erosional and climatic effects on long term chemical weathering rates in granitic landscapes spanning diverse climate regimes abstract we used cosmogenic nuclide and geochemical mass balance methods to measure long term rates of chemical weathering and total denudation in granitic landscapes in diverse climatic regimes our 42 study sites encompass widely varying climatic and erosional regimes with mean annual temperatures ranging from 2 to 25 c average precipitation ranging from 22 to 420 cm year 1 and denudation rates ranging from 23 to 755 t km 2 year 1 long term chemical weathering rates range from 0 to 173 t km 2 year 1 in several cases exceeding the highest granitic weathering rates on record from previous work chemical weathering rates are highest at the sites with rapid denudation rates consistent with strong coupling between rates of chemical weathering and mineral supply from breakdown of rock a simple empirical relationship based on temperature precipitation and long term denudation rates explains 89 95 of the variation in long term weathering rates across our network of sites our analysis shows that for a given precipitation and temperature chemical weathering rates increase proportionally with fresh material supply rates we refer to this as supply limited weathering in which fresh material is chemically depleted to roughly the same degree regardless of its rate of supply from breakdown of rock the temperature sensitivity of chemical weathering rates is two to four times smaller than what one would expect from laboratory measurements of activation energies for feldspar weathering and previous inter comparisons of catchment mass balance data from the field our results suggest that climate change feedbacks between temperature and silicate weathering rates may be weaker than previously thought at least in actively eroding unglaciated terrain similar to our study sites to the extent that chemical weathering rates are supply limited in mountainous landscapes factors that regulate rates of mineral supply from erosion such as tectonic uplift may lead to significant fluctuations in global climate over the long term

erosion rates over millennial and decadal timescales at caspar creek and redwood creek northern california coast ranges comparing millennial scale denudation rates from cosmogenic nuclides with decadal scale sediment yields can shed light on erosional processes and on the effects of land use on sediment delivery to streams detailed measurements of sediment fluxes in the northern california coast ranges at caspar creek and redwood creek have provided estimates of physical erosion rates since 1963 and 1971 respectively we used cosmogenic 10 be to measure

evidence for muon induced production of 10be in near surface rocks from the congo distributions of 10be in vein quartz from a lateritic weathering profile from the congo provide evidence for significant in situ production of 10be by reactions other than neutron induced spallation after consideration of geomorphological and nuclear processes which might contribute to the observed depth variability we conclude that cosmic ray muon induced reactions are the most likely mechanism and that such reactions lead to 1 to 3 of 10be production at the surface this small muon induced component has only minor implications for the use of 10be for quantification of exposure histories of surficial rocks nevertheless the muogenic component has the potential to expand the utility of cosmogenic nuclides in examination of surficial processes overcoming some of the limitations associated with the use of the neutron produced component

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

a 14 000 year sediment yield record from western germany based on annually laminated lake sediments the reconstruction of sediment yield data for the catchment of lake holzmaar 205 8 ha in the eifel mountains western germany is based on high resolution geochemical and physical analyses of an absolutely dated sediment record this technique provides flux rates of allochthonous minerogenic deposition for the last 13 840 years the pleistocene holocene transition is characterized by instable soils and vegetation caused by adjustment of the catchment to interglacial climatic conditions these instabilities are the reason for elevated mean sediment yields in the catchment of 16 t km 2 yr 1 until 9800 cal bp during most of the holocene erosive processes are insignificant and sediment yields are very low 1 5 t km 2 yr 1 since humans cleared the forests for agriculture and early industrial purposes the natural environment has been disturbed and sediment yields increased to mean values of 14 t km 2 yr 1 during the last 2750 years comparisons of reconstructions from the eifel area with similar data from southern sweden and with measured data from lakes reservoirs and monitoring sites suggest that quantitative reconstructions based on lake holzmaar sediments may be regarded as reliable despite uncertainties related to the methods of reconstruction applied

denudation rates and a topography driven rainfall threshold in northern chile multiple cosmogenic nuclide data and sediment yield budgets abstract the quantification of geomorphic process rates on the outcrop and the orogen scale is important to describe accurately the interaction between the relative effects of erosion tectonics and climate on landscape evolution we report single and paired cosmogenic nuclide 10 be 26 al and 21 ne derived erosion rates and exposure ages on hillslope interfluves from the tectonically active western central andes that show a distinct spatial variation a positive correlation of erosion rates with elevation and present day rainfall rates is observed erosion rates at lower altitudes the hyperarid coastal cordillera and the western escarpment with the northern part of the atacama desert are extremely low and of the order of 10 100 cm my nominal exposure ages 1 6 my in contrast erosion rates at higher altitudes the semiarid western cordillera range up to 4600 cm my nominal exposure ages 0 02 0 1 my this latter average long term bedrock erosion rate record suggested to be coupled to an orographically controlled pattern of rainfall is also reflected in the pattern of denudation rates derived from a short term decadal record of limited sediment yield data specifically denudation rates calculated from sediment flux data are of a similar order of magnitude as erosion rates deduced from long lived cosmogenic nuclides from bedrock hillslope interfluves of the western cordillera nevertheless the production and the supply of sediment from the western andean slope are very limited analysis of multiple cosmogenic nuclides allows simultaneous determination of erosion rates and exposure ages but also reveals complex exposure histories of non bedrock samples such as boulders or amalgamated clast samples notably this study shows that saturation of nuclides usually assumed in studies where only a single nuclide is analyzed is rather the exception than the rule as revealed by erosion island plots constant erosion that started much later than the formation age of the rocks or episodic erosion by spalling can partially explain non steady state concentrations and more complicated exposure scenarios furthermore the use of multiple nuclides with different half lives allowed us to infer that no significant variations in long term erosion rates have occurred and that at the western escarpment erosion rates have been low and constant for most of the late neogene nevertheless the time intervals necessary to reach steady state concentrations for cosmogenic nuclides can be quite different from those needed for landscapes to reach steady state

erratum to the control mechanisms of erosion and weathering at basin scale from cosmogenic nuclides in river sediment earth planet sci lett 237 2005 462 479

large scale erosion rates from in situ produced cosmogenic nuclides in european river sediments abstract we have calculated long term erosion rates of 20 100 mm kyr from quartz contained 10be in the bedload of middle european rivers for catchments ranging from 102 to 105 km2 these rates average over 10 40 kyr and agree broadly with rock uplift incision and exhumation rates historic soil erosion rates and erosion rates calculated from the measured sediment loads of the same rivers moreover our new erosion rate estimates correlate well with lithology and relief however in the regen neckar loire and meuse catchments cosmogenic nuclide derived erosion rates are consistently 1 5 4 times greater than the equivalent rates derived from measured river loads this may be due to the systematic under representation of high magnitude low frequency transport events in the gauging records which cover less than a century alternatively the discrepancy may derive from spatially non uniform erosion and preferential tapping of deeper sections of the irradiation profile a third explanation relates the high cosmogenic nuclide derived erosion rates to inheritance of an elevated pleistocene erosion signal uncertainties associated with the cosmogenic nuclide derived erosion rate estimates are not greater than the potential errors in conventional estimates therefore the cosmogenic nuclide approach is an effective tool for rapid catchment wide assessment of time integrated rates of bedrock weathering and erosion and we anticipate its fruitful application to the quaternary sedimentary record

sediment output and effective discharge in two small high mountain catchments in the bavarian alps germany abstract sediment output solid and dissolved load from two small alpine rivers partnach and lahnenwiesgraben in the bavarian alps was measured during three summer field seasons from 2001 2003 there is high spatial variability of sediment output between the catchments and a high temporal variability between observation periods sediment transport in the partnach river reintal is dominated by solute load whereas the lahnenwiesgraben river transports a much greater proportion of solid load this difference can mainly be explained by the different lithologies of the systems the reintal catchment is dominated by massive triassic limestone in the lahnenwiesgraben catchment in addition to limestones unconsolidated rocks marls and mudstone layers are significant furthermore large rockslide dams in the partnach valley isolate large parts of the reintal catchment from solid load output the components of fluvial sediment transport were where possible calculated by using flow duration curves and rating curve techniques in the lahnenwiesgraben event specific rating curves were used to determine suspended load on the broad database of 55 measured flood events in the lahnenwiesgraben a good correlation r pearson 0 9 between event peak discharge and suspended load of the event was established effective discharge was calculated for the different types of sediment load solid and dissolved and total load in the reintal effective discharge for total load is found in low flow classes close to mean discharge because sediment output is dominated by dissolved load which has its maximum efficiency at low and moderate discharges in the lahnenwiesgraben most work is done by discharges much higher than mean discharge during extreme individual flood events

temporal distribution of suspended sediment transport in a mediterranean basin the lower tordera ne spain abstract suspended sediment dynamics are still imperfectly understood especially in areas of mediterranean climate with strong seasonal contrasts where few studies have been conducted the aim of this study is to analyze the variability in the suspended sediment load at different temporal scales within flood variability monthly seasonal and annual in the tordera river 894 km 2 located in northeastern spain suspended sediment samples were obtained during base flows q 3 5 m 3 s 1 and flood events q 3 5 m 3 s 1 the analysis of the variability in the suspended sediment is structured in two consecutive steps i the construction of statistical relations between suspended sediment concentrations c and discharge q and ii the application of those relations to assess the suspended sediment yield the results show that in a single event the sediment peak generally precedes the peak discharge following a clockwise hysteretic loop furthermore it was observed that the reduction in the suspended sediment concentrations in a sequence of events can be mainly associated with a phenomenon of sediment exhaustion the total amount of suspended sediment transported during a single flood is thus related to its duration and time during the year as well as to its magnitude at a seasonal scale the export of suspended sediment takes place in two phases i sediment preparation and ii sediment transfer and exhaustion during the latter phase the exhaustion of the sediment load is primarily related to the sequence of flood events at the annual scale the results show high inter annual variability according to the number of floods recorded yearly since almost all the suspended load is transported during those events

late and post variscan cooling and exhumation history of the northern rhenish massif and the southern ruhr basin new constraints from fission track analysis apatite fission track analyses were carried out on outcrop and core samples from the rhenish massif and the carboniferous ruhr basin germany in order to study the late and post variscan thermal and exhumation history apatite fission track ages range from 291 15 ma lower permian to 136 7 ma lower cretaceous and mean track lengths vary between 11 6 m and 13 9 m mostly displaying unimodal distributions with narrow standard deviations all apatite fission track ages are younger than the corresponding sample stratigraphic age indicating substantial post depositional annealing of the apatite fission tracks this agrees with results from maturity modelling which indicates 3500 7000 m eroded devonian and carboniferous sedimentary cover numerical modelling of apatite fission track data predicts onset of exhumation and cooling not earlier than 320 ma in the rhenish massif and 300 ma in the ruhr basin generally followed by late carboniferous triassic cooling to below 50 60 c rapid late variscan cooling was followed by moderate mesozoic cooling rates of 0 1 0 2 c ma converting into denudation rates of 1 mm a assuming a stable geothermal gradient of 30 c km modelling results also give evidence for some late triassic and early jurassic heating and or burial which is supported by sedimentary rocks of the same age preserved at the rim of the lower rhine basin and in the subsurface of the central and northern ruhr basin cenozoic exhumation and cooling of the rhenish massif is interpreted as an isostatic response to former erosion and major base level fall caused by the subsidence in the lower rhine basin

on steady states in mountain belts the dynamic system of tectonics and erosion contains important feedback mechanisms such that orogenic systems tend toward a steady state this concept is often invoked but the nature of the steady state is commonly not specified we identify four types of steady state that characterize the orogenic system and illustrate these cases by using numerical model results and natural examples these types are 1 flux steady state 2 topographic steady state 3 thermal steady state and 4 exhumational steady state they refer to the erosional flux the topography the subsurface temperature field and the spatial pattern of cooling ages respectively models suggest that the topography will reach a steady mean form at the scale of an orogenic belt but perfect topographic steady state is unlikely to be achieved at shorter length scales thermal steady state is a precondition for exhumational steady state and in the case of temperature dependent deformation topographic steady state exhumational steady state is characterized by reset age zones spatially nested according to closure temperature as illustrated in natural systems from new zealand the cascadia accretionary margin and taiwan

10be and 26al production rates deduced from an instantaneous event within the dendro calibration curve the landslide of kofels otz valley austria surface exposure dating requires the knowledge of cosmogenic nuclide production rates when determining time integrated production rates the exposure ages of the calibration samples need to be accurately known the landslide of kofels austria is very well suited for this purpose it is the largest landslide in the crystalline alps of austria dating back to 7800 100 years bc ams 14c dating of buried wood which is well within the 14c dendro calibration curve exposed quartz veins were sampled from the tops of large boulders from the toe of the landslide for analysis of 10be and 26al to calculate sea level high geomagnetic latitude 60 open sky radionuclide production rates corrections were applied for altitude and latitude for shielding by surrounding mountains for sample geometry vegetation and snow cover and for sample thickness the production rates for an exposure age of 10 000 years are 5 75 0 24 10be atoms yr g sio2 and 37 4 1 9 26al atoms yr g sio2 a 26al 10be ratio of 6 52 0 43 can be calculated the influence of the geomagnetic field on these production rates has been estimated using two different geomagnetic field records our production rates should be a good approximation for the use of surface exposure dating between about 5000 and 13 000 years bp

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

suspended sediment load during floods in a small stream of the dolomites northeastern italy abstract suspended sediment load was analyzed in a small high gradient stream of the eastern italian alps which was instrumented to measure discharge and sediment transport the ratio of suspended to total sediment yield and the relations between sediment concentration and water discharge were analyzed for seven floods which occurred from 1991 to 1996 in summer and autumn from june to october different patterns of hysteresis in the relation between suspended sediment and discharge were related to types and locations of active sediment sources the within storm variation of particle size of suspended sediment during a major flood indicates a coarsening of transported material for increasing discharge an analysis of grain size has shown that erosion areas on hillslopes were the main sources of suspended load

the effect of land plants on weathering rates of silicate minerals abstract land plants and their associated microbiota directly affect silicate mineral weathering in several ways by generation of chelating ligands by modifying ph through production of co2 or organic acids and by altering the physical properties of a soil particularly the exposed surface areas of minerals and the residence time of water in laboratory experiments far from equilibrium 1 mm oxalate a strong chelator of al has a negligible effect on the dissolution rate of alkali feldspars but some effect on calcic feldspars and olivine by analogy to oxalate the overall effect of organic ligands on the weathering rate of silicate minerals in nature is likely to be small except perhaps in microenvironments adjacent to roots and fungal hyphae the effect of ph on silicate mineral dissolution rate depends on ph below ph 4 5 the rate increases with decreasing ph in the circumneutral region the rate is ph independent and at ph values above around 8 the rate increases with increasing ph vegetation should thus cause an increase in weathering rate through the ph effect only where the ph is below 4 5 as an overall generalization the effect of plants on weathering rate through changes in soil solution chemistry is probably small for granitic rocks it may be greater for more mafic rocks it is the release of ca and mg from mafic rocks that has the greatest influence on the global co2 budget the effect of changes in soil physical properties on weathering rate can be major by binding fine particles plants can greatly increase weathering rates in areas of high physical erosion where erosion rates are lower the effect of plants is less clear on long timescales plants may decrease chemical weathering by binding secondary products and isolating unweathered minerals from meteoric water a major unknown in estimating the effect of the advent of land plants on weathering rates is the nature thickness particle size distribution permeability of the regolith on the pre silurian continents the indirect effect of vegetation through changing the regional distribution of precipitation may be as important as the direct effects

geochemistry of dissolved and suspended loads of the seine river france anthropogenic impact carbonate and silicate weathering this study focuses on the chemistry of the seine river system one of the major rivers in europe and constitutes the first geochemical investigation of both suspended and dissolved loads of this river the seine river drains a typical mesozoic cenozoic sedimentary basin the paris basin constituted of limestones mixed or interbedded with terrigenous sediments derived from the paleoreliefs bordering the mesozoic and cenozoic seas in the context of quantifying the global influence of carbonate and silicate weathering on atmospheric co2 consumption the seine river offers the possibility of examining weathering rates in a flat sedimentary environment under temperate climatic conditions one of the major problems associated with the seine river as with many temperate rivers is pollution we propose in this paper 2 approaches in order to correct the dissolved load of the seine river for anthropogenic inputs and to calculate weathering rates of carbonates and silicates the first uses the dissolved load of rivers and tries to allocate the different solutes to different sources a mixing model based on elemental ratios is established and solved by an inversion technique the second approach consists in using the suspended load geochemistry under steady state conditions we show that the geochemistry of suspended sediments makes it possible to estimate the amount of solutes released during the chemical weathering of silicates and thus to calculate weathering rates of silicates the total dissolved load of the seine river at paris can be decomposed into 2 of solutes derived from natural atmospheric sources 7 derived from anthropogenic atmospheric sources 6 derived from agriculture 3 derived from communal inputs and 82 of solutes derived from rock weathering during high floods the contribution of atmospheric and agriculture inputs predominates the weathering rate of carbonates is estimated to be 48 t km2 yr 25 mm 1000 yr only 10 of carbonates are transported in a solid form the rest being transported in solution co2 consumption by carbonate weathering approaches 400 103 mol km2 yr in the seine river at paris about 2 3 mg l of dissolved cations are found to originate from the chemical weathering of silicates by taking dissolved silica into accounts the total dissolved load derived from silicate weathering is about 6 7 mg l this value is minimal because biological uptake of silica probably occur in the seine river the chemical weathering rate of aluminosilicates is estimated to be 2 t km2 yr the ratio of physical over chemical weathering of silicates range between 1 and 3 and the total chemical and physical erosion rates of sedimentary silicates are about 2 3 mm kyr the co2 consumption by silicate weathering 15 24 103 mol km2 yr and is independent of dissolved silica concentration silicate consumption is thus 20 times less than carbonate consumption in the paris basin compared to the neighboring granitic areas the sedimentary region drained by the seine river has 2 to 3 times lower co2 consumption rates we attribute this difference to the cation depleted nature of the seine basin aluminosilicates which are of sedimentary origin at a world scale the chemical denudation rates found for the seine basin are very low and comparable to those given for tropical lowland rivers draining silicates such as the rivers of the congo and amazon basins in spite of huge climatic differences we attribute this similarity to the low mechanical denudation that characterizes these two types of regions

representation of the scandinavia greenland pattern and its relationship with the polar vortex in s2s forecast models the strength of the stratospheric polar vortex is a key contributor to subseasonal prediction during boreal winter anomalously weak polar vortex events can be induced by enhanced vertically propagating rossby waves from the troposphere driven by blocking and wave breaking here we analyse a tropospheric pattern the scandinavia greenland s g pattern associated with both processes the s g pattern is defined as the second empirical orthogonal function eof of mean sea level pressure in the northeast atlantic the first eof is a zonal pattern resembling the north atlantic oscillation we show that the s g pattern is associated with a transient amplification of planetary wavenumber2 and meridional eddy heat flux followed by the onset of a weakened polar vortex which persists for the next 2 months we then analyse 10 different models from the s2s database finding that while all models represent the structure of the s g pattern well some models have a zonal bias with more than the observed variability in their first eof and accordingly less in their second eof this bias is largest in models with the lowest resolution skill in predicting the s g pattern is not high beyond week 2 in any model in contrast to the zonal pattern we find that the relationship between the s g pattern and enhanced eddy heat flux and a weakened polar vortex is initially well represented but significantly decays with lead time in most s2s models our results motivate improved representation of the s g pattern and its stratospheric response at longer lead times for improved subseasonal prediction of the stratospheric polar vortex

relation between rock uplift and denudation from cosmogenic nuclides in river sediment in the central alps of switzerland 1 a north south traverse through the swiss central alps reveals that denudation rates correlate with recent rock uplift rates in both magnitude and spatial distribution this result emerges from a study of in situ produced cosmogenic 10be in riverborne quartz in central alpine catchments as a prerequisite we took care to investigate the potential influence of shielding from cosmic rays due to snow glaciers and topographic obstructions to calculate a possible memory from last glacial maximum lgm glaciation and to identify a watershed size that is appropriate for systematic sampling mean denudation rates are 0 27 0 14 mm a for the alpine foreland and 0 9 0 3 mm a for the crystalline central alps the measured cosmogenic nuclide derived denudation rates are in good agreement with post lgm lake infill rates and are about twice as high as denudation rates from apatite fission track ages that record denudation from 9 to 5 ma in general denudation rates are high in areas of high topography and high crustal thickness the similarity in the spatial distribution and magnitude of denudation rates and those of rock uplift rates can be interpreted in several ways 1 postglacial rebound or climate change has introduced a transient change in which both uplift and denudation follow each other with a short lag time 2 the amplitude of glacial to interglacial changes in both is small and is contained in the scatter of the data 3 both are driven by ongoing convergence where their similarity might hint at some form of long term quasi steady state or 4 enhanced continuous quaternary erosion and isostatic compensation of the mass removed accounts for the distribution of present day rock uplift

erosion rates on different timescales derived from cosmogenic 10 be and river loads implications for landscape evolution in the rhenish massif germany we determined erosion rates on timescales of 101 104 years for two catchments in the northeastern rhenish massif in order to unravel the quaternary landscape evolution in a variscan mountain range typical of central europe spatially averaged erosion rates derived from in situ produced 10be concentrations in stream sediment of the aabach and mohne watersheds range from 47 6 to 65 14 mm ka and integrate over the last 9 13 ka these erosion rates are similar to local rates of river incision and rock uplift in the quaternary and to average denudation rates since the mesozoic derived from fission track data this suggests that rock uplift is balanced by denudation i e the landscape is in a steady state short term erosion rates were derived from suspended and dissolved river loads subsequent to 1 correcting for atmospheric and anthropogenic inputs 2 establishing calibration curves that relate the amount of suspended load to discharge and 3 estimating the amount of bedload the resulting solid mass fluxes suspended and bedload agree with those derived from the sediment volume trapped in three reservoirs however resulting geogenic short term erosion rates range from 9 to 25 mm ka and are only about one third of the rates derived from 10be model simulations in combination with published sediment yield data suggest that this discrepancy is caused by at least three factors 1 phases with higher precipitation and or lower evapotranspiration 2 rare flood events not captured in the short term records and 3 prolonged periods of climatic deterioration with increased erosion and sediment transport on hillslopes

dynamic equilibrium among erosion river incision and coastal uplift in the northern and central apennines italy erosion river incision and uplift rates in the northern and central apennines italy since 0 9 ma are determined from new cosmogenic nuclide data beryllium 10 concentrations in modern and middle pleistocene sediments indicate erosion rates from 0 20 to 0 58 mm yr these rates are similar to estimates of sediment yield 0 12 0 44 mm yr river incision 0 35 mm yr and uplift 0 01 1 0 mm yr rates inferred from other methods that integrate landscape process rates since the early pleistocene these rates of landscape change are significantly lower than long term exhumation rates of 1 2 mm yr since ca 4 5 ma inferred from thermochronometry collectively these data suggest that hillslope erosion and river incision rates in the northern and central apennines have balanced local uplift rates for 1 my but that exhumation rates have slowed significantly since emergence of the mountain chain in the pliocene this condition of dynamic equilibrium was potentially achieved within ca 3 ma similar to some model predictions of hillslope and fluvial system adjustment

increase of human over natural erosion rates in tropical highlands constrained by cosmogenic nuclides we quantify the difference between the human caused sediment yield and the natural rates of soil production and bedrock erosion in a now largely deforested tropical highland the present day rate of soil loss in the upper mahaweli catchment sri lanka is calculated by using suspended river load fluxes these data provide spatially averaged sediment yields of 130 2100 t km 2 yr 1 local rates of soil loss from agricultural plots on hillslopes are as high as 7000 t km 2 yr 1 by comparison natural rates of sediment generation as determined by measuring cosmogenic 1 0 be in quartz from sediments and soils are only 13 30 t km 2 yr 1 the natural rates presented here provide a benchmark against which recent erosion rates determined by various sediment gauging techniques can be referenced in the sri lankan highlands these results suggest that soil is now being lost 10 100 times faster from agriculturally utilized areas than it is being produced

mountain erosion over 10 yr 10 k y and 10 m y time scales we used cosmogenic 10 be to measure erosion rates over 10 k y time scales at 32 idaho mountain catchments ranging from small experimental watersheds 0 2 km 2 t o large river basins 35 000 km 2 these long term sediment yields are on average 17 times higher than stream sediment fluxes measured over 10 84 yr but are consistent with 10 m y erosion rates measured by apatite fission tracks our results imply that conventional sediment yield measurements even those made over decades can greatly underestimate long term average rates of sediment delivery and thus overestimate the life spans of engineered reservoirs our observations also suggest that sediment delivery from mountainous terrain is extremely episodic sporadically subjecting mountain stream ecosystems to extensive disturbance

martian perched craters and large ejecta volume evidence for episodes of deflation in the northern lowlands the northern lowland plains such as those found in acidalia and utopia planitia have high percentages of impact craters with fluidized ejecta in both regions the analysis of crater geometry from mars orbiter laser altimeter mola data has revealed large ejecta volumes some exceeding the volume of excavation moreover some of the crater cavities and fluidized ejecta blankets of these craters are topographically perched above the surrounding plains these perched craters are concentrated between 40 and 70 n in the northern plains the atypical high volumes of the ejecta and the perched craters suggest that the northern lowlands have experienced one or more episodes of resurfacing that involved deposition and erosion the removal of material most likely caused by the sublimation of ice in the materials and their subsequent erosion and transport by the wind is more rapid on the plains than on the ejecta blankets the thermal inertia difference between the ejecta and the surrounding plains suggests that ejecta characterized by a lower thermal inertia protect the underneath terrain from sublimation this results in a decreased elevation of the plains relative to the ejecta blankets sublimation and eolian erosion can be particularly high during periods of high obliquity

denudation rates determined from the accumulation of in situ produced 10be in the luquillo experimental forest puerto rico we present a simple method for estimation of long term mean denudation rates using in situ produced cosmogenic 10be in fluvial sediments procedures are discussed to account for the effects of soil bioturbation mass wasting and attenuation of cosmic rays by biomass and by local topography our analyses of 10be in quartz from bedrock outcrops soils mass wasting sites and riverine sediment from the icacos river basin in the luquillo experimental forest puerto rico are used to characterize denudation for major landform elements in that basin the 10be concentration of a discharge weighted average of size classes of river sediment corresponds to a long term average denudation of 43 m ma 1 consistent with mass balance results

spatially averaged long term erosion rates measured from in situ produced cosmogenic nuclides in alluvial sediment spatially averaged erosion rates of small catchments can be accurately inferred from the concentrations of cosmogenic nuclides in stream sediment here we test this technique at two catchments by comparing erosion rates inferred from cosmogenic nuclides with rates of alluvial fan deposition over the past 16 000 years these two independent estimates agree within one standard error demonstrating that cosmogenic nuclide signatures of stream sediment can be used to measure spatially averaged long term erosion rates using this technique we show that long term erosion rates are an exponential function of average hillslope gradient at these sites

natural controls of fluvial denudation rates in major world drainage basins we present a new compilation of estimates of modern rates of mechanical and chemical denudation for externally drained basins exceeding 5 105 km2 in area these estimates are based on sediment and solute load data selected in order to represent natural rates as far as possible chemical denudation rates have been calculated by deducting the nondenudational component of solute load mechanical denudation rates range from 1 mm kyr 1 for the st lawrence and dnepr basins to 670 mm kyr 1 for the brahmaputra basin chemical denudation rates vary from 1 mm kyr 1 kolyma niger nile and rio grande basins to 27 mm kyr 1 chiang jiang basin the kolyma basin has the lowest 4 mm kyr 1 and the brahmaputra basin the highest overall rate of denudation 688 mm kyr 1 relationships between denudation rates and a range of morphometric hydrologic and climatic variables are investigated through correlation and regression analysis morphometric variables such as mean local relief are accurately calculated for large basins for the first time by using the national geophysical data center 10 minute topographic database variables expressing basin relief characteristics and runoff are found to be most strongly associated with both mechanical and chemical denudation rates with more than 60 of the variance in total denudation being accounted for by basin relief ratio and runoff basin area runoff variability and mean temperature however are only weakly associated with rates of denudation although direct comparisons cannot be made it appears that rates of basin denudation derived from present day mass flux estimates are not overall significantly different from estimates of long term rates based on sediment volume and thermochronologic data it therefore appears that the key factors identified as controlling denudation rates here are also applicable to the geological time spans relevant to the interaction between tectonic and denudational processes

estimating rates of denudation using cosmogenic isotope abundances in sediment we propose as a testable hypothesis a basin scale approach for interpreting the abundance of in situ produced cosmogenic isotopes an approach which considers explicitly both the isotope and sediment flux through a drainage basin unlike most existing models which are appropriate for evaluating in situ produced cosmogenic isotope abundance at discrete points on earth s surface our model is designed for interpreting isotope abundance in sediment because sediment is a mixture of materials in favourable cases derived from throughout a drainage basin we suggest that measured isotope abundances may reflect spatially averaged rates of erosion we investigate the assumptions and behaviour of our model and conclude that it could provide geomorphologists with a relatively simple means by which to constrain the rate of landscape evolution if a basin is in isotopic steady state and if sampled sediments are well mixed

strong tectonic and weak climatic control of long term chemical weathering rates the relationships among climate physical erosion and chemical weathering have remained uncertain because long term chemical weathering rates have been difficult to measure here we show that long term chemical weathering rates can be measured by combining physical erosion rates inferred from cosmogenic nuclides with dissolution losses inferred from the rock to soil enrichment of insoluble elements we used this method to measure chemical weathering rates across 22 mountainous granitic catchments that span a wide range of erosion rates and climates chemical weathering rates correlate strongly with physical erosion rates but only weakly with climate implying that by regulating erosion rates tectonic uplift may significantly accelerate chemical weathering rates in granitic landscapes

sediment yield during late glacial and holocene periods in the lac chambon watershed massif central france a sediment budget for the late glacial and holocene periods was calculated for the lac chambon watershed which is located in a formerly glaciated temperate crystalline mountain area it appears that over 15 500 years 1 69 per cent of eroded particles have been displaced by gravity processes and then stored within the watershed compared to 31 per cent that have been displaced by running water and evacuated outward 2 the mean mechanical erosion due to gravity processes on the slopes amounted to 16 1 6 m and only developed on a quarter of the watershed surface whereas the mean mechanical erosion due to running water amounted 1 24 0 37 m and involved the whole watershed surface the mean sediment yields due to gravity processes on slopes were 2300 1360 1770 960 and 380 100 m 3 km 3 a 1 respectively for basalts and basic and acidic trachyandesites values of sediment yield due to running water were 49 15 120 36 and 79 24 m 3 km 2 a 1 respectively during the bolling allerod the younger dryas and the pre boreal boreal periods they were 56 17 and 166 50 m 3 km 2 a 1 during the sub atlantic period before and after 1360 a bp respectively these values reflect variations in the natural environment and the impact of human induced deforestation 1997 by john wiley sons ltd

lithology landscape dissection and glaciation controls on catchment erosion as determined by cosmogenic nuclides in river sediment the wutach gorge black forest cosmogenic nuclides measured in quartz from recent river bedload provide a novel tool to quantify catchment wide erosion rates at geologically meaningful time scales here we present an analysis of the geomorphological evolution of the 350 km2 wutach catchment in the uplands of the south west german black forest the robustness of the method is demonstrated by the fact that although the area was affected by river capture at 18 kyr bp the formed gorge is so narrow that spatially averaged erosion rates were not resolvably perturbed however because cosmogenic nuclides preserve an erosion memory of several thousand years the only perturbation introduced was detected in the minor areas that have been subject to the last maximum glaciation in unglaciated areas an important relationship between lithology and erosion can by quantified sandstone lithologies erode at 12 18 mm kyr 1 granite lithologies at 35 47 mm kyr 1 and limestone lithologies as deduced from river load gauging at 70 90 mm kyr 1