a diffusion adsorption model of uranium uptake by archaeological bone abstract an argument for the possibility of uranium uptake by buried bone taking place through the adsorption of uranyl species on bone mineral is advanced in the light of this a diffusion adsorption model for uranium uptake by buried bone is developed the necessary constants are evaluated from the literature and from laboratory measurements of the partition coefficient between solution and bone mineral the geochemical and hydrological parameters which control uptake are discussed the predictions of the model are shown to be in general accordance with the timescale magnitude and distribution of uranium uptake in archaeological bone using the model specific predictions of the variation of apparent uranium series ages in bone can be made and bone is shown clearly not to conform to the closed system assumption when the model is extended to tooth enamel it is found to be incompatible with the early uptake model used for esr dating but to fall between the early uptake and linear uptake models similarly it suggests that uranium series dates on enamel assuming a closed system are liable to underestimate the true age by at least one third

tectonic plate generation and two phase damage void growth versus grain size reduction 1 the generation of plate tectonics from mantle convection requires shear localization in order to yield narrow weak plate boundaries separating broad strong plates a plausible shear localizing mechanism involves damage e g distributed microcracking one theoretical model of which involves two phase mechanics two phase damage theory employs a nonequilibrium relation between interfacial surface energy pressure and viscous deformation thereby providing a description of void generation and microcracking and hence weakening failure and shear localization here we examine the application of this theory to the problem of generating plate like behavior from convective type divergent convergent poloidal motion through a source sink formulation we extend the previous damage theory to consider two possible damage effects 1 growth and nucleation of voids associated with dilation of the host matrix and 2 increasing fineness i e reducing coarseness of the mixture by for example grain size reduction void generating damage is found to be poor at plate generation because of the predominance of dilational motion that is adverse to the development of plate like flow fineness generating damage is found to be very efficient at generating plate like behavior if we assume that the matrix viscosity is a simple function of grain void size as is typical for diffusion creep the implied grain size reduction mechanism is different from that of dynamic recrystallization and appears to be more capable of generating the requisite shear localization for forming tectonic plates from mantle flow

early diagenesis of bone and tooth apatite in fluvial and marine settings constraints from combined oxygen isotope nitrogen and ree analysis abstract fossil bones and teeth of late pleistocene terrestrial mammals from rhine river gravels rs and the north sea ns that have been exposed to chemically and isotopically distinct diagenetic fluids fresh water versus seawater were investigated to study the effects of early diagenesis on biogenic apatite changes in phosphate oxygen isotopic composition 18opo4 nitrogen content wt n and rare earth element ree concentrations were measured along profiles within bones that have not been completely fossilized and in skeletal tissues bone dentine enamel with different susceptibilities to diagenetic alteration early diagenetic changes of elemental and isotopic compositions of apatite in fossil bone are related to the loss of the stabilizing collagen matrix the ree concentration is negatively correlated with the nitrogen content and therefore the amount of collagen provides a sensitive proxy for early diagenetic alteration ree patterns of rs and ns bones indicate initial fossilization in a fresh water fluid with similar ree compositions bones from both settings have nearly collagen free ree u f and sr enriched altered outer rims while the collagen bearing bone compacta in the central part often display early diagenetic pyrite void fillings however ns bones exposed to holocene seawater have outer rim 18opo4 values that are 1 1 to 2 6 higher compared to the central part of the same bones 18opo4 18 2 0 9 n 19 surprisingly even the collagen rich bone compacta with low ree contents and apatite crystallinity seems altered as ns tooth enamel 18opo4 15 0 0 3 n 4 has about 3 lower 18opo4 values values that are also similar to those of enamel from rs teeth therefore ree concentration n content and apatite crystallinity are in this case only poor proxies for the alteration of 18opo4 values seawater exposure of a few years up to 8 kyr can change the 18opo4 values of the bone apatite by 3 therefore bones fossilized in marine settings must be treated with caution for palaeoclimatic reconstructions however enamel seems to preserve pristine 18opo4 values on this time scale using species specific calibrations for modern mammals a mean 18oh2o value can be reconstructed for late pleistocene mammalian drinking water of around 9 2 0 5 which is similar to that of late pleistocene groundwater from central europe

effect of three dimensional slab geometry on deformation in the mantle wedge implications for shear wave anisotropy shear wave splitting observations from many subduction zones show complex patterns of seismic anisotropy that commonly have trench parallel fast directions three dimensional flow may give rise to trench parallel stretching and provide an explanation for these patterns of seismic anisotropy along strike variations in slab geometry produce trench parallel pressure gradients and are therefore a possible mechanism for three dimensional flow in this study we quantify the effects of variable slab dip curved slabs oblique subduction and slab edges on flow geometry and finite strain in the mantle wedge of subduction zones temperature dynamic pressure velocity and strain are calculated with high resolution three dimensional finite element models these models include temperature and stress dependent rheology and parameterized slab and trench geometry thick layers 20 60 km with strong trench parallel stretching are observed in the mantle wedge when slab geometry involves a transition to slab dip less than 15 or strong curvature in the slab in these cases strong trench parallel stretching develops when flow lines have an oblique to trench normal orientation this suggests that trench parallel seismically fast directions may not indicate trench parallel flow lines in systems with large along strike variations an oblique component of stretching is confined to a 20 30 km layer above the slab in systems with oblique subduction the effects of slab edges include strong toroidal flow and focusing in the mantle near slab edges and trench parallel flow that extends 50 100 km into the core of the mantle wedge

u series dating of bone using the diffusion adsorption model abstract u series dating of bone has suffered problems of reliability since its inception because bone remains an open system with respect to uranium commonly applied a priori assumptions of u uptake such as early uptake or linear uptake are inadequate because they have no physical or chemical bases no means of demonstrating which model is suitable for a particular bone and no intrinsic tests of reliability despite this and numerous examples of anomalous u series dates such assumptions are still routinely applied we address this problem using the diffusion adsorption d a model of u uptake millard and hedges 1996 which incorporates a physicochemical description of u uptake using this model we show how the u uptake of a bone responds to geochemical changes in the burial environment which can lead to phenomena such as the removal of u from bones leaching or u uptake late in their burial history recent uptake and we show how the overall uptake history is reflected in distributions profiles of u and u series isotopes across a bone section we present measurements of u concentration profiles and 230 th 234 u profiles on archeological bone from a number of different sites and burial environments and compare the results to profiles predicted by the d a model bones that have undergone complex uptake histories which include u leaching or recent uptake are identified on the basis of these profiles and rejected as unsuitable for dating for bones that appear to have undergone uptake under constant geochemical conditions the d a model is applied to calculate u series dates with much improved reliability

diagenetic arsenic uptake in archaeological bone can we really identify copper smelters in a recent paper oakberg levy smith 2000 reported measurements of arsenic concentrations in bone from the chalcolithic site of shiqmim israel they inferred that since elevated levels of as had been found in the bone of modern copper smelter workers in sweden high concentrations in archaeological bone could be used to infer copper smelting activities in the past however their argument ignores the effects of post depositional mobility of arsenic between soil groundwater and bone here we outline the processes influencing mobilization of as and post depositional as incorporation in bone we argue that the as concentrations reported by oakberg levy smith 2000 can be accounted for by diagenetic uptake and are unlikely to reflect biogenic as concentrations we therefore conclude that the data presented by oakberg levy smith 2000 cannot be used to infer past copper smelting

bone diagenesis in the european holocene ii taphonomic and environmental considerations we have applied cluster analysis to mercury intrusion porosimetry data from 219 archaeological bones 121 human and 98 animal and soil chemistry data from 219 accompanying soil samples 1 per bone sample to investigate the influence of soil chemistry on bone preservation the samples chosen for the study were obtained from sites ranging in time from the pre modern to the mesolithic and were representative of burial environments across europe from the baltic to the mediterranean these results represent the single largest database for archaeological bone preservation in the european holocene to date and demonstrate the potential for large scale diagenetic studies to help develop long term preservation strategies for our european heritage despite the variety of sites and environments bones could be categorised into only four main diagenetic types furthermore soil chemistry appears to significantly affect only one type of preservation the pathway characterised by loss of mineral in neutral to basic soils taphonomy and in particular the differences between the treatment of human and animal remains becomes the dominating factor in determining preservation using these results strategies for heritage management of archaeological sites can be suggested grouping sites into those requiring immediate excavation and those where in situ preservation is viable

observations of warm water volume changes in the equatorial pacific and their relationship to el nino and la nina abstract this paper describes observed changes in surface winds sea surface temperature sst and the volume of water warmer than 20 c wwv in the equatorial pacific ocean for the period 1980 99 the purpose is to test recent hypotheses about the relationship between variations in wwv and the el nino southern oscillation enso cycle the results confirm inferences based on theory models and previous empirical analyses using proxy data namely sea level that enso involves a recharge and discharge of wwv along the equator and that the cyclic nature of enso results from a disequilibrium between zonal winds and zonal mean thermocline depth the authors also find that the magnitude of enso sst anomalies is directly related to the magnitude of zonal mean wwv anomalies furthermore for a given change in equatorial wwv the corresponding warm el nino sst anomalies are larger than the corresponding cold la nina anomalies this asymmetry between the warm and cold phases of the enso cycle implies differences

mineral microbial structures in a bone of the late cretaceous dinosaur saurolophus angustirostris from the gobi desert mongolia a raman spectroscopy study abstract bones while buried undergo diagenetic transformations the intensity of which depends on a variety of geochemical factors microbial degradation is one of the main processes acting on bones during early diagenesis we present mineral microspheres formed during bone diagenesis from the inner walls of the left tibia of the late cretaceous dinosaur saurolophus angustirostris from the gobi desert mongolia the microspheres occur either as individual bodies from a few micrometers to about 70 m in diameter or aggregated in clusters micro raman analysis shows that the microspheres are composed of various fe oxides mostly hematite and goethite that form regular reddish brown rings with organic matter at their cores the bone itself is composed for the most part of diagenetically transformed carbonate fluorapatite calcite cement was identified around the spheres and at points of contact with bone tissue negative ce anomalies indicative of ce iv in the diagenetic environment indicate oxic burial conditions all the size distribution of the microspheres their mode of occurrence and the presence of organic matter in cores surrounded by concentric fe oxide envelopes indicate early diagenetic microbially mediated mineralization in aerobic conditions the presence of microspheres and other mineral phases in the studied bone gives evidence of at least two mineralization episodes 1 fe oxide formation during an early diagenetic microbial attack on the bone and 2 later calcite barite gypsum cementation

influence of grain size evolution on convective instability 1 grain size one of the most important microstructural properties of materials evolves during creep deformation to minimize the free energy of polycrystalline aggregates we apply a model of grain size evolution to the study of convective instability of cooling boundary layers the grain size evolution model is coupled to a composite rheology where the deformation rate is the sum of that due to dislocation creep and grain size sensitive diffusion creep the onset of convection is sensitive to grain growth rates and the initial grain size the formation of convective instabilities is enhanced by stresses induced by plate motions therefore small scale convection is more likely to occur beneath fast moving plates in finite amplitude convection grain size evolution leads to high viscosity in regions where convective stresses are low and can induce viscosity contrasts exceeding one order of magnitude such viscosity contrasts are sufficient to influence the dynamics of convection often leading to domains which remain isolated from the well mixed convecting fluid a composite viscosity including diffusion creep which has a lower activation energy than dislocation creep reduces the effective temperature dependence of viscosity

contextualising the dead combining geoarchaeology and osteo anthropology in a new multi focus approach in bone histotaphonomy abstract histotaphonomy has become an important area of research in funerary archaeology it focuses on diagenetic alterations in bone microstructure and the reconstruction of post mortem processes microbial bioerosion is the most common diagenetic change observed in archaeological bone and its probable causes have been the subject of ongoing discussions this paper presents a new integrative approach that combines methods from physical anthropology and geoarchaeology the aim is to contextualise samples in regard to their sedimentary milieu sediment type the sedimentation processes they underwent and the specific archaeological features they originate from the analysis is based on 208 human and animal skeletal fragments from the late la tene site of basel gasfabrik recovered from various feature types and embedded in different sediments both 80 m and 30 m thin sections were graded semi quantitatively on a scale of 0 or 1 to 5 in regard to bacterial attack bai wedl tunnels wti cyanobacterial attack cai the formation of cracks cri the collagen content coi and thermal alterations hei our results evinced no correlations between the intensity of bacterial attack and sediment types or sedimentation processes respectively we therefore deduce that bacterial degradation of bone is mainly caused by endogenous gut bacteria wedl tunnels on the other hand are chiefly found in bones from exposed surfaces bone collagen content as measured by birefringence is dependent on a variety of factors with thermal alteration being among the most important unlike the 80 m sections used in anthropological investigations the 30 m thin sections typically utilized in geoarchaeological analyses permitted a reliable distinction of microbial bioerosion types our context oriented histotaphonomic approach allows detailed conclusions on the causes of microbial bioerosion in bone moreover it provides an important tool for reconstructing the post mortem biographies of human and animal remains especially in regard to multi stage mortuary practices and the analysis of sedimentation processes thus this novel approach generates a wealth of information from individual skeletal elements as well as from bone fragments embedded in soil samples

micro pixe pige analysis of palaeolithic mammoth ivory potential chemical markers of provenance and relative dating abstract micro proton induced x ray and gamma ray emission micro pixe pige provide non destructive methods for the evaluation of the major minor and trace element compositions of archaeological material the current study applies micro pixe pige analysis to mammoth ivory artefacts from four palaeolithic sites abri castanet vogelherd cave grottes de la verpilliere i and ii in france and germany in order to assess the effectiveness of this approach to material older than 30 000 y bp it has thus far not been established whether such methods of analysis can yield results of scientific and archaeological interest on ivory material that has undergone such extended periods of diagenesis this approach evaluated preservation state in terms of mean elemental concentrations mg vs ca and a comparative assessment of f content as an indication of relative burial time the results also indicate that analysis of trace elements sr zn br can provide chemical markers of archaeological provenance the results of this study are compared to data in the existing database established by the same methods of analysis on ivory objects from several different time periods and archaeological sources the implications of these results for the study of archaeological ivories from palaeolithic contexts are discussed

timescales for the evolution of seismic anisotropy in mantle flow 1 we study systematically the relationship between olivine lattice preferred orientation and the mantle flow field that produces it using the plastic flow recrystallization model of kaminski and ribe 2001 in this model a polycrystal responds to an imposed deformation rate tensor by simultaneous intracrystalline slip and dynamic recrystallization by nucleation and grain boundary migration numerical solutions for the mean orientation of the a axes of an initially isotropic aggregate deformed uniformly with a characteristic strain rate show that the lattice preferred orientation evolves in three stages 1 for small times recrystallization is not yet active and the average a axis follows the long axis of the finite strain ellipsoid 2 for intermediate times the fabric is controlled by grain boundary migration and the average a axis rotates toward the orientation corresponding to the maximum resolved shear stress on the softest slip system 3 for the fabric is controlled by plastic deformation and average a axis rotates toward the orientation of the long axis of the finite strain ellipsoid corresponding to an infinite deformation the infinite strain axis in more realistic nonuniform flows lattice preferred orientation evolution depends on a dimensionless grain orientation lag parameter x defined locally as the ratio of the intrinsic lattice preferred orientation adjustment timescale to the timescale for changes of the infinite strain axis along path lines in the flow explicit numerical calculation of the lattice preferred orientation evolution in simple fluid dynamical models for ridges and for plume ridge interaction shows that the average a axis aligns with the flow direction only in those parts of the flow field where 1 calculation of provides a simple way to evaluate the likely distribution of lattice preferred orientation in a candidate flow field at low numerical cost

chemical compositional changes in archaeological human bones due to diagenesis type of bone vs soil environment abstract diagenesis in human remains is a subject of growing interest due to the increase in bone chemical studies to reconstruct pre and post mortem features in archaeological and forensic sciences the efforts made during the last decades have solidified our understanding of diagenetic processes however their high complexity demands more research to address them empirically specifically considering factors such as types of soil substratum and skeletal element in this work a geochemical study of human remains from the archaeological site of a lanzada nw spain is performed to understand diagenesis i e chemical alteration and life environmental exposure three types of bone thoracic long and cranial from 30 skeletons of two periods 9 roman 21 post roman were analysed by x ray fluorescence bones were recovered from burials located in slightly alkaline haplic arenosol calcaric and acidic cambic umbrisol humic soils principal components analysis was applied to extract the main chemical signatures and analysis of variance to determine the influence of different factors bone composition was characterized by four chemical signals related to i alteration of bone bioapatite ii metal sorption from the soil solution iii presence of fine silt clay soil particles and iv lead incorporation thoracic bones were found to be more sensitive to diagenesis and the burial environment long bones and crania presented a similar response skeletons buried in the acidic soil were significantly poorly preserved lead content was higher in bones of the roman period which seems to be related to pre mortem conditions previous investigations on palaeopollution in nw spain enable us to hypothesize that roman individuals may have been subjected to a high exposure of pb due to elevated atmospheric metal contamination

a few remarks on the kinetics of static grain growth in rocks static grain growth is a relatively simple transformation in which grain size increases under driving forces caused by grain and interphase boundary curvature given the relative simplicity of the protocol for grain growth experiments measurements of grain boundary mobility show surprising variations boundary mobilities during grain growth are affected by solute and impurity chemistry chemical fugacity of trace and major elements pore size and number pore fluid chemistry the presence of melts and the presence of solid second phases as well as temperature and pressure all of these factors may exert influence on grain growth of rocks in natural situations and many are also present during the laboratory experiments provided that the necessary kinetics parameters are known bounds may be placed on the interface mobility when pores partial melts or solutes are present to predict the rate of grain growth in natural situations will require improved laboratory data and careful consideration of the thermodynamic conditions likely to be encountered in nature

systematic variation in the depths of slabs beneath arc volcanoes summary the depths to the tops of the zones of intermediate depth seismicity beneath arc volcanoes are determined using the hypocentral locations of engdahl et al these depths are constant to within a few kilometres within individual arc segments but differ by tens of kilometres from one arc segment to another the range in depths is from 65 km to 130 km inconsistent with the common belief that the volcanoes directly overlie the places where the slabs reach a critical depth that is roughly constant for all arcs the depth to the top of the intermediate depth seismicity beneath volcanoes correlates neither with age of the descending ocean floor nor with the thermal parameter of the slab this depth does however exhibit an inverse correlation with the descent speed of the subducting plate which is the controlling factor both for the thermal structure of the wedge of mantle above the slab and for the temperature at the top of the slab we interpret this result as indicating that the location of arc volcanoes is controlled by a process that depends critically upon the temperature at the top of the slab or in the wedge of mantle immediately below the volcanic arc

low temperature high stress deformation of olivine under water saturated conditions abstract low temperature high stress rheology of olivine was investigated under water saturated conditions by large strain shear deformation experiments using the griggs type apparatus samples at t 1273 1373 k and p 2 gpa under water saturated conditions deformed under a significantly lower applied stress than expected from the power law relation and the strain rate increases more rapidly with stress these observations suggest that an exponential flow law operates under the present experimental conditions in which the stress dependence of activation enthalpy is characterized by the peierls stress the peierls stress is determined between 1 6 and 2 9 gpa depending on the choice of the form of stress dependence of the activation enthalpy these values are significantly smaller than the peierls stress under dry conditions 9 1 gpa we suggest that water hydrogen incorporated in the olivine lattices decreases the peierls stress and hence the rate of deformation in the exponential creep is significantly enhanced by the presence of water the reduction of the peierls stress by water results in the highly anisotropic weakening effect of water that causes the fabric transitions in olivine the transition between the power law and the exponential creep occurs at relatively low stress 100 mpa at a geologically relevant strain rate of 10 15 s 1 when temperature is lower than 1273 k and under water rich conditions hence the exponential creep might be dominated in olivine rich rocks at low temperature and high stress under water rich conditions and such regions could be widespread in the subduction zone upper mantle where the cold lithospheric plates sink into the mantle

bones and groundwater towards the modelling of diagenetic processes this paper develops a theory for describing those diagenetic changes in bone which involve its interaction with groundwater three main processes are considered as examples of such changes namely the uptake of uranium the dissolution of bone and the increase of crystallinity of the bone mineral carbonate hydroxyapatite or dahllite here simple models of the chemistry involved are postulated although how bone interacts with water on amolecularscale is not clearly known in order to demonstrate the theory with explicit mechanisms and values greater emphasis is given to uranium uptake since the model used is comparatively detailed being based on the authors previous work the basic assumption is that the rate limiting process in diagenetic change is the movement of solutes to from or within the bone therefore the main thrust of the paper is to show how the physical structure of the bone itself together with the hydrology of the burial site interact to determine how water and its solutes move into within and from a bone during burial this interaction can be of three kinds defined by the site hydrology these are termed here diffusion hydraulic flow and recharge all three types may operate together and their relative importance depends on the extent to which the pore structure of a bone has been altered by diagenesis as well as the type of chemical change taking place it is shown that diffusion is usually the most common and important process but that it is possible to predict the hydrological regimes in which other mechanisms dominate it is shown how knowledge of site hydrology mainly the specification of soil structure and moisture variation the physical state of the bone and the chemistry of the diagenetic process can provide estimates for the rate and manner of the particular diagenetic process such estimates agree with observation suggesting this approach to be on the right lines qualitative predictions also result from the theory the main value of this approach is to identify those situations where particular diagenetic changes are simplest e g sites where the hydrology gives rise to a single and quantifiable hydraulic process so that they may be decisively tested against the quantitative predictions of the theory

measurements and relationships of diagenetic alteration of bone from three archaeological sites four diagenetic parameters have been chosen to represent the state of diagenesis of bone buried on archaeological sites they are histological preservation protein content crystallinity and porosity how these parameters are measured is described and results from populations of bones from three different sites are presented the results show the extent and variation in the degree of change both within a site and between sites in particular the correlations between diagenetic parameters are examined which give clues about the processes which cause alteration the value of porosity determinations both at the intercrystalline level and at coarser levels in revealing the degree of diagenetic change in bone and in underlying the dynamics of the interaction between buried bone and the surrounding water is stressed the data also indicate but are too restricted to prove the following microbiological attack is generally complete within less than 500 years substantial levels of protein may remain in bone after maximal micromorphological alteration loss of protein appears to be independent of other diagenetic change the correlated lose of microporosity with increase of crystallinity suggests these changes may arise from the dissolution perhaps with subsequent recrystallization of the smallest hydroxyapatite crystallites

origin of archaeological black bones within a waterlogged context a multidisciplinary approach abstract this paper presents the interdisciplinary study on the origin of black bones at the neolithic lakeside settlement of dispilio greece 5500 3500 bce where animal bones have been recovered from a waterlogged and organic soil matrix containing charcoal ash and burnt cultural remains in the past this has been interpreted as the result of the destruction of the village by fire and abandonment this study aims to examine this theory through the distinction of burnt vs oxide stained bones a selection of 44 fish and 19 mammal bone samples are examined through optical microscopy scanning electron microscopy sem x ray microanalysis eds x ray diffraction xrd rietveld analysis infrared spectroscopy atr nir and chemical analyses icp ms alterations of histology mineralogy chemistry crystallinity and structural parameters prove that the black bones from dispilio owe their colour to mn and fe oxide staining light coloured bones found at the site have not been affected by this diagenetic procedure which suggests that they were buried in a totally different geochemical environment the analytical techniques employed did not offer any proof that the studied material is burnt however due to the fact that most techniques used to this day allow for the identification of thermal alteration of bone at temperatures usually higher than 300 450 c the possibility of thermal alterations due to an indirect fire thus at lower temperatures or a fire of small duration cannot be identified and thus be ruled out

diagenesis of archaeological bone and tooth an understanding of the structural complexity of mineralised tissues is fundamental for exploration into the field of diagenesis here we review aspects of current and past research on bone and tooth diagenesis using the most comprehensive collection of literature on diagenesis to date environmental factors such as soil ph soil hydrology and ambient temperature which influence the preservation of skeletal tissues are assessed while the different diagenetic pathways such as microbial degradation loss of organics mineral changes and dna degradation are surveyed fluctuating water levels in and around the bone is the most harmful for preservation and lead to rapid skeletal destruction diagenetic mechanisms are found to work in conjunction with each other altering the biogenic composition of skeletal material this illustrates that researchers must examine multiple diagenetic pathways to fully understand the post mortem interactions of archaeological skeletal material and the burial environment

why do crystallinity values fail to predict the extent of diagenetic alteration of bone mineral spectroscopic indicators of bone crystallinity such as the infrared splitting factor irsf are commonly used to determine the general state of preservation of ancient bone in principle such indices might be expected to act as a proxy for alteration of bone mineral and thus could be used to screen bones or portions of bones for likely preservation of in vivo biogenic trace element and stable isotope signals we tested the relationship between irsf and bone mineral composition in two suites of well characterised recent and pleistocene bones initially crystallinity change and trace element uptake are correlated apparently both controlled by decomposition of the organic phase and exposure of bone crystal surfaces this relationship breaks down in older bones where authigenic phosphate growth and mineral pore water interactions are no longer rate limited by the breakdown of collagen and exposure of crystal surfaces in these conditions the extent of chemical alteration of bone will be controlled by site specific conditions and thus while ftir spectra of bone provide a broad indication of organic content and apatite recrystallisation they are not reliable proxies for the degree of diagenetic alteration in terms of biogenic geochemical signals

bone diagenesis in arid environments an intra skeletal approach bone trace element content and isotopic composition are closely related to human nutrition the investigation of archaeological bone geochemistry can help us to better understand the relationship between past populations and their environment alongside cultural practices as inferred from dietary reconstruction however dietary in formation may be altered post mortem by diagenetic processes in soil in this study bone mineralogy ca p sec ondary minerals organic matter content and bone apatite crystallinity histology element content mg na f sr ba mn fe la ce and u and stable isotope composition 13cand 18o carbonate were investigated at the intra individual scale in order to understand the effects of diagenesis on skeletons buried in different saharo sahelian environments between 10 to 18 bone samples were taken from 4 neolithic skeletons excavated in the mauritanian dhar oualata and nema and in the daounas mali additionally the enamel of two third molar teeth was also analysed from each skeleton for comparison with bone the results show that the four skeletons buried in the same desert climate area all exhibited different degrees of diageneticmodification relatedto localtaphonomic conditions highly drainedand periodically flooded environments generated substantial bone bacterial damage low to moderate apatite crystallinity and secondary minerals in bone pores bone trace element content and isotopic composition were more diagenetically affected than in bones from skeletons buried in a drier environment which display little bioerosion high apatite crystallinity and the absence or late precipitation of secondary minerals in their bone pores intra skeletal variability of the geochemical composition and the comparison of geochemical data from bones and teeth enables the approximation of ante mortem bone trace element and stable isotope compositions using the best preserved bones from each skeleton

states of preservation of bones from prehistoric sites in the near east a survey abstract a survey of the states of preservation of organic material in 30 fossil bones from 16 different prehistoric sites in the near east shows that whereas almost all the bones have little or no collagen preserved they do with few exceptions contain non collagenous proteins these macromolecules therefore represent an important reservoir of indigenous fossil bone constituents

bone diagenesis at the micro scale bone alteration patterns during multiple burial phases at al khiday khartoum sudan between the early holocene and the ii century ad abstract histological analysis is widely applied to archaeological and fossil bones in order to identify diagenetic changes in bone microstructure diagenetic processes affecting bones from the body deposition to the discovery strongly depend on environmental conditions therefore the study of diagenetic alterations provides valuable information on the taphonomic history of bones and on their burial environment histological analysis was performed on 58 samples of human compact bone found at al khiday khartoum sudan a multi stratified archaeological site that revealed a cemetery with distinct burial phases dating from the early holocene to the ii century ad the well defined archaeological context provides a set of bone samples belonging to the same site but buried in different phases and under different environmental conditions central sudan was characterised by a humid environment with seasonal swamps and palaeo lakes in the early holocene while in the ii century ad the environmental conditions were more similar to the current arid climate of the sub saharan belt scanning electron microscopy sem and high resolution x ray computed micro tomography ct analysis revealed extensive bacterial and fungal attack and secondary phases precipitation and dissolution in the samples the analysis of textural relationships between each diagenetic feature enabled to establish a relative chronological sequence of events acting during burial moreover different patterns of diagenetic alterations were observed for burial phases of different ages proving a strong relationship between diagenesis and environmental conditions

mineralogical and compositional changes in bones exposed on soil surfaces in amboseli national park kenya diagenetic mechanisms and the role of sediment pore fluids abstract bones exposed on tropical savannah grasslands of amboseli national park kenya undergo extensive post mortem alteration within 40 years a combined analytical approach involving tem microscopy trace metal analysis ftir spectroscopy and petrographic analysis has revealed a complex dynamic diagenetic environment operating within exposed bones driven by evaporative transport of soil water from the bone soil interface to the upper exposed surface of the bone this process results in extensive bone soil water interaction and is responsible for increases in the concentrations of trace elements such as ba and la of 100 1000 within 15 years the maximum and mean size of bone crystallites increases with continued exposure this change in mean crystallite length is correlated positively with increases in bone crystallinity which in turn is associated with degradation of the bone protein microbial decomposition is rarely observed in the amboseli bones but where present resulted in severe dissolution reprecipitation of bone mineral many bones showed extensive permineralization of the larger vascular spaces with calcite and barite and to a lesser extent crandallite permineralization of unburied bones may account for 95 reduction in macro micron millimeter scale porosity in the bone within 2 years of death we produce a model for pre burial diagenesis of bone in arid tropical environments that highlights extensive alteration of bone chemistry within 1 40 years post mortem

grain size distribution in the mantle wedge of subduction zones 1 mineral grain size plays an important role in controlling many processes in the mantle wedge of subduction zones including mantle flow and fluid migration to investigate the grain size distribution in the mantle wedge we coupled a two dimensional 2 d steady state finite element thermal and mantle flow model with a laboratory derived grain size evolution model in our coupled model the mantle wedge has a composite olivine rheology that incorporates grain size dependent diffusion creep and grain size independent dislocation creep our results show that all subduction settings lead to a characteristic grain size distribution in which grain size increases from 10 to 100 m at the most trenchward part of the creeping region to a few centimeters in the subarc mantle despite the large variation in grain size its effect on the mantle rheology and flow is very small as 90 of the deformation in the flowing part of the creeping region is accommodated by grain size independent dislocation creep the predicted grain size distribution leads to a downdip increase in permeability by 5 orders of magnitude this increase is likely to promote greater upward migration of aqueous fluids and melts where the slab reaches 100 km depth compared with shallower depths potentially providing an explanation for the relatively uniform subarc slab depth seismic attenuation derived from the predicted grain size distribution and thermal field is consistent with the observed seismic structure in the mantle wedge at many subduction zones without requiring a significant contribution by the presence of melt

diagenesis of strontium in fossil bone a reconsideration of nelsonet al 1986 abstract in experiments on marine animal fossils that had been buried in terrestrial sediments nelsonet al 1986 geochimica et cosmochimica acta50 1941 1949 reported that the strontium sr of prehistoric bone had nearly completely exchanged with that of the burial environment and therefore cannot be used for paleodietary reconstruction however sealyet al 1991 journal of archaeological science18 399 416 using a solubility profile procedure reported that it was possible to remove diagenetic sr and obtain biologically meaningful sr nevertheless the nelsonet al study is often cited as evidence that a biological signal is irretrievable here infra red spectrometry xrd spectrometry and elemental analyses were used to compare the effects of the nelsonet al protocol with the solubility profile protocol on the crystal structure and crystallinity of the bone and fossil specimens the results show that the procedures used by nelsonet al which include a preliminary ashing step result in severe recrystallization of apatite both before and during the leaching step which deleteriously affects any attempt to recover biological sr by contrast no observable recrystallization takes place in the solubility profile procedure the results imply that the conclusions reached by nelsonet al are primarily artefacts of the specific methods used in their study rather than due to any inherent mechanism of diagenesis

strontium increases and crystallinity changes in taphonomic and archaeological bone bone strontium levels and hydroxyapatite crystal sizes increased with time in two exposed wildebeest skeletons the strontium increases could not be removed by sequential washing according to the method of sillen a 1986 biogenic and diagenetic srca in plio pleistocene fossils of the omo shungura formation paleobiology12 311 323 human subfossil bone recovered archaeologically also showed evidence of extensive diagenetic reworking that resulted in crystal growth and elevated strontium levels the increase in bone strontium content was independent of nonapatitic contaminating crystal phases

grain size sensitive seismic wave attenuation in polycrystalline olivine 1 in order to investigate the processes responsible for the attenuation of seismic shear waves in the earth s upper mantle four olivine polycrystals ranging in mean grain size d from 3 to 23 m have been fabricated characterized and mechanically tested in torsion at high temperatures and seismic frequencies both the shear modulus which governs the shear wave speed vs and the dissipation of shear strain energy q 1 have been measured as functions of oscillation period to temperature t and for the first time grain size at sufficiently high t all four specimens display similar absorption band viscoelastic behavior adequately represented for 1000 t 1200 or 1300 c and 1 to 100 s by the expression q 1 a tod 1 exp e rt with a 7 5 102 s m 0 26 and e 424 kj mol 1 this mildly grain size sensitive viscoelastic behavior of melt free polycrystalline olivine is attributed to a combination of elastically and diffusionally accommodated grain boundary sliding the latter becoming progressively more important with increasing t and or to extrapolation to the larger mm cm grain sizes expected in the earth s upper mantle yields levels of dissipation comparable with those observed seismologically implying that the same grain size sensitive processes might be responsible for much of the observed seismic wave attenuation the temperature sensitivity of vs is increased substantially by the viscoelastic relaxation allowing the lateral variability of wave speeds to be associated with relatively small temperature perturbations

microbial attack of archaeological bones versus high concentrations of heavy metals in the burial environment a case study of animal bones from a mediaeval copper workshop in paris abstract microbial attack is one of the key processes altering archaeological bone during the early stage of diagenesis some burial conditions seem more prone to prevent microbial attack in archaeological bone it is generally admitted that the presence of certain metals in the burial environment such as copper may have an inhibiting effect on microbial destruction of archaeological bone this study was aimed at evidencing such effects by the investigation of different archaeological animal bones excavated from several activity zones of one french archaeological urban site corresponding to a mediaeval copper alloys workshop in paris at hotel de mongelas the analytical approach combined morphological observations sem structural investigations ft ir xrd and tem and chemical analyses sem edx and pixe pige of archaeological bones at different scales down to the nanoscale it permitted the classification of the bones as a function of their contamination with heavy metals their conservation state and the presence of signs of microbial attack correlations between the observed alteration features and the metallurgical activity on this site as well as the underlying alteration processes are discussed an inhibiting effect of heavy metals on the microbial attack could be deduced from the available though restricted data in agreement with the expectation however the relationship between heavy metal uptake and microbial alteration of bone depends on other diagenetic factors and their progress such as bone collagen content crystallinity of bone mineral soil geochemistry and hydrology significant changes in environmental conditions over time which can especially occur in urban sites can also influence alteration phenomena generally simultaneous alterations induced by heavy metal uptake and microbial attack seem to take place in the very early stage of diagenesis and influence one another in sites with soils highly contaminated in heavy metals