localized basal freezing within george vi ice shelf antarctica hobbs pool is an area of thin ice shelf situated within george vi ice shelf antar ctica thicker ice shelf surro unding hobbs pool isolates the upper 155 m of the water column from water lying at the same depth else where under the ice shelf summer melt water lakes drain through crevasses at hobbs pool forming a 155 m thick layer of low s alinity water close to its freezing point colder and more saline water in the lower part of this layer leads to in situ freezing of fresher water lying above it below 155 m depth the water tempera ture and salinity are linearly related by basal melting which is observed elsewhere under the ice shelf the surface ice shows areas of defo rmation and deposits of subglacial rock debris which may result from upward particle paths in the area the raising of subgl acial rock debris on to the ice surface may provide a mechanism for the transp ort of erratics across the ice shelf to alexa nder island from the base of palmer land glaciers

reverse water level change during interference slug tests in fractured rock 1 reverse water level responses in monitoring wells are widely known during pumping tests where they are recognized as the noordbergum or rhade effects and a similar response was observed in many of the 100 interference slug tests conducted at a well field near clemson south carolina the reverse water level effect is characterized by a drop in pressure head by 1 cm to several centimeters and it occurs in the first 10 100 s of the test the reverse response is followed by a rise and fall of pressure head that is typical of slug in tests the reverse water level response is highly repeatable and it increases when the pressure used to create the slug test is increased a conceptual model recognizes that opening displacement of the fracture wall can cause a pressure drop even when the pressure increases in the wellbore the conceptual model is supported by a closed form analytical solution and a numerical model that couple fluid pressure and deformation in a fracture characteristics of the reverse water level response are sensitive to properties of the fracture system and enveloping formation parameter estimation methods can be used to invert theoretical analyses and use the reverse response to improve the characterization of fractured rock aquifers

storage change in a flat lying fracture during well tests 1 the volume of water released from storage per unit head drop per volume of an rev is a basic quantity in groundwater hydrology but the details of the process of storage change in the vicinity of a well are commonly overlooked we characterize storage change in a flat lying fracture or thin sedimentary bed through the apparent hydraulic compliance cf the change in aperture of the fracture or thickness of the layer per unit change in pressure the results of theoretical analyses and field measurements show that cf increases with time near the well during pumping but it drops suddenly and may become negative at the beginning of recovery during a well test profiles of cfincrease with radial distance from a well but they are marked by a sharp increase and a sharp decrease at the edge of the region affected by the wellbore pressure transient the conventional view in groundwater hydrology is that storage change at a point is proportional to the local change in pressure which requires that the hydraulic compliance is uniform and constant it appears that this conventional view is a simplification of a process that varies in both space and time and can even take on negative values this simplification may be a source of uncertainty when interpreting well tests and extensometer records or predicting long term well performance

hydromechanical behavior of a deformable rock fracture subject to normal stress lbl 12297 preprint to be published in the journal of geophysical research hydromechanical behavior of a deformable rock fracture subject to normal stress y w tsang and p a witherspoon january 1981 two week loan copy this is a library circulating copy which may be borrowed for two weeks for a personal retention copy call tech info diu is ion ext 6782 prepared for the u s department of energy under contract w 7405 eng 48

ash deposits in hayonim and kebara caves israel macroscopic microscopic and mineralogical observations and their archaeological implications abstract a study of the hearths and ash layers preserved in hayonim and kebara caves israel showed that they are composed of one or several different minerals these include the polymorph of caco3 calcite a variety of phosphate minerals and a suite of siliceous minerals the major component of the latter are siliceous aggregates that are present in wood detailed studies of the mineral associations in these fossil ash layers as well as in fresh wood ash using optical and scanning electron microscopy in the back scattered electron mode together with elemental analyses showed that ash in these caves undergoes a series of diagenetic changes the best preserved ash layers resemble fresh ash and are composed mainly of calcite with minor amounts of siliceous minerals the calcite reacts with phosphate rich solutions to form carbonated apatite and with time the latter dissolves and a variety of other phosphate containing minerals form with each diagenetic change some of the more soluble minerals are lost and ultimately only the ash derived siliceous minerals remain in both caves there are local accumulations of such siliceous minerals that are metres thick in fact ash derived minerals in general are major components of the sediments in both kebara and hayonim caves their diagenesis involves a hugh reduction in volume which in turn may have important effects on the geological structures and stratigraphy of the sediments the changing mineralogy of the sediments due to diagenesis complicates the use of present day estimates of radiation content of the sediments for correcting age estimates by thermoluminescence and electron spin resonance finally the presence of the relatively stable ash derived siliceous minerals in a sedimentary layer in other caves could be a useful means of identifying the presence of ash in other archaeological sites where macroscopic hearth features are absent

retreat of northern margins of george vi and wilkins ice shelves antarctic peninsula the george vi and wilkins ice shelves are considered at risk of disinteg ration due to a regional atmospheric warming trend on the antarctic peninsula retreat of the northern margin of the george vi ice shelf has been observed previously but the wilkins ice shelf was thought to be stable we investigated the positions of the northern fronts of these shelves from the literature and looked for changes on 1974 landsat and 1992 and 1995 european remote sensing satellite ers synthetic aperture radar images our investigation shows that the northern george vi ice shelf lost a total of 906 km 2 between 1974 and 1992 and an additional 87 km2 by 1995 the northern margin of the wilkins ice shelf lost 796 km2 between 1990 and 1992 and another 564 km2 between 1992 and 1995 armadas of tabular icebergs were visible in front of this shelf in the ers images these two ice shelves mark the southern most documented conspicuous retreat of ice shelf margins

microstratigraphic and multi analytical evidence for advanced neanderthal pyrotechnology at abric romani capellades spain abstract the complexity of social behaviour by neanderthal communities is consolidated by illustrating the sophistication of fire linked activities in their home based contexts this was achieved by relating the microfacies analysis of cultural deposits to combustion structures at the abric romani capellades spain the geometry and nature of cultural microfacies from a selection of hearths and their surrounding empty areas were characterized in thin sections the related bulk fraction from the distinctive individual microstrata was extracted water sieved and examined under the binocular microscope the selective micro sampling was performed from the collection of undisturbed blocks in combustion structures of layer j 1995 excavation the procedure was applied to combustion structures from the lower layer o 2009 excavation the integrated micromorphological observation and binocular sorting allowed identification of a similar assemblage of components that are closely linked to distinctive anthropic microfacies individual grains were characterized by esem edax x ray diffraction and raman spectrometry x ray fluorescence analysis was performed on the host matrix the specific association of remarkable components cultural microfacies is identical for the combustion structures of layers o and j the four groups components identified comprise carbonaceous polymorphs allochthonous mineral clasts organo phosphatic compounds and native metals the phase association of organic and mineral phases allowed recognition of a common natural precursor rich in hydrocarbon species and metallic compounds that were probably extracted from a miocene source microscale analysis in thin sections linked the combustion microfacies to the transformation contexts of the metal rich carbonaceous precursors heat resistant polymers and graphitic components associated with wood ash are suggested to trace pyrolitic residues from flaming combustion the intimate mixing of the metal rich carbonaceous polymorphs to finely crushed heated bones allowed identification of pyrogenic transformations of the fossil fuel with fresh biomass analysis at microscale in thin sections linked the processed by products to finely prepared and meticulously consolidated surfaces showing distinctive colours yellow brown blue green red white and black the repeated surface preparation and their exceptional preservation at microscales illustrate the great concern of neanderthal occupants for maintaining the long term memory of their carefully designed home space the recognition of advanced pyrotechnology by using fossil fuels for lighting firing spatial design colouring in the combustion structures of abric romani incites speculation on the exceptional social status of this home based camp site further development of the microfacies multi analytical analysis should more deeply penetrate the social sophistication of neanderthal communities

hydromechanical interactions in a fractured carbonate reservoir inferred from hydraulic and mechanical measurements hydromechanical coupled processes in a shallow fractured carbonate reservoir rock were investigated through field experiments coupled with analytical and numerical analyses the experiments consist of hydraulic loading unloading of a water reservoir in which fluid flow occurs mainly inside a heterogeneous fracture network made up of vertical faults and bedding planes hydromechanical response of the reservoir was measured using six pressure normal displacement sensors located on discontinuities and two surface tiltmeters a dual hydraulic behavior was characterized for low permeability bedding planes well connected to highpermeability faults displacement responses show high variability nonlinear changes sometimes with high frequency oscillations and a large scattering of magnitudes initial normal stiffnesses and effective normal stresses along fault planes were estimated in the field by interpreting pressure normal displacement relations with a nonlinear function between effective normal stress and normal displacement two dimensional discontinuum modeling with transient fluid flow was performed to fit measurements during hydraulic loading tests results show that the hydromechanical behavior of the reservoir is restored if a high stiffness contrast is allocated between low and high permeability discontinuities thus a dual permeability network of discontinuities will likely also be a contrasting stiffness network in which the deformation of major flow conducting discontinuities is significantly influenced by the stiffness of the surrounding less permeable discontinuities

water table effects on the measurement of earth strain abstract forced changes in the water head within a granite penetrating borehole were found to induce anomalously large free surface strains and tilts in the vicinity of the hole this deformation is shown to be due to fluid pressure induced changes in the aperture of a compliant hydraulically conductive fracture at a depth of 100 m and a quantitative analysis of the deformation data is performed to recover fracture characteristics the importance of the effect for secular earth strain measurements is discussed in the light of the ubiquitous nature of both water table fluctuations and fractures in the shallow crust

bone needle fragment in lgm from the shizitan site china archaeological evidence and experimental study an eyed bone needle fragment found in shizitan 29 site shanxi province dated to ca 23 26 ka cal bp is one of the early needles with a precise stratigraphic context and date among the open air palaeolithic sites in north china although the needle was found broken based on microwear observation and experiments in making and using bone needles we conclude that it had been used for sewing further archaeological evidence including a sandstone needle shaping stone drilling tools perforated ornaments and microscopic evidence of thread support the presence of a bone needle at the shizitan 29 site it was the same type as the bone needles used in siberia during the late pleistocene and the use of needles at shizitan was one of the strategies for making warm clothes to adapt to the coming of the last glacial maximum lgm 24 000 18 000 cal bp

palaeoecology of neanderthals during dansgaard oeschger cycles in northeastern iberia abric romani from regional to global scale abstract the sequence from abric romani has provided several palaeoecological studies this paper presents a synthesis of the results yielded by palynology including the data from the entire non excavated deposits and the data obtained through the study of large mammals micromammals herpetofauna and anthracology from the excavated layers the palaeobotanical studies show that the sequence is mainly related to pine forests and near or within these dominant forests there were smaller plant formations and or secondary species with a mediterranean and or atlantic character nevertheless continuous forest did not dominate the entire region the fauna occupying the territory indicate open spaces in which seasonal grasslands proliferated dry assemblages in sunny areas and humid ones in mountain shadows the non excavated archaeological layers correspond to mis 4 initially characterized by temperate and humid conditions and thereafter cool and humid until hs 6 and mis 3 afterwards at the beginning of the mis 3 the dansgaard oeschger cycles 1500 yr rapid and abrupt climatic changes occurred during the deposition of the archaeological levels o n m l k and j later these events were interrupted by a cold and dry phase between ca 49 and 47 ka bp which affected levels ja i and h culminating with hs 5 finally this cold episode was followed by the hengelo interstadial or do 12 characterized by a temperate and humid climate identified in levels e and d

use of in situ fiber optic sensors to characterize highly heterogeneous elastic displacement fields in fractured rocks fractured and porous rock masses undergo complex deformations relating to geological mechanical and hydrological processes such as plate tectonics earthquakes earth tides and the engineering design of structures in and on rock masses the distribution of stresses in the earth s crust governs the deformation field within and on the surface of geological systems in turn the rock stiffness the presence of faults and others discontinuities the topographical variations the pore pressures body forces and tectonic forces affect the stresses distribution in the earth 1 under basic loading or unloading such as overburden loads tectonics forces underground excavation fractured rock masses generally deform according to a complex mechanical or hydromechanical behavior 1 2 displacements are first localized along pre existing discontinuities and then propagate within the porous rock matrix 2 3 along discontinuity planes the displacements are generally of high magnitude and instantaneous while displacements of the rock matrix are generally of lesser magnitude and slower thus in active zones deformation changes within fractured rocks present a large frequency range and can be both static and dynamic static changes involve static deformations that can be produced by volcanoes tectonic sources hydrologic effects while dynamic changes are best represented by seismic waves produced by earthquake sources 4 geodesy has been the classical field measurements method for static changes and seismology for

circulation and melting beneath george vi ice shelf antarctica introduction george vi ice shelf sandwiched between the western coast of palmer land and the eastern coast of alexander island is the largest and most studied of the west antarctic peninsula ice shelves it covers an area of approximately 25 000 km2 and is underlain by circumpolar deep water cdw with temperatures in excess of 1oc giving rise to rapid basal melting bishop and walton 1981 lennon et al 1982 the maximum ice thickness of about 500 m occurs about 70 km from the southern ice front where a ridge of thick ice extends across george vi sound near 70ow see figure 1 effectively dividing the upper water column into northern and southern regions the northern ice front which faces marguerite bay appears to be near the geographical limit of ice shelf viability and has undergone a gradual retreat in recent decades lucchitta and rosanova 1998 a timeframe over which much of the nearby wordie ice shelf disintegrated doake and vaughan 1991 there is extensive surface melting over the northern parts of the ice shelf and much of the ice column near the northern ice front appears to be temperate paren and cooper 1986 conditions in the south where the ice front faces into ronne entrance are colder and the ice front position appears to be steady the vast majority of the flow into the ice shelf comes from palmer land but basal melting is sufficient to remove most of this so that the ice is derived almost exclusively from local accumulation by the time it reaches the ice fronts potter et al 1984 there is some evidence at the margins of the ice shelf to suggest that it may have disappeared completely during the early holocene before reforming sugden and clapperton 1981 bentley et al 2005

continual fire making by hominins at gesher benot ya aqov israel this paper presents the culmination of an extensive study of fire use at the early and early middle pleistocene site of gesher benot ya aqov using software available in the gis package we have examined the spatial distribution of burned and unburned flint microartifacts from eight acheulian archaeological horizons the results of this study demonstrate that the burned microartifacts are never evenly distributed and dense concentrations are observed the circumstances that introduced these burned flint artifacts to the archaeological layers are examined suggesting that anthropogenic rather than natural fires are responsible for the observed patterns as the evidence for the use of fire is recorded throughout the long stratigraphic sequence it seems that fire was continually used by the acheulian hominins of the site this repetitive use of fire indicates that the hominins of gesher benot ya aqov had a profound knowledge of fire making enabling them to make fire at will

a portable borehole extensometer and tiltmeter for characterizing aquifers 1 the solid skeleton of an aquifer moves in response to changes in water pressure barometric pressure earth tides and other factors and measuring these movements can help characterize aquifers a device for measuring the vertical displacement and horizontal shear or tilt at the same time and place has been developed by combining a tiltmeter and extensometer on a frame that can be temporarily anchored to borehole walls the device can resolve displacements on the order of 10 8 m and tilts on the order of 10 8 rad during a 4 h long pumping test in fractured gneiss the rock contracted by 3 m in response to 2 m of drawdown a compliance of roughly 1 5 m of displacement meter of head change 1 5 10 10 m pa tilt of 10 s of rad to the southwest occurred during pumping and both the displacement and the tilt returned during recovery the tilt signal is repeatable during sequential tests and it changes in magnitude with depth it can be explained by a fracture zone that strikes roughly ew and dips to the south semidiurnal tilts of roughly 0 1 rad occur during ambient conditions at periods of the o1 and m2 earth tides diurnal displacements of several tens of nanometers are associated with ambient fluctuations in water level when barometric pressure changed by several 100 pa increasing barometric pressure causes water level to fall but elevates the total pressure in the well this correlates with dilational displacement while falling total pressure correlates with contraction during ambient conditions

field evaluation of the hydromechanical behavior of flat lying fractures during slug tests summary slug tests were conducted at depths of 20 50 m in a fractured gneiss and axial displacements were measured along the borehole with a portable extensometer in order to evaluate the feasibility of combining pressure and displacement measurements to improve the characterization of fractured rock displacements on the order of microns occurred during slug tests when maximum head changes were on the order of meters maximum displacement lagged behind the maximum head and the signals at a given location were repeatable to within reasonable tolerances tests were conducted at 12 packed off depth intervals in a borehole and the signals from each interval were distinctly different from those at other depths parameter estimation techniques were used with a hydromechanical model to interpret the field results and the findings show that there are three transmissive zones in the borehole and the compliance of the fractures generally decreases with depth the inversion also highlights the importance of considering heterogeneities in the vicinity of the well bore when interpreting hydromechanical tests zones of leakage and blockage in the fractures were predicted in the vicinity of the well bore and their presence had a significant effect on the displacement signals

ocean interactions with the base of amery ice shelf antarctica using a two dimensional ocean thermohaline circulation model we varied the cavity shape beneath amery ice shelf in an attempt to reproduce the 150 m thick marine ice layer observed at the gi ice core site most simulations caused melting rates which decrease the ice thickness by as much as 400 m between grounding line and g1 but produce only minor accumulation at the ice core site and closer to the ice front changes in the seafloor and ice topographies revealed a high sensitivity of the basal mass balance to water column thickness near the grounding line to submarine sills and to discontinuities in ice thickness model results showed temperature salinity gradients similar to observations from beneath other ice shelves where ice is melting into seawater modeled outflow characteristics at the ice front are in general agreement with oceanographic data from prydz bay a freshwater flux across the grounding line derived from melting beneath the grounded ice sheet would have to be anomalously large to produce the basal marine ice layer and account for the ice shelf water outflow we concur with morgan s inference that the g 1 core may have been taken in a basal crevasse filled with marine ice this ice is formed from water cooled by ocean ice shelf interactions along the interior ice shelf base

environmental reconstruction and dating of shizitan 29 shanxi province an early microblade site in north china global cooling during the last glacial maximum lgm posed significant challenges to peoples living in northern eurasia using micromorphology pollen and non pollen palynomorphs npp and faunal analyses this study reconstructs the local paleoenvironmental contexts of repeated ephemeral occupations at shizitan 29 in shanxi province north china across the lgm from ca 28 to 18 ka cal bp followed by a gap until a final occupation ca 13 5 ka cal bp among the significant finds at shizitan 29 are remains of 285 hearths and a rich lithic assemblage that contains the earliest radiocarbon dated evidence for microblades in china appearing first in layer 7 the environmental data show that the low mountains and tributary river valleys of the yellow river in the loess plateau provided abundant sources of water and food in spite of environmental fluctuations microblade producing groups repeatedly visiting this locality survived severe climate change by making use of fire selective herbivore hunting processing plant foods with grinding stones and symbolic ornamentation such as ostrich shell beads npp data also indicate the potential presence of flax and other fiber processing the shizitan 29 data demonstrate how humans adapted to challenging local conditions throughout the lgm allowing them to stay within this northerly region without migrating to warmer southern latitudes

measurements and interpretations of tilt strain gauges in seismically active areas abstract an overview of different aspects of deformation measurements is given an introduction to the general theory of point crustal deformations with an application to the stress strain relations at the earth surface is made the instrumentation used in crustal deformation measurements is briefly explained emphasizing different constructions of tilt and strainmeters the problems connected with the housing of the instruments i e the cavity and topography effects and with the ambient noise factors as the hydrological and pressure effects are discussed the last part of the paper is concerned with the relation between deformation measurements and seismic events both from a theoretical and observational standpoint a number of examples are shown that report on pre co and post seismic and the secular term deformation in different areas of the world

archaeological soil and pollen analysis of experimental floor deposits with special reference to butser ancient farm hampshire uk archaeological stratigraphies that may contain floors are often encountered for more than a decade soil micromorphologists working on archaeological sequences have benefited from having access to reference thin sections of ethnoarchaeological and experimental floors including those from the floors of iron age houses reconstructed by the late dr peter reynolds at butser ancient farm hampshire uk this paper reports upon experimental studies mainly carried out at butser during 1990 95 and their suggested application to microstratigraphic and microfacies analysis of occupation sites sampling at butser in 1990 was very much a rescue operation nevertheless fundamental differences in soil micromorphology were found between domestic house beaten floor deposits and those formed in a stable these differences were also reflected in the parallel study of pollen from these deposits with microchemical analyses helping to explain anomalous pollen preservation in the unsuitable soil at butser the limited bulk chemical study produced less clear results but when compared with findings from some roman and early medieval sites in london showed that the chemical trends hinted at butser are probably replicated in some ancient floors a preliminary interdisciplinary study of samples from the london guildhall clearly suggested the potential of such microstratigraphical and microfacies analyses and intimates at the potential of attaining rigorous consensus interpretations stable floor deposits are both organic and phosphate rich with homogeneous soil micromorphological and pollen characteristics beaten floors are much more mineralogenic and heterogeneous in terms of their microfabric and pollen that also indicate trampling in of a wide variety of allocthonous materials the last commonly responsible for raised magnetic susceptibility at archaeological sites these findings prove the worth of the ethnoarchaeological simulations carried out at the moel y gar stable and domestic pimperne house this microfacies approach is viewed as complementary to site reconstruction through macrofossil analysis of beetles and plant remains especially where sites are being investigated at the microstratigraphic level the phosphate content of stabling deposits may allow preservation of pollen in what may otherwise be deemed unsuitable material as demonstrated at butser

oceanic and atmospheric forcing of early holocene ice shelf retreat george vi ice shelf antarctica peninsula we use lake sediment records from an epishelf lake on alexander island to provide a detailed picture of the holocene history of george vi ice shelf gvi is core analyses included micropaleontology diatoms foraminifera stable isotope 18o 13c geochemistry total organic carbon toc total nitrogen tn c n ratios and grain size analyses these data provide robust evidence for one period of past ice shelf absence during the early holocene the timing of this period has been constrained by 10 ams 14c dates performed on mono specific foraminifera samples these dates suggest that gvi is was absent between c 9600 cal yr bp and c 7730 cal yr bp this early holocene collapse immediately followed a period of maximum holocene warmth that is recorded in some antarctic ice cores and coincides with an influx of warmer ocean water onto the western antarctic peninsula ap shelf at c 9000 cal yr bp the absence of a currently extant ice shelf during this time interval suggests that early holocene ocean atmosphere variability in the ap was greater than that measured in recent decades

developing sediment geochronologies for high latitude continental shelf deposits a radiochemical approach during january and february of 1986 47 box cores and 55 piston cores were collected from the bransfield strait gerlache strait and marguerite bay antarctica apparent sediment accumulation rates established for 100 yr time scales with excess 210pb chronologies range from 0 08 to 0 34 cm yr in the bransfield strait 0 15 to 0 51 cm yr in gerlache strait and from 0 10 to 0 27 cm yr in marguerite bay for the antarctic peninsula continental shelf 137cs appears to have a limited usefulness in assessing the effects of deep sediment mixing by benthic fauna on seabed excess 210pb profiles because the observed activities for the regions examined are close to counter detection limits conventional 14c ages of surface sediments from the peninsula region range from 1370 to 2820 yr the spatial variations in the conventional 14c surface ages are thought to be influenced predominantly by inputs of older eroded sediment from lateral transport current winnowing mass wasting and or a variable carbon source on a 1000 yr time scale 14c measurements of five piston cores from the bransfield strait yielded sediment accumulation rates ranging from 0 06 to 0 49 cm yr these data support the assertion by nelson 1988 that the excess 210pb sediment accumulation rates range of 0 08 to 0 34 cm yr for this region represent true rates the two sediment accumulation rates of 0 01 and 0 08 cm yr for the gerlache strait are significantly lower than the observed apparent 210pb accumulation rates mean 0 27 0 12 cm yr for this region likewise two piston cores from marguerite bay yielded 14c sediment accumulation rates of 0 02 and 0 05 cm yr which also are considerably lower than the excess 210pb apparent accumulation rates mean 0 17 0 06 cm yr for this area the one dimensional advection diffusion equation of goldberg and koide geochim cosmochim acta vol 51 1962 was solved simulatneously with 210pb and 14c data for bc18 and bc113 to resolved the effects of sediment mixing and accumulation in bransfield strait and marguerite bay box core samples respectively this model indicates that 210pb and 14c sediment accumulation rates agree within a factor of 2 in the bransfield strait whereas in marguerite bay the apparent 210pb accumulation rates may be as much as an order of magnitude too high in the southern high latitude environments of the antarctic peninsula radiocarbon measurements in the seabed are a better approach than 210pb for establishing accurate rates of sediment accumulation the 14c chronologies when coupled with 210pb data provide more reliable assessments of biological deep mixing and sediment accumulation rates than do excess 210pb data coupled with measurements of bomb produced 137cs the sediment accumulation rates for both 100 yr and 1000 yr time scales tend to decrease southward from the bransfield strait to marguerite bay which is consistent with glacial marine sedimentation processes as modulated by climate for the western antarctic peninsula seabed measurements of 210pb 137cs and 14c also provides valuable insights on water circulation and upwelling atmospheric inputs and sediment depositional processes for the antarctic peninsula region

response of fractured rock subject to fluid injection part i development of a numerical model abstract the selection and development of a numerical model used to investigate the response of fractured rock to injection are described the distinct element method was chosen on the basis of its ability to represent explicitly the fractures and to couple the mechanical deformation to the fluid flow the numerical model was used to simulate fluid injection from a single well into each of four basic model reservoirs the results of these simulations form the basis of the interpretation given in parts ii and iii

thirty year land elevation change from subsidence to uplift following the termination of groundwater pumping and its geological implications in the metropolitan taipei basin northern taiwan several levelling routes in the metropolitan taipei basin have been repeatedly conducted during the past decades mainly in order to monitor the anthropogenic ground subsidence due to massive pumping of groundwater we analysed the levelling data released from government and investigated the rate of ground level change from 1975 to 2003 which postdate the massive groundwater exploitation in taipei area based on the contour maps created from the levelling data of 406 benchmarks the overall subsidence rate in the taipei basin gradually decreased since 1975 and around 1989 the basin switched to slight uplift throughout a large part of the basin three mechanisms are proposed to be responsible for the observed land elevation changes including shallow soil compaction deformation within aquifer and tectonic subsidence the trend of the ground level change in 1975 2003 essentially demonstrated the effects of natural recharge to previously depleted aquifers and is explained by the hydro mechanical coupling of aquifer materials i e elastic rebound to the rising piezometric level the rate of shallow soil compaction is estimated about 1 8 mm yr throughout the basin according primarily to the shallow clay thickness asymmetric tectonic subsidence related to the shanchiao fault was estimated to be 1 75 mm yr and 0 9 mm yr in the western part and the central part of the basin respectively by subtracting the components of the soil compaction and tectonic subsidence from the surface land elevation change the rebound of aquifer strata was estimated to be about 6 7 cm and 16 cm in western margin and central taipei respectively the amount of rebound is approximately 10 in magnitude comparing to the amount of previous anthropogenic subsidence due to massive groundwater pumping totally about 2 m 2007 elsevier b v all rights reserved

the dakhleh glass product of an impact airburst or cratering event in the western desert of egypt impact cratering is a ubiquitous geological process on the terrestrial planets meteorite impact craters are the most visible product of impact events but there is a growing recognition that large aerial bursts or airbursts should occur relatively frequently throughout geological time in this contribution we report on an unusual impact glass the dakhleh glass dg which is distributed over an area of 400 km 2 of the dakhleh oasis egypt this region preserves a rich history of habitation stretching back to over 400 000 years before the emergence of homo sapiens we report on observations made during recent fieldwork and subsequent analytical analyses that strengthen previous suggestions that the dg formed during an impact event the wide distribution and large size of dg specimens up to 50 cm across the chemistry e g cao and al2o3 contents up to 25 and 18 wt respectively the presence of lechatelierite and burnt sediments and the inclusion of clasts and spherules in the dg is inconsistent with known terrestrial processes of glass formation the age and other textural characteristics rule out a human origin instead we draw upon recent numerical modeling of airbursts to suggest that the properties of dg coupled with the absence of a confirmed crater can best be explained by melting of surficial sediments as a result of a large airburst event we suggest that glass produced by such events should therefore be more common in the rock record than impact craters assuming that the glass formed in a suitable preserving environment

linking thermal hydrological and mechanical processes in fractured rocks abstract in this paper an overview is presented of coupled processes linking thermo hydro mechanical thm effects in fractured rocks a formulation is first presented to show the linkage mathematically which can be used as a basis for numerical solutions and for further developments two simple examples of hydromechanical hm and thermo hydro mechanical thm coupled processes are discussed to convey physical insight into such couplings finally three large scale long term experiments currently under way are described these are being conducted specifically to study coupled processes in situ

models of glaciomarine sedimentation and their application to the interpretation of ancient glacial sequences abstract this paper argues that glaciomarine environments can be regarded as special glacially influenced types of continental margin environments e g continental shelf slope rise and basin plain knowledge of the stratigraphic architecture and typical sedimentary sequences of non glacial margins is becoming well known but remains limited for those that have been glacially modified the principal influences on sedimentation in these environments relate to the glacial sediment input controlled by relief of basin margin glacier thermal regime and ice flow dynamics and depositional environments influence of traction currents substrate relief and proximity to nearby ice margins typical ranges of sedimentation rates can be established for glacially influenced continental margin environments and these may provide a framework for ancient sequences starvation of sediment supply to glacially influenced continental margins is common the nature of sub ice shelf sedimentation a model that has been applied to many ancient glacial sequences is critically reviewed the significance of such sedimentation in the rock record has probably been exaggerated because of oversimplistic interpretations of diamictite sequences existing process models of glaciomarine sedimentation derived from study of modern environments are sometimes difficult to employ in investigation of ancient sedimentary sequences because simple lithofacies criteria and typical vertical profiles are not available to aid in interpretation in addition compositional data emphasized by many workers for distinguishing glaciomarine from continental glacial diamict ite s frequently fingerprint sediment source and not mode of deposition the importance of facies analysis methods for isolating depositional environments is illustrated by three examples of ancient glaciomarine sequences these are the early proterozoic gowganda formation 2 3 ga of northern ontario canada the late proterozoic port askaig formation 670 ma of scotland and ireland and the late cenozoic yakataga formation 20 ma to recent of the gulf of alaska these examples illustrate the significance of detailed genetic studies of ancient glacial rocks in the interpretation of palaeogeographic and tectonic settings diamictite units in ancient glaciomarine sequences cannot be easily interpreted in terms of climatic or ice advance retreat cycles because of the varied controls on diamict accumulation and diamictite preservation in marine basins

glaciological and oceanographic calculations of the mass balance and oxygen isotope ratio of a melting ice shelf on a etudie l alimentation du george vi ice shelf en relation avec l accumulation le velage et la fonte on releve la relation temperature taux d isotope de l oxygene ces donnees sont couplees a des donnees oceanologiques sur les eaux chaudes et son interaction avec le shelf

30 000 year old wild flax fibers a unique finding of wild flax fibers from a series of upper paleolithic layers at dzudzuana cave located in the foothills of the caucasus georgia indicates that prehistoric hunter gatherers were making cords for hafting stone tools weaving baskets or sewing garments radiocarbon dates demonstrate that the cave was inhabited intermittently during several periods dated to 32 to 26 thousand years before the present kyr b p 23 to 19 kyr b p and 13 to 11 kyr b p spun dyed and knotted flax fibers are common apparently climatic fluctuations recorded in the cave s deposits did not affect the growth of the plants because a certain level of humidity was sustained

stress and fluid transfer in a fault zone due to overpressures in the seismogenic crust 1 stress and fluid transfers were analyzed on the surface of a 30 m thick dextral strike slip fault zone subjected to an overpressure of 63 kpa pressure strain measurements taken during the pressurization indicated a strain state primarily controlled by the hydromechanical behavior of permeable fractures and then by the fluid diffusion in the matrix using thm modeling we simulated an extension of these hydromechanical effects to a 25 km depth in the seismogenic crust applying a lithostatic pressure at the base of the fault the simulations indicate that a significant strain in the damage zone greater than that in the protolith along with the differences in hydraulic diffusivity between the damage zone and protolith may induce high static stress and fluid accumulations in the core under this stress this core is projected to exhibit deformity as much as a 12 m shear slip distributed over a 175 m long active zone

poroelasticity observations of anomalous near surface tilt induced by ground water pumping abstract ground tilt signals observed at three different test sites in germany confirm earlier observations of surface deformation occurences caused by the withdrawal of ground water from nearby wells the strength of the signals presented here ranges from a few rad to 230 rad whereby ground tilt was measured in shallow boreholes at depths between 2 and 4 m analysis of the tilt signals suggests that local inhomogeneities in the subsoil can have significant impact on several signal parameters namely its maximum amplitude its variation in time and its strike with respect to the direction of the productive well the observed data emphasize the likelihood of various causes for deviations from the normal tilt response that holds for an isotropic poroelastic half space in particular at one site a reverse well level change also known as noordbergum effect in hydrogeology is seen together with a respective response in the tilt signal the study concludes that near surface deformation in the vicinity of pumped wells bears a wealth of information that may be useful to constrain the conditions of fluid flow at depth and that there is a need for model calculations to fully understand the involved phenomena

flow through fractures flow through fractures is often idealized as flow between two parallel plates plane poiseuille flow the opening or aperture between parallel plates is unambiguous and its relation to flowrate is well known however fractures in rock have uneven walls and a variable aperture a model for flow in a fracture is proposed wherein the fracture is represented by a set of parallel plate openings with different apertures the model leads to a modified poiseuille equation for flow which includes an aperture frequency distribution for the fracture any arbitrary aperture distribution can be used in order to simplify computation and demonstrate the properties of the model a log normal form of distribution is assumed even when an analytical form of the distribution is assumed two parameters rather than a single value representing aperture size are required to determine flowrate models of aperture change for a fracture undergoing compression fracture walls deforming and extension fracture walls separating are developed which constrain the additional parameter and allow calculation of flowrate as a function of mean aperture the theoretical relationships developed between mean aperture and flowrate can be used to interpret published laboratory data for single fractures

analysis of the hydromechanical behavior of a flat lying fracture during a slug test slug tests dilate and contract fractures in aquifers we developed a coupled hydromechanical analysis of an idealized fracture to evaluate effects of these deformations in fractured crystalline rock aquifers the analysis shows the abrupt increase in pressure at the beginning of a slug test causes a slight opening of a fracture but the fracture continues to open as the pressure falls in the wellbore this happens because the pressure increases over an ever widening area even though it decreases in the wellbore eventually decreasing pressure in the vicinity of the wellbore offsets the spreading pressure and the fracture starts to close ultimately returning to its initial aperture when the pressure equilibrates the displacement in the wellbore when the pressure head is rising is always smaller than when the head is falling and this produces a loop like hysteresis when displacement is plotted as a function of pressure a sensitivity analysis shows the displacement at the wellbore is sensitive to the magnitude and distribution of aquifer properties suggesting that the displacement signal could be combined with pressure measurements to improve the interpretation of slug tests during aquifer characterization

isotropic events observed with a borehole array in the chelungpu fault zone taiwan shear failure is the dominant mode of earthquake causing rock failure along faults high fluid pressure can also potentially induce rock failure by opening cavities and cracks but an active example of this process has not been directly observed in a fault zone using borehole array data collected along the low stress chelungpu fault zone taiwan we observed several small seismic events i type events in a fluid rich permeable zone directly below the impermeable slip zone of the 1999 moment magnitude 7 6 chi chi earthquake modeling of the events suggests an isotropic nonshear source mechanism likely associated with natural hydraulic fractures these seismic events may be associated with the formation of veins and other fluid features often observed in rocks surrounding fault zones and may be similar to artificially induced hydraulic fracturing

circulation and heat fluxes during the austral fall in george vi sound antarctic peninsula abstract a mesoscale survey was conducted in northern george vi sound as part of the united states southern ocean global ocean ecosystems dynamics program in austral fall 2001 to examine the circulation and heat fluxes the absolute dynamic height field is determined from a combination of measured currents detided using model predicted tidal currents streamfunction fitting and the thermal wind equation based on hydrographic measurements the results have revealed surface coastal currents of 0 2 m s 1 intruding into northern george vi sound from marguerite bay mb and mesoscale eddies formed within the deep trough both antarctic surface waters and modified circumpolar deep water were transported into the sound along the eastern side of the sound while ice shelf influenced waters exited to mb along the western side analysis indicates that predominant southward winds during the season were responsible for driving the basin wide circulation in the sound both convergence of horizontal heat transports and vertical upwelling heat fluxes were significant to the contribution or delay of local ice formation in george vi sound which is critical for the austral winter ecosystem

bondi cave and the middle upper palaeolithic transition in western georgia south caucasus abstract the late pleistocene expansion of anatomically modern humans amhs into eurasia and the concurrent demise of the neanderthals appears to be a complex and regionally variable process the southern caucasus region with its rich cave sites has recently provided important results regarding this process in this paper we report on the results of fieldwork in bondi cave western georgia providing a new radiocarbon chronology stratigraphic observations analyses of lithic technology and provenance faunal and floral remains as well as paleoenvironmental data the cave includes middle palaeolithic ca 45 000 ka cal bp cultural horizons and a long upper palaeolithic sequence ca 40 000 27 000 cal bp from layer v to iv a modern human tooth was found in layer vb we estimate its age at 39 000 35 800 cal bp 95 4 based on the bayesian age model we built if the context of the tooth is reliable as we think it is this would make it the oldest morphologically modern human in the caucasus upper palaeolithic hunting of tur and bison as well as the collection of various plants including flax is attested mobile upper palaeolithic foragers inhabited the cave in generally cold and dry periods but a mosaic of environments including forests and meadows was nonetheless available to them the archaeological sequence of bondi and adjacent sites indicates a substantial time gap between the middle and upper palaeolithic occupations thus disproving neanderthal amh interaction in this area and lending support to a replacement scenario in the southern caucasus assuming of course that the early upper palaeolithic eup is related to the arrival of amhs

mesoscale characterization of coupled hydromechanical behavior of a fractured porous slope in response to free water surface movement mesoscale characterization of coupled hydromechanical behavior of a fractured porous slope in response to free water surface movement y guglielmi a f cappa a b j rutqvist b c f tsang b and a thoraval c b geosciences azur cnrs unsa ird upmc sophia antipolis france lawrence berkeley national laboratory earth sciences division berkeley usa c ineris ecole des mines de nancy nancy france a corresponding author fax 33 4 92 94 26 10 e mail address guglielmi geoazur unice fr y guglielmi abstract to better understand the role of groundwater level changes on rock slope deformation and damage a carbonate rock slope 30 m 30 m 15 m was extensively instrumented for mesoscale hydraulic and mechanical measurements during water level changes the slope is naturally drained by a spring that can be artificially closed or opened by a water gate in this study a 2 hour slope dewatering experiment was analyzed changes in fluid pressure and deformation were simultaneously monitored both at discontinuities and in the intact rock using short base extensometers and pressure gauges as well as tiltmeters fixed at the slope surface field data were analyzed with different coupled hydromechanical hm codes rocmas flac 3d and udec field data indicate that in the faults a 40 kpa pressure fall occurs in 2 minutes and induces a 0 5 to 31 10 6 m normal closure pressure fall is slower in the bedding planes lasting 120 minutes with no normal deformation no pressure change or deformation is observed in the intact rock the slope surface displays a complex tilt towards the interior of the slope with magnitudes ranging from 0 6 to 15 10 6 rad close agreement with model for both slope surface and internal measurements is obtained when a high variability in slope element properties is introduced into the models with normal stiffnesses of k n faults 10 3 k n bedding planes and permeabilities of k h faults 10 3 k h bedding planes a nonlinear correlation between hydraulic and mechanical discontinuity properties is proposed and related to discontinuity damage a parametric study shows that 90 of slope deformation depends on hm effects in a few highly permeable and highly deformable discontinuities located in the basal saturated part of the slope while the remaining 10 are related to elasto plastic deformations in the low permeability discontinuities induced by complex stress strain transfers from the high permeability zones the periodicity and magnitude of free water surface movements cause 10 to 20 variations in those local stress strain accumulations related to the contrasting hm behavior for high and low permeable elements of the slope finally surface tilt monitoring coupled with internal localized pressure deformation measurements appears to be a promising method for characterizing the hm properties and behavior of a slope and for detecting its progressive destabilization key words fracture rock slope mesoscale in situ poroelastic measurements hydromechanics numerical modeling tiltmeter monitoring damage 1 introduction understanding coupled groundwater and mechanical processes in complex fractured porous rocks is essential for the safety and efficiency of subsurface and slope stability engineering and thus for the security and economic well being of the general public although poorly documented water is often mentioned as a triggering mechanism for failure of rocks with well developed pre existing fractures networks and thus the cause for rock

estimation of fracture flow parameters through numerical analysis of hydromechanical pressure pulses cappa et al modelling pressure pulses in rock fractures estimation of fracture flow parameters through numerical analysis of hydromechanical pressure pulses frederic cappa 1 yves guglielmi 2 jonny rutqvist 3 chin fu tsang 3 and alain thoraval 4 geosciences azur university of nice sophia antipolis sophia antipolis france geologie des systemes et des reservoirs carbonates university of provence aix marseille france earth sciences division lawrence berkeley national laboratory berkeley usa ineris ecole national superieure des mines de nancy parc de saurupt nancy france corresponding author fax 33 4 92 94 26 10 e mail address cappa geoazur unice fr f cappa