible maxwell viscoelastic earth model which is forced by a time dependent load distribution simulating the deglaciation history of the svalbard archipelago and the barents sea in view of inconclusive geomorphological evidence suggesting either total or partial glaciation of the area at glacial maximum two simple load models barents t1 and barents p1 are considered in the first instance a comparison between the calculated and observed values of land emergence suggests increases in lithosphere thickness and asthenosphere viscosity with increasing distance of the location from the continental margin the trends are qualitatively insensitive to the load model load thickness or load cross section used for load model barents t1 with parabolic cross section an initial load thickness of 1 50 km and a relaxed fitting criterion the lateral variations are only weak if a more restrictive fitting criterion is employed the variations become more prominent and suggest increasing values of lithosphere thickness from below 80 km to above 140 km and of asthenosphere viscosity from below 3 1018 pa s to above 2 1019 pa s over a distance of about 300 km in paper ii kaufmann wolf 1995 a high resolution load model and an extended set of land emergence observations are used to study further the possibility of resolving lateral heterogeneity in the upper mantle below the svalbard archipelago

kinematics of the pamir and hindu kush regions from gps geodesy 1 gps velocities measured in the pamir and surrounding regions show a total of 30 mm yr of northward relative motion between stable pakistan and eurasia the convergence budget is partitioned into 10 15 mm yr of localized shortening across the trans alai thrust which bounds the pamir on the north consistent with southward subduction of intact lithosphere another 10 15 mm yr of shortening is distributed across the chitral himalaya and hindu kush suggesting that hindu kush seismicity might be related to northward subduction of indian lithosphere modest shortening at 5 mm yr occurs north of the trans alai thrust across the south tien shan and between the ferghana valley and eurasia negligible north south shortening occurs within the high pamir but as much as 5 mm yr and perhaps 10 mm yr of east west extension occurs within this region this extension is matched by a comparable amount of east west shortening in the tajik depression the localization of shortening to the margins of the pamir combined with observations of distributed internal extension implies that the east west vertically averaged horizontal compressive normal stress is smaller than the north south compressive stress

the biogeochemistry of mercury at the sediment water interface in the thau lagoon 2 evaluation of mercury methylation potential in both surface sediment and the water column abstract methylation rates of mercury have been determined in both surface sediments and the water column of a shallow coastal lagoon thau france using in situ incubation experiments the experiments were conducted in order to evidence and evaluate the significance of such pathways on the fate of methylmercury mehg as influenced by both benthic and pelagic dynamics isotopically labelled hg species have been used as chemical tracers allowing the direct determination of specific methylation and demethylation yields each experimental method cores experiments and water experiments has been carefully evaluated in terms of sensitivity and reproducibility of the transformation rates and has been demonstrated as a powerful method to investigate transformation processes although mercury methylation in surface sediments is a major process significant mehg formation in the water column has been measured for the first time in a coastal environment in spring conditions methylation yields are found to be higher in the water column 6 3 than in sediments 0 8 1 3 area integrated rates for the experimental site demonstrate however that mehg is mostly produced in surface sediments with a formation rate of 12 nmol m 2 d 1 compared to 1 8 nmol m 2 d 1 in the water column biological characteristics of the incubated samples indicate that sediment and plankton microorganisms are involved in hg methylation which is thus directly associated to the pelagic benthic turnover occurring in the lagoon

vertical land motion from present day deglaciation in the wider arctic vertical land motion vlm from past and ongoing glacial changes can amplify or mitigate ongoing relative sea level change we present a high resolution vlm model for the wider arctic that include

atmospheric effects and spurious signals in gps analyses improvements in the analyses of global positioning system gps obser vations yield resolvable mm to sub mm di erences in coordinate estimates thus provid ing su cient resolution to distinguish subtle di erences in analysis methodologies here we investigate the e ects on site coordinates of using di erent approaches to modelling atmospheric loading deformation atml and handling of tropospheric delays the rig orous approach of using the time varying vmf1 mapping function yields solutions with lower noise at a range of frequencies compared with solutions generated using empiri cal mapping functions this is particularly evident when atml is accounted for some improvement also arises from using improved a priori zenith hydrostatic delays zhd with the combined e ect being site speci c importantly inadequacies in both mapping functions and a priori zhds not only introduce time correlated noise but signi cant pe riodic terms at solar annual and semi annual periods we nd no signi cant di erence between solutions where non tidal atml is applied at the observation level rather than as a daily averaged value but failing to model diurnal and semi diurnal tidal atml at the observation level can introduce anomalous propagated signals with periods that closely match the gps draconitic annual 351 4 d and semi annual period 175 7 d ex acerbated by not xing ambiguities these signals are evident in both stacked and sin gle site power spectra with each tide contributing roughly equally to the dominant semi annual peak the amplitude of the propagated signal reaches a maximum of 0 8 mm with a clear latitudinal dependence that is not correlated directly with locations of maximum tidal amplitude this is the first evidence of aliased signals being produced from tidal atml deformations

surge type glaciers in the russian high arctic identified from digital satellite imagery landsat digital imagery was used to search the island archipelagos of franz josef land severnaya zemlya and novaya zemlya russian high arctic for the presence of looped moraines characteristic of past glacier surges the imagery provides almost complete summer time coverage of the 60000 km 2 of ice in these islands very few surge type glaciers are identified none in franz josef land three in novaya zemlya and two on severnaya zemlya this contrasts greatly with svalbard ice covered area 36 600 km 2 to the west where 36 of glaciers and ice cap drainage basins are inferred to surge the strong climatic gradient across the eurasian high arctic with decreasing temperature and moisture eastward may provide a gross control on this pattern through colder glacier thermal structure limiting basal drainage on the thinner ice masses in particular

seismic domains within the gissar kokshal seismic zone soviet central asia by evaluating seismological data from the belt of shallow intraplate seismicity known as the gissar kokshal seismic zone in soviet central asia in conjunction with recent data on the shallow crustal structure and longer term geologic deformation we show that certain size classes of earthquakes are characteristic of adjacent and in some places overlapping geologic tectonic settings we call these settings seismic domains they are both geologically and seismologically distinct i e they contain different rocks and structures and have different frequency magnitude relationships for example in terms of number of events gissar kokshal seismicity is dominated by the microearthquakes that have occurred within the sedimentary rocks of the vakhsh fold thrust belt these are all shallow and have occurred mostly within the frontal portions of the thrust sheets more rarely moderate size m 5 5 earthquakes have ruptured the thrust ramps on the other hand the major strain release in this region has accompanied the large 5 5 m 8 1 shallow earthquakes on basement faults in the southern gissar range adjacent to the fold thrust belt within these ranges there is relatively little microearthquake activity that dichotomy indicates that a significantly different seismic hazard is associated with each of these areas but the seismological distinction is obscured along the front of the fold thrust belt where the domain of small shocks in the sedimentary rocks overlaps the domain of large earthquakes on basement faults to explain the localization of the large basement events along the southern flank of the fold thrust belt adjacent to the fold thrust belt we hypothesize a mechanism of thrust sheet loading thrust loads are greatest in this region since thrust sheets have overridden large basement block uplifts beneath the illiac and peter the first range faults

glacier bed characteristics of midtre lovenbreen svalbard from high resolution seismic and radar surveying we conducted a seismic and radar survey of the central part of midtre lovenbreen a small polythermal valley glacier in svalbard we determined the physical properties of the material beneath the glacier by measuring the reflection coefficient of the bed by comparing the energy of the primary and multiple reflections and deriving the acoustic impedance by making reasonable assumptions about the properties of the basal ice we determined the acoustic impedance of the bed material as 6 78 1 53 x 10 6 kg m 2 s 1 we interpret the material beneath the glacier to be permafrost with up to 50 ice and we speculate that the material may be frozen talus similar to a deposit observed directly by others beneath another svalbard glacier the implication for midtre lovenbreen is that the basal material beneath the present glacier is not able to support fast flow we conclude that midtre lovenbreen has most likely had limited capability for faster flow in the past with motion dominated by internal deformation midtre lovenbreen is used as a study glacier for the scientific community in svalbard and a large number of studies have been based there our results show that it cannot be used as an analogue for larger glaciers in svalbard having distinct basal boundary conditions

a reconciled estimate of ice sheet mass balance we combined an ensemble of satellite altimetry interferometry and gravimetry data sets using common geographical regions time intervals and models of surface mass balance and glacial isostatic adjustment to estimate the mass balance of earth s polar ice sheets we find that there is good agreement between different satellite methods especially in greenland and west antarctica and that combining satellite data sets leads to greater certainty between 1992 and 2011 the ice sheets of greenland east antarctica west antarctica and the antarctic peninsula changed in mass by 142 49 14 43 65 26 and 20 14 gigatonnes year 1 respectively since 1992 the polar ice sheets have contributed on average 0 59 0 20 millimeter year 1 to the rate of global sea level rise

positive mass balance during the late 20th century on austfonna svalbard revealed using satellite radar interferometry determining whether increasing temperature or precipitation will dominate the cryo spheric response to climate change is key to forecasting future sea level rise the volume of ice contained in the ice caps and glaciers of the arctic archipelago of svalbard is small compared with that of the greenland or antarctic ice sheets but is likely to be affected much more rapidly in the short term by climate change this study investigates the mass balance of austfonna svalbard s largest ice cap equilibrium line fluxes for the whole ice cap and for individual drainage basins were estimated by combining surface velocities measured using satellite radar interferometry with ice thicknesses derived from radio echo sounding these fluxes were compared with balance fluxes to reveal that during the 1990s the total mass balance of the accumulation zone was 5 6 2 0 10 8 m 3 a 1 three basins in the quiescent phase of their surge cycles contributed 75 of this accumulation the remaining volume may be attributable either to as yet unidentified surge type glaciers or to increased precipitation this result emphasizes the importance of considering the surge dynamics of glaciers when attempting to draw any conclusions on climate change based on snapshot observations of the cryosphere

some comments on climatic reconstructions from ice cores drilled in areas of high melt poor consideration has been given in many arctic circum polar ice core studies to the effect of summer snow melt on chemistry stable isotope concentrations and time scales many of these corps are drilled close to the firn line where melt is intense some come from below the firn line where accumulation is solely in the form of super imposed ice in all cases seasonal signals are reduced or removed and in some time gaps develop during periods of excessive melting which situate the drill site in the ablation zone consequently cross correlations of assumed synchronous events among the cores are invalid so that time scales along the same cores differ between authors by factors of over 2 many so called climatic signals are imaginary rather than real by reference to published analyses of cores from the superimposed ice zone on devon ice cap koerner 1970 and meighen ice cap koerner and paterson 1974 it is shown how melt affects all the normally well established ice core proxies and leads to their misinterpretation despite these limitations the cores can give valuable low resolution records for all or part of the holocene they show that the thermal maximum in the circum polar arctic occurred in the early holocene this maximum effected negative balances on all the ice caps and removed the smaller ones cooler conditions in the second half of the holocene have caused the regrowth of these same ice caps

atmospheric pressure and gravity summary gravity green s functions for a column load of a model atmosphere on a spherical elastic earth are presented and they are used to evaluate the contribution of global atmospheric pressure variations to local gravity the green s functions are found to be relatively insensitive to the details of the model atmosphere but they are dependent on the temperature at the base of the column and on the relative height difference between the base of the column and the gravity station the total signal that global pressure systems contribute to gravity is about 30 gal of which about 90 per cent is produced by the atmosphere within 50 km of the gravity station a zone between 50 and 1000km from the gravity station contributes a couple of gal as does the remainder of the globe this pattern the coherence scale of pressure fluctuations the time and spatial scales appropriate to the hydrostatic approximation and the distance of the gravity station from the oceans suggest a division of the globe into local regional and global zones data requirements processing details and the reliability of the computed signal are different in each zone the local zone is within about 50 km of the gravity station within this zone pressure changes rapidly in time but is spatially coherent so that hourly observations of pressure and temperature at the gravity site alone are sufficient to compute an accurate correction except when a front is passing through the regional zone extends from the edge of the local zone to between several hundred and a thousand kilometres the signal from this zone is small and is only weakly coherent with the signal from the central zone so that a rather sparse array of hourly samples of pressure and temperature are required the gravity signal from the global zone can reach about a gal it varies on a time scale of days and is influenced by the response of the oceans to pressure variations previously reported observations that the admittance between local pressure and gravity residuals depends on epoch frequency or site are most probably due to incorrect modelling a proper local regional temperature and global correction can adequately account for the gravity signal from the atmosphere to within a few tens of ngal in the diurnal band and about 100 ngal in the days to seasonal band except during extreme weather conditions the application of the local correction lowers the power spectral density of the gravity residuals in every band from seasonal to hourly the regional global and temperature corrections lower the residual noise in the seasonal and synoptic bands but are not consistently effective at periods less than about half a day

glacier volume changes using aster satellite stereo and icesat glas laser altimetry a test study on edgeoya eastern svalbard currently one of the major methodological gaps in the observation of glaciers from space is the measurement of volume changes of mountain glaciers and ice caps in this paper we present a case study of comparing a digital elevation model derived from advanced spaceborne thermal emission and reflection radiometer aster satellite optical stereo elevation data derived from ice cloud and land elevation satellite geoscience laser altimeter system glas laser altimetry and contour lines from a topographic map from the 1970s for two ice caps in eastern svalbard kvalpyntfonna and digerfonna we obtain an overall elevation change of 0 55 or 0 61 m year between 1970 and 2002 aster or glas 2006 respectively from comparison of different methods and from different quality checks we estimate the error of this numbers to be on the order of 5 this paper demonstrates that and on how long term glacier volume changes can be observed from space over a large number of ice caps and glaciers

separation of the geodetic consequences of past and present ice mass change influence of topography with application to svalbard norway polar regions such as greenland svalbard and antarctica are deforming today because of both the present day ice mass pdim change of glaciers and the glacial isostatic adjustment gia following the pleistocene deglaciation observations handled in these areas contain both the contributions from the pdim change and gia this study aims at separating them by considering two specific gravity variation to vertical displacement ratios we first review the case of the viscoelastic rebound gia subsequent to the pleistocene deglaciation leading to a ratio c v the outcome of previous studies is that c v is approximately equal to 0 15 gal mm and almost independent of the deglaciation history ice geometry and viscosity profile of the mantle similarly we consider the elastic deformation resulting from pdim change which leads to a second ratio c e n several studies have shown that c e n approx 0 26 mu gal mm if one assumes that the changing glaciers are thin layers over the surface of a spherical earth model in this case we show that the separation between the contributions from pdim change and gia is unique if both gravity and height changes observations are available at the same station next we focus on c e n and show that according to the deglaciation glaciation context and from colocated gravity variation and ground vertical velocity measurements one can deduce a range of possible values for c e n studying the influence of the topography on c e n we first show that it tends to positive values if most of surrounding ice mass changes above the altitude of the observation site and to values lower than 0 26 gal mm if changes are below we next apply our general formalism to the case of the past and pdim changes in svalbard norway we compute the ratio c e n at the geodetic observatory at ny alesund and show the influence of the topography of the surrounding glaciers on the measured gravity and uplift rates we show that if the ice mass change is spatially uniform c e n does not depend on the speed of ice mass change and hence the separation of the contributions from pdim changes and gia can still be done univocally however if the ice mass change is not spatially uniform c e n depends on both the speed of ice mass change and the volume of ice change rate

a geophysical interpretation of the secular displacement and gravity rates observed at ny alesund svalbard in the arctic effects of post glacial rebound and present day ice melting summary we have analysed the ny alesund very long baseline interferometry vlbi data over the period 1994 august to 2004 may and we obtain secular displacement rates relative to a nnr nuvel 1a reference frame of 0 2 0 5 mm yr 1 1 7 0 5 mm yr 1 and 4 8 1 1 mm yr 1 for the north east and vertical directions respectively the corresponding global positioning system gps station displacement rates relative to the same reference frame for the north east and vertical directions are 0 2 0 6 mm yr 1 2 3 0 6 mm yr 1 and 6 4 1 5 mm yr 1 at nya1 and 0 1 0 5 mm yr 1 1 6 0 5 mm yr 1 and 6 9 0 9 mm yr 1 at nall where these gps rates were derived from the itrf2000 velocity solution of heflin from the comparison at 25 globally distributed collocated sites we found that the difference in uplift rate between vlbi and gps at ny alesund is mainly due to a gps reference frame scale rate error corresponding to 1 6 mm yr 1 in the gps vertical rates the uplift rate was estimated to be 5 2 0 3 mm yr 1 from the analysis of the tide gauge data at ny alesund hence the uplift rates obtained from three different kinds of data are very consistent each other the absolute gravity ag measurements at ny alesund which were carried out four times period 1998 2002 by three different fg5 absolute gravimeters lead to a decreasing secular rate of 2 5 0 9 gal yr 1 1 gal 10 8 ms 2 in this analysis the actual data obtained from a superconducting gravimeter at ny alesund were used in the corrections for the gravity tide including the ocean tide effect and for the air pressure effect we have

a mid mesozoic extension across central asia although relatively little is known about basin formation north of the himalayas recent stratigraphic studies of several sedimentary basins tarim dzhungaria tsaidam have demonstrated a common pattern of subsidence in post triassic times1 all these basins show rapid subsidence concurrent with the onset of himalayan orogenesis presumably reflecting both tectonic loading and increased sediment supply before that time however subsidence curves have the characteristic concave up shape of rifted margin sedimentary environments2 although data from these basins are not sufficiently detailed to justify a more thorough investigation the tadjik depression a sedimentary basin comprising the southwestern portion of the soviet republic of tadjikistan fig 1 contains a continuous and relatively well documented record of post jurassic sedimentation analysis of which suggests deposition in a rifted margin environment on crust thinned by 50

the geology and petroleum potential of the north afghan platform and adjacent areas northern afghanistan with parts of southern turkmenistan uzbekistan and tajikistan the north afghan platform has a pre jurassic basement unconformably overlain by a jurassic to paleogene oil and gas bearing sedimentary rock platform cover unconformably overlain by neogene syn and post orogenic continental clastics the pre jurassic basement has four units 1 an ordovician to lower devonian passive margin succession developed on oceanic crust 2 an upper devonian to lower carboniferous tournaisian magmatic arc succession developed on the passive margin 3 a lower carboniferous visean to permian rift passive margin succession 4 a triassic continental magmatic arc succession the mesozoic palaeogene cover has three units 1 a late triassic to middle jurassic rift succession is dominated by variable continental clastics thick coarse lenticular coal bearing clastics were deposited by braided and meandering streams in linear grabens while bauxites formed on the adjacent horsts 2 a middle to upper jurassic transgressive regressive succession consists of mixed continental and marine bathonian to lower kimmeridgian clastics and carbonates overlain by regressive upper kimmeridgian tithonian evaporite bearing clastics 3 a cretaceous succession consists of lower cretaceous red beds with evaporites resting unconformably on jurassic and older deposits overlain usually unconformably by cenomanian to maastrichtian shallow marine limestones which form a fairly uniform transgressive succession across most of afghanistan 4 a palaeogene succession rests on the upper cretaceous limestones with a minor break marked by bauxite in places thin palaeocene to upper eocene limestones with gypsum are overlain by thin conglomerates which pass up into shales with a restricted brackish water upper oligocene lower miocene marine fauna the neogene succession consists of a variable thickness of coarse continental sediments derived from the rising pamir mountains and adjacent ranges almost all the deformation of the north afghan platform began in the miocene oil and gas traps are mainly in upper jurassic carbonates and lower cretaceous sandstones across the entire north afghan block upper jurassic carbonate traps sealed by evaporites occur mainly north of the southern limit of the upper jurassic salt lower cretaceous traps consist of fine grained continental sandstones sealed by aptian albian shales and siltstones upper cretaceous palaeocene carbonates sealed by palaeogene shales are the main traps along the northern edge of the platform and in the tajik basin almost all the traps are broad anticlines related to neogene wrench faulting in this respect like similar traps along the san andreas fault hydrocarbon sources are in the mesozoic section the lower middle jurassic continental coal bearing beds provide about 75 of the hydrocarbons the callovian oxfordian provides about 10 the neocomian a meagre 1 and the aptian albian about 14 the coal bearing source rocks decrease very markedly in thickness southwards cross the north afghan platform much of the hydrocarbon generation probably occurred during the late cretaceous paleogene and migrated to structural traps during neogene deformation since no regional structural dip aids southward hydrocarbon migration and since the traps are all structural and somewhat small then there is little chance of very large petroleum fields on the platform nevertheless further studies of the north afghan platform should be rewarding because a the traps of strike slip belts are difficult to find without detailed exploration b the troubles of the last 20 years mean that almost no exploration has been done and c conditions may soon become more favorable there should be ample potential for oil and particularly gas discoveries especially in the northern and western parts of the north afghan platform

gravity and uplift rates observed in southeast alaska and their comparison with gia model predictions gravity change rates unit mgal yr 1 mgal 10 8 ms 2 over the 6 sites are estimated to be 4 50 0 76 and 4 30 0 92 by only using our data and also using the 1987 data respectively we computed the uplift and gravity rates predicted by ice load models for three different time intervals last glacial maximum lgm little ice age lia and present day pd except for 1 2 examples the predictions recover the observed rates within the observation errors we also estimated the viscous portion of the ratio unit mgal mm of the observed gravity rate to the uplift rate by correcting for the effects of the present day ice mass change pdimc two pdimc models are compared which are called here as uaf05 and uaf07 mean ratios are estimated to be 0 205 0 089 and 0 183 0 052 for the cases using uaf05 and uaf07 respectively the predicted mean ratios are 0 166 0 001 and 0 171 0 002 for the cases using both the lga and lia ice models and only using the lia ice model respectively we have confirmed that our ag and gps observations detect the rates and ratios reflecting an early stage of viscoelastic relaxation mainly due to the unloading effects after the lia

spatial distribution of cosmogenic 10be derived denudation rates between the western tian shan and northern pamir tajikistan abstract the northward motion of the pamir mountains relative to eurasia results in uplift and shortening of the pamir and tian shan orogens the vakhsh river catchment tajikistan is situated along a thrust system in the collision zone between the northern pamir and the western tian shan in this study spatial variations in catchment wide denudation rates are reported from the vakhsh river catchment with in situ produced cosmogenic 10be and 26al of 22 samples from active river channels samples distributed along 140 km of the main vakhsh river yield denudation rates between 1 28 0 16 to 1 94 0 26 mm yr in detail samples from rivers draining the northern pamir indicate denudation rates of 1 7 mm yr and a river draining the alai valley indicates denudation rates of 1 14 0 14 mm yr in contrast rivers draining the western tian shan show increasing denudation rates from 0 18 0 02 mm yr in the west to 2 70 0 36 mm yr in the east coincident with a small increase in the fluvial normalized steepness index ksn measured 26al 10be ratios range from 5 2 to 7 6 indicating a low influence of sediment storage and reworking of partially shielded material in addition locations resampled one year later confirm previously calculated denudation rates along the main trunk analysis of in situ produced cosmogenic 10be from depth profiles collected from a sequence of terraces preserved along the main trunk of the vakhsh river indicate terrace incision starting at 3 kyr as well as paleo denudation rates ranging between 1 75 0 54 to 2 01 0 39 mm yr 2 s d errors all these results suggest consistent high denudation rates in the northern pamir block and a spatial along strike gradient in western tian shan denudation rates the most likely explanation for the spatial gradient in western tian shan and vakhsh river denudation rates is a regional gradient in tectonic rock uplift

intracontinental subduction beneath the pamir mountains constraints from thermokinematic modeling of shortening in the tajik fold and thrust belt american philosophical society american association of petroleum geologists geological society of america exxon mobil corporation

displacements of the earth s surface due to atmospheric loading effects on gravity and baseline measurements atmospheric mass loads and deforms the earth s crust by performing a convolution sum between daily global barometric pressure data and mass loading green s functions we estimate the time dependent effects of atmospheric loading including those associated with short term synoptic storms on surface point positioning measurements and surface gravity observations we calculate the response for both an oceanless earth and an earth with an inverted barometer ocean load responses for near coastal stations are significantly affected by the inclusion of an inverted barometer ocean peak to peak vertical displacements are frequently 15 20 mm with accompanying gravity perturbations of 3 6 gal baseline changes can be as large as 20 mm or more the perturbations are largest at higher latitudes and during winter months these amplitudes are consistent with the results of rabbel and zschau 1985 who modeled synoptic pressure disturbances as gaussian functions of radius around a central point deformation can be adequately computed using real pressure data from points within about 1000 km of the station knowledge of local pressure alone is not sufficient rabbel and zschau s hypothesized corrections for these displacements which use local pressure and the regionally averaged pressure prove accurate at points well inland but are in general inadequate within a few hundred kilometers of the coast

relocation effects of dredged marine sediments on mercury geochemistry venice lagoon italy abstract understanding the biogeochemical process of hg is critical in the overall evaluation of the ecological impacts resulting from the reuse of hg contaminated dredged sediment sediment banks v1 and v2 were constructed with freshly dredged sediments from a navigational channel in venice lagoon italy with the goal of clarifying potential differences in the biogeochemistry of hg between the reused dredged sediments and those from surrounding sites ss1 and s2 toward this purpose hg and monomethylmercury mmhg concentrations and hg methylation rates mmrs in the surface 2 5 cm sediments were monitored along with ammonium iron sulfate and sulfide concentrations in the pore waters of banks and surrounding sites from november 2005 to february 2007 pore water analyses indicate that the bank sediments are characterized by lower levels of sulfate and iron and by higher levels of ammonium and sulfide compared to the surrounding sediments with respect to hg speciation the fractions of mmhg in total hg mmhg hg and the mmrs were significantly lower in the bank v1 compared to those in the reference site ss1 whereas the mmhg hg and the mmrs were similar between v2 and s2 a negative correlation is found between the logarithm of the particle water partition coefficient of hg and the mmr indicating that the reduced mmrs in v1 are caused by the limited concentrations of dissolved hg organic matter appears to play a key role in the control of mmr via the control of hg solubility

extreme aridification since the beginning of the pliocene in the tarim basin western china abstract mid latitude central asia is characterized by an extreme arid landscape among the central asian deserts the taklimakan desert is the largest shifting sand desert which is located in the rain shadow of the tibetan plateau and of the other central asian high mountains the formation of this desert is important for placing widespread aridification into a regional tectonic context at the western end of the himalayan tibetan orogen however there still exists considerable controversy regarding the timing of desert formation thus impeding our understanding of the climatic effects of the tibetan uplift and regional environmental changes here we report new biostratigraphic age control and multiple high resolution climatic records from the center of the taklimakan desert our results reveal dramatic environmental changes at 5 ma suggesting that an extremely dry climate has prevailed since the beginning of the pliocene which is consistent with findings from a high resolution borehole record about 670 km to the east in the same basin the two records combined demonstrate that an extremely dry environment prevailed in the entire tarim basin from approximately 5 ma this was related to the reduced transport of water vapor by westerlies in response to the retreat of the paratethys ocean driven by global climatic cooling and the closed oceanic water vapor pathway between the pamir and the tian shan ranges driven by the ongoing india eurasia collision

study of the atmospheric pressure loading signal in very long baseline interferometry observations 1 redistribution of air masses due to atmospheric circulation causes loading deformation of the earth s crust which can be as large as 20 mm for the vertical component and 3 mm for horizontal components rigorous computation of site displacements caused by pressure loading requires knowledge of the surface pressure field over the entire earth surface a procedure for computing three dimensional displacements of geodetic sites of interest using a 6 hourly pressure field from the national centers for environmental prediction numerical weather models and the ponte and ray 2002 model of atmospheric tides is presented we investigated possible error sources and found that the errors of our pressure loading time series are below the 15 level we validated our model by estimating the admittance factors of the pressure loading time series using a data set of 3 5 million very long baseline interferometry observations from 1980 to 2002 the admittance factors averaged over all sites are 0 95 0 02 for the vertical displacement and 1 00 0 07 for the horizontal displacements for the first time horizontal displacements caused by atmospheric pressure loading have been detected the closeness of these admittance factors to unity allows us to conclude that on average our model quantitatively agrees with the observations within the error budget of the model at the same time we found that the model is not accurate for several stations that are near a coast or in mountain regions we conclude that our model is suitable for routine data reduction of space geodesy observations

timing and magnitude of displacement on the altyn tagh fault constraints from stratigraphic correlation of adjoining tarim and qaidam basins nw china the altyn tagh fault plays an important role in growth of the north western tibetan plateau but the timing of its inception and magnitude of left lateral displacement are not well constrained this study provides new independent constraints by correlating stratigraphic development and spatial distribution of the neighbouring tarim and qaidam basins it is shown that the tarim and qaidam basins experienced quite similar stratigraphic and sedimentary evolution from late sinian to early palaeogene times this fact indicates that the tarim and qaidam basins were a single block at least until oligocene time which was then offset by the altyn tagh fault early palaeozoic and late triassic suture zones within the east and west kunlun and pinch outs of mesozoic strata are chosen as piercing lines restoration of these lines gives total offset estimates of 350 400 km across the south western and central segments of the altyn tagh fault

a reconciled estimate of glacier contributions to sea level rise 2003 to 2009 glaciers distinct from the greenland and antarctic ice sheets are losing large amounts of water to the world s oceans however estimates of their contribution to sea level rise disagree we provide a consensus estimate by standardizing existing and creating new mass budget estimates from satellite gravimetry and altimetry and from local glaciological records in many regions local measurements are more negative than satellite based estimates all regions lost mass during 2003 2009 with the largest losses from arctic canada alaska coastal greenland the southern andes and high mountain asia but there was little loss from glaciers in antarctica over this period the global mass budget was 259 28 gigatons per year equivalent to the combined loss from both ice sheets and accounting for 29 13 of the observed sea level rise

oxic anoxic oscillations and organic carbon mineralization in an estuarine maximum turbidity zone the gironde france the study of vertical particle dynamics in the highly turbid gironde estuary has shown intense cycles of sedimentation and resuspension at both diurnal and neap spring time scales fluid mud with suspended particulate matter spm concentrations between 50 and 500 g liter 21 has been observed during neap tides vertical profiles of biogeochemical parameters have been measured in the fluid mud anoxic conditions have been detected when spm concentration exceeded 50 g liter 21 in the upstream and 140 g liter 21 in the downstream parts of the maximum turbidity zone mtz at the downstream part of the mtz anoxic fluid mud was partitioned into a denitrification layer spm 5 140 250 g liter 21 intensively reworked at the tidal time scale and by an mn iv reduction layer spm 250 g liter 21 preferentially reworked at the neap spring time scale due to the alternation of sedimentation and resuspension periods most of the sediment experienced oxic anoxic oscillations throughout the neap spring cycle fluid mud resuspension occurred without any observable incidence on the surface water oxygenation an increase in total alkalinity was found in the fluid mud due to both anaerobic respiration and a carbonate dissolution coupled to aerobic respiratory co2 generation this phenomenon significantly affected the inorganic carbon budget of the estuary increasing the hco input to the coastal ocean and reducing the co2 flux to the atmosphere an 2 3 accumulation of labile dissolved organic carbon observed in the fluid mud suggests that these oscillations result in an acceleration of particulate organic matter pom decomposition in the gironde mtz a net loss of refractory land derived pom occurs this system acts as an efficient oxic suboxic fluidized bed reactor similar to mobile deltaic muds

spectral finite element approach to viscoelastic relaxation in a spherical compressible earth application to gia modelling summary the choice of the physical model of postglacial rebound plays a decisive role to derive information about the mantle rheology and viscosity from observed data in models for the mantle rheology an incompressible maxwell material is often assumed in spite of seismic observations showing that the earth s mantle is composed of compressible material in this study in order to assess the influence of compressibility on glacial isostatic adjustment gia the spectral finite element approach proposed by martinec is extended to incorporate the effect of compressibility using this approach the present day velocity field is computed for peltier s ice5g vm2 earth model glaciation history combination considering the sea level equation in the formulation of hagedoorn et al the results show that the effect of compressibility on the vertical displacement rate is small whereas the horizontal rates are markedly enhanced for example the rate around fennoscandia and laurentide becomes twice as large when compressibility is considered this large difference between the compressible and incompressible models can be reduced by adjusting the elastic rigidity of the incompressible model so that the flexural rigidity becomes approximately the same as that in the compressible model however differences of 1 mm yr 1 still remain for wavelengths longer than 8000 km these findings show that when modelling horizontal motion induced by gia the influence of compressibility cannot be neglected

relationship between hydrology and seasonal distribution of suspended sediments on the continental shelf of the bay of biscay abstract numerous oceanographic cruises with hydrology water sampling drift current measurements carried out since 1980 on the continental shelf of the bay of biscay together with available noaa avhrr infra red images form the basis of a proposed explanation for the processes responsible for the distribution of suspended sediments on the shelf the seasonal hydrographic structure of continental shelf waters is of paramount importance in sediment distribution in summer there is an horizontal stratification of water masses and suspended sediment distribution is closely related to the thermo haline structure a fresher water mass with less suspended material lies on a thicker and more turbid homogeneous layer during winter when sediment discharge from the rivers often reaches its annual maximum an oceanic thermo haline wedge occurs on the shelf at around 100 m as a result winter turbidity values on the outer continental shelf are low comparable to summer values and a permanent nepheloid layer is never observed the wedge which lasts for several months may act as a filter preventing transport to the slope high turbidities on the external shelf and the continental slope are only measured in spring when the thermo haline wedge disappears it seems possible that during winter time suspended materials brought by rivers are deposited in the grande vasiere the large mud patch it is postulated that the position of this mud patch is linked to the long term stable location of the thermo haline front that separates oceanic waters from the colder and less salty coastal waters

basin evolution in a folding lithosphere altai sayan and tien shan belts in central asia abstract central asia is a classical example for continental lithospheric folding in particular the altay sayan belt in south siberia and the kyrgyz tien shan display a special mode of lithospheric deformation involving decoupled lithospheric mantle folding and upper crustal folding and faulting both areas have a heterogenous crust with a long history of accretion collision subsequently reactivated as a far field effect of the indian eurasian collision thanks to the youthfulness of the tectonic deformation in this region peak deformation in late pliocene early pleistocene the surface expression of lithospheric deformation is well documented by the surface topography and superficial tectonic structures a review of the paleostress data and tectono stratigraphic evolution of the kurai chuya basin in siberian altai zaisan basin in kazakh south altai and issyk kul basin in kyrgyz tien shan suggests that they were initiated in an extensional context and inverted by a combination of fault controlled deformation and flexural folding in these basins fault controlled deformation alone appears largely insufficient to explain their architecture lithospheric buckling inducing surface tilting uplift and subsidence also played an important role they form typical basins in a folding lithosphere flb their characteristic basin fill and symmetry inner structure folding wavelength and amplitude thermal regime time frame are examined in relation to basement structure stress field strain rate timing of deformation and compared to existing modelling results

svalbard glacier elevation changes and contribution to sea level rise 1 we compare satellite altimetry from the ice cloud and land elevation satellite icesat 2003 2007 to older topographic maps and digital elevation models 1965 1990 to calculate long term elevation changes of glaciers on the svalbard archipelago results indicate significant thinning at most glacier fronts with either slight thinning or thickening in the accumulation areas except for glaciers that surged which show thickening in the ablation area and thinning in the accumulation areas the most negative geodetic balances occur in the south and on glaciers that have surged while the least negative balances occur in the northeast and on glaciers in the quiescent phase of a surge cycle geodetic balances are related to latitude and to the dynamical behavior of the glacier the average volume change rate over the past 40 years for svalbard excluding austfonna and kvitoya is estimated to be 9 71 0 55 km3 yr 1 or 0 36 0 02 m yr 1 w equivalent for an annual contribution to global sea level rise of 0 026 mm yr 1 sea level equivalent

quiescent phase dynamics and surge history of a polythermal glacier hessbreen svalbard hessbreen is a 5 km 2 polythermal glacier in southern spitsbergen it is believed to have surged at the end of the 19th century and another surge started in 1969 not in 1972 as earlier studies suggested the surge was probably triggered in the middle section of the glacier and affected the upper part approximately 4 years before including the whole glacier present velocities are low increasing from 0 3 m a 1 at the snout to 4 8 m a 1 above the equilibrium line a distinct velocity reduction occurs where the glacier narrows this suggests the velocities here are affected by the cold marginal and frontal ice large seasonal variations with summer velocities of more than twice the winter velocities in the middle part of the glacier indicate a seasonal change in the drainage system in this area in the lower part there is no apparent sliding the balance flux estimate indicates that the actual ice flux is only about 50 of that required for steady state so hessbreen appears to be building up in the accumulation area the surge duration is now estimated to be 8 years

geodetic secular velocity errors due to interannual surface loading deformation geodetic vertical velocities derived from data as short as 3 yr are often assumed to be representative of linear deformation over past decades to millennia we use two decades of surface loading deformation predictions due to variations of atmospheric oceanic and continental water mass to assess the effect on secular velocities estimated from short time series the interannual deformation is time correlated at most locations over the globe with the level of correlation depending mostly on the chosen continental water model using the most conservative loading model and 5 yr long time series we found median vertical velocity errors of 0 5 mm yr 1 over the continents 0 3 mm yr 1 globally exceeding 1 mm yr 1 in regions around the southern tropic horizontal velocity errors were seven times smaller unless an accurate loading model is available a decade of continuous data is required in these regions to mitigate the impact of the interannual loading deformation on secular velocities

some effects of lateral heterogeneities in the upper mantle on postglacial land uplift close to continental margins summary we investigate the effects of lateral heterogeneities in the upper mantle on the calculation of postglacial land uplift for the model calculations we use a commercial finiteelement code which enables us to solve the equations governing a layered isotropic incompressible maxwell viscoelastic half space with laterally varying layer thicknesses and physical properties following previous investigations performed by sabadini yuen portney 1986 and gasperini sabadini 1989 we extend their results using a more realistic loading history and different earth models we then focus our attention on the question whether lateral heterogeneities in the upper mantle can be modelled correctly using a set of homogeneous earth models to this end a comparison of model calculations using both laterally homogeneous and heterogeneous earth models is performed we find that lateral heterogeneities in the upper mantle significantly influence the calculated postglacial land uplift the resolving power of relative sea level observations for the prescribed lateral heterogeneities used in this study is mainly focused on observations around the load margin and outside the glaciated areas where differences in predicted land uplift between individual models are large enough to be resolved by observations we can qualitatively determine lateral heterogeneities in the upper mantle using a set of laterally homogeneous earth models if the geological structure for example a continental margin is known however in order to infer the correct values of lithospheric thickness and asthenospheric viscosity we need to use laterally heterogeneous models

the last glacial maximum of svalbard and the barents sea area ice sheet extent and configuration abstract the timing extent and configuration of the late weichselian barents ice sheet has been debated for several decades this debate has arisen largely because of the limited or conflicting field evidence on which most models have been based in particular reconstruction of the marine parts of the former barents ice sheet has been controversial this paper aims to review the geological observations and interpretations regarding the size and timing of the late weichselian ice sheet combined with numerical modelling of its formation in order to produce a reconstruction of ice sheet extent and behaviour sub glacial till with overlying glacimarine deposits dated to the late weichselian is found over most of the barents sea floor and the continental shelf west of svalbard glacially induced debris flow deposits on the large bjonoya and isfjorden trough mouth fans strongly support the idea of ice sheet extension to the shelf edge during maximum glaciation isobase maps show a centre of post glacial uplift in the north central barents sea and glaciological and isostatic modelling suggest that the ice sheet was 2000 3000 m thick in this area the ice sheet was confluent with ice over the kara sea but the interaction between the barents and kara ice sheets is not yet fully understood the deglaciation of the barents ice sheet started ca 15 ka probably by calving within the deeper troughs by 12 ka most of the central barents sea was ice free and ice remained over the svalbard franz josef land and novaja zemlya archipelagos and adjacent shallow shelf areas the coasts and fjords of these islands were ice free by 10 ka

climatic and tectonic controls on cretaceous palaeogene sea level changes recorded in the tarim epicontinental sea abstract during late cretaceous to eocene times a vast epicontinental sea existed in the western tarim basin of china and its appearance evolution and demise played an important role in the paleogeographic and paleoclimatic history of central asia sea level changes in the tarim sea and its controlling factors have been poorly studied so far here we present a detailed stratigraphic and sedimentological analysis of six upper cretaceous to eocene stratigraphic sections in the southwestern tarim basin seventeen lithofacies types were identified overall based on which changes of paleowater depth were reconstructed between the mid cretaceous cenomanian and the late eocene priabonian the tarim sea experienced five transgressive regressive cycles deposition took place in middle ramp to inner ramp settings during transgressions and in coastal plain lacustrine and braided river environments during regressions the sea retreated but did not withdraw completely during late cretaceous to early paleocene regressive stages whereas seaways disappeared completely from the studied area during late paleocene to eocene regressions the tarim basin lay on a stable craton in the late cretaceous when paleowater depth was chiefly controlled by eustatic change tectonic subsidence started to increase at middle paleocene time simultaneously with the selandian dry event in the tarim basin when a thick gypsum unit was deposited during incipient development of a foreland basin such a middle paleocene onset of tectonic activity also indicated by discrepancies between the regional paleowater depth curve and the global sea level curve and by penecontemporaneous uplift of the west kunlun range in northeastern pamir were most likely a far field effect of the onset of the india asia continental collision to the south

decadal geodetic variations in ny alesund svalbard role of past and present ice mass changes the geodetic rates for the gravity variation and vertical uplift in polar regions subject to past and present day ice mass changes pdimcs provide important insight into the rheological structure of the earth we provide an update of the rates observed at ny alesund svalbard to do so we extract and remove the significant seasonal content from the observations the rate of gravity variations derived from absolute and relative gravity measurements is 1 39 0 11 gal yr 1 the rate of vertical displacements is estimated using gps and tide gauge measurements we obtain 7 94 0 21 and 8 29 1 60 mm yr 1 respectively we compare the extracted signal with that predicted by gldas noah and era interim hydrology models we find that the seasonal gravity variations are well represented by local hydrology changes contained in the era interim model the phase of seasonal vertical displacements are due to non local continental hydrology and non tidal ocean loading however a large part of the amplitude of the seasonal vertical displacements remains unexplained the geodetic rates are used to investigate the asthenosphere viscosity and lithosphere asthenosphere thicknesses we first correct the updated geodetic rates for those induced by pdimcs in svalbard using published results and the sea level change due to the melting of the major ice reservoirs we show that the latter are at the level of the geodetic rate uncertainties and are responsible for rates of gravity variations and vertical displacements of 0 29 0 03 gal yr 1 and 1 11 0 10 mm yr 1 respectively to account for the late pleistocene deglaciation we use the global ice evolution model ice 3g the little ice age lia deglaciation in svalbard is modelled using a disc load model with a simple linear temporal evolution the geodetic rates at ny alesund induced by the past deglaciations depend on the viscosity structure of the earth we find that viscous relaxation time due to the lia deglaciation in svalbard is more than 60 times shorter than that due to the pleistocene deglaciation we also find that the response to past and pdimcs of an earth model with asthenosphere viscosities ranging between 1 0 and 5 5 10 18 pa s and lithosphere resp asthenosphere thicknesses ranging between 50 and 100 km resp 120 and 170 km can explain the rates derived from geodetic observations

the thermal regime of sub polar glaciers mapped by multi frequency radio echo sounding radio echo soundings provide an effective tool for mapping the thermal regimes of polythermal glaciers on a regional scale radar signals of 320 370 mhz penetrate ice at sub freezing temperatures but are reflected from the top of layers of ice which are at the melting point and contain water radar signals of 5 20 mhz on the other hand see through both the cold and the temperate ice down to the glacier bed radio echo soundings at these frequencies have been used to investigate the thermal regimes of four polythermal glaciers in svalbard kongsvegen uversbreen midre lovenbreen and austre broggerbreen in the ablation area of kongsvegen a cold surface layer 50 160m thick was underlain by a warm basal layer which is advected from the temperate accumulation area the surface ablation of this cold layer may be compensated by freezing at its lower cold temperate interface this requires that the free water content in the ice at the freezing interface is about 1 of the volume the cold surface layer is thicker beneath medial moraines and where cold based hanging glaciers enter the main ice stream on uversbreen the thermal regime was similar to that of kongsvegen a temperate hole was found in the otherwise cold surface layer of the ablation area in a surface depression between kongsvegen and uversbreen where meltwater accumulates during the summer near the subglacial lake setevatnet 250 m a s l lovenbreen was frozen to the bed at the snout and along all the mountain slopes but beneath the central part of the glacier a warm basal layer up to 50m thick was fed by temperate ice from two cirques on austre broggerbreen a temperate basal layer was not detected by radio echo soundings but the basal ice was observed to be at the melting point in two boreholes

least squares restoration of tertiary thrust sheets in map view tajik depression central asia the tajik depression located west of the pamirs and south of the tien shan is a compressional intermontane basin bounded by basement overthrusts and filled with mesozoic and cenozoic sediments the internal structure is typical of a thin skinned tbld and thrust belt kinematic data available in the literature suggest that indentation of the pamirs into asia durino the cenozoic collision of india and asia has been accommodated in various ways within the depression including westward extrusion thickening combined with wrenching along n s tblds and thrusts and counterclockwise rotations these various detbrmation processes can be analyzed and quantified by reconstruction of the predeformed state of the depression however the combina tion of thrusting wrenching and block rotations implies a nonplane deformation which cannot be restored properly using balanced cross sections alone we have therefore developed a numerical method for restoration of stratigraphic surfaces designed for regions of nonplane compressional tectonics the deformed region is represented in map view as a mosaic of fault bounded blocks overlapping each other along the faults blocks are separately unfolded and then numerically packed together by least squares minimization of overlaps yielding fields of finite horizontal translations and rotations about vertical axes to analyze the deformation postdating the collision of india and asia we have restored a stratigraphic surface at the base of the cenozoic first in order to test the numerical method we restored a map that had previously been restored by a purely manual method restoration of a second map drawn from newly available subsurface data leads to geometrical inconsistencies overlaps and gaps which cannot be reduced remain in the restored state after correction of these inconsistencies restoration yields a complex mode of deformation for the depression individual thrust slices have undergone counterclockwise rotations about verti cal axes the magnitudes increasing from west to east up to a maximum of 40 o near the pamirs horizontal shortening is 150 km 35 in the center of the depression and 240 km 85 in the northeastern part between the pamirs and the tien shan strike slip motions commonly not revealed by balancing cross sections are associated with thrusting on faults striking n s inde pendent paleomagnetic data and slip directions on small scale faults provide positive checks on the results of our restoration

shallow upper mantle rheology and secular ice sheet fluctuations on time scales from decades to centuries continental cryospheric forcing in response to climate change constitutes a major source of isostatic disequilibrium that may influence future regional sea level variations current vertical displacements and gravity field variations are often estimated neglecting rheological effects and thus assuming a fully elastic response of the earth in this study we adopt a more general point of view aiming at describing ongoing surface movements resulting from recent glacial instabilities also taking into account the effects associated with shallow upper mantle and crustal rheologies our computations are based on the post widder laplace inversion formula which permits the straightforward computation of load deformation coefficients for steady state and transient rheologies up to very high harmonic degrees using a surface load with a simple geometry and time history we compare the classical elastic solutions to those obtained considering the rheological response of the shallow upper mantle while at the center of the ice sheet rheology only magnifies the elastic response the pattern and time history of vertical displacement at the ice sheet margins show a greater complexity mainly due to the development of lateral forebulges whose shape and amplitude are particularly sensitive to the rheology of the shallow upper mantle in this region assuming an elastic rheology is generally appropriate on a century time scale but significant deviations from a purely elastic response both sign and amplitude are observed at longer time scales or when a low viscosity zone with maxwell rheology is taken into account

postglacial sea level change on a rotating earth summary we present a complete derivation of the equation governing long term sea level variations on a spherically symmetric self gravitating maxwell viscoelastic planet this new sea level equation extends earlier work by incorporating in a gravitationally self consistent manner both a time dependent ocean continent geometry and the in uence of contemporaneous perturbations to the rotation vector of the planet we also outline an e cient pseudo spectral numerical methodology for the solution of this equation and present a variety of predictions based on a suite of earth models of relative sea level rsl variations due to glacial isostatic adjustment gia these results show that the contribution to the predicted rsl signal from gia induced perturbations to the rotation vector can reach 7 8 m over the postglacial period in geographic regions where the rotationally induced signal is a maximum this result is sensitive to variations in the adopted lower mantle viscosity and is relatively insensitive to variations in the adopted lithospheric thickness we also show that the rotationally induced component of rsl change is su cient to in uence previous estimates of late holocene melting events and ongoing sea level change due to giawhich were based on a rsl theory for a non rotating earth in particular estimates of antarctic melting over the last 5 kyr based on the amplitude of sea level highstands from the australian region may require an adjustment downwards of the order of 0 5 m of equivalent sea level rise furthermore present day rates of sea level change are perturbed by as much as 0 2 mm yr 1 by the rotational component of sea level change and this has implications for gia corrections of the global tide gauge record over the period from the last glacial maximum to the present we predict a distinctly non monotonic variation in the rotation induced component of rsl this is in agreement with our previous preliminary study milne mitrovica 1996 but contrasts signi cantly with predictions presented by han wahr 1989 and bills james 1996 we demonstrate that the disagreement arises as a consequence of approximations adopted in the latter studies we furthermore refute an assertion by bills james 1996 that previously published constraints on mantle viscosity and ice sheet histories which did not incorporate a rotation induced rsl component are largely invalidated by this omission

ice 3g a new global model of late pleistocene deglaciation based upon geophysical predictions of post glacial relative sea level change a new high resolution global model of late pleistocene deglaciation is inferred on the basis of geophysical predictions of postglacial relative sea level variations in which the ice ocean solid earth interaction is treated in a gravitationally self consistent fashion for the purpose of these analyses the radial viscoelastic structure of the planet is assumed known on the basis of previously published sensitivity tests on solutions of the forward problem only radiocarbon controlled relative sea level histories from sites that were actually ice covered with one or two additions are employed to constrain the model leaving relative sea level rsl data from sites that were not ice covered to be employed to confirm its consistency results for these confirmatory analyses are reported elsewhere here the new deglaciation model referred to as ice 3g is compared to previous models derived by several independent means and tested against a number of additional observations other than sea level histories including geologically controlled retreat isochrones oxygen isotope data from deep sea sedimentary cores and coral terrace elevations the latter two observations strongly constrain the net sea level rise that has occurred since the onset of deglaciation and therefore the mass of ice that melted during the last glacial interglacial transition

numerical modeling of the late weichselian svalbard barents sea ice sheet abstract previous reconstructions of the ice cover of the svalbard barents sea region during the late weichselian have ranged from small ice masses on svalbard to complete inundation of the barents shelf region by an ice sheet several kilometers thick we have used a time dependent finite difference numerical model to undertake a new glaciological reconstruction for the svalbard barents sea ice sheet over the last 30 000 yr the numerical model requires environmental forcing functions in the form of air temperature and precipitation and their behavior with respect to altitude together with sea level change and an iceberg calving relation ice buildup on svalbard is calculated to have begun 28 000 yr ago and maximum dimensions were reached by 20 000 yr ago covering svalbard and the northwestern barents sea with a center of mass 1 3 km thick around eastern svalbard decay was complete by about 10 000 yr ago the margin of the modeled ice sheet at its maximum is in good agreement with observed sea floor morphological features but there are discrepancies in timing between the modeled ice sheet decay and i a dated meltwater spike in fram strait and ii the observed rebound curves for svalbard an inverse approach was used to predict ice sheet decay and it was found that increasing the rate of iceberg calving within the model produces a deglaciation some 2000 yr earlier which is compatible with these two independent datasets the reconstruction is also compatible with geological evidence on the isostatic response of bjornoya close to the southern limit of the ice sheet and seismically observed deposits interpreted to be ice proximal facies located in the northwestern barents sea our time dependent model reconstructions of the svalbard barents sea ice sheet indicate ice cover over only the northwestern barents sea during the late weichselian but this does not preclude the presence of ice derived from fennoscandia and the kara sea region elsewhere in the barents sea

deglacial land emergence and lateral upper mantle heterogeneity in the svalbard archipelago ii extended results for high resolution load models summary in paper i breuer wolf 1995 a preliminary interpretation of the postglacial land emergence observed at a restricted set of six locations in the svalbard archipelago was given the study was based on a simple model of the barents sea ice sheet and suggested increases in lithosphere thickness and asthenosphere viscosity with increasing distance from the continental margin in the present paper the newly developed high resolution load model barents 2 and land uplift observations from an extended set of 25 locations are used to study further the possibility of resolving lateral heterogeneity in the upper mantle below the northern barents sea a comparison of the calculated and observed uplift values shows that the lithosphere thickness is not well resolved by the observations although values above 110 km are most common for this parameter in contrast to this there are indications of a lateral variation of asthenosphere viscosity whereas values in the range 10 8 1020 pa s are inferred for locations close to the continental margin 1020 102 pa s are suggested further away from the margin a study of the sensitivity of the values found for lithosphere thickness and asthenosphere viscosity to modifications of load model barents 2 shows that such modifications can be largely accommodated by appropriate changes in lithosphere thickness whereas the suggested lateral variation of asthenosphere viscosity is essentially unaffected an estimate of the influence of the fennoscandian ice sheet leads to the conclusion that its neglect results in an underestimation of the thickness of the barents sea ice sheet by about 10 per cent

past and present day ice mass variation on svalbard revealed by superconducting gravimeter and gps measurements 1 we use superconducting gravimeter sg and global positioning system gps measurements from ny alesund svalbard to infer changes in ice mass loss between september 1999 and september 2010 we find that during this period the gravity rate and vertical crustal velocities are changing with time adding to evidence about varying rates of ice mass loss the gravity rate varies through 10 years of observation 0 23 gal yr in 2000 2002 3 22 gal yr in 2002 2005 and 1 10 gal yr in 2005 2010 the gravity changes agree well with the observed uplift rates measured by gps which are 4 4 11 3 and 7 4 mm yr over the same periods in addition we generate model predictions which account for past and present day ice mass variation we find that the models under predict both the observed uplift rates and gravity changes

decoding the origins of vertical land motions observed today at coasts in recent decades geodetic techniques have allowed detecting vertical land motions and sea level changes of a few millimetres per year based on measurements taken at the coast tide gauges on board of satellite platforms satellite altimetry or both global navigation satellite system here contemporary vertical land motions are analysed from january 1993 to july 2013 at 849 globally distributed coastal sites the vertical displacement of the coastal platform due to surface mass changes is modelled using elastic and viscoelastic green s functions special attention is paid to the effects of glacial isostatic adjustment induced by past and present day ice melting various rheological and loading parameters are explored to provide a set of scenarios that could explain the coastal observations of vertical land motions globally in well instrumented regions predicted vertical land motions explain more than 80 per cent of the variance observed at scales larger than a few hundred kilometres residual vertical land motions show a strong local variability especially in the vicinity of plate boundaries due to the earthquake cycle significant residual signals are also observed at scales of a few hundred kilometres over nine well instrumented regions forming observation windows on unmodelled geophysical processes this study highlights the potential of our multitechnique database to detect geodynamical processes driven by anthropogenic influence surface mass changes surface loading and glacial isostatic adjustment and tectonic activity including the earthquake cycle sediment and volcanic loading as well as regional tectonic constraints future improvements should be aimed at densifying the instrumental network and at investigating more thoroughly the uncertainties associated with glacial isostatic adjustment models

on postglacial sea level summary an exact method is presented for calculating the changes in sea level that occur when ice and water masses are rearranged on the surface of elastic and viscoelastic non rotating earth models the method is used to calculate the instantaneous elastic and delayed vi scoelastic sea level changes following the partial melting of late quaternary ice sheets we find that there can be large errors in the usual assumption that changes in sea level are uniform over the ocean basins if a quantity of ice equivalent to a uniform 100 m rise in sea level melts from the laurentide and fennoscandian ice sheets then in the south pacific the instantaneous rise in sea level can be as large as 120m in the north atlantic the instantaneous rise is always less than 100 m there is a zone in the north atlantic with almost no sea level change and near greenland and norway the sea level falls rather than rises by over 100 m one thousand years after the melting a forebulge migrating towards the ice loads causes water to flow from the south pacific into the north pacific suggesting that raised beaches should occur in the south pacific the gravitational attraction of an ice mass upon a nearby ocean tends to hold sea level high in the vicinity of the ice this extra load near the ice may have a significant influence on postglacial isostatic adjustment

gravity anomalies over the ferghana valley central asia and intracontinental deformation gravity anomalies over the ferghana valley a deep sedimentary basin in the western tien shan differ from those expected for local airy isostatic equilibrium by 120 mgal and imply a deficit of mass beneath the basin equivalent to a moho deeper by 10 km than prevails where isostasy holds although the ferghana valley is underlain by thick mesozoic and cenozoic sediment measurements of density show that this material cannot account for the deficit of mass gravity anomalies over both the surrounding mountain belts and the kazakh platform farther north imply that local airy isostatic equilibrium is approached flexure of a relatively thin effectively elastic plate thickness 10 15 km loaded by the present topography can account for the range of bouguer anomalies of 50 to 450 mgal over these regions we infer that approximately north south shortening of the relatively thin lithosphere has created mountains north and south of the basin has warped the basement of the immediate surroundings of the basin up by folding the mantle lithosphere and has forced the basin floor down beneath the ferghana valley it appears that the preexisting thermal structure and variations in crustal thickness have dictated the styles and distribution of deformation in this region

cretaceous evolution of the central asian proto paratethys sea tectonic eustatic and climatic controls the timing and mechanisms of the cretaceous sea incursions into central asia are still poorly constrained we provide a new chronostratigraphic framework based on biostratigraphy and magnetostratigraphy together with detailed paleoenvironmental analyses of cretaceous records of the proto paratethys sea fluctuations in the tajik and tarim basins the early cretaceous marine incursion in the western tajik basin was followed by major marine incursions during the cenomanian ca 100 ma and santonian ca 86 ma that reached far into the eastern tajik and tarim basins these marine incursions were separated by a turonian coniacian ca 92 86 ma regression basin wide tectonic subsidence analyses imply that the early cretaceous sea incursion into the tajik basin was related to increased pamir tectonism we find that thrusting along the northern edge of the pamir at ca 130 90 ma resulted in increased subsidence in a retro arc basin setting this tectonic event and coeval eustatic highstand resulted in the maximum observed geographic extent of the sea during the cenomanian ca 100 ma the following turonian coniacian ca 92 86 ma major regression driven by eustasy coincides with a sharp slowdown in tectonic subsidence during the late orogenic unloading period with limited thrusting the santonian ca 86 ma major sea incursion was likely controlled by eustasy as evidenced by the coeval fluctuations in the west siberian basin an early maastrichtian cooling ca 71 70 ma potentially connected to global late cretaceous trends is inferred from the replacement of mollusk rich limestones by bryozoan and echinoderm rich limestones

recent elevation changes of svalbard glaciers derived from icesat laser altimetry abstract we have tested three methods for estimating 2003 2008 elevation changes of svalbard glaciers from multi temporal icesat laser altimetry a linear interpolation of crossover points between ascending and descending tracks b projection of near repeat tracks onto common locations using digital elevation models dems and c least squares fitting of rigid planes to segments of repeat track data assuming a constant elevation change rate the two repeat track methods yield similar results and compare well to the more accurate but sparsely sampled crossover points most glacier regions in svalbard have experienced low elevation thinning combined with high elevation balance or thickening during 2003 2008 the geodetic mass balance excluding calving front retreat or advance of svalbard s 34 600 km2 glaciers is estimated to be 4 3 1 4 gt y 1 corresponding to an area averaged water equivalent w e balance of 0 12 0 04 m w e y 1 the largest ice losses have occurred in the west and south while northeastern spitsbergen and the austfonna ice cap have gained mass winter and summer elevation changes derived from the same methods indicate that the spatial gradient in mass balance is mainly due to a larger summer season thinning in the west and the south than in the northeast our findings are consistent with in situ mass balance measurements from the same period confirming that repeat track satellite altimetry can be a valuable tool for monitoring short term elevation changes of arctic glaciers

the influence of drifting snow on the location of glaciers on western spitsbergen svalbard on western spitsbergen svalbard the amount of winter precipitation is insufficient to maintain the present day mass balance of the local glaciers additional snow mass must be added to the precipitation to reach the observed accumulation rates of the glaciers it was assumed in previous work that this additional mass is transported onto the glaciers by drifting snow and snow avalanches this study is a first attempt to quantify the amount of snow mass added to the glacier mass balance by wind transported snow the wind field over an area of 60 50 km2 on western spitsbergen was simulated for 24 idealized weather types by a mesoscale meteorological model on a 750 m grid the resulting wind velocities and directions were coupled to a two level snowdrift model the model output clearly shows erosion and accumulation areas in the terrain comparison with the present glacier locations suggests that the glacier accumulation areas coincide with low wind speeds moreover exposed areas with high wind speeds are mostly glacier free in reality thus the wind field and corresponding snowdrift gives an indication of the location of the present glaciers on western spitsbergen

acceleration in thinning rate on western svalbard glaciers 1 geodetic measurements indicate that a number of glaciers in western svalbard ranging in size from 5 1000 km2 are losing mass at an accelerating rate the average thinning rate for midtre lovenbreen the glacier with the best data coverage has increased steadily since 1936 thinning rates for 2003 2005 are more than 4 times the average for the first measurement period 1936 1962 and are significantly greater than presented previously on slakbreen thinning rates for the latest measurement period 1990 2003 are more than 4 times that of the period 1961 1977 thinning of several glaciers along a previously measured airborne lidar profile in wedel jarls land has also increased doubling between the period 1990 1996 and 1996 2002 our results imply an increased sea level contribution from svalbard in addition the mass loss is an important influence on measured rates of rebound on western svalbard and should be factored into analysis of grace results

tertiary evolution of the western tarim basin northwest china a tectono sedimentary response to northward indentation of the pamir salient 1 this paper deals with the tertiary tectonic and sedimentary evolution of the western tarim basin based on an integrated stratigraphic sedimentary structural and tectonic analyses basin evolution is divided into three stages paleogene miocene and pliocene the western tarim basin was the easternmost part of the tethyan realm from late cretaceous to paleogene and marine sedimentation continued into the early miocene miocene development of the western tarim basin was chiefly governed by west kunlun right slip faulting and the simultaneous northward thrusting of the pamir salient and tianshuihai terrane yecheng subbasin developed as a pull apart basin owing to synchronous activity of the west kunlun and the shache yangdaman right slip faults hotan foreland basin formed in response to northward displacement of the tianshuihai terrane and another might have developed in front of the advancing pamir salient in the miocene basinward thrusting became predominant in the orogenic belts adjacent to the western tarim basin in the pliocene north directed displacement and uplift of the tiklik thrust terrane fragmented the preexisting hotan foreland basin and collision of the pamir with the southern tian shan deformational fronts caused complete destruction of the miocene pamir foreland basin eastward displacement of the qimugen fold thrust system led to flexural subsidence of the yecheng subbasin in the pliocene kashi subbasin developed as part of the southern tian shan foreland basin and was controlled by the eastern pamir as well a tectonic scenario is proposed to illustrate complicated interplay of the western tarim basin with its peripheral orogens in the tertiary

global glacial isostasy and the surface of the ice age earth the ice 5g vm2 model and grace abstract the 100 kyr quasiperiodic variation of continental ice cover which has been a persistent feature of climate system evolution throughout the most recent 900 kyr of earth history has occurred as a consequence of changes in the seasonal insolation regime forced by the influence of gravitational n body effects in the solar system on the geometry of earth s orbit around the sun the impacts of the changing surface ice load upon both earth s shape and gravitational field as well as upon sea level history have come to be measurable using a variety of geological and geophysical techniques these observations are invertible to obtain useful information on both the internal viscoelastic structure of the solid earth and on the detailed spatiotemporal characteristics of glaciation history this review focuses upon the most recent advances that have been achieved in each of these areas advances that have proven to be central to the construction of the refined model of the global process of glacial isos

horizontal and vertical velocities derived from the ids contribution to itrf2014 and comparisons with geophysical models in the context of the 2014 realization of the international terrestrial reference frame the international doris doppler orbitography radiopositioning integrated by satellite service ids has delivered to the iers a set of 1140 weekly sinex files including station coordinates and earth orientation parameters covering the time period from 1993 0 to 2015 0 from this set of weekly sinex files the ids combination centre estimated a cumulative doris position and velocity solution to obtain mean horizontal and vertical motion of 160 stations at 71 doris sites the main objective of this study is to validate the velocities of the doris sites by comparison with external models or time series horizontal velocities are compared with two recent global plate models geodvel 2010 and nnr morvel56 prior to the comparisons doris horizontal velocities were corrected for global isostatic adjustment from the ice 6g vm5a model for more than half of the sites the doris horizontal velocities differ from the global plate models by less than 2 3 mm yr 1 for five of the sites arequipa dionysos gavdos manila and santiago with horizontal velocity differences with respect to these models larger than 10 mm yr 1 comparisons with gnss estimates show the veracity of the doris motions vertical motions from the doris cumulative solution are compared with the vertical velocities derived from the latest gps cumulative solution over the time span 1995 0 2014 0 from the university of la rochelle solution at 31 co located doris gps sites these two sets of vertical velocities show a correlation coefficient of 0 83 vertical differences are larger than 2 mm yr 1 at 23 percent of the sites at thule the disagreement is explained by fine tuned doris discontinuities in line with the mass variations of outlet glaciers furthermore the time evolution of the vertical time series from the doris station in thule show similar trends to the grace equivalent water height

recent contributions of glaciers and ice caps to sea level rise satellite measurements of earth s gravity field show that the mass loss of glaciers and ice caps contributed to sea level rise by approximately 0 4 millimetres per year between 2003 and 2010 the extent to which mass loss from ice covered land areas contributes to sea level rise is not known accurately in part because previous global estimates use different techniques for glaciers ice caps and ice sheets the gravity recovery and climate experiment grace satellite has provided monthly measurements of the global gravity field since 2002 using grace data jacob et al assess regional mass loss between 2003 and 2010 and conclude that mass loss from ice covered land areas contributed almost 1 5 mm per year to the sea level rise estimated mass loss from the high mountains of asia was negligible in contrast to some other reports glaciers and ice caps gics are important contributors to present day global mean sea level rise1 2 3 4 most previous global mass balance estimates for gics rely on extrapolation of sparse mass balance measurements1 2 4 representing only a small fraction of the gic area leaving their overall contribution to sea level rise unclear here we show that gics excluding the greenland and antarctic peripheral gics lost mass at a rate of 148 30 gt yr 1 from january 2003 to december 2010 contributing 0 41 0 08 mm yr 1 to sea level rise our results are based on a global simultaneous inversion of monthly grace derived satellite gravity fields from which we calculate the mass change over all ice covered regions greater in area than 100 km2 the gic rate for 2003 2010 is about 30 per cent smaller than the previous mass balance estimate that most closely matches our study period2 the high mountains of asia in particular show a mass loss of only 4 20 gt yr 1 for 2003 2010 compared with 47 55 gt yr 1 in previously published estimates2 5 for completeness we also estimate that the greenland and antarctic ice sheets including their peripheral gics contributed 1 06 0 19 mm yr 1 to sea level rise over the same time period the total contribution to sea level rise from all ice covered regions is thus 1 48 0 26 mm 1 which agrees well with independent estimates of sea level rise originating from land ice loss and other terrestrial sources6

earthquakes related to active salt doming near kulyab tadjikistan ussr in the region near kulyab tadjikistan hundreds of shallow earthquakes with magnitudes greater than 2 have been reported in soviet yearly catalogs since 1964 this area appears as a well defined cluster of activity distant from the line of epicenters that defines the gissar kokshal seismic zone to the north of the pamir ranges the geology of this region is dominated by the presence of numerous salt domes surrounded by neogene and quaternary continental deposits the spatial relationship between these earthquakes and the salt domes suggests that the two phenomena may be related moderate earthquakes m 5 occurred in 1972 and 1973 and intensities of surface shaking greater than mm 6 were reported from earthquakes in 1937 1952 1969 1972 1973 and 1978 the earthquake on 2 april 1973 and its aftershocks were located in a region where no salt domes have been mapped at the surface however a buried salt diapir has been mapped at depth by geophysical means these earthquakes may result from active salt diapirism at depth the mechanism for producing this seismicity could be either the active fracturing of the cap rock by the rising diapir or the concentration of tectonic stresses in the thinned section above and adjacent to the diapir the salt related earthquakes may produce lower frequency radiation than other events of the same size

glacier change from the early little ice age to 2005 in the torngat mountains northern labrador canada abstract the glaciers of the torngat mountains of northern labrador are the southernmost of the canadian arctic and the easternmost of continental north america currently 195 small mountain glaciers cover an area in excess of 24 km2 confined mostly to small cirques and upland depressions using a combination of field and remote sensing methods this study reconstructs and dates the areal extent of torngat glaciers at their neoglacial maximums enabling the first assessment of regional glacier change over the past several centuries mapped glacier paleomargins n 165 are compared to current 2005 glaciers and ice masses showing a 52 5 reduction in glacier area with at least 11 former glaciers altogether disappearing glacier change is spatially homogenous and independent of most geographic and topographic factors however glacier elevation and glacier size mitigated total change previously established lichen growth stations were revisited and growth rates recalculated based on 30 year long records enabling the construction of locally derived low and high altitude lichen growth curves using growth rates and in situ lichen measurements the retreat from maximum neoglacial moraine extents are suggested to have occurred between a d 1581 and 1673 these findings indicate a similar magnitude of post lia retreat to mountain glaciers elsewhere yet a much earlier timing 200 years of retreat than other glaciers in the eastern canadian arctic though no definitive answer explaining this discrepancy is presented evidence suggests that regional climate dynamics and the importance of solar radiation for torngat glaciers may play an important role in local glacierization

greenland uplift and regional sea level changes from icesat observations and gia modelling we study the implications of a recently published mass balance of the greenland ice sheet gris derived from repeated surface elevation measurements from nasa s ice cloud and land elevation satellite icesat for the time period between 2003 and 2008 to characterize the effects of this new high resolution gris mass balance we study the time variations of various geophysical quantities in response to the current mass loss they include vertical uplift and subsidence geoid height variations global patterns of sea level change or fingerprints and regional sea level variations along the coasts of greenland long wavelength uplifts and gravity variations in response to current or past ice thickness variations are obtained solving the sea level equation which accounts for both the elastic and the viscoelastic components of deformation to capture the short wavelength components of vertical uplift in response to current ice mass loss which is not resolved by satellite gravity observations we have specifically developed a high resolution regional elastic rebound er model the elastic component of vertical uplift is combined with estimates of the viscoelastic displacement fields associated with the process of glacial isostatic adjustment gia according to a set of published ice chronologies and associated mantle rheological profiles we compare the sensitivity of global positioning system gps observations along the coasts of greenland to the ongoing er and gia in notable contrast with past reports we show that vertical velocities obtained by gps data from five stations with sufficiently long records and from one tide gauge at the gris margins can be reconciled with model predictions based on the ice 5g deglaciation model and the er associated with the new icesat derived mass balance

dynamics of mercury species in surface sediments of a macrotidal estuarine coastal system adour river bay of biscay estuarine and coastal surface sediments from the adour estuary and adjacent coastal area south bay of biscay have been investigated to establish mercury species variability in a macrotidal system submitted to contrasted seasonal river discharges and downstream urbanisation surface sediments were sampled during three campaigns in the major sediment deposits of the adour estuary and at selected discharge points concentrations of hg2 and mehg in adour estuarine sediments average 1600 and 1 3 pmol g 1 and range from 2 to 7300 pmol g 1 and from 0 5 to 8 0 pmol g 1 respectively the concentrations of inorganic ionic mercury hg2 and monomethylmercury mehg in the surface sediments display large seasonal variation being one order of magnitude higher in june 2001 for hg2 and in october 2000 for mehg the results show that hg2 can be accumulated in the estuarine sediments after seasonal river inputs and both remobilised and methylated during dry period mercury species concentrations in coastal sediments collected in june 2001 assessed the impact of estuarine inputs on the nearby coastal area except direct anthropogenic discharge points the variability and transfer of hg2 and mehg in surface sediments of the whole estuarine coastal macrotidal system can be depicted by simple geochemical parameters of the bulk sediments such as grain size distribution organic carbon and total sulphur

structure and changing dynamics of a polythermal valley glacier on a centennial timescale midre lovenbreen svalbard hambrey michael murray t glasser n f hubbard a 2005 structure and changing dynamics of a polythermal valley glacier on a centennial timescale midre lovenbreen svalbard journal of geophysical research 110 pp 1 19 rae2008