bed material transport estimated from the virtual velocity of sediment this study evaluates the possibility of determining bed material transport using the virtual rate of travel of individual particles dimensions of the active layer of the streambed and porosity and density of streambed material magnetically tagged stones and scour indicators were employed in carnation creek british columbia to quantify transport rates observations cover flows up to 36 m3 s 1 0 081 transport rates ranging from 0 090 to 9 7 kg s 1 0 12 13 2 m3 h 1 display a relatively sensitive trend with maximum stream power as expected error analysis indicates that uncertainty in virtual velocity covers the majority of sample variance an evaluation of the two measurement techniques used to delineate active layer dimensions magnetically tagged stones and scour indicators indicates that they yield comparable depths widths and transport rates over the range of flows observed issues for further study are discussed 1998 john wiley sons ltd

measurement of the spatial distribution of fluvial bedload transport velocity in both sand and gravel maps are presented of the spatial distribution of two dimensional bedload transport velocity vectors bedload velocity data were collected using the bottom tracking feature of an acoustic doppler current pro ler adcp in both a gravel bed reach and a sand bed reach of fraser river british columbia block averaged bedload velocity vectors and bedload velocity vectors interpolated onto a uniform grid revealed coherent patterns in the bedload velocity distribution concurrent helley smith bedload sampling in the sand bed reach corroborated the trends observed in the bedload velocity map contemporaneous 2d vector maps of near bed water velocity velocity in bins centered between 25 cm and 50 cm from the bottom and depth averaged water velocity were also generated from the adcp data using a vector correlation coef cient which is independent of the choice of coordinate system the bedload velocity distribution was signi cantly correlated to the near bed and depth averaged water velocity distributions the bedload velocity distribution also compared favorably with variations in depth and estimates of the spatial distribution of shear stress published in 2004 by john wiley sons ltd

non destructive fabric analysis of prehistoric pottery using high resolution x ray microtomography a pilot study on the late mesolithic to neolithic site hamburg boberg abstract the characterisation of prehistoric pottery fragments presents a quite complex task in provenance studies petrographic and chemical analyses of the ceramic materials are employed to investigate potential production areas in respect to the geolocial background moreover also the production technology of the firing process as well as the forming techniques used by the prehistoric potters are of great interest their investigation is most often accompanied by a destructive preparation of the samples in this paper we want to present high resolution x ray microtomography ct a non destructive and non invasive method as a supplementary research tool in the study of prehistoric pottery ceramic fragments from the endmesolithic neolithic site hamburg boberg 15 northern germany were analysed by x ray microtomography ct inspection combines quantification and shape analysis of fabric components by means of computer aided image processing as the ct method is sensitive to material densities qualitative and quantitative analyses of different temper materials are possible furthermore the ct method permits the characterisation of the connectivity within the porous system as well as the analysis of the orientation of the pore structures which are indicative for vessel forming techniques although limited by the resolution of the reconstructed images distribution analysis of heavy minerals in the clay matrix can offer distinctive features to discriminate various clay sources moreover x ray microtomography can be used to infer the nature of organic temper even with all plant remains completely burnt out during the firing process the visualisation of the high resolution true volume renderings and their detailed morphometric characterisation enables new avenues in the study of ceramic technology

crystallographic and structural transformations of sedimentary chalcedony in flint upon heat treatment the early occurrence of intentional heat treatment of silica rocks has recently become a key element in the discussion about the cultural modernity of prehistoric populations lithic vestiges are the only sources that remain of this process and the understanding of the material s properties and transformations are essential for reconstructing the conditions and parameters applied during heat treatment several models of the structural transformations upon heating have been proposed in the current literature these models are often contradictory and do not account for the most recent structural and mineralogical data on chalcedony in order to propose a new model we elaborated an experimental procedure and applied different techniques involving infrared spectroscopy solid state nmr x ray diffraction and electron microscopy the results show that the major transformation to happen is the loss of silanole sioh and the creation of new si o si bonds according to the reaction si oh ho si si o si h2o this reaction starts between 200 degrees c and 300 degrees c and causes an increase in the hardness of the rocks the maximal annealing temperature and the ramp rate are the functions of the ability of the structure to evacuate newly created h2o and depend on the size of the specimen and the volume of its porosity these results also show that the annealing duration at maximum temperature can be relatively short 50 min for a sufficiently large amount of transformation to be accomplished

deconvolution technique to separate signal from noise in gravel bedload velocity data a deconvolution procedure is presented to estimate the probability density function of bedload transport velocity from noisy stationary data collected using the bottom tracking feature of acoustic doppler current profilers adcps the procedure involves the optimization of a computational summation of random variables for the instrument noise assumed to be gaussian with zero mean and the spatially averaged bedload velocity within the insonified area of each acoustic beam v the procedure was tested on two adcp time series measured in two different gravel bed rivers fraser river and norrish creek models generated using either a semitheoretical compound poisson gamma distribution or an empirical gamma distribution for v were similar and did not differ significantly from the distribution of the original data optimized distributions for v were highly positively skewed the instrument noise was comparable to instrument noise for adcp water velocity measurements i e an order of magnitude greater t

investigations of continuous bed load saltating process particle saltating motions during bed load transport are dominated by the forces acting upon particles and the random process of the particles impacting on and rebounding from the channel bed a real time flow visualization technique is developed in this study to measure particle saltating trajectories corresponding velocities and impacting and rebounding angles based on the experimental data regression equations for the dimensionless saltating length height and velocity were obtained a numerical model that is able to simulate the continuous saltating process of a single particle was developed the model was calibrated and verified with the experimental data and the results were satisfactory the model was also used to generate a series of synthetic data based on these data and the flume data collected by previous investigators a bed load equation was derived

heat treatment in the south african middle stone age temperature induced transformations of silcrete and their technological implications abstract it was recently found that silcrete raw material was heat treated during the south african middle stone age msa for altering its flaking properties this finding led to hypotheses about the implications for the msa hunter gatherers such as the cost of thermal treatment in terms of investment and firewood to date these hypotheses lack a solid basis for data on the thermal transformations of south african silcrete and hence the necessary heating procedure and heating environment is missing in order to produce such data we conducted an experimental study within the framework of the diepkloof project this work is based on the petrographic mineralogical and structural analysis of south african silcrete from the west coast and its thermal transformations our results shed light on the nature of these transformations the ideal heating temperatures and the tolerated heating speed the processes occurring in silcrete are comparable to flint i e the loss of chemically bound water and the formation of new si o si bonds but their intensity is less pronounced effective heating temperatures are significantly higher than for flint and the heating speed tolerated by south african silcrete is relatively fast these findings imply that silcrete heat treatment cannot be directly compared with flint heat treatment unlike flint heating silcrete does not require the setup of a dedicated heating environment and may have been performed in the same time as other fire related activities this would represent only a minor supplementary investment in time and firewood these results have broad implications for the discussion about technological evolution and the acquisition of specialised knowledge in the msa

case study of precision of gps differential correction strategies influence on adcp velocity and discharge estimates the precision of four differential global positioning systems dgps was evaluated in the context of fluvial water velocity and discharge measurement dgps is used to resolve water velocities measured with an acoustic doppler current profiler adcp into earth coordinates if bottom tracking is unavailable the dgps systems assessed were 1 the dual frequency real time kinematic rtkl1l2 2 the single frequency real time kinematic rtkl1 3 the code phase canadian coast guard cg and 4 the code phase wide area augmentation system waas repeat discharge surveys n 22 were conducted at a transect of the gatineau river canada simultaneously collecting bottom track boat velocity vbt and boat velocity from all four dgps vdgps the mean absolute single ping differences between vbt and vdgps were 3 1 rtkl1l2 3 2 rtkl1 8 9 cg and 9 8 cm s waas errors were observed more often near channel margins presumably due to obstruction and multipath associated with riverbank vegetation

sediment transport along lower fraser river 1 measurements and hydraulic computations a comprehensive program of sediment transport measurements was conducted along lower fraser river british columbia between 1966 and 1986 the data yield a detailed sediment budget annual total suspended loads at three stations are virtually identical averaging 17 106 tonnes year t yr 1 the suspended sand load is about 5 5 106 t yr 1 about one third of the total in the gravel bed reach of the river the sand behaves as wash load significant transport of gravel begins at agassiz at a discharge of about 5000 m3 s 1 the annual gravel transport was estimated to be about 0 23 106 t yr 1 only 1 of the total load all of this material is deposited in the reach upstream of mission at mission sands finer than 0 177 mm make up more than 50 of the suspended sand load but are virtually absent from the sand bed therefore a portion of the sand load at mission is wash load the total bed material load here was estimated to be 3 0 106 t yr 1 about 18 of the total sediment load virtually all of the bed material load was transported in intermittent suspension near the bed less than 5 occurring as bed load in the long term the suspended sand load upstream is approximately equal to the total sand load at mission however within individual years some of the sand is stored within the reach temporarily and then reentrained later

distance of movement of coarse particles in gravel bed streams distributions of distance of bedload particle movement were examined in two gravel bed streams using several hundred magnetically tagged cobbles and pebbles the compound poisson model of einstein hubbell sayre and a simple gamma function model were compared with observed distributions of moved particles and of all particles both models fit the data reasonably well for small mean displacements but notable misfits occurred in an event with large mean displacement when mean particle travel distance approaches the scale of bar spacing trapping in the bars interrupts particle progress and the dispersion process the data remain very noisy so definitive discrimination of suitable models will require trials with more than 103 particles

effect of heat treatment on siliceous rocks used in prehistoric lithic technology stone tool manufacture by many prehistoric and recent societies was characterized by deliberate heating of fine grained siliceous rocks to improve their flaking properties extensive mechanical testing of heated and unheated cryptocrystalline and macrocrystalline quartz lithologies has shown that thermal treatment causes a consistent marked reduction in fracture toughness this mechanical property can be used as an objective measurement of the flaking qualities of stone materials and a reliable criterion for the recognition of intentionally heated artefacts in the archaeological record x ray diffraction studies and scanning electron microscopy have demonstrated that the change in fracture toughness with heating is the result of recrystallization the poorly ordered strongly interlocking cryptocrystalline fabric of the unheated samples becomes more equigranular and better crystallized with thermal treatment as a consequence fractures propagate more readily in heated samples accounting for their better flaking properties

bedload entrainment travel lengths step lengths rest periods studied with passive iron magnetic and active radio tracer techniques this paper reports results from bedload transport investigations with active radio and passive iron magnetic tracers in the lainbach a step pool mountain river in bavaria southern germany the spatial distributions of the iron tracers after flood events can be best described by exponential or gamma distributions there is some indication of a tendency of size selective transport of the iron tracers but there is also a considerable amount of scatter in the correlations between weight size and travel length owing to the masking influence of other variables such as the shape of the particles and different positions in the river bed the experiments with artificial magnetic tracers showed that elongated pebbles rods had the longest mean transport distance platy ones discs remained relatively close to the starting points the particles from the pool showed the greatest transport lengths and a 100 per cent chance of being eroded the pebble transmitter system petsy consists of transmitters implanted into individual pebbles a computerized receiver a stationary antenna system with an antenna switchboard and a data logging system the particles do not move continuously but in a series of transport steps and non movement intervals a single value for a given size class is not adequate to describe the critical conditions of entrainment under natural circumstances a probability approach is much more suitable the critical unit discharges total discharge divided by active channel width along the measuring reach are dependent on river bed morphology in the steps bedload needs higher unit discharges to be entrained once entrained the transport of bedload is stochastic in nature and the single particle transport is controlled by the step lengths and the duration of rest periods the distributions of both parameters can be approximated by exponential functions applying the stochastic concept proposed by einstein the mean values of the random variables step length and duration of rest period measured with the petsy technique were used for the simulation of spatial distributions of bedload particles from point sources more field and laboratory data are needed to include varying flow and roughness conditions with tracers representing different particle characteristics

evolution of eureka flat a dust producing engine of the palouse loess usa sedimentologic stratigraphic and pedologic evidence demonstrates that eureka flat ef a narrow 80 km long deflation plain in south central washington usa is the source for the thick and widespread loess of the palouse region located in the southern columbia plateau ef has been a depocenter for abundant clay to sand sized sediment derived from repeated glacial outburst floods that swept through the area during the pleistocene prevailing sw winds that were funneled across ef remobilized flood sediment into sand dunes sand sheets and loess an eolian sand sheet buried beneath 1 8 m of loess at the downwind end of ef attests to bioclimatically driven changes in the style of eolian deposition the depositional transition from sand sheet to loess is characterized by a change from wind rippled strata to structureless bimodal sand and silt with insect burrows and rhizoliths to unimodal sandy loess soil moisture and density of dust trapping vegetation control where sand dunes and loess accumulate up to 4 5 m of post lgm loess mantles the landscape adjacent to and downwind from ef some of the thickest loess deposits owe their origins to the sequestering of eolian sand particles by topographic traps such as the touchet river and its tributary valleys the removal of saltating sand from the eolian system promotes thick accumulation of loess downwind of topographic traps patterns of loess accumulation across the columbia plateau are identified on isopach maps of major pre and post lgm loess units and show that ef has been the major engine for the production of atmospheric dust and loess during both times

radio tracking gravel particles in a large braided river in new zealand a field test of the stochastic theory of bed load transport proposed by einstein hans a einstein initiated a probabilistic approach to modelling sediment transport in rivers his formulae were based on theory and were stimulated by laboratory investigations the theory assumes that bed load movement occurs in individual steps of rolling sliding or saltation and rest periods so far very few attempts have been made to measure stochastic elements in nature for the first time this paper presents results of radio tracing the travel path of individual particles in a large braided gravel bed river the waimakariri river of new zealand as proposed by einstein it was found that rest periods can be modelled by an exponential distribution but particle step lengths are better represented by a gamma distribution einstein assumed an average travel distance of 100 grain diameters for any bed load particle between consecutive points of deposition but larger values of 6 7 m or 150 grain diameters and 6 1 m or 120 grain diameters were measured for two test particle sizes together with other available large scale field data a dependence of the mean step length on particle diameter relative to the d50 of the bed surface was found during small floods the time used for movement represents only 2 7 of the total time from erosion to deposition the increase in percentage of time being used for transport means that it then has to be regarded in stochastic transport models tracing the flow path of bed load particles between erosion and deposition sites is a step towards explaining the interactions between sediment transport and river morphology copyright 2001 john wiley sons ltd

virtual rate and mean distance of travel of individual clasts in gravel bed channels travel distances in gravel bed rivers of tagged particles of various sizes are related to excess stream power estimated for peak discharge mean distance of movement irrespective of grain size is weakly correlated with stream power especially near the threshold of movement there may be several reasons for the weak correlation including variable effects of bed structure varying magnitudes of sediment mobilizing events and sampling problems grain size itself is of marginal significance the virtual rate of travel calculated using total time for which the flow is larger than that needed to initiate clast movement also bears a weak relation to the excess stream power over the period better results are obtained by relating the virtual rate of travel to the first peak of the flow event only this implies that the initial seeding of the tagged particles dominates the observations nonetheless an underlying general relation is indicated by the data which are derived from a wide range of flow regime types

early use of pressure flaking on lithic artifacts at blombos cave south africa pressure flaking has been considered to be an upper paleolithic innovation dating to 20 000 years ago 20 ka replication experiments show that pressure flaking best explains the morphology of lithic artifacts recovered from the 75 ka middle stone age levels at blombos cave south africa the technique was used during the final shaping of still bay bifacial points made on heat treated silcrete application of this innovative technique allowed for a high degree of control during the detachment of individual flakes resulting in thinner narrower and sharper tips on bifacial points this technology may have been first invented and used sporadically in africa before its later widespread adoption

airflow terrain interactions through a mountain gap with an example of eolian activity beneath an atmospheric hydraulic jump the integration of atmospheric soundings from a fully instrumented aircraft with detailed sedimentary and geomorphic analyses of eolian features in the ferris dune field of south central wyoming lends insight into the manner in which topography interacts with airflow to modify eolian activity topographically modified airflow results in zones of airflow deceleration acceleration and enhanced atmospheric turbulence all of which influence the surface morphology and sedimentology extreme lateral confluence of prevailing airflow produces accelerated unidirectional winds these winds correlate with unusually continuous and elongate parabolic dunes that extend into a mountain gap windy gap persistently heightened winds produced at the entrance to windy gap have resulted in a concentration of active sand dunes that lack slipfaces common development of a strongly amplified atmospheric wave analogous to a hydraulic jump in the gap contributes to the formation of a variety of eolian features that mantle the surface of windy gap and the ferris dune field tail heightened unidirectional winds in this zone promote grain size segregation the formation of elongated and aligned sand drifts climbing and falling dunes elongate scour streaks and parabolic dunes that have low angle 20 sup 0 cross stratification deflation of bedrock and loose sediment has been enhanced in the zonemore of maximum turbulence beneath the hydraulic jump less

late holocene intensification of colds fronts in southern brazil as indicated by dune development and provenance changes in the sao francisco do sul coastal barrier abstract holocene coastal barriers from southern brazil present great geomorphological changes during their late stages of development in this study we investigate the holocene evolution of the sao francisco do sul sfs barrier through geomorphological heavy minerals and grain size analyses constrained by optically stimulated luminescence osl dating the sfs barrier stands out among the southern brazilian barriers due to its well preserved morphology with a parabolic dune belt in the seaward portion the progradation of the sfs barrier started at least 4914 478 years ago and had a pronounced morphodynamic shift around 1891 155 years ago this shift is characterized by episodic development of parabolic dunes migrating to nnw associated with sand coarsening and a marked variation in sediment provenance represented by the input of sands derived from local coastal watersheds southward from the sfs barrier this morphodynamic provenance shift resulted from the strengthening of sse winds and associated wave systems responsible for the northward alongshore drift implying intensification of cold fronts coupled with higher precipitation since 1891 155 years ago osl dating combined with grain size heavy minerals and geomorphological analyses allowed assessing the response of coastal barriers to the impacts of centennial to millenial climate events occurred during the late holocene reconstruction of the late holocene climate variability and associated impacts on coastal sedimentation is a key issue to evaluate the sensitivity of coastal barriers to future climate changes

late pleistocene eolian sand sheets in alaska abstract nonglaciated lowlands in central and southwestern alaska contain extensive deposits of upper quaternary eolian sand derived largely from major outwash rivers although surface dunes are common deep exposures consistently reveal that subhorizontally stratified sand and silt deposits dominate over dune cross strata we hypothesize that 1 many of the subhorizontally stratified deposits represent full glacial eolian sand sheets formed when sand supply was limited by seasonally variable combinations of ice cementation snow cover high groundwater tables and vegetation and 2 many surface dunes reflect late glacial and postglacial reworking under conditions of increased short term availability of loose sand the morphology of some surface dunes may therefore reflect mainly the intensity of reworking since the last glacial maximum rather than full glacial paleowind vectors or the age of the bulk of the underlying deposits

solutrean and magdalenian ferruginous rocks heat treatment accidental and or deliberate action heating of prehistoric coloring materials can induce radical changes in color indicative of structural matter transformation for instance the structure of the yellow iron oxide rich mineral goethite changes into the red iron oxide rich mineral hematite when it is heated to around 250 300 c for a long time heating has been thought to be the reason for the high frequencies of red rocks used in camp sites and the red pigments in rock art paintings however records of heat treatment of coloring materials are usually not well documented the contextual information is not clear enough to confirm intentional heating two solutrean camp sites the flint workshop les maitreaux and the hunting site combe sauniere i and one middle magdalenian cave with rock art grotte blanchard la garenne allow us to study the heating process of ferruginous rocks all three sites which have been excavated relatively recently have well defined archaeological records and strong associations between the ferruginous rocks and other artifacts with the use of x ray diffraction and electron diffraction for identifying structural modification and sem feg and tem feg for detecting dehydration nano pores we have strong evidence for intentional heat treatment of yellow goethite rich materials in two archaeological contexts and one site for unintentional heating where rocks were only partially transformed intentional heating to obtain red hematite from primary goethite would have required ingenious methods of temperature control in fireplace settings and purpose built ground ovens

first evidence of heat treatment during the early neolithic in northeastern italy the site of la vela sector vii trentino alto adige italy provides one of the few complete stratigraphic sequences ranging from the mesolithic to the middle neolithic in northwestern italy the site is located in the adige valley a way of communication between the po plan and the alps this research focuses on the early neolithic lithics ascribable to the gaban facies dated to 5000 4700 cal bc different rocks coming from local exposures have been exploited the goal of the reduction sequence was the production of blades by pressure knapping technique the technological study of the assemblage raised a particular interest for the presence of flint artifacts suggesting the usage of controlled heat treatment the presence of this technique has been tested by an experimental approach based on fourier transform infrared ft ir spectroscopy complementary microstructural and analytical characterizations with low vacuum scanning electron microscopy lvsem observations combined with energy dispersive x ray spectroscopy edxs have been performed the analyses confirm the presence of artifacts intentionally heat treated the thermal treatment achieved in order to increase the quality of the blade production is the first evidence of this technique in northeastern italy during the early neolithic

testing for the presence of thermal pretreatment of flint in the mesolithic and neolithic of sweden abstract through ethnographic accounts the method of heat treatment of silica materials to improve the flaking qualities is shown to have been known almost worldwide some mesolithic and neolithic flint artifacts from southern sweden were examined in order to determine if they too were heat treated from several methods proving or indicating thermal alteration of flint analysis using scanning electron microscopy was chosen two samples were taken from each artifact one being examined unaltered the other being heat treated no two samples from the same artifact had the same kind of surface appearance thus these analyses prove that the artifacts examined had not been heat treated

inland aeolian deposits of the iberian peninsula sand dunes and clay dunes of the duero basin and the manchega plain palaeoclimatic considerations abstract this paper describes the latest research on the geomorphological characteristics formation environment and chronology of the main inland aeolian deposits from the south eastern duero basin db and the manchega plain mp of the iberian peninsula similarities and differences between the aeolian deposits of these two locations are summarised wind deflation from the guadiana and jucar alluvial systems created the aeolian deposits of the mp these deposits are mainly composed of quartz sands however in the san juan alluvial plain mp there is a large extent of clay dunes formed by exposure to prevalent winds of seasonal playa lakes with salt and clay sediments in the db wind remobilisation of the small particles from quaternary terraces and tertiary arkosic sediments left aeolian deposits of quartz feldspar sands textural parameters of the aeolian deposits show large variations depending on the location and the original deposit thus in the db the aeolian sands derived from the deflation of fluvial sediments are better sorted and smaller in grain size than those created by the deflation of arkosic sediments morphologically simple and compound parabolic dunes u v forms hemicyclic lobate and elongate crescentic and linear dunes climbing dunes and blowout dunes have been recognized at both sites barchan and dome dunes are present only in the db while lunette lunette clay dunes are found only in the mp in both locations the large extent of aeolian sand sheets and the predominance of simple and compound parabolic dunes indicates the active role of sparse vegetation cover in the formation of this aeolian system in the db dunes were formed by southwest and west winds while in the mp the aeolian morphologies indicate that the prevalent winds were west and northwest the chronology of the dune deposits is being determined with luminescence tl osl dating and mass spectrometry analysis 14 c ams in this way the aeolian activity and stabilisation stages can be established the latter well marked in the db through soil a horizon development thus the main sand dune formation in the db and the eastern regions of the mp occurred between 13 5 and 7 ka bp during the cold and arid younger dryas episode and the early holocene the clay dunes of the mp accumulated mainly from 29 to 19 ka bp that corresponds with heinrich events he 3 and he 2 and the last glacial maximum however clay dunes were also formed between 13 5 and 7 ka bp in both locations there have been reactivations of some sand deposits in the recent holocene with maximum activity around 5 2 ka bp and 0 5 0 2 ka bp on the other hand three marked stages of stabilisation of the db aeolian system have been established with 14 c ams around 10 2 6 2 and 1 2 ka bp finally the main winds contributing to dune construction were also responsible for the deflation processes with the formation of erosional depressions

partial transport of a sand gravel sediment grains of a single size within a mixed size bed are entrained over a range of flows within this range some grains exposed on the bed surface are active entrained at least once over the duration of a transport event while the remaining surface grains are immobile a condition we define as partial transport we demonstrate the existence and domain of partial transport using observations of grain entrainment on time series of bed photographs of flume experiments with a widely sorted sand gravel mixture the active proportion of the bed surface increases with bed shear stress 0 at a given 0 90 of the active grains are entrained when the cumulative mass transported exceeds approximately 4 times the active mass on the bed mobilization of grains in a size fraction increases from 10 to 90 over a range of 0 of a factor of 2 the bounds of this range increase with grain size di so that at a given 0 sizes over a range of a factor of 4 are in a state of partial transport fractional transport rates are independent of di for fully mobilized fractions and decrease rapidly with di for partially mobile fractions partial transport is associated with substantial transport rates of finer fully mobile sizes limits both the rate and size distribution of grain exchange with the bed subsurface and may be the dominant transport condition in many gravel bed rivers

thermal curved fragments a method for identifying anthropogenic fire in the archaeological record abstract the archaeology of fire is a developing field one challenge centers on equifinality distinguishing the affects of wildfire versus anthropogenic fire especially where evidence for control of fire by humans in the early pleistocene remains debated there is little consensus regarding what constitutes clear evidence of human control another concern is preservation bias which reduces clearly identifiable archaeological signatures of fire in this paper we argue that a peculiar lithic angular fragment termed thermal curved fragment tcf exhibits statistically distinct quantitative evidence of the confluence of human knapped stone tools and exposure to a high energy long duration ground level fire i e campfires experimental tcfs are described and compared to unfired knapping debitage natural exfoliations and suspected archaeological tcfs the provenance of these archaeological specimens has previously been argued to infer hominin controlled fire at 1 5 1 6 ma at the koobi fora formation we also present data from experiments exposing stone flakes arranged as scatters of similar raw materials to those found in the koobi fora formation to usda prescribed burns in a variety of conditions approximating landscape fires results indicate that tcfs are formed specifically where previously knapped stone is exposed to high energy ground level fires similar to those seen in ethnographic campfires our analysis indicates that tcfs can be used in conjunction with other lines of evidence indicating the presence of anthropogenic fire in the archaeological record

acoustic bed velocity and bed load dynamics in a large sand bed river 1 development of a practical technology for rapid quantification of bed load transport in large rivers would represent a revolutionary advance for sediment monitoring and the investigation of fluvial dynamics measurement of bed load motion with acoustic doppler current profilers adcps has emerged as a promising approach for evaluating bed load transport however a better understanding of how adcp data relate to conditions near the stream bed is necessary to make the method practical for quantitative applications in this paper we discuss the response of adcp bed velocity measurements defined as the near bed sediment velocity detected by the instrument s bottom tracking feature to changing sediment transporting conditions in the lower missouri river bed velocity represents a weighted average of backscatter from moving bed load particles and spectral reflections from the immobile bed the ratio of bed velocity to mean bed load particle velocity depends on the concentration of the particles moving in the bed load layer the bed load layer thickness and the backscatter strength from a unit area of moving particles relative to the echo strength from a unit area of unobstructed bed a model based on existing bed load transport theory predicted measured bed velocities from hydraulic and grain size measurements with reasonable success bed velocities become more variable and increase more rapidly with shear stress when the transport stage defined as the ratio of skin friction to the critical shear stress for particle entrainment exceeds a threshold of about 17 this transition in bed velocity response appears to be associated with the appearance of longer flatter bed forms at high transport stages

effects of storminess sand supply and the north atlantic oscillation on sand invasion and coastal dune accretion in western portugal holocene forested coastal dunes fringe the atlantic coast of western portugal mapping of dunes in the field and using air photographs shows a range of forms reflecting dominant northwest and westerly onshore wind regimes planting of maritime pine forests in the thirteenth and twentieth centuries was initiated because of sand invasion causing problems for human settlement and agriculture early holocene dunes have a well developed podsol and date to 9 7 and 8 2 ka suggesting at least some of these sands may have been emplaced during a global cooling event significant transgressive dune accretion at 2 2 and 1 5 ka implies abundant sand supply and strong onshore winds the most recent dune building period dates to ad 1770 1905 and coincides with a predominantly negative winter north atlantic oscillation index naoi accretion of dunes along the portuguese coast appears out of phase with dune development in southwest france which may reflect different atlantic storm tracks driven by changes in the domin

wind regimes and aeolian transport in the great basin u s a abstract the modern great basin of the interior western united states is characterized by surface winds with considerable spatial and temporal variabilities wind records from the second half of the 20th century for 12 great basin localities analyzed with standard aeolian sediment transport methods developed elsewhere in the world reflect this complexity the drift potential dp for aeolian deposits is generally moderate dp 200 400 in the western great basin and weak dp 300 at the eastern edge of the great basin where the dominant prevailing wind direction is south southwesterly both dp and resultant drift direction rdd are consistent with synoptic meteorological observations of the evolution of cold fronts in the great basin meteorological observations show that effective winds to produce dunes are most commonly the result of late winter early spring cyclogenesis there has been considerable temporal variability of dp in the latter half of the 20th century most of the great basin has experienced decreasing wind strength since 1973 consistent with recent studies of wind strength in north america and elsewhere dune morphology matches both localized rdd and temporal variations in dp reasonably well in the great basin the results demonstrate that local topography can have an important influence on wind directionality thus providing a cautionary note on the interpretation of dune morphology in the paleoclimatic and stratigraphic record

tracer pebble movement along a concave river profile virtual velocity in relation to grain size and shear stress over 1400 tracer pebbles 16 256 mm in diameter were tracked for 2 years in six reaches of allt dubhaig scotland a small gravel bed river along which shear stress and bed surface grain size decrease toward a local base level pebble movement was size selective both within and between reaches within reaches the decrease in mean travel distance with increasing grain size is strongest in the coarse tail of the size distribution particle shape has a minor secondary effect a nondimensional grain velocity averaged over the duration of competent flow is used to compare different size classes and reaches over 90 of its variance is explained by relative grain size and reach shields stress the pattern of size selectivity is consistent with single event tracer results elsewhere bedload trap data from our distal reach and the concept of partial mobility it provides a mechanism for strong downstream fining by selective transport and deposition along rivers in which stress declines toward base level the nondimensional prediction equation for grain velocity may be of use in other rivers but requires testing

heat treatment of polish flints abstract in poland three types of flint chocolate spotted and banded were intensively mined from the terminal palaeolithic to the early bronze age although heating of flint to improve its flaking properties was practised across the world from 110 000 years ago to the recent particularly in southwestern europe heat treatment of flint in poland is known from only two sites experimental studies showed that controlled heat treatment of polish flints causes subtle variable changes in colour but a consistent marked increase in lustre on fractured surfaces which should make heat treated artefacts easy to recognise in the polish archaeological record heat treatment also causes a substantial reduction in the fracture toughness of all tested polish flint types and a concomitant increase in flakeability the effect is greatest for banded flint due to its initially higher fracture toughness the decrease in fracture toughness is caused by recrystallisation allowing fractures to propagate more easily in banded flint the average crystal size increases and within chocolate and spotted flint the fibrous chalcedony patches become more granular although the flaking properties of banded flint are improved markedly by heat treatment the procedure was applied only occasionally by prehistoric flintknappers to this material banded flint was preferentially used for completely polished axes and only rarely for blades because chocolate and spotted flints are available close to the banded flint mines these flint types have far superior flaking properties and were extensively used for blade manufacture spotted flint is generally less suitable for heat treatment it is subject to explosive thermal spalling due to its abundant calcite inclusions although heat treatment improves the flaking properties of chocolate flint heated chocolate flint is rare in the polish archaeological record probably because high quality flint was so abundant in poland

bedload transport of fine gravel observed by motion picture photography motion pictures taken at duck creek a clear stream 6 5 m wide and 35 cm deep near pinedale wyoming provide detailed quantitative information on both the modes of motion of individual bedload particles and the collective motions of large numbers of them bed shear stress was approximately 6 pa 60 dynes cm 2 which was about twice the threshold for movement of the 4 mm median diameter fine gravel bed material and transport was almost entirely as bedload the displacements of individual particles occurred mainly by rolling of the majority of the particles and saltation of the smallest ones and rarely by brief sliding of large angular ones entrainment was principally by rollover of the larger particles and liftoff of the smaller ones and infrequently by ejection caused by impacts whereas distrainment was primarily by diminution of fluid forces in the case of rolling particles and by collisions with larger bed particles in the case of saltating ones the displacement times averaged about 0 2 0 4 s and generally were much shorter than the intervening repose times the collective motions of the particles were characterized by frequent brief localized random sweep transport events of very high rates of entrainment and transport which in the aggregate transported approximately 70 of the total load moved these events occurred 9 of the time at any particular point of the bed lasted 1 2 s affected areas typically 20 50 cm long by 10 20 cm wide and involved bedload concentrations approximately 10 times greater than background the distances travelled during displacements averaged about 15 times the particle diameter despite the differences in their dominant modes of movement the 8 16 mm particles typically travelled only about 30 slower during displacement than the 2 4 mm ones whose speeds averaged 21 cm s 1 particles starting from the same point not only moved intermittently downstream but also dispersed both longitudinally and transversely with diffusivities of 4 6 and 0 26 cm 2 s 1 respectively the bedload transport rates measured from the films were consistent with those determined conventionally with a bedload sampler the 2 4 mm particles were entrained 6 times faster on finer areas of the bed where 8 16 mm particles covered 6 of the surface area than on coarser ones where they covered 12 even though 2 4 and 4 8 mm particles covered practically the same percentage areas in both cases the 4 8 and 8 16 mm particles in contrast were entrained at the same rates in both cases to within the statistical uncertainty the rates of distrainment balanced the rates of entrainment for all three sizes and were approximately proportional to the corresponding concentrations of bedload

heating of flint debitage from upper palaeolithic contexts at manot cave israel changes in atomic organization due to heating using infrared spectroscopy abstract the heat treatment of flint is known to change its mechanical properties and improve its fracture behaviour during knapping here we examine 20 flint artifacts from upper paleolithic contexts from manot cave israel using fourier transform infrared spectroscopy and compare them to geogenic flint beds from the walls inside the cave and from outcrops just above the cave we show that the 512 and 467 cm 1 peaks are broader in most of the flint debitage pieces as compared to the geogenic flint and that broadening of these peaks occurs when geogenic flint from the cave wall is heated we also present an empirical simple method to monitor these changes

bed load transport i mechanical characteristics this paper deals with the mechanical characteristics of saltation of bed load transport in flowing water experiments have been carried out by means of high speed photography and advanced data processing techniques taking saltation as the mode of bed load transport systematic analysis has been made with regard to the forces acting on grains and the variation of their magnitudes along the saltation trajectories to obtain the kinematic and dynamic properties of these grains moveover the relations between magnitudes of saltation parameters and flow intensity are attained from the measured data some parameters in bagnold s theory of bed load transport are also discussed