changes in the permeability streaming potential and resistivity of a claystone from the nankai prism under stress permeability is the critical factor governing fluid flow in accretionary prisms accretionary wedges are highly deformed so permeability changes in an indurated claystone sample from the nankai accretionary prism were measured during a triaxial stress experiment by the pulse decay method three zones were identified from the loading test in zone i the sample has deformed less than 1 3 and its permeability was 5 10 20 m in zone ii the deformation reached 1 5 and the permeability was unstable with time in zone iii the sample deformation reached 2 and its permeability reached 3 8 10 18 m the permeability strongly decreased from 3 2 10 18 m to 1 7 10 19 m with increasing effective pressure from 2 3 to 10 8 mpa after the sample was well deformed zone iii the streaming potential was not measurable when the sample had a low permeability zone i but clearly occured when the permeability increased zone iii the streaming potential measured was 6 mv when the pore pressure pulse applied was about 1 17 mpa and the permeability 3 8 10 18 m our experiments suggest that shear deformation under low effective pressure increased the vertical permeability of sediments above the decollement this increase in permeability may be detected by measuring the streaming potential variations of flow rate of expelled fluid in accretionary wedges may be detected by monitoring changes of electrokinetic potential giving new insights on the state of stress related to the seismic cycles

volcanic shards from santorini upper minoan ash in the nile delta egypt one of the largest volcanic outbursts recorded in early human history is the cataclysmic eruption of santorini thera which occurred about 35 centuries ago in the southern aegean sea this explosive event termed upper minoan or upper thera produced a tephra fall believed by archaeologists and volcanologists to have been widespread in the eastern mediterranean1 4 upper minoan ash has been found on land in the aegean and hellenic arc regions including crete5 6 and rhodes7 to date however there has been no confirmed observation of this ash on land across the mediterranean in north africa we now report evidence for the presence of ash ejected from this explosion in sediment cores recovered in the eastern nile delta of egypt this discovery of upper minoan glass shards extends considerably the zone of confirmed ash fall to the southeast of santorini and serves as evidence of a major natural phenomenon affecting egypt during the reign of pharaohs in the eighteenth dynasty it is quite possible that this ash fall event may have given rise to texts pertaining to darkening of the sky and veiling of the sun in early historic records

lateglacial holocene environmental changes in the mediterranean alps inferred from lacustrine sediments this study investigates sediment cores from the mediterranean alpine lakes located in upvalley cirques upper than 1700 metres a s l using sedimentological palynological and geomorphological studies in order to document environmental changes following the last phase of glacier retreat these results are considered in the framework of the deglaciation characterized from 16 sediment cores from high altitude lakes and mires including 104 14c ages and geomorphological studies of the mediterranean alps considering each sediment core proxy as an independent observation i e comparisons between 14c ages and palynostratigraphy between 14c ages and lithostratigraphy between palynostratigraphy and lithostratigraphy these data are aimed at contributing to a better understanding of the timing of postglacial environmental changes the 14c ages combined with pollen biostratigraphy indicate that the deglaciation of cirque catchments is dated between 14 500 and 13 000 cal bp i e during the lateglacial interstadial greenland interstadial 1e the sixteen lacustrine and mire sediment records are systematically characterized by three units from bottom to top organic poor blue clay beige to light brown silty clay and organic rich dark brown gyttja lithotype during the younger dryas lakes located below 2300 m a s l were ice free and their pollen record indicates steppe conditions the sedimentary facies also informs on the timing of glacial dominated processes the onset of organic rich gyttja is dated at 11 000 cal bp suggesting the last influence of cirque glaciers in these lakes at the beginning of the holocene the timing of the onset of this organic rich unit differs in sites 2000 years probably due to an altitudinal and exposure gradient of the glacial cirques the presence of gyttja from 11 000 cal bp to present indicates biogenic infilling lake for all the holocene even though the literature have indicated rock glacier advances occurred during the holocene subboreal and lia in the south of the alps no significant sedimentological patterns related to glacier fluctuations are recorded in lake vens the glacier fluctuations in the mediterranean alps are concomitant with those dated in the non mediterranean alps thus suggesting a main common climate forcing however the increase in terrigenous sediment inputs since 1800 cal bp is mainly due to human activities

recent climate driven river incision rate fluctuations in the mercantour crystalline massif southern french alps abstract we present a new geomorphological analysis of the tinee river tributaries in the southern french alps based on numerical inverse and forward modelling of their longitudinal profiles we model their relative uplift history with respect to the main channel hence the incision rate history of this channel inverse models show that all tributaries have consistent incision rate histories with alternating high and low values a comparison with global temperature curves shows that these variations correlate with quaternary climate changes we suggest that during warm periods a wave of regressive erosion propagates in the tinee river while its tributaries deeply incise their substratum to catch up with the falling base level we also show that the post 140 ka history of this landscape evolution is dominated by fluvial incision we then perform forward models of river incision and simulate the incision of the tinee river system over a time span of 600 ka this model allows us to extract time and space incision rate variations of the tinee river with a background of a few mm yr 1 incision rate can increase up to more than 1 cm yr 1 during short periods of time due to climatic oscillations this result is compatible with published cosmogenic nuclide based dating which evidenced incision rates from 0 2 to 24 mm yr 1 the part of the channel located between 12 and 20 km downstream from the source has undergone several periods of rapid incision rates which could explain the steep hillslopes and the triggering of a landslide 10 ka ago

anisotropy of electrical conductivity record of initial strain at the toe of the nankai accretionary wedge an approach based on march s theory is applied to measurements of the anisotropy of electrical conductivity on samples and is used to quantify initial strain at the toe of the nankai accretionary wedge a quantitative determination of strain is possible from simple assumptions passive reorientation offlat pores forming the porous network and existence of a linear relationship between fabric tensor and electrical conductivity tensor we show that this simple model correctly accounts for the increase of anisotropy with compaction at a reference site located in the trench ocean drilling program drill site 1173 at the toe of the accretionary wedge site1174 development of anisotropy in the horizontal plane and concurrent reduction of vertical plane anisotropy are observed this can be explained by 12 horizontal ductile shortening occurring after decollement initiation but before slip on imbricate thrust faults anisotropy in the underthrust sequence is correctly described by vertical compaction consistent with decoupled stress states across the decollement at site 1174 the magnitude of ductile strain implies at least 75m slip on the decollement ductile shortening is associated with porosity loss implying partly drained conditions above the decollement

influence of secular variation of the geomagnetic field on production rates of in situ produced cosmogenic nuclides abstract scaling factors are presented that allow a full description of the cosmic ray flux modulation during secular variation of the geomagnetic field these scaling factors are analogous to those determined in a similar work dunai t j earth planet sci lett 2000 176 157 169 that were accurate for field strengths equivalent to present day field strength but cannot accommodate field strength variations strategies to derive the relevant geomagnetic field parameters are discussed and are tested with existing production rate calibrations for 3 he a production rate of 103 4 2 atoms g olivine yr sea level and for zero cutoff rigidity was derived from calibration sites from hawaii western usa and canary islands covering the time range of 2 281 kyr

preservation of inner gorges through repeated alpine glaciations the origins of alpine valleys are controversial topographic data from the swiss alps suggest that the valleys have been incised progressively during consecutive glacial interglacial cycles

modification of streaming potential by precipitation of calcite in a sand water system laboratory measurements in the ph range from 4 to 12 spontaneous potentials associated with volcanic activity are often interpreted by means of the electrokinetic potential which is usually positive in the flow direction i e zeta potential of the rock is negative the water rock interactions in hydrothermal zones alter the primary minerals leading to the formation of secondary minerals this work addresses the study of calcite precipitation in a sand composed of 98 quartz and 2 calcite using streaming potential measurements the precipitation of calcite as a secondary mineral phase inferred by high calcite saturation indices and by a fall in permeability has a significant effect on the electrokinetic behaviour leading to a significant reduction in the zeta potential in absolute value and even a change in sign the measured decrease in zeta potential from 16 mv to 27 4 mv takes place as the ph rises from 4 to 7 while it remains constant at 25 1 mv as the ph increases from 8 to 10 5 for ph higher than 10 5 calcite precipitates and is expected to coat the quartz surface the measured zeta potential vary from 17 to 8 mv for ph ranging from 10 6 to 11 7 depending on the amount of precipitated calcite indicated by the decrease in permeability the observed change in sign of the electrical surface potential rules out the usual qualitative interpretation of sp anomalies in order to determine fluid circulations even at ph lower than 9 if calcite is widely present as a secondary mineral phase since the electrical surface potential of calcite depends also on co2 partial pressure and ca2 therefore sp anomalies as measured in hydrothermal field without mineralogical analyses of hydrothermal deposits and without geochemical fluid survey should be interpreted with caution

fluvial landscape response time how plausible is steady state denudation whether or not steady state topography and denudation are probable states depends on the timescale of system response to tectonic and climatic perturba tions relative to the frequency of those perturbations this paper presents analytical derivations of algebraic relations for the response time of detachment limited fluvial bedrock channel systems both to tectonic and climatic perturbations detachment limited fluvial erosion is described by the stream power incision model and the derivations are limited to the applicability of that model all factors likely to influence system response time that are not adequately captured by the stream power incision model will tend to increase the response time the calculations presented thus provide minimum estimates of landscape response time and therefore over predict the prob ability of attaining and sustaining steady state topography and denudation the central range of taiwan is used as a case study to estimate response times in a landscape often argued to be in steady state model parameters are fit to modern stream profiles by assuming that the topography represents a quasi steady state form estimated response times generally range from 0 25 to 2 5 ma depending on the non linearity of the incision rule and the magnitude and type of perturbation thus it may be reasonably argued that steady state topography and denudation are likely to prevail during periods of climatic stability response time is sufficiently short compared with plate tectonic timescales however rapid climatic fluctuation in the quaternary appears to preclude the attainment of steady state conditions in modern orogens motivation

late cenozoic uplift of mountain ranges and global climate change chicken or egg the high altitudes of most mountain ranges have commonly been ascribed to late cenozoic uplift without reference to when crustal thickening and other tectonic processes occurred deep incision and recent denudation of these mountain ranges abundant late cenozoic coarse sediment near them and palaeobotanical evidence for warmer climates where high mountain climates today are relatively cold have traditionally been interpreted as evidence for recent uplift an alternative cause of these phenomena is late cenozoic global climate change towards lower temperatures increased alpine glaciation a stormier climate and perturbations to humidity vegetative cover and precipitation

long term fluvial incision rates and postglacial river relaxation time in the french western alps from 10be dating of alluvial terraces with assessment of inheritance soil development and wind ablation effects studying river long profile development as a response to tectonic and climatic controls requires reliable age dating of paleo profile remnants preserved as river terraces cosmic ray exposure cre dating often represents the only method available to date river terraces but the interpretation of cosmogenic nuclide concentrations is complicated by pre depositional inheritance and post depositional disturbance of the terrace deposits through pedogenesis and surface inflation or deflation here we use cosmogenic 10be measurements to date alluvial terraces in the french western alps in order to estimate river incision rates and to infer river response to climatic fluctuations and tectonic forcing we assess inheritance by constructing 10be concentration vs pebble depth profiles and use a monte carlo technique to estimate terrace ages we find that inheritance is negligible on all terraces enabling us to date terraces as young as 5 ky terraces that predate the last glaciation experienced intense pedogenesis and wind ablation which led to significant scatter in the 10be concentrations of surface samples we assess these effects using a model of 10be ingrowth and show that the oldest cre ages of surface clasts are close to the probable terrace age we study two catchments which have undergone varying degrees of glacial disruption the buech river experienced variations in runoff and sediment flux during the last glaciation as well as occasional ice dammings of its outlet its upper terraces record incision rates averaged over 190 ky of 0 8 mm yr consistent with denudation rates estimated in the surrounding areas and suggesting long term stability of river incision rates climatic forcing is well documented for the drac river which was repeatedly dammed by glaciers during cold periods its postglacial incision history was triggered by an 800 m drop in base level following ice dam disappearance long profile development by knickpoint propagation explains the time lag of 2 5 ky between this base level drop and terrace abandonment upstream as well as subsequent peak incision rates of 6 cm yr followed by a gradual decrease in incision rates the present knickpoint location 55 km upstream from the glacial damming site enables us to calculate a fluvial response time of 15 20 ky controlled by knickpoint propagation rates of several meters per year within the drac river

dating the incision of the yangtze river gorge at the first bend using three nuclide burial ages incision of the yangtze river gorge is widely interpreted as evidence for lower crustal flow beneath the southeast margin of the tibetan plateau previous work focused on the onset of incision but the duration of incision remains unknown here we present cosmogenic nuclide burial ages of sediments collected from caves on the walls of the gorge that show the gorge was incised 1 km sometime between 18 and 9 ma thereafter incision slowed substantially we resolve middle miocene burial ages by using three nuclides and accounting for in situ muogenic production this approach explains the absolute concentrations of 10be 26al and 21ne as well as 26al 10be and 21ne 10be ratios a declining incision rate challenges existing geodynamic interpretations by suggesting that either 1 surface uplift has ceased immediately south of the plateau margin or 2 gorge incision is not a useful proxy for the timing of surface uplift

ultra rapid landscape response and sediment yield following glacier retreat icy bay southern alaska abstract glacial retreat and opening of taan fjord an arm of icy bay alaska in the last two decades drove a base level fall of 400 m at the outlets of four tributary valleys in the region of the current tyndall glacier terminus response in the tributary valleys to this base level fall includes evacuation of stored sediment incision of slot gorges into bedrock and landsliding on valley walls fluvial transfer of eroded bedrock glacial deposits and stored nonglacial fluvial deposits after 1983 resulted in progradation of fan deltas toward the fjord centerline at the outlet of each of the four catchments in the largest nonglacial tributary valley 0 08 km 3 8 of the 0 59 km 3 of 500 m thick stored fluvial and colluvial deposits has been transferred to the adjacent fjord a percentage of the fjord sedimentation in the last two decades thus includes material eroded from bedrock and stored in the landscape during the previous glacial expansions distal deltaic deposits extend across the fjord floor and likely interfinger with distal proglacial deltaic deposits sourced from the tyndall glacier a paraglacial landscape response such as the one exhibited in upper taan fjord where sediment delivery to fjords from tributary sources in synchrony with sediment produced by primary bedrock erosion by glaciers helps to explain the order of magnitude discrepancy between sediment yields from alaskan tidewater glaciers on 10 0 to 10 2 year timescales and sediment yields and exhumation rates on 10 4 to 10 6 year timescales

spontaneous potentials and resistivity surveys applied to hydrogeology in a volcanic area case history of the chaine des puys puy de dome france two geophysical methods resistivity soundings and spontaneous potentials sp are used to investigate aquifers in the quaternary volcanic formations of the chaine des puys france the interpretation of the resistivity soundings required a specific work of determination of the resistivity of the formations concerned the basement topography characterized by axial horst and graben structures and perpendicular palaeovalleys was revealed sp was developed experimentally in the field and theoretically it is shown that the sp anomalies can be considered as double layer potentials with their source on the aquifers interfaces the most significant of them is the water table which creates an sp anomaly of similar but inverted form sp anomalies due to flows in unconfined aquifers in palaeovalleys and in volcanic ranges are computed and compared with the observed ones these two methods have determined the extent and the boundary conditions of the different hydrogeological basins and have determined the major drainage axes and the groundwater flow pattern

the relative efficacy of fluvial and glacial erosion over modern to orogenic timescales it has been debated whether rivers or glaciers are more effective agents of erosion a global compilation of erosion rates reveals that both are capable of generating rates of erosion that match or exceed the highest rates of rock uplift since the late nineteenth century it has been debated whether rivers or glaciers are more effective agents of erosion1 the dramatic landscapes associated with glaciated terrain have often led to the argument that glaciers are more erosive than rivers and recent studies have documented the topographic signature of an ice controlled limit of mountain height known as the glacial buzz saw 2 3 here we present a new global compilation of erosion rates which questions the conventional view of glaciers and erosion in regions of rapid tectonic uplift erosion rates from rivers and glaciers both range from 1 to over 10 mm yr 1 indicating that both are capable of generating erosion rates matching or exceeding the highest rates of rock uplift moreover a comparison of erosion rates over timescales ranging from 101 to 107 years indicates that glacial erosion tends to decrease by one to two orders of magnitude over glacial cycles whereas fluvial erosion rates show no apparent dependence on time we conclude that tectonics controls rates of both fluvial and glacial erosion over millennial and longer timescales and that the highest rates of erosion 10 mm yr 1 generally result from a transient response to disturbance by volcanic eruptions climate change and modern agriculture

climatic reconstruction in europe for 18 000 yr b p from pollen data an improved concept of the best analogs method is used to reconstruct the climate of the last glacial maximum from pollen data in europe in order to deal with the lack of perfect analogs of fossil assemblages and therefore to obtain a more accurate climate reconstruction we used a combination of pollen types grouped according to plant phenology and present climate constraints rather than pollen percentages for each individual taxon the distribution of pollen taxa into plant functional types pfts is aimed to reflect the vegetation in terms of biomes which have a wider distribution than a species the climatic variables are then calibrated on these pfts using an artificial neural network technique the use of pfts allowed us to deal with situations where pollen assemblages have only partial modern analogs the method is applied to the glacial steppic vegetation in europe using 15 pollen records north of the pyrenees alps line the reconstructed temperatures were lower than today 30 10 degrees c for the temperature of the coldest month t c and 12 3 degrees c far the annual mean t ann south of that line t c and t ann anomalies were respectively 15 5 degrees c and 10 5 degrees c the available moisture index and annual precipitation were also lower than present 60 20 north of mediterranean sea 800 100 mm for precipitation in italy and greece the available moisture was 20 lower with a precipitation anomaly of ca 600 200 mm southward the moisture index was close to that at present 20 and precipitation was lower 300 300 mm c 1998 university of washington

river incision and migration deduced from 36cl cosmic ray exposure durations the clue de la cerise gorge in southern french alps abstract we estimate recent 20 ka incision and lateral migration rate on a spectacular n s striking gorge cross cutting n dipping limestones in a fold and thrust belt of the external southern french alps upstream of the gorge the river makes a right angle turn and follows the limestone surface parallel to the bedding direction ew eighteen samples were gathered along two vertical river polished profiles and three others on the denuded north dipping surface layer in order to determine river incision and lateral migration timing and rates surface age exposures of polished river cliff and bedding surface have been obtained from 36cl cosmogenic nuclide dating and allow us to constrain the rate of vertical incision and of surface denudation of the jurassic limestone layer fifteen 36cl exposure ages have been obtained and range from 21 ka to 3 ka samples clearly define two age height linear trends which slopes correspond to incision rates of 1 and 0 3 mm yr respectively the transition from low to high incision rate occurs at about 12 ka i e during the younger dryas glacial phase data also indicate that the vertical incision of the n s branch of the gorge is coeval with the lateral northward river migration of its e w branch associated with the denudation of the limestones surface extrapolating incision rates deduced from 36cl exposure ages through time suggests that the incision of the clue and denudation of the jurassic limestones started about 500 600 ka ago

active transpressional tectonics in the andean forearc of southern peru quantified by 10be surface exposure dating of an active fault scarp our understanding of the style and rate of quaternary tectonic deformation in the forearc of the central andes is hampered by a lack of field observations and constraints on neotectonic structures here we present a detailed analysis of the purgatorio fault a recently recognized active fault located in the forearc of southern peru based on field and remote sensing analysis pleiades dem we define the purgatorio fault as a subvertical structure trending nw se to w e along its 60km length connecting on its eastern end to the crustal incapuquio fault system the purgatorio fault accommodates right lateral transpressional deformation as shown by the numerous lateral and vertical plurimetric offsets recorded along strike in particular scarp with a 5m cumulative throw is preserved and displays cobbles that are cut and covered by slickensides cosmogenic radionuclide exposure dating be 10 of quartzite cobbles along the vertical fault scarp yields young exposure ages that can be bracketed between 0 to 6ka depending on the inheritance model that is applied our preferred scenario which takes in account our geomorphic observations implies at least two distinct rupture events each associated with similar to 3 and similar to 2m of vertical offset these two events plausibly occurred during the last thousand years nevertheless an interpretation invoking more tectonic events along the fault cannot be ruled out this work affirms crustal deformation along active faults in the andean forearc of southern peru during the last thousand years

formation of inner gorges abstract under certain conditions a distinctive type of landform the inner gorge evolves in drainage basins undergoing persistent base level lowering inner gorges are typical of basins in north coastal california u s a and one such basin was selected for detailed study based on analysis of along channel distribution of rock types streamside land sliding and stored sediment as well as computation of stream power the following set of conditions appears to accompany the formation of an inner gorge 1 inner gorge parent materials are relatively competent homogenous rock types 2 in inner gorge reaches there is an absence of any base level control that would prevent downcutting 3 continued downcutting occurs due to continued base level fall and this fall is most likely induced by tectonic uplift 4 mass slope failures that form steep straight slopes debris slides are the main denudational hillslope process in the inner gorge 5 sufficient stream power is available to transport landslide derived material out of the inner gorge reach such that alluvial sediment does accumulate in the reach over time and 6 the initial condition of the landscape is a low relief erosionally mature land surface into which the inner gorge is cut this initial condition implies that inner gorges develop in tectonically rejuvenated landscapes the processes of denudation on inner gorge slopes acting over a time scale of 105 years result in a style of landform evolution that approximates parallel slope retreat this type of slope retreat maintains the distinct inner gorge morphology during sustained downcutting though the analysis is confined to one basin in northern california so as to provide a detailed framework to understand inner gorge landform inner gorges appear to be commonplace in areas of moderate to high uplift where lithologic and tectonic conditions are appropriate for their formation a global search for this landform yet to be undertaken is needed to confirm whether it indeed occurs where the above conditions are met

simulation of electrical conduction in geomaterials by spice electrical responses of the subsurface can be used to identify geologic strata locate anomalies detect and delineate contamination among many other applications all these applications depend on the spatial variations of electrical properties in the subsurface and the resulting flow pattern of electric current due to the heterogeneity of the subsurface and complex boundary conditions three dimensional electric current flow problems are not easy to analyze in particular when the response is frequency and or time dependent in this paper a method of electric circuit analogy is proposed to simulate the electrical responses of geomaterials using the circuit simulator spice the technique will allow simulation of more complex electrical conduction behavior of geomaterials without much extra effort the excellent agreement between simulated results and analytical solutions developed for surface geophysical techniques establishes the viability of the method limitations of the approach and potential solutions to relax these limitations and other potential applications of the technique in geosciences are also discussed

experimental measurements of the streaming potential and seismoelectric conversion in berea sandstone the streaming potential across a porous medium is induced by a fluid flow due to an electric double layer between a solid and a fluid when an acoustic wave propagates through a porous medium the wave pressure generates a relative movement between the solid and the fluid the moving charge in the fluid induces an electric field and seismoelectric conversion in order to investigate the streaming potential and the seismoelectric conversion in the same rock sample we conduct measurements with berea sandstone saturated by nacl solutions with different conductivities we measure the electric voltage streaming potential across a cylindrical sample in nacl solutions with different conductivities and under different pressures to determine the dc coupling coefficients we also measure the seismoelectric signals induced by acoustic waves with a berea sandstone plate at different frequencies and solution conductivities the pressures of the acoustic waves are calibrated with a standard hydrophone bruel 8103 at different frequencies 15 120 khz we calculate the quantitative coupling coefficients of the seismoelectric conversion at dc and at high frequencies with samples saturated by solutions with different conductivities when the berea sandstone sample is saturated by the nacl solution with 0 32 ms m in conductivity for example the dc and seismoelectric coupling coefficients at 15 khz are 0 024 v pa and 0 019 v pa respectively the seismoelectric coupling coefficient is an important and helpful parameter for designing a seismoelectric tool more experimental measurements of seismoelectric coupling coefficients in the frequency range of 100 hz to 15 khz are needed in the future

orogeny and orography the effects of erosion on the structure of mountain belts a numerical model of the coupled processes of tectonic deformation and surface erosion in convergent orogens is developed to investigate the nature of the interaction between these processes crustal deformation is calculated by a two dimensional finite element model of deformation in response to subduction and accretion of continental crust erosion operates on the uplifted surface of this model through fluvial incision which is taken to be proportional to stream power the relative importance of the tectonic and erosion processes is given by a dimensionless erosion number relating convergence velocity rock erodibility and precipitation rate this number determines the time required for a system to reach steady state and the final topographic shape and size of a mountain belt fundamental characteristics of the model orogens include asymmetric topography with shallower slopes facing the subducting plate and an asymmetric pattern of exhumation with the deepest levels of exhumation opposite to subduction these characteristics are modified when the regional climate exhibits a dominant wind direction and orographically enhanced precipitation on one side of the mountain belt the two possible cases are dominant wind in the direction of motion of the subducting plate and dominant wind direction in the opposite direction of the subducting plate velocity models of the former case predict a broad zone of exhumation with maximum exhumation in the orogen interior models of the latter case predict a focused zone of exhumation at the margin of the orogen and at high erosion number a reversal in the topographic asymmetry natural examples of these two cases are presented the southern alps of new zealand exhibits the climate and exhumation asymmetry characteristic of wind in the direction opposite to motion of the subducting plate the asymmetry of topography suggests that erosion is not efficient enough to have reversed the topographic asymmetry the contrasting example of dominant wind in the direction of subduction motion is provided by the olympic mountains of washington state in this case exhumation of deep levels of the cascadia accretionary wedge shows a broad domal pattern consistent with the observed orographic precipitation

late quaternary incision rates in the vesubie catchment area southern french alps from in situ produced 36cl cosmogenic nuclide dating tectonic and climatic implications we have estimated recent river incision rates using the in situ produced 36cl cosmogenic nuclide concentrations the target site consists of a 25 m high vertical profile along a polished river cliff located in jurassic limestones in the vesubie catchment area in the southern french alps the 36cl exposure ages of the sampled river polished surface range from 3 to 14 ka i e after the last glacial maximum our data suggest as a first approximation a linear age height relationship and lead to a mean incision rate of 2 2 mm a 1 over the last 14 ka more precisely incision rates are characterized by two peaks reaching 2 and 4 5 mm a 1 at 4 5 ka and 11 12 ka respectively separated by a period experiencing a lower incision rate 1 mm a 1 a chi plot of the river longitudinal profile suggests that on the long term the river is close to equilibrium conditions with a concavity index of 0 475 the evolution of the vesubie river longitudinal profile over a time period of 2 ma based on the stream power law of river incision was then modeled with varying erodibility coefficients and uplift rates ranging from 0 5 to 2 mm a 1 the best fitting models yield erodibility coefficient values ranging from 2 5 to 9 0 10 6 m 0 475 a 1 for the considered uplift rates for long term uplift rates lower than 2 mm a 1 an increase of the erodibility coefficient during the last 16 ka with two peaks at 11 12 and 4 5 ka is necessary to precisely match the observed incision rates and is interpreted as resulting from recent climatic changes these variations do not strongly affect the general shape of the river profile and suggest that the measured short term incision rate is dominated by a climatic signal which does not preclude the possible role of tectonic uplift

electrokinetic spontaneous polarization in porous media petrophysics and numerical modelling abstract the behaviour of streaming potential is directly related to movement of groundwater the responses for typical subsurface flows are modelled to investigate possibilities of spontaneous polarization sp when performing quantitative data interpretation the physical properties of geomaterials related to streaming potential are described a magnitude range of streaming current coefficient is assessed for geomaterials and found to be from 10 10 to 10 8 a pa m depending on water salinity and rock composition the electrical sources of sp caused by groundwater flow in saturated media are theoretically described it is shown that sp is completely defined by three types of electrical sources situated 1 on boundaries where water enters or quits porous media 2 in areas with transient regime and 3 on the boundaries of rocks with different properties hydraulic conductivity streaming current coefficients and electrical conductivity a 2d computer program based on the method of finite difference was created to provide numerical successive modelling of both groundwater flow and sp using sill s geophysics 48 1983 76 approach first the water heads are calculated then electrical sources of sp are obtained on the basis of the calculated heads and coefficient of streaming current finally the sp is obtained on the basis of calculated electrical sources and subsurface electrical conductivity numerical examples illustrating sp responses of infiltration of barrage with different electrical conductivity and of well pumping are discussed field data obtained at the site containing the dam between superficial artificial reservoir and the river are interpreted on the basis of numerical modelling the discussed method can be mainly used for additional calibration of groundwater flow models

evolution of gravity driven rock slope failure and associated fracturing geological analysis and numerical modelling abstract an accurate analysis of fracture and cleavage anisotropies along two landslides in the argentera massif french southern alps was performed in order to relate the fracturing mode to the rock slope failure state the mature la clapiere landslide and the incipient isola landslide were investigated in both cases the gneissic rock schistosity was found sub horizontal in the vicinity of the landslides at shallow depths while it was sub vertical elsewhere at the massif s scale in addition to the well known regional tectonic fracture sets we identified in both cases a new family of vertical valley parallel vp fractures the vp fractures were only observed on the lower part of slopes affected by landslides where schistosity was found sub horizontal the vp fractures are clearly related to the decrease in schistosity dip and correspond to fold extrado like joints the proximity of the schistosity folds and the associated vp joints to the landslides suggests that they are gravity driven the presented 2 d finite difference models of the slope destabilisation in the la clapiere site shade light on possible mechanisms of the indicated gravity induced processes a progressive degradation of the material strength was imposed in these models to simulate the weathering effect which led to inelastic deformation damage at the lower part of slope this was followed by the formation of dense sub vertical deformation bands and then by the initiation of a landslide in the area corresponding to the actual position of the la clapiere landslide it is suggested that the gravity induced damage in the lower part of slope increases the permeability and thereby accelerates the weathering that causes a more rapid strength reduction the latter results in the tilting folding of pre existing fabrics and the related vp fracturing the la clapiere landslide is initiated in the upper part of this zone

vertical gps ground motion rates in the euro mediterranean region new evidence of velocity gradients at different spatial scales along the nubia eurasia plate boundary we use 2 5 to 14 years long position time series from 800 continuous global positioning system gps stations to study vertical deformation rates in the euro mediterranean region we estimate and remove common mode errors in position time series using a principal component analysis obtaining a significant gain in the signal to noise ratio of the displacements data following the results of a maximum likelihood estimation analysis which gives a mean spectral index 0 7 we adopt a power law white noise stochastic model in estimating the final vertical rates and find 95 of the velocities within 2 mm yr with uncertainties from filtered time series 40 smaller than from the unfiltered ones we highlight the presence of statistically significant velocity gradients where the stations density is higher we find undulations of the vertical velocity field at different spatial scales both in tectonically active regions like eastern alps apennines and eastern mediterranean and in regions characterized by a low or negligible tectonic activity like central iberia and western alps a correlation between smooth vertical velocities and topographic features is apparent in many sectors of the study area glacial isostatic adjustment and weathering processes do not completely explain the measured rates and a combination of active tectonics and deep seated geodynamic processes must be invoked excluding areas where localized processes are likely or where subduction processes may be active mantle dynamics is the most likely process but regional mantle modeling is required for a better understanding

landscape response to tectonic forcing digital elevation model analysis of stream profiles in the mendocino triple junction region northern california the topographic evolution of orogens is fundamentally dictated by rates and patterns of bedrock channel incision quantitative field assessments of process based laws are needed to accurately describe landscape uplift and denudation in response to tectonics and climate we evaluate and calibrate the shear stress or similar unit stream power bedrock incision model by studying stream profiles in a tectonically active mountain range previous work on emergent marine terraces in the mendocino triple junction region of northern california provides spatial and temporal control on rock uplift rates digital elevation models and field data are used to quantify differences in landscape morphology associated with along strike northwest to southeast changes in tectonic and climatic conditions analysis of longitudinal profiles supports the hypothesis that the study area channels are in equilibrium with current uplift and climatic conditions consistent with theoretical calculations of system response time based on the shear stress model within uncertainty the profile concavity of the trunk streams is constant throughout the study area 0 43 as predicted by the model channel steepness correlates with uplift rate these data help constrain the two key unknown model parameters the coefficient of erosion k and the exponent associated with channel gradient n this analysis shows that k cannot be treated as a constant throughout the study area despite generally homogeneous substrate properties for a reasonable range of slope exponent values n best fit values of k are positively correlated with uplift rate this correlation has important implications for landscape evolution models and likely reflects dynamic adjustment of k to tectonic changes due to variations in orographic precipitation and perhaps channel width sediment load and frequency of debris flows the apparent variation in k makes a unique value of n impossible to constrain with present data

significant increase in relief of the european alps during mid pleistocene glaciations the effect of expanded glaciation on the relief of mountain ranges is debated chronometric and model data from the european alps suggest that relief in the rhone valley was enhanced as a result of the increased incision of the valley following the mid pleistocene climate transition

increase in late neogene denudation of the european alps confirmed by analysis of a fission track thermochronology database abstract a sharp increase in deposited sediment volume since pliocene times has been observed worldwide and in particular around the european alps this phenomenon has been linked to a rise in denudation rates controlled by an increase of either climatic or tectonic forcing observation of in situ cooling histories for orogens is critical to assess the reality of the inferred increase in denudation rates and to determine whether this phenomenon is widespread or localized at active tectonic structures we exploit the unique density of fission track ages in the western european alps to reconstruct cooling isoage surfaces and to estimate exhumation rates on the orogen scale between 13 5 and 2 5 ma our novel technique is based on the association of isoage contours with age elevation relationships it uses map view interpolation enabling a spatio temporal analysis of exhumation rates over the entire western alps the resulting exhumation histories reconstructed for eight areas of the western alps display strong similarities in timing and rates with orogen wide average denudation rates inferred from sediment volumes this consistency validates the use of both techniques for the study of an orogen characterized by strong relief and high recent exhumation rates we conclude that exhumation rates in the western alps have increased more than twofold since late miocene times this increase may have been locally modulated by the distinct response of different tectonic units

an analytical solution to assess the sh seismoelectric response of the vadose zone fil monachesi leonardo bruno universidad nacional de rio negro sede alto valle instituto de investigaciones en paleobiologia y geologia argentina consejo nacional de investigaciones cientificas y tecnicas argentina

detection of fluid flow variations at the nankai trough by electric and magnetic measurements in boreholes or at the seafloor detection of changes in the flow rate of expelled fluids in accretionary prisms by monitoring of electric and magnetic fields is discussed a numerical model of the electric and magnetic fields associated with fluid flow variations at the nankai trough is presented which gives a numerical solution of the coupled system of electric convection currents and conduction currents that directly determines the magnetic anomaly itself measurements in a borehole located between two vents are shown to be well adapted to detection of fluid flow variations using the vertical gradient of the electric potential and the horizontal magnetic field the vertical electric field is about 10 mv km up to 500 m depth where there is a lithologic reflector and about 50 mv km below this reflector the horizontal gradient of the magnetic field is 2 nt km at the seafloor modelization with a lower fault conductivity and a larger decollement thickness has also been modeled the vertical gradient of the horizontal magnetic field is 5 to 15 nt km a variation of 3 mv and 1 5 to 3 nt at 600 m depth in a borehole could reveal a fluid flow rate variation of 20 which is a reasonable fluid flow change based on some observations at short scale time since a 1 5 to 3 nt anomaly seems easier to detect than a 3 mv anomaly it is likely that the variation of the magnetic field would more sensitively reveal fluid flow variations when monitoring the magnetic field at the seafloor a change of 0 4 nt km in the horizontal gradient could reveal a fluid flow rate variation of 20

on the difficulty of detecting streaming potentials generated at depth in order to investigate how a streaming potential coefficient measured in the laboratory at a typical scale of 10 cm can be incorporated into a field model with a typical scale of 1 to 10 km we measured the electric field induced by water flows forced at 150 m depth through a 10 m wide granite fractured zone the water flows were obtained by pumping cyclically 10 m of water from a borehole that cut the fractured zone at depth and contemporaneously reinjecting it into another borehole located 50 m away after one day a steady state fluid flow regime was reached with pumping cycles lasting 45 minutes indicating a hydraulic conductivity of 10 5 m s 1 and a specific storage coefficient of 3 25 10 6 m 1 the expected self potential at the surface was an anomaly with two maxima of opposite sign and 2 v amplitude each both located 160 m away from the middle of the borehole heads the signal being divided by two 500 m away from the middle of the borehole heads in agreement with wurmstich and morgan 1994 instead we observed an electrical signal of 8 mv midway between the borehole heads and smaller than 5 mv 33 m away from the borehole heads the discrepancy observed between the data and the model can be explained by fluid flow leakages that occurred close to the water table head represented about 20 of the total water flow and activated smaller but closer electric sources this experiment thus illustrates the practical difficulty of detecting streaming potentials generated at depth it shows in particular that in fractured zones and hence in the vicinity of a major active fault small water flows located distantly from an energetic targeted source but close to some of the electrodes of the network can sometimes drastically distort the shape of the expected anomaly models of possible electrical earthquake precursors therefore turn out to be more speculative than expected

recognition of the minoan tephra in the acigol basin western turkey implications for inter archive correlations and fine ash dispersal here we report the recognition of the minoan tephra layer in the acigol basin western turkey which represents the most eastward occurrence of this tephra on land and the first in continental deposits out of lacustrine sediments in mainland turkey the correlation is supported by glass and mineral geochemistry which includes solution and laser ablation icp ms data for trace and rare earth elements thickness and grain size data allow the extension of already described occurrences to an area of about 359 000 km 2 from the eastern mediterranean to black sea throughout central western turkey coupling dispersal area and grain size data suggests the joint influence of high and low atmosphere dynamics in dispersal of fine ash during volcanic eruptions the thickness and lateral continuity of the minoan tephra in the acigol basin testifies to the widespread impact on the late bronze age environment of mainland turkey of this important ash deposit copyright 2013 john wiley sons ltd

epigenetic gorges in fluvial landscapes epigenetic gorges form when channels that have been laterally displaced during episodes of river blockage or aggradation incise down into bedrock spurs or side walls of the former valley rather than excavating unconsolidated fills and reinhabiting the buried paleovalley valley filling events that promote epigenetic gorges can be localized such as a landslide dam or an alluvial debris flow fan deposit at a tributary junction or widespread such as fluvial aggradation in response to climate change or fluctuating base level the formation of epigenetic gorges depends upon the competition between the resistance to transport strength and roughness of valley filling sediments and a river s ability to sculpt and incise bedrock the former affects the location and lateral mobility of a channel incising into valley filling deposits the latter determines rates of bedrock incision should the path of the incising channel intersect with bedrock that is not the paleovalley bottom epigenetic gorge incision by definition post dates the incision that originally cut the valley strath terraces and sculpted bedrock walls that form in relation to epigenetic gorges should not be used to directly infer river incision induced by tectonic activity or climate variability rather they are indicative of the variability of short term bedrock river incision and autogenic dynamics of actively incising fluvial landscapes the rate of bedrock incision associated with an epigenetic gorge can be very high 1 cm yr typically orders of magnitude higher than both short and long term landscape denudation rates in the context of bedrock river incision and landscape evolution epigenetic gorges force rivers to incise more bedrock slowing long term incision and delaying the adjustment of rivers to regional tectonic and climatic forcing copyright 2008 john wiley sons ltd

curvelet based seismoelectric data processing seismoelectromagnetic conversions are induced through electrokinetic phenomena occurring when passing seismic waves induce relative fluid to solid displacements information on porous material properties provided by the type i coseismic electric field accompanying surface and body waves is limited to the vicinity of the electrical receivers as opposed to the type ii electromagnetic interface response ir which can help detect porous contrasts and or fluid changes within the subsurface at depth for general field geometries the problem is that type ii disturbances exhibit lower amplitudes than type i fields and are difficult to access directly hence separating both types of waves is a critical step when processing seismoelectric data synthetic seismograms and electrograms generated with a full waveform seismoelectric forward modelling code written by garambois dietrich enabled us to study the behaviour of the ir s characteristic dipolar amplitude pattern recovered through filtering the definitive version is available at www blackwell synergy com to better preserve the ir amplitudes we have developed a new filtering strategy based on the fast discrete curvelet transform seismic or seismoelectric wave fronts can be optimall described using this multiscale decomposition over multidirectional anisotropic needle shape structures we have built a mask in the curvelet domain zeroing out seismoelectric samples corresponding to non zero samples from the accelerogram thus taking advantage of the relationship between seismic and seismoelectric waves for type i fields this mask consists of a threshold function combined with a gaussian distribution promoting horizontal i e zero slowness directions when applied to synthetic data this filter enabled to successfully extract the ir although less altering its dipolar radiation pattern than the conventional dip based techniques this strategy was successfully applied to a seismoelectric data set acquired in sedimentary deposits and permitted to isolate an ir generated at the water table

climatic significance of glacier retreat and rockglaciers re assessed in the light of cosmogenic dating and weathering rind thickness in claree valley brianconnais french alps recent advances in geochronology provide opportunities to identify the glacial and periglacial sequences in mountain area in this paper we focus on the upper durance catchment southern french alps in the claree valley where no absolute chronological benchmark was defined glacial remnants and periglacial features were investigated integrated within a chronological scenario thanks to relative weathering rind thickness and absolute cre technique dates we find evidence of the existence of a late glacial valley glacier that has never been reported before then the upper valleys became ice free during a period corresponding to the early holocene climate optimum whereas two sequences of cirque glaciation are identified during the second half of the holocene we also show evidence of three main generations of rockglaciers which also mainly developed during the second half of the holocene probably at the end of the subboreal period the location and the altitudes of rockglaciers are strongly dependent on the geomorphic setting especially the location of the sediment sources hence complicating their palaeo climatic interpretations

depth determinations of shallow hydrothermal systems by self potential and multi scale wavelet tomography in hydrothermal studies the depth of the hydrothermal system is always required but rarely known via traditional geophysical exploration techniques while previous studies have shown that continuous wavelet transform algorithms applied to self potential data can theoretically determine the depth of the hydrothermal fluids this study uses multi scale wavelet tomography with multiple wavelets field measurements and geophysical models to accurately determine this depth on stromboli waita and masaya volcanoes multi scale wavelet tomography of field measurements gives reproducible depth results supported by independent geophysical measurements and models and accurately locates the main water flow paths at shallow depths unlike other traditional geophysical methods multi scale wavelet tomography using self potential data is a low cost tool to rapidly determine depths of the shallowest hydrothermal structures this approach has the potential to significantly enhance our ability to locate geothermal systems and monitor active volcanoes

three dimensional modelling of streaming potential summary the self potential sp method responds to the electrokinetic phenomenon of streaming potential and has been applied to hydrogeologic and engineering investigations to aid in the evaluation of subsurface hydraulic conditions to enable the study of variably saturated flow problems of complicated geometry a 3 d finite volume algorithm is developed to evaluate the sp distribution resulting from subsurface fluid flow the algorithm explicitly calculates the distribution of streaming current sources and solves for the sp given a model of hydraulic head and prescribed distributions of the streaming current cross coupling conductivity and electrical conductivity the forward solution is verified by comparing it with an analytical solution for a point source of flow and measured data taken at the surface of a homogeneous embankment we apply the forward model to a synthetic pumping well example to illustrate that heterogeneous physical property distributions can result in significant charge accumulation the sign and magnitude of this secondary charge is determined by the physical property and potential gradients at the interface and can complicate the interpretation of sp data when a single primary flow source is assumed the 3 d character of the sp response to seepage through an embankment and foundation is illustrated in a preliminary study of sp data collected at a dam site in british columbia

bedrock incision rock uplift and threshold hillslopes in the northwestern himalayas the topography of tectonically active mountain ranges reflects a poorly understood competition between bedrock uplift and erosion dating of abandoned river cut surfaces in the northwestern himalayas reveals that the indus river incises through the bedrock at extremely high rates 2 12 mm yr 1 in the surrounding mountains the average angles of hillslopes are steep and essentially independent of erosion rate suggesting control by a common threshold process in this rapidly deforming region an equilibrium is maintained between bedrock uplift and river incision with landsliding allowing hillslopes to adjust efficiently to rapid river down cutting

frost cracking control on catchment denudation rates insights from in situ produced 10be concentrations in stream sediments ecrins pelvoux massif french western alps the potential tectonic and climatic controls on erosion rates in the european alps and other mountain belts remain strongly debated we have quantified denudation rates at catchment scales using in situ produced cosmogenic nuclides 10be in stream sediments sampled at the outlets of twelve variously sized 27 1072 km2 catchments of the ecrins pelvoux massif french western alps with average elevations ranging from 1700 to 2800 m spatially averaged denudation rates corrected for potential shielding by little ice age glaciers vary from 0 27 0 05 to 1 07 0 20 mm yr on millennial timescales our results exhibit a correlation 2 0 56 between denudation rate and mean catchment elevation in the absence of significant correlation with any other morphometric parameters relief slope catchment size hypsometry etc although such variations in erosion rates have been previously linked to variations in tectonic uplift rate the relatively small size and tectonic homogeneity of our study area exclude a strongly variable tectonic control we interpret the increase in erosion rate with elevation as the effect of frost controlled processes which are strongly temperature dependent we use a one dimensional heat flow model driven by high resolution instrumental temperature records from the study area to correlate the variability in denudation rates with the integral of the absolute temperature gradient within the frost cracking window 3 to 8 c a proxy of the frost cracking intensity for each catchment the results imply that the efficiency of frost cracking constitutes a major control on catchment wide denudation rates in the study area explaining more than half the measured variability in these rates our study shows that present day denudation of the ecrins pelvoux massif is controlled by a climatically driven factor and suggests that frost cracking processes impose an important control on the post glacial topographic evolution of mid latitude mountain belts

deglaciation history at the alpine mediterranean transition argentera mercantour sw alps from 10be dating of moraines and glacially polished bedrock estimating the extent and age of the last glacial maxima as well as the chronology of glacial recessions in various environmental contexts is key to source to sink studies and paleoclimate reconstructions the argentera mercantour massif being located at the transition between the alps and the mediterranean sea its deglaciation chronology can be compared to the sediment budget of the var river marine delta in this paper the deglaciation is constrained by 13 new and 22 reassessed cosmic ray exposure cre 10be datings of moraines and polished crystalline bedrocks these data allow for the first time to fully reconstruct the deglaciation history at the scale of the entire massif in agreement with a major glacier recession at ca 15 ka at the onset of bolling transition this contribution reveals a glacier climate relationship more sensitive to warming phases in the southern alps highlighted by a major decrease of glaciers after ca 15 ka this major deglaciation is correlated with a 2 5 fold decrease of sediment discharge of rivers into the mediterranean sea main deglaciation of the massif upper slopes 2 700 2 800 m a s l occurred after the lgm at 20 8 18 6 ka followed by the lower slopes 2 300 m a s l at 15 3 14 2 ka finally the flat polished surfaces above 2 600 m a s l and the zones confined within narrow lateral valleys were likely affected by progressive ice melting of remaining debris covered glaciers and moraine erosion following the younger dryas re advance stage between 12 and 8 9 ka at lower elevations a sediment core in the vens lake located at 2 300 m a s l shows onset of lake sedimentation at ca 14 ka and a transition towards a vegetated environment after 8 ka final stabilization of moraines occurred at 5 ka which might reflect denudation acceleration during the holocene humid phase

plio pleistocene increase of erosion rates in mountain belts in response to climate change here we review an ensemble of observations that point towards a global increase of erosion rates in regions of elevated mountain belts or otherwise high relief since the onset of northern hemisphere glaciation about 2 3 ma during that period of earth s history atmospheric co2 concentrations may have dropped and global climate cooled and evolved towards high amplitude oscillating conditions that are associated with the waxing and waning of continental ice sheets in the northern hemisphere we argue for a correlation between climate change and increased erosion rates and relief production which we attribute to some combination of the observed cooling onset of glaciation and climatic oscillation at orbital timescales in our view glacial erosion played a major role and is driven by the global cooling furthermore analyses of the sedimentary fluxes of many mountain belts show peaks of erosion during the transitions between glacial and inter glacial periods suggesting that the variable climatic conditions have also played a role

present day uplift of the european alps evaluating mechanisms and models of their relative contributions abstract recent measurements of surface vertical displacements of the european alps show a correlation between vertical velocities and topographic features with widespread uplift at rates of up to 2 2 5 mm a in the north western and central alps and 1 mm a across a continuous region from the eastern to the south western alps such a rock uplift rate pattern is at odds with the horizontal velocity field characterized by shortening and crustal thickening in the eastern alps and very limited deformation in the central and western alps proposed mechanisms of rock uplift rate include isostatic response to the last deglaciation long term erosion detachment of the western alpine slab as well as lithospheric and surface deflection due to mantle convection here we assess previous work and present new estimates of the contributions from these mechanisms given the large range of model estimates the isostatic adjustment to deglaciation and erosion are sufficient to explain the full observed rate of uplift in the eastern alps which if correct would preclude a contribution from horizontal shortening and crustal thickening alternatively uplift is a partitioned response to a range of mechanisms in the central and western alps the lithospheric adjustment to deglaciation and erosion likely accounts for roughly half of the rock uplift rate which points to a noticeable contribution by mantle related processes such as detachment of the european slab and or asthenospheric upwelling while it is difficult to independently constrain the patterns and magnitude of mantle contributions to ongoing alpine vertical displacements at present future data should provide additional insights regardless interacting tectonic and surface mass redistribution processes rather than an individual forcing best explain ongoing alpine elevation changes

numerical analysis of seismoelectric wave propagation in spatially confined geological units using numerical modelling we investigate the evolution of seismoelectric effects induced by seismic excitation in spatially confined lithological units typical geometries represent clay lenses embedded in an aquifer or petroleum deposits in a host rock in fluid saturated rocks seismic waves can generate electromagnetic fields due to electrokinetic coupling mechanisms associated with such processes in the vicinity of the fluid mineral interface two seismoelectric phenomena are investigated 1 the co seismic field associated with the seismic displacement at each point in a subsurface and 2 the interface response generated at layer boundaries our modelling uses a simplified time domain formulation of the coupled problem and an efficient 2d finite element implementation to gain insight into the morphogenetic field behaviour of the seismoelectric effects several numerical simulations for various target geometries were treated accordingly we varied both the thickness of the confined units and the value of the electrical bulk conductivity in porous media analysis of these effects shows differences between interface responses for electrically conductive versus resistive units so the pertinent contrast in electrical bulk conductivity controls the shape and structure of these seismoelectric conversion patterns moreover the seismoelectric interface response captures both the petrophysical and geometrical characteristics of the geological unit these models demonstrate the value of using seismoelectric interface response for reservoir characterization in either hydrogeological or hydrocarbon exploration studies

production of cosmogenic radionuclides at great depth a multi element approach abstract for the last two decades in situ produced cosmogenic nuclides are increasingly applied in earth sciences to quantify surface processes in parallel significant reduction of the analytical uncertainties linked to advances in accelerator mass spectrometry ams allows more precise measurements however among all the published works on cosmogenic nuclides only few studies are dedicated to a better understanding of their production systematic or to a better constrain of the physical parameters involved in their production thus an approach to investigate in situ produced cosmogenic nuclides 10 be 26 al and 36 cl along a single 11 meter long core drilled from the surface and composed of carbonates and quartzose conglomerates has been launched these measurements have been used to quantify muon induced productions based on natural samples for each studied nuclide contrary to the current most oftenly used calculation of muon induced production parameters which are based on irradiation experiments at discrete energies productions based on natural samples are considering the entire energy range of particles reaching the ground surface the evolution of 36 cl concentrations with depth needs to agree with those parameters deduced from 10 be and 26 al data this is optimized when considering a fast muon induced 36 cl production contribution and a spallation production rate at sea level high latitude slhl of 42 0 2 0 atoms 36 cl g ca 1 a 1 1 sigma uncertainty

long lasting transcurrent tectonics in sw alps evidenced by neogene to present day stress fields abstract the sw alps are an active orogen undergoing intra mountainous extension and peripheral compression we discuss the significance of syn orogenic extension based on a comparison of paleo stress derived from fault slip data inversion reflecting the long term

characterization of electrical daily variations induced by capillary flow in the non saturated zone electrical daily variations without an associated magnetic field were observed for a period of six weeks on independent parallel dipoles during the one year electrode inter comparison experiment that took place in garchy france from april 1995 to april 1996 these daily variations appeared suddenly during summer when the soil was dry on the surface their amplitude ranged from 0 1 to 1 5 mv for 50 m long dipoles and characteristic relative phases the amplitude of the variations was found to be related to soil temperature these daily variations are accounted for in a model where streaming potentials are produced by coherent capillary flow in the non saturated zone such daily variations are important to control in long period magnetotelluric sounding and may be of practical use for agricultural applications as their amplitude strongly depends on time varying soil conditions they may also lead to erroneous interpretations as earthquake precursors

inner gorges incision history a proxy for deglaciation insights from cosmic ray exposure dating 10be and 36cl of river polished surfaces tinee river sw alps france editor a yin keywords river gorges incision cre 10 be and 36 cl dating river polished surfaces 10 be and 36 cl cosmic ray exposure cre dating performed on river polished surfaces of river gorges in a mountain to sea river system in the french sw alps highlights transient erosional events involving incision rates 10 mm a 1 these events took place during the last two major deglaciation phases following 1 the last glacial maximum lgm at 16 14 ka 2 the younger dryas at 8 11 ka and during the warm and humid holocene climatic optimum at 4 5 ka these periods of high incision rates 3 30 mm a 1 alternated with periods of low incision rates 1 mm a 1 which probably correspond to a long term equilibrium between incision and relative uplift the alpine river staircase shape profiles evidence local and transient responses that are ascribed to cumulate disequilibrium after the long time spanned glaciations after each glaciation rivers rush down to get closer to their equilibrium profile incision is amplified both by the sediment discharge due to the erosion of moraines and by landslides triggered by the glacier retreat

dependence of seismoelectric amplitudes on water content summary the expectation behind seismoelectric field measurements is to achieve a combination of the sensitivity of electrical properties to water content and permeability and the high spatial resolution of seismic surveys a better understanding of the physical processes and a reliable quantification of the conversion between seismic energy and electric energy are necessary and need to take into account the effect of water content especially for shallow subsurface investigations we performed a field survey to quantify the seismoelectric signals as the water content changed we measured seismoelectric signals induced by seismic wave propagation by repeating the observations on the same two profiles during several months the electrical resistivity was monitored to take into account the water content variations weshowthatthehorizontalcomponentoftheseismoelectricfield normalizedwithrespectto the horizontal component of the seismic acceleration is inversely proportional to the electrical resistivity 0 42 0 25 assuming that the observed resistivity changes depend only on the water content this result implies that the electrokinetic coefficient should increase with increasing water saturation taking into account the water saturation and combining our results with the archie law for the resistivity in non saturated conditions the normalized seismoelectric field is a power law of the effective saturation with the exponent 0 42 0 25 n where n is archie s saturation exponent

self potential signals induced by periodic pumping tests 1 we measured the variations of the self potential sp during periodic pumping tests performed at a test site located near a freshwater reservoir kemnader see bochum germany successions of injection and production intervals were applied in a borehole penetrating a jointed sandstone aquifer we report the sp observations for tests with periods ranging between 10 and 60 min and flow rates between 10 and 25 l min 1 the sp responses at the surface exhibit the imposed period but are not truly harmonic contrary to the hydraulic pressure and sp measured in monitoring wells in the grassy zone around the injection well the amplitude of the sp signals decreases with distance from the injection well around one order of magnitude at 10 m in rough agreement with predictions for radial flow in a homogeneous medium around an infinite source the shape of the sp responses also evolves with distance fourier spectral analysis reveals that the surface signals generally contain two main components at the main period and at half the period with the relative weight of the subperiodic components increasing with distance furthermore the characteristics of the sp responses depend on whether the boreholes are left open or closed by packers the comparison between surface and borehole measurements suggests that nonlinear phenomena are acting probably related to the saturation and desaturation processes occurring in the vadose zone

scaling factors for the rates of production of cosmogenic nuclides for geometric shielding and attenuation at depth on sloped surfaces abstract the decrease in rates of production of cosmogenic nuclides occurs because of shielding of cosmic rays by mountains sloped surfaces and local rock formations that block them when a large part of the sky is blocked this correction is large and requires detailed model calculations this paper considers three geometries a rectangular obstruction a triangular obstruction and a sloped surface other geometries can be considered as a combination of these the results are presented in terms of formulas and graphs so that the reader can easily apply them to common field situations any use of cosmogenic nuclides in the study of geomorphic processes or forms must consider factors that introduce variations in the production of nuclides

spatial and temporal pattern of erosion in the three rivers region southeastern tibet convergence and collision between india and eurasia have produced the tibetan plateau which stands 5 km high over a region of 3 million km2 its southeastern margin lies in the restraining bend between the sichuan basin and the eastern himalayan syntaxis in this region three parallel rivers the salween the mekong and the yangtze carve gorges up to 3 km deep along the longitudinal profiles large scale knickzones defined by very high steepness correspond to the gorges of the salween and mekong the yangtze instead has a nearly linear profile upstream from its first big bend new low temperature thermochronometric data reveal a complex pattern of erosion in the three rivers region from the salween in the west to the yangtze in the east the magnitude and rate of erosion decrease from south to north erosion rates exhibit variable gradients in space and time along the salween and the mekong a northward increase of erosion rate is followed by a decrease with additional distance to the north variations of erosion rate in time are characterized by a deceleration along the salween and a general deceleration with local acceleration along the mekong this pattern together with river profile analysis is best explained by active coupling between tectonics and river incision related to the indentation and northward migration of the corner of the indian continent

self potential and current channelling anomalies in self potential sp are usually explained in terms of geochemical activity however there are other sources of current which cause complications in the interpretation in particular dc telluric currents can be generated outside the survey region contrasts in resistivity cause current channelling and secondary voltages can be induced by leakage the effect can be demonstrated using network theory and internal sources can be emphasized by subtraction joint surveys are required to demonstrate correlations with apparent resistivity

streaming potential from multiphase flow in trying to understand the affect of electrokinetics on the spontaneous potential sp log the focus has generally been on the solid brine streaming potential within the accuracy of the measurements the streaming potential coupling coefficient is shown to be independent of the permeability of the rock the solid brine streaming potential is of much smaller magnitude than the electrostatic potentials from gas liquid and liquid liquid flow air bubbles were found to increase the streaming potential coupling coefficient by more than two orders of magnitude over the value for single phase brine flow thus two phase gas liquid flow is more likely to have a significant impact on the sp log than is single phase liquid flow two phase oil brine flow may also produce a larger electrokinetic potential than single phase flow the magnitude of the electrokinetic potential caused by oil brine flow will depend on the composition of the oil and the brine trace materials can have a major impact on the electrokineti

latest pleistocene and holocene glacier variations in the european alps in the alps climatic conditions reflected in glacier and rock glacier activity in the earliest holocene show a strong affinity to conditions in the latest pleistocene younger dryas glacier advances in the alps related to younger dryas cooling led to the deposition of egesen stadial moraines egesen stadial moraines can be divided into three or in some cases even more phases sub stadials moraines of the earliest and most extended advance the egesen maximum stabilized at 12 2 1 0 ka based on 10be exposure dating at the schonferwall tyrol austria and the julier pass outer moraine switzerland final stabilization of moraines at the end of the egesen stadial was at 11 3 0 9 ka as shown by 10be data from four sites across the alps from west to east the sites are piano del praiet northwestern italy grosser aletschgletscher central switzerland julier pass inner moraine eastern switzerland and val viola northeastern italy there is excellent agreement of the 10be ages from the four sites in the earliest holocene glaciers in the northernmost mountain ranges advanced at around 10 8 1 1 ka as shown by 10be data from the kartell site northern tyrol austria in more sheltered drier regions rock glacier activity dominated as shown for example at julier pass and larstig valley tyrol austria new 10be dates presented here for two rock glaciers in larstig valley indicate final stabilization no later than 10 5 0 8 ka based on this data we conclude the earliest holocene between 11 6 and about 10 5 ka was still strongly affected by the cold climatic conditions of the younger dryas and the preboreal oscillation with the intervening warming phase having had the effect of rapid downwasting of egesen glaciers at or slightly before 10 5 ka rapid shrinkage of glaciers to a size smaller than their late 20th century size reflects markedly warmer and possibly also drier climate between about 10 5 ka and 3 3 ka conditions in the alps were not conducive to significant glacier expansion except possibly during rare brief intervals past tree line data from kaunertal tyrol austria in concert with radiocarbon and dendrochronologically dated wood fragments found recently in the glacier forefields in both the swiss and austrian alps points to long periods during the holocene when glaciers were smaller than they were during the late 20th century equilibrium line altitudes ela were about 200 m higher than they are today and about 300 m higher in comparison to little ice age lia elas the larstig rock glacier site we dated with 10be is the type area for a postulated mid holocene cold period called the larstig oscillation presumed age about 7 0 ka our data point to final stabilization of those rock glaciers in the earliest holocene and not in the middle holocene the combined data indicate there was no time window in the middle holocene long enough for rock glaciers of the size and at the elevation of the larstig site to have formed during the short infrequent cold oscillations between 10 5 and 3 3 ka small glaciers less than several km2 may have advanced to close to their lia dimensions overall the cold periods were just too short for large glaciers to advance after 3 3 ka climate conditions became generally colder and warm periods were brief and less frequent large glaciers for example grosser aletschgletscher advanced markedly at 3 0 2 6 ka around 600 ad and during the lia glaciers in the alps attained their lia maximum extents in the 14th 17th and 19th centuries with most reaching their greatest lia extent in the final 1850 1860 ad advance

pleistocene holocene climate change re establishment of fluvial drainage network and increase in relief in the swiss alps abstract data are presented about modern sediment discharge of the swiss rivers and related to the size of catchments the information reveals that the central alps have experienced denudation rates of 0 15 mm yr 1 in the foreland and 0 5 mm yr 1 in the alpine core mapping however indicates that modern erosion only affects 30 50 of the alpine surface and that fluvial and associated hillslope processes have focused erosion in 50 200 m deep valleys these valleys are incised into the glacial surface if this limited spatial extent of erosion is considered then effective erosion rates are significantly higher than average denudation rates these effective rates equal or locally exceed modern rates of rock uplift this implies that the modification of erosional processes related to the pleistocene holocene climate change has resulted in an increase in the relief at a local scale at a drainage basin scale however the relief appears not to change at present

seismoelectric wave propagation numerical modelling in partially saturated materials to better understand and interpret seismoelectric measurements acquired over vadose environments both the existing theory and the wave propagation modelling programmes available for saturated materials should be extended to partial saturation conditions we propose here an extension of pride s equations aiming to take into account partially saturated materials in the case of a water air mixture this new set of equations was incorporated into an existing seismoelectric wave propagation modelling code originally designed for stratified saturated media this extension concerns both the mechanical part using a generalization of the biot gassmann theory and the electromagnetic part for which dielectric permittivity and electrical conductivity were expressed against water saturation the dynamic seismoelectric coupling was written as a function of the streaming potential coefficient which depends on saturation using four different relations derived from recent laboratory or theoretical studies in a second part this extended programme was used to synthesize the seismoelectric response for a layered medium consisting of a partially saturated sand overburden on top of a saturated sandstone half space subsequent analysis of the modelled amplitudes suggests that the typically very weak interface response ir may be best recovered when the shallow layer exhibits low saturation we also use our programme to compute the seismoelectric response of a capillary fringe between a vadose sand overburden and a saturated sand half space our first modelling results suggest that the study of the seismoelectric ir may help to detect a sharp saturation contrast better than a smooth saturation transition in our example a saturation contrast of 50 per cent between a fully saturated sand half space and a partially saturated shallow sand layer yields a stronger ir than a stepwise decrease in saturation

the discovery of santorini minoan tephra in western turkey dispersal of volcanic ash from the violent bronze age minoan eruption of the santorini volcano in the southern aegean has been the subject of much research1 6 a sediment core taken from a small mountain lake in western turkey contains a layer of tephra from the minoan eruption the santorini origin is established by refractive index major glass chemistry and stratigraphic position the lake is located north of the recognized dispersal area for the tephra this deposit provides evidence for dispersal of the minoan tephra well to the northeast of santorini and implies that the west coast of asia minor must have experienced heavy tephra fallout from the bronze age eruption the minoan tephra has not previously been identified from sites in turkey

multiphase streaming potential in sandstones saturated with gas brine and oil brine during drainage and imbibition 1 we have measured the streaming potential in water wet sandstones during both drainage and imbibition and demonstrate that it behaves differently in oil brine and gas brine displacements during drainage the streaming potential remains significantly greater than zero at the irreducible water saturation in oil brine displacements but falls to zero in gas brine displacements during imbibition the streaming potential at partial saturation in oil brine displacements exceeds that measured at saturation but not in gas brine experiments our results have application to streaming potential measurements in the vadose zone hydrocarbon reservoirs contaminated aquifers and during co2 sequestration

impulsive alluviation during early holocene strengthened monsoons central nepal himalaya the steep walled bedrock gorges of the greater himalayan rivers currently lack significant stored sediment suggesting that fluvial erosion and transport capacity outpace the supply of sediment from adjacent hillsides despite this appearance of sustained downcutting such rivers can become choked with sediments and aggrade during intervals of higher precipitation cosmogenic dating 10 be and 26 al of fluvially carved bedrock surfaces indicates that sediment at least 80 m thick filled the marsyandi river valley in central nepal during a time of strengthened early holocene monsoons despite threefold differences in height 43 124 m above the modern river these fluvial surfaces display strikingly similar cosmogenic exposure ages clustering around 7 6 1 ka we speculate that enhanced monsoonal precipitation increased pore pressure and the frequency of landsliding thereby generating a pulse of hillslope derived sediment that temporarily overwhelmed this alpine fluvial system s transport capacity after the easily liberated material was exhausted ca 7 ka the hillslope flux dropped and the river incised through the aggraded alluvium it concurrently eroded adjacent rock walls thereby removing previously accumulated 10 be and 26 al and resetting the cosmogenic clock in the bedrock unlike previous studies these exposure ages cannot be used to derive river incision rates instead they record a coupled fluvial hillslope response to climate change

on the origin and interpretation of self potential anomalies the renewed interest in the self potential method of exploration for mineral deposits gives an understanding of the self potential mechanism new importance the cause of sp anomalies in general lies in the interference between simultaneously occurring nonequilibrium phenomena however theories of the mechanism of mineral sp anomalies generally relate the sp anomaly to the equilibrium potential of the chemical reaction supposed to occur on the ore body surface in this paper i reformulate these equilibrium mechanisms in terms of nonequilibrium thermodynamics the result is that the sp anomaly depends not on the equilibrium potential alone but also on the potential resulting from current transferred across the ore body electrolyte interface it is not possible to calculate the overpotential theoretically because of the number of complicating factors and experimental data are not available this does not imply that sp data are uninterpretable quantitatively sp data may be interpreted similarly to other potential field data

reply to comment on dependence of shear wave seismoelectrics on soil textures a numerical study in the vadose zone by f i zyserman l b monachesi and l jouniaux by revil a

permeability dependence of streaming potential coefficient in porous media in theory the streaming potential coefficient depends not only on the zeta potential but also on the permeability of the rocks that partially determines the surface conductivity of the rocks however in practice it is hard to show the permeability dependence of streaming potential coefficients because of the variation of zeta potential from sample to sample to study permeability dependence of streaming potential including the effects of the variation of the zeta potential and surface conductance due to the difference in mineral compositions between samples we perform measurements on 12 consolidated samples including natural and artificial samples saturated with 7 different nacl solutions to determine the streaming potential coefficients the results have shown that the streaming potential coefficients strongly depend on the permeability of the samples for low fluid conductivity when the fluid conductivity is larger than than 0 50 s m for the natural samples or 0 25 s m for the artificial ceramic samples the streaming potential coefficient is independent of permeability this behavior is quantitatively explained by a theoretical model

geomorphology deceptively old alpine gorges the timing and origins of alpine gorge formation are controversial a high resolution analysis of the inner gorges of the swiss alps suggests that these landforms were carved over successive interglacial periods and survived the intervening glaciations

exhumation controlled by transcurrent tectonics the argentera mercantour massif sw alps new apatite fission track aft and u th he ages from the argentera mercantour external crystalline massif of the sw alps document an exhumation history along transcurrent dextral faults significant aft age differences across the strikes of the main faults have been obtained from the ne 12 9 ma to the sw 5 2 ma and are linked to vertical uplifts along these right lateral transpressional structures such segmentation is not observed in ahe ages ahe ages have preserved younger ages 4 5 ma on the eastern hangingwall side of the high durance extensional system such an exhumation history is interpreted to result from a transition of transpressional to transtensional regimes at 8 5 ma during continuing adria europe convergence these data show that recent extensional deformation in the sw alps can be related to the development of a transtensional domain in the ubaye embrunais depression linked to ongoing strike slip deformation along the argentera mercantour

influence of water pressure dynamics and fluid flow on the streaming potential response for unsaturated conditions streaming potentials are produced by electrokinetic effects in relation to fluid flow and are used for geophysical prospecting the aim of this study is to model streaming potential measurements for unsaturated conditions using an empirical approach a conceptual model is applied to streaming potential measurements obtained from two drainage experiments in sand the streaming potential data presented here show a non monotonous behaviour with increasing water saturation following a pattern that cannot be predicted by existing models a model involving quasi static and dynamic components is proposed to reproduce the streaming potential measurements the dynamic component is based on the first time derivative of the driving pore pressure the influence of this component is investigated with respect to fluid velocity which is very different between the two experiments the results demonstrate that the dynamic component is predominant at the onset of drainage in experiments with the slowest water flow on the other hand its influence appears to vanish with increasing drainage velocity our results suggest that fluid flow and water distribution at the pore scale have an important influence on the streaming potential response for unsaturated conditions we propose to explain this specific streaming potential response in terms of the behaviour of both rock water interface and water air interfaces created during desaturation processes the water air interfaces are negatively charged as also observed in the case of water rock interfaces both the surface area and the flow velocity across these interfaces are thought to contribute to the non monotonous behaviour of the streaming potential coefficient as well as the variations in its amplitude the non monotonous behaviour of air water interfaces created during the flow was highlighted as it was measured and modelled by studies published in the literature the streaming potential coefficient can increase to about 10 to 40 when water saturation decreases such an increase is possible if the amount of water air interfaces is increased in sufficient amount which can be the case

dating bedrock gorge incision in the french western alps ecrins pelvoux massif using cosmogenic 10be terra nova 22 18 25 2010 abstract we report in situ produced 10be data from the gorge du diable french western alps to date and quantify bedrock gorge incision into a glacial hanging valley we sampled gorge sidewalls and the active channel bed to derive both long term and present day incision rates 10be ages of sidewall profiles reveal rapid incision through the late holocene ca 5 ka at rates ranging from 6 5 to 13 mm yr 1 present day incision rates are significantly lower and vary from 0 5 to 3 mm yr 1 within the gorge our data imply either delayed initiation of gorge incision after final ice retreat from internal alpine valleys at ca 12 ka or post glacial surface reburial of the gorge our results suggest that fluvial incision rates 1 cm yr 1 into crystalline bedrock may be encountered in transient landscape features induced by glacial interglacial transitions

the respiratory health hazards of volcanic ash a review for volcanic risk mitigation studies of the respiratory health effects of different types of volcanic ash have been undertaken only in the last 40 years and mostly since the eruption of mt st helens in 1980 this review of all published clinical epidemiological and toxicological studies and other work known to the authors up to and including 2005 highlights the sparseness of studies on acute health effects after eruptions and the complexity of evaluating the long term health risk silicosis non specific pneumoconiosis and chronic obstructive pulmonary disease in populations from prolonged exposure to ash due to persistent eruptive activity the acute and chronic health effects of volcanic ash depend upon particle size particularly the proportion of respirable sized material mineralogical composition including the crystalline silica content and the physico chemical properties of the surfaces of the ash particles all of which vary between volcanoes and even eruptions of the same volcano but adequate information on these key characteristics is not reported for most eruptions the incidence of acute respiratory symptoms e g asthma bronchitis varies greatly after ashfalls from very few if any reported cases to population outbreaks of asthma the studies are inadequate for excluding increases in acute respiratory mortality after eruptions individuals with pre existing lung disease including asthma can be at increased risk of their symptoms being exacerbated after falls of fine ash a comprehensive risk assessment including toxicological studies to determine the long term risk of silicosis from chronic exposure to volcanic ash has been undertaken only in the eruptions of mt st helens 1980 usa and soufriere hills montserrat 1995 onwards in the soufriere hills eruption a long term silicosis hazard has been identified and sufficient exposure and toxicological information obtained to make a probabilistic risk assessment for the development of silicosis in outdoor workers and the general population a more systematic approach to multi disciplinary studies in future eruptions is recommended including establishing an archive of ash samples and a website containing health advice for the public together with scientific and medical study guidelines for volcanologists and health care workers

experimental measurements of seismoelectric signals in borehole models s u m m a r y an experimental system is built for the electrokinetic measurements with a small scaled seismoelectric detector and a high resolution digitizer 1 ms s 1 22 bits the acoustic and seismoelectric experiments are carried out in different boreholemodels at the high frequency of 90 khz in the laboratory all the localized seismoelectric signals that accompany compressional wave shear wave and stoneley wave are first clearly observed with a monopole source in sandstone boreholes that are saturated by tap water the amplitudes of these signals are measured in the range of 1 120 v which is useful for designing the seismoelectric logging instruments then the amplitude ratio of electric signal to acoustic pressure rep for each of the three waves is calculated and compared with the theoretical simulations based on the experimental data we find that seismoelectric logging signals as well as rep become stronger at the more permeable borehole model we also find that seismoelectric logging signals are more sensitive to permeability and porosity comparedwith acoustic logging signals therefore this study verifies the feasibility of seismoelectric well logging and further indicates that the seismoelectric logging technique might be a preferable method to estimate formation parameters in the field measurements

implications of sediment flux dependent river incision models for landscape evolution 1 developing a quantitative understanding of the factors that control the rate of river incision into bedrock is critical to studies of landscape evolution and the linkages between climate erosion and tectonics current models of long term river network incision differ significantly in their treatment of the role of sediment flux we analyze the implications of various sediment flux dependent incision models for large scale topography in an attempt 1 to identify quantifiable and diagnostic differences between models that could be detected from topographic data or from the transient responses of perturbed systems and 2 to explain the apparent ubiquity of mixed bedrock alluvial channels in active orogens although certain forms of the various models can be discarded as inconsistent with morphological data we find that the relative intrinsic concavity indices of detachment and transport limited systems defined herein largely dictate whether the various models can be tied to distinctive steady state morphologies preliminary data suggest that no such diagnostic differences may exist and other methods must be developed to test models accordingly we develop and explore differences in the scaling behavior of topographic relief and the extent of detachment versus transport limited channels as a function of rock uplift rate that may allow discrimination among various models further we explore potentially diagnostic differences in the rates and patterns of transient channel response to changes in rock uplift rate in addition to general differences between detachment and transport limited systems our analysis identifies an interesting hysteresis in landscape evolution hybrid channels at the threshold between detachment and transport limited conditions are expected to act as detachment limited systems in response to an increase in rock uplift rate or base level fall and as transport limited systems in response to a decrease in rock uplift rate especially during postorogenic topographic decline the analyses presented set the stage for field studies designed to test quantitatively the various river incision models that have been proposed