groundwater transport of strontium 90 in a glacial outwash environment as part of the investigation of groundwater contamination at a uranium scrap recovery plant at wood river junction rhode island laboratory experiments led to the development of a model for predicting the transport of strontium 90 in glacial outwash sediments based on an approximate mechanism for ion exchange the multicomponent system was simplified to two components by regarding all exchangeable cations other than strontium 90 as a single component the binary ion exchange parameter was a function of the variable total ion concentration a one dimensional solute transport model was formulated to evaluate the time necessary for natural groundwater flow to remove the strontium 90 contamination plume from the groundwater system to the pawcatuck river the finite difference transport equations were solved sequentially for total ion concentrations then strontium 90 concentrations clay free quartz and feldspar sands at the study site have little potential for strontium 90 sorption and high calcium magnesium and sodium concentrations compete for the few ion exchange sites as the total ion concentration plume moves out of the system ion exchange of strontium 90 increases reducing the strontium 90 concentration in the groundwater cleanout times predicted using the binary ion exchange mechanism were about two thirds of those predicted using a constant distribution coefficient it is suggested that this type of model can simulate solute transport more realistically in many groundwater systems where the total ion concentration is not constant

changes in antarctic bottom water properties in the western south atlantic in the late 1980s data collected in 1988 1989 as part of the south atlantic ventilation experiment have been combined with the historical database to study the circulation and water mass variability of the abyssal water in the argentine basin a map of potential temperature at 4000 m used as an indication of geostrophic shear defines a south and western intensified crescent shaped abyssal recirculation within this recirculation and its northward extension to the brazil basin antarctic bottom water aabw properties have undergone two modifications during the 1980s 1 the water mass cooled 0 05 c and freshened 0 008 in salinity ratio on surfaces of constant density 2 the densest layer of aabw was altered to less dense water through mixing or advection out of the study area this water mass change does not appear to have affected the flow pattern data collected in 1983 and 1988 to the north in the brazil basin show penetration of the freshwater mass in the deep western boundary current to between 18 s and 10 s indicating very rapid propagation of the anomaly from the argentine basin into the brazil basin as a deep western boundary current it is suggested that open ocean convective events within the weddell sea contributed to the change in aabw documented here

nature of and controls on volcanism in the ca 2 32 2 06ga pretoria group transvaal supergroup kaapvaal craton south africa abstract the time of deposition of the pretoria group between 2 32 and 2 06 ga on south africa s kaapvaal craton was characterized by the first major increase in atmospheric oxygen it was accompanied by the extrusion of significant thicknesses of volcanic deposits namely the bushy bend lavas of the timeball hill formation the hekpoort formation and the machadodorp volcanic member of the silverton formation marking the three major volcanic events within the transvaal supergroup which are thought to be precursors to the succeeding bushveld complex magmatism the bushy bend lava member of the timeball hill formation is characterized by subaqueous basaltic andesitic fissure eruptions with fumarolic activity and probably minor subaerial explosive eruptions in the hinterland of the transvaal supergroup basin the subaerial volcanism of the hekpoort formation appears to have been dominated by fissure eruptions with a preponderance of lava flows and locally important pyroclastic material intermittent hiatuses in volcanism were marked by local lacustrine shale deposition finally the machadodorp lava member can be interpreted as the deposits of several seamounts aligned along a fissure probably within an extensional environment the geodynamic control inferred for the evolution of the pretoria group basin encompasses two cycles of prerift uplift subsequent mechanical rifting and long lived thermal subsidence the limited extent of the bushy bend lavas in the south of the pretoria group depository attests to the likelihood that volcanism accompanying the first rifting event was short lived in contrast the second rifting cycle postulated for the pretoria group basin has a strong association with widespread and large scale volcanism of the hekpoort ongeluk flood basalts which may have been plume related the scale of the second cycle volcanism and its importance in influencing the upper part of the pretoria group basin fill is underlined by the machadodorp volcanism probably related to hot spot volcanism as the ongeluk hekpoort plume waned

environmental responses of the northeast antarctic peninsula to the holocene climate variability in this study we present a unique high resolution holocene record of oceanographic and climatic change based on analyses of diatom assemblages combined with biomarker data from a sediment core collected from the vega drift eastern antarctic peninsula eap these data add to the climate framework already established by high resolution marine sedimentary records from the palmer deep western antarctic peninsula wap heavy sea ice conditions and reduced primary productivity were observed prior to 7 4 ka b p in relation with the proximity of the glacial ice melt and calving subsequent holocene oceanographic conditions were controlled by the interactions between the westerlies antarctic circumpolar current acc weddell gyre dynamics a warm period characterized by short seasonal sea ice duration associated with a southern shift of both acc and westerlies field persisted until 5 ka b p this warm episode was then followed by climate deterioration during the middle to late holocene 5 to 1 9 ka b p with a gradual increase in annual sea ice duration triggered by the expansion of the weddell gyre and a strong oceanic connection from the eap to the wap increase of benthic diatom species during this period was indicative of more summer autumn storms which was consistent with changes in synoptic atmospheric circulation and the establishment of low to high latitude teleconnections finally the multicentennial scale variability of the weddell gyre intensity and storm frequency during the late holocene appeared to be associated with the increased el nino southern oscillation frequency

sedimentological study of the chernobyl npp site to schematise radionuclide migration conditions the approach methods and results of a sedimentological study of a near surface stratum of late pleistocene holocene deposits in the near zone 5 10 km radius of the chernobyl nuclear power plant are presented sedimentological analyses are carried out at three levels of detail regional local and object scale the unsaturated zone and unconfined aquifer at the site are composed of two main genetic types of deposits aeolian and alluvial including several dynamic facies consideration of lithological properties leads to following ranking of the main genetic sediments facies with respect to radionuclide migration retardation potential aeolian alluvial channel alluvial overbank alluvial abandoned channel based on sedimentological interpretations the geological environment is schematised into a set of typical geological sections possessing different radionuclide retardation potential

interpretation of ph and eh trends in a fluvial sand aquifer system ground waters and aquifer materials from a shallow fluvial sand aquifer system 1 km long flow path were sampled and analyzed to determine the hydrogeochemical processes affecting ph and eh measured pt electrode potential the aquifer system is a fine grained sand k 10 3 cm s composed principally of quartz and plagioclase 70 of all grains with minor biotite partially altered to vermicuiite and trace amounts of calcite acid neutralization capacity measurements and x ray diffractograms suggest that acid precipitation recharging the aquifer undergoes a two step neutralization process the first step involves reactions with the surfaces of mineral grains mainly with plagioclase and biotite and the second step involves an irreversible neutralization involving biotite alteration to vermiculite and carbonate mineral dissolution during migration through deep confined parts of the aquifer ground waters attain equilibrium with calcite a thermodynamically based redox model of a closed oxidant system satisfactorily accounts for the sequential reduction of dissolved oxygen ferric oxides and sulfate in the aquifer by the oxidation of dissolved organic carbon and for oxygen only ferrous iron because of the problems of using pt electrodes in ground waters it is recommended that eh measurements be supplemented with dissolved oxygen and sulfide measurements

the present and past bottom current flow regime around the sediment drifts on the continental rise west of the antarctic peninsula throughout the last decade large sediment drifts located on the upper continental rise west of the antarctic peninsula were the target of oceanographic measurements bathymetric mapping seismic investigations shallow sediment coring and deep sea drilling by ocean drilling program odp leg 178 these studies concluded that for most of the late neogene and quaternary a generally sw ward directed bottom current affected the deposition on the drifts in particular during glacial periods the deposition was additionally influenced by nw ward directed transport of terrigenous detritus supplied by turbidity currents from the antarctic peninsula continental slope in a recent study however the palaeomagnetic signal of the drift sediments recovered at two odp leg 178 sites 1095 and 1101 was interpreted to provide spatial and directional information on the physical record of the ne ward flowing antarctic circumpolar current acc here we investigate the link between the clockwise flowing acc and the generally sw wards flowing near bottom contour current we show that at the odp leg 178 sites on the western antarctic peninsula continental margin the acc only affects the ocean circulation above ca 1000 m water depth therefore the signal of acc flow might only be archived in the ice rafted debris ird content of the drift sediments however the ird from the leg 178 sites accounts for only a small proportion of the drift sediments and is dominantly of local origin past variability of bottom water flow around the sediment drifts was reconstructed on the basis of seismic studies and clay mineralogical and grain size analyses these reconstructions provide useful information about both downstream direction and velocity changes of the bottom current and point to its sw ward flow along the upper rise during at least the last 9 4 ma

circumpolar influences on the weddell sea indication of an antarctic circumpolar coastal wave abstract the antarctic circumpolar wave is now a well known feature that can be detected in atmospheric oceanic mixed layer and sea ice data in this coupled ice ocean model driven by 40 yr of daily atmospheric forcing data it represents a significant part of the interannual variability linking the sea ice and water mass formation processes in the weddell sea with other areas in the antarctic water ring in addition these model results show a decadal period wavelike anomaly pattern near the coast of antarctica propagating westward at about 2 cm s 1 this coastally trapped bottom intensified phenomenon likely has important effects on the dense water formation rate in the weddell sea and even the occurrence of the weddell polynya

freshening of the ross sea during the late 20th century ocean measurements in the ross sea over the past four decades one of the longest records near antarctica reveal marked decreases in shelf water salinity and the surface salinity within the ross gyre these changes have been accompanied by atmospheric warming on ross island ocean warming at depths of 300 meters north of the continental shelf a more negative southern oscillation index and thinning of southeast pacific ice shelves the freshening appears to have resulted from a combination of factors including increased precipitation reduced sea ice production and increased melting of the west antarctic ice sheet

the late quaternary geology of the chalk river region ontario and quebec glacial ice covered the chalk river area through most of the wisconsin stage about 11 300 years ago an ice retreat was followed immediately by a short incursion of champlain sea waters which deposited at least 2 5 m of clay silt and sand a local readvance probably associated with the st narcisse event deposited till on the marine sediments following the final retreat of the ice from the area lacustrine and aeolian deposition occurred locally for a short time about 10 500 years ago the north bay drainage route opened greatly increasing the discharge of the ottawa river a faint terrace at a present elevation of 209 m probably formed at this time changes in the drainage routes of proglacial lakes and in the rate of ice retreat caused a general decrease in discharge rates and resulted in the formation of pronounced terraces now at 180 160 and 129 m and fainter terraces at 170 141 and 137 m by about 5000 years bp the north bay outlet closed and the river fell to approximately 111 m it

a seasonal cycle in the export of bottom water from the weddell sea dense water formed over the antarctic continental shelf rapidly descends into the deep ocean where it spreads throughout the global ocean as antarctic bottom water1 2 the coldest and most voluminous component of this water mass is weddell sea bottom water1 3 4 5 6 7 here we present observations over eight years of the temperature and salinity stratification in the lowermost ocean southeast of the south orkney islands marking the export of weddell sea bottom water we observe a pronounced seasonal cycle in bottom temperatures with a cold pulse in may june and a warm one in october november but the timing of these phases varies each year we detect the coldest bottom water in 1999 and 2002 whereas there was no cold phase in 2000 on the basis of current velocities and water mass characteristics we infer that the pulses originate from the southwest weddell sea we propose that the seasonal fluctuations of weddell sea bottom water properties are governed by the seasonal cycle of the winds over the western margin of the weddell sea interannual fluctuations are linked to the variability of the wind driven weddell sea gyre and hence to large scale climate phenomena such as the southern annular mode and el nino southern oscillation

can dispersive pressure cause inverse grading in grain flows grain flows in the collisional regime are self regulated in such a way that dispersive pressure at every level tends to balance static pressure and so cannot promote the upward segregation of large particles in a steady flow le roux adds new insights to this analysis by pointing out that dispersive and static pressures would not balance in unsteady flows when shear strain rate increases in a grain flow dispersive pressure which is positively correlated to shear strain rate increases too and the gradient of dispersive pressure becomes higher than the gradient of static pressure as a consequence the grain flow expands thus lowering the dispersive pressure until the two gradients reequilibrate during the

oceanic heat transport onto the amundsen sea shelf through a submarine glacial trough glaciers which drain the west antarctic ice sheet wais into the amundsen sea are accelerating and thinning rapidly these observations have been attributed to the regional oceanography whereby heat contained within circumpolar deep water cdw drives the basal melting of floating glaciers on the basis of new data we calculate that 2 8 terra watts 1012 of oceanic heat flow onto the continental shelf and toward the glaciers via a submarine glacial trough this is enough to account for most of the basal melting in the entire region suggesting the ocean is supplying an excess of heat toward the antarctic continent

a possible link between the weddell polynya and the southern annular mode abstract shortly after the advent of the first imaging passive microwave sensor on board a research satellite an anomalous climate feature was observed within the weddell sea during the years 1974 1976 a 250 103 km2 area within the seasonal sea ice cover was virtually free of winter sea ice this feature the weddell polynya was created as sea ice formation was inhibited by ocean convection that injected relatively warm deep water into the surface layer though smaller less persistent polynyas associated with topographically induced upwelling at maud rise frequently form in the area there has not been a reoccurrence of the weddell polynya since 1976 archived observations of the surface layer salinity within the weddell gyre suggest that the weddell polynya may have been induced by a prolonged period of negative southern annular mode sam during negative sam the weddell sea experiences colder and drier atmospheric conditions making for a saltier surface layer with reduced pycnocline stability t

twentieth century global mean sea level rise is the whole greater than the sum of the parts confidence in projections of global mean sea level rise gmslr depends on an ability to account for gmslr during the twentieth century there are contributions from ocean thermal expansion mass loss from glaciers and ice sheets groundwater extraction and reservoir impoundment progress has been made toward solving the enigma of twentieth century gmslr which is that the observed gmslr has previously been found to exceed the sum of estimated contributions especially for the earlier decades the authors propose the following thermal expansion simulated by climate models may previously have been underestimated because of their not including volcanic forcing in their control state the rate of glacier mass loss was larger than previously estimated and was not smaller in the first half than in the second half of the century the greenland ice sheet could have made a positive contribution throughout the century and groundwater depletion and reservoir impoundment which are of opposite sign may have been approximately equal in magnitude it is possible to reconstruct the time series of gmslr from the quantified contributions apart from a constant residual term which is small enough to be explained as a long term contribution from the antarctic ice sheet the reconstructions account for the observation that the rate of gmslr was not much larger during the last 50 years than during the twentieth century as a whole despite the increasing anthropogenic forcing semiempirical methods for projecting gmslr depend on the existence of a relationship between global climate change and the rate of gmslr but the implication of the authors closure of the budget is that such a relationship is weak or absent during the twentieth century

non hawaiian lithostratigraphy of louisville seamounts and the formation of high latitude oceanic islands and guyots guyots are large seamounts with a flat summit that is generally believed to form due to constructional biogenic and or erosional processes during the formation of volcanic islands however despite their large abundance in the oceans there are still very few direct constraints on the nature and formation of guyots in particular those formed at high latitude that lack a thick cap of shallow marine carbonate rocks it is largely accepted based on geophysical constraints and surficial observations sampling that the summit platform of these guyots is shaped by wave abrasion during post volcanic subsidence of volcanic islands here we provide novel constraints on this hypothesis and the summit geology of guyots with a lithostratigraphic analysis of cores from three louisville seamounts south pacific collected during expedition 330 of the integrated ocean drilling program iodp thirteen lithofacies of sedimentary and volcanic deposits are described which include facies not previously recognized on the top of guyots and offer a new insight into the formation of high latitude oceanic islands on a fast moving plate our results reveal that the lithostratigraphy of louisville seamounts preserves a very consistent record of the formation and drowning of volcanic islands with from bottom to top i volcaniclastic sequences with abundant lava fed delta deposits ii submarine to subaerial shield lava flows iii post volcanic shallow to deeper marine sedimentary rocks lacking thick reef deposits iv post erosional rejuvenated volcanic rocks and v pelagic sediments recognition of erosional boundaries between subaerial lava flows and shallow marine sedimentary rocks provides novel support for post volcanic wave planation of guyots however the summit geology of louisville seamounts is dissimilar to that of high latitude hawaiian emperor guyots that have emplaced in a similar tectonic and environmental setting and that include thicker lava stacks with apparently little lava fed delta deposits to explain observed lithostratigraphic discrepancy we propose that louisville seamounts represent a distinct type of intraplate ocean volcano characterized by formation of a smaller island with a central shield volcano surrounded by extended shallow marine shelves formed by lava fed deltas in this interpretation the summit platform of louisville type guyots results from early syn volcanic subaerial to shallow marine constructional volcanic processes and marine erosion enhanced by later post volcanic wave planation this contrasts with larger hawaiian edifices that are capped by thicker shield volcanoes and that develop an extended wave planation surface during post volcanic subsidence in the absence of efficient coral growth the difference between hawaiian and louisville type volcanic islands and guyots can be explained by contrasted dynamic disequilibrium between magmatic growth erosion and subsidence during the island building stage unlike hawaiian type volcanoes louisville seamounts are characterized by alkaline magmatism that extends from the late seamount to island stages this supports more limited magmatic growth during the formation of louisville islands and we hypothesize that this promotes the formation of ephemeral shallow marine platforms and extended lava fed deltas hawaiian type volcanoes and guyots are unusually large in the population of intraplate ocean volcanoes louisville type guyots as defined in this study could therefore represent a very common but yet poorly documented mode of oceanic island formation in the pacific ocean and other similar fast moving plate settings

rapid freshening of antarctic bottom water formed in the indian and pacific oceans 1 repeat hydrographic sections occupied in 1995 and 2005 reveal a rapid decline in the salinity and density of antarctic bottom water throughout the australian antarctic basin the basin wide shift of the deep potential temperature salinity s relationship reflects freshening of both the indian and pacific sources of antarctic bottom water the s curves diverge for waters cooler than 0 1 c corresponding to a layer up to 1000 m thick over the antarctic continental slope and rise changes over the last decade are in the same direction but more rapid than those observed between the late 1960s and the 1990s when combined with recent observations of similar freshening of north atlantic deep water these results demonstrate that dense water formed in both hemispheres is freshening in response to changes in the high latitude freshwater balance and rapidly transmitting the signature of changes in surface climate into the deep ocean

basin evolution within the kitakami massif northeast japan relationship between sedimentation tectonics and volcanism in an incipient neogene continental back arc basin abstract the ichinohe basin in the western margin of the kitakami massif northeast japan consists of the early to middle miocene yotsuyaku and keiseitoge formations and represents the incipient stage of neogene back arc sedimentation that extends toward the north and northwest megaclast breccias derived from mesozoic basement rocks of the kitakami massif were transported from southern areas as debris flows the debris flow deposits of the yotsuyaku formation grade northwards along the basin axis into clast supported braided stream deposits where floodplains developed in the center of the basin voluminous volcanic eruptives of the keiseitoge formation were derived from eastern and southeastern volcanic ranges and formed transversal distributaries the deposition of both clastic and pyroclastic sediments suggests that volcanism and tectonic uplift took place simultaneously during basin evolution parallel laminated fine grained sediments intercalated with lignite beds suggest lacustrine deposition and large cross beds of volcanic breccias indicate gilbert type progradation into the lakes a number of small lakes in the center of the basin was probably formed as the result of damming tributary mouths by the main drainage from eastern and southeastern volcanoes or the reciprocal blocking by lahars and non volcanic debris flows derived from the southern uplift damming episodes produced by thick lava flows were not recognized in this study the evolution of the n s trending longitudinal ichinohe basin indicates that e w extensional tectonism related to the opening of the sea of japan affected not only the green tuff region to the west of the studied basin but also even the mesozoic basement during the miocene although the mingling of volcanic and basement derived deposits indicates the complexities of sedimentary facies and provenances our view of the stratigraphic architecture has relevance to the interpretation of the evolution of other extensional basin systems

clast orientations of the 1985 lahars of the nevado del ruiz colombia and implications for depositional processes abstract the eruption of the nevado del ruiz colombia on 13 november 1985 produced lahar flows resulting in extensive deposits the imbrications of flat clasts within the deposits as well as the orientations of large boulders resting on the surface of these deposits were measured the imbrications of the long a axes of the small clasts were found to dip 25 upstream against the lahar flow direction with a dispersion of 30 indicating transport of such clasts by normal stream flow contrary to this the boulders mostly on the surface of the deposits are aligned with their long a axes normally to the lahar flow indicating rolling on the surface both orienting mechanisms occurred in runoff pulses subsequent to the main event which produced only unordered deposits en masse thus the genesis of the emplacement of the lahar deposits in question has been mechanically explained

water mass conversion fluxes and mixing in the scotia sea diagnosed by an inverse model abstract an inverse box model of the scotia sea is constructed using hydrographic tracer and velocity data collected along the rim of the basin during the antarctic large scale box analysis and the role of the scotia sea albatross cruise the model provides an estimate of the time mean three dimensional circulation as the antarctic circumpolar current acc crosses the region it concurrently solves for geostrophic and wind driven ekman transports across the boundaries of the basin air sea driven diapycnal fluxes and interior diapycnal fluxes below the ocean surface an increase is diagnosed in the acc volume transport from 143 13 sv sv 106 m3 s 1 at drake passage to 149 16 sv on leaving the scotia sea supplied by the import of 5 9 1 7 sv of weddell sea deep water wsdw over the south scotia ridge there is a lateral redistribution of the transport primarily in response to a topographically induced branching of the 70 80 sv polar front pf jet and an increase in the transport associa

laboratory measurements of the strontium distribution coefficient kdsr for sediments from a shallow sand aquifer a batch method has been modified and improved for measuring strontium distribution coefficients kdsr for sediments from the shallow aquifer at chalk river an average measured kdsr value of 10 ml g for whole aquifer sediments compares favorably both with a field value of 7 ml g determined using the retardation equation and with an average kdsr of 10 ml g based on analytical results for aquifer sediments and coexisting groundwaters from a portion of the flow system that is contaminated with 90sr measurements of kdsr for mineralogically pure segregates indicate that vermiculite an alteration product of biotite is the most effective adsorbent phase kdsr results for grain size fractions suggest that the distribution of minerals with respect to grain size may strongly influence the kdsr of the whole sediment relationships between kdsr and exchangeable calcium on the sediments and competing cation concentration in the test solution indicate that electrostatic forces primarily control the sorption of strontium

export of weddell sea deep and bottom water an extensive set of conductivity temperature depth ctd lowered acoustic doppler current profiler ladcp data obtained within the northwestern weddell sea in august 1997 characterizes the dense water outflow from the weddell sea and overflow into the scotia sea along the outer rim of the weddell gyre there is a stream of relatively low salinity high oxygen weddell sea deep water defined as water between 0 and 0 7 c constituting a more ventilated form of this water mass than that found farther within the gyre its enhanced ventilation is due to injection of relatively low salinity shelf water found near the northern extreme of antarctic peninsula s weddell sea shelf shelf water too buoyant to descend to the deep sea floor the more ventilated form of weddell sea deep water flows northward along the eastern side of the south orkney plateau passing into the scotia sea rather than continuing along an eastward path in the northern weddell sea weddell sea bottom water also exhibits two forms a low salinity better oxygenated component confined to the outer rim of the weddell gyre and a more saline less oxygenated component observed farther into the gyre the more saline weddell sea bottom water is derived from the southwestern weddell sea where high salinity shelf water is abundant the less saline weddell sea bottom water like the more ventilated weddell sea deep water is derived from lower salinity shelf water at a point farther north along the antarctic peninsula transports of weddell sea deep and bottom water masses crossing 44 w estimated from one ladcp survey are 25 106 and 5 106 m3 s 1 respectively the low salinity better ventilated forms of weddell sea deep and bottom water flowing along the outer rim of the weddell gyre have the position and depth range that would lead to overflow of the topographic confines of the weddell basin whereas the more saline forms may be forced to recirculate within the weddell gyre

contrasting lithofacies architecture in ring plain deposits related to edifice construction and destruction the quaternary stratford and opunake formations egmont volcano new zealand abstract the early constructional and destructional history of ancestral egmont volcano is recorded by variations in lithofacies assemblages and architecture in volcaniclastic deposits making up the southern ring plain eruptive periods and edifice construction are recorded by aggradational sequences of debris flow deposits on the ring plain and numerous tephra deposits preserved on the lower flanks of the volcano the aggradational sequences represent fairly long term periods of accumulation when a succession of lahars delivered coarse grained sediment to the ring plain edifice destruction is recorded on the ring plain by deposits of debris avalanches and associated debris flows individual deposits represent rapid as much as 2 6 km 3 but episodic sedimentation over large areas up to 500 km 2 of the ring plain sedimentation following these events was slow with reworked tephra and lignite accumulating over most of the ring plain episodes of edifice destruction usually marked the beginning of long term quiescent intervals or periods of low frequency eruptive activity tephra deposits on the flanks of the volcano are not as abundant as in stratigraphic intervals representing periods of edifice construction

high chloride concentrations in the soil and groundwater under an oak hedge in the west of france an indicator of evapotranspiration and water movement chloride is a major anion in soil water and its concentration rises essentially as a function of evapotranspiration compared to herbaceous vegetation high transpiration rates are measured for isolated trees shelterbelts or hedgerows this article deals with the influence of a tree hedge on the soil and groundwater cl concentrations and the possibility of using cl as an indicator of transpiration and water movements near the tree rows cl concentrations were measured over 1 year at different depths in the unsaturated zone and in the groundwater along a transect intersecting a bottomland oak hedge we observed a strong spatial heterogeneity of cl concentrations with very high values up to 2 g l 1 in the unsaturated zone and 1 2 g l 1 in the upper part of the groundwater this contrasts with the low and homogeneous concentrations 60 70 mg l 1 in the deeper part of the groundwater cl accumulation in the unsaturated zone at the end of the vegetation season allows us to identify the active root zone extension of trees in winter upslope of the tree row downwards leaching partly renews the soil solution in the root zone while the slow water movement under the trees or farther downslope results in cl accumulation and leads to a salinization of the soil and groundwater this salinization is of the same order as experimental conditions produce negative effects on oak seedlings the measurement of cl concentrations in the unsaturated zone under tree rows at the end of the vegetation season would indicate whether certain topographic pedological or climatic conditions are likely to favour a strong salinization of the soil as observed in the present study copyright 2009 john wiley sons ltd

interpretation of recent southern hemisphere climate change climate variability in the high latitude southern hemisphere sh is dominated by the sh annular mode a large scale pattern of variability characterized by fluctuations in the strength of the circumpolar vortex we present evidence that recent trends in the sh tropospheric circulation can be interpreted as a bias toward the high index polarity of this pattern with stronger westerly flow encircling the polar cap it is argued that the largest and most significant tropospheric trends can be traced to recent trends in the lower stratospheric polar vortex which are due largely to photochemical ozone losses during the summer fall season the trend toward stronger circumpolar flow has contributed substantially to the observed warming over the antarctic peninsula and patagonia and to the cooling over eastern antarctica and the antarctic plateau

rapid bottom melting widespread near antarctic ice sheet grounding lines as continental ice from antarctica reaches the grounding line and begins to float its underside melts into the ocean results obtained with satellite radar interferometry reveal that bottom melt rates experienced by large outlet glaciers near their grounding lines are far higher than generally assumed the melting rate is positively correlated with thermal forcing increasing by 1 meter per year for each 0 1 c rise in ocean temperature where deep water has direct access to grounding lines glaciers and ice shelves are vulnerable to ongoing increases in ocean temperature

lahar facies of the mount dutton formation oligocene miocene in the marysvale volcanic field southwestern utah lahar facies of the mount dutton formation oligocene miocene marysvale volcanic field utah differ in clast size gradation presence or absence of a self supporting clast framework and to a lesser extent thickness the two most common of these fades matrix supported and either inversely graded facies 1a or nongraded 1b are absent from the closest modem analog mount st helens msh washington as are three others matrix supported normally graded 3 clast supported inversely graded 5 and clast supported nongraded 7a one common mount dutton fades matrix supported inversely to normally graded 4 is the peak flow overbank and transition lahar fades at msh one less common mount dutton lahar fades clast supported inversely to normally graded 6 is the sole facies or channel facies at msh mount dutton facies 2 thin matrix supported nongraded is present at msh as the lahar runout facies plots of maximum particle size mps versus bed thickness bth show significant positive correlations for seven fades as expected of debris flow deposits analogy with msh lahars suggests that mount dutton lahars were cohesionless debris flows grainflows that formed when turbulent floods or pyroclastic surges bulked by eroding material from their bed dispersive pressure produced inverse grading where shearing occurred inverse grading throughout beds is inherited from transient shearing episodes normal grading may be inherited from graded suspensions developed during bulking of turbulent flows or may reflect progressive deposition rather than frictional or cohesive freezing of a laterally graded flow slopes and intercepts of correlation lines for individual facies on an mps bth plot form natural groups three groups comprising facies 5 and 7a 1a and 1b and 3 and 4 differ chiefly in the intercept of the correlation line with the mps axis this intercept indicates thickness independent strength the result of cohesion and possibly other factors all three groups are stronger in this respect by a factor of 2 to 100 than a sampling of ancient nonvolcanic debris flows these three groups correspond to diamictite subfacies of nonvolcanic debris flows from the permian of colorado facies 6 is unlike other fades of the mount dutton formation but similar to ancient nonvolcanic debris flows in its strength properties it resembles whaleback bars that formed during nonuniform flow in the north fork lahars at msh two mount dutton fades 2 and 7b clast supported normally graded do not have a significant positive correlation of mps and bth they are probably deposits of hyper concentrated fluids not lahars in the strict sense

distribution of clay minerals and proxies for productivity in surface sediments of the bellingshausen and amundsen seas west antarctica relation to modern environmental conditions surface sediments from the antarctic continental margin in the bellingshausen and amundsen seas pacific sector of the southern ocean were investigated in order to decipher their capability to record modern environmental conditions spatial distribution of terrigenous sand and mud reflect regional differences in current induced redeposition of glaciogenic debris clay mineral assemblages in the shelf sediments are controlled by the supply of terrigenous detritus from source rocks in the adjacent hinterland suggesting the occurrence of yet unknown sedimentary rocks in the hinterland of the amundsen sea clay mineral distribution on the continental rise in the bellingshausen sea points to the continuation of a bottom current from the antarctic peninsula rise to at least 94 w foraminifer bearing and opal poor deposits prevail on the continental margin in the western bellingshausen sea and the amundsen sea whereas diatom bearing and carbonate free sediments characterize the eastern bellingshausen sea different modes of biological production which were deduced from accumulation rates of biogenic barium during marine isotope stage 1 and recent productivity measurements obviously control the spatial pattern of opal and carbonate bearing sediments in the study area

bioremediation of strontium and technetium contaminated groundwater using glycerol phosphate abstract groundwater at legacy nuclear facilities around the world is contaminated with radionuclides including strontium 90 and technetium 99 which are often present as co contaminants here we investigated whether biostimulation of indigenous microbial communities by glycerol phosphate can co treat 90sr through incorporation into phosphate biominerals and 99tc through microbially induced reduction of the sediment to form less mobile tc iv phases via reaction with reduced species e g fe ii results showed that 95 of sr was removed from solution in sediment microcosms treated with glycerol phosphate and sequential extraction showed that 18 of the sr in the resulting solid phase was associated with the ph 5 na acetate fraction and 75 was in the ion exchangeable fraction this removal and partitioning to recalcitrant phases during glycerol phosphate treatment was greater than in the untreated controls where only 60 of sr was removed from solution and of the solid associated sr 95 was present in the exchangeable fraction fitting of sr k edge exafs spectra confirmed these findings with shell by shell fitting suggesting 30 of sediment associated sr was present in a coordination environment consistent with phosphate biominerals following glycerol phosphate treatment whilst sr was present only as outer sphere complexes in the controls in addition 16s rrna sequencing of sediments stimulated with glycerol phosphate demonstrated the growth of potential phosphate solubilising species such as chryseobacterium and serratia spp finally glycerol phosphate treatment stimulated bioreduction via addition of electron donor in the form of glycerol to the system in turn this stimulated the removal of 99tc from solution concomitant with microbial fe iii reduction to form poorly soluble hydrous tc iv o2 like phases in sediments amended with an electron donor the microbial community also reflected the onset of bioreduction with an increased relative abundance of fe iii and sulfate reducing bacteria such as geothrix geobacter and desulfobulbus spp overall these results suggest application of glycerol phosphate offers a promising bioremediation strategy to co treat both 90sr and 99tc contaminated groundwaters and promotes the formation of sr phosphate and tc iv bearing biominerals when reducing conditions are maintained combined with past work which shows the scavenging of uranium from solution following addition of glycerol phosphate this extends the scope for glycerol phosphate as a treatment for radioactive contamination in groundwaters

influence of the southern annular mode on the sea ice ocean system 1 the global sea ice ocean model orca2 lim driven by the ncep ncar national centers for environmental prediction national center for atmospheric research reanalysis daily 2 m air temperatures and 10 m winds and by monthly climatologies for precipitation cloud cover and relative humidity is used to investigate the impact of the southern annular mode sam on the antarctic sea ice ocean system our results suggest that the response of the circumpolar southern ocean consists of an annular and a nonannular component for the sea ice cover the non annular component seems to be the most important the annular component strongly affects the overall patterns of the upper ocean circulation when the sam is in its positive phase a northward surface ekman drift a downwelling at about 45 degreess and an upwelling in the vicinity of the antarctic continent are simulated the non annular component has a significant impact at the regional scale especially in the weddell ross amundsen and bellingshausen seas in those regions the pressure pattern associated with the sam induces meridional winds which advect warmer air in the weddell sea and around the antarctic peninsula and colder air in the amundsen and ross seas this implies a dipole response of sea ice to the sam with on average a decrease in ice area in the weddell sea and around the antarctic peninsula and an increase in the ross and amundsen seas during years with a high sam index the long term trend in the observed sea ice area does not appear to be related to the trend in the sam index

geochemical influence of waste trench no 22t at chernobyl pilot site at the aquifer long term trends governing processes and implications for radionuclide migration abstract this article discusses and analyzes data for geochemical monitoring of groundwater collected in 1998 2008 at the international experimental radioecological study site chernobyl pilot site located in the red forest radioactive waste dump site in the chernobyl exclusion zone groundwater in the zone of influence of the studied waste trench no 22t was characterized by a specific geochemistry along with a high content of 90sr of an order of n 1000 n 10 000 bq l groundwater showed elevated concentrations of ca k no 3 so 4 2 and of some trace elements in particular stable sr and had more acidic ph values compared to background aquifer conditions the observed water quality changes are apparently related to degradation of organic matter pine forest remnants litter humus containing topsoil layer buried inside trench no 22t which have lead to acidification of groundwater and leaching of cations adsorbed on the exchange complex of soils buried inside the trench regime monitoring data for the project period of 1998 2008 shows a progressive decrease of concentrations of the leached ions accompanied by an increase of ph in the chemical plume emerging from the trench this can be explained by a combined effect of a gradual decrease of the inventory humification of the original organic matter inside the trench and of nutrient element uptake by roots of the newly planted pine forest on top of the trench the identified trends of evolution of geochemical regime favor attenuation of subsurface migration of 90sr from red forest waste dumps due to an increase of the 90sr distribution coefficients and stabilization of plumes of contaminated groundwater

three dimensional groundwater flow near narrow surface water bodies a series of natural gradient tracer tests was conducted to delineate groundwater flow patterns near a drainage ditch in glacial outwash of central wisconsin water level and precipitation data were collected to document factors that could contribute to temporal variations in the flow field year to year variations in recharge generated shifts in flow paths between replicate tracer experiments the field data provided the basis for numerical modeling designed to elucidate the sensitivity of flow paths to variations in recharge a three dimensional aspect of flow paths identified in this study is a wrap around pattern in which groundwater passes under a surface water body prior to turning in the downstream direction and continuing to migrate as subsurface flow this feature was suggested by the path of a tracer injected deep in the aquifer and was simulated at all recharge rates employed in the modeling the three dimensional nature of the flow field and temporal variability of flow paths can have important implications for design of monitoring networks near narrow surface water bodies

syn eruptive inter eruptive relations in the syn rift deposits of the precuyano cycle sierra de chacaico neuquen basin argentina abstract the syn rift volcanic successions of the upper triassic lower jurassic precuyano cycle i e the lapa formation from the sierra de chacaico in the neuquen basin argentina were studied in order to address the distinctive characteristics of accumulation during syn eruptive and inter eruptive periods in a depocentre associated with active volcanism and extensional tectonics in particular the syn rift fill in this area comprises a wide range of compositions as well as of transport and depositional processes lava flows coexist with pyroclastic and epiclastic deposits in the same accumulation space in order to analyse the complexities inherent in a volcanic environment subjected to extension five different accumulation units were identified in the area lava flow shallow intrusion units pyroclastic units volcaniclastic alluvial units polymictic alluvial units and lacustrine units the analysis of each of these units and of the relationship between them provided meaningful insights into the evolution of the syn rift sedimentary environments and the identification of different stages of effusive activity explosive activity and relative quiescence determining syn eruptive and inter eruptive rock units the relationship between these units was examined and two accumulation stages were defined the underfilled stage originates when the material supplied to the depocentre during the eruptive events is not enough to level the existent topography allowing the development of high gradient alluvial systems during the next inter eruptive period the overfilled stage occurs when extensive pyroclastic density current deposits choke the accumulation space during syn eruptive periods causing low gradient sedimentary systems to develop during the subsequent inter eruptive periods

seasonal inflow of warm water onto the southern weddell sea continental shelf antarctica 1 to capture the austral summer to winter transition in water mass properties over the southern weddell sea continental shelf and slope region 19 weddell seals were tagged with miniaturized conductivity temperature depth sensors in february 2011 during the following 8 months the instruments yielded about 9000 temperature salinity profiles from a previously undersampled area this allows for the first time a description of the seasonality of warm water intrusions onto the shelf as well as its southward extent towards the filchner ice shelf a temperature section across the filchner depression and eastern shelf shows a pronounced decrease in warm water inflow from summer to winter further supported by an almost 3 year long time series from a shelf break mooring the seasonal variability is related to the surface wind stress and an associated deepening of the off shelf core of warm deep water

lahar facies of the latest paleozoic arbasay formation geomorphological characters and paleoenvironment reconstruction of northern tian shan nw china abstract texturally well preserved lahars are exposed in the latest paleozoic arbasay formation northern tian shan the lahars consist primarily of two lithofacies massive poorly lithified diamictites and stratified moderately lithified gravelly sandstones the diamictites can be generally divided into two subfacies i e the matrix supported and the clast supported diamictites most diamictites are structureless and nongraded however some crudely stratified beds with a certain grading have also been found they are thick in beds and contain large clasts up to 3 m in dimension the gravelly sandstones display much finer particle size and have wedge or lenticular geometries large clasts are absent within them and the sorting characters are much better than the diamictites despite the different size grading the matrix and the clasts of the two lithofacies appear to be homogeneous the matrix is generally sandy mudstone the clasts comprise rhyolites dacites andesites andesitic basalts and basalts same to the co existing volcanic rocks suggesting they originate from the cognate volcanics the disorganized diamictites are supposed to deposit from a turbulent flood or pyroclastic surge the gravelly sandstone lithofacies are interpreted as sand rich flood flows or hyperconcentrated flood flows during the waning stage of a mass flow event the overall characteristics of the deposits suggest a mass flow dominated alluvial fan environment they are rapidly accumulated within small normal faults bounded depocenters the characteristics of the arbasay formation lahars together with the geochemistry characters of the co existing volcanic rocks clearly prove that they were deposited in a post collisional extensional regime la icp ms zircon dating of the intercalated fallout tuff sample provided an age of 314 4 3 4 ma mswd 1 6 suggesting they were deposited at late carboniferous therefore the north tian shan ocean must have closed before 314 ma and the initial basin type in northern tian shan should be extensional faulted basins rather foreland basins

depositional processes in large scale debris flow experiments this study examines the depositional process and characteristics of deposits of large scale experimental debris flows to 15 m3 composed of mixtures of gravel to 32 mm sand and mud the experiments were performed using a 95 m long 2 m wide debris flow flume that slopes 31 following release experimental debris flows invariably developed numerous shallow 10 cm deep surges sediment transported by surges accumulated abruptly on a 3 runout slope at the mouth of the flume deposits developed in a complex manner through a combination of shoving forward and shouldering aside previously deposited debris and through progressive vertical accretion progressive accretion by the experimental flows is contrary to commonly assumed en masse sedimentation by debris flows despite progressive sediment emplacement deposits were composed of unstratified accumulations of generally unsorted debris hence massively textured poorly sorted debris flow deposits are not emplaced uniquely en masse the depositional

variations of winter water properties and sea ice along the greenwich meridian on decadal time scales sea ice ocean interaction processes are of significant influence on the water mass formation in the weddell gyre on the basis of data obtained between 1984 and 2008 from eight repeat hydrographic sections moored instruments and profiling floats in the weddell gyre on the greenwich meridian almost all of them collected with rv polarstern we identified variations in the properties of the winter water and the sea ice draft in the winter water the salinity was relatively low throughout the 1990s with a minimum in 1992 and a maximum was observed in 2003 observations of sea ice draft by moored upward looking sonars are available from 1996 onwards in the southern part of the transect they display variations on a decadal time scale with a minimum in sea ice thickness in 1998 and an increase since then salinity variations in the winter water layer cannot be explained only by variations in sea ice formation and variable entrainment of underlying warm deep water but lateral advection of water and sea ice needs to be taken into account as well potential sources are melt water from the ice shelves in the western weddell sea or transport of water of low salinity entering the weddell gyre from the east accompanying variations of the properties of warm deep water are discussed in detail in a companion paper fahrbach et al 2011 this issue

weddell sea anomalies excitation propagation and possible consequences 1 antarctic marginal seas are susceptible to significant decadal variability as revealed by the analysis of a 200 year integration of a regional ice ocean model forced with the atmospheric output of the ipcc climate model echam5 mpiom the strongest signal occurs on the southern and western weddell sea continental shelf where changes in bottom salinity are initiated by a variable sea ice cover and modification of surface waters near the greenwich meridian related zonal shifts of the western rim current guide deep waters with different temperature out of the weddell sea with a deep boundary current the temperature signal propagates westward through southern drake passage and along the upper continental rise in the southeast pacific thereby influencing the hydrographic conditions on the continental shelf of bellingshausen amundsen and ross seas

build up and depositional dynamics of an arc front volcaniclastic complex the miocene tepoztlan formation transmexican volcanic belt central mexico volcanic terrains such as magmatic arcs are thought to display the most complex surface environments on earth ancient volcaniclastics are notoriously difficult to interpret as they describe the interplay between a single or several volcanoes and the environment the early miocene tepoztlan formation at the southern edge of the transmexican volcanic belt belongs to the few remnants of this ancestral magmatic arc and therefore is thought to represent an example of the initial phase of evolution of the transmexican volcanic belt based on geological mapping detailed logging of lithostratigraphic sections palaeocurrent data of sedimentary features and anisotropy of magnetic susceptibility mapping of two dimensional panels from outcrop to field scale and geochronological data in an area of ca 1000 km 2 three periods in the evolution of the tepoztlan formation were distinguished which lasted around 4 myr and are representative of a volcanic cycle edifice growth phases followed by collapse in a magmatic arc setting the volcaniclastic sediments accumulated in proximal to medial distances on partly coalescing aprons similar to volcanic ring plains around at least three different stratovolcanoes these volcanoes resulted from various eruptions separated by repose periods during the first phase of the evolution of the tepoztlan formation 22ae 8t o 22 ae2 ma deposition was dominated by fluvial sediments in a braided river setting pyroclastic material from small andesitic dacitic composite volcanoes in the near vicinity was mostly eroded and reworked by fluvial processes resulting in sediments ranging from cross bedded sand to an aggradational series of river gravels the second phase 22ae 2t o 21 ae3 ma was characterized by periods of strong volcanic activity resulting in voluminous accumulations of lava and tuff which temporarily overloaded and buried the original fluvial system with its detritus continuous build up of at least three major volcanic centres further accentuated the topography and in the third phase 21ae 3t o 18 ae8 ma mass flow processes represented by an increase of debris flow deposits became dominant marking a period of edifice destruction and flank failures

late quaternary marine sediments at chalk river ontario the occurrence of marine clays and silts in the chalk river area necessitates a revision of the previously accepted position of the northwestern extent of the champlain sea in the ottawa valley th

intra arc sedimentation in a low lying marginal arc eocene clarno formation central oregon abstract the clarno formation consists of andesitic volcaniclastic rocks interstratified with clayey paludal sediments and lava flows and cut locally by irregular hypabyssal stocks dikes and sills lateral lithofacies variations are pronounced and intrusive and extrusive volcanic rocks appear haphazardly emplaced throughout the formation a range of sedimentary environments is represented in the volcaniclastic sequences including near vent flow and breccia accumulations bouldery high gradient braided streams and relatively low gradient sandy tuff braidplains associated with paludal deposits we infer that the coarse grained volcaniclastic rocks of the clarno formation accumulated largely in volcanic flank and apron settings the formation s stratigraphy reflects an abundance of small volcanoes erupting into sedimentary lowlands and only a few scattered remnants of large central vent volcanoes are known the absence of systematic variation across a large outcrop belt argues against derivation of the succession from a line of volcanoes beyond the reaches of the present outcrop we infer that the arc was composed of small to medium size volcanoes arranged haphazardly across a broad area the sedimentary succession most probably accumulated in a series of intra arc depressions formed by diffuse block rotation driven by oblique subduction during the eocene