chemical and physical denudation in the amazon river basin we present major and trace element data on the suspended and dissolved phases of the amazon river and its main tributaries the sr isotopic composition of the dissolved load is also reported special attention is paid to the abundances of ree and to their fractionation between the dissolved and suspended phase the rivers of the amazon basin are among the richest in dissolved ree and are similar to the rivers of the congo system however a greater range of fractionation between lree and hree is reported here at a global scale the rivers have intermediate patterns between those of the congo system and those of high ph rivers such as the indus and mississippi rivers only few elements rb u ba k na sr and ca are mobilized by silicate weathering these elements are strongly depleted in the suspended phase with respect to upper continental crust in the dissolved load these elements are controlled by atmospheric inputs and the weathering of the main lithologies we propose a model based on mass budget equations that allow the proportions derived from the different sources to be calculated as a consequence silicate carbonate and evaporite weathering rates can be estimated as well as the consumption of co2 by weathering of each of these lithologies physical weathering rates can be estimated by two complementary approaches on the one hand the multi year average of suspended sediments yields can be used to estimate physical denudation on the other hand we have developed a steady state model of erosion that allows us to calculate physical erosion rates on the basis of the dissolved load of rivers a mean crustal composition is assumed in this model for the rock sources of the drainage basins comparison of the rates predicted by the model to the observed rates shows good agreement for the lowland rivers but a strong discrepancy for the rivers derived from the andes andean rivers solimoes madeira and amazon have observed sediment yields much greater than those predicted according to the steady state model of chemical and physical weathering two interpretations can account for this inconsistency the first is that these rivers are not in steady state and hence that the soils are being destroyed the second requires that the local continental crust is different from the average continental crust of taylor and mclennan and contains a large proportion of sedimentary rocks using the measured sediment yields and assuming a steady state we can estimate the amount of sediment recycling for each drainage basin for the amazon at santarem we find that at least 25 of the mass of the upper continental crust of the amazon drainage basin is constituted of recycled material

the interrelation of glaciotectonic and glaciodepositional processes within the glacial environment abstract in recent years it has been recognised that ice sediment coupling occurred beneath the quaternary ice sheets that advanced over the soft sediments of lowland areas this paper looks in detail at the effects of this coupling on the sediments which results in glaciotectonic deformation and also discusses the interaction of deformation and deposition within the subglacial environment two types of glaciotectonic deformation are discussed that are produced by the active movement of ice 1 proglacial tectonics at the margin which include compressive fold styles such as listric thrusts and faults and open folding 2 subglacial tectonics formed beneath the glacier which include fold styles resulting from simple shear and represent a soft rock purely dynamic shear zone styles of deformation associated with stagnant ice are also investigated we argue that glaciotectonic deformation is a common phenomenon and an integral part of geological record from continental ice sheets it is suggested that zones of deformation within the sediment are related to similar zones of strain in the ice sheet and complex deformation sequences are produced by the superimposition of these differing styles upon one another as the ice sheet advances and retreats it is also argued that subglacial deposition and deformation are related and that on soft beds underformed till is rare whilst deformed till is very common

dissolved constituents and sr isotopes in river waters from a mountainous island the danshuei drainage system in northern taiwan abstract taiwan is a typical active orogenic belt situated at the collision boundary between the eurasian continental plate and the philippine sea plate dissolved major and trace constituents as well as sr and sr isotopes in river waters collected from the danshuei river basin in northern taiwan have been studied to evaluate chemical weathering processes the results of principal component analysis show that the ion sources in these river waters can be categorized into 3 major components chemical weathering seasalt contribution and local anthropogenic input the chemical weathering is the most dominant factor that contributes about 85 of total variances significantly increased na cl and ca cl as well 87 sr 86 sr were observed in most upper stream samples the na cl and ca cl ratios in the dahan stream however are much higher than the shindien stream even though average rainfall is stronger in the shindien drainage basin chemical evidence from river waters supports less intense weathering in the region selective dissolution of secondary calcites explains the observed high ca cl sr cl and ca na in the dahan stream these results highlight the potential importance of tectonic factors such as uplift and physical erosion in studying chemical weathering in an active orogenic belt the variations of 87 sr 86 sr in the danshuei river are quite large reflecting some strata that released sr most of the upstream waters exhibit more radiogenic 87 sr 86 sr 0 713243 0 714338 due to weathering of ambient low grade metamorphic rocks 0 71678 0 72216 the distributions of cl sr and 87 sr 86 sr in the main stream were affected by somewhat conservative mixing with sources varing between ambient rocks and seasalt in the upper dahan stream heavy 87 sr 86 sr ratios were coincident with large deviations of na cl from the average seawater value as high as 40 the degree of chemical weathering in ambient rocks plays a dominant role in affecting the distribution of sr and 87 sr 86 sr in the danshuei river this isotopic characteristic makes 87 sr 86 sr an invaluable tracer for studying source mixing migration pathways and chemical weathering in an active orogenic belt

holocene floodplain soils along the rio mamore northern bolivia and their implications for understanding inundation and depositional patterns in seasonal wetland settings abstract the llanos de moxos lm in the bolivian amazon basin host one of the largest seasonally inundated savannah landscapes on earth very little is known of this area with regard to sedimentary dynamics soil formation or their relationship to longer term climatic and hydrological variability in this setting here we present a detailed study of three floodplain depositional sequences building up the inundation savannah along the mamore river in the central lm pleistocene sands and silts unit 1 are overlain by thick overbank deposits of mostly holocene age unit 2 on both sides of the mamore river and underline the importance of extensive flooding processes for the late quaternary sedimentary and geomorphic evolution of the lm the fine grained distal overbank sediments show signs of strong modification by hydromorphic processes and reflect spatial and temporal variations in flood inundation patterns in addition widespread dark gray to blackish soil and paleosol horizons are intercalated with the overbank sediments but lack evidence for significant weathering these horizons are likely the result of cumulative incorporation of organic material under conditions of particularly low sedimentation rates therefore their formation should be linked to processes such as channel migration longer term meanderbelt evolution avulsive drainage reorganization changes in sediment supply or climatically induced variations in flooding type frequency or magnitude the common occurrence of these floodplain soils in the early to mid holocene may thus reflect the combined effects of hydrological geomorphic and sedimentary changes during a drier mid holocene

geomorphology and evolution of the late pleistocene to holocene fluvial system in the south eastern llanos de moxos bolivian amazon in the bolivian amazon several paleochannel generations are preserved their wide spectrum of morphologies clearly provides crucial information on the type and magnitude of geomorphic and hydrological changes within the drainage network of the andean foreland therefore in this study we mapped geomorphological characteristics of paleochannels and applied radiocarbon and optically stimulated luminescence dating seven paleochannel generations are identified significant changes in sinuosity channel widths and river pattern are observed for the successive paleochannel generations our results clearly reflect at least three different geomorphic and hydrological periods in the evolution of the fluvial system since the late pleistocene changes in discharge and sediment load may be controlled by combinations of two interrelated mechanisms i spatial changes and re organizations of the drainage network in the upper catchment and or ii climate changes with their associated local to catchment scale modifications in vegetation cover and changes in discharge inundation frequencies and magnitudes which have likely affected the evolution of the fluvial system in the llanos de moxos in summary our study has revealed the enormous potential which geomorphic mapping and analysis combined with luminescence based chronologies hold for the reconstruction of the late pleistocene to recent fluvial system in a large portion of amazonia

comparing a three dimensional and a dupuit forchheimer solution for a circular recharge area in a confined aquifer abstract an exact closed form analytic solution is presented for three dimensional steady state flow due to a source disc the solution is used to model a circular recharge area at the upper boundary of a confined aquifer streamlines and contour plots of equipotentials are compared with those obtained from a dupuit forchheimer solution the latter solution is approximate in that resistance to vertical flow is ignored as a further illustration a groundwater contamination problem is solved that of a leaching circular pond in a uniform flow field some streamlines and the shape of the downstream plume are plotted for both the three dimensional and the dupuit forchheimer solution it appears that when the recharge area is sufficiently large the dupuit forchheimer solution is quite adequate particularly when tracing streamlines the results therefore confirm the validity of the dupuit forchheimer assumption when modeling regional flow even under circumstances of areal recharge however when the size of the recharge area is in the order of the aquifer thickness a truly three dimensional solution is needed

temporal transport of major and trace elements in the upper reaches of the xijiang river sw china this study investigated the temporal variations of major and trace element contents and controlling factors in the upper reaches of the xijiang river sw china the results showed the major ions principally derived from the weathering of carbonate and silicate rocks with a seasonal variation impacted by the monsoonal climate the contents of dissolved trace elements also varied seasonally in the two main tributaries the nanpan and beipan rivers most dissolved trace elements such as mn zn and pb being affected by anthropogenic contributions displayed a large seasonal variability from onefold to hundred fold while v rb and u show a relative stable trend uncorrelated with the different seasons suggesting a natural origin by rock weathering suspended particle matter in the nanpan and beipan rivers was depleted in ca mg na k and sr but enriched in al fe and sb compared to the upper crust uc values a binary mixture of silicate rich and carbonate rich sources dominates the behavior of elements such as ca and sr in riverine sediments while a third end member with an anthropogenic signature influenced the content of trace elements like mn sb pb zn cd cr and cu the enrichments of sb relative to the uc would be related to the mining activity in the studied area the study highlights the importance of investigating temporal variations of major and trace element contents of rivers controlled by the monsoon climate and impacted by human activity

postglacial rebound and the focal mechanisms of eastern canadian earthquakes a detailed numerical model of postglacial rebound for the eastern canadian arctic is described with special attention being paid to baffin island this numerical model is able to account for the observed uplift patterns as recorded by the relative sea level histories of discrete sites distributed throughout the study area these uplift patterns show regional trends so the same model can be used to interpolate between data sites and to estimate the uplift history at any arbitrary site within the study area by treating the lithosphere as a thin elastic plate spatial variations in the uplift pattern can be translated into estimates of lithospheric stress the model predicts the variations in uplift as a function of both space and time since deglaciation and can therefore be used to estimate the temporal evolution of lithospheric stress following deglaciation the stress so calculated is treated as a perturbation to an ambient stress field having its origin in other processes postglacial rebound is shown to

analytical solution for arbitrarily located multiwells in an anisotropic homogeneous confined aquifer 1 analytical solutions have been suggested to delineate the capture zone created by multiwells for the remediation design of contaminated groundwater these previous analytical solutions are often restricted to pumping wells only specific well locations a limited number of wells and isotropic aquifer an alternative analytical steady state solution was suggested to deal with arbitrarily located multiinjection pumping wells in an anisotropic homogeneous aquifer the solution can be an alternative solution for easily and conveniently calculating the hydraulic head and gradient in a complex flow field caused by multiinjection pumping wells at different rates and will consequently be useful for pump and treat design

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

dupuit forchheimer solutions for radial flow with linearly varying hydraulic conductivity or thickness of aquifer 1 this paper presents new analytical solutions for steady state piezometric heads in phreatic and confined aquifers with radial flow the new solutions utilize two constant head boundaries and a hydraulic conductivity k or thickness of aquifer h that is a linear function of radius r previous solutions applied constant k and h and they were usually based on one constant head boundary which might be superimposed on a solution that allowed a constant discharge or recharge at the center of the aquifer the previous solutions may be difficult to apply to real aquifers because constant k and h is usually an oversimplification of nature the dupuit forchheimer assumption implies that vertical head gradients are ignored the magnitude of the error introduced by allowing h h r is evaluated numerically in this paper

grain size control of river suspended sediment geochemistry clues from amazon river depth profiles residual solid products of erosion display a wide range of size density shape mineralogy and chemical composition and are hydrodynamically sorted in large river channels during their transport we characterize the chemical and isotopic variability of river sediments of the amazon basin collected at different water depths as a function of grain size absolute chemical concentrations and sr and nd isotopic ratios greatly varies along channel depth the al si ratio tightly linked to grain size distribution systematically decreases with depth mostly reflecting dilution by quartz minerals a double normalization diagram is proposed to correct from dilution effects elements define fan shaped patterns and can be classified in three different groups with respect to hydrodynamic sorting during transport in the amazon 1 poorly sorted insoluble elements like al fe th and rees 2 well sorted insoluble elements like zr and ti mainly carried by heavy minerals and 3 alkali na to cs and alkali earth elements mg to ba for which a large variety of patterns is observed related for alkali to their variable affinity for phyllosilicates sr isotopes show that the amazon river at the mouth is stratified the madeira and solimoes derived sediments being preferentially transported near the channel surface and at depth respectively the comparison between the solimoes and madeira rivers shows how the interplay between grain sorting weathering and crustal composition controls the composition of the suspended river sediments

particulate element inventory of the huanghe yellow river a large high turbidity river abstract suspended sediments from the river mouth to the upper portions of the huanghe yellow river were collected and analysed to determine their chemical composition comparison with other large world rivers indicates that trace element levels are relatively low in this high turbidity river natural weathering and erosion are of primary importance in controlling particulate element concentrations although the impact from anthropogenic activities is also visible finally input of particulate elements to the china sea is assessed from the river sediment load and compositions

anthropophile elements in river sediments overview from the seine river france in contrast to larger river systems that drain relatively pristine basins little is known about the sediment geochemistry of rivers impacted by intense human activities in this paper we present a systematic investigation of the anthropogenic overprints on element geochemistry in sediments of the human impacted seine river france most elements are fractionated by grain size as shown by the comparison between suspended particulate matter spm and riverbank deposits rbd the rbd are particularly coarse and enriched in carbonates and heavy minerals and thus in elements such as ba ca cr hf mg na rees sr ti th and zr although the enrichment depletion pattern of some elements e g k rees and zr can largely be explained by a binary mixture between two sources other elements such as ag bi cr cd co cu fe mo ni pb sb sn w and zn in spm in paris show that a third end member having anthropogenic characteristics is needed to account for their enrichment at low water stage these anthropophile elements with high enrichment factors efs relative to the upper continental crust ucc display a progressive enrichment downstream and different geochemical behaviors with respect to the hydrodynamic conditions e g grain size compared to elements having mainly a natural origin our findings emphasize the need for systematic studies of these anthropophile elements in other human impacted rivers using geochemical nor malization techniques and stress the importance of studying the chemical variability associated with hydro dynamic conditions when characterizing riverine element geochemistry and assessing their flux to the ocean

the sedimentology stratigraphy and 14c dating of a turf banked solifluction lobe evidence for holocene slope instability at okstindan northern norway

major and trace elements of river borne material the congo basin the congo river basin is the second largest drainage basin in the world after the amazon the materials carried by its main rivers provide the opportunity to study the products of denudation of a large fraction of the upper continental crust of the african continent this paper presents the chemical composition of the different phases carried in the congo rivers and is followed by a companion paper devoted to the modelling of major and trace elements the congo river between bangui and brazzaville as well as its main tributaries including a few organic rich rivers also called black rivers were sampled during the 1989 high water stage the three main phases suspended load dissolved load and bedload were analysed for twenty five major and trace elements concentrations normalized to the upper continental crust show that in each river suspended sediments and dissolved load are chemical complements for the most soluble elements ca na sr k ba rb and u while these elements are enriched in the dissolved loads they are considerably depleted in the corresponding suspended sediments this is consistent with their high mobility during weathering another type of complementarity is observed for zr and hf between suspended sediments and bedload related to the differential velocity of suspended sediments and zircons which are concentrated in bedloads compared to other rivers absolute dissolved concentrations of ca na sr k ba rb and u are remarkably low surprisingly high dissolved concentrations are found in the congo waters for other trace elements e g rees especially in the black rivers on a world scale these concentrations are among the highest measured in rivers and are shown to be ph dependent for a number of dissolved trace elements the dissolved loads are systematically normalized to the suspended loads for each river in order to remove the variations of the element abundances owing to source rock variations normalized diagrams for rees are presented and extended to the other elements they strongly support the argument that the apparent higher solubility of trace elements in the congo waters is due to the presence in the dissolved load of a colloidal phase as a result of 0 2 m filtration an important result is that these colloids are strongly depleted in fe and al with respect to the other elements finally the comparison of the dissolved suspended and sandy transport fluxes of each element in the congo basin rivers shows that although the proportions of for example the rees in the dissolved loads of the majority of the congo basin rivers is close to 10 of the total transport flux up to 80 of the rees are transported by the so called dissolved load in the black rivers

chemical weathering and atmospheric soil co2 uptake in the andean and foreland amazon basins abstract this study is a geochemical investigation of the andean and foreland basins of the amazon river at high spatial and time resolution carried out within the framework of the hybam research program hydro geodynamics of the amazon basin monthly sampling was carried out at 27 gauging stations located in the upper tributaries of the amazon basin from north to south the napo maranon ucayali madre de dios beni and mamore rivers the aim of this paper is to estimate the present day chemical weathering rate cwr as well as the flux of co 2 consumption from total and silicate weathering in the andes and foreland amazon basins and to discuss their distribution as a function of geomorphic and structural parameters based on the forward method the napo and other ecuadorian basins present high silicate weathering rates in comparison with the other basins we confirm that the maranon and ucayali rivers control the amazon hydrochemistry due to the presence of salt rocks and carbonates in these basins the madre de dios beni and mamore basins do not contribute much to the amazon dissolved load this north to south cwr gradient can be explained by the combination of decreasing weatherable lithology surface and decreasing runoff rates from the north to the south the foreland part of the basins or mountain lowland transition accounts for nearly the same proportion of the amazon silicate chemical weathering and carbonate chemical weathering fluxes as the andean part this result demonstrates the importance of the sediment accumulation areas in the amazon basin weathering budget and can be explained by the occurrence of a higher temperature the deposition of fresh sediments from andean erosion and a higher sediment residence time than in the upper part of the basin with a total co 2 consumption rate of 744 10 3 moles km year 1 and a silicate co 2 consumption rate of 300 10 3 moles km year 1 the upper amazon river andes foreland part is the most intense part of the amazon basin in terms of atmospheric co 2 consumption by weathering processes it is an important co 2 sink by weathering processes but accounts for only somewhat more than half of the co 2 consumption by silicate weathering of the amazon basin this result points out the importance of the lowland part of the basin in the inorganic c silicate budget the upper amazon accounts for 2 4 of the world s silicate co 2 consumption which is the same proportion as for the southern and southern east himalaya and tibetan plateau

reactivity of evaporites during burial an example from the jurassic of alabama the jurassic louann salt was the first significant sedimentary unit to accumulate in the gulf of mexico sedimentary basin br cl and sup 87 sr sup 86 sr ratios of halite from a single core into the top of the formation record the evaporation of normal seawater to bittern stage the bittern zone today consists of intergrown halite and sylvite the br and rb contents of the solid phases along with sup 87 sr sup 86 sr ratios and rb sr systematics are inconsistent with precipitation of the existing phases from seawater evaporated in jurassic time rather petrography and fluid inclusion and solid phase chemistry from the bittern zone is consistent with postdepositional water rock interaction which diagenetically modified a marine bittern assemblage to halite sylvite the chemistry of the br and rb rich saline formation waters characteristic of this area today likewise may reflect water evaporite interaction during burial

possible triggering of heinrich events by ice load induced earthquakes north atlantic sediments dating from the last ice age contain layers of rock fragments from northeastern canada so called heinrich layers 1 like modern iceberg borne sediments from greenland these layers have been attributed to ice rafting episodes1 2 3 six heinrich layers have been documented and correlated with climate changes4 5 6 7 8 the layers which are several centimetres thick contain negligible amounts of foraminifera which accumulate at a few millimetres per century implying that they were deposited over just a few years these ice rafting heinrich events are separated by progressively shorter intervals from about 40 to 6 kyr ref 9 and it has been suggested10 that they are related to the milankovitch cycles in the earth s orbital parameters11 alternatively they may be generated by forcing mechanisms arising from the internal dynamics of the laurentide ice sheet12 here we suggest the possibility that the heinrich events were precipitated by ice load induced earthquakes analogous to those produced by reservoir water loads13 we suggest that near its edge the laurentide ice sheet sheared the earth s crust inducing repeated failure that released the ice rafts this region along canada s northeastern seaboard shows evidence of both current14 15 and past seismic activity owing to postglacial rebound our model accounts for the intervals between both the heinrich events and the evidence of palaeoseismicity and can be tested by studying local sedimentary relationships

ice ages and nuclear waste isolation abstract the greatest natural threats to the integrity of the geological barriers to nuclear wastes isolated in cavities mined at depths between 400 and 800 m are likely during rapid retreats of future ice sheets the next major glacial retreat is expected at ca 70 ka well within the lifetime of high grade nuclear waste but it is not yet clear how long man s greenhouse effect may delay it this contribution discusses the potential problems posed to european waste isolation sites during erosion by ice and over pressurizing of meltwater and gasses in a lithosphere flexed by major ice sheets these depend on the target rocks and the location of the site with respect to the ice streams and margins of future ice sheets of particular size no sites are planned under the centres of future ice sheets in europe where end glacial earthquakes can be expected to reactivate major faults nor where ice can be expected to deepen and lengthen fjords along the atlantic coast sites in the alps may be vulnerable to radical changes in the patterns of glacial troughs the stability and geohydrology of sites in coastal areas beyond future ice margins are threatened by river gorges when sea level falls ca 125 m or in enclosed basins like the mediterranean ever lower the greatest problems are likely in lowland regions exposed by the rapid retreat of thick ice fronts where large lakes on or under thick warm based ice are dammed by more distal cold based ice groundwater in subhorizontal fractures dilated by glacial unloading may reach over pressures capable of hydraulically lifting megablocks of bedrock with fracture permeability and or the ice damming them so that less permeable substrates are susceptible to incisions eroded to depths of ca 360 at locations controlled mainly by ice topography kinematics and history

lateglacial and holocene environmental changes in ganga plain northern india abstract stable isotope elemental geochemistry and pollen analysis of a sediment profile from sanai lake central ganga plain were used to document climatic oscillations during the last 15 000 yr in indian subcontinent micaceous sandy sediments at the base of the profile indicate an active channel and humid conditions before 15 000 14c yr bp the channel was abandoned during comparatively arid conditions 15 000 13 000 14c yr bp and converted into a swamp enhanced humidity around 13 000 14c yr bp led to submergence of marshes and establishment of a large lake a dry phase is also identified around an estimated age of 11 500 10 500 14c yr bp which might correspond to the younger dryas event witnessed globally the early to mid holocene climatic optimum 10 000 5800 14c yr bp is characterised by a lake environment occurence of warmth loving aquatic plants lower 18o values of gastropod aragonite heavier 13corg values indicate a sensitive response of the lake ecology to the climatic warming and increased rainfall this is followed by an arid event during 5000 2000 14c yr bp and from 1700 14c yr bp there is evidence of climatic amelioration the sequence and magnitude of the millenium scale climatic oscillations documented along the lake profile correlate well with records from other parts of the indian subcontinent indicating that the recorded changes are an expression of broad scale probably global and climatic change

hydrogeochemical investigation of kucuk menderes river coastal wetland selcuk izmir turkey kucuk menderes river forms a rich coastal wetland inside in the selcuk plain three saline brackish lakes one swamp and kucuk menderes river are these wetlands components alkaline slightly alkaline type lakes are recharged from precipitation and karstic springs that discharge from marble schist and marble alluvium contacts in the northern and southern parts of the study area water types of the wetland are na cl and na ca mg hco3 cl in both rainy and dry seasons both seawater intrusion and evaporation as being the sources of the ions justify the presence of na cl na so4 and cl so4 in the wetland water environmental isotopes were used to identify the relationship between wetland and groundwater in the selcuk plain the 18o and d composition of wetland area samples have changed between 6 42 to 4 56 and 36 40 to 23 80 respectively the lakes and rivers are plotted on the mixing line by slope of 5 2 and these data indicate that wetland is affected from seawater intrusion the recharge area that was sampled in order to compare the wetland has ca hco3 water type with a neutral slightly alkaline ph values and the main hydrogeochemical process is weathering the different types of silicates iron manganese and selenium are the dominant minor ions due to the high biological activities and organic matters in the lakes there are two contamination risks for this wetland 1 waste disposal site and 2 water treatment plant where the purified waters are released into the river ec al as cd cu fe and zn values exceed those of aquatic life standards in the near future these sites will pose a danger for wetland wild life and surrounding irrigation water suppliers

neotectonics seismicity and stress in glaciated regions the melting of large ice caps over the span of many centuries to several millennia is an important agent of dynamic change within the solid earth fig 1 it induces significant redistributions of mass on the surface of the earth drives sea level and land elevation changes and readjusts lithospheric stresses in formerly glaciated areas and adjacent regions effects manifest as increased seismicity and eventually in powerful earthquakes it was an understanding that was apparent a century ago de geer 1888 kolderup 1913 but has found increased support during the 20th century in particular the discovery of the end glacial faults of northern scandinavia kujansuu 1964 lagerback 1979 olesen 1988 proved definitively that glacial loads and therefore climate can act as tectonic drivers over very short geological times fig 1 simplifed loading history for central fennoscandia during the last weichselian major glaciation modified after talbot 1999 ice thickness appears above the time axis and consequent crustal depression appears below the model illustrates how rapid vertical ice loading and unloading changes lead to far slower crustal depression or rebound and that the scale of crustal response is considerably less than the imposed ice mass fluctuations reflecting viscous flow of the

postglacial rebound and fault instability in fennoscandia summary the best available rebound model is used to investigate the role that postglacial rebound plays in triggering seismicity in fennoscandia the salient features of the model include tectonic stress due to spreading at the north atlantic ridge overburden pressure gravitationally self consistent ocean loading and the realistic deglaciation history and compressible earth model which best fits the sea level and ice data in fennoscandia the model predicts the spatio temporal evolution of the state of stress the magnitude of fault instability the timing of the onset of this instability and the mode of failure of lateglacial and postglacial seismicity the consistency of the predictions with the observations suggests that postglacial rebound is probably the cause of the large postglacial thrust faults observed in fennoscandia the model also predicts a uniform stress field and instability in central fennoscandia for the present with thrust faulting as the predicted mode of failure however the lack of spatial correlation of the present seismicity with the region of uplift and the existence of strike slip and normal modes of current seismicity are inconsistent with this model further unmodelled factors such as the presence of high angle faults in the central region of uplift along the baltic coast would be required in order to explain the pattern of seismicity today in terms of postglacial rebound stress the sensitivity of the model predictions to the evects of compressibility tectonic stress viscosity and ice model is also investigated for sites outside the ice margin it is found that the mode of failure is sensitive to the presence of tectonic stress and that the onset timing is also dependent on compressibility for sites within the ice margin the evect of earth rheology is shown to be small however ice load history is shown to have larger evects on the onset time of earthquakes and the magnitude of fault instability

three dimensional streamlines in dupuit forchheimer models an approximate method is presented for determining streamlines in three dimensions using two dimensional dupuit forchheimer models the latter models of horizontal flow which may comprise several aquifers are based on the assumption that the resistance to flow in the vertical direction is neglected this assumption does not preclude the occurrence of flow in the vertical direction vertical components of flow are determined in an approximate fashion by requiring continuity of flow the problem of leakage from a shallow pond above an unconfined aquifer is discussed as an example of determining streamlines in three dimensions the errors induced by the approximation are determined for a few idealized flow problems that can be solved exactly

geomorphic limits to climate induced increases in topographic relief recognition of the potential for strong dynamic coupling between atmospheric and tectonic processes has sparked intense cross disciplinary investigation and debate on the question of whether tectonics have driven long term climate change or vice versa it has been proposed that climate change might have driven the uplift of mountain summits through an isostatic response to valley incision because isostasy acts to compensate mean elevations the debate hinges on the question of whether climate change can significantly increase topographic relief or more precisely increase the volume of missing mass between summits and ridges here we show that in tectonically active mountain ranges geomorphic constraints allow only a relatively small increase in topographic relief in response to climate change thus although climate change may cause significant increases in denudation rates potentially establishing an important feedback between surficial and crustal processes neither fluvial nor glacial erosion is likely to induce significant isostatic peak uplift

glacio seismotectonics ice sheets crustal deformation and seismicity abstract the last decade has witnessed a significant growth in our understanding of the past and continuing effects of ice sheets and glaciers on contemporary crustal deformation and seismicity this growth has been driven largely by the emergence of postglacial rebound models pgm constrained by new field observations that incorporate increasingly realistic rheological mechanical and glacial parameters in this paper we highlight some of these recent field based investigations and new pgms and examine their implications for understanding crustal deformation and seismicity during glaciation and following deglaciation the emerging glacial rebound models outlined in the paper support the view that both tectonic stresses and glacial rebound stresses are needed to explain the distribution and style of contemporary earthquake activity in former glaciated shields of eastern canada and fennoscandia however many of these models neglect important parameters such as topography lateral variations in lithospheric strength and tectonic strain built up during glaciation in glaciated mountainous terrains glacial erosion may directly modulate tectonic deformation by resetting the orogenic topography and thereby providing an additional compensatory uplift mechanism such effects are likely to be important both in tectonically active orogens and in the mountainous regions of glaciated shields in general the short term response to ice fluctuations is similar to the earth s response to fluctuations in water reservoirs with the subsequent increase or decrease in seismicity which depends on the pre existing stress state when the ice fluctuations occur on the spatial scale and magnitude of the late pleistocene glaciation and deglaciation however the viscoelastic response of the earth especially the mantle causes significant changes in crustal deformation and earthquake activity that is spatially extensive and temporally complex the regions of greatest ice thickness and the regions marginal to the late pleistocene ice sheets indicate the most dramatic evidence of earthquake faulting the mantle response to these large ice mass fluctuations and the change in mass between the oceans and land caused and continues to cause measureable crustal deformation at hundreds of kilometres from the ice margins for both tectonically active and cratonic regions palaeoseismic investigations of late pleistocene and holocene faults are an important tool in evaluating earthquake hazard the predicted response of the earth over this time however is very dependent on the model assumed for most regions far more carefully designed field observations are needed to constrain the existing rheological and ice models

constraints on the geometry of the suasselka post glacial fault northern finland based on reflection seismic imaging abstract unloading of the ice during the last glacial period in northern fennoscandia is believed to have generated major faulting these faults often referred to as post glacial faults typically have clear surface exposures but their geometry at depth is poorly known in order to better understand the geometry at depth of the suasselka post glacial fault in finland three high resolution 2d reflection seismic profiles over the fault were reprocessed their total profile length is about 60 km and they were acquired as part of a major effort in finland to map the uppermost crust in mining areas the reprocessing led to significantly improved images that could be used to map the fault at depth two approximately n s striking profiles and one e w striking profile were reprocessed the different azimuths and the crooked nature of the profiles allowed the fault geometry to be relatively well constrained clear reflections from the fault dipping towards the se can be traced from the shallow subsurface down to about 3 km the strike and dip of two sets of dipping reflections in the stacked data along with geometrical constraints and cross dip analysis give a consistent dip of about 35 45 towards the se for the fault the strike and dip vary from n55e with a dip of 35 in the east to a strike of n48e with a dip of 45 in the west existence of the two sets of reflections indicates that the fault surface is non planar aside from allowing the geometry of the fault to be determined the seismic data show a complex reflectivity pattern in the area and indications of both reverse and normal movement along fault planes with similar orientation to the suasselka post glacial fault these images can be used as a basis for better characterizing the 3d geology of the area

1822 earthquake triggered homogenite in lake le bourget nw alps high resolution textural signatures of an earthquake induced historical homogenite layer are presented as well as its 3d distribution this homogeneous deposit is correlated with the ad 1822 event vii viii msk intensity the main historical earthquake of the french outer alps using 210pb dating and historical chronicles during this earthquake a violent lake water oscillation was reported seiche effect in the present study we discuss the influence of lake water oscillations during earthquake induced subaqueous slide through a pluridisciplinary analysis of subbottom sediments including high resolution seismic sidescan sonar and short gravity coring

the apure river geochemistry of major and selected trace elements in an orinoco river tributary coming from the andes venezuela the analysis of physicochemical variables and selected dissolved elements was performed on the apure river waters for 15 months the variables ph alkalinity dissolved o2 conductivity and na ca mg and cd concentrations showed maximum values during low water whereas k si fe al mn zn cu cr and dissolved organic carbon doc showed maximum concentrations during rising and high water five important factors were found to control the amount and temporal variability of the dissolved elements lithology hydrology vegetation floodplain processes redox conditions and organic complexation weathering of silicates carbonates and evaporites in the andes provides most of the proportion of na ca mg and hco3 to waters the temporal variability of these ions is controlled by a dilution process although si can be taken up by the biomass si and k can be leached from the floodplain by weathering of clays microbial decay of the submerged plants in the floodplain during the inundation periods provides doc and k to river waters and changes the redox conditions in water the changing redox conditions control the solubility of mn zn and fe dissolved mn is a function of ph dependent redox process whereas zn solubility is controlled by scavenging of zn during the oxidation of mn2 to mno2 positive relationships between al fe cu cr and doc suggest that these elements are complexed by organic colloids generated in the floodplain moreover the binding capacity of fe with doc increases under reducing conditions although cd seems to be provided by weathering in the andes several processes can affect the mobility of cd during transport copyright 2010 john wiley sons ltd

reverse slip offsets and axial fractures in road cut boreholes from the caledonides in finnmark northern norway neotectonic stress orientation indicators abstract reverse slip offsets of road cut drillholes and axial fractures developed in the walls of many such holes have been recorded from areas in the porsangerfjord and laksefjord districts of the caledonides of finnmark northern norway displacement vectors of the offset boreholes indicate movement towards 120 136 in phyllites of the laksefjord nappe at the base of the kalak nappe and in the gaissa nappe in western porsanger reverse slip offset is directed almost due east observations of the extensional axial fractures which are considered to have developed normal to the least principal in situ stress 3 at the time of blasting support a c ese wnw orientation of shmax at or close to the surface in these parts of finnmark possibly with a slightly more e w trend in western areas the consistency of orientation of these structural features is considered to reflect a regional stress pattern and is not merely a manifestation of the local geology or topography

dependence of horizontal stress magnitude on load dimension in glacial rebound models summary it has been proposed that the deglaciation of the northern hemisphere triggered large earthquakes within intraplate environments and in this paper we examine this hypothesis by evaluating quantitatively the stress state in the lithosphere produced by time dependent surface loads a series of models demonstrate the dependence of horizontal incremental stress in an elastic plate overlying an inviscid or viscoelastic mantle on the lateral extent of a load applied at the surface the horizontal stress is largest when the dominant wavelength that is twice the diameter of the load is close to eight times the elastic thickness of the plate when the mantle is inviscid and for the particular viscosity model employed in this paper close to 12 times the elastic thickness for a viscoelastic mantle at wavelengths close to the critical wavelength the horizontal incremental stress may be up to six times as large as the vertical incremental stress for appropriate earth model parameters amplification of horizontal stress is close to maximum for ice loads with a radius of 280 km comparable to the dimensions of the former ice sheet over great britain this amplification may be sufficiently large that loading by small ice sheets can lead to failure on marginally stable faults in contrast to the behaviour for large ice sheets the models also predict greater fault instability for fennoscandia than for the larger laurentide ice sheet consistent with the observation of large postglacial faults in northern sweden the model is used to predict the stability of faults and style of faulting due to rebound stresses in the absence of a background tectonic stress field since the last glacial maximum 18 000 years ago in northern europe within the formerly glaciated region thrust faulting is predicted to occur at the end of deglaciation and normal faulting is predicted to occur in peripheral regions for the entire period since the last glacial maximum

major and trace element geochemistry in the upper niger river mali physical and chemical weathering rates and co2 consumption this study describes the chemistry of the upper niger river system upstream of the inland delta in mali it constitutes the first geochemical investigation of suspended and dissolved loads of this region of the world the niger on its way between banankoro and ke macina and its tributary the bani river at douna were sampled during eight hydrological years from 1991 1992 to 1997 1998 major elements were determined for all 8 years and trace elements during 2 years 1996 1997 and 1997 1998 the total period of investigation is representative of the hydrological fluctuations over the last 25 years dissolved concentrations show that in comparison with other rivers the upper niger rivers are among the least mineralised and are strongly influenced by silicate rocks which underlie almost the totality of the basin the contribution of atmospheric precipitation to the rivers chemistry using the technique of marine contribution appears very low normalised to the upper crust the chemical composition of the different phases shows that in each tributary suspended sediment and dissolved load are chemically complementary for the most soluble elements ca na sr k ba rb and u the depletion of these elements in the suspended phase and the corresponding enrichment in the dissolved phase is related to their high chemical mobility during silicate weathering the variability over the hydrological year of trace elements in suspended matter has been attributed to the mixing between inputs of clay minerals and quartz the distribution of the dissolved particulate ratio in the upper niger basin leads to the conclusion that for the majority of elements the sediment content controls the quantity of elements in the dissolved phase as carbonate outcrops are insignificant in the upper niger basin it is possible to calculate chemical denudation rates by correcting water quality for atmospheric inputs for the studied period the denudation rates found range from 0 2 to 1 9 106 tons year corresponding to 26 103 to 100 103 mol co2 km2 year physical denudation rates were also estimated and range from 3 9 to 8 2 tons km2 year it appears that the low values of these chemical and physical denudation rates are related to a number of factors such as the lithology silicate rocks the lack of tectonism permitting thick soil formation that limits bedrock weathering and low precipitation limiting runoff finally a simple steady state model has been applied to the chemical composition of dissolved and solid products of silicate weathering this model shows a good agreement between the modelled and the measured values of the suspended sediment concentrations thus confirming the existence of steady state conditions in this tropical area

chemical weathering controls on variations in the molybdenum isotopic composition of river water evidence from large rivers in china abstract mo isotopic composition in large rivers is very important for understanding global mo cycle at present temporal variation signatures in the 98 95 mo in large rivers have not been investigated which hinder a comprehensive understanding on the mechanism for the variations of mo isotopic compositions in river water in this study we report a one year long time series march 2010 to march 2011 of the 98 95 mo of both the water and suspended particulates collected at guiping from the middle reaches of the xijiang river xjr and of the water 98 95 mo from the lower reaches of the huanghe river hhr or yellow river collected at lijin china the results indicate that the temporal variations in the concentration and 98 95 mo of dissolved mo in the xjr range from 4 32 to 10 5 nmol l mean 7 31 nmol l and 1 04 to 1 31 relative to nist 3134 mean 1 20 respectively but that the particulates have a lower 98 95 mo 0 18 to 0 58 analysis of the suspended particulates and other chemical parameters of the river water suggests that the weathering of silicates and sulfides is the main contributor to the dissolved mo content in the xjr subsequently the highly efficient preferential trapping of lighter 98 95 mo by weathering products such as clay minerals fe mn oxides and organic materials in soils and saprolites which are abundant in the tropical catchment is the key to the heavy mo isotope signatures in the xjr furthermore it seems that neither mo scavenging by suspended particulates during riverine transportation nor the weathering of sulfates significantly influences the 98 95 mo of the xjr water cross comparison among the 98 95 mo in the waters of the three largest rivers in china the changjiang cjr hhr and xjr indicates that the hhr has the highest mo concentrations but the lightest 98 95 mo the xjr has the lowest mo concentrations but the heaviest 98 95 mo and the values for the cjr are intermediate between those for the other two rivers this supports the conclusion that the efficiency of the selective trapping of mo by soils and saprolites is the main factor controlling 98 95 mo in these large rivers the tropical subtropical xjr catchment experiences intense chemical weathering the semi arid temperate hhr catchment experiences very little and the cjr catchment falls somewhere between the two such a relationship between water mo concentrations and 98 95 mo agrees with previous observations from many large rivers worldwide it is therefore suggested that chemical weathering on continents is the key to variations in the isotopic composition of mo in the waters of large rivers

an analytic element solution to unconfined flow near partially penetrating wells an analytic element solution for steady state unconfined flow near one or more partially penetrating wells in an ambient flow field has been developed the phreatic surface is modeled using a three dimensional version of the zhukovski function boundary conditions at control points on the phreatic surface and seepage face at the well are maintained by use of distributed singularities outside the flow domain the phreatic surface and seepage face for a single well is compared with two different numerical solutions and a laboratory experiment found in the literature a sample case showing flow near two wells in an ambient flow field is presented

riverine li isotope fractionation in the amazon river basin controlled by the weathering regimes we report li isotope composition 7li 7li of river borne dissolved and solid material in the largest river system on earth the amazon river basin to characterize li isotope fractionation arl a continental scale the 7li 7li in the dissolved load 1 2 to 32 is fractionated toward heavy values compared to the inferred bedrock 1 to 5 and the suspended sediments 6 8 to 0 5 as a result of the preferential incorporation of 66li into secondary minerals during weathering despite having very contrasted weathering and erosion regimes both andean headwaters and lowland rivers share similar ranges of dissolved 7li 7li 1 2 to 18 correlations between dissolved 7li 7li and li na and li mg ratios suggest that the proportion of li incorporated in secondary minerals during weathering act as the main control on the 7lidiss 7lidiss across the entire amazon basin a batch steady state fractionation model for andean and lowland rivers satisfactorily reproduces these variations with a fractionation factor between weathering products and dissolved load sec dis sec dis of 0 983 two types of supply limited weathering regimes can be identified for the lowlands clearwaters with dominant incorporation of li in secondary minerals and black waters e g rio negro where dissolution of secondary minerals enhanced by organic matter produces low 7li 7li apart from the black waters the 7li 7li of andean and lowland rivers is negatively correlated to the denudation rates with the lowest 7li 7li corresponding to the rivers having the highest denudation rates in contrast the main tributaries draining both the andes and the lowlands have higher 7li 7li compared to other rivers we propose that part of the dissolved li derived from weathering in the andes is re incorporated in sediments during transfer of water and sediments in floodplains and that this results in an increase of the dissolved 7li 7li along the course of these rivers unlike other rivers the dissolved 7li 7li in the main tributaries is best described by a rayleigh fractionation model with a fractionation factor sec dis sec dis of 0 991 altogether the control imposed by residence time in the weathering zone and floodplain processes results in i a non linear correlation between dissolved 7li 7li and the weathering intensity defined as w d and ii a positive relationship between the dissolved li flux and the denudation rate these results have important implications for the understanding of past ocean 7li 7li and its use as a paleo weathering proxy

chemical weathering in the drainage basin of a tropical watershed nsimi zoetele site cameroon comparison between organic poor and organic rich waters abstract this study deals with the weathering processes operating at the scale of a small catchment nsimi zoetele cameroon and is focused on the role of organic colloids on mineral weathering and transport of elements in natural waters samples of river spring and groundwaters from nsimi zoetele were filtered through membranes of decreasing pore size 0 22 m 0 025 m or 300 000 da 5000 da to separate colloidal fractions from the truly dissolved one major and trace elements and dissolved organic carbon doc were analysed in each fraction two kinds of waters can be distinguished in the catchment clear and coloured waters clear waters exhibit low concentrations of major and trace elements and doc elements are carried in these solutions in a true dissolved form except al and rare earth elements rees by contrast the higher abundances of al fe and trace elements in coloured waters are controlled by the colloidal fraction thermodynamic equilibrium calculations show that clear waters are in equilibrium with kaolinite and iron oxi hydroxide which are major minerals in the weathered soil for coloured waters the aqueous speciation of ca mg cu fe al la and th was calculated taking into account the complexes with humic acids speciation calculations for cu fe al la th show a strong complexation with humic acids in good agreement with the results of the filtration experiments by contrast although filtration experiments show a strong control of major cations by organic matter for example 75 for ca speciation calculations reveal that their complexes with humic ligands do not exceed a few percent of total dissolved elements this discrepancy is explained as an artefact induced by the organic colloids and occurring during the filtration procedure finally both filtration experiments and speciation calculations show that organic matter plays an important role in natural doc rich waters organic acids increase significantly the dissolution rates of silicates and oxi hydroxides and thus the amounts of solutes and of complexed elements leaving the catchment

multi element chemistry of some amazonian waters and soils abstract the rivers flowing through the amazon basin are both physically and chemically heterogeneous through detailed geochemical analyses variability is shown to be primarily controlled by both substrate lithology in the source region and soil geochemistry in the erosional regime the solute rich waters of the rio solimoes reflect the drainage from the andes mountains and the fertility of the varzea in contrast the solute deficient waters of the rio negro reflect the infertility of the lateritic and podsolitic terrains of the central amazon rivers flowing through the precambrian shield have an intermediate composition such observations suggest that it is possible to classify the chemical composition of amazonian rivers according to the soil types in their catchment regions and vice versa these findings have profound implications for using water chemistry as an indicator of the agricultural and mineral potential of a region results from this study also confirm that precipitation is a significant source of major cations and trace metals to solute deficient river systems such as the rio negro

geochemistry of the amazon 1 precipitation chemistry and the marine contribution to the dissolved load at the time of peak discharge analyses of precipitation and surface water are used to estimate the fluxes of marine cyclic salts through that part of the amazon river system draining past obidos 80 of the basin at the time of peak discharge in june amazon precipitation chemistry can be devided into two principal components marine and terrestrial the marine component determined from analyses of marine rain consists of na k mg ca and cl in approximately sea salt proportions with s doubly enriched the excess sulfur is probably derived from gas phase inputs the terrestrial component makes an important contribution of k ca s and n much of which can be related to biological emissions the emission of reduced sulfur in the marine and terrestrial environment and nitrogen in the terrestrial environment is responsible for a natural acid rain in the amazon region with a ph from 4 7 to 5 7 this is about one tenth the acidity of polluted urban rain the chloride content of lowland rivers which drain regions lacking significant geologic sources of chloride shows a systematic decrease in chloride with increasing distance from the ocean this trend is used to define the cyclic salt background for amazonian surface waters cyclic salts in general make only a minor contribution relative to terrestrial inputs to the chemistry of amazon basin rivers even those draining intensely weathered terrains an estimated 17 6 cl 6 9 na 1 3 mg 3 6 s 0 4 k and 0 1 ca of the dissolved load at obidos during peak discharge is cyclic

the bifrost project gps determined 3 d displacement rates in fennoscandia from 800 days of continuous observations in the swepos network abstract this presentation summarizes results obtained from 800 days of operation of swepos the swedish permanent gps array located in the area of the fennoscandian land uplift swepos is the main measuring device for the bifrost project aiming primarily at determination of crustal motions and changes in global sea level in conjunction with postglacial rebound as a future prospect the project will contribute to determine present day changes in the oceanic water budget as well as strive for a more complete understanding of the viscoelastic structure of crust and mantle we show solutions of site positions obtained from the daily processing of the gps observations we determine their variations in time discerning them from plate or frame orientation and discuss a number of perturbation effects among these the possibility of random walk monument motion is considered the feasibility of single site solutions rather than baseline pairs is demonstrated on the basis of 800 days of operation of the permanent network data analysis is able to confirm the general rebound pattern comparison with both modelling results and evidence from mareograph and precise levelling shows high rates of vertical surface displacement from gps measurements in the centre of the pleistocene glaciation region we discuss the possibility of rate biases due to problems with the terrestrial reference frames

approximate analytic solutions to 3d unconfined groundwater flow within regional 2d models abstract we present methods for finding approximate analytic solutions to three dimensional 3d unconfined steady state groundwater flow near partially penetrating and horizontal wells and for combining those solutions with regional two dimensional 2d models the 3d solutions use distributed singularities analytic elements to enforce boundary conditions on the phreatic surface and seepage faces at vertical wells and to maintain fixed head boundary conditions obtained from the 2d model at the perimeter of the 3d model the approximate 3d solutions are analytic continuous and differentiable everywhere including on the phreatic surface itself while continuity of flow is satisfied exactly in the infinite 3d flow domain water balance errors can occur across the phreatic surface

postglacial faulting in eastern canada nature origin and seismic hazard implications abstract at more than 70 locations in southeastern canada and the adjacent united states tiny bedrock faults displace glacial striations that are about 10 000 years old these reverse faults mostly of small displacement occur in a broad arc from western ontario to newfoundland the faults lie near the margin of the laurentian ice sheet strike generally tangential to it and imply compression nearly normal to the ene directed contemporary regional stress these observations and some age relationships suggest that the faults formed very soon after deglaciation perhaps in the first few thousand years after ice melting in each place and probably represent the release of stresses caused by flexural deformation of the upper crust although the individual offsets are small the faults are believed to be pervasive and individual outcrops reflect amounts of stress relief consistent with stresses implied by the postglacial tilt of nearby lake shorelines

suppression of earthquakes by large continental ice sheets the interior regions of antarctica and greenland are aseismic no earthquake larger than body wave magnitude 4 5 5 0 is known for either except along coastal zones or continental shelves here i advance an explanation for this lack of seismic activity in terms of pressure effects produced by the continental ice sheets that mantle both continents

analytic elements for multiaquifer flow abstract the objective of this paper is to present an analytic element formulation for groundwater flow in multiaquifer systems analytic element equations are presented for wells line sinks and circular infiltration areas each analytic element is a solution to the governing system of differential equations and thus simulates the leakage between aquifers exactly the head discharge and leakage may be computed analytically at any point in the aquifer superposition of these analytic elements allows for the simulation of regional multiaquifer flow a hypothetical example is presented of a system with three aquifers a river network and three pumping wells it is demonstrated that the leakage between aquifers may vary significantly over short distances and that each aquifer has its own water divide

first data on trace metal level and behaviour in two major arctic river estuarine systems ob and yenisey and in the adjacent kara sea russia dissolved and colloidal trace element concentrations cd cu fe ni and pb were determined in the ob and yenisey river estuary systems and in the adjacent kara sea in september 1993 the data show a natural low concentration level of dissolved 0 4 m trace metals cd cu fe ni and pb in the two rivers and in the kara sea as compared to world unpolluted rivers and the central arctic ocean suggesting that the region studied is pristine with respect to trace metals the pathway of trace metals transported from rivers to the ocean seems to be complicated and largely influenced by biogeochemical processes taking place in the estuarine mixing zone colloidal material 104 daltons 0 4 m in addition to its significant contribution to the so called dissolved fraction has been shown to play a fundamental role in determining the behaviour of both conservative and non conservative trace metals during estuarine mixing hence colloids may control to a large extent the fate of dissolved trace metals as well as their net input from the rivers to the kara sea

regional patterns of tectonic stress in europe nearly 1500 stress orientation determinations are now available for europe the data come from earthquake focal mechanisms overcoring measurements well bore breakouts hydraulic fracturing measurements and young fault slip studies and sample the stress field from the surface to seismogenic depths three distinct regional patterns of maximum compressive horizontal stress shmax orientation can be defined from these data a consistent nw to nnw shmax stress orientation in western europe a wnw ese shmax orientation in scandinavia similar to western europe but with a larger variability of shmax orientations and a consistent e w shmax orientation and n s extension in the aegean sea and western anatolia the different stress fields can be attributed to plate driving forces acting on the boundaries of the eurasian plate locally modified by lithospheric properties in different regions on average the orientation of maximum stress in western europe is subparallel to the direction of relative plate motion between africa and europe and is rotated 17 clockwise from the direction of absolute plate motion the uniformly oriented stress field in western europe coincides with thin to medium lithospheric thickness approximately 50 90 km and high heat flow values 80 m w m2 in western europe a predominance of strike slip focal mechanisms implies that the intermediate principal stress is vertical the more irregular horizontal stress orientations in scandinavia coincide with thick continental lithosphere 110 170 km and low heat flow 50 m w m2 the cold thick lithosphere in this region may result in lower mean stresses associated with far field tectonic forces and allow the stress field to be more easily perturbed by local effects such as deglaciation flexure and topography the stress field of the aegean sea and western anatolia is consistent with n s extension in a back arc setting behind the hellenic trench subduction zone the stress field is influenced in places by regional geologic structures e g in the western alps where shmax directions show a slight tendency toward a radial stress pattern not all major geologic structures however appear to affect the shmax orientation e g in the vicinity of the rhine rift system horizontal stress orientations are continuous

trace element geochemistry in the upper amazon drainage basin bolivia abstract the distribution of trace elements sr mo ba rb u mn ni cu zn and cd was investigated in surface waters and associated particulates in two upper amazonian basins mamore and beni dissolved sr ba mo rb u and to a lesser extent zn and cd correlate with major ions and appear to be predominantly derived from soluble rocks carbonates evaporites or sulfides essentially contained in shales these elements are conservative in waters except in highly alkaline or sulfate rich waters where calcite and barite can precipitate the concentrations of transition element are generally not correlated with major ion chemistry their behaviour can be largely explained by equilibrium reactions in solution and solid liquid exchanges additionally the distribution of mn and cu reflects also the lithological differences between the mamore and beni basins the occurrence of mineralisation in the beni basin explains the high zn cd as well as the concentrations of cu in some rivers of the beni basin the higher content of mn in the mamore basin may reflects the predominance of carbonate rocks the fractionation of trace elements in spm has been attributed to the sorting of feldspars during transport in water and to the mixing between clay minerals and quartz these minerals refractory to weathering and introduced in water rivers by mechanical erosion have not contributed to the dissolved load