volcanism in the afar rift sustained by decompression melting with minimal plume influence continental breakup is caused by some combination of heating and stretching1 2 the afar rift system in africa is an example of active continental rifting where a mantle plume probably weakened the lithosphere through thermal erosion and magma infiltration however the location and degree of plume influence today are debated2 3 here we use seismic s to p receiver functions to image the mantle structure beneath afar we identify the transition between the lithosphere and underlying asthenosphere at about 75 km depth beneath the flanks of the continental rift however this boundary is absent beneath the rift itself and we instead observe a strong increase in seismic velocities with depth at about 75 km we use geodynamic modelling to show that the velocity increase at this depth is best explained by decompression melting of the mantle in the absence of a strong thermal plume so although the absence of mantle lithosphere beneath the rift implies a plume may have once been active we conclude that the influence of a thermal plume directly beneath afar today is minimal

seismic imaging of melt in a displaced hawaiian plume the precise location of the mantle plume upwelling beneath hawaii is debated seismic data reveal a thick layer of melt in the mantle beneath western hawaii implying that the upwelling plume may be deflected around an ancient resistive root beneath the island

unveiling the taphonomy of elusive natural tank deposits a study case in the pleistocene of northeastern brazil abstract fossiliferous natural tanks are a singular type of sedimentary deposit restricted to northeastern brazil which usually preserves a diversified late pleistocene vertebrate fauna their fossil assemblages are taxonomically well known but their taphonomy is poorly understood this work presents a detailed taphonomic analysis of a tank deposit from jirau site ceara state northeastern brazil to improve understanding of the processes that influenced fossil deposition and preservation in natural tanks and to shed light on paleoecological and paleoenvironmental aspects related to the late pleistocene vertebrate fauna from northeastern brazil tank deposits from different localities were also compared to figure out potential taphonomic patterns among them additionally comparisons with other brazilian pleistocene deposits and other debris flow deposits bearing vertebrates were undertaken the study revealed the predominance of the megamammal eremotherium laurillardi in the deposit which we attributed to its abundance in late pleistocene biocoenosis as well as bone resistance scarcity of non mammalian vertebrates is likely related to their paucity in late pleistocene biocoenosis time averaging was evidenced by the co occurrence of different weathering petrographic and color patterns and may have affected the ontogenetic profile of the accumulation relative to the original biocoenosis analyses of weathering stages tooth and trample marks indicate wide exposition of the thanatocoenosis before burial abrasion and petrographic patterns allow reworking in the assemblage to be inferred permineralization and substitution are the fossilization processes observed taphonomy indicates that floods deposited clasts and bioclasts in the tank under an arid or semiarid climate in a debris flow regime comparison with other tank deposits revealed several similar taphonomic features and differences related to sedimentology and stratigraphy taphonomic similarities suggest rather homogeneous environmental conditions in the northeastern brazil during the late pleistocene as previously suggested by taxonomic studies comparison with other brazilian pleistocene deposits shows that tanks have more temporal fidelity than caves coastal and some fluvial deposits the jirau vertebrate accumulation was produced by the reworking and transport of skeletal elements accumulated in a nearby thanatocoenosis and is similar to other better known debris flow hosted vertebrate accumulations

beached penguins on the atlantic coast in the pampas region of argentina taphonomic analysis and implications for the archaeological record abstract this study evaluates a modern natural deposit of magellanic penguin remains in the coast of the pampas region and discusses the regional availability of this resource for prehistoric hunter gatherer populations as well as the potential for the natural incorporation of this species into the archaeological record the penguin assemblage from the surveyed area which results from beaching during seasonal migration consists of disarticulated bones articulated bones and carcasses in the skeletal representation there is a strong predominance of limbs and shoulder girdle elements natural processes such as weathering sedimentary abrasion and predator action highly affected the preservation of specimens even though penguins could have been a potential prey for hunter gatherer populations of the pampas region our results suggest that they were not an attractive food resource given their scarcity and poor nutritional condition the spatial distribution of modern penguin remains and the archaeological evidence suggest that the natural incorporation of bones from this seabird into surface archaeological sites can be expected in the backshore and deflated interdunes however the chances of long term burial and bone preservation are low thus the formation of a stratigraphic archaeological site containing intrusive penguin remains in these settings is unlikely

new data from ambrona closing the hunting versus scavenging debate abstract this paper presents a taphonomic analysis of the faunal assemblages from the 1993 1999 excavations at ambrona spain directed by santonja and perez gonzalez the purpose of the new excavations was to achieve a better understanding of the stratigraphic sequence general geology sedimentary context and processes of accumulation of materials our objectives are to evaluate the opposing interpretations of the hominid subsistence activities at the site proposed by freeman and binford the faunal and lithic remains are found in different sedimentary contexts an alluvial fan lacustrine muds fluviatile clay sands and channel deposits faunal remains in the lacustrine muds are often but not always in primary context remains of elephant and deer carcasses may be found in partial articulation or proximity and represent natural occurrences without any clear evidence of hominid intervention in other contexts the faunal remains are occurrences of single anatomical elements either displaced by water or left isolated in situ there are no carnivore marks bones and stone artifacts show varying degrees of mechanical abrasion due to water transport limited evidence of human action on bones is provided by a few sem verified cutmarks and some anthropic fractures they document butchery of various animals including elephants we cannot prove hunting but we can definitely reject binford s idea of marginal scavenging of medium size ungulates from carnivore kills ambrona is a complex mix of natural and human components the remnant of a natural landscape regularly visited by hominids who transported some artifacts from nonlocal raw material sources and had an organized approach to meat acquisition however strong evidence of elephant hunting is provided only by sites younger than ambrona

experimental examination of animal trampling effects on artifact movement in dry and water saturated substrates a test case from south india this paper presents the motivation procedures and results of an experiment that examines short episodes of animal trampling in dry and water saturated substrates in south india while horizontal artifact displacement was similar to that modeled by other trampling experiments vertical artifact displacement in water saturated substrates was greater than any reported experiment to date the toolstone used in this experiment a silicious limestone exhibited minimal damage after trampling artifact inclination patterning appeared to be a potentially diagnostic middle range marker of trampling in water saturated substrates given the abundant number of paleolithic sites that are located on flat open surfaces near water bodies or experience monsoonal climatic regimes we propose that future excavations should measure artifact inclination on a regular basis

dating of modified femora of extinct dwarf hippopotamus from southern madagascar implications for constraining human colonization and vertebrate extinction events two significant events in the late holocene history of madagascar were a the arrival of people and b the loss of nearly two dozen species of land vertebrates in the socalled subfossil extinctions the consensus is that the faunal losses occurred shortly subsequent to human arrival but the timing of these events is poorly constrained the minimum age for initial human presence on the island may now be set at approximately 2000 bp on the basis of ams 14c dates for human modified femora of extinct dwarf hippos from sw madagascar assuming that this date also marks the beginning of deleterious human interactions with the subfossil fauna and assuming that this fauna became completely extinct by 900 bp the width of the anthropogenic extinction window may have been as long as c 1000 a this estimate nearly twice the length of previous ones is close to the unadjusted minimum for the duration of the terminal pleistocene extinction event in the americas whether or not this length of time comports with theoretical expectations of a blitzkrieg pattern of losses is uncertain but greater refinement in dating the end of the subfossil extinctions is unlikely to produce radically shorter estimates of duration

an upper mantle seismic discontinuity beneath the galapagos archipelago and its implications for studies of the lithosphere asthenosphere boundary an upper mantle seismic discontinuity the gutenberg or g discontinuity at which shear wave velocity decreases with depth has been mapped from s to p conversions in radial receiver functions recorded across the galapagos archipelago the mean depth of the discontinuity is 91 8 km beneath the southeastern archipelago and 72 5 km beneath surrounding regions the discontinuity appears deeper beneath the portion of the nazca plate that we infer passed over the galapagos mantle plume than elsewhere in the region we equate the depth of the g discontinuity to the maximum depth extent of anhydrous melting which forms an overlying layer of dehydrated and depleted mantle we attribute areas of shallow discontinuity depth to the formation of the dehydrated layer near the galapagos spreading center and areas of greater discontinuity depth to its modification over a mantle plume with an excess temperature of 115 30 c the g discontinuity lies within a high seismic velocity anomaly that we conclude forms by partial dehydration and a gradual but steady increase in seismic velocity with decreasing depth after upwelling mantle first encounters the solidus for volatile bearing mantle material at the depth of the solidus for anhydrous mantle material removal of remaining water creates a sharp decrease in velocity with depth this discontinuity may also mark a site of melt accumulation results from seismic imaging the compositions of galapagos lavas and rare earth element concentrations across the archipelago require that mantle upwelling and partial melting occur over a broad region within the dehydrated and depleted layer we conclude that the g discontinuity beneath the archipelago does not mark the boundary between rigid lithosphere and convecting asthenosphere

a preliminary view of the coexistence of mammoth and early peoples in mexico abstract a progress report about human mammoth interactions in mexico is provided based primarily on a literature search more than 270 mammoth localities are known in mexico but only 17 of them have shown some evidence of an association between early peoples and mammoth however that number is even less when each locality is assessed in detail due to the lack of a supportable association or the loss of the actual specimens that precludes their analysis using current techniques only six localities have modified mammoth bone among them the greatest potential for demonstrating such a relationship is at santa isabel iztapa valsequillo villa de guadalupe and tocuila establishing an analysis methodology for the materials from those as well as new localities is warranted to provide the basis for interpreting the human mammoth relationship in mexico future research calls for detailed stratigraphic and radiometric control and an analytical protocol for bone analysis focused on taphonomy and biotechnology

waveform tomography reveals channeled flow at the base of the oceanic asthenosphere understanding the relationship between different scales of convection that drive plate motions and hotspot volcanism still eludes geophysicists using full waveform seismic tomography we imaged a pattern of horizontally elongated bands of low shear velocity most prominent between 200 and 350 kilometers depth which extends below the well developed low velocity zone these quasi periodic fingerlike structures of wavelength 2000 kilometers align parallel to the direction of absolute plate motion for thousands of kilometers below 400 kilometers depth velocity structure is organized into fewer undulating but vertically coherent low velocity plumelike features which appear rooted in the lower mantle this suggests the presence of a dynamic interplay between plate driven flow in the low velocity zone and active influx of low rigidity material from deep mantle sources deflected horizontally beneath the moving top boundary layer

seismic structure of the upper mantle in a central pacific corridor the seismic structure of the tonga hawaii corridor has been investigated by combining two data sets revenaugh and jordan s reflectivity profile from scs reverberations which provides travel times to and impedance contrasts across the major mantle discontinuities and 1500 new observations of frequency dependent phase delays for the three component s ss and sss body waves and the r1 and g1 surface waves which constrain the velocity structure within this layered framework the shear waves turning in the upper mantle showed significant splitting of the sh and sv components indicative of shallow polarization anisotropy the data set was inverted in conjunction with attenuation and mineralogical constraints to obtain a complete spherically symmetric radially anisotropic structure the final model pa5 is characterized by a high velocity anisotropic lid bounded at 68 km depth by a large negative g discontinuity a low velocity anisotropic layer below g extending to a small l discontinuity at 166 km an isotropic steep gradient region between 166 km and 415 km and transition zone discontinuities at 415 507 and 651 km the depth of the radial anisotropy in pa5 is shallower than in most previous studies based on surface waves and higher modes the average value of radial shear anisotropy in the lid 3 7 is consistent with the magnitude expected from the spreading controlled models of olivine orientation while anisotropy in the low velocity zone which is required by our data set could be induced either by paleostrains that took place near the ridge crest or by shearing in the asthenosphere as a result of present day plate motions on the basis of recent work by hirth and kohlstedt we suggest that the g discontinuity is caused by a rapid increase in the water content of mantle minerals with depth marking the fossilized lower boundary of the melt separation zone active during crust formation the high gradient zone between 200 and 400 km is a characteristic feature of convecting oceanic upper mantle and is probably controlled by a steady decrease in the homologous temperature over this depth interval the average shear velocity gradient in the transition zone is lower than in most previous seismic models in better agreement with the predictions for a pyrolitic composition

the taphonomy of mammoth localities in southeastern wisconsin usa abstract four southeastern wisconsin mammoth localities located within a glacial landscape had well preserved remains found in inter morainal depressions filled with lacustrine clays covered with peat numerous radiocarbon ages dated the mammoths to the late pleistocene the taphonomic analysis focused on determining the agency or agencies involved in site formation and the agency or agencies involved in modification to the bones statistical approaches to bone orientation data underscored that water transport was not a factor in the formation of the bone beds nor was water movement a disturbance factor the bone modification profile of the overall assemblage was dominated by chemical weathering followed by other chemical and microbiological processes root etching was the most common biological modification and the most frequent modifications are involved with the microenvironments of the surface to burial substrate potentially cultural modification accounted for only a small portion of the cortical damage to the bones this general profile indicated an assemblage far more influenced by the immediate environment than by passing animals or people

a seismic reflection image for the base of a tectonic plate a high resolution image for the base of an oceanic plate that is subducting beneath north island new zealand reveals a channel which is interpreted as a sheared zone of ponded partial melts or volatiles this low viscosity channel decouples the plate from mantle flow beneath allowing plate tectonics to work tim stern and co authors use explosion generated seismic waves to form a high resolution image of the base of an oceanic plate that is subducting beneath north island new zealand they find an abrupt seismic wave speed transition less than a kilometre thick at a depth of 100 km dipping at an angle of 15 the presence of a parallel 10 km deeper reflection event shows that the decrease in compressional wave speed is confined to a channel at the base of the plate which the authors interpret as a sheared zone of ponded partial melts or volatiles they conclude that this is independent evidence for a low viscosity channel at the lithosphere asthenosphere boundary that decouples plates from mantle flow beneath and allows plate tectonics to take place plate tectonics successfully describes the surface of earth as a mosaic of moving lithospheric plates but it is not clear what happens at the base of the plates the lithosphere asthenosphere boundary lab the lab has been well imaged with converted teleseismic waves1 2 whose 10 40 kilometre wavelength controls the structural resolution here we use explosion generated seismic waves of about 0 5 kilometre wavelength to form a high resolution image for the base of an oceanic plate that is subducting beneath north island new zealand our 80 kilometre wide image is based on p wave reflections and shows an approximately 15 dipping abrupt seismic wave speed transition less than 1 kilometre thick at a depth of about 100 kilometres the boundary is parallel to the top of the plate and seismic attributes indicate a p wave speed decrease of at least 8 3 per cent across it a parallel reflection event approximately 10 kilometres deeper shows that the decrease in p wave speed is confined to a channel at the base of the plate which we interpret as a sheared zone of ponded partial melts or volatiles this is independent high resolution evidence for a low viscosity channel at the lab that decouples plates from mantle flow beneath and allows plate tectonics to work

thermal structure radial anisotropy and dynamics of oceanic boundary layers defining the oceanic lithosphere as a thermal boundary layer allows to explain to first order age dependent bathymetry and isotropic wave speeds in contrast ss precursors and receiver functions suggest a subhorizontal interface within this layer on top of a radially anisotropic zone comparing a suite of geodynamic scenarios against surface wave dispersion data and seismic discontinuities we find that only weak age dependency of the radially anisotropic zone is compatible with observations we show that this zone is confined from below by a second weaker seismic interface while observed azimuthal anisotropy is consistent with lattice preferred orientation of olivine due to asthenospheric flow underneath the lithosphere radial anisotropy requires additional contributions perhaps from petrological fabrics or melt ponding this implies that seismic reflectors previously associated with the base of the lithosphere are instead associated with preserved structures embedded in it they carry information about plate formation but have little control on plate deformation

receiver function imaging of lithospheric structure and the onset of melting beneath the galapagos archipelago abstract the galapagos archipelago represents an opportunity to investigate the properties of young oceanic lithosphere the effects of a hotspot anomaly on lithospheric thickness and melting dynamics in a hotspot ridge interaction here we use data recorded by the signet array and permanent station payg on the islands santa cruz and isabela respectively we used p to s ps and s to p sp receiver functions to constrain crust and mantle structure a simultaneous deconvolution method was used to constrain 1 d structure and also for the modeling of robust features a migrated extended multitaper method was used to investigate 3 d structural variations ps images a velocity increase with depth at 11 7 km probably the base of the pre plume crust or old moho sp imaging and modeling images a second deeper velocity increase at 37 7 km depth a velocity decrease with depth is imaged on average at 75 12 km likely associated with the lithosphere asthenosphere boundary this discontinuity is imaged deeper 82 km in the southwest and shallower 66 km in the northeast near the spreading ridge although the trend is consistent with lithospheric thickening with age the thickness is much larger than predicted by conductive cooling models of 0 10 my oceanic lithosphere we infer a compositional contribution to velocity variations finally a velocity increase with depth is imaged at 125 to 145 15 km depth that is likely associated with the onset of melting the discontinuity is imaged deeper in 3 sectors of the galapagos platform ridge region all coincident with the slowest surface wave shear velocity anomalies in the upper 100 km one is located in the southwest in a hypothesized plume location the other two are to the northwest and northeast possibly illuminating multiple plume diversions related to complex plume ridge interactions

imaging the seismic lithosphere asthenosphere boundary of the oceanic plate 1 the seismic lithosphere asthenosphere boundary lab or g discontinuity a seismologically characterized abrupt drop in wave speed in the uppermost mantle is one of the key issues in current geodynamics although plate tectonics started as a theory for the ocean reports on lab for normal oceanic regions are scarce due to paucity of seismic data and whether or not the oceanic lab grows with age is the key issue to be resolved we conduct a systematic survey for the oceanic lab using s to p converted seismic waves along three margins of oceanic plates whose crustal age ranges from 10 myr to 130 myr and we observe laterally continuous oceanic lab images the thickness of the oceanic plate estimated from labs increases with the plate age though scattered suggesting that the evolution of oceanic lithosphere is predominantly governed by temperature and that the oceanic seismic lab represents a boundary that grows with age

the faunal remains from evron quarry in relation to other lower paleolithic hominid sites in the southern levant abstract the mammalian assemblage and archaeological finds from the lower palaeolithic hominid site of evron quarry situated on the northern coastal plain of israel are described and discussed in their lithic and faunal composition the sites of latamne qfiii latamne formation orontes syria and sitt markho nahr elkebir syria resemble evron and are probably contemporaneous it is suggested here based on their lithic and faunal composition that these sites may be chronologically closer to the site of ubeidiya ubeidiya formation jordan valley israel 1 4 myr than to the sites of gesher benot ya akov dated as

elephants and subsistence evidence of the human exploitation of extremely large mammal bones from the middle palaeolithic site of preresa madrid spain the archaeological site at preresa madrid spain has been dated to 84 5 6 ka by optically stimulated luminescence osl mis 5a an area 255 m2 was excavated and 754 lithic pieces were recovered as well as a large amount of micro and macro vertebrate remains including proboscidean bones the aim of this paper is to outline the results of the taphonomic study of these remains the identification of cut marks on a number of the bones recovered strengthens the theory that the exploitation of extremely large mammals was more than just a marginal practice before the upper palaeolithic additionally the identification of green bone fractures and percussion marks confirm for the first time that the bone marrow of these taxa was also consumed few other cases of this practice have been identified firstly because obtaining this substance would not be an easy matter and secondly because similar nutritional needs can also be met by the consumption of brain matter which is easier to acquire

a unified continental thickness from seismology and diamonds suggests a melt defined plate thick rigid continents move over the weaker underlying mantle although geophysical and geochemical constraints on the exact thickness and defining mechanism of the continental plates are widely discrepant xenoliths suggest a chemical continental lithosphere 175 kilometers thick whereas seismic tomography supports a much thicker root 250 kilometers and a gradual lithosphere asthenosphere transition consistent with a thermal definition we modeled ss precursor waveforms from continental interiors and found a 7 to 9 velocity drop at depths of 130 to 190 kilometers the discontinuity depth is well correlated with the origin depths of diamond bearing xenoliths and corresponds to the transition from coarse to deformed xenoliths at this depth the xenolith derived geotherm also intersects the carbonate silicate solidus suggesting that partial melt defines the plate boundaries beneath the continental interior

predictions and observations for the oceanic lithosphere from s to p receiver functions and ss precursors the ocean lithosphere is classically described by the thermal half space cooling hsc or the plate models both characterized by a gradual transition to the asthenosphere beneath scattered waves find sharp seismic discontinuities beneath the oceans possibly from the base of the plate active source studies suggest sharp discontinuities from a melt channel we calculate synthetic s to p receiver functions and ss precursors for the hsc and plate models and also for channels we find that the hsc and plate model velocity gradients are too gradual to create interpretable scattered waves from the base of the plate subtle phases are predicted to follow a similar trend as observations flattening at older ages therefore the seismic discontinuities are probably caused by a thermally controlled process that can also explain their amplitude such as melting melt may coalesce in channels although channels 10 km thick should be resolvable by scattered wave imaging

along the ice margin the cultural taphonomy of late pleistocene mammoth in southeastern wisconsin usa abstract four localities fenske mud lake schaefer and hebior in southeastern wisconsin have been put forth as probable sites associated with early peoples based on purported cultural marks on bones and lithic artifacts only two of the localities schaefer and hebior have associated lithics radiocarbon dates provide a time period of ca 13 530 11 200 yr bp results of the taphonomic analysis regarding natural modifications are reported elsewhere and the potential cultural modification category was examined further using established criteria as well as additional features two mark types are identified as caused by human agency foot elements are most affected by marks followed by long bones the marks indicate two major activities occurring that of cutting actions in defleshing and prying or leverage actions in disarticulation the mud lake and fenske mammoth are found carcasses already stiffened when scavenged by people schaefer most likely represents a hunted animal while hebior being a hunted or found fresh carcasses could not be determined the resource procurement strategy whether the carcass is fresh or stiffened appears to be the same easily accessible legs and feet form the focal point and provide a sizeable amount of protein from muscle bundles and fat from foot pads based on the wisconsin localities both hunting and scavenging of mammoth by early peoples have a time depth in the late pleistocene beyond the clovis age

surface and near surface effects on seismic waves theory and borehole seismometer results a simple plane wave model is adequate to explain many surface versus borehole seismometer data sets using such a model we present a series of examples which demonstrate the effects of the free surface near surface velocity gradients and low impedance surface layers on the amplitudes of upcoming body waves in some cases these amplitudes are predictable from simple free surface and impedance contrast expressions however in other cases these expressions are an unreliable guide to the complete response and the full plane wave calculation must be performed large surface amplifications are possible even without focusing due to lateral heterogeneities or nonlinear effects both surface and borehole seismometer site responses are almost always frequency dependent ocean bottom versus borehole seismic data from the 1983 ngendei seismic experiment in the southwest pacific are consistent with both a simple plane wave model and a more complete synthetic seismogram calculation the borehole seismic response to upcoming p waves is reduced at high frequencies because of interference between the upgoing p wave and downgoing p and sv waves reflected from the sediment basement interface however because of much lower borehole noise levels the borehole seismometer enjoys a p wave signal to noise advantage of 3 to 7 db over nearby ocean bottom instruments

characterization of bone surface modifications on an early to middle pleistocene bird assemblage from mata menge flores indonesia using multifocus and confocal microscopy abstract island southeast asia isea is a key region for the study of human evolution new fossil and archaeological evidence from several islands suggests an early to middle pleistocene colonisation date by hominins a taphonomic framework however such as that exists for africa is currently lacking and taphonomical studies of isea vertebrate assemblages are very limited in this paper we apply multifocus and confocal microscopy to surface modifications on an early to middle pleistocene avian assemblage from mata menge in the so a basin of central flores indonesia with the aim of characterizing material and testing the relevance of 3d reconstructions to study the taphonomy of isea bone assemblages our observations document a number of bone surface modifications including individual parallel grooves overlapping spindle like striations elongated impacts short composite grooves and rows of pits these features suggest that several taphonomic agents were at play during and after the accumulation of the mata menge small vertebrate assemblage we find no unambiguous evidence for the exploitation of birds by the so a basin hominins or for hominins being a significant accumulating agent of avian remains at mata menge however our work should be seen as preliminary as direct comparative data on relevant biological agents are lacking the markedly distinct faunal composition and climatic regimes of many southeast asian islands and the potential use of different tools by hominins warrants the development of a comprehensive taphonomical framework that is specifically relevant for isea

seismic imaging of thickened lithosphere resulting from plume pulsing beneath iceland ocean plates conductively cool and subside with seafloor age plate thickening with age is also predicted and hot spots may cause thinning however both are debated and depend on the way the plate is defined determining the thickness of the plates along with the process that governs it has proven challenging we use s to p sp receiver functions to image a strong persistent lab beneath iceland where the mid atlantic ridge interacts with a plume with hypothesized pulsating thermal anomaly the plate is thickest up to 84 6 km beneath lithosphere formed during times of hypothesized hotter plume temperatures and as thin as 61 6 km beneath regions formed during colder intervals we performed geodynamic modeling to show that these plate thicknesses are inconsistent with a thermal lithosphere instead periods of increased plume temperatures likely increased the melting depth causing deeper depletion and dehydration and creating a thicker plate this suggests plate thickness is dictated by the conditions of plate formation

spreading rate dependence of three dimensional structure in oceanic spreading centres segmentation by transform faults and other types of along axis discontinuity1 is a well described but poorly explained characteristic of oceanic spreading centres here we use numerical experiments to explore the dynamics of mantle flow and melting beneath a mid ocean ridge buoyant upwelling driven by compositional density variations resulting from the extraction of the melt that forms the ocean crust exhibits a spreading rate dependent transition between two dimensional and three dimensional upwelling structures for low spreading rates and mantle viscosities an initial two dimensional structure transforms into a three dimensional one at high spreading rates an initially two dimensional structure remains two dimensional these results suggest that the origin of spreading centre segmentation may be different at fast and slow spreading rates

clustered impacts experiments and implications impact by clusters of projectiles rather than a single projectile can result from several processes atmospheric breakup tidal breakup and ejecta from a large primary impact experiments have been performed in order to establish the characteristics of such events over a wide range of impact velocities 15 m s to 6 km s at very low impact velocities 15 200 m s clustered impacts were produced by launching a grouped projectiles of aluminum shot steel shot iron filings and sand at moderate to high velocities 0 8 6 km s pyrex spheres were shattered above the target during passage through aluminum foil or paper thereby forming a well defined cluster of fragments of overall radius rc the ratio of the overall radius rc of the cluster to the radius rs of a solid impactor of the same mass provides a measure of the cluster dispersion sand and compacted pumice targets were used in order to compare qualitatively the additional effect of slight differences in target strength the experiments reveal marked contrasts between impacts by clusters of projectiles and impacts by a single solid body tight clusters rc rs 20 displace a factor of 10 less mass this reduction in cratering efficiency is largely expressed as a shallow crater with an aspect ratio diameter depth as large as 30 for open clusters the size and velocity of the cluster as well as the density and strength contrast between the impactor and target can dramatically affect crater morphology open clusters impacting compacted pumice produce a flat hummocky floor with an incipient multiring pattern whereas a tight cluster impacting the same target produces a central floor mound oblique impacts by symmetrical clusters form a characteristic array of v shaped ridges pointing uprange the apex angle of the ridges depends on the cluster dispersion and impact angle inventories of postimpact projectile material reveal that the projectile is largely retained on the surface and spread downrange from the impact direction the amount of projectile material retained on the surfaces increases with decreasing impact angle from the horizontal and with increasing strength of the target relative to the projectile clustered impact craters and lunar secondary craters bear striking similarities over a broad range of morphologic features on this basis and on the basis of reasonable models of ejecta curtain structure we suggest that these experiments provide new clues for understanding ejecta emplacement around large lunar impact craters when the ejecta curtain around large impacts is viewed as a thick wall of debris and clustered impactors are viewed as a unit section of such a curtain then experimental results indicate that the continuous ejecta facies even for lunar craters larger than 100 km could contain as much as 90 primary material such a conclusion contrasts with many existing models that derive mixing ratios implicitly based on single noninteracting impact events beyond the continuous ejecta facies impacting clusters of ejecta provide a physical basis for understanding the wide variety of secondary morphologies and the large range in spectral signatures of primary material in crater rays

seismic evidence for sharp lithosphere asthenosphere boundaries of oceanic plates the mobility of the lithosphere over a weaker asthenosphere constitutes the essential element of plate tectonics and thus the understanding of the processes at the lithosphere asthenosphere boundary lab is fundamental to understand how our planet works it is especially so for oceanic plates because their relatively simple creation and evolution should enable easy elucidation of the lab data from borehole broadband ocean bottom seismometers show that the lab beneath the pacific and philippine sea plates is sharp and age dependent the observed large shear wave velocity reduction at the lab requires a partially molten asthenosphere consisting of horizontal melt rich layers embedded in meltless mantle which accounts for the large viscosity contrast at the lab that facilitates horizontal plate motions

the davy crater chain implications for tidal disruption in the earth moon system and elsewhere linear crater chains on ganymede and callisto apparently provide an impact record of tidally disrupted bodies like comet shoemaker levy 9 at jupiter we propose that the davy crater chain on the earth s moon records a similar tidal disruption event in the earth moon system most lunar crater chains result from either volcanism or secondary impacts but the davy chain differs in setting and appearance from these crater chains and instead shows morphologic similarities to the jovian crater chains while the davy chain is much smaller than the jovian crater chains tidal disruption models indicate that this smaller size is consistent with the earth s lower mass the disruption models also indicate that most earth crossing comets and asteroids are moving too fast for fragment dispersion before impact to produce the observed crater chain length thus the davy and jovian crater chains apparently result from bodies with different orbital characteristics in addition the limited dispersion of high velocity fragments at the moon suggests that crater chains may not form for all disruption events or on all planetary satellites based on modeled fragment dispersions elsewhere in the solar system we suggest that similar crater chains may be present on iapetus and possibly on titan titania or oberon

imaging pacific lithosphere seismic discontinuities insights from ss precursor modeling oceanic lithosphere provides an ideal location to decipher the nature of the lithosphere asthenosphere system which is vital to our understanding of plate tectonics it is well established that oceanic lithosphere cools thickens and subsides as it ages according to the conductive cooling models yet this simple realization fails to explain various observations for example old oceanic lithosphere does not subside as predicted further precise imaging of the lower boundary of the oceanic lithosphere has proven challenging here we use ss precursors to image the discontinuity structure across the pacific ocean using 24 years of teleseismic data we image a sharp pervasive velocity discontinuity 3 15 drop over 36 my there is no age depth dependence and we image the discontinuity at an average depth of 60 1 5 km the amplitude and sharpness of the boundary suggests a compositional variation and or layered carbonatitic melt may be required to explain our observations rather than temperature alone the strength and pervasiveness of the boundary suggests that it is likely related to the lithosphere asthenosphere boundary an additional deeper discontinuity at 80 120 km depth is imaged intermittently that in most cases likely represents a continuing negative velocity gradient in depth

characterization of recent marks produced on fossil bone surface during sullegic and trephic processes and their influence on taphonomic studies abstract different taphonomic processes throughout the history of a fossil assemblage may preserve modify or destroy particular palaeobiological traits but these processes always increase taphonomic information of the past similarly fossils are affected during later stages of taphonomic history i e excavation preparation study and storage of fossils known as sullegic and trephic phases tools used during excavation and preparation of fossils can damage them and produce marks on their surface some of these recent marks highly mimic taphonomic marks produced before excavation both modern and fossil marks lead to misinterpretations and erroneous conclusions when similarities are not clearly detected in order to distinguish recent from ancient marks several diagnostic criteria resulting from experimental work are described in this paper

a sharp lithosphere asthenosphere boundary imaged beneath eastern north america although a rigid lithosphere about 100 km of crust and uppermost mantle moving over a weaker asthenosphere a few hundred kilometres of more deformable rock is a widely accepted aspect of plate tectonics the properties of the boundary between them are poorly understood when compressional waves p waves from an earthquake encounter an interface at an angle some of the energy is converted to shear waves or s waves these converted waves can be used to construct an image of the interface based on converted waves recorded in eastern north america the lithosphere asthenosphere boundary has been resolved as a sharp gradient that cannot be explained by thermal gradients alone indicating that the boundary is controlled by melt or high water content in the asthenosphere plate tectonic theory hinges on the concept of a relatively rigid lithosphere moving over a weaker asthenosphere yet the nature of the lithosphere asthenosphere boundary remains poorly understood the gradient in seismic velocity that occurs at this boundary is central to constraining the physical and chemical properties that create differences in mechanical strength between the two layers for example if the lithosphere is simply a thermal boundary layer that is more rigid owing to colder temperatures mantle flow models1 2 indicate that the velocity gradient at its base would occur over tens of kilometres in contrast if the asthenosphere is weak owing to volatile enrichment3 4 5 6 or the presence of partial melt7 the lithosphere asthenosphere boundary could occur over a much smaller depth range here we use converted seismic phases in eastern north america to image a very sharp seismic velocity gradient at the base of the lithosphere a 3 11 per cent drop in shear wave velocity over a depth range of 11 km or less at 90 110 km depth such a strong sharp boundary cannot be reconciled with a purely thermal gradient but could be explained by an asthenosphere that contains a few per cent partial melt7 or that is enriched in volatiles relative to the lithosphere3 4 5 6

scattered wave imaging of the lithosphere asthenosphere boundary several recent studies have imaged discontinuities interpreted as the lithosphere asthenosphere boundary using receiver function methods these are exciting results since this boundary is fundamental and yet relatively elusive its location is not well imaged nor are its properties well understood the receiver function method provides high depth resolution and the multitude of studies using this method have increased lateral resolution a better global understanding of the location and nature of the boundary is developing which ultimately will have implications for mantle dynamics and planetary evolution however these new results do not all form a clear and consistent picture and in some cases introduce new complexities and questions some apparent contradictions may represent unmodeled earth structure overall interpretation and synthesis requires careful consideration of the approaches and sensitivities of individual studies

size matters an evaluation of descriptive and metric criteria for identifying cut marks made by unmodified rocks during butchery one of the key concerns in human evolution studies is tracing the development of stone tool use by early hominins to acquire meat it has been suggested that the earliest tools used for this purpose might have been unmodified naturally sharp rocks however it has proven challenging to distinguish marks on bones made by hominins using humanly unmodified rocks hurs for butchery from marks made by natural processes here we present the results of a study aimed at comparing marks made by hurs during butchery versus marks made by the same hurs through simulated natural processes specifically the fluvial tumbling of bones with naturally sharp rocks replicated here using a rock tumbler the results of this study in which the lithological effector is held constant while the actor is varied confirm earlier studies suggesting that many existing categorical attributes do not effectively distinguish between marks made by hurs versus those made by other tools or trampling however we also present a novel way of measuring mark depths which shows that marks made by the human actor are much deeper and longer than those made by natural processes the size of marks therefore matters this knowledge may help us assess the likelihood that marks on bone surfaces may have been produced by natural forces as opposed to by humans using unmodified rocks for butchery

middle stone age bone tools from the howiesons poort layers sibudu cave south africa abstract recently discovered bone implements from middle stone age msa deposits at sibudu cave south africa confirm the existence of a bone tool industry for the howiesons poort hp technocomplex previously an isolated bone point from klasies river provided inconclusive evidence this paper describes three bone tools two points and the end of a polished spatula shaped piece from unequivocal hp layers at sibudu cave with ages greater than 61 ka comparative microscopic and morphometric analysis of the sibudu specimens together with bone tools from southern african middle and later stone age lsa deposits an iron age occupation nineteenth century bushman hunter gatherer toolkits and bone tools used experimentally in a variety of tasks reveals that the sibudu polished piece has use wear reminiscent of that on bones experimentally used to work animal hides a slender point is consistent with a pin or needle like implement while a larger point reminiscent of the single specimen from peers cave parallels large un poisoned bone arrow points from lsa iron age and historical bushman sites additional support for the sibudu point having served as an arrow tip comes from backed lithics in the hp compatible with this use and the recovery of older larger bone and lithic points from blombos cave interpreted as spear heads if the bone point from the hp layers at sibudu cave is substantiated by future discoveries this will push back the origin of bow and bone arrow technology by at least 20 000 years and corroborate arguments in favour of the hypothesis that crucial technological innovations took place during the msa in africa

criteria for identifying bone modification by termites in the fossil record three geographically dispersed middle and later stone age cave sites in south africa and a middle stone age cave site in ethiopia share a similar taphonomic signature that includes destruction of bones associated with variable forms of star shaped features clusters of microscopically visible sub parallel striations edge gnawing pits and etching of the bone surface similar traces preserved on plio pleistocene fauna are interpreted by different authors as the possible work of termites or ants considering that ambiguity exists in the interpretation of these traces and that there are no modern examples available for comparison we set out to create a reference collection of bones modified by southern african termites here we present the results of an actualistic experiment conducted with the harvester termite trinervitermes trinervoides sjostedt isoptera termitidae in the sterkfontein valley south africa results show that within six months all bones were approximately half covered with a dark surface residue had an etched surface appearance and recorded boreholes and destruction particularly of less dense elements and epiphyses star shaped marks edge gnawing and clusters of sub parallel striations on the periosteal surface were faint after six months but became clearly visible and more plentiful after 12 months a finding attributed to the termites being more active in austral autumn and spring this result demonstrates the pertinence of insect modification studies to our understanding of regional palaeoenvironment palaeoecology and palaeoclimate this experiment has demonstrated that t trinervoides can destroy bone in all stages of preservation favouring fresh thin cortical and spongy bone with meat and marrow the presence of appreciable quantities of calcium carbonate in termite mounds suggests that termites may be drawn to dolomitic cave sites and the calcium rich bones they contain to satisfy their mineral requirements they therefore have the potential to bias taxonomic and element representation minimum number of individuals and age profiles in a faunal assemblage and may account in part for the patchy preservation of faunal remains including hominins in fossil deposits and or the lack of bone artefacts at some middle stone age cave sites preserving long sequences of occupation

tumbling effects on bone surface modifications bsm an experimental application on archaeological deposits from the barranc de la boella site tarragona spain abstract tumbling is defined as a process in which hyper concentrated flows alter bone remains producing changes in their morphology and original structure although the process is well known little experimental research has focused on describing the effects this process has on bone surface modifications bsm which can subsequently be applied to the fossil record water currents may have played an important role in altering the surfaces of bones from barranc de la boella which were deposited in a deltaic fan context striae of undetermined origin have been documented on bones at the la mina locality and possible cut marks found on bones at pit 1 locality in our experiments both fresh and dry bones with reproduced trampling striae and cut marks were tumbled in a tumbling machine combining different types of movement and proportions of water to sediment the bones were examined after each of the five cycles of the modification process which lasted 30 30 1 h 2 h and 4 h our results show a considerable diminishing of trampling striae while the majority of cut marks were preserved the marks on fresh bones were more severely altered than those on dry bones based on the results of this experiment the marks from pit 1 appear to be morphologically close to the experimentally altered cut marks while the majority of those from la mina are more similar to the altered trampling striae

taphonomical and palaeoecological investigation of the late cretaceous maastrichtian tustea vertebrate assemblage romania haţeg basin insights into a unique dinosaur nesting locality abstract the tustea vertebrate locality at oltoane hill northwestern part of the ha eg basin romania has provided a rich and diverse assemblage of late cretaceous maastrichtian continental vertebrates more than 800 vertebrate fossils were recovered from this locality the isolated and associated remains represent 21 different taxa including amphibians turtles lizards snakes crocodyliforms pterosaurs dinosaurs and mammals the local assemblage is overwhelmingly dominated by dinosaurs with the rhabdodontid zalmoxes as the most abundant taxon the bonebeds that yielded this fossil material occur in a stacked series of mudstone calcrete units belonging to the middle member of the densus ciula formation the taphonomical investigations suggest that the tustea assemblage is made up of attritionally accumulated politaxic remains and that it is a parautochthonous assemblage with no evidence for significant bone transport or reworking according to the synthesis of all available field data two outstanding fossiliferous levels can be identified within the tustea locality where megaloolithus eggs and hadrosauroid hatchling material are preserved together recognized here as two superposed nesting grounds such co occurrence was considered controversial since there is a long standing and quasi general consensus that eggs of the megaloolithus oogenus were laid by titanosaurian sauropods we present several alternative scenarios to account for the co occurrence of telmatosaurus hatchling remains and megaloolithid eggs in the nesting horizons and explore these alternative hypotheses by weighing the arguments supporting or contradicting them the burden of evidence derived from our sedimentological taphonomical and palaeoecological investigations at tustea is still in favour of the autochthony of the hatchlings preserved within their own nesting grounds whereas there is no such support for a titanosaurian origin of the tu tea megaloolithid eggs

thickening of young pacific lithosphere from high resolution rayleigh wave tomography a test of the conductive cooling model direct seismic measurements of the thickening of oceanic lithosphere away from the spreading axis are rare due to the remoteness of mid ocean ridges on the east pacific rise at 17 s there were two long term broadband ocean bottom seismometer deployments the melt and glimpse experiments these arrays spanned young pacific plate seafloor ranging in age from 0 to 8 ma combining these two data sets we describe the increase in rayleigh wave phase velocities for 16 100 s period as function of distance from the ridge with two parameterizations an arbitrary function of seafloor age and a simple polynomial function of age on the pacific and nazca plates although resolution analysis shows that 10 to 15 independent pieces of information about the age variation of phase velocity on the pacific plate can be resolved at periods of 50 s the three parameter polynomial model fits the data almost as well indicating a simple pattern of the evolution of structure with age to compare our observations to the predictions for the conductive cooling of the lithosphere we convert a thermal half space cooling model to shear velocity using anharmonic and anelastic contributions the patterns in the velocities are not consistent with simple conductive cooling the conductive cooling model under predicts the changes in phase velocity with age observed in the 20 to 78 s period range we observe significant changes in shear velocity in the asthenosphere at depths greater than conductive cooling should extend the asthenospheric low velocity zone is asymmetric dipping to the west with the lowest velocities beneath the pacific plate west of the spreading center the conductive cooling model also over predicts the shear velocities in the lithosphere by 0 2 km s these anomalies indicate that more complicated mantle flow and significant mantle heterogeneities such as melt are required

the global attenuation structure of the upper mantle 1 a large data set of fundamental mode rayleigh wave amplitudes is analyzed to derive a new global three dimensional model of shear wave attenuation in the upper mantle the amplitude observations span a range of periods between 50 and 250 s and are derived from earthquakes with mw 6 0 that occurred between 1993 and 2005 four separate factors may influence an amplitude anomaly intrinsic attenuation along the raypath elastic focusing effects along the raypath uncertainties in the strength of excitation and uncertainties in the response at the station in an earlier paper dalton and ekstrom 2006a dependence of the retrieved attenuation structure on these terms was shown to be significant and an approach was developed to invert the amplitudes simultaneously for each term the new three dimensional attenuation model qrfsi12 which is the subject of this paper is derived using this method the model contains large lateral variations in upper mantle attenuation 60 to 100 and exhibits strong agreement with surface tectonic features at depths shallower than 200 km at greater depth qrfsi12 is dominated by high attenuation in the southeastern pacific and eastern africa and low attenuation along many subduction zones in the western pacific resolution tests confirm that the change in pattern of attenuation above and below 200 km depth can be determined with confidence using the fundamental mode data set the new model is highly correlated with global models of shear wave velocity particularly in the uppermost mantle suggesting that the same factors may control both seismic attenuation and velocity in this depth range however forcing the lateral perturbations in attenuation to match those found in global velocity models decreases the data variance reduction which suggests that subtle differences between patterns of attenuation and velocity are robust

bioerosion on vertebrate remains from the upper cretaceous of the haţeg basin romania and its taphonomic implications abstract bioerosion on fossil bones offers significant insights into both trophic relationships of ancient ecosystems and vertebrate taphonomy here we report six distinct trace fossil categories identified on isolated turtle crocodyliform and dinosaur remains from the upper cretaceous sinpetru formation of the ha eg basin romania for which five different probable tracemakers are identified 1 termites 2 dermestid beetles 3 multituberculate mammals 4 ziphodont theropod dinosaurs or crocodyliforms and 5 plants this extraordinary diversity of bioerosional trace fossils on vertebrate remains reveals insect vertebrate as well as vertebrate vertebrate interactions previously undocumented in the continental uppermost cretaceous of romania the association between different traces especially since many of these are superimposed on top of each other allows the reconstruction of the detailed taphonomic history of the specimens indicating four different taphonomic pathways the vertebrate remains with trace fossils described here were most likely exposed to post mortem biotic interactions for a prolonged time period before they were transported and or trampled and finally buried in the palaeoenvironmental context of a heterogeneous braided river system with low lying wetlands and more elevated drylands the death of the vertebrates as well as the scavenging likely occurred on the drylands

in the elephant everything is good carcass use and re use at castel di guido italy abstract castel di guido is a typical middle pleistocene elephant site where intentionally fragmented bones of elephant and of other large mammals were found together with acheulean biface like industry including bifaces made of various stone types and of elephant bone associated with flint tools on pebbles and flakes following a first interpretation of the evidence the site represented a single and short phase of use and elephants horses aurochs and few other species were killed and butchered on site or partly brought to the site to be butchered after having been killed elsewhere the bones were intentionally fractured for marrow extraction and left to season before being used as raw material for artefact production further evidence deriving from more recent studies suggests that the site lasted for much longer time and is in fact an intricate palimpsest of several phases of human use and partial reworking castel di guido results largely from anthropic processes deriving from peculiar behavioural aspects of the early neandertal groups that frequented the site the carcasses of various taxa were exploited for food and the elephant ones also for raw material in bone tool production this choice was probably due to limited availability of good quality flint or other hard rocks in the area because of these characteristics castel di guido is an ideal ground for exploring the aspects of use re use and recycling of food and raw material resources and of tools several stone and some bone tools show clear evidence of recycling such as subsequent knapping or refashioning phases put into evidence by different wear of the surfaces these characteristics point to long continuity of use of the site for similar purposes which is in accordance with the very different preservation of the remains that were partly reworked by short range fluvial processes these aspects indicate that the bones of large taxa mostly elephant were part of a complex subsistence system characterised by hunting and scavenging on one side and an extremely fuzzy boundary among use re use and recycling on the other one this system was based on the recycling or transfunctionalisation of the carcasses which were exploited for food consumption meat and possibly marrow and later for raw material procurement over a long time of permanence and availability on the surface of the site

the interpretation of stratified sites a view from underground abstract this paper reports on an experiment designed to study the role of trampling in the vertical dispersal of artifacts in the soil and in the mixing of originally separate sets of materials the experiment is part of a study of the archaeological stratigraphy and patterns of site use at a large stratified cave in southern france the experiment was designed to replicate conditions prevailing at the cave the results strongly suggest caution in the interpretation of living floors and stratified assemblages in sandy deposits

investigating human and megafauna co occurrence in australian prehistory mode and causality in fossil accumulations at cuddie springs abstract human arrival in sahul pleistocene australia and new guinea has long been argued as the catalyst in the decline and disappearance of a suite of extinct animals referred to as megafauna the debate concerning causality in sahul is highly polarised with climate change often cited as the alternative explanatory model on continental australia there are few datasets available with which to explore the likely processes leading to the extinction events at the present time there is one site in new guinea nombe rockshelter and one on continental australia cuddie springs where the coexistence and temporal overlap of humans and megafauna has been identified the cuddie springs pleistocene archaeological site in southeastern australia contains an association of fossil extinct and extant fauna with an archaeological record through two sequential stratigraphic units dating from c 36 to c 30 ka ago a taphonomic study of the fossil fauna has revealed an accumulation of bone in a primary depositional context consistent with a waterhole death assemblage overall the faunal assemblage studied here n 8146 nisp 1355 has yielded little direct evidence of carnivore damage or human activities post depositional factors such as physical destruction incurred by trampling compaction of sediments and or the hydrological status of the lake at that time have played important roles as the only known site on continental australia where megafauna and humans co occur the cuddie springs faunal assemblage yields equivocal evidence for a significant human role in the accumulation of the fauna here at the present time there is no evidential basis to the argument that humans had a primary role in the extinction of the australian megafauna the first colonisers are likely to have preyed upon those few species known to have persisted to this time but their impact may have been restricted to the tail end of a process that had been underway for millennia prior to human arrival

taphonomic and paleoecologic investigations of the late cretaceous santonian iharkut vertebrate assemblage bakony mts northwestern hungary abstract the iharkut vertebrate locality an open pit mine in the bakony mountains western hungary has provided a rich and diverse assemblage of late cretaceous santonian continental vertebrates the isolated and associated remains represent 31 different taxa including fish amphibians turtles lizards pterosaurs crocodilians non avian dinosaurs and birds sedimentologic investigations suggest that the iharkut depositional environment was represented by the floodplain of a very low gradient river the 10 50 cm thick bonebed of site sz 6 is the most important fossiliferous layer in the open pit mine and analysis of this site indicates alternating energy conditions during the bone accumulation which resulted in fossils of different states of preservation being deposited together the vertebrate assemblage of site sz 6 includes three main different subsets with widely different taphonomic history the characteristics and the preservation mode high rate of abrasion and the spherical shape of the bone pebbles suggest that this type of the isolated bones was more exposed to abrasion and probably the remains were transported from farther away than the other isolated bones the second group includes 88 of the iharkut collection containing most of the identified isolated bones and teeth and represents polytypic attritional remains transported and deposited by high density flow during ephemeral flood events meanwhile the monospecific ankylosaur skeletal material from iharkut site sz 6 may represent a mass death assemblage because seven skeletons of hungarosaurus were discovered from an area of approximately 400 m 2 and in many cases close to each other in the same layer the iharkut vertebrate assemblage is dominated by bones of aquatic semi aquatic animals while the number of terrestrial animal remains is subordinate the taphonomic analysis of the ankylosaur material from iharkut locality further strengthens the previously suggested hypothesis that some of the ankylosaurs preferred wetland habitats e g areas along fluvial systems while the other two herbivorous dinosaur groups from iharkut ornithopods and ceratopsians were probably living in distal habitats

autochthonous anisotropy of archaeological materials by the action of water experimental and archaeological reassessment of the orientation patterns at the olduvai sites abstract anisotropic patterns documented indirectly through m leakey s drawings of olduvai archaeological sites have led to questions about the integrity of these sites most experiments on bone transport by water have been carried out using complete elements that do not replicate specimen bone breakage and size as documented in archaeological sites in the present work an experimental framework is provided using experimental proxies of archaeological assemblages results show that autochthonous assemblages affected by hydraulic processes can adopt anisotropy in their fabric archaeological comparisons between drawings and excavated sites at olduvai stress the bias in leakey s drawings of flk zinj and flk north in bed i a large scale open excavation recently carried out at tk bed ii exposes an area comparable in size to leakey s excavations comparing the orientation patterns of this site to those reported by leakey shows how biased the drawing of the site is and how easily this can lead to misinterpretations of isotropy anisotropy with fatal consequences for the understanding of site formation processes

surface modification on bone trampling versus butchery abstract previous researchers have reported difficulties in distinguishing between surface marks on bone formed by sedimentary abrasion and those inflicted while butchering trampling by large ungulates and humans has been credited with producing pseudocut marks natural alterations to the bone that mimic cultural ones the purposes of this research are 1 to re examine trampling as a taphonomic process and 2 to suggest criteria useful for distinguishing sedimentary abrasion including trampling from butchery macroscopic and microscopic comparison of experimentally trampled bones and those which have had soft tissue removed with a flint tool demonstrate significant differences between the surface modifications produced by the two processes

a newly discovered antler flint knapping hammer and the question of their rarity in the palaeolithic archaeological record reality or bias abstract the use of soft bone antler tooth and wood hammers and retouchers is a key innovation in early stone tool technology first appearing in the archaeological record with lower palaeolithic handaxe industries e g boxgrove uk 500 ka although organic knapping tools were undoubtedly a component of early human toolkits and are essential for example for the manufacture of finely flaked handaxes mousterian scrapers and upper palaeolithic blades tools such archaeological finds are exceptionally rare in this study we present qualitative and quantitative analyses focus variation optical microscope scanning electron microscope micro ct scanning and energy dispersive x ray spectroscopy of a newly discovered antler flint knapping from laugerie haute west france this specimen was originally identified as a waste product from splinter manufacture and the use damage appears to have been overlooked by earlier workers the new analysis shows that prior to being used as a flint knapping percussor the red deer antler had been modified to reduce the length of its beam and to remove the tines although minimally used characteristic use damage includes attrition pits and scores compression of the antler matrix and flint chips embedded within some of the percussion features on the base of the burr an ams radiocarbon date of 12 385 55 bp 12 647 335 bc calibrated confirms a magdelenian context for the hammer the fact that the laugerie haute knapping hammer went unrecognised in a well studied and accessible collection where it was stored for almost 200 years suggests that antler hammers may be more common than generally assumed only further re examination of prehistoric antlers in museum collections will confirm whether the apparent rarity of antler hammers during the lower and middle palaeolithic is real phenomenon or the result of analytical biases

assessing the macrofracture method for identifying stone age hunting weaponry abstract macrofracture analysis is an experimentally derived method used as an initial step in investigating the hunting function of stone artefacts diagnostic impact fractures which can only develop as a result of longitudinal impact underpin this method macrofracture analysis recently gained favour in middle stone age studies supporting hypotheses for effective hunting during the late pleistocene in southern africa however the factors affecting diagnostic impact fracture formation and the interpretation of these fracture frequencies are not yet fully understood this paper outlines a set of experiments designed to test macrofracture formation under human and cattle trampling and knapping conditions the results show that a macrofractures occur frequently when stone artefacts are trampled by cattle and humans and in knapping debris b diagnostic impact fractures occur on some of the trampled flakes and knapping debris 3 but significantly less often than in previous hunting experiments c when they do occur they are likely produced by longitudinal forces similar to those experienced during hunting d considering artefact morphology is important during macrofracture analysis and e macrofracture analysis is not a standalone method but is most useful as part of a multi analytical approach to functional analysis these experiments help to establish a significant baseline diagnostic impact fracture frequency for the interpretation of archaeological macrofracture frequencies

subsidence of normal oceanic lithosphere apparent thermal expansivity and seafloor flattening abstract seafloor topography has been a key observational constraint on the thermal evolution of oceanic lithosphere which is the top boundary layer of convection in earth s mantle at least for the first 70 myr the age progression of seafloor depth is known to follow the prediction of half space cooling and the subsidence rate is commonly believed to be 350 m ma 1 2 here we show that based on a new statistical analysis of global bathymetry the average subsidence rate of normal oceanic lithosphere is likely to be 320 m ma 1 2 i e 10 lower than the conventional value we define the normal seafloor as regions uncorrelated with anomalous crust such as hotspots and oceanic plateaus but the lower subsidence rate appears to be a stable estimate not depending on how exactly we define the normal seafloor this low subsidence rate can still be explained by half space cooling with realistic mantle properties if the effective thermal expansivity of a viscoelastic mantle is taken into account in light of a revised model of half space cooling the normal seafloor unperturbed by the emplacement of anomalous crust exists for all ages and the so called seafloor flattening seems to be mostly caused by hotspots and oceanic plateaus

the application of geometric morphometric shape analysis to middle paleolithic bone retouchers from the altai mountains russia abstract here we apply geometric morphometric shape analysis to middle paleolithic bone retouchers from chagyrskaya cave in the altai mountains of southern siberia the cave contains evidence of the easternmost manifestation of the micoquian industry associated with neanderthals at end of mis4 and the beginning of mis3 taphonomic and scar pattern analyses were performed first on random samples exhibiting appropriate characteristics several retouchers produced on intentionally modified blanks were identified in our sample suggesting that some of the chagyrskaya cave bone retouchers can be described as formal tools all retouchers from chagyrskaya cave exhibit a similar general morphology the most variable group is comprised of complete retouchers without blank modifications retouchers exhibiting minor damage affect the general pattern of variability and it is not possible to identify them only by means of geometric morphometric shape analysis complete retouchers with blank modifications fall within the range of variability of complete retouchers without blank modification suggesting intentional shaping of blanks to conform to a standard template the range of variability of the bone retouchers does not differ significantly from that of the most highly modified lithic artifacts at chagyrskaya plano convex bifaces which may indicate intentional shape control for such artifacts geometric morphometric analysis indicates that the anatomical origin of bone blanks does not significantly influence the retouchers shape which may point to strict blank selection and at the same time intentional modification our results raise questions regarding the integration of retouchers into a complex multidimensional chaine operatoire as well as the nature of neanderthal cognitive abilities geometric morphometric shape analysis represents a major step forward in the study of prehistoric retouchers

steppe mammoth mammuthus trogontherii remains in their geological and cultural context from belchatow poland a consideration of human exploitation in the middle pleistocene abstract in 1981 and 1991 mammoth remains and associated fauna were found in central poland at the belchatow opencast mine in sandy gravel deposits most of them lay at approximately 160 175 m above mean sea level a s l located in the lower and upper members of the alluvial chojny formation this formation belongs to the middle pleistocene and can be connected with the mazovian mis 11 holsteinian or zbojnian mis 9 reinsdorf interglacial the belchatow mammoth assemblage described here consists of cranial and postcranial elements analysis of their morphological characteristics and osteometrics are used to demonstrate that at least two molars and one tusk belong to mammuthus trogontherii and that the tusk belonged to a male on the basis of the minimum number of elements of the most common element left incisors the mammoth remains represent at least two individuals based upon the different ages of death for the various elements it appears that they represent several individuals the bulk of the mammoth remains were recovered from the oldest depositional cycle in the lower member of chojny formation and are therefore coincident with a shrub tundra environment and cool temperate conditions they were deposited in sediments formed by a meandering river with a fairly low power of flow and were buried soon after transport over a short distance this conclusion is also supported by the palaeobotanical data an additional element a costa was recovered from the upper member of the chojny formation which is associated with the cooling conditions the enveloping deposit appears to be the result of a series of more rapid discharge events by a braided river this element is distinguished from those elements recovered from the lower member due to the presence of a series of unusual striations sem analysis suggests that some of the striations were probably made by chipped stone tools used in a slicing action as if the result of the filleting of flesh from the rib area the time frame for the depositional context of the costa suggests that the striations may have been made by one of several possible human taxa that occurred in central europe during this period including homo heidelbergensis given the dearth of human skeletal remains from this region and time period this represents the earliest and only example of middle pleistocene human butchering activity in poland the remains discussed in this paper are presented in light of their depositional and cultural contexts which not only increases our knowledge of the occurrence of m trogontherii in poland but also provides increased evidence for lower palaeolithic human activity in central europe during an early interglacial

a taxonomic and taphonomic study of pleistocene fossil deposits from the western nefud desert saudi arabia over the past decade a growing interest has developed on the archaeology palaeontology and palaeoenvironments of the arabian peninsula it is now clear that hominins repeatedly dispersed into arabia notably during pluvial interglacial periods when much of the peninsula was characterised by a semiarid grassland environment during the intervening glacial phases however grasslands were replaced with arid and hyperarid deserts these millennial scale climatic fluctuations have subjected bones and fossils to a dramatic suite of environmental conditions affecting their fossilisation and preservation yet as relatively few palaeontological assemblages have been reported from the pleistocene of arabia our understanding of the preservational pathways that skeletal elements can take in these types of environments is lacking here we report the first widespread taxonomic and taphonomic assessment of arabian fossil deposits novel fossil fauna are described and overall the fauna are consistent with a well watered semiarid grassland environment likewise the taphonomic results suggest that bones were deposited under more humid conditions than present in the region today however fossils often exhibit significant attrition obscuring and fragmenting most finds these are likely tied to wind abrasion insolation and salt weathering following fossilisation and exhumation processes particularly prevalent in desert environments

crustal structure of the azores archipelago from rayleigh wave ellipticity data determining the crustal structure of ocean island volcanoes is important to understand the formation and tectonic evolution of the oceanic lithosphere and tectonic swells in marine settings and to assess seismic hazard in the islands the azores archipelago is located near a triple junction system and is possibly under the influence of a mantle plume being at the locus of a wide range of geodynamic processes however its crustal structure is still poorly constrained and debated due to the limited seismic coverage of the region and the peculiar linear geometry of the islands to address these limitations in this study we invert teleseismic rayleigh wave ellipticity measurements for 1 d shear wave speed vs crustal models of the azores archipelago moreover we test the reliability of these new models by using them in independent moment tensor inversions of local seismic data and demonstrate that our models improve the waveform fit compared to previous models we find that data from the westernmost seismic stations used in this study require a shallower moho depth 10 km than data from stations in the eastern part of the archipelago 13 16 km this apparent increase in the moho depth with increasing distance from the mid atlantic ridge mar is expected however the rate at which moho deepens away from the mar is greater than that predicted from a half space cooling model suggesting that local tectonic perturbations have modified crustal structure the 1 d vs models obtained beneath the westernmost seismic stations also show higher wave speeds than for the easternmost stations which correlates well with the ages of the islands except santa maria island we interpret the relatively low vs profile found beneath santa maria island as resulting from underplating which agrees with previous geological studies of the island compared to a recent receiver function study of the region the shallow structure top 2 km in our models shows lower shear wave speed which may have important implications for future hazard studies of the region more generally the new seismic crustal models we present in this study will be useful to better understand the tectonics seismicity moment tensors and strong ground motions in the region

taphonomy of debris flow hosted dinosaur bonebeds at dalton wells utah lower cretaceous cedar mountain formation usa abstract a taphonomic study of the lower cretaceous dalton wells dw dinosaur bonebeds near moab utah provides insight into the origins preservational biases and paleobiological significance of one of the richest and most diverse early cretaceous dinosaur sites known the bonebeds occur in a stacked succession of debris flows at the base of the yellow cat member of the cedar mountain formation which was deposited in a seasonally dry alluvial lacustrine setting although only 5 of the locality has been collected more than 4200 bones were recovered representing an assemblage overwhelmingly dominated by dinosaurs with a minimum of 67 individuals that represent at least eight genera the assemblage also includes eight elements from four non dinosaurian reptiles the dinosaur fauna is sauropod dominated mni minimum number of individuals 41 a basal macronarian mni 15 venenosaurus mni 3 a camarasaurid mni 2 and a large number mni 21 of generically unassigned sauropod elements other dinosaurs include the theropods utahraptor mni 9 nedcolbertia mni 2 a possible ornithomimid mni 2 plus a large iguanodontid mni 4 and the ankylosaurid gastonia mni 9 patterns of skeletal articulation and clustering ontogenetic representation and bone surface modification indicate that the assemblage accumulated and was exposed for more than a year as the result one or more multiple mass mortality events likely droughts that culled large numbers of subadults from the biocoenose carcasses and disarticulated elements were reworked then later transported a short distance and buried by a succession of debris flows skeletal representation data patterns of sorting breakage burrows abrasion and scratch marks provide evidence for sorting trampling and scavenging prior to debris flow reworking pre debris flow sorting is attributed to earlier hydraulic winnowing of easily transported elements the intensity and thoroughness of breakage involving 97 of the elements suggest highly focused high load impacts compatible with trampling by sauropods and iguanodontids lightly abraded and vertically displaced elements indicate episodes of trampling in soft mud trampling occurred before and after debris flow transport theropod tooth marks are uncommon but bone scavenging by osteophagous insects was common and severe resulting in substantial damage to articular surfaces comparisons of dw and other debris flow hosted bonebeds indicate that there are few consistent patterns among fossil assemblage and bone modification data however there are numerous similarities in the geological and spatial taphonomy datasets from these sites resulting from the similar physico hydraulic conditions under which elements were transported reworked and buried geologically and taphonomically dalton wells is similar to the blagoveshchensk monodominant hadrosaur bonebed in the udurchukan formation of eastern russia which also is interpreted as a debris flow hyperconcentrated flow deposit dalton wells also shares geologic and taphonomic characteristics with four bonebeds southeast of the town of green river utah and all occur at the base of the yellow cat member the uniform stratigraphic occurrences of the dalton wells blagoveshchensk and the green river sites resting on an unconformity and their shared sedimentologic and taphonomic features indicate that these sites originated in response to similar tectonic depositional and biostratinomic factors

resolving crustal thickness using ss waveform stacks we image lithospheric interfaces using variations in the character of ss waveform stacks a method we term ss lithospheric interface profiling sslip the variations are caused by reflected phases that is underside reflections ss precursors and topside multiples ss reverberations created at velocity discontinuities near the midpoint of the ss ray path stacks from continental versus oceanic bounce point regions produce distinctly different ss waveforms consistent with the large continent ocean difference in crustal thickness to investigate the potential of ss waveform stacks to constrain moho depths under continents we develop a method to fit continental bounce point stacks with a reference ss waveform convolved with a crustal operator the sslip inferred moho depths agree with the crust 2 0 model in asia for those regions where the ss bounce point density is the highest the sslip depths are correlated correlation coefficient 0 82 with the crust 2 0 values averaged over sample bins of 10 radius the sslip method has broad lateral resolution in comparison to most other methods for resolving crustal thickness but has the potential to sample regions where station coverage may be sparse

water rich sublithospheric melt channel in the equatorial atlantic ocean the lithosphere asthenosphere boundary is the most extensive boundary on earth separating the mobile plate above from the convecting mantle below but its nature remains a matter of debate using an ultra deep seismic reflection technique here we show a systematic seismic image of two deep reflectors that we interpret as the upper and lower limits of the lithosphere asthenosphere boundary beneath a 40 70 million year old oceanic lithosphere in the atlantic ocean these two reflections correspond to 1 260 c and 1 355 c isotherms and bound a low velocity channel suggesting that the lithosphere asthenosphere boundary is thermally controlled we observe a clear age dependency of this sublithospheric channel its depth increases with age from 72 km where it is 40 myr old to 88 km where it is 70 myr old whereas its thickness decreases with age from 18 km to 12 km we suggest that partial melting facilitated by water is the main mechanism responsible for the low velocity channel the required water concentration for melting increases with age nevertheless its corresponding total mass remains relatively constant suggesting that most of the volatiles in the oceanic sublithospheric channel originate from a horizontal flux near the ridge axis

trans pacific upper mantle shear velocity structure 1 we use 50 tonga fiji events recorded at the broadband trinet array southern california to develop a pure path upper mantle shear velocity model across the pacific at the epicentral distances of 70 95 multibounce s waves up to s5 are observed including their triplicated branches which become particularly clear after stacking since these s wave multiples turn at various depths simultaneously modeling their differential traveltimes and waveforms provides strong constraints on the radial velocity structure we parameterize the velocity model according to a priori information from the previous oceanic models so that we can take a grid search approach to fully investigate possible interdependencies among the model parameters we construct synthetics with a reflectivity code and study both the sh and sv components by modeling the whole recordings from events at different depths with different mechanisms we are able to separate shallow low velocity zone lvz features from deeper structure our preferred model pac06 contains a fast lid vsh 4 78 km s 1 vsv 4 58 km s 1 with a thickness of 60 km the underlying lvz is prominent with the lowest velocities vsh 4 34 km s 1 and vsv 4 22 km s 1 occurring at a depth of 160 km these velocities are below the estimates of solid state lvz suggesting the presence of partial melt the anisotropy vsv vsh of pac06 extends to 300 km depth which is constrained by s5 turning at this depth besides the 406 km and 651 km discontinuities pac06 also has a small 1 velocity jump at 516 km we consider these main features of pac06 to be well determined since pac06 explains a large data set from various events therefore it is ideally suited for comparing with mineralogical models

low seismic velocities below mid ocean ridges attenuation versus melt retention the first comprehensive seismic experiment sampling subridge mantle revealed a pronounced low velocity zone between 40 and 100 km depth below the east pacific rise epr that has been attributed to substantial retained melt fractions of 0 3 2 such high melt fractions are at odds with low melt productivity and high melt mobility inferred from petrology and geochemistry here we evaluate whether seismic attenuation can reconcile subridge seismic structure with low melt fractions we start from a dynamic spreading model which includes melt generation and migration and is converted into seismic structure accounting for temperature pressure composition phase and melt dependent anharmonicity and temperature pressure frequency and hydration dependent anelasticity our models predict a double low velocity zone a shallow approximately triangular region due to dry melting and a low velocity channel between 60 and 150 km depth dominantly controlled by solid state high temperature seismic attenuation in a damp mantle with only a minor contribution of 0 1 melt we test how tomographic inversion influences the imaging of our modeled shear velocity features the epr experiment revealed a double low velocity zone but most tomographic studies would only resolve the deeper velocity minimum experimentally constrained anelasticity formulations produce vsas low as observed and can explain lateral variations in near ridge asthenospheric vs with 100 k temperature variations and or zero to high water content furthermore such qs formulations also reproduce low asthenospheric vs below older oceans and continents from basic lithospheric cooling models although these structures are compatible with global qs images they are more attenuating than permitted by epr data

cut marks and raw material exploitation in the lower pleistocene site of bell s korongo bk olduvai gorge tanzania a geometric morphometric analysis the lower pleistocene site of bell s korongo bk in olduvai gorge tanzania has been a key site for the study of the origin of human behaviour the lower archaeological levels of bk are characterized by anthropogenic activity related to the exploitation of megafauna elephant hippopotamus sivatherium and smaller game zebra wildebeest and antelopes these remains display a high frequency of cut marks the exceptional state of preservation of the bk fossil assemblage has allowed a wide range of different analyses that among other things detected the use of quartzite in butchering activities through the study of cut marks following up previous analyses this paper presents the study of a series of cut marks from the bk faunal assemblage using a 3d geometric morphometric methodological approach in order to determine the mineralogical properties of the quartzite used at the site bk cut marks are compared with experimentally produced cut marks using 9 mineralogically different quartzite types from olduvai gorge this comparative analysis provides valuable hints about the exact nature of the raw materials used in butchering activities the results presented here identify a preferential use of quartzite with a finer granular composition suggesting that hominin populations were already selecting the best raw materials for their use in specific activities 1 3 mya

split comets and the origin of crater chains on ganymede and callisto when the voyager 1 spacecraft flew through the jovian system in january 1979 it returned images of several prominent chains of impact craters on the surface of the moon callisto fig 1 these impressively straight chains or catenae are composed of between 4 and 25 craters and are up to 620 km long they were initially thought to be secondary craters produced by debris from a larger primary impact1 but detailed searches for source craters have been largely unsuccessful a satisfactory explanation for the crater chains has yet to be found inspired by the recent observations of comet shoemaker levy 9 which split into a line of about 20 fragments as it swept past jupiter2 we suggest that the impact of previous split comets might be responsible for at least some of the catenae on callisto in support of this hypothesis we find that nearly all of callisto s crater chains are on the jupiter facing hemisphere as are an additional three catenae that we have found on ganymede we present a simple model of tidal breakup which both reproduces the range of observed chain lengths and indicates that the parent comets responsible for the callisto catenae were typically no more than about 10 km in diameter

changes in seismic anisotropy shed light on the nature of the gutenberg discontinuity the boundary between the lithosphere and asthenosphere is associated with a platewide high seismic velocity lid overlying lowered velocities consistent with thermal models seismic body waves also intermittently detect a sharp velocity reduction at similar depths the gutenberg g discontinuity which cannot be explained by temperature alone we compared an anisotropic tomography model with detections of the g to evaluate their context and relation to the lithosphere asthenosphere boundary lab we find that the g is primarily associated with vertical changes in azimuthal anisotropy and lies above a thermally controlled lab implying that the two are not equivalent interfaces the origin of the g is a result of frozen in lithospheric structures regional compositional variations of the mantle or dynamically perturbed lab

ambiguities in human and elephant interactions stories of bones sand and water from castel di guido italy geoarchaeological and taphonomical studies have been carried out on the sequence and on the faunal remains of castel di guido central italy a middle pleistocene site with acheulean industry and faunas including elephas palaeoloxodon antiquus bos primigenius equus ferus and other taxa investigation focused on remains accumulated on the bottom of a depressed area probably an ephemeral stream channel sometimes acting as a seep the assemblage resulted prevalently from human activity as shown by the selection of the faunas by the thorough fracturing of the bones and by the occurrence of abundant chipped stone industry and bone bifaces it is still a matter of debate whether the animals were hunted or scavenged the present day distribution of the remains does not represent exactly their original configuration as in most sites of this type and age more likely the objects are partly in their original position and partly reworked and lie within a complex palimpsest of several phases of fluvial transport and human activity with the addition of external inputs of reworked bones and artefacts

neotaphonomic measures of carnivore serial predation at ngamo pan as an analog for interpreting open air faunal assemblages abstract here i present a neotaphonomic account of natural bone accumulations that have resulted from carnivore serial predation at ngamo pan a vast complex of seasonal water holes located in hwange national park zimbabwe reconstructing the taphonomic histories of faunal assemblages from open air archaeological sites is burdened with a host of interpretive complications and this study is offered as a referential means for evaluating instances where stone tools and bone accumulations are associated in apparent archaeological contexts while the presence of stone tools implies some involvement on the part of humans open air sites near water would also have served as prime locations for serial predation by large carnivores to ambush prey a situation that over time can mimic archaeological bone accumulations the taphonomic and zooarchaeological signatures of carnivore serial predation at ngamo pan show marked similarities with the open air faunal accumulation from kalkbank a late pleistocene site in limpopo province south africa located along the margins of a relict pan many potential archaeological sites within the interior of southern africa dating to the middle stone age are known from open air settings near permanent or ephemeral bodies of water and the ability to decipher between hominin and non hominin carnivore involvement with bone accumulations is paramount in determining the hunting and scavenging behaviors of our early ancestors as much of our understanding of hominin subsistence during the middle stone age is drawn from coastal cave locations this study is intended to encourage a broadening of our perspective on the taphonomic histories of faunal accumulations dating to the middle stone age by incorporating supplementary evidence provided by these open air sites

cometary nuclei and tidal disruption the geologic record of crater chains on callisto and ganymede prominent crater chains on ganymede and callisto are most likely the impact scars of comets tidally disrupted by jupiter and are not secondary crater chains we have examined the morphology of these chains in detail in order to place constraints on the properties of the comets that formed them and the disruption process in these chains intercrater spacing varies by no more than a factor of 2 and the craters within a given chain show almost no deviation from linearity although the chains themselves are on gently curved small circles all of these crater chains occur on or very near the jupiter facing hemisphere for a given chain the estimated masses of the fragments that formed each crater vary by no more than an order of magnitude the mean fragment masses for all the chains vary by over four orders of magnitude w b mckinnon and p m schenk 1995 geophys res lett 13 1829 1832 however the mass of the parent comet for each crater chain is not correlated with the number of fragments produced during disruption but is correlated with the mean mass of the fragments produced in a given disruption event also the larger fragments are located near the center of each chain all of these characteristics are consistent with those predicted by disruption simulations based on the rubble pile cometary nucleus model in which nuclei are composed on numerous small fragments weakly bound by self gravity and with those observed in comet d shoemaker levy 9 similar crater chains have not been found on the other icy satellites but the impact record of disrupted comets on callisto and ganymede indicates that disruption events occur within the jupiter system roughly once every 200 to 400 years

determination of intrinsic attenuation in the oceanic lithosphere asthenosphere system we recorded p and s waves traveling through the oceanic lithosphere asthenosphere system las using broadband ocean bottom seismometers in the northwest pacific and we quantitatively separated the intrinsic anelastic and extrinsic scattering attenuation effects on seismic wave propagation to directly infer the thermomechanical properties of the oceanic las the strong intrinsic attenuation in the asthenosphere obtained at higher frequency 3 hertz is comparable to that constrained at lower frequency 100 seconds by surface waves and suggests frequency independent anelasticity whereas the intrinsic attenuation in the lithosphere is frequency dependent this difference in frequency dependence indicates that the strong and broad peak dissipation recently observed in the laboratory exists only in the asthenosphere and provides new insight into what distinguishes the asthenosphere from the lithosphere

bois de riquet lezignan la cebe herault a late early pleistocene archeological occurrence in southern france the bois de riquet archeological site lezignan la cebe herault france provides significant paleontological and archeological data about the first occupations of western europe although only partially excavated the site has already yielded an exceptionally rich paleontological assemblage as well as some stone artefacts the archeostratigraphical unit us2 is encased within a basalt flowstone radiometrically dated to 1 57 ma the sedimentary infill has preserved large and small mammal fossils as well as coprolites biochronological interpretations suggest an age of around 1 3 1 1 ma for the accumulation a few basalt artefacts were exhumed alongside the fossil bones interpretation of the lithics has required the elaboration of a strict selection protocol based upon extensive knapping experiments with local basalt this paper presents results from the interdisciplinary study of the bois de riquet site in the aim of contextualizing these discoveries the microstratigraphical analysis of the deposits is presented with recent geological interpretations in order to contribute a better understanding of the main features of this assemblage and its remarkable preservation within the thermal and textural boundary between a basalt flowstone s base and its entablature

trampling in coastal sites an experimental study on the effects of shell on bone in coastal sediment abstract faunal remains are often recovered from shelly deposits in coastal sites but little is known about the trampling effects of shell on bone here trampling experiments were conducted to investigate these effects and to describe the types of surface modification that could occur on bone in coastal sediment the results suggest that bone is significantly more likely to exhibit surface modification if trampled in shelly rather than sandy sediment burnt bone is less likely to display trampling modification this is probably because prior to trampling burning exfoliates the cortex making the observation of markings on bone problematic pitting trampling lines and sheen were found to be the most prevalent form of surface modification pitting is a particularly over looked criterion and its presence on archaeological bone suggests that the effects of trampling should be considered in zooarchaeological analyses the pervasiveness of sheen and trampling lines on the experimental bone makes it possible that some incidence of trampling could be mistaken for use wear or intentional polish however the vast majority of trampled bone exhibits sheen which does not resemble anthropogenic specimens and trampling is unlikely to smooth bone fragment edges this experiment demonstrates that modification caused by trampling can generally be differentiated from butchery markings the high percentage of modified trampled bone in the shelly deposits suggests that some shell marks may be mistaken for cut marks if recovered in an archaeological context

testing heterogeneity in faunal assemblages from archaeological sites tumbling and trampling experiments at the early middle pleistocene site of gesher benot ya aqov israel abstract the current paper reports an experimental case study to test the heterogeneity of faunal assemblages from the early middle pleistocene layers v 5 and v 6 of the gesher benot ya aqov acheulian site israel tumbling and trampling experiments were initiated to gain qualitative insight into processes of bone modification and to assess the timing of the biostratonomic chronology as it was assumed that both mechanisms were responsible for the formation of striations documented on the bone surfaces from the site the tumbling experiments mimicked sediment movement in a calm lacustrine shoreline environment whereas the trampling experiments investigate the role of animal hominin activities in dry muddy and wet environments models for the internal operational sequence of an abrasional process due to uni and multidirectional water movement and of a trampling scenario are presented these models are used for the interpretation of the fauna from gesher benot ya aqov

implications of grain size evolution on the seismic structure of the oceanic upper mantle abstract we construct a 1 d steady state channel flow model for grain size evolution in the oceanic upper mantle using a composite diffusion dislocation creep rheology grain size evolution is calculated assuming that grain size is controlled by a competition between dynamic recrystallization and grain growth applying this grain size evolution model to the oceanic upper mantle we calculate grain size as a function of depth seafloor age and mantle water content the resulting grain size structure is used to predict shear wave velocity v s and seismic quality factor q for a plate age of 60 myr and an olivine water content of 1000 h 10 6 si we find that grain size reaches a minimum of 15 mm at 150 km depth and then increases to 20 30 mm at a depth of 400 km this grain size structure produces a good fit to the low seismic shear wave velocity zone lvz in oceanic upper mantle observed by surface wave studies assuming that the influence of hydrogen on anelastic behavior is similar to that observed for steady state creep further it predicts a viscosity of 10 19 pa s at 150 km depth and dislocation creep to be the dominant deformation mechanism throughout the oceanic upper mantle consistent with geophysical observations we predict larger grain sizes than proposed in recent studies in which the lvz was explained by a dry mantle and a minimum grain size of 1 mm however we show that for a 1 mm grain size diffusion creep is the dominant deformation mechanism above 100 200 km depth inconsistent with abundant observations of seismic anisotropy from surface wave studies we therefore conclude that a combination of grain size evolution and a hydrated upper mantle is the most likely explanation for both the isotropic and anisotropic seismic structure of the oceanic upper mantle our results also suggest that melt extraction from the mantle will be significantly more efficient than predicted in previous modeling studies that assumed grain sizes of 1 mm

a theropod dinosaur feeding site from the upper jurassic of the junggar basin nw china abstract direct evidence for theropod feeding behaviour is rare in the fossil record and mainly limited to bite marks on bones here we describe a dinosaur assemblage from the lower part of the early late jurassic qigu formation at liuhuanggou gorge southern junggar basin nw china which has yielded fragmentary remains of a large sauropod as well as four teeth of large sized theropods and one tooth of a small sized theropod the sauropod bones show numerous bite marks that can be confidently linked to the large sized theropod probably a metriacanthosaurid the abundance of the theropod bite marks on a single skeleton indicates that the sauropod carcass was probably fed on extensively some bones are completely crushed and occur in patches of hundreds of tiny individual fragments indicating that they were trampled repeatedly by large dinosaurs both the feeding traces and the trampling suggests that the sauropod carcass was exposed for a substantial amount of time before it was finally buried within the deposits of a well drained floodplain the traces and the distinct preservation of the sauropod remains offer valuable insights into the feeding behaviour of large sized theropods within late jurassic continental ecosystems

taphonomy of palaeloxodon antiquus at castel di guido rome italy proboscidean carcass exploitation in the lower palaeolithic field investigations at castel di guido revealed a middle pleistocene open air site containing macrofaunal remains associated with acheulean industry the large majority of the remains lay at the bottom of a depressed area which probably evolved into a low energy freshwater basin after the deposition of the assemblage to quantify the importance of the natural processes compared to the anthropogenic ones in the formation of the site a full taphonomic analysis of the macromammal assemblage was carried out a geoarchaelogical study together with a taphonomic analysis of the lithic and bone implements is ongoing this paper discusses the results of the study of elephant bones the taphonomic analysis has documented traces of different modifying agents on the specimens indicating the important role of syn and post depositional factors in the accumulation and modification of bones nevertheless evidence of utilization of carcasses for subsistence and for tool production was detected the study provides new data for the exploitation of elephants by hominins during the lower palaeolithic

ponded melt at the boundary between the lithosphere and asthenosphere the boundary between earth s rigid lithosphere and ductile asthenosphere is marked by a seismic discontinuity laboratory experiments on basaltic magmas show that melts should pond at pressures that correspond to the lithosphere asthenosphere boundary thus magma ponding could explain the observed seismic discontinuity

lithospheric structure across the california continental borderland from receiver functions due to its complex history of deformation the california continental borderland provides an interesting geological setting for studying how the oceanic and continental lithosphere responds to deformation we map variations in present day lithospheric structure across the region using ps and sp receiver functions at permanent stations of the southern california seismic network as well as ocean bottom seismometer obs data gathered by the asthenospheric and lithospheric broadband architecture from the california offshore region experiment albacore which enhances coverage of the borderland and provides first direct constraints on the structure of the pacific plate west of the patton escarpment noisiness of obs data makes strict handpicking and bandpass filtering necessary in order to obtain interpretable receiver functions using h and common conversion point stacking we find pronounced lithospheric differences across structural blocks which we interpret as indicating that the outer borderland has been translated with little to no internal deformation while the inner borderland underwent significant lithospheric thinning most likely related to accommodating the 90 clockwise rotation of the western transverse range block west of the patton escarpment we find that the transition to typical oceanic crustal thickness takes place over a lateral distance of 50 km we detect an oceanic seismic lithosphere asthenosphere transition at 58 km depth west of the patton escarpment consistent with only weak age dependence of the depth to the seismic lithosphere asthenosphere transition sp common conversion point stacks confirm wholesale lithospheric thinning of the inner borderland and suggest the presence of a slab fragment beneath the outer borderland

cutmarks made by stone tools on bones from olduvai gorge tanzania fossils from olduvai gorge tanzania show cutmarks which establish that hominids were using stone tools on animal tissues during the lower pleistocene in africa we identified cutmarks by elimination of other likely causes of the marks on the bone surfaces for example gnawing or chewing by carnivores or rodents and damage made by tools of excavators or preparators this was achieved by comparing the marks on the fossils with those produced by known causes on modern bones using scanning electron microscopy sem because the fossils occur as part of accumulations of animal remains in relatively undisturbed geological contexts we conclude that there is a functional association between the stone artefacts and bones at these sites rather than an accidental postmortem association1 2

the late pleistocene pilauco site osorno south central chile abstract paleontological and archaeological sites have frequently been found in open locations of the intermediate depression of south central chile this paper presents the results of two field sampling seasons carried out at the pilauco site ca 39 s and compares them with those of three well known sites in chile quereo tagua tagua and monte verde ca 32 34 and 41 s respectively stratigraphic data collected at pilauco and the resulting radiocarbon age model suggest that before 12 540 90 bp the old damas river eroded an older volcaniclastic hill which was followed by a bog formation in an ox bow lake the site was developing up to 11 004 186 bp the date of the youngest vertebrate fossil two younger peat beds seal the site as in tagua tagua and monte verde gomphotheres are the most represented megafauna fossils of equidae camelidae cervidae mephitidae muridae myocastoridae and xenarthra are also found in pilauco as a whole 718 bones 30 teeth and 11 coprolites represent the extinct and extant vertebrates preliminary taphonomic results suggest action of various agents in the bones i e trampling root etching abrasion and carnivore gnawing the spatial analysis suggests the transfer of smaller anatomical units e g bones of camelids and horses and the rearrangement of some pieces comparatively large e g gomphothere bones similar to the present day north patagonian landscape the area where pilauco site is located had a variety of animal resources plants and stones in an ecotone between hills floodplains and wetlands a total of 101 lithics were recorded basalt and quartzite were collected from nearby fluvial deposits and dacitic obsidian from the local volcaniclastic deposits debitage is the most represented lithic item 75 cores and marginal edge trimmed artifacts represented 12 and 13 respectively artifacts and flakes are spatially and temporality associated in the same pb 7 bed with high bone concentrations in some specific areas between 361 and 424 cm of local altitude this industry is characterized by a recurrent lithic expedite technology with production of flakes and chips which mastered marginal retouches over the bifacial trimming this seems to be connected to strategic conditions of high resource diversity especially of human groups with a high or medium mobility across land pilauco represents a site contemporaneous to monte verde related as well to the first human occupation in the southern cone of south america but with higher mammal diversity

cut marks made with quartz tools an experimental framework for understanding cut mark morphology and its use at the middle palaeolithic site of the navalmaillo rock shelter pinilla del valle madrid spain abstract the study of cut marks in archaeological contexts is of great importance for understanding the subsistence strategies of past human groups many authors have indicated differences to exist between the cut marks produced by different tools and when the same types of tool have been made from different raw materials the present work examines the cut marks made during the experimental butchering of a red deer cervus elaphus using simple quartz flakes with those found on fossilised animal remains at the navalmaillo rock shelter site pinilla del valle madrid spain likely to have been made with similar flakes the methodology followed was that of dominguez rodrigo et al 2009 which was originally designed to differentiate between cut marks and trampling marks but which here was tested as a method of distinguishing between the raw materials from which cutting tools were made the results were also compared to those made with other types of tool raw material reported in the literature the present results confirm the above ideas the marks made experimentally by the quartz flakes are very similar to those seen on the faunal remains from the level f of navalmaillo rock shelter site but different to those made by other tools or by flakes made from other materials they also show however that different cut mark morphologies are largely independent of the size of the animal butchered and of the anatomical element on which they appear

constraints on the anisotropic contributions to velocity discontinuities at 60 km depth beneath the pacific strong sharp negative seismic discontinuities velocity decreases with depth are observed beneath the pacific seafloor at 60 km depth it has been suggested that these are caused by an increase in radial anisotropy with depth which occurs in global surface wave models here we test this hypothesis in two ways we evaluate whether an increase in surface wave radial anisotropy with depth is robust with synthetic resolution tests we do this by fitting an example surface wave data set near the east pacific rise we also estimate the apparent isotropic seismic velocity discontinuities that could be caused by changes in radial anisotropy in s to p and p to s receiver functions and ss precursors using synthetic seismograms we test one model where radial anisotropy is caused by olivine alignment and one model where it is caused by compositional layering the result of our surface wave inversion suggests strong shallow azimuthal anisotropy beneath 0 10 ma seafloor which would also have a radial anisotropy signature an increase in radial anisotropy with depth at 60 km depth is not well resolved in surface wave models and could be artificially observed shallow isotropy underlain by strong radial anisotropy could explain moderate apparent velocity drops 6 in ss precursor imaging but not receiver functions the effect is diminished if strong anisotropy also exists at 0 60 km depth as suggested by surface waves overall an increase in radial anisotropy with depth may not exist at 60 km beneath the oceans and does not explain the scattered wave observations

the gutenberg discontinuity melt at the lithosphere asthenosphere boundary the lithosphere asthenosphere boundary lab beneath ocean basins separates the upper thermal boundary layer of rigid conductively cooling plates from the underlying ductile convecting mantle the origin of a seismic discontinuity associated with this interface known as the gutenberg discontinuity g remains enigmatic high frequency ss precursors sampling below the pacific plate intermittently detect the g as a sharp negative velocity contrast at 40 to 75 kilometer depth these observations lie near the depth of the lab in regions associated with recent surface volcanism and mantle melt production and are consistent with an intermittent layer of asthenospheric partial melt residing at the lithospheric base i propose that the g reflectivity is regionally enhanced by dynamical processes that produce melt including hot mantle upwellings small scale convection and fluid release during subduction