the abrasion of modern and archaeological bones by mobile sediments the importance of transport modes abstract fresh weathered archaeological and fossilized bones were subjected to a series of abrasion experiments using fine sand in an annular flume in order to link bone surface abrasion to flow regimes and sediment transport modes compare these effects on bones of different states and quantify the extent and types of wear occurring flow velocities were chosen to replicate the predominant transport modes of bedload saltation and suspension comparative scanning electron microscopic image analysis was performed to assess the degree and type of wear occurring on each bone type for the different transport modes over a range of exposure periods from 24 to 72 h these preliminary investigations have shown that both the amount and type of wear experienced was related to the bone type duration of exposure and the mode of sediment transport with wear being the result of deformation rather than cutting wear the formation of scour pits in the sand bed on the upstream side of the bone samples significantly reduced wear and appears to be an important control mechanism for impact related wear that has been overlooked until now

chemical sedimentology and paleoenvironmental history of lake olduvai a pliocene lake in northern tanzania lake olduvai was a saline highly alkaline closed basin lake in which lacustrine sediments of bed i and lower bed ii of olduvai gorge were deposited between ca 1 92 and 1 70 ma the lake consisted of a lacustrine area the central basin cb surrounded by lake margin terrain that was alternately flooded and dried the lacustrine deposits consist largely of authigenic clay and carbonate minerals zeolites k feldspar chert and pyrite claystones of the cb and most of the eastern lake margin elm terrain consist chiefly of mg rich authigenic illite smectite and interlayered illite smectite i s these clays were formed penecontemporaneously with detrital clay deposition by interaction of the detrital clays with the saline highly alkaline water the lake olduvai clays average 65 70 mg 2 sio 2 and alkali ions from lake water and the remaining 30 35 is detrital clay lacustrine clays of the elm indicate that this area was flooded by saline water for substantial periods of time hominids occupied the elm at times of lower lake levels when the clays were dried calcite is the most abundant carbonate mineral and occurs chiefly as sand size euhedral crystals dispersed in claystone and less commonly as calcite crystal limestones and nodules the sand size calcite crystals were formed diagenetically at shallow depths possibly from a gaylussite and or micritic calcium carbonate precursor dolomite occurs chiefly in the form of dolostones some of which are probably of replacement origin the oxygen isotope composition of lake water and pore fluid of the cb varied over 11 as determined from calculated delta 18 o h 2 o values of authigenic minerals clay minerals were formed chiefly in the more saline waters sand size calcite crystals were generated mostly from less saline pore fluids and limestone nodules were formed chiefly from dilute pore fluid dolostones were formed from fluids of varying salinity hydrogeology of the central basin was complex and postdepositional fluid movements are documented by differing delta 18 o h 2 o values for different authigenic minerals of the same samples pore fluids moved within the lake deposits for a considerable period of time after deposition as shown by 18 o values of quartz and k feldspar formed at different times downward flow of lacustrine fluids is indicated by zeolitic alteration of the underlying tuffaceous alluvial deposits lake olduvai became overall shallower during the deposition of bed i and the subaerial exposure increased leading to occasional playa conditions these changes very likely resulted from increasing aridity and tectonic activity the lake that deposited lower bed ii was larger than that responsible for upper bed i and episodes of wetter climate alternated with drier periods in which salinity and probably temperatures were higher than in the bed i lake

a spring and wooded habitat at flk zinj and their relevance to origins of human behavior the 1959 discovery of the hominin fossil zinjanthropus boisei brought the world s attention to the rich records at olduvai gorge tanzania subsequent excavations of archaeological level 22 flk zinj bed i uncovered remains of homo habilis and a high density collection of fossils and oldowan stone tools the occurrence of this unusual collection of bones and tools at this specific location has been controversial for decades we present paleoecological data that provide new insights into the origin of flk zinj our recent excavations 200 m north of the site uncovered a 0 5 m thick tufa mound draped by tuff ic in the same stratigraphic horizon as level 22 stable isotope analyses indicate that the carbonates were deposited by a freshwater spring phytolith analysis of the waxy clay under tuff ic revealed abundant woody dicotyledon and palm phytoliths indicating that the site was wooded to densely wooded the time equivalency and close physical proximity of the two environments indicate the two are related this study has provided the first documented evidence of springs in bed i and these data have important implications for the interpretation of hominin behavior in meat acquisition and the ongoing debate on scavenging versus hunting

new excavations at the flk zinjanthropus site and its surrounding landscape and their behavioral implications renewed excavations at flk zinj and its surrounding landscape have yielded valuable information regarding its paleoecological situation and the prehistoric behavioral function of the site the density of materials at the main cluster of the site excavated by leakey contrasts with the bone and lithic scatters surrounding the site the location of flk zinj situated a few hundred meters away from a freshwater spring would have enabled hominins access to water plants and game the appeal of the spot for hominins also explained by the presence of a wooded habitat is confirmed by inferences of its redundant use prior and during the formation of the flk zinj paleosol as witnessed by materials accumulated both under and on the waxy clay deposit that constitutes the flk zinj stratum the single cluster nature of the site indicates central place behavior and evidence is provided that hominins occupied the site at a time of very low predation hazards in the area

physical modelling of gelifluction and frost creep some results of a large scale laboratory experiment an experimental slope was constructed in a 5 m 5 m square refrigerated tank the slope was formed of four sections each consisting of regolith soil collected from a distinct bedrock lithology the four lithologies utilized were granite limestone mudstone and slate the slope was subjected to freezing and thawing from the surface downwards water was supplied at the base of the soil during freezing frost heaving and surface downslope soil movement were determined after each of 15 freezing cycles and the profiles of soil movement with depth for each soil type were measured at the end of the 15th cycle the experimental soils were non cohesive those derived from granite and limestone were respectively sandy and gravelly in texture while those derived from mudstone and slate were silt rich mass movement in the granite and limestone soils was due mainly to frost creep and was associated with the growth of needle ice in the mudstone and slate soils gelifluction was dominant as a result of high moisture contents caused by the melting of segregation ice mean per cycle rates of downslope soil transport for the granite limestone mudstone and slate soils were 5 8 cm3 cm 1 6 9 cm3 cm 1 21 2 cm3 cm 1 and 31 2 cm3 cm 1 respectively units referring to the volume of soil passing a unit width of slope per cycle mass movement rates were shown to be strongly related to the silt content of the soils

combined quantification of anisotropy and inhomogeneity of magmatic rock fabrics an outcrop scale analysis recorded in high resolution abstract magmatic mineral distribution patterns in a syntectonic syenite pluton have been recorded at high resolution over several square metres on quarried faces the anisotropy and inhomogeneity of k feldspar and mafic mineral distribution patterns have been quantified using two methods originally based on fractal geometry 1 map counting based on box counting illustrates an inhomogeneity on the decimetre to metre scale and highlights diffuse structures that can be related to mafic schlieren or felsic dykes that are not visible on the rock surface 2 we have developed a mapping of rock fabric anisotropy morfa method that leads to the detection of further magmatic structures that are not visible in the field with morfa a magmatic lineation and its variation over large areas is determined as well as fabrics on the decimetre to 1 m scales which possibly represent flow or fracture structures in the crystallising magma

taphonomy of some articulated skeletal remains transport potential in an artificial environment flume experiments demonstrated that disarticulated bones did not display the same behaviour when combined as articulated elements the character of movement and rates of movement were recorded skeletal elements were identified as displaying either a transportable or a non transportable potential some of which were common to all three species that were tested the experiments demonstrated that articulated bones displayed a greater transport potential and that in one species the rate of movement was significantly faster than when disarticulated it is suggested that the taphonomic history of a fluvial transported assemblage could be misinterpreted if the bones were treated as a mixture of individually transported elements

leopards as taphonomic agents in dolomitic caves implications for bone accumulations in the hominid bearing deposits of south africa it has been hypothesised that leopards were significant contributors to the bone accumulations of the plio pleistocene hominid bearing caves of south africa interpretations of leopard activity in these fossil caves were previously based upon reports of modern leopard behaviour in areas of southern africa that were lacking in caves in 1991 a leopard lair with an accompanying bone accumulation was discovered in a dolomitic cave on the john nash nature reserve south africa all of the bones in this cave could be unambiguously attributed to the activity of one individual leopard over a 1 year period the resulting bone assemblage indicates that when available leopards will preferentially utilise the deep recesses of caves to the exclusion of trees when feeding and that the size of prey leopards are capable of capturing killing and transporting has previously been underestimated the implications this may have for understanding the accumulation of fossils in the hominid bearing caves of south africa are that bones derived form leopards consuming prey in trees probably did not contribute significantly to the assemblages and further that it is not necessary to invoke sabre tooth cat involvement for the larger animals found in these assemblages this modern cave probably represents a more appropriate model for the accumulation of bones in the fossil caves of the sterkfontein valley and the assemblage is being continually monitored to view any and all taphonomic alterations that are occurring

was flk north levels 1 2 a classic living floor of oldowan hominins or a taphonomically complex palimpsest dominated by large carnivore feeding behavior abstract from excavation at flk north levels 1 2 in 1960 1962 mary leakey reported approximately 1200 oldowan artifacts and 3300 large mammal fossils as a hominin living floor preliminary taphonomic analysis by bunn seemed supportive based on the presence of some cut marked bones the concentration of several dozen bovid individuals and the relative abundance of limbs and mandibles over other axial elements recent taphonomic analysis of leakey s entire fossil assemblage by dominguez rodrigo and barba however documents a minor hominin role at the site contrasted to the dominant role of carnivores felids brought prey animals hyenas scavenged from abandoned felid meals at different times hominins butchered several bovids and discarded artifacts at this dynamic location since 2006 renewed excavations at flk north and other sites by the olduvai paleoanthropology and paleoecology project toppp have expanded artifact and fossil samples and implemented new analytical approaches to clarify taphonomic histories of the olduvai paleolandscape at flk north 1000 new large mammal fossils from levels 1 to 2 show minimal butchery evidence amid abundant evidence of carnivore gnawing fracture rodent gnawing and sediment abrasion to help guide future excavation and analyses we have developed several alternative working hypotheses of site formation

sampling surface orientation and clast macrofabric in periglacial colluvium to isolate the influence of sampling surface orientation on the macrofabric of periglacial colluvial deposits clast orientation measurements were obtained from seven paired horizontal and vertical exposures in turf banked solifluction lobes on niwot ridge colorado front range most samples form moderately strong upslope plunging clusters aligned with the local slope orientation fabrics obtained from vertical faces were stronger than those from horizontal exposures in six of the pairs near horizontal sampling surfaces yield less biased results than vertical exposures owing to operator perceptions procedural difficulties and the relative thinness of the layer affected by colluvial processes sampling procedures must be standardized before comparative studies of colluvium can yield reliable results copyright 2001 john wiley sons ltd

solifluction induced modifications of archaeological levels simulation based on experimental data from a modern periglacial slope and application to french palaeolithic sites the taphonomic study of petit bost croix de canard and cantalouette ii three palaeolithic sites that were recently discovered near perigueux and bergerac dordogne france in a colluvial context has enlightened the difficulty of adequately appreciating the relative role of cultural and natural processes in site spatial patterning periglacial solifluction was thought to have played a significant role in site formation because the nature of the modifications induced by solifluction was still poorly understood a simulation was made using data of soil movement recorded at la mortice french southern alps 3100 m in elevation in a modern periglacial environment the results show that for a knapping location the first steps of deformation are typified both by a downslope translation of the location center and by an anisotropic diffusion of the artifacts the knapping spot becomes elongated along the slope with a dense relic concentration of artifacts in the upslope portion this type of pattern has been obtained after 100 to 200 years of simulated displacement according to the climatic and soil conditions that characterise the la mortice site the ultimate stages of deformation show that the artifact distribution tends to homogenise on larger surfaces and resemble a random distribution the ability of the simulated patterns to closely fit those observed in archaeological contexts is evaluated at three sites from south western france at petit bost the hypothesis of limited solifluction explains accurately the association of both cultural artifact concentrations and natural artifact preferred orientation features at croix de canard long term solifluction can be proposed by contrast the simulated patterns do not describe the structures observed on the steeper slopes at cantalouette ii where the knapping spot transforms into distinct solifluction lobes

autochthony and orientation patterns in olduvai bed i a re examination of the status of post depositional biasing of archaeological assemblages from flk north flkn recent excavations at flk north olduvai gorge tanzania have produced new information on the orientation of archaeological materials at various levels of the site this information includes the uniform distribution of material azimuths which contrasts with previous inferences of highly patterned orientations of materials in the bed i archaeological sites those previous inferences of patterned material orientations are based on mary leakey s 50 year old drawings of artifact and fossil bone distribution but are not verified by our precise measurements of archaeological objects made in situ nor do those previous results agree with the general lack of geological geomorphological and or taphonomic data that would indicate significant post depositional movement of archaeological materials in the sites we argue here that leakey s drawings are incomplete only portions of each assemblage were drawn and inaccurate in their representation of the original locations shapes and orientations of most archaeological specimens this argument is supported by several important mismatches in object representations between a photograph taken of a small portion of the flk 22 zinjanthropus site floor before the removal of the archaeological items and the sketch of the same area drawn by leakey thus we conclude that primary orientation data of excavations i e direct measurements taken from items generated prior to object removal are the only valid indicators of the relative isotropy or anisotropy of these important paleoanthropological assemblages

the impact of periglacial processes on palaeolithic sites the case of sorted patterned grounds during the last glaciation western europe witnessed recurrent millennial scale episodes of periglacial climates that had significant impact on palaeolithic site preservation after a review on the genesis and climatic meaning of sorted patterned grounds examples of polygons stripes and stone banked solifluction lobes taken from archaeological contexts are described sorted features in palaeolithic sites imply that caution should be taken in site patterning analysis for reconstructing past human behaviours since spatial alteration of the original anthropogenic pattern took place on low gradients artefact movements remain limited but may increase dramatically on slopes when solifluction adds to sorting processes although these features are widespread in modern periglacial environments archaeological examples remain scarce multiple factors are probably involved including lack of knowledge of periglacial processes and landforms by archaeologists leading to misinterpretation but also more or less complete obliteration of surface features by sedimentary processes upon burial however it is assumed that scarcity of clear anthropogenic patterning in french palaeolithic sites before the late glacial is due for a large part to post depositional disturbance by periglacial processes

taphonomy of a middle miocene autochthonous forest assemblage ngorora formation central kenya abstract a 12 6 million year old forest assemblage of leaves twigs and rare fruit is preserved in the ngorora formation of central kenya the assemblage is autochtonous preserved in airfall tuff and represents well the diversity heterogeneity and richness of the original forest the herbaceous component not usually preserved in paleobotanical assemblages is present nearest neighbor analysis and mapping of the vertical distribution of plant organs indicates that leaves and twigs are preserved near the parent plant and that there is no apparent size weight or species bias in deposition of these remains leaves occur isolated in clusters or attached to branches and fell directly to the ground as a result of ashfall most falling very soon after ashfall commenced the absence of upright trunks and large stems is probably due to post depositional weathering which may also be responsible for the absence of a leaf litter layer however leaf litter may have been absent at the time of ash deposition

rates and processes of periglacial solifluction an experimental approach cold room physical modelling of periglacial solifluction processes on an experimental slope of 12 is described and data on soil temperatures surface frost heave thaw consolidation downslope soil movement and porewater pressures over seven freeze thaw cycles are presented these data are analyzed in the context of laboratory determination of the rheometry of the experimental soils at high moisture contents it is concluded that the observed thaw induced solifluction represents pre failure soil shear strain and results from loss of strength due to the combined effects of raised porewater pressures during thaw consolidation and upward seepage pressures as water flows towards the surface away from the thaw front an investigation of the rheometry of thawing soils offers the prospect of an analytical model to predict rates and depths of periglacial solifluction 1997 by john wiley sons ltd

provenance analysis of oligocene autochthonous and allochthonous coralline algae a quantitative approach towards reconstructing transported assemblages abstract the oligocene shallow water carbonates of the lower inn valley tyrol northern calcareous alps contain a rich coralline algal flora these carbonates are known from two distinct settings 1 autochthonous limestones and 2 debris flows intercalated with deeper water marls the carbonate facies are dominated not only by crustose coralline algae corallinaceae rhodophyta but also by smaller and larger benthic foraminifers bryozoans corals as well as lithoclasts of triassic origin five species of coralline algae are identified and described in detail lithoporella melobesioides lithothamnion sp a lithothamnion sp b mesophyllum sp and sporolithon sp the distribution of algal taxa shows distinct relationships to non algal biota and substrates l melobesioides preferably encrusts other coralline algae lithothamnion sp a is found encrusting bryozoans lithothamnion sp b encrusts corals while mesophyllum sp grows directly on fine grained soft substrates besides the fact that algal taxa reveal close relationships to other components it can also be shown that algal assemblages are highly correlated to carbonate facies types hierarchical cluster analysis based on the relative abundance of taxa reveals five coralline algal assemblages showing distinct distribution patterns among carbonate facies while two of the assemblages are restricted to the debris flows the other three were found in both debris flows and autochthonous occurrences a correlation between algal assemblages and carbonate facies allows the following conclusions to be made 1 both coralline algal taxa in particular and algal assemblages as a whole show distinct relations to water depth herein referred to as a summary of light conditions and hydrodynamic energy and substrate relationships this makes them potentially valuable indicators for palaeoecological reconstructions 2 most of the coralline algal assemblages in allochthonous occurrences i e debris flow can be traced back to facies patterns in autochthonous occurrences this indicates that a thorough microfacies analysis combined with a systematic study of specific components can be very useful in the reconstruction of palaeoenvironments even if these are not preserved in their original context 3 some of the coralline algal assemblages within debris flows cannot be traced to autochthonous facies and do not seem to reflect primary facies compositions as they contain an atypical mixture of algal taxa and other components these are characterised by a relatively high abundance of lithoclasts usually 20 of the components and a high degree of fragmentation of coralline algae thalli

fabric of palaeolithic levels methods and implications for site formation processes fabric analysis in archaeological contexts i e the study of the orientation and dip of artefacts has been significantly improved during the last decade mainly with respect to the statistical treatment of data the development of a reference base for natural sedimentary processes as well as the increased number of data for palaeolithic levels these works show that fabrics are an efficient tool for assessing site formation processes fabrics allow discrimination between i undisturbed or minimally disturbed levels ii levels that have undergone strong pedoturbations due to biological activity or to shrinking and swelling of clayey sediments and iii levels that have been significantly reworked by slope processes such as periglacial solifluction or overland flow however in the present state of knowledge fabrics do not allow precise estimation of the degree of perturbation if not associated with other archaeological and geological criteria from the set of data on french palaeolithic sites used here it is demonstrated that slope dynamics and particularly solifluction for sites predating the late glacial may have played an important role in site formation

one bone two bones wet bones dry bones transport potentials under experimental conditions flume experiments demonstrated that bones had varying hydraulic transport potentials depending on whether the bones were wet or dry articulated or disarticulated when placed into a water flow dry and articulated bones demonstrated the greatest transport potential while wet and disarticulated bones demonstrated the least the velocity at which bones were transported was plotted against a range of attributes such as the shape weight volume and density of the bones with varying degrees of success although several attributes did prove to be significant as indicators of bone transport potential no single attribute emerged as more useful than another

differential frost heave and sorted patterned ground field measurements and a laboratory experiment abstract small scale sorted stripes and circles dominate over the alpine regions in the upper engadin swiss alps most of these features are spaced at less than 30 cm intervals by coarse margins shallower than 5 cm monitoring of sorted stripes indicates that shallow diurnal freezing often induces differences in amount and timing of frost heave by needle ice growth between fine and coarse stripes while deeper diurnal freezing and seasonal freezing rarely differentiate heave amounts of the two materials a laboratory simulation is designed to explore the contribution of differential frost heave to the sorting process at the monitoring site the device consists of a fine part loam and a coarse part a granule layer mounted on loam freeze thaw tests with a granule mantle of 0 5 2 5 and 5 cm thick demonstrate that the heave amount on the coarse part is greatly reduced by the 5 cm thick mantle and that the coarse part always heaves later but subsides earlier than the fine as a result of this time lag in frost heaving lateral soil movement towards the coarse part is generated within the surficial soil differential heave associated with diurnal freeze thaw cycles is capable of sorting of the top 5 cm of soil

cooling history of atlantis bank oceanic core complex evidence for hydrothermal activity 2 6 ma off axis 1 we report 26 u th he zircon ages from atlantis bank southwest indian ridge which constrain time scales and rates of lower crustal cooling in ultraslow spreading oceanic crust in this setting samples from the detachment fault surface indicate that denuded oceanic crust cooled rapidly 1200 c ma consistent with existing models for the cooling of oceanic crust u th he zircon ages from samples collected along n s and e w trending faults scarps record young ages inconsistent with standard cooling models for lower oceanic crust these samples have a mean u th he zircon age 2 6 ma younger than their corresponding igneous crystallization ages and record cooling through 200 c well outside the rift valley similar anomalously young ages are recorded by zircon sphene and apatite fission track data from odp hole 735b we interpret these young ages as recording an off axis thermal heating event associated with localized high temperature 300 c hydrothermal fluid flow resulting from underplated mafic magmas

effect of mechanical interactions on the development of shape preferred orientations a two dimensional experimental approach abstract modifications in the development of preferred orientations of rigid particles due to mechanical interactions between particles are studied experimentally in two dimensions experiments in both pure shear and simple shear were performed and the results analysed using an easy and fast new automatic method for increased concentration of rigid particles the rotation of individual particles may be slowed down or even stopped due to collisions or disturbance of the flow in the matrix caused by neighbours in coaxial flow the fabric intensity is consequently reduced in simple shear flow the fabric evolution is no longer cyclic the intensity is on average weaker and the fabric axis rotates asymptotically toward the shear plane in the case of preferred orientations of particles having a low aspect ratio 2 5 the fabric rotates through the shear plane then undergoes a reverse rotation and rotates toward the shear plane again in the light of these experimental results we emphasize that quantification of finite strain based on such fabrics may lead to significant underestimates and calculated values should be taken as minimum estimates the kinematic significance of concentrated rigid particle preferred orientations in rocks is modified by interactions between particles techniques for qualitative or quantitative kinematic analysis may become unreliable for simple shear flows the concentrated population fabrics show an angular behaviour close to that of passive markers they tend to align parallel to the shear plane in simple shear flow