geology and geomorphology control suspended sediment yield and modulate increases following timber harvest in temperate headwater streams abstract suspended sediment transport is an important contributor to ecologic and geomorphic functions of streams however it is challenging to generalize predictions of sediment yield because it is influenced by many factors in this study we quantified the relevance of natural controls e g geology catchment physiography on suspended sediment yield ssy in headwater streams managed for timber harvest we collected and analyzed six years of data from 10 sites five headwater sub catchments and five watershed outlets in the trask river watershed western oregon united states we used generalized least squares regression models to investigate how the parameters of the ssy rating curve varied as a function of catchment setting and whether the setting modulated the ssy response to forest harvesting results indicated that the highest intercepts of the power relation between unit discharge and ssy were associated with sites underlain primarily by friable rocks e g sedimentary formations the greatest increases in ssy after forest harvesting up to an order of magnitude also occurred at sites underlain by the more friable lithologies in contrast basins underlain by resistant lithologies intrusive rocks had lower ssy and were more resilient to management related increases in ssy as such the impact of forest management activities e g use of forested buffers building of new roads on the variability in ssy was primarily contingent on catchment lithology sites with higher ssy or harvest related increases in ssy also generally had a lower mean elevation and slope b greater landscape roughness and c lower sediment connectivity we used principal component analysis pca to further explore the relationship between ssy and several basin physiographic variables the pca clearly separated sites underlain by friable geologic units from those underlain by resistant lithologies results are consistent with greater rates of weathering and supply of sediment to headwater streams in catchments with more friable lithologies and limited sediment supply in catchments underlain by resistant lithologies we hypothesize that a similar framework may aid in predicting the overall ssy of a catchment as well as its susceptibility to increases in ssy following forest harvesting

modeling the tor dotted crests bedrock edges and parabolic profiles of high alpine surfaces of the wind river range wyoming abstract broad low curvature surfaces common to many alpine landscapes and particularly well expressed in the laramide ranges of the western usa appear to be roughly in steady state with respect to the current surface processes uniform thin order 1 m regolith covers the crystalline bedrock with the exception of occasional tors at ridgecrests the surfaces are commonly edged by bedrock lips at the tops of cliffs that bound the intervening glacial troughs regolith production is low order 10 m year on bare bedrock and reaches a maximum under tens of centimeters of regolith all of these characteristics may be accounted for with a numerical model that is faithful to the periglacial surface processes presently operating on these surfaces hillslope transport is modeled assuming the dominant process is frost creep transport efficiency depends linearly upon local slope and appropriately vanishes in the absence of regolith frost frequency scales the rate of motion while the ratio of frost penetration depth to regolith thickness dictates the degree to which the process is curtailed by available regolith initial conditions include initial mean slope and bedrock roughness and a uniform regolith cover boundary conditions are imposed by dictating that the edges of the calculation space be lowered at a rate appropriate for glacial incision broad convex surfaces emerge over time scales of order 1 million years all surfaces rapidly decouple from the bounding glacial troughs as the high negative curvature at the edges disallows accumulation of regolith these bedrock edges lower at a few microns per year while the troughs lower at many times this rate as the bedrock edges therefore serve as the effective boundary condition for the remaining surface the surfaces operate independently of both lowering and widening of the glacial troughs for a reasonable set of transport and weathering rates the final steady state landscape is sensitive to the initial condition in particular the steeper the initial landscape the more likely tors are to develop as the high curvature disallows accumulation of regolith these tors in turn limit the lowering rate of the crest and the landscape retains significant local relief low relief initial conditions more likely lead to parabolic surfaces that lack tors that tors are more likely on the crests reflects the high initial curvature at the crest tors on the side slopes are eliminated the present high surfaces in the laramide ranges of the western usa imply operation of periglacial surface processes over millions of years the occasional tors imply a steeper rather than flatter initial landscape the strong decoupling of surfaces from glacial troughs justifies their use as local geomorphic markers that allow calculation of relief production since glacial incision was initiated on the other hand their present low curvature does not require a landscape history in which these surfaces were once joined as an initially widespread erosion surface

age of the mousterian industry at hayonim cave northern israel using electron spin resonance and 230th 234u methods abstract electron spin resonance esr analysis was done on teeth excavated at hayonim between 1993 and 1997 230 th 234 u analysis was done on two of these teeth and one calcite speleothem excavated in 1992 small amounts of uranium uptake into teeth provided nearly ideal conditions for esr age determinations the combined esr 230 th 234 u analyses on teeth confirmed that uranium uptake occurred according to values constrained by early eu and linear lu uptake esr model age estimates suggesting that eu and lu esr model ages on other teeth were reliable burial ages a speleothem stratigraphically above all the teeth yielded a 230 th 234 u age of 155 3 2 9 1 4 ka the eu and lu esr mean model ages for teeth in layers just below the speleothem were 177 12 and 182 15 ka respectively teeth in the lowest part of the section in the central area yielded younger ages apparently due to the increase in radioactive potassium content associated with the formation of siliceous aggregate mineral assemblages nearby these results were rejected the ages of the reliably dated portion of the section were contemporaneous with levels at tabun cave containing both tabun c type and d type lithics but they were significantly younger than the levels at tabun which contain only the d type lithics the use of infrared spectroscopy to identify mineral assemblages in close proximity to teeth were important to be able to select only those teeth not affected by changes in radioactive dose rate through time

three dimensional distribution of minerals in the sediments of hayonim cave israel diagenetic processes and archaeological implications the mineral components of the sediments that accumulate in an archaeological site constitute a potentially rich source of information on the diagenesis and in turn the archaeology of the site this detailed three dimensional study of the mineral assemblages in mainly the mousterian sediments of hayonim cave incorporates more than 2100 infrared analyses performed on site during the excavation as well as diverse analyses in the laboratory three major mineral assemblages are identified the calcite dahllite cd assemblage the assemblage comprising mainly montgomeryite leucophosphite and siliceous aggregates lmvs and a highly altered sediment in which the clays have broken down and silica was released the boundaries between these assemblages were mapped in detail the overall picture is one of extreme heterogeneity with sharp variations occurring over distances of a few centimetres the relation between the cd and lmvs assemblages shows that it is a product of post depositional diagenesis whereas the altered clay assemblage formed beneath an erosional unconformity the cd and lmvs assemblages were derived primarily from an accumulation several metres thick of ash deposits produced by humans ash is thus shown to be a major component of the sediments of this cave the distribution of the cd assemblage reflects to a large extent the locations of two active springs seepages in the cave the distribution of the cd assemblage also faithfully maps the distribution of bones in the cave showing that their distribution is a function of preservational conditions and not human activities stineret al 2001 the conditions that produced the erosional unconformity also resulted in severe alteration of the clays and other mineral components of these sediments the erosion process and the fact that the thickness of this altered zone decreases towards the centre of the cave indicates that the diagenetic driving force was probably climatic the three dimensional distributions of the mineral assemblages have a direct bearing on the dating of the cave by thermoluminescence and electron spin resonance

sediment transport mechanisms on soil mantled hillslopes landscape evolution is modeled widely using a simple creep law for complex processes of sediment transport here field data show how a new transport model combined with an exponential soil production law better captures spatial variations of soil thick ness on hillslopes we combine parameterizations of simple and depth dependent creep with overland flow to predict soil thickness and suggest how soil distribution evolves in response to climatic and tectonic forcing we present an empirical expression for the response time of the system to external forcing that shows strong dependence on relief and is independent of soil production rate we suggest that this parameterization may be used to quantify upland carbon storage and removal and predict impacts of defor estation or rapid climatic changes

evidence from luminescence for late pleistocene formation of calcareous aeolianite kurkar and paleosol hamra in the carmel coast israel abstract calcareous aeolianite kurkar and red loamy paleosol hamra units form ridges in the northern coastal plain of israel the kurkar ridges with hamra units have been thought to be indicators of past sea levels and of palaeoclimate though there has been no clear chronology that could correlate units from one ridge to another or to global palaeoclimate and sea level change we obtained detailed stratigraphy and luminescence ages for the kurkar and hamra units that range from 35 to 101 ka indicating coeval formation of these units during the late pleistocene independent dating suggests that hamra and similar loamy soils formed at 45 to 130 ka in the habonim quarry site at the eastern ridge when kurkar that has been dated by us to 50 67 ka was deposited in the coastal trough showing facies changes from west to east the youngest ages for exposed kurkar in the dor islet at the coastal ridge 35 and 38 ka are close to the 35 ka age obtained independently for the upper kurkar near atlit at the eastern ridge at that time when kurkar was deposited and cemented on the top of both ridges a hamra dated by us to 37 ka formed in the coastal trough our results indicate that kurkar accumulated along the coastal plain at different time intervals throughout the late pleistocene and that its deposition was not necessarily associated with high sea levels moreover our data as well as previous research suggest that hamra also formed at different periods sometimes synchronous with kurkar and its formation is therefore not related to any particular climatic events

flint procurement strategies in the late lower palaeolithic recorded by in situ produced cosmogenic 10be in tabun and qesem caves israel abstract the in situ produced cosmogenic beryllium isotope 10 be in flint artifacts from different layers in prehistoric caves can provide information on flint procurement the buildup of 10 be in a flint matrix is related to the exposure time of the flint to cosmic rays although this exposure history can be complex the 10 be content of flint assemblages can show whether the raw material was obtained from shallow mining and or surface collection as opposed to sediments two or more meters below the surface flint artifact assemblages from two palaeolithic caves in israel tabun and qesem were analyzed in tabun cave the flint artifacts from lower layer e acheulo yabrudian around 400 000 200 000 yr contain very small amounts of 10 be which is consistent with flint procured from sediments two or more meters deep artifacts from above and below tabun lower layer e show a more complex distribution as do artifacts from all layers of qesem cave acheulo yabrudian this is probably due to the fact that they were surface collected and or mined from shallow less than 2 m depths we show here that artifact assemblages have different concentrations of 10 be indicating different raw material procurement strategies

tl dates of burnt flints from jelinek s excavations at tabun and their implications abstract a selection of 37 burnt flints from jelinek s excavations at tabun were dated by thermoluminescence the results indicate that the bottom of unit i garrod s layer c should be given an age of 171 17 ky bp transition from oxygen isotope stage 7 to 6 and that units xiii to ii layers ed to d were deposited between c 330 and 210 ky bp i e during the oxygen isotope stages 9 8 and the beginning of 7 these dates raise the possibility that a a pre wurmian neanderthal population may have settled in the levant during the oxygen isotope stage 6 and that b the transition from mugharan acheuleo yabrudian yabrudian and amudian to levallois mousterian type lithic industries occurred at the end of stage 8 more than 200 ky ago these early dates whose reliability was consistent with isochron analysis of the data are not that different from those now accepted for the development of the levallois mousterian industries in europe

esr dating of archaeologically relevant authigenic terrestrial apatite veins from tabun cave israel abstract apatite veins exposed at tabun cave were collected for an electron spin resonance esr dating feasibility study the dose response and thermal stability of the esr signals were found to be suitable for an age determination using a signal at g 2 0015 the early and linear uptake esr ages were found to be in the range of 45 75 ka since the apatite vein is known to have crystallized in situ after the formation of the host sediments the age was expected to be younger than that of the host sediments thermoluminescence dating of heated flints j archaeol sci 22 1995 495 in corresponding units establish the age of the host sedimentation to be 306 33 ka or greater the apatite veins ages were found to be at least 200 ka younger consistent with their expected younger age we emphasize that these results are not relevant to a resolution of the controversy that remains in the literature regarding the burial ages of sediments at tabun cave the significance of this dating approach is discussed in relation to diagenesis of bone and guano which is important to our understanding of cave sediment formation and to the determinations of sediment ages using other radiation exposure techniques

diagenesis in prehistoric caves the use of minerals that form in situ to assess the completeness of the archaeological record an interpretation of the archaeological record in particular that of a prehistoric cave site is complicated by the diversity of depositional and post depositional processes that affect the material deposited here we propose to use the authigenic minerals that form in situ within the cave sediments to reconstruct the ancient chemical environments in the sediments this can be done by experimentally determining the conditions under which each of the authigenic minerals are stable although this information is not available to date for minerals formed in a prehistoric cave we present calculated stability field data for the relevant minerals the results clearly demonstrate the feasibility of this approach this information particularly if based on measurements of real authigenic cave minerals will facilitate an assessment of the completeness of the cave archaeological record this is particularly important for determining whether or not the distributions of archaeologically important materials such as bones teeth plant phytoliths charcoal and ash reflect their original burial distributions or were altered as a result of secondary diagenetic processes

crenulation cleavage development by partitioning of deformation into zones of progressive shearing combined shearing shortening and volume loss and progressive shortening no volume loss quantification of solution shortening and intermicrolithon movement abstract an analytical method for determining amounts of cleavage normal dissolution and cleavage parallel shear movement that occurred between adjacent microlithons during crenulation cleavage seam formation within a deformed slate is developed for the progressive bulk inhomogeneous shortening pbis mechanism of crenulation cleavage formation the method utilises structural information obtained from samples where a diverging bed and vein are offset by a crenulation cleavage seam several samples analysed using this method produced ratios of relative cleavage parallel movement of microlithons to the material thickness removed by dissolution typically in the range of 1 1 3 4 1 the mean amount of solution shortening attributed to the formation of the cleavage seams examined is 24 the results indicate that a relationship may exist between the width of microlithons and the amount of cleavage parallel intermicrolithon movement the method presented here has the potential to help determine whether crenulation cleavage seams formed by the progressive bulk inhomogeneous shortening mechanism or by that involving cleavage normal pressure solution alone

block controlled hillslope form and persistence of topography in rocky landscapes rocky hillslopes dotted with boulder sized blocks and covered by a thin nonuniform soil are common in both steep landscapes and arid environments on earth as well as on other planets while the evolution of soil mantled convex upward hillslopes in uniform lithology is reasonably well understood the influence of heterogeneous lithology and geologic structure on hillslope form and evolution has yet to be properly addressed landscapes developed in layered sedimentary rocks feature sharp edged landforms such as mesas and hogbacks that exhibit steep linear to concave upward ramps with scattered blocks calved from resistant rock layers overlying softer strata here we show that blocks can control the persistence of topography and the form and evolution of hillslopes in these landscapes we present a numerical model demonstrating that incorporation of feedbacks between block release interruption of soil creep by blocks and sporadic downslope movement of blocks are necessary and sufficient to capture the morphology and evolution of these landscapes numerical results are reproduced by a simple analytical solution that predicts steady state concave hillslope form and average slope angle from block size and spacing our results illuminate previously unrecognized hillslope feedbacks advancing our understanding of the geomorphology of rocky hillslopes on a landscape scale our findings establish a quantitative method to address the migration of sharp edges and the persistence of topography in layered landscapes

u series dating and human evolution some of the major events in human evolution occurred during the middle pleistocene these include the evolutionary rise of the neanderthals in eurasia and of anatomically modern humans either in africa or on a broader geographical front in addition to major biogeographic changes among mammals including the hominine colonization of europe prior to the middle pleistocene the application of potassium argon and argon argon dating has yielded a relatively detailed chronological picture for the earlier phases of hominid evolution and from c 50 ky radiocarbon dating provides the backbone of our chronology for the extinction of the neanderthals colonization of europe by anatomically modern humans and all subsequent events between these however the middle pleistocene has only been amenable to precise chronometric dating for the past few decades before the advent of radiometric dating as glynn isaac 1975 famously observed the middle pleistocene was the muddle in the middle u series dating is one of a range of dating methods employed by archaeologists to provide a chronology for human evolution fig 1 other applicable methods include optically stimulated luminescence osl which can be used to date sediments perhaps back to about 0 5 my measuring the time since the last exposure to sunlight it is increasingly employed as a dating method especially since suitable sediments are common on archaeological sites e g aitken 1992 a related technique thermoluminescence tl can be used to date burnt flint artifacts e g aitken 1985 which provide a more direct date for specific human activity on a site although material that is suitably burnt is relatively rare potassium argon and argon argon dating have been the most useful techniques for calibrating early hominid evolution because its limit for dating extends considerably beyond the origins of the earliest hominids at around 5 my e g curtis and hay 1972 their application however is

chronology of the middle palaeolithic open air site of combe brune 2 dordogne france a multi luminescence dating approach abstract the bergerac region of south western france is well known for its wealth of middle palaeolithic open air sites however their chronology remains poorly understood due to the complexity of the deposits and difficulties applying radiometric dating techniques combe brune 2 excavated in 2006 and 2007 by the inrap institut national de recherches archeologiques preventives comprises a substantial stratigraphic sequence providing an almost continuous sedimentary record that is unique for the region three lithic assemblages were documented in the eastern part of the site and six stratified assemblages in the western part five of which are concentrated in unit 7 all the clearly individualised industries portray an unequivocal techno economic coherence and are dominated by levallois debitage minerals present in the sediments were dated by the optically stimulated luminescence osl using different protocols thermal transfer tt osl for quartz grains and irsl and post ir irsl for feldspar grains heated flints were also dated by thermoluminescence tl dating results obtained from quartz and feldspars grains provide an age of 234 25 ka for unit 8 at the base of the western sequence 161 18 to 97 3 12 ka for unit 7 63 1 6 5 ka for unit 4 and a series of ages ranging from 39 2 4 0 to 22 3 2 2 ka for unit 3 tl ages obtained from heated flints recovered from the base of unit 7 in the eastern section range from 183 20 to 195 16 ka these results are in good agreement and are stratigraphically coherent suggesting that the early middle palaeolithic occupation the first documented for the bergerac region can be placed at the end of marine isotopic stage mis 7 and the beginning of mis 6

the complex nature of creep movements on steeply sloping ground in southern rwanda long term soil creep motion is often represented as a type of laminar flow with velocity vectors parallel to the slope and constant in time records on a hillslope in southern rwanda reveal that creep movements there compare more with turbulent flow characterized by a a1 humic horizon superlayer creeping over a subsoil affected by more irregular creep deformation

statistical description of slope dependent soil transport and the diffusion like coefficient 1 for hillslopes undergoing diffusive soil transport it is often assumed that the soil flux is proportional to the local land surface gradient where the coefficient of proportionality is like a diffusion coefficient inasmuch as transport involves quasi random soil particle motions related to biomechanical mixing and similar dilational processes a slope dependent relation arises from a balance between particle fluxes that tend to loft a soil and gravitational settling of particles into available pore space a specialized form of the fokker planck equation adapted to such particle motions clarifies how the particle flux involves advective and diffusive parts this in turn contributes to a kinematic description of the diffusion like coefficient ingredients of this coefficient include an active soil thickness a characteristic particle size the porosity in excess of a consolidated porosity and the rate of particle activation as a function of depth these last two ingredients vertical porosity structure and activation rate in effect characterize the magnitude and frequency of settling particle motions related to biological activity and thereby set the rate constant of the transport process the significance of land surface slope is that it is a measure of the downslope component of slope normal lofting that is balanced by settling because the diffusion like coefficient contains the soil thickness the analysis suggests that the soil flux is proportional to the depth slope product the analysis is consistent with published profiles of soil creep displacement and with published estimates of soil flux obtained by downslope integration of soil production rates for hillslopes in california and australia

age of the middle palaeolithic site of rosh ein mor central negev israel implications for the age range of the early levantine mousterian of the levantine corridor abstract a small portion of the early levantine mousterian site of rosh ein mor site was re excavated in 1996 in order to recover ostrich eggshell for uranium series dating analyses flint that appeared to have been heated was recovered from the archive at southern methodist university and tested for its feasibility for thermoluminescence dating flint and eggshell were dated and found to give significantly different results the eggshell yielded a mass spectrometric 230 th 234 u burial age of 200 9 9 5 8 7 ka while the flint showed a range of last heating ages between 14 and 48 ka these ages are compared with other age estimates for sites containing similar lithic industries in the region we conclude that the eggshell age is most likely the minimum age of the time of occupation in which the early levantine mousterian industry was produced and that the flint heating ages represent either later ephemeral occupations with anthropogenic heating of the flints or natural fires in which tree roots heated the flints the results taken together with other age estimates for the early levantine mousterian in this area suggest that while in the central levant we find its earliest appearance between 225 and 300 ka in southern israel we find no correspondingly early ages

how well can hillslope evolution models explain topography simulating soil transport and production with high resolution topographic data the morphology of hillslopes is a direct refl ection of tectonic forcing and climatic and biologic processes that drive soil production mobilization and transport soil transport on hillslopes affects river incision by providing tools for channel abrasion and controls the distribution of sediment that infl uences aquatic habitat although numerous hillslope transport relationships have been proposed over the past 60 years a comprehensive analysis of model predictions for a real landscape has not been performed here we use high resolution topographic data obtained via airborne laser swath mapping alsm to simulate the long term evolution of oregon coast range hillslopes and test three published transport models and a new model that accounts for nonlinear depth and slopedependent transport analysis of one dimensional steady state solutions for these four models suggests that plots of gradient curvature may be diagnostic for distinguishing model predictions to evaluate two dimensional model predictions for our fi eld site we assumed local steady state erosion for a 72 000 m 2 sequence of hillslopes and valleys after calibrating each of the four models we imposed constant base level lowering for cells within the valley network simulated 500 000 yr of soil production and transport and determined which transport model best preserved morphologic patterns that describe the current landscape form models for which fl ux varies proportionally with hillslope gradient generated broadly convex hilltops inconsistent with the sharp crested steep sided slopes of our study site whereas the two nonlinear slope dependent models produced convex planar slopes consistent with current hillslope form our proposed nonlinear slope and depth dependent model accounts for how soil thickness controls the magnitude of biogenic disturbances that drive transport this model best preserved the current landscape form particularly the narrow sharply convex hilltops characteristic of the oregon coast range according to our formulation which provides an explicit linkage for relating the distribution of biota to hillslope processes the degree of hilltop convexity varies nonlinearly with the ratio of erosion rate to maximum soil production rate highlighting the profound infl uence of soil depth on hillslope evolution

tl dates for the neanderthal site of the amud cave israel abstract age estimates ranging from 50 to 70 ky were obtained for the mousterian deposits of amud cave in israel from thermoluminescence measurements performed on 19 burnt flints the late dates obtained for the stratigraphic layers bearing hominid remains confirm the evidence for the late presence of neanderthals in the levant the dates enable a more effective comparison of the lithic assemblages from amud cave with those of other contemporaneous sites and underline the variability within mousterian lithic industries at the end of the middle palaeolithic in the levant

early and middle pleistocene faunal and hominins dispersals through southwestern asia abstract this review summarizes the paleoecology of the early and middle pleistocene of southwestern asia based on both flora and fauna retrieved from a series of windows provided by the excavated sites the incomplete chrono stratigraphy of this vast region does not allow to accept the direct chronological correlation between the available sites and events of faunal and hominin dispersals from africa it also demonstrates that hominins survived in a mixed landscape of open parkland with forested surrounding hills in addition the prevailing environmental conditions are not sufficient to explain successful adaptations to new ecological niches away from the african savanna of the bearers of core and flake and the acheulian industries the differences in knapping and secondary shaping of stone artifacts probably reflect the learned traditions of different groups of hominins the current distribution of lithic industries across eurasia is undoubtedly incomplete due to lack of cultural continuities as well as paucity of field research in several sub regions this observation supports the contention that what we view as a constant stream of migrants was actually interrupted many times the continuous occupation of southwestern asia by the makers of the acheulian is in contrast with neighboring regions such as the iranian plateau and eastern europe a more complex model is required to explain the recorded eurasian archaeological cultural mosaic

lithologic control on the form of soil mantled hillslopes slopes in steady state soil mantled landscapes tend to increase downslope in a way that balances local transport capacity with the sediment supplied from progressively larger source areas most formulations of sediment transport due to hillslope processes scale transport rate with local slope which produces convex up forms that are independent of the properties of the underlying lithologies in this study we document soil mantled hillslopes that show variations in slope that mimic the underlying stratigraphy we present stratigraphic and soil thickness measurements topographic analyses and numerical models to demonstrate that variations in rock type can impact the forms of these soil mantled hillslopes if hillslope transport rates scale with local slope and soil thickness this demonstrates that hillslope forms in soil mantled landscapes can be influenced by the underlying lithology through a coupling between the processes that produce soil from rock and those that transport this soil downslope

evidence for nonlinear diffusive sediment transport on hillslopes and implications for landscape morphology steep soil mantled hillslopes evolve through the downslope movement of soil driven largely by slope dependent transport processes most landscape evolution models represent hillslope transport by linear diffusion in which rates of sediment transport are proportional to slope such that equilibrium hillslopes should have constant curvature between divides and channels on many soil mantled hillslopes however curvature appears to vary systematically such that slopes are typically convex near the divide and become increasingly planar downslope this suggests that linear diffusion is not an adequate model to describe the entire morphology of soil mantled hillslopes here we show that the interaction between local disturbances such as rainsplash and biogenic activity and frictional and gravitational forces results in a diffusive transport law that depends nonlinearly on hillslope gradient our proposed transport law 1 approximates linear diffusion at low gradients and 2 indicates that sediment flux increases rapidly as gradient approaches a critical value we calibrated and tested this transport law using high resolution topographic data from the oregon coast range these data obtained by airborne laser altimetry allow us to characterize hillslope morphology at 2 m scale at five small basins in our study area hillslope curvature approaches zero with increasing gradient consistent with our proposed nonlinear diffusive transport law hillslope gradients tend to cluster near values for which sediment flux increases rapidly with slope such that large changes in erosion rate will correspond to small changes in gradient therefore average hillslope gradient is unlikely to be a reliable indicator of rates of tectonic forcing or baselevel lowering where hillslope erosion is dominated by nonlinear diffusion rates of tectonic forcing will be more reliably reflected in hillslope curvature near the divide rather than average hillslope gradient

aspect dependent variations in regolith creep revealed by meteoric 10be although variations in insolation and emergent feedbacks among soil moisture vegetation and soil cohesion are commonly invoked to explain topographic asymmetry that depends on aspect few studies have directly quantified the efficiency of regolith transport along hillslopes of opposing aspect we utilize meteoric 10 be concentrations in regolith n 74 to determine mass flux along equatorial facing and polar facing hillslopes in three forested upland watersheds in and adjacent to the susquehanna shale hills critical zone observatory in central pennsylvania usa in combination with regolith depth measurements and high resolution topography these fluxes allow us to evaluate transport rate laws and the efficiency of regolith creep concentrations of meteoric 10 be in regolith along six separate transects imply that regolith flux is similar along all hillslopes despite differences in topographic gradient and regolith thickness comparison of flux with regolith depth and topographic gradient reveals that transport depends on regolith depth and that regolith creep is twice as efficient along low gradient south facing slopes with thin regolith as compared to steep north facing slopes mantled with thicker regolith we suggest that the observed topographic asymmetry in these watersheds has evolved over geologic time as a result of differences in the frequency of freeze thaw events between hillslopes of opposing aspect

an analysis of the compositional integrity of the levantine mousterian facies abstract for almost a century the levantine mousterian facies b c and d first defined by dorothy garrod at mugharet et tab n have figured prominently in discussions of spatial and temporal variability in the middle paleolithic of the levant although much modified by subsequent workers and frequently described qualitatively the compositional integrity of these basic analytical units has never been assessed quantitatively here we describe the statistical parameters of the facies using a large data set comprising 54 collections from 20 sites assigned by the excavators to one or another of the facies a statistical summary revealed many cross cutting patterns that departed from qualitative descriptions of the facies calling their compositional integrity into question a multivariate discriminant analysis helped resolve some of these problems it confirmed a strong statistical affinity between the b and c facies which were in turn sharply differentiated from d our results are then compared with the stratified mousterian sequence at hummal a site in the syrian desert relatively good correspondence was attained implications of the analysis are discussed in terms of the adequacy of the systematics used to identify facies differences and what they might mean behaviorally

weathering limited hillslope evolution in carbonate landscapes understanding topographic evolution requires integrating elementary processes acting at the hillslope scale into the long wavelength framework of landscape dynamics recent progress has been made in the quantification of denudation of eroding landscapes and its links with topography despite these advances data is still sparse in car bonate terrain which covers a significant part of the earth s surface in this study we measured both long term denudation rates using in situ produced 36 cl concentrations in bedrock and regolith clasts and surface convexity at 12 sites along ridges of the luberon carbonate range in provence southeastern france starting from 30 mm ka for the lowering of the summit plateau surface denudation linearly increases with increasing hilltop convexity up to 70 mm ka as predicted by diffusive mass transport theory beyond this point denuda tion rates appear to be insensitive to the increase in hilltop convexity we interpret this constant denudation as indicating a transition from a regime where hillslope evolution is primarily controlled by diffusive downslope regolith transport toward a situation in which denuda tion is limited by the rate at which physical and chemical weathering processes can produce clasts and lower the hilltop such an abrupt transition into a weathering limited dynamics may prevent hillslope 1 denudation from balancing the rate of base level fall imposed by the river network and could potentially explain the development of high local relief in many mediterranean carbonate landscapes

geo chronological context of the open air acheulian site at nahal hesi northwestern negev israel abstract the open air site of nahal hesi located on northwestern negev desert fringe of israel is one of the few primary context late acheulian localities in the levant late acheulian sites in the levant rarely provide faunal assemblages and radiometric ages leaving large gaps in our knowledge of the lower paleolithic palaeoenvironment ecology subsistence and chronology here we present a new geo chronological study conducted at the nahal hesi site the major objectives were to describe the geological and archaeological stratigraphy assign a numerical age to the acheulian artifact bearing deposit by tt osl and pir ir290 dating and reconstruct the local palaeoenvironment during the human occupation at the site geological and microfaunal observations suggest that late acheulian hominins at nahal hesi exploited marshy environments the limited spatial and vertical extent of the artifact bearing deposit and the presence of artifacts only in context of marsh like sediments highlight the utilization of short lived water bodies by the hominins the combined tt osl and pir ir290 methods provide an average age of 430 35 ka for the studied marsh like deposits the study indicates that the middle pleistocene in the area of the nahal hesi site is characterized by lengthy cycles of deposition and erosion of fine grained sediments associated with the semi arid nahal shiqma drainage system marshy sediments could be the result of full or partial blockage of the shiqma system probably by coastal dune ridges that led to formation of standing water bodies during the middle pleistocene

dating the lower paleolithic open air site of holon israel by luminescence and esr techniques abstract the open air acheulian site in holon israel was dated by the luminescence methods and by electron spin resonance esr situated in the coastal plain quaternary kurkar group the holon site was first excavated in the late 1960s when typical lower paleolithic lithics and middle pleistocene fauna were found in order to date the site new test pits were dug adjacent to the earlier excavations and the archaeological bed was exposed in a section comprising a series of paleosols and aeolianites alkali feldspars separated from the sediments were dated using the infrared stimulated luminescence and thermoluminescence signals and quartz was dated using the optically stimulated luminescence signal the age of the archaeological bed is constrained by two samples to 198 000 22 000 201 000 17 000 yr the age of the base of the section is 240 000 29 000 yr and the age of the top is 81 000 8000 yr two teeth from the archaeological bed recovered from the original excavation collection yielded an average esr age of 204 000 16 000 yr calculated using the linear uptake model which is in a very good agreement with the luminescence ages these dates place holon within the range of other late acheulian and acheulo yabrudian sites in this region such as tabun e younger chronology yabrud i archaeological level 18 and berekhat ram

soil development over mud rich rocks produces landscape scale erosional instabilities in the northern gabilan mesa california in soil mantled landscapes the length of hillslopes is set by the relative efficiency of hillslope transport processes and incision by channelized flows in cases where rapid channel incision exposes less weathered more resistant rocks incision should slow creating a damping feedback that prevents runaway channel expansion we present observations from the northern gabilan mesa central coast ranges california which is underlain by mud rich rocks that provide less resistance to erosion than the soils produced from them this strength inversion arises because unconfined mud rich units of the pancho rico formation undergo a process called slaking in which pervasive fractures spaced centimeters apart develop when subjected to wet dry cycles in contrast consecutive wetting and drying cycles have produced a cohesive regolith with higher tensile strength than the slaked bedrock exposure of the relatively weak bedrock may create a positive feedback where the acceleration of erosion within the bedrock undermines the cohesive regolith and allows channels to expand headward at the expense of hillslopes geomorphic mapping reveals numerous channelized features that have incised deeply into bedrock and crosscutting relationships and topographic analyses indicate that these features have consumed regions of the landscape previously occupied by hillslopes however these features are only present in south flowing drainages where soil is thinnest and therefore bedrock is most likely to be exposed by increases in erosion rate preferential headward expansion of these south flowing channels has established a profound topographic asymmetry where south flowing tributaries occupy 75 of drainage basin width these results suggest that processes operating at the scale of the critical zone which may be unique to certain rock types conspire to produce an instability that shapes the morphology of drainage basins

last interglacial age of the eva forest bed central alaska from thermoluminescence dating of bracketing loess abstract the eva forest bed in the yukon tanana upland of east central alaska represents a frozen buried boreal forest this bed consists of well preserved peat lenses sticks roots logs as well as rooted and unrooted stumps of trees where preserved the eva forest bed is overlain by the goldstream formation and underlain by gold hill loess almost all exposures have a prominent unconformity at the top of the gold hill loess even where the forest bed is not preserved attempts have been made over the last 50 yr to determine the age of this bed numerically we report here details of thermoluminescence tl dating of 14 samples of loess from above and below this unconformity in the fairbanks area together with knowledge about the climatic indicators from the eva forest bed these tl age estimates 1 indicate that the most probable age of the eva forest bed is 125 ka the time of the warmest part of oxygen isotope stage 5 and 2 confirm stratigraphic inferences from tephra beds in the upper gold hill loess that erosion has removed variable thicknesses of the original loess complex just prior to the development of the eva forest bed

particle trajectories on hillslopes implications for particle age and 10be structure many geomorphic systems act as conveyor belts onto which material is loaded at a particular rate and is transported in one direction toward another system that serves as a sink as the material travels it ages it changes in grain size it accumulates cosmogenic radionuclides it adsorbs or releases nutrients and it weathers here i address the hillslope conveyor as many geochemical processes are depth dependent the depth history of a particle becomes important to know i calculate soil particle trajectories in the horizontal depth plane and address three cases one in which horizontal speeds decline exponentially with depth a second in which they are uniform with depth and a third in which horizontal speeds are also uniform but all profile values are vertically well mixed vertical speeds are governed by continuity in an incompressible medium and by the boundary condition of zero vertical particle speed at the soil surface particle trajectories must therefore become surface parallel at the surface knowledge of soil particle trajectories allows calculation of residence times and concentration profiles of 10be in the soil the results inform strategies for interpretation of nuclide concentrations in soils and stream sediments and for inference of transport rate profiles in all steady cases the particle age and 10be structure is uniform with distance from the divide when significant vertical gradients in horizontal speed occur the patterns of particle age and of 10be concentration are dominated by the depth scale of the transport process in unmixed cases the particle age and 10be concentration in near surface samples can greatly exceed the vertically averaged values reflecting the fact that the vertical speeds of particles slow dramatically as they near the surface in cases in which horizontal speed varies significantly with depth the vertically averaged concentration of 10be within the soil can significantly under predict the mean 10be concentration of sediment delivered to the channel proper averaging requires weighting by particle speed these results provide the backdrop for addressing chemical evolution of soil on a hillslope

the illusion of diffusion field evidence for depth dependent sediment transport soil covered upland landscapes are common in much of the habitable world and our understanding of their evolution as a function of different climatic tectonic and geologic regimes is important across a wide range of disciplines erosion laws direct quantitative study of the processes shaping earth s surface and form the basis of landscape evolution modeling but are based on limited field data here we use in situ produced cosmogenic 1 0 be and 2 6 al concentrations from granitic saprolite to quantify an exponential decline in soil production with increasing soil thickness for a new field site in point reyes california results are similar to soil production functions from two different previously studied field sites and are used with extensive measurements of soil thickness to quantify depth integrated sediment transport flux plots of calculated sediment fluxes against the product of soil depth and hillslope gradient provide the first field based evidence that soil transport is a nonlinear depth dependent function data from all sites suggest that the widely used linear diffusion equation is only appropriate for shallow gradient convex up regions while the depth dependent transport law is more broadly applicable quantifying both the mobile soil thickness and landscape morphology is therefore critical to understanding how landscapes evolve