on the mechanism of wavelength selection of self organized shoreline sand waves sandy shorelines exposed to very oblique wave incidence can be unstable and develop self organized shoreline sand waves different types of models predict the formation of these sand waves with an initially dominant alongshore wavelength in the range 1 10 km which is quite common in nature here we investigate the physical reasons for such wavelength selection with the use of a linear stability model the existence of a minimum wavelength for sand wave growth is explained by an interplay of three physical effects a largest relative to the local shoreline wave angle at the downdrift flank of the sand wave b wave energy concentration at the updrift flank due to less refractive energy dispersion and c wave energy concentration slightly downdrift of the crest due to refractive focusing for small wavelengths effects a and c dominate and cause decay while for larger wavelengths effect b becomes dominant and causes growth however the alongshore gradients in sediment transport decrease for increasing wavelength making the growth rate diminish there is therefore a growth rate maximum giving a dominant wavelength lm in contrast with previous studies we show that lm scales with 0 0 is the wavelength of the offshore waves and is the mean shoreface slope from shore to the wave base an estimate of the order of magnitude of the distance waves travel to undergo appreciable transformation our model investigations show that the proportionality constant between lm and 0 is typically in the range 0 1 0 4 depending mainly on the wave incidence angle

high angle wave instability and emergent shoreline shapes 2 wave climate analysis and comparisons to nature 1 recent research has revealed that the plan view evolution of a coast due to gradients in alongshore sediment transport is highly dependant upon the angles at which waves approach the shore giving rise to an instability in shoreline shape that can generate different types of naturally occurring coastal landforms including capes flying spits and alongshore sand waves this instability merely requires that alongshore sediment flux is maximized for a given deepwater wave angle a maximum that occurs between 35 and 50 for several common alongshore sediment transport formulae here we introduce metrics that sum over records of wave data to quantify the long term stability of wave climates and to investigate how wave climates change along a coast for long point a flying spit on the north shore of lake erie canada wave climate metrics suggest that unstable waves have shaped the spit and furthermore that smaller scale alongshore sand waves occur along the spit at the same locations where the wave climate becomes unstable a shoreline aligned along the trend of the carolina capes united states would be dominated by high angle waves numerical simulations driven by a comparable wave climate develop a similarly shaped cuspate coast local wave climates along these simulated capes and the carolina capes show similar trends shoreline reorientation and shadowing from neighboring capes causes most of the coast to experience locally stable wave climates despite regional instability

timing kinematics and cause of aegean extension a scenario based on a comparison with simple analogue experiments abstract since the early 1970s most geodynamic models proposed for the eastern mediterranean consider that the initiation of extension in the aegean during the late middle miocene or later was a direct consequence of the westward extrusion of anatolia away from the arabia eurasia collision front in the late 1990s a few models have taken into account the increasing evidence for an earlier initiation of aegean extension arising mostly from the analysis of deformation within the various alpine metamorphic complexes of the area based largely on our own investigations we first present a review of the data that reliably constrain the minimum age for the initiation of extension in these complexes it shows that regional scale extension with a pattern of stretching orientations similar to that of the pliocene pleistocene was already strongly active in the aegean before the onset of arabian indentation into eurasia lower miocene vs middle or upper miocene this implies that the initiation of aegean extension did not result from the lateral extrusion of anatolia instead extension may have started owing to a process of gravity spreading of the continental lithosphere that had previously been thickened during alpine collision the main arguments favouring this interpretation are presented and a preliminary scenario is proposed for the neogene evolution of the eastern mediterranean in which lateral extrusion of anatolia occurred lately during southward spreading of the aegean lithosphere in order to test this hypothesis further physical experiments simulating the horizontal spreading of a continental lithosphere toward a free boundary have been carried out the analysis of various elements of the deformation field displacements strain rotations fault pattern and kinematics both in the experiments and in the aegean domain reveals an excellent agreement between the two not only do early stages of aegean extension appear to fit the gravity spreading hypothesis but so does the recent to present internal deformation of the aegean transverse e w active shortening observed in the northern aegean is commonly taken as one of the most striking pieces of evidence that aegean extension results from the lateral extrusion of anatolia the experiments indicate that such transverse shortening may equally develop as a result of pure gravity spreading associated with a pattern of faults and rotations that compares well with that of the northern aegean pure dextral shearing along some strands of the north aegean trough fault system and the related development of an asymmetric pattern of faults in the northern aegean are eventually the only features that evidently arise from the extrusion of anatolia since less than 3 ma finally we argue that during the early stages of aegean extension since at least 21 ma and until ca 11 ma the distribution of extensional strain on a regional scale has been controlled by the distribution of earlier thickening post thickening thermal weakening through partial melting of deep levels of the crust probably accounts for the localization of extensional strain within the areas of thick crust restoring the aegean in its most likely configuration at the onset of bulk crustal extension suggests that 1 the extensional strain rate remained roughly constant or has eventually decreased since the onset of aegean extension and 2 the amounts of extension before and after 16 ma have been roughly equal

formation mechanisms for self organized kilometer scale shoreline sand waves the feedbacks between morphology and waves through sediment transport are investigated as a source of kilometer scale shoreline sand waves in particular the observed sand waves along srd holmslands tange denmark are examined we use a linear stability model based on the one line approximation linking the bathymetry to the perturbed shoreline previous models that consider the link by shifting the equilibrium profile and neglecting the curvature of the depth contours predict a positive feedback only if the offshore wave incidence angle c is above a threshold c 42 considering curvilinear depth contours and using a linearly decaying perturbation in bed level we find that c can vary over the range 0 90 depending on the background bathymetric profile and the depth of closure dc associated to the perturbed wave refraction there are two sources of instability the alongshore gradients in wave angle wave angle mechanism and the alongshore gradients in wave energy induced by wave crest stretching wave energy mechanism the latter are usually destabilizing but the former are destabilizing only for large enough dc steep foreshores and gently sloping shorefaces the critical angle comes out from the competition between both mechanisms but when both are destabilizing c 0 in contrast with earlier studies the model predicts instability for the holmslands tange coast so that the observed sand waves could have emerged from such instability the key point is considering a larger dc that is reasonably supported by both observations and wave climate which brings the wave angle mechanism near the destabilizing threshold

formation of coastline features by large scale instabilities induced by high angle waves along shore sediment transport that is driven by waves is generally assumed to smooth a coastline this assumption is valid for small angles between the wave crest lines and the shore as has been demonstrated in shoreline models but when the angle between the waves and the shoreline is sufficiently large small perturbations to a straight shoreline will grow here we use a numerical model to investigate the implications of this instability mechanism for large scale morphology over long timescales our simulations show growth of coastline perturbations that interact with each other to produce large scale features that resemble various kinds of natural landforms including the capes and cuspate forelands observed along the carolina coast of southeastern north america wind and wave data from this area support our hypothesis that such an instability mechanism could be responsible for the formation of shoreline features at spatial scales up to hundreds of kilometres and temporal scales up to millennia

global positioning system measurements of present day crustal movements in the arabia africa eurasia plate collision zone we present and interpret global positioning system gps measurements of crustal motions for the period 1988 1994 at 54 sites extending east west from the caucasus mountains of southern russia georgia and armenia to the aegean coast of turkey and north south from the southern edge of the eurasian plate pontus block to the northern edge of the arabian platform viewed from a eurasia fixed reference frame sites on the northern arabian platform move n38 13 w at 20 3 mm yr roughly consistent with the velocity implied by nuvel 1a circuit closure n23 7 w at 24 2 mm yr the motion of arabia appears to be transferred directly to the region of turkey north of the suture however eastern turkey is characterized by distributed deformation while central western turkey is characterized by coherent plate motion involving westward displacement and counterclockwise rotation of the anatolian plate internal deformation within the central part of the anatolian plate is less than 2 mm yr the anatolian plate is decoupled from eurasia along the right lateral strike slip north anatolian fault naf this different response in eastern and western turkey to the collision of arabia may result from the different boundary conditions the hellenic arc forming a free boundary to the west and the asian continent and oceanic lithosphere of the black and caspian seas forming a resistant boundary to the north and east we derive a best fitting euler vector for anatolia eurasia motion of 29 2 0 8 n 32 9 0 4 1 3 0 1 m y the mapped surface trace of the naf corresponds well to a small circle about this pole the new euler vector implies an upper bound for naf slip rate of 30 2 mm yr i e assuming all relative motion is accommodated along the naf using the nuvel 1a euler vector for arabia eurasia and the gps euler vector for anatolia eurasia we determine an arabia anatolia euler vector of 31 2 n 45 2 e 0 9 0 1 m y and an upper bound on the east anatolian fault slip rate of 15 3 mm yr the aegean trough region of western turkey deviates significantly from coherent plate rotation in addition to rotating with anatolia this region shows roughly n s extension at a rate of 14 5 mm yr taken together with satellite laser ranging results along the hellenic arc the contemporary pattern of deformation indicates increasing motions toward the arc suggesting that the westward displacement and counterclockwise rotation of anatolia is driven both by pushing from the arabian plate and by pulling or basal drag associated with the foundering african plate along the hellenic subduction zone

large scale dynamics of sandy coastlines diffusivity and instability 1 the dynamics of small amplitude perturbations of an otherwise rectilinear coastline due to the wave driven alongshore sediment transport is examined at large time and length scales years and kilometers a linear stability analysis is performed by using an extended one line shoreline model with two main improvements 1 the curvature of the coastline features is accounted for and 2 the coastline features are assumed to extend offshore as a bathymetric perturbation up to a finite distance for high incidence angles instability is found in accordance with ashton et al 2001 however it is seen that instability is inhibited by high waves with long periods and gently sloping shorefaces so that in this case the coastline may be stable for any angle similarly there is no instability if the bathymetric perturbation is confined very close to the coast it is found that the traditional linearized one line model larson et al 1987 tends to overpredict the coastline diffusivity the overprediction is small for the conditions leading to a stable coastline and for moderate incidence angles but can be very dramatic for the conditions favoring instability an interesting finding is that high angle waves instability has a dominant wavelength at the linear regime which is in the order of 4 15 km one to two orders of magnitude larger than the length scale of surf zone rhythmic features intriguingly this is roughly the same range of the wavelength of some observed shoreline sand waves and in particular those observed along the dutch coast a model application to this coast is presented

microseimicity and strain pattern in northwestern greece during a 7 week microearthquake experiment conducted in epirus akarnania and the ionian islands of western greece we located approximately 600 earthquakes with magnitudes between 2 and 4 2 no event was deeper than 40 km the seismicity cannot be clearly associated with any single fault except the lixourion right lateral fault located west of the ionian islands focal mechanisms of about 100 earthquakes show for a narrow band of earthquakes located along the coast ene wsw shortening consistent with the surface tectonics farther east focal mechanisms show nnw sse extension beneath the foothills of the pindus mountains which is unrelated to surface faulting but is consistent with the presently subsiding basins this strain pattern is seen far north and south of the lixourion fault and is similar to the one observed in the peloponnese it suggests that a large scale mechanism is responsible for the recent geodynamics of both the northwestern and southwestern aegean

the origin of solutes within the groundwaters of a high andean aquifer abstract this paper investigates the origin of solutes within the groundwaters of the monturaqui negrillar tilopozo mnt aquifer system within the high andes of the atacama desert that discharges into the salar de atacama key questions include the relative significance of volcanic hydrothermal processes and evaporitic brine recycling over solute supply as well as the pathways of solute ingress to the mnt aquifer system groundwaters were analysed for elemental major minor and trace and isotopic 18o 2h 13c dic 34s so4 87sr 86sr constituents to which various hydrochemical and multivariate statistical methods have been applied groundwaters are all classified as thermal and show increasing temperatures 27 35 c and concentrations of hco3 4 4 10 4 mmol l 1 dissolved inorganic carbon dic with increasing proximity to volcano socompa resulting from an increasing mass flux of steam and magmatic co2 pco2 0 016 to 0 10 atm 13c co2 9 3 to 3 6 v pdb boiled off a deep hydrothermal reservoir superimposed upon this gradational and relatively smooth spatial increase in heat and mass flow is a sharp structurally controlled increase in tds 826 3632 mg l 1 and a concomitant change in 34s so4 0 79 to 4 9 v cdt and 87sr 86sr values 0 707375 0 706859 associated with the inflow of evaporitic solutes evaporitic inputs are chemically and isotopically distinct from localised secondary hydrothermally derived solutes with major minor and trace element data suggesting an origin within a highly oxidising alkaline evaporitic lake receiving dilute inflows enriched in volcanic fumarolic sulfur mineralisation probably from volcanoes socompa salin or pular that delimit the eastern topographic extent of the aquifer system the conceptual model presented in this paper proposes that basal leakage of evaporitic brines from active salar s within the high altiplano volcanic arc are actively entrained by sub regional groundwater flow and conveyed to the mnt aquifer system where they mix with solutes derived from localised secondary hydrothermal gas water rock interaction this work provides detail on the origin and processes controlling the solute composition of groundwater inflows to the salar de atacama within the volcanically active and hyperarid atacama desert and may be of significance to conceptual models of evaporitic brine evolution recycling of evaporitic brines and hydrothermalism in arid regions

sand waves along the dutch coast sand waves defined as longshore wave like movements of the shoreline measured in a horizontal plane are described along several stretches of the shoreline of the netherlands they have a celerity in the order of 50 200 m yr a period of 50 150 years and an amplitude of 30 500 m they are found along the whole dutch shoreline analysis of sand waves shows that the assumed effect of groins might be very small along this shoreline there are indications that groins did not have any long term effect on coastal regression

a recharge model for high altitude arid andean aquifers evidence for groundwater recharge in arid zones is mounting despite early ideas that recharge was unlikely where evaporation greatly exceeded precipitation the mechanisms and magnitude of groundwater recharge in the andes and atacama desert are not well known but the subject of current research diffuse recharge is expected to be limited to high altitude areas with coarse grained soils devoid of vegetation a recharge model for this environment is developed based on a simple soil moisture budgeting technique and the calculation of actual evaporation based on empirical studies the model is run with data for the linzor basins over 4000 m elevation at 22 2 s on the west slope of the andes it is checked against independent estimates based on the chloride mass balance cmb method and flood events measured downstream in the rio salado and found to provide robust and reliable results the results indicate that irregular and volumetrically limited amounts of diffuse recharge occur at high elevations in half of all years with a tendency to cluster during la nina episodes for the linzor basins mean annual recharge is found to be equivalent to 28 mm a 1 although no recharge occurs in years with precipitation less than 120 mm and increases proportionately with annual rainfall amounts above this limit copyright 2009 john wiley sons ltd

dunefoot dynamics along the dutch coast the dynamics of the dunefoot along a 160 km portion of the dutch coast has been investigated based on a data set of annual surveys dating back to as early as 1850 the linearly detrended or residual dunefoot positions comprise an alongshore uniform and an alongshore non uniform component the former is expressed as 10 to 15 m of landward retreat along extensive 10 km stretches of coast during years with severe storm surges and as up to 5 m of seaward advance during years without significant storm activity the latter alongshore non uniform component is organized in sandwave like patterns which may have a longevity of decades to up to the duration of the entire data set 150 years their wavelengths vary along the coast from 3 5 to 10 km migration rates are 0 200 m a 1 dunefoot sandwaves are shown to be the shoreward extensions of similar sandwave patterns in the beach position the non uniform dunefoot behaviour constitutes at least 80 per cent of the total residual dunefoot dynamics implying that along the dutch coast residual dunefoot variability is controlled by temporal and spatial variability in beach characteristics and not by storm induced uniform erosion various potential mechanisms causing beach sandwaves are discussed copyright 2002 john wiley sons ltd

coastline sand waves on a low energy beach at el puntal spit spain abstract coastline sand waves have been observed at el puntal spit located on the north coast of spain the spit has been monitored by an argus video system since 2003 and the formation and destruction of sand waves has been observed coastline data from the video images are analyzed by means of principal components analysis obtaining a mean sand wave length of 125 150 m and a maximum amplitude of 15 m it is also observed that sand waves reach their maximum amplitude at about 15 days no propagation of these sand waves is noticed during the approximately two month long events analyzed sand wave formation and evolution are examined in relation with the prevailing local wave conditions during that period incident waves at the west end of the spit approach from the east northeast with a very high angle with respect to the shoreline field observations suggest that sand waves may result from an instability in alongshore sediment transport caused by moderate energy waves with a high angle incidence

high angle wave instability and emergent shoreline shapes 1 modeling of sand waves flying spits and capes 1 contrary to traditional findings the deepwater angle of wave approach strongly affects plan view coastal evolution giving rise to an antidiffusional high wave angle instability for sufficiently oblique deepwater waves with angles between wave crests and the shoreline trend larger than the value that maximizes alongshore sediment transport 45 a one contour line numerical model shows that a predominance of high angle waves can cause a shoreline to self organize into regular quasiperiodic shapes similar to those found along many natural coasts at scales ranging from kilometers to hundreds of kilometers the numerical model has been updated from a previous version to include a formulation for the widening of an overly thin barrier by the process of barrier overwash which is assumed to maintain a minimum barrier width systematic analysis shows that the wave climate determines the form of coastal response for nearly symmetric wave climates small net alongshore sediment transport cuspate coasts develop that exhibit increasing relative cross shore amplitude and pointier tips as the proportion of high angle waves is increased for asymmetrical wave climates shoreline features migrate in the downdrift direction either as subtle alongshore sand waves or as offshore extending flying spits depending on the proportion of high angle waves numerical analyses further show that the rate that the alongshore scale of model features increases through merging follows a diffusional temporal scale over several orders of magnitude a rate that is insensitive to the proportion of high angle waves the proportion of high angle waves determines the offshore versus alongshore aspect ratio of self organized shoreline undulations

migration and sedimentology of longshore sandwaves long point lake erie canada this paper describes the formation migration and sedimentology of sandwaves along the distal end of long point a 40 km long spit in lake erie some seven to nine sandwaves occur in a zone over the last 14 km of the spit they are characteristically 50 100 m wide at the downdrift end range in length from 350 m to 1500 m and migrate alongshore at rates that are typically 100 300 m year 1 measurements over a 7 year period show two forms of alongshore sandwave migration 1 a migratory jump and 2 downdrift accretion the migratory jump is commonly 200 500 m year 1 and results from the onshore migration and welding of an inner nearshore bar to the downdrift end of the sandwave this in turn leads to emergence of the bar over a distance of several hundred metres downdrift of the sandwave and isolation of the trough landward of the bar infilling of the trough abstracts large volumes of sediment from the local sediment transport system and may affect movement of the sandwave in the following year or movement of the next sandwave downdrift downdrift accretion commonly results in migration of 50 150 m year 1 and results from the refraction of waves around the distal end of the sandwave and episodic accretion of small swash bars this mechanism occurs less frequently and appears to reflect a local condition of lower sediment abundance often triggered by a large migratory jump in the previous year the process of bar emergence and infilling produces a distinct suite of sedimentary structures associated with the infilling of the landward trough and building of the sandwave berm the initial shoreline perturbation that generates the sandwave results from onshore migration and welding of inner nearshore bars and the development and growth of the sandwaves is promoted by refraction of highly oblique waves

the tertiary geodynamical evolution of the aegean arc a paleomagnetic reconstruction abstract the paleomagnetic results obtained in the last 5 6 years from tertiary formations in the aegean domain indicate that the lower miocene arc was almost rectilinear with an e w trend and that its curvature has been acquired tectonically in two major phases during the middle miocene a first phase of deformation is characterized by rotations occurring at the two terminations of the arc clockwise in the west epirus anticlockwise in the east southeastern anatolia a second phase of rotation occurring in the last 5 ma about a pole situated in the southern adriatic sea has affected only the northwestern part the data also indicate that the antalya basin has not been involved in the geodynamical evolution of the arc so that the bey daglari represent its easternmost unit a more complex rotational pattern is observed in the internal zones the large rotations measured in evia 48 and skyros 26 probably occurred in the last 5 ma and result from rotation of fault bounded blocks in a shear zone connecting the north aegean trough to the external arc in the izmir region in the karaburun peninsula of western anatolia and in the island of lesbos significant counterclockwise clockwise or null rotations of coherent blocks have taken place during the neotectonic extensional regime furthermore the values of the inclination obtained from both sedimentary and volcanic oligo miocene formations are systematically shallower than expected on the basis of a geocentered dipole field this suggests that the entire studied area has undergone a northward drift of over 1000 km since the middle miocene

reproducing the velocity and stress fields in the aegean region recent satellite geodetic measurements help to clearly define the velocity field in the aegean anatolian area the velocity field can be broadly characterized by anticlockwise rotation of this region relative to eurasia around a pole located at lat 32 73 long 32 03 north of the egyptian shoreline studies of the fault kinematics in the region also provide information on the time evolution of the stress field in this work we model deformation in the aegean anatolian region to better understand the tectonic origin of the observed stress and velocity fields we found that the observed deformation pattern can be well reproduced by imposing simple boundary conditions including 1 northward displacement of the arabian plate 2 locking of eastward motion in northwestern greece and 3 suction force at the hellenic trench the observed variation in the stress field occurred at 0 9 ma can be partially explained by a change in the activity of the north anatolian fault

shoreline instability under low angle wave incidence 1 the growth of megacusps as shoreline instabilities is investigated by examining the coupling between wave transformation in the shoaling zone longshore transport in the surf zone cross shore transport and morphological evolution this coupling is known to drive a potential positive feedback in case of very oblique wave incidence leading to an unstable shoreline and the consequent formation of shoreline sand waves here using a linear stability model based on the one line concept we demonstrate that such instabilities can also develop in cases of low angle or shore normal incidence under certain conditions small enough wave height and or large enough beach slope the wavelength and growth timescales are much smaller than those of high angle wave instabilities and are nearly in the range of those of surf zone rhythmic bars o 102 103 m and o 1 10 days the feedback mechanism is based on 1 wave refraction by a shoal defined as a cross shore extension of the shoreline perturbation leading to wave convergence shoreward of it 2 longshore sediment flux convergence between the shoal and the shoreline resulting in megacusp formation and 3 cross shore sediment flux from the surf to the shoaling zone feeding the shoal even though the present model is based on a crude representation of nearshore dynamics a comparison of model results with existing depth averaged two dimensional model output and laboratory experiments suggests that the instability mechanism is plausible additional work is required to fully assess whether and under which conditions this mechanism exists in nature

the climate of the altiplano observed current conditions and mechanisms of past changes abstract the large scale controls on the climate of the south american altiplano are investigated using local observations reanalysis data and general circulation model experiments the objective is to gain understanding of causes of climate variability and climate change by relating mechanisms that operate on timescales ranging from the intraseasonal to the glacial interglacial our results suggest that on all timescales the climatic conditions on the altiplano are closely related to the upper air circulation with an easterly zonal flow aloft favoring wet conditions and westerly flow causing dry conditions different factors influence the upper air circulation on the different timescales intraseasonal variability is a reflection of the position and intensity of the bolivian high which is modulated by rossby waves emanating from the midlatitude south pacific the annual cycle of dry winter and wet summer conditions is caused by the seasonal expansion of the equatorial easterlies in the upper troposphere rather than direct insolation forcing over the altiplano or moisture changes in the source area interannual variability is primarily related to changes in the mean zonal flow over the altiplano reflecting changes in meridional baroclinicity between tropical and subtropical latitudes which in turn is a response to sea surface temperature changes in the tropical pacific orbitally forced changes in the land sea contrast drive continental scale circulation changes which significantly alter the zonal flow over the altiplano on glacial interglacial timescales the contrast in heating between northern and southern hemispheres during the glacial leads to upper air easterly anomalies throughout the tropics on modern timescales the marked submonthly seasonal and interannual changes of moisture over the altiplano cannot be accounted for by moisture changes in the humid tropical lowlands however the model experiments suggest that cooler conditions during a glacial reduce moisture availability from the tropical lowlands which counteracts the effect of the upper level circulation resulting in little overall change in precipitation this observational and modeling analysis provides a physical framework for relating the mechanisms of both internal and forced climate change on the altiplano on a wide range of timescales

temporal variation in the stress field of the aegean region we use a forward numerical model to analyse the intra plate stress field in an area of active extension of continental lithosphere the aegean region recent tomographic images of the hellenic subduction zone offer the unique opportunity to address the relation between the evolving aegean stress field and temporal variations in the subduction process to this extent we apply our model to both the present day and the late pliocene situation regarding the current situation it is found that subduction related forces largely explain the observed pattern of tension results obtained for the pliocene indicate that detachment of the slab subducted below western greece may have controlled the observed temporal variation in the pattern of tension

rapid recharge of fresh water to the halite hosted brine aquifer of salar de atacama chile we document analyze and interpret direct and rapid infiltration of precipitation to the southern margin of the salar de atacama halite hosted brine aquifer during 2 intense precipitation events in 2012 2013 we present physical geochemical and stable and radioactive isotope data to detail this influx of water the two events differ distinctly in the mechanisms of recharge the 2012 event did not produce direct precipitation onto the salar surface while the 2013 event did both events are recorded by abrupt changes in head in observation wells along the halite aquifer margin spatially distributed water levels rose by over 30 cm during the larger 2013 event consistent with remotely sensed observations of surface water extent the lithium concentration and stable isotopic composition of water indicate dilution of brine and dissolution of salt with fresh water tritium measurements of precipitation surface water and groundwater all indicate modern influx of water to the halite aquifer along the southern margin we extend these observations by examining the response of the halite aquifer as a whole to precipitation events during the period of 2000 2010 this study suggests that local recharge to the aquifer during sporadic precipitation onto the halite nucleus is an important component of the modern water budget in this hyper arid environment the rapid dissolution and salinization along the southern margin of the salar halite nucleus is aided by such precipitation events contributing a modern fresh water component to the water budget of the economically valuable lithium rich brine this article is protected by copyright all rights reserved

physical properties and state of the crust and upper mantle of the eastern mediterranean sea deduced from geophysical data abstract by evaluating the geophysical information available for the eastern mediterranean sea ems a crustal thickness map and some conclusions as to the nature of the crustal type were drawn it was found that the ionian abyssal plain is floored by an oceanic type of crust which is 14 km thick and covered by sediments of the order of 8 km thick the herodotus abyssal plain in the levantine sea is floored by a crust 22 km thick and covered by sediments ranging between 10 and 15 km thick the eastern mediterranean rise extending more or less continuously from the apulian plateau to rhodes and the south of the antalya basin is of a thickness ranging between 28 and 34 km the thickness of its sedimentary cover is of the order of 10 km the borders of the eastern mediterranean sea are built up of thick continental crust for example the hellenides of western greece range between 40 and 44 km thick and western turkey has a similar crustal thickness the crust of sicily also exceeds 40 km whereas the southern and eastern borders of the ems are approximately 30 32 km thick tectonically the northern border of the ems is built up of active continental margins defined by the calabrian hellenic and cyprus antalya arcs whereas the southern border represents a passive continental margin controlled mainly by subsidence and stretching to the east the dead sea megashear limits the area the deep basins of the eastern mediterranean sea are tectonically controlled by subsidence and partial stretching the mediterranean ridge or rise is still an area of dispute regarded by some authors as a subsiding continental fragment and separated from the hellenic arc by the hellenic trench whereas others consider it to be a zone of crustal shortening thickened mainly by thrusting both the western and southwestern borders of the mediterranean rise and the hellenides are controlled by compressional processes similar to those deforming the calabrian arc the stravo and pliny trenches to the east southeast border of the hellenic arc are partly affected by strike slip movements various plate tectonic models of the area have been proposed by several authors though the complexity of the deformation hardly permits reliable reconstructions the lack of reliable paleomagnetic information and the absence of linear magnetic anomalies do not favour the application of plate tectonic concepts vertical processes due to the uprising of lithothermal systems below the hellenic and calabrian arcs may also be regarded as the driving force controlling the present day deformation

experiments on shortening of a 4 layer model of the continental lithosphere davy ph and cobbold p r 1991 experiments on shortening of a 4layer model of the continental lithosphere in p r cobbold editor experimental and numerical modelling of continental deformation tecronophysics 188 l 25 we present an experimental method for modelhng lithospheric deformation the method is based on a simplified profile of lithosphere rheology where only four layers are considered brittle crust ductile crust brittle mantle and ductile mantle the strengths of the four layers calculated from laboratory determined flow laws depend strongly on geothenns and slightly on strain rates and deformation regimes the rheological profiles of the lithosphere have been recreated in experimental models built with analog materials sand silicone putty and golden syrup which flow under their own weight during lithospheric shortening the style of deformation depends on the relative strengths of the four layers especially those in the mantle of special importance is the existence or non existence of a brittle mantle the initial stages of compression often produce flexures or buckles without local isostatic compensation buckling exerts a strong control on the localisation of thrust faults in later stages the thrusts tend to form at the inflexion points of buckles the style of crustal thickening depends on the relative thicknesses and resistances of the lithospheric layers in 2 layer lithospheric models without resistant mantle shortening was concentrated upon a small number of thrusts widely spaced in 3 layer models shortening was concentrated into a large number of reverse faults more closely spaced and more steeply dipping than before in clayer models a single thrust formed in the brittle mantle motion on this thrust dragged the crustal layers down forming an asymmetric crustal root with steep imbricate slices

deflection gravity anomalies and tectonics of doubly subducted continental lithosphere adriatic and ionian seas three profiles across the southern adriatic and northern ionian seas span an intermediate foreland area that is or has recently been subducted both westward under the apennine calabrian thrust belt and eastward under the hellenide belt gravity and deflection data from the base of the pliocene along the three profiles are qualitatively similar to those predicted for a thin elastic sheet subject to end loads at both plate ends more detailed analysis of the profiles shows very good agreement between observations and predictions if the intermediate foreland lithosphere is treated as a thin elastic sheet with an effective elastic thickness between about 15 and 20 km equivalent to a flexural rigidity between 2 1022 and 6 1022 nm these results coupled with seismicity data suggest that active convergence within the hellenides extends as far north as southwestern yugoslavia analysis of the northernmost profile across the southern adriatic sea shows a well constrained elastic plate thickness of 14 km and an initial water depth prior to loading of about 1 km the distance between the two subduction systems on this profile is estimated at about 275 km analysis of the two more southerly profiles yields a minimum effective elastic plate thickness of about 15 km but no maximum value could be determined the initial water depths for these two profiles are well constrained at 1 3 and 1 6 km prior to loading and the distance between the two subduction systems is estimated at about 175 km on both profiles along the northwest trend of the two opposing subduction systems the change in distance between the two systems occurs abruptly and the hellenic subduction system appears to be segmented into a series of northwest trending roughly linear subduction segments the calculated deflection profiles also show pronounced asymmetry on the northernmost profile and an opposite sense of asymmety on the southernmost profile

groundwater recharge through an alluvial fan in the atacama desert northern chile mechanisms magnitudes and causes the chacarilla fan in the atacama desert is one of several formed in the late miocene at the foot of the pre andean cordillera overlying the large complex pampa tamarugal aquifer contained in the continental clastic sediments of the fore arc basin the pampa tamarugal aquifer is a strategic source of water for northern chile but there is continuing doubt over the resource magnitude and recharge during january 2000 a 1 in 4 year storm in the andes delivered a 34 million m3 flash flood to the fan apex where c 70 percolated to the underlying aquifers groundwater recharge through the fan is calculated to be a minimum of 200 l s or 6 of the long term catchment rainfall these figures are supported by hydrochemical data that suggest that recharge may be 9 of long term rainfall isotopic data suggest groundwater less than 50 years old is transmitted westward through the permeable sheetflood sediments of the fan overlying the main aquifer analysis of this and other events shows that the hydrological system is non linear with positive feedback the magnitude of groundwater recharge is dependent on climatic variations antecedent soil moisture storage and changes in channel characteristics long term declines in groundwater level may partly result from climatic fluctuations and the causes of such fluctuations are discussed copyright 2002 john wiley sons ltd

variability of shore and shoreline evolution shore and shoreline evolution both due to natural and human induced causes or factors can be variable over a wide range of different temporal and or spatial scales our capability to understand and especially predict this variability is still limited this can lead to misinterpretation of coastal change information which hampers informed decision making and the subsequent design and implementation of soft engineering interventions collecting and describing example observations of shore and shoreline variability is one way to support and improve such human intervention this paper describes causes and factors for the variability and the resulting possible evolutions of wave dominated shores and shorelines which are illustrated by a number of case studies the new element of this work is that the variability is described in terms of a range of different time and space scales which helps to structure such analysis however it is difficult to generalise the results for arbitrary situations especially on decadal time scales scientific and engineering improvements require more quantitative insight into the physical mechanisms behind the free and forced shore behaviour responsible for the variability

shoreline evolution of the holland coast on a decadal scale the decadal evolution of the dunefoot position along 120 km of the holland coast is analysed firstly a new definition of dunefoot is introduced based on hydrodynamic and morphologic considerations which is not affected by local and instantaneous processes occurring immediately before the bathymetric survey the dunefoot evolution over decadal scales indicates the existence of spatial and temporal oscillations in the shoreline position with magnitudes of 2 3 km length and a periodicity of 4 15 years two main controlling factors of this behaviour are identified 1 influence of sub aqueous bar systems and 2 changes in the storm wave conditions reaching the coast although the precise controlling processes of the relation between the dunefoot and the subaqueous profile still remain unclarified we introduce the concept that the development of a morphological bar cycle requires a fixed amount of time integrated forcing that is proportional to the cumulative effect of storm waves beach mobility along the holland coast on decadal scales 10 20 m is similar or lower than mobility introduced by storms or by seasonal cycles however it is important to consider these changes for the possible implications on the local vulnerability of the coast to extreme events copyright 1999 john wiley sons ltd

the tectonic development of the hellenic arc and the sea of crete a synthesis abstract we use field analyses together with interpretation of aerial photographs orbital imagery and sea beam data to define more accurately the geometry of fault systems in the hellenic arc the tectonics of the area are dominated by extensional processes related to normal faulting we then use sea beam data previous oceanographic studies and extrapolation of field analyses on surrounding islands to describe the fault pattern of the cretan sea basin which is found consistent with the land fault pattern the mechanisms of the late neogene and quaternary deformation of the central and southern aegean region are analysed in terms of stress trajectories as revealed by field studies of fault populations we then examine the subsidence of the sea of crete in terms of a model of uniform stretching of the lithosphere the opening of the sea of crete was cylindrical and did not result in bending of crete this leads us to modify the southern portion of an earlier kinematic reconstruction of aegea in agreement with recent paleomagnetic results the implications of the opening of the sea of crete on the tectonic evolution of the straits to the west and east of crete are discussed finally the uplift of the outer arc is explained by underplating due to subduction

continental collision gravity spreading and kinematics of aegea and anatolia we have carried out experiments using a layered medium of sand and silicone to investigate the lateral extrusion of a material which spreads over its own weight while being compressed by the advance of a rigid indenter boundary conditions in the box mimic those prevailing in the anatolian aegean system both shortening in front of the rigid piston which models the northward motion of arabia and extension resulting from the gravity spreading of the sand silicone layer are necessary to initiate the lateral extrusion strike slip faults accommodate the lateral escape and link the normal faults accompanying gravity spreading with the thrust faults in front of the rigid indenter strike slip faults begin to accommodate extrusion at a late stage in the experiments after the normal and thrust faults have developed experiments also show that the initial geometry of the boundary of the spreading layer may result in the formation of two arcs behind which material extends in a manner analogous to the hellenic and cypriot arcs without invoking a rheological change at the junction of the two arcs the experiments also suggest that southward motion of the eastern part of the spreading region is compensated by the northward advance of the piston which is a possible explanation for the slower movement of the cypriot arc compared to the aegean arc

hydrogeochemical fluxes and processes contributing to the formation of lithium enriched brines in a hyper arid continental basin abstract the accumulation of solutes delivered via shallow groundwater and surface water in arid to hyper arid closed basins and the complex hydrogeochemical processes associated with their transport are key to deciphering mechanisms responsible for the formation of brines and salts in these environments a rigorous investigation of the hydrogeochemical fluxes and the formation of the li enriched brine in the hyper arid basin of the salar de atacama chile is presented water fluxes within the salar de atacama basin range from 0 003 m3 s to 1 50 m3 s with a poor correlation between discharge and drainage basin area the inflowing waters have major elemental and li concentrations that are within the same order of magnitude over a period of several decades the element fluxes indicate for example that 58 of the li in the halite nucleus and brines is derived from the south and southeast parts of the basin the average 18ovsmow and dvsmow of inflow waters indicate that there are varied sources of recharge corresponding to the defined sub watershed regions the average water flux weighted 87sr 86sr of inflow waters allows further definition of where in the regional watershed the solutes are derived the predicted water flux weighted 87sr 86sr of the brines 0 70813 compared to the measured average 87sr 86sr 0 70801 indicates that there may be unaccounted sources of water and solutes to the basin brines elemental accumulation time scales for the volume of halite and brine in the nucleus balance on time frames of 0 5 ma mg 1 0 ma ca 1 9 ma li and 2 2 ma k as compared to 47 ma na and 53 ma cl further evidence that na and cl require additional sources not accounted for in the modern inflows to the topographic watershed dissolved noble gas concentrations of marginal and nucleus brines specify that the brines formed in an atmospheric equilibrated state and have since been isolated below the salt crust a process based model is presented to explain the extremely high concentrations of li in brines which incorporates the 7li isotope signatures of waters in the basin to further decipher on a first order the contributions of processes such as low temperature weathering and secondary phase formation

the kephalonia transform fault and the rotation of the apulian platform evidence from satellite geodesy this paper describes a collaborative gps project to determine recent crustal movements and deformations across the ne ionian sea this region is characterized by rifting in the african foreland pelagian sea subduction along the calabrian and west hellenic arcs rotation of the italian peninsula and distributed normal faulting in central greece from gps campaigns on the ionian islands and in nw greece performed in 1989 and 1991 a kinematic field is deduced which is controlled by the deep trough following the nw coast of kephalonia island it is concluded that this prominent bathymetric feature resembles an active fault system kephalonia fault which has the signature of a right lateral transform fault

longshore sand waves at southampton beach new york observation and numerical simulation of their movement abstract this paper describes measurements and numerical simulations of the movement of longshore sand waves observed at southampton beach long island new york these large morphologic features are created by periodic opening of a small inlet and subsequent welding of its ebb shoal to the beach longshore sand waves are wave like forms that maintain identity while moving along the shore and represent a simple type of collective sediment movement or largescale coastal behavior despite being described as early as 1939 few measurements of longshore sand waves have been made and their dynamic behavior is not well understood eleven longshore sand waves were identified along southampton beach and have an average length of 0 75 km and an amplitude of 40 m migration speed was greatest under winter wave action and reached an average 1 09 km year 1 and yearly average speed including summer calms was a much lower 0 35 km year 1 during a 16 month observation period the longshore sand waves did not disperse during their steady migration westward in the direction of predominant wave incidence and longer waves moved faster than those with smaller wavelengths a numerical model of shoreline change including both standard particulate longshore sand transport and a component describing migration of a longshore sand wave is developed in which the velocity of the wave is related to the calculated longshore discharge of water the model shows wave refraction to be an important mechanism contributing to the longevity of longshore sand waves acting to retard the otherwise expected diffusion model calculations of the migration of a single longshore sand wave agree quantitatively with the observations

first paleomagnetic evidence for a post eocene clockwise rotation of the western taurides thrust belt east of the isparta reentrant southwestern turkey abstract a paleomagnetic study was carried out on 23 sites sampled in paleocene eocene and lower miocene sedimentary formations of the western taurides belt east of the isparta reentrant the paleomagnetic data based on twelve suitable sites record a coherent post eocene 40 clockwise rotation throughout the area studied we interpret this regional rotation as a semi rigid rotation of the whole western taurides belt above a major deep decollement level together with previously published data these new results suggest that the isparta reentrant would result from diachronous opposite rotations of the two branches first a late eocene oligocene clockwise rotation of the akseki beysehir taurides initiating the tauride arc and then anticlockwise rotation of the lycian taurides probably during middle miocene times

stable isotope constraints on the transport of water to the andes between 22 and 26 s during the last glacial cycle abstract the modern climate over much of the andes between 22 and 26 s is very dry dated sediment cores from desiccated lake beds contain saline deposits salars that have halite fabrics that indicate during previous less arid climates saline lakes existed at salar de hombre muerto northwest argentina andean plateau and salar de atacama northern chile west flank of andes paleoclimate conditions are reconstructed from the stable isotope composition of paleo saline lake waters trapped in fluid inclusions in lacustrine halite models of isotopic steady state are applied to estimate the isotopic composition of inflow meteoric water to the paleo lake and paleo atmospheric water vapor the two salars climate records differ the timing of atacama saline lakes is similar to lake level highstands on the altiplano to the northeast with the deepest lake occurring between 24 and 19 8 ka the modern meteoric water source for atacama and the central andes is currently the tropical atlantic via the amazon basin and stable isotopic evidence indicates the same source of water for the paleo lakes in the atacama in contrast to the southeast at hombre muerto the lakes that intermittently occupied the salar became progressively smaller since 45 ka water isotope composition today reflects atmospheric recycling by evaporation condensation as it did between 24 and 20 ka whereas water transported to the earlier lakes does not indicate significant isotopic recycling using knowledge of modern day atmosphere oceanic circulation and forcing mechanisms we hypothesize that the shifts in moisture transport to these andean sites are directly tied to equatorial and south atlantic atmospheric and oceanic surface circulation

mixed siliciclastic carbonate evaporite sedimentation in an arid eolian landscape the khor al adaid tide dominated coastal embayment qatar abstract the khor al adaid embayment of southern qatar represents a unique shallow water mixed siliciclastic carbonate coastal depositional system that developed in a hyper arid climatic setting over the past 6000 years the embayment which was formed during the flandrian transgression as a result of flooding across a partially fault controlled incised fluvial drainage is supplied by quartz rich sands delivered by wind blown dunes migrating southward across the surface of qatar these offshore migrating eolian derived sediments are being redistributed by tidal currents in an otherwise low energy coastal zone where in situ formation of carbonate mud and a low diversity skeletal assemblage is ongoing within salinity restricted environments three depositional sectors are delineated 1 an energetic linear fault controlled entrance channel into which the eolian dunes spill directly 2 a relatively deep up to 20 m outer lagoon interpreted to represent a flooded karst collapse structure and 3 a sprawling low energy shallow physical oceanographic modeling integrating multi seasonal current meter and tidal gage measurements demonstrates tidal current flow velocities are relatively high in both the entrance channel and at the constricted entrance to the inner lagoon associated flow expansion into less confined areas results in deposition of the eolian derived sands as flood tidal deltas one in the outer and two in the inner lagoon a weakly developed ebb tidal delta occurs where the entrance channel debouches into the arabian gulf flood tide dominance is also apparent in entrance channel deposits where sand accumulates in seaward terminating ebb barbs along the margins of the flood dominant thalweg such flood tide dominance of the thalweg is unusual and likely reflects the absence of river discharge evidence of significant inverse estuarine circulation seaward flow of a brine along the embayment floor is mostly absent in spite of the landward increase of salinity where concentrations reach more than double normal seawater salinity in the inner lagoon modeling results show that seaward flowing brines formed in the inner lagoon are trapped in the relatively deep outer lagoon and that mixing by tidal currents in the energetic entrance channel precludes the formation of vertical density gradients there because siliciclastic mud is essentially absent and most of the sediment forming the deltas consists of sand upper intertidal deltaic deposits that would normally consist of mud are absent resulting in the flood tide deltas having a pronounced lobate geometry similar to that of fluvial deltas formed predominantly of sand away from tidal deltas low energy lagoons are floored by carbonate mud of local production with minor gypsum precipitating in the inner lagoon wind generated waves only locally influence sedimentation forming complex nearshore bars along some lagoonal shorelines the overall landward increase in salinity is accompanied by a decrease in the diversity of benthic fauna and their skeletal remains a fairly diverse faunal assemblage is observed in the entrance channel near the arabian gulf including colonial corals whereas the inner lagoon assemblage is dominated gastropods belonging to pirenella cingulata the remnants of large eolian dunes are preserved in the low energy setting of the inner lagoon segmenting the waterbody and locally increasing restriction the sedimentology of the arid zone coastal khor al adaid embayment may serve as an analogue for environmental settings that were perhaps more commonplace in arid zones of flooded continents during greenhouse times

coastline sand waves on a low energy beach at el puntal spit spain linear stability analysis 1 shoreline sand waves of approximately 125 150 m of wavelength and 15 m of amplitude in the offshore direction reached in a few days are often observed at the west end of el puntal spit santander spain they tend to last for about 2 months and do not show an evident alongshore propagation during that time since wave incidence on that beach is typically very oblique a shoreline linear stability analysis is performed to test whether those sand waves could be generated by shoreline instability because of the low energy wave climate and the steep mean bathymetric profile the predicted wavelength 100 150 m and growth time 4 8 days are much smaller than is typical on open ocean beaches this provides a unique opportunity to test high angle wave instability thus the role of the instability on the growth evolution and subsequent destruction of the sand waves is examined a remarkable agreement between predictions and observations regarding the wavelength and growth time is found furthermore by analyzing shoreline instability for a 2 year period where sand waves sometimes occur and sometimes do not a clear correlation is found between sand wave occurrence and predicted instability growth rate intriguingly results are less satisfactory regarding alongshore migration since the model predicts some migration that is not supported by observations however it becomes clear that the instability caused by high angle waves is crucial for shoreline sand wave formation at el puntal and should be considered for any future research

quaternary evolution of the corinth rift and its implications for the late cenozoic evolution of the aegean summary we present geological and morphological observations at different scales to constrain rates of faulting and the distribution of deformation in the seismically active aegean region we focus first on the 130 km long corinth rift an asymmetric graben where a flight of terraces of marine origin are uplifted we show that the edges of the terraces lie in the footwall of the normal fault bounding the corinth rift and correspond to sea level highstands of laic pleistocene age using a detailed analysis of aerial and spot imagery supported by field observations we have mapped 10 terrace platforms and strandlines ranging in elevation from 10 to 400 m over distances of 2 to 20 km from the fault the elevation of the terraces inner edges was estimated at 172 sites with an error of 5m this data set contains a precise description of the uplift and flexure of 10 different palaeohorizontal lines with respect to the present sea level to date the deformation we correlate the corinth terraces with late pleistocene oxygen isotope stages of high sea level stands and with global sea level fluctuations using a thick elastic plate model consistent with our current understanding of the earthquake cycle and a boundary element technique we reproduce the geometry of the shorelines to constrain both mechanical parameters and the slip on the fault we show that the seismogenic layer behaves over the long term as if its elastic modulus were reduced by a factor of about 1000 all the terraces are fitted for fault slip increasing in proportion to terrace age and the component of regional uplift is found to be less than 0 3 mm yr 1 the best fits give a slip rate of 11 3 mm yr 1 on the main rift bounding fault over the last 350 kyr other geological and morphologic information allows us to estimate the total age of the main fault 1 ma and to examine the mechanical evolution of the corinth rift the minimum observed sediment thickness in the gulf places an extreme check on the results of the modelling and a lower bound on slip rate of 6 7 mm yr 1 40 per cent less than estimated with modelling even this slip rate is nearly 10 times higher than for comparable features in most of the aegean and elsewhere in the world at a larger scale the spacing and asymmetry of the rift systems in the aegean suggest strain localization in the upper mantle with slow extension starting 15 myr ago or earlier the more recent 1 myr rapid phase of rifting in corinth partly reactivated this earlier phase of extension the younger faulting in corinth appears to result from its present location in the inhomogeneous stress field process zone of the south westward propagating tip of the southern branch of the north anatolian fault we extend these relations to propose a mechanical model for the late cenozoic evolution of the aegean as the arabia europe collision progressed in eastern turkey it caused anatolia to move to the west and the north anatolian fault to propagate into the aegean where the early slow extension started to be modified about 5 ma ago the process of propagation dramatically increased the activity of some but not all of the earlier rifts the model we present is compatible with tectonic observations as well as with the seismicity the palaeomagnetic rotations and the displacement field now observed with gps and slr

present day dynamics of the aegean region a model analysis of the horizontal pattern of stress and deformation in order to gain quantitative insight into the forces that control the present day stress field and pattern of horizontal motions in the aegean region we adopt a forward model approach mechanisms that have been proposed to explain the present day tectonics are represented to first approximation in terms of the expected force distributions on the basis of a thin elastic shell representation of the aegean lithosphere we then calculate the stress field and displacements associated with these force sets and compare the results with observations of the state of stress based on geological studies of fault kinematics strain as expressed by earthquake focal mechanisms and horizontal motions measured by means of satellite geodesy the two most commonly cited mechanisms suggested to control the aegean tectonics 1 the push exerted by the westward moving anatolian block and 2 forces associated with the hellenic subduction zone are first analyzed separately it is found that the westward anatolian push alone does not explain the observed prevalence of tensional stress this is also expressed in a mismatch between the displacements computed to result from the westward push and the observed horizontal velocities regarding the forces on the aegean overriding margin we find that a model with outward pulling forces of uniform magnitude acting normal to the arc from the sw peloponnese to rhodes yields a stress field that matches the observed pattern of tension to a large extent this distribution of forces is consistent with the notion of gravitational spreading of the aegean lithosphere the pattern of seismic strain of the overriding margin may evidence the occurrence of a small additional resistive force although the prevalence of tension thus appears due mainly to the subduction related forces other aspects of the stress field and also the pattern of horizontal motions indicate that these forces act in combination with westward push our model results allow us to address the relation between the forces experienced by the upper plate and the kinematics of subduction not just in terms of a vertical cross section but also by taking into account the along arc dimension

springwater provenance and flowpath evaluation in blue lake bonneville basin utah abstract water in utah and nevada is important for agriculture municipal use solute transport and ecosystem preservation large spring wetland systems occur on the playa margin of the bonneville basin including blue lake 15 km south of the bonneville salt flats on the utah nevada state border large spring systems have historically been studied as water budgets don t apparently balance from direct mountain front recharge nelson and mayo 2014 gardner and heilweil 2014 and others blue lake is no exception prior studies here have suggested discharge rates 0 04 0 05 km3 yr louderback and rhode 2009 greater than expected for modelled recharge in the surrounding mountain range 0 03 km3 yr three hypothesized recharge mechanisms for blue lake are tested mountain front recharge interbasinal groundwater flow and infiltration from historic lake bonneville remote sensing suggests that a conservative estimate of blue lake discharge constitutes 50 64 of modelled mountain front recharge flint et al 2011 major ions 18o 2h dissolved gases 14c 3he 4he ne ar kr xe and trace elements sr and 87sr 86sr isotopes comprehensively constrain recharge conditions water rock interactions flowpaths and groundwater provenance of this large spring system 14c signatures suggest that blue lake discharge has a transit time between 5 600 and 12 200 years older than that of fish springs noble gas concentrations in blue lake water suggest an elevated recharge temperature greater than 19 c and low salinity indicating a deep water table and high geothermal gradient in the recharge area 87sr 86sr ratios of playa margin springs are elevated from that of mid playa groundwaters springwaters from the adjacent mountain range and alluvial fill groundwater from the valley directly south of blue lake playa margin spring sr isotope values 0 713 0 714 are most similar to direct runoff from the deep creek range granodiorite outcrop 0 713 interbasinal groundwater flow in combination with mountain front recharge is best supported by chemical data rather than mountain front recharge alone or the slow discharge of regional aquifers recharged by lacustrine infiltration from lake bonneville

the strain pattern in the western hellenic arc deduced from a microearthquake survey summary than loo0 earthquakes recorded during 7 weeks in 1986 in the peloponnese and surrounding areas show shallow seismicity spread over a wide area bounded by the hellenic trench the highest level in the energy release is for clusters located along the hellenic trench where changes in the morphology are seen a few clusters are also observed as at the intersection between the gulf of corinth and the gulf of patras near the lake trikhonis or between kythira and crete in the peloponnese the shallow earthquakes do not define single faults but are diffusely distributed a higher concentration and a deepening of the foci within the whole crust towards the west seem to reflect a higher strain rate there fault plane solutions exhibit a scattered pattern for earthquakes shallower than 11 km but for earthquakes deeper than 11 km they show some consistency in the orientation of p t and b axes gently dipping nodal planes are seen all over the peloponnese with the conjugate vertical plane striking in various directions and with no consistency in the sense of motion these earthquakes are located between 8 and 18 km deep and could reflect a decoupling between the lower and the upper crust reverse faulting is seen in the gulf of kefallinia and the western peloponnese the p axes trend ne sw to e w normal faulting is seen in the gulf of corinth and in central peloponnese with the t axes trending n s and in the southern peloponnese where the t axes trend nw se the deformation over the western hellenic arc revealed by fault plane solutions of earthquakes with depth between 11 and 40 km appears to be the superposition of two phenomena first throughout the aegean crustal extension with orientation roughly parallel to the trench dominates with crustal shortening and subduction along the aegean arc superimposed on this is a more local effect of the collision between the aegea and apulia which seems to induce horizontal compression roughly perpendicular to the aegean arc west of the peloponnese and epirus the compression due to this decays eastward at a distance comparable with the width of the collision zone the deepening of the brittleductile transition is likely to be due to an increase of the strain field towards the ionian islands

modeling large scale shoreline sand waves under oblique wave incidence waves develop with wavelengths between 2 and 5 km they migrate downdrift at about 0 5 km yr and they reach amplitudes up to 120 m within 13 years larger wave obliquity higher waves and shorter wave periods strengthen the shoreline instability cross shore transport is essential for the instability and faster cross shore dynamics leads to a faster growth of the sand waves simulations with variable wave incidence angles alternating between 60 and 30 show that a large proportion of high angle waves is required for spontaneous sand wave formation at least 80 insight is provided into the physical mechanism behind high angle wave instability and the occurrence of a optimal length scale for sand wave growth the generic model results are consistent with existing observations of shoreline sand waves in particular with those along the southwest coast of africa

coastline undulations on the west coast of denmark offshore extent relation to breaker bars and transported sediment volume abstract this paper deals with field measurements of undulations of the bottom bathymetry along an otherwise straight coast at the danish west coast two bathymetric datasets and two time series of wave measurements are used in order to determine the following properties the offshore extent of shoreline undulations the amount of sediment transported alongshore in the shoreline undulations the relationship between the shoreline undulations and longshore bars and the relationship between the morphology and the hydrodynamics in one of the data sets the shoreline undulations are well correlated with undulations on the depth contours between 5 m and 2 m relative to mean sea level in the other data set only undulations on the depth contours between 1 m and 1 m are well correlated with the shoreline undulations the main difference in the wave climate between the two locations is the orientation of the shoreline such that the wave incidence angle is more oblique on the section of shoreline with well correlated depth contours suggesting that the well correlated depth contours are a result of the oblique wave incidence

active faulting and folding without topographic expression in an evaporite basin chile the salar de atacama in northern chile accumulated halite during the pliocene and quaternary under conditions that alternated between a saline lake and a dry salt flat hidden beneath its uninterrupted flat surface is the salar fault system the halite deposits provide a high resolution history of deformation contours on the ca 5 ma base of the halite unit in the southern salar defined in a deep oil exploration borehole and traced through reflection seismic lines reveal that net reverse offset across the salar fault system is down to the east by 900 m of that total 200 m occurred during the quaternary and 700 m during the pliocene distributions thicknesses and geometries of eight stratigraphic sequences within the halite unit reveal a history of episodic faulting and demonstrate that faulting during approximately half the 5 m y interval including the holocene did not generate fault scarps we suggest that deposition caused by evaporation of ground water brines in the salt flat rather than either dissolution or deflation has smoothed the topography of the dry lake bed across the active fault zone for the case of west directed groundwater flow we propose that the east facing salar fault system focuses groundwater flux along the eastern flank of the fault which enhances halite precipitation in the downthrown block during desiccated stages and counteracts fault driven topographic relief the realization that a seismic risk may exist even though the salar fault system is hidden leads to the appreciation that similar unrecognized seismic risks may exist in more populous arid basins

recharge to groundwater in the turi basin northern chile an evaluation based on tritium and chloride mass balance techniques summary the turi basin contains an unconfined phreatic aquifer within the toconce formation volcano sedimentary sequence that passes eastwards under the quaternary volcanic chain and outcrops in the altiplano the phreatic aquifer is floored by impermeable welded miocene ignimbrites precipitation captured by the volcanic edifices infiltrates through high permeability soils to recharge the phreatic aquifer the hydrochemistry of the groundwater in the phreatic aquifer shows little evidence of mixing with geothermal water and therefore approximates to a closed system tritium values demonstrate that recharge is occurring under current climatic conditions and takes around 40 years to pass 10 km from recharge areas on the slopes of the volcanoes and the altiplano to the center of the basin the chloride mass balance technique has been used to quantify precipitation recharge at 15 500 m3 d 1 this is significantly less than the flow through the phreatic aquifer 58 000 86 000 m3 d 1 calculated from its physical properties and the difference is interpreted to be due to subsurface inflow through the toconce formation from the altiplano the results of this study have wider application throughout the andean hydrological environment of northern chile

long term erosional hot spots in the southern brazilian coast 1 the southern brazilian coast is a sandy barrier adorned by subtle shoreline perturbations widespread in a rhythmical pattern previous works indicated that short and long term shoreline changes are not alongshore uniform they are based on coastline position monitoring geomorphological evidences historical cartographic documents and aerial photography moreover these studies associated the main observed erosional sites with high rates of sediment drift and energy focusing due to wave refraction nevertheless the role of the highly oblique incident waves in driving shoreline changes was not considered a recently derived sediment diffusion equation showed the possibility of coastal instability induced by incident waves with high obliqueness as opposed to the traditional approach therefore this paper applied these concepts to wave climate and performed coastal instability analysis to explain shoreline changes at an undulating littoral calculations showed wave climate yielding a negative instability index 0 13 when using a 42 month long time series of wave parameters obtained from a forecasting numerical model also the calculated direction asymmetry on wave climate revealed a net littoral drift consequently the sites between troughs and updrift flanks of shoreline undulations are expected to exhibit erosive processes this is the case in the most conspicuous long term erosional hot spots at the southern brazilian coast which was pointed out in earlier studies therefore coastal instability and littoral sediment drift analysis explained the main morphodynamic processes governing shoreline changes at the study area

an analog experiment for the aegean to describe the contribution of gravitational potential energy the southern aegean seafloor exhibits clear evidence of internal deformation stretching as shown by tectonics seismology and space geodesy we use an analog three layer laboratory experiment of sand silicone putty and honey to investigate the deformation of the southern aegean lithosphere the model is installed in a box and confined by a vertical wall we open a gate in the wall and observe the deformation of the two upper layers due to buoyancy forces the general pattern of the deformation of the southern aegean is found in the analog model we observe the formation of an arc spreading outward with time the extension is radial in the inner part but parallel to the arc in the external part and of comparable importance at both ends of the gate we observe strike slip motion dextral in the western part sinistral in the eastern part rotation clockwise in the western part counterclockwise in the eastern part of up to 40 is seen on both sides of the gate but is also present with a smaller amplitude far in the internal region partially due to distributed shear the spreading is associated with the thinning of the two upper layers and affects a region of dimensions comparable to the length of the free boundary this spreading does not propagate inward with time some pieces of material located near the active boundary remain undeformed during the experiment

a geodynamic framework for eastern mediterranean kinematics we use a finite element model incorporating plate motion boundary conditions fault constraints and space geodetic velocities to calculate eastern mediterranean plate kinematics and to estimate the motion of the region s major faults we then use subsets of these constraints to generate models testing different scenarios of driving forces slab roll back at the hellenic arc arabian plate push gravitational collapse of w anatolia to match the expected pattern of deformation we find that models combining only trench rollback and arabian push are unable to provide a good match to the observed deformation across western anatolia and the aegean and that we need to introduce the effects of mantle corner flow and gravitational collapse to fit observations

the evaluation of brine prospects and the requirement for modifications to filing standards the recent increase in demand for lithium has led to the development of new brine prospects particularly in the central andes the brines are hosted in closed basin aquifers of two types mature halite dominant and immature clastic dominant the estimate of elemental resources in these salars depends on a detailed knowledge of aquifer geometry porosity and brine grade the geometry of the aquifers can be evaluated by classical geophysical and drilling techniques but because the resource is a fluid with the attendant problems of in aquifer mixing and reorganization existing codes for filing resource and reserve estimates need modification total porosity is relatively straightforward to measure but effective porosity and specific yield which are required to estimate the resource are more difficult recovery factors are low compared with most metalliferous and industrial mineral deposits due to reliance on pumping of the brine from wells for extraction these and related issues lead us to believe that modifications to the existing standards for reporting mineral resources and reserves are required for these prospects

numerical modeling of shoreline undulations part 1 constant wave climate abstract this paper presents a numerical study of the non linear development of alongshore undulations up to fully developed quasi steady equilibrium a numerical model which describes the longshore sediment transport along arbitrarily shaped shorelines is applied based on a spectral wave model a depth integrated flow model a wave phase resolving sediment transport description and a one line shoreline model first the length of the shoreline undulations is determined in the linear regime using a stability analysis next the further evolution from the linear to the fully non linear regime is described in the fully non linear regime down drift spits and migrating shoreline undulations are described three different shoreline shapes are found depending on the wave conditions undulations with no spits undulations with shore parallel spit and undulations with reconnecting spits

seismic refraction profiles between cyprus and israel and their interpretation summary a long seismic refraction profile was carried out between southern israel and cyprus the seismic energy was generated by 33 sea shots each of 0 8 t explosives and was recorded by land stations in israel and cyprus and by ocean bottom seismographs deployed along the profile the results showed that the continental crust of southern israel thins towards the mediterranean underneath a northward thickening sedimentary cover cyprus is underlain by a 35 km thick continental crust thinning south wards and extending to mt eratosthenes between mt eratosthenes and the israel continental shelf the crystalline crust is composed of high velocity 6 5 km s 1 material and is about 8 km thick it is covered by 12 14 km of sediments and may represent a fossil oceanic crust

late pliocene age for the atacama desert implications for the desertification of western south america the atacama desert forms one of the major hyperarid deserts of the world previous studies suggest that desertification commenced at 14 ma during global climate desiccation sedimentologic data from middle miocene to upper pliocene successions in the modern atacama desert indicate that a semiarid climate persisted from 8 to 3 ma punctuated by a phase of increased aridity at ca 6 ma as such hyperaridity did not commence until the late pliocene implications are 1 that the rain shadow generated by the andean cordillera has had a minor influence on climate change and 2 that the upwelling north flowing cold humboldt current although important in establishing the generally arid climate of western south america did not control the shift to hyperaridity the formation of the hyperarid atacama desert in the late pliocene accompanied the development of the current phase of aridification in the sahara and namib deserts and is attributed to a phase of global climate cooling

distribution redox state and bio geochemical implications of arsenic in present day microbialites of laguna brava salar de atacama abstract understanding how microorganisms adapted to the high arsenic concentration present on early earth requires understanding of the processes involved in the arsenic biogeochemical cycle operating in living microbial mats to this end we investigated a living microbial mat from laguna brava salar de atacama chile a hypersaline lake with high arsenic concentration using an array of conventional geochemical techniques such as x ray diffraction sem edx and confocal laser scanning microscopy clsm combined with state of the art high resolution scanning imaging techniques including x ray micro fluorescence xrf and x ray absorption near edge structure xanes mapping this experimental approach allowed us to unravel the relationship between the microbial mat activity mineral occurrence arsenic speciation distribution of major and trace elements and their relationship with the mineralogy and the exopolymeric substances eps we show that as was not linked to ca or si and only moderately related to fe resulting from sorption onto an iron oxy hydroxide mineral in addition we were able to identify organic rich globules containing significant as but no other trace metal loid s and determine the co existence of as iii and as v these observations strongly support the occurrence of microbially mediated arsenic cycling in these microbial mats

the great atacama flood of 2001 and its implications for andean hydrology in february 2001 widespread flooding occurred throughout the atacama desert of northern chile and southern peru it was particularly severe in the rio loa basin where roads and bridges were disrupted and the town of calama inundated the instantaneous peak flow in the rio salado a tributary of the rio loa reached 310 m3 s 1 an order of magnitude higher than any previously recorded event the flood is estimated to have a return period of 100 200 years and is shown to have been caused by intense long duration rainfall in the western cordillera associated with la nina the surface water response is typical of arid areas and highly dependent on antecedent conditions but is quite different in perennial and ephemeral catchments ephemeral flood flows suffer high transmission losses recharging phreatic aquifers perennial rivers have lower runoff coefficients but baseflow levels remained high after the event for several months due to bank storage rebound and interflow extremely high energies of 3000 w m 2 were generated by the floods in the cordillera becoming less in the precordillera and downstream erosion and sediment transport were consequently highest in the upper and middle reaches of the rivers with mixed erosion deposition in the lowest reach the new insights gained from the interpretation and quantification of this event have important implications for palaeoenvironmental analysis hazard management water resource evaluation and the palaeohydrological evolution of the andes copyright 2005 john wiley sons ltd

orographic barriers high resolution trmm rainfall and relief variations along the eastern andes 1 quantifying the degree to which tectonic and erosive processes shape landscapes is key to understanding the evolution of tectonically active mountain belts here we explore the interplay of these two processes along the humid eastern flank of the south american andes we use high resolution tropical rainfall measurement mission trmm and srtm data to characterize elevation relief and hillslope angle of peak rainfall at orographic barriers over a distance of more than 3500 km along the eastern flanks we find that peak rainfall 3 5 m yr occurs at a mean elevation of 1 3 0 17 km a mean relief of 0 95 0 08 km and at moderate mean hillslope angles of 18 3 1 7 we suggest that topographic relief is the best first order rainfall predictor and we demonstrate how relief changes along strike south of the andean orocline alter rainfall distribution changes in climatic sedimentary and tectonic processes prevent the formation of high relief amounts at the mountain front and these areas are not characterized by pronounced rainfall peak

length scales for continental deformation in convergent divergent and strike slip environments analytical and approximate solutions for a thin viscous sheet model the deformation of a thin viscous layer that has a moving boundary is investigated for comparison with zones of deformation in the continental lithosphere exact analytical solutions for the case of a newtonian fluid and approximate solutions for the case of fluid with power law rheology show that when the imposed velocity vector is normal to the boundary congressional or extensional regime the deformation field decays away from the boundary with a characteristic length scale 1 3 to 1 10 the wavelength of the imposed boundary velocity distribution for n between 1 and 10 where n is the stress strain exponent in the rheology in contrast when the imposed velocity vector is parallel to the boundary transcurrent regime the length scale of the deformation field is approximately 4 times smaller in each case these length scales decrease approximately as n the difference in length scales arises even in the absence of any buoyancy forces acting on thickened or thinned crust such forces would modify the ratio of length scales but not sufficiently to affect this result

palaeomagnetic timing of the rotation and translation of cyprus abstract the geological evolution of the mesozoic troodos ophiolite complex in cyprus and the tectonic nature and timing of the palaeomagnetically indicated anticlockwise rotation of cyprus of some 80 and ca 15 northward translation have been open for debate for some time new palaeomagnetic data from 18 sites 180samples in the post ophiolite sediments ranging in age from upper cretaceous to upper miocene are presented most of the sites are of normal geomagnetic polarity but indications of reversed polarity have been found in an older group of sediments the lefkara formation of upper palaeocene age six sites from the older group of sediments upper cretaceous to eocene in age give a site mean direction of the af cleaned sediments of d i 323 29 with 95 18 while 5 sites from a younger group of sediments oligocene to miocene in age give a cleaned site mean direction of d i 334 58 with 95 9 these and published data suggest that an anticlockwise rotation of cyprus of 60 10 occurred early during the post igneous evolution of the cyprus oceanic crust between 90 and 50ma leaving only a minor anticlockwise rotation of 20 10 to occur during the last 50 ma it is furthermore concluded that the northward translation of cyprus of 15 mostly took place during the last 30ma it thus appears that a fairly rapid rotation of the cyprus microplate first took place in the late cretaceous and early tertiary time with an average angular velocity of 1 2 ma during which the northward translation was minor or negligible in the latter half of the tertiary the sense of movement appears to have radically changed the northward translation now being dominant with an average velocity of 5 6cm yr this temporal evolution is found to be in good agreement with the mesozoic and tertiary movements of the african lithospheric plate relative to europe as evidenced from the atlantic sea floor magnetic anomaly spreading history

the strain rate field in the eastern mediterranean region estimated by repeated gps measurements we use the combined gps velocity field of the eastern mediterranean for the period 1988 to 1996 to determine crustal deformation strain rates in a region comprising the hellenic arc the aegean sea and western anatolia we interpret the velocity field and determine the strain rate tensor by the spatial derivatives of the collocated motion vectors the region following the line marmara sea north aegean trough northern central greece and the central ionian islands is associated with strong right lateral shear motion with maximum shear strain rates of 180 nano strain a 180 10 9 a in the central aegean sea n s oriented extensional processes prevail reaching 100 nano strain a the southern aegean is characterized by relatively small strain rates maximum extensional components of the strain rate tensor reaching 150 nano strain a in a n s direction are found in central greece the hellenic arc is associated with moderate arc parallel extension and strong compression perpendicular to it projections of the strain rates parallel to the major fault zones reveal that the northern aegean is governed by the westward continuation of the north anatolian fault zone which is associated with strong dextral shearing maximum 220 nano strain a accompanied by numerous large earthquakes in this century

effects of a temperature dependent rheology on large scale continental extension the influence of a temperature dependent rheology on large scale continental extension is investigated using a thin viscous sheet model a vertically averaged rheology is used that is consistent with laboratory experiments on power law creep of olivine and that depends exponentially on temperature the behavior of the model depends principally on two parameters the peclet number which describes the relative rates of advection and diffusion of heat and a dimensionless activation energy which controls the temperature dependence of the rheology numerical calculations of such a thin sheet subjected to an extensional boundary condition show the following results at short times following the beginning of extension deformation occurs with negligible change in temperature so that only small changes in lithospheric strength occur due to attenuation of the lithosphere and maximum rates of deformation are located close to the extensional boundary however after a certain time interval thermal diffusion results in lowered temperatures in the lithosphere strongly increasing lithospheric strength and slowing the rate of extension this critical time depends principally on the peclet number and is short compared with the thermal time constant of the lithosphere the changes in strength cause the locus of high extensional strain rates to shift with time from regions of high strain to regions of low strain results of the calculations are compared with observations from the aegean where maximum extensional strains are found in the south near crete but the largest present day extensional strain rates occur about 300 km further north the comparisons support the hypothesis that the observed separation of the loci of maximum strain and maximum present day strain rates in the aegean may be the consequence of changes in lithospheric strength arising from the temperature dependent mechanical properties of lithospheric materials

modeling the long term diffusion and feeding capability of a mega nourishment a morphodynamic model based on the wave driven alongshore sediment transport including cross shore transport in a simplified way and neglecting tides is presented and applied to the zandmotor mega nourishment on the dutch delfland coast the model is calibrated with the bathymetric data surveyed from january 2012 to march 2013 using measured offshore wave forcing the calibrated model reproduces accurately the surveyed evolution of the shoreline and depth contours until march 2015 according to the long term modeling using different wave climate scenarios based on historical data for the next 30 yr period the zandmotor will display diffusive behavior asymmetric feeding to the adjacent beaches and slow migration to the ne specifically the zandmotor amplitude will have decayed from 960 m to about 350 m with a scatter of only about 40 m associated to climate variability the modeled coastline diffusivity during the 3 yr period is 0 0021 m2 s close to the observed value of 0 0022 m2 s in contrast the coefficient of the classical one line diffusion equation is 0 0052 m2 s thus the lifetime prediction here defined as the time needed to reduce the initial amplitude by a factor 5 would be 90 yr instead of the classical diffusivity prediction of 35 yr the resulting asymmetric feeding to adjacent beaches produces 100 m seaward shift at the ne section and 80 m seaward shift at the sw section looking at the variability associated to the different wave climates the migration rate and the slight shape asymmetry correlate with the wave power asymmetry w vs n waves while the coastline diffusivity correlates with the proportion of high angle waves suggesting that the dutch coast is near the high angle wave instability threshold

paleomagnetic evidence for cenozoic clockwise rotation of the external albanides abstract a paleomagnetic study of 750 samples obtained from 55 late eocene to middle pliocene sedimentary sites demonstrates a clockwise rotation of about 45 of the external zones of albania this rotation occurred either in two phases of roughly equal amplitude during the early middle miocene and plio pleistocene or in a single phase with a clear acceleration of the movement during the plio pleistocene the good agreement of these results with those from southern albania and northwestern greece indicates that a large geographical area is involved in the rotation the active aegean compressive front thus extends much farther north than hitherto believed and the rotational pattern is not significantly distorted by the tectonic discontinuities recorded by geological studies the external zones of the albano hellenic belt appear to have rotated virtually as a single entity from the peloponnesos to northern albania over a deep decollement level probably involving the basement itself

metamorphic core complexes of cordilleran type in the cyclades aegean sea greece the islands of ios and naxos in the cycladic archipelago greece contain elongate domes over which a pervasive north to north northeast stretching lineation is warped these islands may be metamorphic core complexes of cordilleran type involving middle crustal rocks drawn upward and outward from underneath the sedimentary basins now 100 km to the south from ca 25 ma onward during uplift the crystalline rocks now exposed on the islands were deformed noncoaxially in the deeper levels of a major shallow dipping ductile shear zone this shear zone may have connected with low angle normal faults in its upper levels because it is probable that its later history involved the metamorphic complexes being dragged out from under a stretching and fracturing upper plate composed mainly of unmetamorphosed sedimentary and ophiolite suite rocks this model can be extended to explain the exhumation of the high pressure low temperature metamorphic rocks on crete which with the cyclades forms a distended paired metamorphic belt separated by an active sedimentary basin

3d mapping hydrodynamics and modelling of the freshwater brine mixing zone in salt flats similar to the salar de atacama chile abstract salt flat brines are a major source of minerals and especially lithium moreover valuable wetlands with delicate ecologies are also commonly present at the margins of salt flats therefore the efficient and sustainable exploitation of the brines they contain requires detailed knowledge about the hydrogeology of the system a critical issue is the freshwater brine mixing zone which develops as a result of the mass balance between the recharged freshwater and the evaporating brine the complex processes occurring in salt flats require a three dimensional 3d approach to assess the mixing zone geometry in this study a 3d map of the mixing zone in a salt flat is presented using the salar de atacama as an example this mapping procedure is proposed as the basis of computationally efficient three dimensional numerical models provided that the hydraulic heads of freshwater and mixed waters are corrected based on their density variations to convert them into brine heads after this correction the locations of lagoons and wetlands that are characteristic of the marginal zones of the salt flats coincide with the regional minimum water brine heads the different morphologies of the mixing zone resulting from this 3d mapping have been interpreted using a two dimensional 2d flow and transport numerical model of an idealized cross section of the mixing zone the result of the model shows a slope of the mixing zone that is similar to that obtained by 3d mapping and lower than in previous models to explain this geometry the 2d model was used to evaluate the effects of heterogeneity in the mixing zone geometry the higher the permeability of the upper aquifer is the lower the slope and the shallower the mixing zone become this occurs because most of the freshwater lateral recharge flows through the upper aquifer due to its much higher transmissivity thus reducing the freshwater head the presence of a few meters of highly permeable materials in the upper part of these hydrogeological systems such as alluvial fans or karstified evaporites that are frequently associated with the salt flats is enough to greatly modify the geometry of the saline interface