occurrence of rocky and sedimentary glacier beds in the swiss alps as estimated from glacier inventory data the occurrence of rocky and sedimentary glacier beds in the swiss alps was investigated using two approaches 1 a detailed and systematic classification of glacier forefields in the completely revised swiss glacier inventory and 2 the application of an algorithm for estimating bed characteristics from glacier inventory data the algorithm is based on the assumption that the sediment balance of a glacierized catchment i e the ratio between debris input from the surrounding rock walls and debris evacuation by the meltwater stream determines the occurrence of rocky sedimentary or mixed beds the processes which govern the sediment balance within a glacierized catchment cannot be easily observed or measured in the field however the main factors reflecting them can be organized in the form of an erosion sedimentation index this index discriminates between glaciers eroding into bedrock and those building up thick sediment beds and thus allows for rough assessments concerning bed characteristics sedimentary and mixed sedimentary rocky glacier beds clearly predominate in the swiss alps but more detailed spatial analysis is required for better predictions

global distribution of beryllium isotopes in deep ocean water as derived from femn crusts the direct measurement of the ratio of cosmogenic 10be t12 1 5 ma to stable terrigenously sourced 9be in deep seawater or marine deposits can be used to trace water mass movements and to quantify the incorporation of trace metals into the deep sea in this study a sims based technique has been used to determine the 10be9be ratios of the outermost millimetre of hydrogenetic ferromanganese crusts from the worlds oceans 10be9be ratios time corrected for radioactive decay of cosmogenic 10be using 234u238u are in good agreement with ams measurements of modern deep seawater ratios are relatively low in the north and equatorial atlantic samples 0 4 0 5 10 7 in the southwest atlantic ratios increase up to 1 10 7 they vary between 0 7 and 1 0 10 7 in indian ocean samples and have a near constant value of 1 1 0 2 10 7 for all pacific samples if the residence time of 10be 10be in deep water is constant globally then the observed variations in 10be9be ratios could be caused by accumulation of 10be in deep water as it flows and ages along the conveyor following a transient depletion upon its formation in the northern atlantic in this view both 10be and 9be reach local steady state concentration in pacific deep water and the global 10be 600 a an alternative possibility is that the be isotope abundances are controlled by local scavenging for this scenario 10be would vary according to local particle concentration and would 600 a in the central pacific but 10be 230 a in the atlantic mass balance considerations indicate that hydrothermal additions of 9be to the oceans are negligible and that the dissolved riverine source is also small furthermore aeolian dust input of 9be appears insufficient to provide the dissolved 9be inventory the dissolution of only a small proportion 2 of river derived particulates could in principle supply the observed seawater 9be content if true ocean margins would be the sites for 9be addition due to the particle reactive nature of be these would also be the primary sites of be removal a possible net result of horizontal water masses passing through these marginal areas might be a decrease in seawater 10be9be and establishment of a relatively constant 9be concentration as 10be 600 a is less than the apparent age of deep water in the pacific 1500 a the pacific record of 10be9be is not expected to show secular variations due to changes in deep water flow despite the large variations in 10be9be between different water masses because of this insensitivity to deep water flow however it is suggested that the 10be9be ratio determined in the authigenic phase of marine sediments or hydrogenetic precipitates should be a suitable tool for monitoring changes in continental input or cosmic ray intensity on longer time scales

growth rate variations of manganese nodules and crusts induced by paleoceanographic events time markers at about 3 ma 6 5 ma and 14 ma are common to 16 manganese nodules and crusts from different localities in the world oceans these time markers correspond to variations in the growth rates in the inner structure and in the chemistry of the samples the observed time markers could be related to 1 changes of the bottom water velocity and 2 variations in the manganese and iron contents in the deep ocean the time markers were determined by high resolution 10be dating applying the accelerator mass spectrometry facility at the eidgenossische technische hochschule zurich

26al 10be systematics in deep sea sediments we report the development of a naoh leaching technique to extract the authigenic al and be in marine sediments which should allow the sedimentary signals of cosmogenic 26al and 10be to be more effectively studied as geochemical geophysical tracers the technique has been applied to the study of 26al and 10be in opal rich sediments from the north pacific the 26al 27al and 10be 9be ratios of 3 10 14 and 1 10 7 leached from the sediments are higher than those in the total sediments by factors of 3 10 and 2 3 respectively the authigenic 10be 9be ratios are similar to those in deep waters at the study site pointing to the potential usefulness of the ratios in paleoceanographic studies the fractions of total be and al in the sediment studied that are of authigenic origin average about 40 and 17 respectively estimated 26al 27a1 ratios in detrital sediments are 10 15 low enough to indicate that the source of 26al in the ocean mainly comes from atmospheric production in the study area the deposition flux of 26al is comparable to its atmospheric supply however the deposition flux of 10be is about threefold higher than the atmospheric input signifying lateral transport of 10be from the open ocean to this area of relatively high particle flux the 26al 10be ratio being insensitive to the oceanic influx of lithogenic particles may serve as a valuable proxy for paleoproductivity both the authigenic and total sediment 26al 27al and 10be 9be ratios decreased significantly at 6 ka which could reflect an enhanced input of windblown lithogenic particles to the north pacific while the enhanced dust input did not significantly alter the deep water 9be concentration it contributed to the observed increase of authigenic 9be flux to the sediment

the development of antarctic glaciation and the neogene paleoenvironment of the maurice ewing bank abstract a micropaleontologic magnetostratigraphic and sedimentologic analysis of 56 piston cores provides the basis of a geologic study of the late miocene to holocene depositional and erosional history of the intermediate depth maurice ewing bank meb located at the eastern extremity of the falkland malvinas plateau southwest atlantic ocean sedimentation on the meb is controlled presently by the position of the polar front and strong bottom currents beneath the axis of the antarctic circumpolar current acc fluctuations in the position of the polar front and in the intensity of the acc are inferred to have largely controlled deposition on the meb since the initiation of acc flow over the bank in the miocene the sedimentary record of the meb is used to infer the late miocene to holocene oceanographic and climatic conditions in the south atlantic sector of the southern ocean the meb suffered major erosion by intense acc flow during late miocene time which exposed cretaceous miocene sediment near the surface and shaped the present configuration of the bank this erosional event is inferred to have occurred during late miocene to early pliocene time 7 2 4 7 m y b p with the major phase of erosion occurring between middle magnetostratigraphic chron 7 and late chron 6 7 2 6 2 m y b p we suggest that the miocene sedimentary record of the meb and other paleoenvironmental evidence from the circum antarctic region precludes the existence of a west antarctic ice sheet or extensive ice shelves along the antarctic margin prior to the late miocene during the late miocene a west antarctic ice shelf formed in the former west antarctic sea and rapidly thickened until it grounded below sea level to form the west antarctic ice sheet formation of this ice sheet with floating and partially grounded extensions ice shelves in the ross and weddell embayments led to the first major production of true antarctic bottom water formed in a manner similar to today which permanently altered global abyssal circulation late miocene changes in oceanic ccd levels and a permanent shift in the oceanic 13 c 12 c composition may be attributed to this major change in abyssal circulation a decrease in acc velocity during an early pliocene amelioration of climate led to resumption of deposition on the bank from 4 7 to 3 9 m y b p intensification of the acc during the late gilbert and early gauss chrons again resulted in limited deposition and widespread erosion and or non deposition over most of the meb from 4 0 to 3 2 m y b p acc velocity apparently began to wane during the middle of the gauss chron and allowed widespread deposition on the bank during late gauss time 2 9 2 48 m y b p and over more limited areas during earliest matuyama time 2 48 to about 2 2 m y b p during middle to late matuyama time bottom current intensity reached its greatest post miocene level forming a regional disconformity between sediments of about 2 0 and 1 0 m y in age this increased circumpolar circulation and associated erosion is inferred to have peaked during the late matuyama chron 1 2 1 0 m y b p and is approximately the same age as the tentatively dated greatest patagonian glaciation in nearby southern argentina between 1 0 and 0 7 m y b p the bank was blanketed with a coarse erosion resistant layer of ice rafted detritus which armored the older sediment thereby protecting it from major subsequent erosion sedimentation on the meb during the bruhnes chron 720 000 yr b p present was intermittent and finally culminated with the deposition of a veneer of carbonate ooze during or since latest pleistocene time

evidence for a till layer beneath storglaciaren sweden based on electrical resistivity measurements evidence for a till layer beneath storglaciaren sweden based on electrical resistivity measurements

late cenozoic sedimentation and metal deposition in the north pacific similar major chemical variations in cores from three sites across a wide area of the north pacific are modeled by coupling the vertical and horizontal motions of the pacific plate with a constant authigenic flux of elements into the sediments superimposed over this flux is an input of detrital material of relatively constant chemical composition the major features of sediment chemistry of cores from the north pacific apparently vary in a fairly uniform and systematic manner and these variations are consistent with cenozoic plate movement elements with a significant authigenic component e g mn co cu ni display high concentrations at depth in cores that correspond to the period when the seafloor while under the low productivity subtropical gyre of the n pacific accumulated sediment at an extremely slow rate 1 mm kyr these concentrations were diluted when the sites experienced an increase in the eolian mass accumulation rate first brought about by migration into the influence of the westerlies and then dominantly by the huge input of wind blown detritus which corresponded to the onset of northern hemisphere glaciation a comparison of 10be profiles to the profiles of metal concentrations is used to reveal the occurrence of haituses in the sediment column over the past 8 m y

the effect of the subglacial water pressure on the sliding velocity of a glacier in an idealized numerical model in order to interpret observed short term variations of the sliding velocity of a glacier the effect of a variable subglacial water pressure on the sliding velocity has been studied using an idealized numerical model in particular the transient stages of growing or shrinking water filled cavities at the ice bedrock interface were analysed it was found that the sliding velocity was larger when cavities were growing than when they had reached the steady state size for a given water pressure the smallest sliding velocities occurred while cavities were shrinking when cavitation is substantial a small drop of water pressure below the steady state value e g by 0 5 bar can temporarily cause backward sliding a limiting water pressure at which sliding becomes unstable is derived the consequences of more realistic assumptions than those of the model are discussed

marine cobalt resources ferromanganese oxides in the open oceans are more enriched in cobalt than any other widely distributed sediments or rocks concentrations of cobalt exceed 1 percent in ferromanganese crusts on seamounts ocean ridges and other raised areas of the ocean the cobaltrich crusts may be the slowest growing of any earth material accumulating one molecular layer every 1 to 3 months attention has been drawn to crusts as potential resources because they contain cobalt manganese and platinum three of the four priority strategic metals for the united states moreover unlike abyssal nodules whose recovery is complicated by their dominant location in international waters some of the most cobalt rich crusts occur within the exclusive economic zone of the united states and other nations environmental impact statements for crust exploitation are under current development by the department of the interior

combination of srtm3 and repeat aster data for deriving alpine glacier flow velocities in the bhutan himalaya abstract the present study evaluates the fusion of dems from the advanced spaceborne thermal emission and reflection radiometer aster instrument and the shuttle radar topography mission srtm the study area consists of high elevation glaciers draining through the rough topography of the bhutan himalayas it turns out that the aster derived and srtm3 dems have similar accuracy over the study area but the srtm3 dem contains less gross errors however for rough topography large sections of the srtm3 dem contain no data we therefore compile a combined srtm3 aster dem from this final composite master dem we produce repeat aster orthoimages from which we evaluate the dem quality and derive glacier surface velocities through image matching the glacier tongues north of the himalayan main ridge which enter the tibet plateau show maximum surface velocities in the order of 100 200 m year 1 in contrast the ice within the glacier tongues south of the main ridge flows with a few tens of meters per year these findings have a number of implications among others for glacier dynamics glacier response to climate change glacier lake development or glacial erosion the study indicates that space based remote sensing can provide new insights into the magnitude of selected surface processes and feedback mechanisms that govern mountain geodynamics

strontium isotopic compositions and paleoceanographic implication of fossil manganese nodules in dsdp odp cores leg 1 126 abstract strontium isotopic compositions of acetic acid hoac leachate fractions of eight manganese oxide deposits from the modern seafloor and of twenty one buried manganese nodules from cretaceous to recent sediments in dsdp odp cores were measured 87sr 86sr ratios of hoac leachates in all modern seafloor manganese oxides of various origins are identical with present seawater the 87sr 86sr ratios of the hoac leachates of buried nodules from dsdp odp cores are significantly lower than those of nodules from the modern seafloor and are mostly identical with coeval seawater values estimated from the age of associated sediments it is suggested that the buried nodules in dsdp odp cores are not artifacts transported from the present seafloor during the drilling process but are in situ fossil deposits from the past deep sea floor during cretaceous to quaternary periods the formation of deep sea fossil nodules prior to the formation of antarctic bottom water aabw indicates that the circulation of oxygenated deep seawaters have activately deposited manganese oxides since the eocene epoch or earlier

short term geomorphological evolution of proglacial systems proglacial systems are amongst the most rapidly changing landscapes on earth as glacier mass loss permafrost degradation and more episodes of intense rainfall progress with climate change this review addresses the urgent need to quantitatively define proglacial systems not only in terms of spatial extent but also in terms of functional processes it firstly provides a critical appraisal of prevailing conceptual models of proglacial systems and uses this to justify compiling data on rates of landform change in terms of planform horizontal motion elevation changes and sediment budgets these data permit us to produce novel summary conceptual diagrams that consider proglacial landscape evolution in terms of a balance of longitudinal and lateral water and sediment fluxes throughout we give examples of newly emerging datasets and data processing methods because these have the potential to assist with the issues of i a lack of knowledge of proglacial systems within high mountain arctic and polar regions ii considerable inter and intra catchment variability in the geomorphology and functioning of proglacial systems iii problems with the magnitude of short term geomorphological changes being at the threshold of detection iv separating short term variability from longer term trends and v of the representativeness of plot scale field measurements for regionalisation and for upscaling we consider that understanding of future climate change effects on proglacial systems requires holistic process based modelling to explicitly consider feedbacks and linkages especially between hillslope and valley floor components such modelling must be informed by a new generation of repeated distributed topographic surveys to detect and quantify short term geomorphological changes

age determinations and growth rates of pacific ferromanganese deposits using strontium isotopes abstract 87 sr 86 sr ratios trace element and ree compositions and textural characteristics were determined for three hydrogenetic fe mn crusts one hydrothermal deposit and two mixed hydrothermalhydrogenetic crusts from the pacific the sr isotope data are compared to the sr seawater curve for the cenozoic to determine the ages and growth rates of the crusts the 87 sr 86 sr in the crusts does not increase monotonically with depth as expected if the sr were solely derived from seawater and perfectly preserved since deposition this indicates post depositional exchange of sr or heterogeneous sources for the sr originally contained in the crusts textures of hydrogenetic crusts generally correlate with sr isotopic variations the highest porosity intervals commonly exhibit the highest 87 sr 86 sr ratios indicating exchange with younger seawater intervals with the lowest porosity commonly have lower 87 sr 86 sr and may preserve the original sr isotopic ratios minimum ages of crust growth inception were calculated from dense low porosity intervals growth of the hydrogenetic crusts began at or after 23 ma although their substrates are cretaceous estimated average growth rates of the three hydrogenetic crusts vary between 0 9 and 2 7 mm ma consistent with published rates determined by other techniques within the marshall islands crust growth rates for individual layers varied greatly between 1 0 and 5 4 mm ma for one crust very low 87 sr 86 sr ratios occurred in detrital rich intervals hydrothermal fe mn oxide from the active lau basin back arc spreading axis valu fa ridge has an 87 sr 86 sr ratio with a predominantly seawater signature 87 sr 86 sr 0 709196 indicating a maximum age of 0 9 ma one crust from an off axis seamount west of gorda ridge may have begun precipitating hydrogenetically at 0 5 ma 0 709211 and had increasing hydrothermal or volcanic input in the top half of the crust indicated by a significantly lower 87 sr 86 sr ratio 0 709052

formation age of the dual structure and environmental change recorded in hydrogenetic ferromanganese crusts from northwest and central pacific seamounts abstract thick hydrogenetic ferromanganese fe mn crusts from the northwest and central pacific seamounts often show a distinct dual structure composed of a typical hydrogenetic porous friable upper part of fe mn oxides layer 1 and the underlying dense hard phosphatized growth generation of fe mn oxides layer 2 in this study layer 2 always appears above the substrate rock and composes the lower part of the crust it is never found as the upper crust layer in contact with seawater the chemical composition of layer 2 clearly differs from the younger layer 1 hydrogenetic fe mn oxides and is depleted in fe al ti and co and enriched in ni cu and zn relative to layer 1 the be isotope age models of the crusts were refined with paleomagnetic and paleontological information and applied to selected crust samples the age model indicates fairly continuous growth from the substrate to the surface and fairly constant growth rates during the past 17 ma the growth rate from the miocene to the present has varied by a factor of two about 2 4 mm myr in layer 1 while layer 2 has similar but more variable growth rates than layer 1 the calculated age for the base of layer 1 and possibly the age of termination of phosphatization is never younger than the late miocene the age seems to vary with water depth shallower water crusts between 991 and 1575 m showing a younger age of about 10 ma whereas the deeper water 2262 m crusts have extrapolated ages for the base of layer 1 of be 17 1 2 5 ma this trend indicates that phosphatization took place in a less oxidizing environment during growth of layer 2 followed by a weakened oxygen minimum zone or intensified aabw during growth of layer 1

modelling mass balance using photogrammetric and geophysical data a pilot study at griesgletscher swiss alps the kinematic boundary condition at the glacier surface can be used to give glacier mass balance at a point as a function of changes in the surface elevation and of the horizontal and vertical velocities vertical velocity can in turn be estimated from basal slope basal ice velocity and surface strain in a pilot study on the tongue of griesgletscher swiss alps the applicability of the relation for modelling area wide ice flow and mass balance distribution is tested the key input of the calculations i e the area wide surface velocity field is obtained using a newly developed photogrammetric technique ice thickness is derived from radar echo soundings error estimates and comparisons with stake measurements show an average accuracy of approximately 0 3 m a for the calculated vertical ice velocity at the surface and 0 7 m a for the calculated mass balance due to photogrammetric restrictions and model inherent sensitivities the applied model appeared to be most suitable for determining area wide mass balance and ice flow on flatlying ablation areas but is so far not very well suited for steep ablation areas and most parts of accumulation areas nevertheless the study on griesgletscher opens a new and promising perspective for the monitoring of spatial and temporal glacier mass balance variations

subglacial electrical phenomena the subglacial electrical environment is surprisingly complex owing to the variety of processes that promote spatial and temporal variability possible sources of variability are the chemical evolution of subglacial water and the structural and morphological evolution of the drainage configuration such changes contribute to changes in the apparent resistivity of the glacier bed less obvious but possibly more interesting are those electrical phenomena associated with the natural transport of water and charge in the subglacial drainage system streaming potentials are generated by water flow through subglacial sediment and these potentials are closely associated with the subglacial water pressure field to explore these effects we have monitored induced and natural electrical responses in the deforming material beneath trapridge glacier yukon canada several arrays of electrodes were placed at the ice bed interface and data were recorded over a period of several years data from these experiments indicate that natural potentials can be used to monitor water pressure gradients and that the bulk resistivity of the glacier bed can be altered by changing the hydraulic regime we present evidence that temporal variations in streaming potentials can indicate fluctuations in subglacial water flow rate and that spatial variations can be related to variations in bed elevation water pressure and hydraulic connectivity

modeling glacier thickness distribution and bed topography over entire mountain ranges with glabtop application of a fast and robust approach 1 the combination of glacier outlines with digital elevation models dems opens new dimensions for research on climate change impacts over entire mountain chains of particular interest is the modeling of glacier thickness distribution where several new approaches were proposed recently the tool applied herein glabtop glacier bed topography is a fast and robust approach to model thickness distribution and bed topography for large glacier samples using a geographic information system gis the method is based on an empirical relation between average basal shear stress and elevation range of individual glaciers calibrated with geometric information from paleoglaciers and validated with radio echo soundings on contemporary glaciers it represents an alternative and independent test possibility for approaches based on mass conservation and flow as an example for using glabtop in entire mountain ranges we here present the modeled ice thickness distribution and bed topography for all swiss glaciers along with a geomorphometric analysis of glacier characteristics and the overdeepenings found in the modeled glacier bed these overdeepenings can be seen as potential sites for future lake formation and are thus highly relevant in connection with hydropower production and natural hazards the thickest ice of the largest glaciers rests on weakly inclined bedrock at comparably low elevations resulting in a limited potential for a terminus retreat to higher elevations the calculated total glacier volume for all swiss glaciers is 75 22 km3 for 1973 and 65 20 km3 in 1999 considering an uncertainty range of 30 these results are in good agreement with estimates from other approaches

water storage and subglacial drainage conditions inferred from borehole measurements on gornergletscher valais switzerland measurements of change in length of a borehole or displacements of poles and of subglacial water pressure were combined with drainage tests and electrode tests in boreholes in experiments near the northern margin of gornergletscher valais switzerland at the upstream side of an overdeepening the measurements suggest that the subglacial drainage system consisted of discrete conduits at that location presumably linked cavities on clean bedrock changes in subglacial water pressure were followed by variations in subglacial water storage together with similar variations in elevation of a pole the variations in subglacial water storage caused changes in cross sections of subglacial passageways and thereby changed the frequencies of slug test oscillations similar experiments conducted near the center line of the glacier revealed different subglacial conditions impeded drainage through a sediment layer and different depths of water levels in different boreholes these results are discussed in relation to previous studies

diffusion and supply rates of 10be and 230th radioisotopes in two manganese encrustations from the south china sea ages of two mn encrustations estimated by their 230th and 10be distributions are compared with k ar ages and micropaleontological datings of their nuclei to discuss possible diffusion and supply effects of the radioisotope distribution and their influence on the reliability of age determinations based on comparable results obtained by the different methods the effective diffusion coefficient of 10be can be calculated as d 1 0 10 8cm2 y this coefficient is 3 8 times smaller than the best estimates available at present in both nodules we observe lower 10be concentrations in the uppermost 2 3 mm 1 3 m y which suggests that 10be uptake has been reduced since the middle pleistocene the 2 7 fold increase of the growth rate starting 3 2 m y ago coincides with the initiation of the northern hemisphere glaciation

distribution of10be and9be in the pacific ocean abstract the vertical distributions of10be and9be at three locations in the pacific 25 n 170 e 17 n 118 w 3 s 117 w are presented the results show that both isotopes exhibit nutrient like profiles from the surface to the bottom the increase for10be is two to threefold and that for9be is about fivefold while the inter station variations in surface water concentrations may reach a factor of two deep water values tend to be much more uniform averaging about 2000 atoms g for10be and 30 pm for9be a similar situation applies to the10be 9be ratio it varies approximately from 1 to 3 10 7 atom atom at shallow depths but tends toward a value close to 1 1 10 7 in the deep ocean the variation of10be 9be can be viewed as resulting from the fact that10be in a given parcel of water consists of two components recycled and primary the recycled component is that part of10be which has reached tracer equilibrium with9be as opposed to the primary component which upon entering the sea from the atmosphere has yet to equilibrate with9be through particle cycling and mixing processes it is estimated that 70 to nearly 100 of10be at the three stations are being recycled and the recycled beryllium bears an atomic ratio of10be 9be close to 1 10 7 the oceanic residence time of be is of the order of 1000 4000 years comparable to or slightly longer than the ocean mixing time

calcareous nannofossil biostratigraphic dating of a ferromanganese crust from schumann seamount abstract calcareous nannofossil biostratigraphy was employed to determine the age and growth rates of the different layers within ferromanganese crusts from schumann seamount 200 miles north of the island of kauai hawaii this work is part of a study to reconstruct the paleoceanographic history of crusts using various geochemical indicators the methods are based on the identification of coccolith imprints not actual coccolith remains age constraints on the time span of a particular horizon are defined either 1 by the presence of a species which was extant for only a limited geological time interval or 2 by the presence of two organisms whose time ranges overlapped age resolution is optimized by short time ranges or narrow overlaps in the crust studied there was considerable inter horizon variability in the preservation of coccolith imprints in imprint abundance and in species diversity some of the crust layers examined were narrowly constrained temporally 1 4 myr while others were less so 10 myr our results indicate that the minimum age for the interval at 27 mm depth is at least eocene this is the maximum age many believe any crust can be the position of this interval however is only about one half of the way through the crust while the data support previous estimates of average crust growth rates 0 5 mm myr the actual apparent growth rate appears to have varied by an order of magnitude 0 1 to 2 mm myr

prevention of outburst floods from periglacial lakes at grubengletscher valais swiss alps flood and debris flow hazards at grubengletscher near saas balen in the saas valley valais swiss alps result from the formation and growth of several lakes at the glacier margin and within the surrounding permafrost in order to prevent damage related to such hazards systematic investigations were carried out and practical measures taken the evolution of the polythermal glacier the creeping permafrost within the large adjacent rock glacier and the development of the various periglacial lakes were monitored and documented for the last 25 years by photogrammetric analysis of annually flown high resolution aerial photographs seismic refraction d c resistivity and gravimetry soundings were performed together with hydrological tracer experiments to determine the structure and stability of a moraine dam at a proglacial lake the results indicate a maximum moraine thickness of 100 m extremely high porosity and even ground caverns near the surface may have resulted from degradation of sub and periglacial permafrost following 19th 20th century retreat of the partially cold glacier tongue the safety and retention capacity of the proglacial lake were enhanced by deepening and reinforcing the outlet structure on top of the moraine complex the water level of an ice dammed lake was lowered and a thermokarst lake artficially drained

on the thermal regime of an arctic valley glacier a study of white glacier axel heiberg island n w t canada from 1974 to 1981 a total of 32 bore holes was drilled on white glacier and vertical ice temperature profiles measured the data obtained allowed the construction of three longitudinal and four transverse profiles of the two dimensional temperature distributions thus an extensive layer of temperate or near temperate ice was discovered close to the bedrock in the lowest part of the glacier tongue it was also found that the temperature distribution cannot be in a steady state since there is a temperature minimum 100 150 m below the glacier surface in the accumulation area a simple numerical model calculation shows that this minimum can be mostly explained by the general climatic warming since 1880 the 10 m temperatures show diffuse relations to climatic conditions and balance zones a simple scheme for extrapolating surface temperatures is discussed

beryllium in the water column of the central north pacific the existence of the cosmogenic radioisotope of beryllium 10be t1 2 1 5 myr was first confirmed1 2 almost 25 yr ago subsequently merrill et al 3 worked out the sedimentary geochemistry of the stable isotope of the element 9be the geochronological potential of 10 be could not be exploited however because of its extremely low abundance global average production rate 1 08 atoms cm 2 min 1 4 and the difficulties associated with the analysis of the stable species 9be particularly in natural waters this situation is changing dramatically with the application of accelerator techniques to the detection of the radioisotope5 it thus becomes important to obtain a detailed understanding of the geochemistry of 9be since the potential use of the stable isotope for normalization purposes would significantly enhance the usefulness of the radioactive species in dating studies we report here the first detailed profile for 9be in the oceanic water column

ferromanganese crusts from necker ridge horizon guyot and s p lee guyot geological considerations abstract necker ridge horizon guyot and s p lee guyot in the central pacific were sampled seismically surveyed and photographed by bottom cameras in order to better understand the distribution origin and evolution of ferromanganese crusts necker ridge is over 600 km long with a rugged crest pods of sediment to 146 m thick slopes that average 12 to 20 and debris aprons that cover some of the lower flanks substrate lithologies are mostly hyaloclastite volcaniclastic breccia and minor alkalic basalt horizon guyot 300 km long and 75 km wide is capped by at least 160 m of sediment which buries stepped terraces substrate lithologies are similar to those on necker ridge although previous workers sampled much tholeiitic basalt on horizon s p lee guyot 125 km long and 80 km wide is capped by at least 300 m of sediment and contains talus aprons along its lower flanks ferromanganese encrusted rocks were recovered in every dredge and are thickest on necker ridge crust thicknesses average about 2 5 1 5 and 0 8 cm for necker horizon and s p lee respectively crusts range from smooth or porous surfaces to knobby and botryoidal the entire crust is laminated however two distinct layers commonly exist separated by a paper thin layer of phosphorite the dominant mineral of all crusts is vernadite mno 2 while quartz feldspar apatite and in three rocks todorokite are minor phases quartz and feldspar decrease with decreasing latitude of occurrence and is suggested to be related to eolian input on the average apatite also increases within the crusts with decreasing latitude of occurrence which may be related to high biological productivity in the zone of equatorial upwelling phosphorite substrates are more abundant on necker ridge and s p lee guyot than they are on horizon guyot seamount ferromanganese nodules are distinct from abyssal nodules in their chemistry and internal structure

the geochemical cycle of 9be a reconnaissance an initial survey has been made of the geochemistry of 9be in natural waters with a view to utilizing the isotope with the cosmogenic species 10be t1 2 1 5 m y in geochronological studies of sedimentary accumulation the mobility of9be in continental waters is a strong function of ph with acid streams ph 6 being strongly enriched as compared to alkaline carbonate rivers large scale scavenging of beryllium occurs in the estuaries of rivers containing more than about 200 pm of the element in alkaline systems of lower concentration the element appears to behave conservatively the net flux of beryllium to the ocean is estimated as that equivalent to an average effective river concentration of about 150 pm beryllium is strongly enriched in ridge crest hydrothermal solutions over ambient seawater the flux is approximately 70 of that from the continents the deep water concentrations of 9be vary by only 20 between the north atlantic and north pacific demonstrating that the chemical saltation produced by scavenging from the deep water column and release from the sediments predominates over simple advective concentration along flow lines isotopic homogenization of 10be and 9be is probably achieved in the ocean the situation in continental waters appears much less promising

10 be dating of a manganese crust from central north pacific and implications for ocean palaeocirculation one of the most promising applications of the new 10be detection technique using accelerator mass spectrometry is the determination of growth rates of mn nodules and crusts1 5 because the half life of cosmogenic 10be 1 5 myr is of the same order as the time needed for a few millimetres of nodule material to grow 10be is a useful tool for unravelling such evolution during the late tertiary when most nodules are assumed to have started their growth6 mass spectrometric measurement of a 10be profile across the manganese crust va 13 2 from the central pacific using a tandem van de gr a ff accelerator yields growth rates of 2 7 and 4 8 mm myr 1 for the layers of the crust accumulated between recent and 6 myr bp and between 6 and 11 myr respectively using these measurements as well as 230th dating we have been able to distinguish boundaries between zones in the crust with different structures and chemical compositions and to assign ages to them these ages are 0 12 2 9 3 4 5 7 6 7 7 9 10 12 and 13 16 myr bp all of these boundaries apparently coincide with the times reported for quaternary and late tertiary palaeoclimatic events suggesting that the crust growth has been strongly influenced by palaeoclimate

time lapse imaging of subglacial drainage conditions using three dimensional inversion of borehole electrical resistivity data we recorded electrical resistivity data at the base of four boreholes drilled through haut glacier d arolla switzerland the data were acquired repetitively every hour over two diurnal hydrological cycles in the late melt season separated by 10 days constrained three dimensional 3 d data inversion allowed reconstruction of hourly variations in bulk resistivity in the subglacial sediment layer inverted resistivity models reflect the establishment of channelized subglacial drainage in the study area between the two hydrological cycles in agreement with previous work daily variations in bulk and water resistivity are in phase and bulk resistivity amplitudes decrease away from the subglacial channel using selected electrical hydraulic relationships we estimate metre scale changes in the hydraulic conductivity and porosity of the subglacial sediment layer accounting for increasing clay content and decreasing median grain radius with distance from the channel hydraulic conductivity and porosity were respectively calculated to decrease from 6 4 2 1 10 2 m s 1 and 0 34 0 01 at the channel to 3 3 2 2 10 2 m s 1 and 0 26 0 01 at a distance of 5 m from it the hydraulic conductivity estimates are in agreement with previously inferred values and the porosity estimates fall within the expected range for unlithified subglacial sediments we conclude that collection and inversion of repeat 3 d subglacial resistivity data is feasible and has the capacity to generate multidimensional images of subglacial hydraulic processes and properties

a high resolution authigenic 10be 9be record of geomagnetic moment variations over the last 300 ka from sedimentary cores of the portuguese margin a high resolution study of authigenic be isotopes 10be and 9be combined with continuous relative paleointensity records has been performed along the same marine sedimentary sequences from the portuguese margin n e atlantic covering the past 300 ka in order to assess relationships between geomagnetic moment variations and 10be production rate variations a carefull examination of the various ways of taking into account environmental disturbing effects on the authigenic 10be concentration leads to the conclusion that the most reliable proxy of cosmonuclide production rates is presently the authigenic 10be 9be ratio eight intervals of significant authigenic 10be 9be enhancement evidence geomagnetic moment drops related to global paleomagnetic excursions some being already admitted others being proposed as new geomagnetic features since contrarily to sedimentary magnetic remanence the authigenic 10be 9be records dipole moment variations without significant acquisition delay it provides better constraints on their timing comparison of 10be 9be and benthic 18o records from the same cores suggests that dipole moment lows preferentially occured during or at the end of interglacial episodes with a quasi period of 100 ka

beryllium isotope geochemistry in tropical river basins abstract the distributions of beryllium 9 and beryllium 10 in rivers within the orinoco and amazon basins have been examined to extend our understanding of their geochemical cycles and to develop their use both in geochronometry and in studying erosional processes beryllium 9 the stable isotope is weathered from mineral lattices before entering the riverine dissolved or exchangeable phase the cosmogenic radioisotope 10be t 1 2 1 5 myr is produced primarily in the atmosphere and is brought into riverine systems via rainfall in dissolved or exchangeable form it may be used to examine the processes which affect beryllium partitioning between the dissolved and particulate phases ancillary data such as major ion distributions provide a basis for selecting regions in which riverine chemistry is dominated by a single geochemical process allowing examination of its effects on be distributions in isolation analyses of 9be in dissolved and suspended material from rivers with a wide range of chemical compositions indicate that its geochemistry is primarily controlled by two major factors 1 1 its abundance in the rocks of the watershed and 2 2 the extent of its adsorption onto particle surfaces the relative importance of these parameters in individual rivers is determined by the extent of interaction with flood plain sediments and the riverine ph this understanding of 9be geochemistry forms a basis for examination of the geochemical cycling of 10be in rivers which are dominated by interaction with sediments the riverine concentration of dissolved 10be is far lower than that in the incoming rainwater indicating that a substantial proportion of it is retained within the soils of the basin or is adsorbed onto riverine particles however in acidic rivers in which the stable dissolved be concentration is determined by the be level in the rocks of the drainage basin dissolved 10be has essentially the same concentration as in precipitation these observations imply that the soil column in such regions must be saturated with respect to 10be and that the ratio of the inventory to the flux does not represent an age as may be the case in temperate latitudes but rather a residence time

transport of10be and9be in the ocean beryllium isotopes 10be and9be have been measured in suspended particles of 1 mm size collected by mid water sediment traps deployed in the eastern pacific at manop sites h 6 32 n 92 50 w water depth 3600 m and m 8 50 n 104 00 w 3100 m for comparison surface sediments from box cores taken from the two sites were also studied the concentrations of10be and9be in sediment trap particles are about an order of magnitude smaller than those in the bottom sediments which contain about 8 109 and 6 1016 atoms g 1 of10be and9be respectively the sediment trap samples collected from 50 m off the bottom showed significant 26 63 contributions from resuspended bottom sediments the10be 9be ratio in trap samples varies from 3 to 20 10 8 the variation may partly result from varied proportion of authigenic detrital material the fluxes of both isotopes exhibit a very strong seasonality the fluxes of10be into the traps at about 1500 m are estimated as 9 105 and 4 105 atoms cm 2 a 1 at sites h and m respectively these values are to be compared with the fluxes into the sediments of 4 5 105 atoms cm 2 a 1 at both locations good correlations exist between10be 9be and27al indicating that the primary carrier phase s for the beryllium isotopes in the water column may be aluminosilicates

tv video observations of bed and basal sliding on storglaciaren sweden four boreholes in storglaciaren a small valley glacier in northernsweden were inspected with a video camera in two of the boreholes the apparentglacier bed was filmed in one borehole the bed was found to be composed of softsediment but in the other it consisted of bedrock in the latter the camera moved5 6 mm relative to the bed during an 80 min period the recorded camera movementshowed a background motion which is in the expected range of basal sliding superimposed on the background motion a jerky motion of a high speed spike wasfound the jerky motion is interpreted as a stress release induced by local topographyat the ice bed interface

photogrammetric reconstruction of glacier mass balance using a kinematic ice flow model a 20 year time series on grubengletscher swiss alps the kinematic boundary condition at the glacier surface can be used to provide glacier mass balance at individual points if changes in surface elevation horizontal and vertical surface velocities and surface slope are known vertical ice velocity can in turn be estimated from basal slope basal ice velocity and surface strain this relation is applied to reconstruct a 20 year mass balance curve of grubengletscher swiss alps largely using repeated aerial photogrammetry but only a minimum of field work for individual years the mass balance distribution on the glacier tongue was modelled with an accuracy of about 0 9 m a 1 ice mechanical assumptions and errors in glacier bed geometry markedly affect discrete mass balance patterns but are eliminated to a major extent when calculating year to year mass balance changes the resulting curve for the grubengletscher tongue 1973 1992 shows reasonable consistency with meteorological data and other glaciologically derived mass balance series large changes in measured ice speed on the glacier tongue 50 significantly governed the long term variability of ice thickness over the observational period

application of the authigenic 10be 9be dating method to continental sediments reconstruction of the mio pleistocene sedimentary sequence in the early hominid fossiliferous areas of the northern chad basin the concentrations of atmospheric cosmogenic 10be normalized to the solubilized fraction of its stable isotope 9be have been measured in the authigenic phase leached from silicated continental sediments deposited since the upper miocene in the northern chad basin this method is validated by the systematic congruence with the biochronological estimations based on the fossil mammal evolutive degree of faunal assemblages the fifty five authigenic 10be 9be ages obtained along 12 logs distributed along two west east cross sections that encompass best representative mio pliocene outcrops including paleontological sites show a systematic stratigraphic decrease when considering all studied sedimentary facies extending from the pleistocene up to 8 ma and allow performing geologic correlations otherwise impossible in the studied area the resulting global sequence evidences and temporally specifies the succession of the main paleoenvironments that have developed in this region since the miocene under the special conditions encountered in the northern chad basin this study demonstrates that the authigenic 10be 9be ratio may be used as a dating tool of continental sedimentary deposits from 1 to 8 ma the half life of 10be theoretically allowing dating up to 14 ma it may have fundamental implications on important field research such as paleoclimatology and through the dating of fossiliferous deposits in paleontology and paleoanthropology

constancy of oceanic deposition of 10 be as recorded in manganese crusts recent developments in the use of nuclear accelerators as high energy mass spectrometers1 2 has renewed interest in the study of cosmogenic 10be half life 1 5 myr as a geophysical time tracer the accelerator techniques enable us to measure 10be with a sensitivity of 107 atoms or less the potential age dating span with 10be is extended back to at least 15 myr bp providing that the 10be production and deposition rates remain constant or nearly constant over that time period a knowledge of the long term constancy in the 10be deposition rate is thus very important we report here the first detailed measurements of 10be and 9be in two ferromanganese oxide crusts from the sea floor of the equatorial atlantic sample no k 9 21 and the north pacific schw 1d each representing 10 myr of accumulation history we have found in these crusts that the deposition of 10be and 10be 9be during the past 7 9 myr has been constant averaged over time intervals of 1 myr the variation is within 6 before that time both crusts show similar significant deviations the 7 9 myr demarcation may be related to the reported late miocene global abyssal circulation change in the ocean3

incorporation of be isotopes and other trace metals into marine ferromanganese deposits abstract two to threefold inward increase of 10be 9be cu and ni have been found in surface layers of marine ferromanganese deposits we interpret this phenomenon as reflecting the manner in which the be isotopes and probably other trace metals e g cu and ni are incorporated on reaching the sea floor exchangeable be is released from its carrier phase to the pore water of the ferromanganese deposits diffuses inward and gets fixed into the deposits the fixation process may be related to the mineralogical reorganizations suggested by previous studies we have modeled this concept and applied it to a mn crust on which detailed analyses of cu ni and natural decay series nuclides as well as be isotopes are made post depositional fixation of th isotopes may also occur the redistributions of be and th isotopes are confined to regions very close to the surface of the deposits for all practical purposes they will not affect growth rate determinations conventionally done using these isotopes the linearly extrapolated 10 be 9 be ratio to the surface from deep layers of a mn deposit does not necessarily represent that ratio in sea water

response of beryllium and radiogenic isotope ratios in northern atlantic deep water to the onset of northern hemisphere glaciation we present time corrected ratios of cosmogenic 10 be to continent sourced 9 be from two fe mn crusts located in the northwest atlantic in the vicinity of the origins of northern atlantic deep water nadw these initial 10 be 9 be ratios represent those of the ambient seawater at the time of crust deposition and are constant through the last 7 ma previously published isotope records of radiogenic nd and pb isotopes in these crusts show a decrease in e nd and an increase in 206 pb 204 pb over the last 5 ma these changes are consistent with a gradual increase in the strength of nadw production an increase in the labrador sea component of nadw or an increased erosional input into the labrador sea since the residence time and thus the advective length scales of dissolved be in deep water lie between those of nd and pb records of 10 be 9 be should contrary to what has been observed vary in phase with those of nd and pb if these variations are accounted for by changes in paleo circulation the observed variations in radiogenic nd and pb isotopes are therefore most likely to be explained with an increase in the flux of terrigenous matter in the area of the labrador sea which was possibly associated with ice rafting and selective leaching of pb isotopes an increase of the labrador sea component that contributes to nadw is also a possibility but based on the 10 be 9 be data presented here large scale changes in the thermohaline circulation can be discounted as cause for the radiogenic tracer variations

cosmogenic nuclide dating of sahelanthropus tchadensis and australopithecus bahrelghazali mio pliocene hominids from chad ages were determined at two hominid localities from the chad basin in the djurab desert northern chad in the koro toro fossiliferous area kt 12 locality 16 00 n 18 53 e was the site of discovery of australopithecus bahrelghazali abel and in the toros menalla fossiliferous area tm 266 locality 16 15 n 17 29 e was the site of discovery of sahelanthropus tchadensis toumai at both localities the evolutive degree of the associated fossil mammal assemblages allowed a biochronological estimation of the hominid remains early pliocene 3 3 5 ma at kt 12 and late miocene 7 ma at tm 266 atmospheric 10be a cosmogenic nuclide was used to quasicontinuously date these sedimentary units the authigenic 10be 9be dating of a pelite relic within the sedimentary level containing abel yields an age of 3 58 0 27 ma that points to the contemporaneity of australopithecus bahrelghazali abel with australopithecus afarensis lucy the 28 10be 9be ages obtained within the anthracotheriid unit containing toumai bracket by absolute dating the age of sahelanthropus tchadensis to lie between 6 8 and 7 2 ma this chronological constraint is an important cornerstone both for establishing the earliest stages of hominid evolution and for new calibrations of the molecular clock

10be and 9be in marine sediments and their potential for dating using sequential leaching experiments we have measured the fraction of the cosmogenic isotope 10be half life 1 5 my and its stable isotope 9be co extracted with the following phases in marine sediments exchangeable calcium carbonate fe and mn oxyhydroxides organic opal and detrital the extraction of the authigenic phases typically release 70 of the 10be but only 40 of the 9be in order to test its potential for dating marine sediments we have measured the authigeniccally associated 10be 9be in 17 surface sediment samples from different ocean basins the observed spatial variability which appears to be influenced by proximity to continental input of 9be precludes the general and precise applications of leached 10be 9be for dating however the relatively constant value observed in surface sediments over large areas of the pacific indian and southern atlantic oceans shows considerable promise for approximate dating of open oceans sediments in order to test temporal variability a profile of the authigenically associated 10be 9be ratio has been measured in the independently dated central pacific core rc12 65 the observed variation in 10be 9be over the past nine my is approximately twice that expected on the basis of 10be decay alone several possible explanations for such behavior and their potential consequences for the use of leached 10be 9be for dating are discussed

the relationship between 10be and geomagnetic field strength records in central north atlantic sediments during the last 80 ka abstract a profile of leached 10 be 9 be has been measured in an 80 ka sediment core from the northeast atlantic ocean this profile shows a significant inverse correlation with the palaeomagnetic intensity profile inferred from nrm arm measurements in the same core particularly between 40 and 50 ka where a rapid decrease in field intensity is accompanied by a rapid increase in 10 be 9 be the extent to which this increase in 10 be 9 be at 40 ka is associated with a 10 be peak seen in polar ice cores at about the same time remains speculative

a comparison of geodetic and geologic rates prior to large strike slip earthquakes a diversity of earthquake cycle behaviors comparison of preevent geodetic and geologic rates in three large magnitude mw 7 6 7 9 strike slip earthquakes reveals a wide range of behaviors specifically geodetic rates of 26 28 mm yr for the north anatolian fault along the 1999 mw 7 6 izmit rupture are 40 faster than holocene geologic rates in contrast geodetic rates of 6 8 mm yr along the denali fault prior to the 2002 mw 7 9 denali earthquake are only approximately half as fast as the latest pleistocene holocene geologic rate of 12 mm yr in the third example where a sufficiently long pre earthquake geodetic time series exists the geodetic and geologic rates along the 2001 mw 7 8 kokoxili rupture on the kunlun fault are approximately equal at 11 mm yr these results are not readily explicable with extant earthquake cycle modeling suggesting that they may instead be due to some combination of regional kinematic fault interactions temporal variations in the strength of lithospheric scale shear zones and or variations in local relative plate motion rate whatever the exact causes of these variable behaviors these observations indicate that either the ratio of geodetic to geologic rates before an earthquake may not be diagnostic of the time to the next earthquake as predicted by many rheologically based geodynamic models of earthquake cycle behavior or different behaviors characterize different fault systems in a manner that is not yet understood or predictable

automated monitoring of subglacial hydrological processes with ground penetrating radar gpr at high temporal resolution scope and potential pitfalls kulessa b a d booth a hobbs and a l hubbard 2008 automated monitoring of subglacial hydrological processes with ground penetrating radar gpr at high temporal resolution scope and potential pitfalls geophysical research letters 35 24 l24502

element supply to surface sediments and interrelationships with nodules along the aitutaki jarvis transect south pacific a suite of surface sediment samples has been studied from sites on the aitutaki jarvis transect between the equator and 17 s at approximately 160 w in the central pacific ocean the sediments were analysed by bulk and partition analysis in order to characterize changes in sediment geochemistry with water depth and with latitude with particular reference to the effects of variation in supply and dissolution of biogenic material the surface sediments are heterogeneous ranging from carbonate or siliceous oozes to pelagic red clays the elements in the sediments are variably partitioned into different sediment fractions examination of the sediments along the transect has also provided a profile of the carbonate compensation depth which shows it to deepen from approximately 4800 m at 16 s to approximately 5300 m at the equator the relationships between the bulk sediments and the sediment reducible fraction and associated mn fe nodules has been examined variations in the interrelationships between the nodules and the sediment reducible fraction are ascribed to variations in element supply and early diagenetic reactions a major decoupling of the relationship between nodules and associated sediment reducible fraction is observed in the north of the transect at water depths close to the position of the ccd diagenetic reactions involving the destruction of organic matter which result in the reductive remobilization of mn and the release of trace metals from labile material are thought to be important causes of this decoupling

10be and th isotopes in manganese nodules and adjacent sediments nodule growth histories and nuclide behavior abstract the concentration profiles of 9 be 10 be 230 th 232 th 231 pa via 227 th and 238 u have been measured in three manganese nodules one each from the north pacific a47 16 4 the south pacific tf 5 and the indian ocean r v vitiaz in addition the 10 be concentration in deep water from the geosecs reoccupation station 500 of the north pacific and in cores raised from the manganese nodule field in the north pacific have been measured the 10 be concentration in nodule and seawater samples was measured by the accelerator masss spectrometric technique employing the yale tandem van de graaff accelerator the concentrations of 10 be 230 th exc and 231 pa exc and ratios of 10 be 9 be and 230 th exc 232 th all decrease with depth in the nodules this decrease interpreted in terms of nodule growth yields average growth rates of a few millimeters per million years for the nodules the growth rates of the nodules exhibit temporal variations both on short time 50 000 years and long time several million years scales of the three nodules studied only in tf 5 is the short term average growth rate based on 230 th exc in the top 0 0 5 mm the same as the long term average rate based on be isotope data for the 0 5 17 mm interval for the other two nodules the recent average growth rates based on 230 th exc data differ significantly from the long term average growth rates based on be isotopes in a47 16 4 the 10 be based rate is less than the 230 th exc rate and in r v vitiaz the 10 be based rate is greater than the 230 th exc rate this observation coupled with measurable changes in growth rates even during the past few hundred thousand years suggests but does not prove that the discordant growth rates deduced from 230 th exc and 10 be profiles document changes in nodule growth rate with time rather than mixing effects on 230 th exc profiles the 10 be concentration in the geosecs north pacific deep water is 6100 1200 atoms g this value coupled with the average surface 10 be 9 be ratio of north pacific nodules predicts a 9 be concentration within the limits of measured values the inventory of 10 be and 230 th exc in the nodules is only 10 of the total the remaining being in sediments the 10 be concentrations in the upper portions of two adjacent cores studied are nearly the same but the deposition fluxes of both 10 be and 230 th based on 230 th dating vary by a factor of two this difference is attributable to local redistribution of sediment at the time of deposition prior to accumulation

aquia aquifer dissolved cl and 36cl cl implications for flow velocities the aquia aquifer southern maryland contains a remarkably smooth cl profile 0 46 3 23 ppm along its flow path this is interpreted as a record of historic changes in the deposition of cl in this region those changes have been influenced by the rise and fall of sea level which has altered the distance of the recharge region from the coastline by 200 km the 36cl concentration along the flow path is not as smooth as the cl profile historic variations in cosmogenic production atmospheric transport precipitation and evapotranspiration all might have influenced 36cl concentrations a general similarity between the 36cl and cl profiles suggests that changes in precipitation and evapotranspiration rates which influence both tracers similarly are particularly important to reconcile 14c 36cl and hydrologic data we propose a two tier model for flow in the aquia shallower portions of the aquifer 60 m were subjected to hydraulic gradients and flow rates approximately 5 times larger during the pleistocene than modern prepumping rates at greater depths flow rates were much slower and less variable water in this region may be old enough to record some 36cl decay

an evaluation of strontium isotopic dating of ferromanganese oxides in a marine hydrogenous ferromanganese crust abstract in order to assess the utility of dating marine hydrogenous ferromanganese crusts with strontium isotopes we conducted a series of leaching experiments on samples selected from several stratigraphic layers of a well preserved 9 5 cm thick crust from the pacific ocean initially using a method similar to that of previous studies acetic acid leached residues of twelve subsamples were leached with hcl and the leachates analyzed for their isotopic composition the results did not make stratigraphic sense so we carried out two sequences of more detailed leaches on subsamples from four layers representing the chemical and textural spectrum observed in the crust in one sequence mineral specific leaches were selected for optimal extraction of strontium associated with the respective manganese and iron oxide phases the main compositional endmembers within ferromanganese crusts strontium isotopic ratios for these leaches were compared with those from the other sequence involving acetic acid plus hcl leaches on the same material residues remaining at the end of each leaching sequence were also analyzed it is evident from the results that hcl extracts strontium associated with both phosphatic material and aluminosilicate detritus present within the ferromanganese layers 87 sr 86 sr ratios obtained on the manganese oxides indicate that the strontium within the oxides exchanges with seawater strontium throughout the history of the deposit regardless of the porosity of the layer assuming that this crust is representative of other marine hydrogenous crusts strontium isotopes appear to be of little value for the direct dating of ferromanganese oxide deposits

the 17 august 1999 izmit earthquake on 17 august 1999 an earthquake of magnitude 7 4 shook northwestern turkey details on the earthquake9s characteristics and effects across northwestern turkey are provided and are put in the historical context of previous earthquakes in the region the earthquake was the seventh in a series of earthquakes migrating westwards along the north anatolian fault since 1939 information on historical earthquakes modeling and estimates of the slip rate along the fault indicate that the location and severity of the earthquake should not have come as a surprise

magnetic stratigraphy observed in ferromanganese crust summary a sample of ferromanganese crust deposit schw 1d was cut into two sets of 1 mm slices for palaeomagnetic study alternating field and thermal demagnetization and isothermal remanent magnetization analyses were performed on each thin slice the results reveal the presence of a stable magnetism and both normal and reversed polarity intervals in the specimens the observed polarity intervals cannot be confidently correlated with the geomagnetic polarity time scale of the last 10 myr due to the polarity overlap inherent in the sampling technique but the results confirm the slow accretion rate of ferromanganese deposit determined by 10be method and suggest potential use of ferromanganese deposits in palaeomagnetic and tectonic studies

refraction correction for radio echo sounding of ice overlain by firn expression du trajet du signal radar permettant d eviter les 10 d erreurs obtenues si on assimile le neve a la glace

mobilization of beryllium in the sedimentary column at convergent margins studies of be distributions in subduction zone sediments will help to understand questions regarding the enrichments of cosmogenic be 10 in arc volcanic rocks analyses of be 10 and be 9 in sediments of ocean drilling program site 808 nankai trough and be 9 in porewaters of site 808 and sites 671 and 672 barbados ridge complex show significant decreases in solid phase be 10 and large increases of porewater be 9 at the location of the decollement zone and below or at potential flow conduits these data imply the potential mobilization of be during pore fluid expulsion upon sediment burial experiments involving reaction between a decollement sediment and a synthetic nacl cacl2 solution at elevated pressure and temperatures were conducted in an attempt to mimic early subduction zone processes the results demonstrate that be is mobilized under elevated pressure and temperature with a strong ph dependence the be mobilization provides an explanation of be 10 enrichment in arc volcanic rocks and supports the argument of the importance of the fluid processes in subduction zones at convergent margins