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

high resolution sr ca records in sclerosponges calibrated to temperature in situ ratios of strontium to calcium have been analyzed by laser ablation inductively coupled plasma mass spectrometry la icp ms in a skeletal section of the sclerosponge ceratoporella nichol soni the growth period representative of 3 yr was stained in the skeleton with a fluorochrome calcein temperatures were record ed at 2 h intervals within the shallow cryptic reef enclosure that the sclerosponge inhabited on the northern coast of jamaica al lowing the formulation of a direct empirical relationship between sr ca and temperature to verify this calibration sr ca ratios of two sclerosponges of the same species from depths of 67 m and 136 m in exuma sound bahamas were analyzed by la icp ms and compared to the temperatures from these depths over a decade prior to collection the result is an independently verified high resolution empirical calibration for the temperature sensitivity of sr ca ratios in the aragonite skeletons of sclerosponges from ja maica and the bahamas the calibration is a first for c nicholsoni and indicates that sclerosponges are more sensitive temperature recorders than zooxanthellate corals it represents an important step in establishing skeletal geochemistry of sclerosponges as a proxy of temperature in the upper 250 m of the ocean

iron copper and zinc isotopic fractionation up mammal trophic chains abstract there is a growing body of evidence that some non traditional elements exhibit stable isotope compositions that are distinct in botanical and animal products providing potential new tracers for diet reconstructions here we present data for iron fe copper cu and zinc zn stable isotope compositions in plants and bones of herbivores and carnivores the samples come from trophic chains located in the western cape area and in the kruger national park in south africa the fe cu and zn isotope systematics are similar in both parks however local cu and possibly zn isotopic values of soils influence that of plants and of higher trophic levels between plants and bones of herbivores the zn isotope compositions are 66zn enriched by about 0 8 whereas no significant trophic enrichment is observed for fe and cu between bones of herbivores and bones of carnivores the fe isotope compositions are 56fe depleted by about 0 6 the cu isotope compositions are 65cu enriched by about 1 0 and the zn isotope compositions are slightly 66zn depleted by about 0 2 the isotopic distributions of the metals in the body partly explain the observed trophic isotopic systematics however it is also necessary to invoke differential intestinal metal absorption between herbivores and carnivores to account for the observed results further studies are necessary to fully understand how the fe cu and zn isotope values are regulated within the ecosystem s trophic levels but the data already suggests significant potential as new paleodietary and paleoecological proxies

sr ca u ca and δ18o records in recent massive corals from bermuda relationships with sea surface temperature abstract high resolution records of sr ca u ca ratios and 18o have been obtained in two recent colonies of massive corals diploria labyrinthiformis from bermuda the three geochemical proxies display regular seasonal variations and are well correlated with each other however some important discrepancies are observed between the two colonies the average seasonal variations of the three geochemical proxies are lower by almost 50 in one of the profiles where the seasonal oscillation also displays a strong asymmetry with narrower summer maxima different calculations are discussed for calibrating sr ca and 18o with sea surface temperatures sst we show that the method using only temperature minima and maxima is slightly more accurate and is also more reliable our results from bermuda corals confirm that the temperature dependency of sr ca u ca and 18o is species dependent as previously shown by others and that vital effects are clearly involved in the geochemical incorporation of trace elements in the coral skeleton finally a simple model involving seasonal variation of the growth rate and a kinetic fractionation related to growth rate is presented to explain the differences between the two bermuda colonies it is shown that these factors may prevent corals from recording the complete temperature seasonality and could be the cause for the discrepancies observed between profiles resulting in significant biases of the sst reconstructions

u series dating of fossil teeth and carbonates from snake cave thailand abstract snake cave thailand is an important site for the study of the evolution in southeast asia leading to a discovery of rich and various faunas including a human tooth fossils of large and small mammals converge to indicate on the basis of faunal assemblage a late middle pleistocene age for the fossiliferous layers on the other hand previous u series dating of carbonates furnished a lower limit for the fossils of about 130 ky in order to achieve a better comprehension of the chronology of the cave the uranium series method for absolute age determination has been applied to some carbonates older than those studied previously and to fossils themselves we used the isochron technique approach to yield valuable ages because spleleothem samples consist in a mixture of calcite and detrital contamination the results obtained suggest that the main fossiliferous level is older than about 160 ky the application of the u series method to tooth samples from this tropical cave leads to erroneous ages probably because of post depositional groundwater movements

models of diffusion limited uptake of trace elements in fossils and rates of fossilization abstract many fossils are assumed to take up trace elements by a process of combined diffusion plus adsorption da yet in principle composition profiles can be explained by several different diffusion limited processes including diffusion plus reaction or recrystallization dr and double medium diffusion dmd the da and dmd models are supported by ree and u composition profiles across fossil teeth measured by laser ablation icp ms that show error function like diffusion profiles into enamel from the dentine enamel interface and concentrations in the interior of enamel that are at original biogenic levels or higher published composition and age profiles in some pleistocene bones may be better explained by a dr model all three diffusion models imply linear behavior between age and distance squared vastly simplifying u series dating methods for pleistocene fossils modeled uptake rates for fossil teeth yield a strict minimum bound on durations of about one decade to one century the similarity of diffusion profiles in teeth irrespective of depositional ages ranging from 30 ka to 30 ma implies that uptake occurred quickly with a maximum duration of a few tens of kyr for typical fossil enamel faster uptake is implied for typical fossil bone and dentine disparities in these uptake estimates compared to some archeological bone may reflect sampling and preservation bias for paleontological vs archeological materials

rare earth element geochemistry of colour lake an acidic freshwater lake on axel heiberg island northwest territories canada a lake column profile was collected in 24 m of water from colour lake axel heiberg island northwest territories canada in early june of 1991 beneath 1 8 m of lake ice the rare earth element ree concentrations of the acidic fresh waters of colour lake were analyzed along with the major solute chemistry in order to investigate ree distribution and speciation in the low ph waters previous studies indicate the lake is dominated by ca2 mg2 and so42 and has no measurable carbonate alkalinity shale normalized ree patterns for the lake waters are all enriched in the middle ree s mree s as compared to the light ree s lree s and heavy ree s hree s dissolved ree concentrations in colour lake e g 2 3 22 nmol kg 1 for nd mean value of 20 nmol kg 1 are typically less than values obtained for the acid saline waters of the lake tyrrell playa system in australia as well as the slightly acidic groundwaters of the carnmenellis region of england but greater than ree concentrations measured in the alkaline saline waters of mono lake california u s a the speciation of the ree s in colour lake was modelled based on the major solute chemistry using a combined specific ion interaction and ion pairing model these calculations suggest that in the relatively high sulfate low ph waters of colour lake the ree s exist as either free metal so42 or f complexes our calculations indicate that so42 complexes dominate over the free metal and fluoride species for the majority of the ree s in the lake water and that in general for acidic high sulfate waters sulfate complexes with the ree s may increase the dissolved concentrations of the ree s over natural waters where relatively low sulfate concentrations prevail

enamel diagenesis at south african australopith sites implications for paleoecological reconstruction with trace elements abstract elemental ratio data from archaeological and paleontological bone have often been used for paleoecological reconstruction but recent studies have shown that even when solubility profiling techniques are employed in an attempt to recover biogenic signals bone is an unreliable material as a result there has been renewed interest in using enamel for such studies as it is known to be less susceptible to diagenesis nevertheless enamel is not immune from diagenetic processes and several studies have suggested that paleoecologically relevant elements may be altered in fossil enamel here we investigate sr ba zn and pb compositions of enamel from south african karstic cave sites in an effort to ascertain whether or not this material provides reliable paleoecological information we compared enamel data for mammals from three fossil sites aged 1 8 3 0 ma all of which are on dolomites with data from modern mammals living on dolomitic and granitic substrates sr ca and ba ca are about three times higher in enamel from modern mammals on granites than those living on dolomites stressing the need for geologically appropriate modern fossil comparisons after pretreatment with dilute acid we found no evidence of increased sr ca ba ca or pb ca in fossil enamel in contrast zn ca increased by over five times at one site makapansgat but much more subtly elsewhere ecological patterning in sr ca ba ca and sr ba ratios was also retained in fossil enamel this study suggests that sr ca ba ca and pb ca data likely preserve paleoecological information from these sites but also demonstrates that geologically similar sites can differ in the degree to which they impart certain elements zn in this case to fossils thus screening is probably necessary on a site by site basis lastly further investigation of elemental distributions in modern foodwebs is necessary before elemental ratio analysis can become a common tool for paleoecological reconstruction

lu hf and pbsl geochronology of apatites from proterozoic terranes a first look at lu hf isotopic closure in metamorphic apatite abstract the mineral apatite is characterized by elevated and highly variable lu hf ratios that in some cases allow for single crystal dating by the lu hf isotopic system apatites from the adirondack lowlands and otter lake area in the grenville province and from the black hills south dakota yield lu hf ages that are consistently older than their respective pb step leaching ages isotopic closure for the lu hf system therefore occurs before u pb system closure in this mineral in the adirondack lowlands where h2o activity was low lu hf systematics of cm sized apatite crystals remained undisturbed during upper amphibolite facies metamorphism 700 to 675 c at 1170 1130 ma the relatively old lu hf ages of 1270 and 1230 ma observed for these apatites correlate with decreasing crystal size in contrast apatite from the fluid rich otter lake area and black hills yields unrealistically low apparent lu hf closure temperatures implying that in these apatites fluids facilitated late exchange the lu hf ages for the metamorphic apatites were thus controlled either by the prevailing temperature and grain size or by fluid activity

on long wave propagation over a fluid mud seabed using the boussinesq approximation a set of depth integrated wave equations for long wave propagation over a mud bed is derived the wave motions above the mud bed are assumed to be irrotational and the mud bed is modelled as a highly viscous fluid the pressure and velocity are required to be continuous across the water mud interface the resulting governing equations are differential integral equations in terms of the depth integrated horizontal velocity and the free surface displacement the effects of the mud bed appear in the continuity equation in the form of a time integral of weighted divergence of the depth averaged velocity damping rates for periodic waves and solitary waves are calculated for the solitary wave case the velocity profiles in the water column and the mud bed at different phases are discussed the effects of the viscous boundary layer above the mud water interface are also examined

reconstructing seawater sr ca during the last 70 my using fossil fish tooth enamel abstract the chemical composition of past oceans records the combined effects of the evolution of life climate changes and solid earth dynamics variations in the rate of hydrothermal alteration of the oceanic crust continental weathering input and burial of marine carbonates are thought to drive the seawater sr ca ratio several methods exist for reconstructing past seawater sr ca ratio which are based on the partitioning of sr between biogenic and inorganic carbonates and seawater a compilation of reconstructed seawater sr ca ratios shows that results at variance with each other are obtained for the last 100 my leaving the question of the sr ca composition of seawater over this period unresolved here a new method for reconstructing the sr ca ratio of past seawater based on the partitioning of sr between tooth apatite of fossil fish enamel and seawater is proposed previously reported values of sr ca and 18 o po4 for a collection of fish teeth and new data allow the reconstruction of the seawater sr ca ratio evolution for the last 70 my using a new thermometer based on the sr ca ratio in fish teeth calculated sr ca ratios decrease from 14 mmol mol 1 at 70 ma to 8 mmol mol 1 at 50 ma and further increase to present day values during the pliocene the results are in agreement with values calculated from cenozoic benthic foraminifera obtained from odp and dsdp sites once the biological offsets of the partitioning of sr between apatite and water are determined fossil fish tooth bioapatite represents a material of choice for reconstructing the past seawater sr ca considering its better resistance to diagenetic alteration than for calcite and aragonite

an investigation of barium calcium and strontium as palaeodietary indicators in the southwestern cape south africa samples of modern indigenous foods and archaeological human skeletons from the southwestern cape of south africa were analyzed for barium strontium and calcium barium strontium and barium calcium successfully differentiate marine and terrestrial foods measurement of all three elements improves the resolution of the marine terrestrial separation and enhances the trophic level differentiation analysis of the archaeological human skeletons indicates that removal of diagenetic contamination is critical in order to obtain useful elemental analyses where such removal is possible barium strontium and barium calcium techniques can be particularly valuable in distinguishing marine and terrestrial inputs into prehistoric human diets in areas where stable carbon analyses are not applicable e g in regions with terrestrial c 4 flora

the assessment of ree patterns and 143nd 144nd ratios in fish remains abstract the ree content and isotopic composition of sr and nd have been determined in fish teeth ranging in age from the trias to the present and from various localities mostly around the atlantic these measurements have been carried out on selachian and teleost remains from the same locality in togo and show no appreciable difference which suggests with the help of a mass balance calculation of the ce anomaly that diagenetic effects are not responsible for the ree enrichment of biogenic phosphates one group of fossil teeth has about 3 times the ree abundances of shale and a shale normalized pattern with a minimum at sm it is thought to reflect deposition in the open sea environment a second group has ree concentration about 10 times higher than the first group with either a regular light ree enrichment or more frequently a maximum in the middle ree both being probably indicative of deposition in estuarine or near shore conditions the shape of the ree spectra and the size of the ce anomaly can be used semi quantitatively to determine the depth of deposition the results presented here on late cretaceous eocene fish teeth samples from morocco reflect an increasing influx of deep waters with a lowla yb ratio and strong negative ce anomaly which agrees well with the evolution of sediment chemistry and microfauna associations in contrast nd is typical of the water mass in which the fish debris decayed examples of nearly isolated basins identified with nd isotopes include the south atlantic prior to the lutetian nd 13 5 the miocene persian gulf nd 3 1 and bolivia during the late cretaceous nd 12 8 togo and guinea bissau results suggest that in the south atlantic the meridional oceanic circulation had not started before 45 ma ago combination of ree and nd data suggests that the assignment of jurassic cretaceous samples measured so far to open sea water masses is still ambiguous

heterogeneous rare earth element ree patterns and concentrations in a fossil bone implications for the use of ree in vertebrate taphonomy and fossilization history abstract a bone fragment cgdq 3 of falcarius utahensis a therizinosaur from the early cretaceous cedar mountain formation utah contained within a carbonate nodule was analyzed by laser ablation inductively coupled plasma mass spectrometry la icp ms in order to investigate ree variability within a thin walled phalanx previous studies have found depth related ree pattern variations however in cgdq 3 variation occurs along the circumference of the bone nasc normalized ree patterns and concentrations vary between two apparent end members a light ree enriched lree pattern similar to solution icp ms analysis of this bone characterizes approximately two thirds of the bone fragment total ree concentrations are high and do not vary significantly from the periosteal surface to the medullar surface conversely the remaining one third of the bone has ree patterns that are mree depleted and low in total ree concentrations ree concentrations in this part of the bone do not vary significantly from the periosteal to the medullar surface a positive ce anomaly is found throughout the entire bone and is greatest within the lree enriched portion of the bone this in combination with the lree enrichment suggests that the bone fossilized under reducing conditions the distance between the lree enriched and mree depleted regions is less than 1 mm isotopic and petrographic analyses of the bone and surrounding carbonate matrix suggest the ree patterns in the bone were the result of partial fossilization incomplete filling of micro pore spaces around bone crystallites in an environment with changing redox conditions the lower mree depleted part of the bone fossilized contemporaneously with a pendant cement that formed on the underside of the bone in the vadose zone formation of the pendant cement restricted water flow through the bone isolating the lower portion which incorporated a mree depleted pattern the upper part of the bone lree enriched side fossilized under more reducing conditions than the lower part this resulted in reductive dissolution of minerals such as hydrous ferric oxides and manganese oxides which were lree enriched with positive ce anomalies these ree were then incorporated into the upper part of the bone this likely occurred after the bone entered the saturated zone below the water table the thinness of the bone and presence of a pendant cement helped facilitate partial fossilization of the bone preserving the ree signature of an earlier fluid as demonstrated by this case study differences in ree patterns within a fossil may record changes in geochemical conditions during fossilization particularly when bones are encased in a material that reduces fluid permeability such as micritic vadose calcite analysis of such bones may offer the opportunity to decipher complex fluid histories that occur during fossilization la icp ms should be utilized to confirm solution icp ms analysis if it yields high ree variability prior to an interpretation of reworking or time averaging

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

climate proxies from sr ca of coccolith calcite calibrations from continuous culture of emiliania huxleyi abstract continuous culture of the coccolithophorid emiliania huxleyi reveals that coccolith sr ca ratios depend on temperature and growth rate at a constant temperature of 18 c coccolith sr ca ratios increased nearly 15 as growth rate increased from 0 1 to 1 5 divisions per day and calcification rate increased from 1 5 to 50 pg calcite per cell per day when temperature increased from 7 to 26 c sr ca ratios increased by more than 25 i e 1 1 c although the range in growth and calcification rates was the same as for experiments at constant temperature the temperature dependence of sr ca ratios in coccoliths is consistent with that observed in planktonic foraminifera and abiogenic calcites suggesting that it is controlled by thermodynamic processes however the positive correlation of coccolith sr ca with temperature contrasts with field studies in the equatorial pacific where sr ca ratios are highest at the locus of maximum upwelling and productivity despite depressed temperatures this paradox may reflect different calcification rate effects between e huxleyi and the other species dominating assemblages in the equatorial pacific sediments which may be resolved by new techniques for separation of monospecific coccolith samples from sediments models of crystal growth indicate that kinetic effects on sr partitioning in calcite due to surface enrichment could explain the sr ca variations observed in constant temperature experiments but not the larger amplitude calcification rate effects observed in equatorial pacific sediments despite the dual influence of temperature and growth rate on coccolith sr ca coccolith sr ca correlates with b the slope of the dependence of carbon isotope fractionation in biomarkers ep on co2 aq at a range of growth rates and temperatures consequently using coccolith sr ca in combination with alkenone ep may improve paleo co2 determinations

further studies for uranium series dating of fossil bone abstract in an earlier paper the authors suggested that bones from well sealed depositional matrices might be deteable by the u series method this paper presents the results of further case studies on bones from archaeological sites and also in vitro laboratory studies of the u bone system these suggest that the u series method may only be of limited use for bones and that in most sites samples are exposed to an unknown number of wetting events over their period of deposition the laboratory experiments indicate a more complex process than the simple diffusion of u through the bone cross section

trace elements and their isotopes in bones and teeth diet environments diagenesis and dating of archeological and paleontological samples fossil biogenic apatites display trace element te compositions that can record environmental and biological signals give insights into past water compositions or be used for dating paleontological and archeological bones and teeth processes of te incorporation into apatites of skeletal phosphatic tissues are described ranging from those active in living organisms to those active during diagenesis abiotic incorporation mechanisms have been modeled theoretically and experimentally and include crystallographic controls on te partitioning coefficients inorganic surface adsorption and adsorption mediated through chelation and diffusion adsorption processes each leading to specific fractionation patterns predictions from models and experiments have been tested against te concentration and isotopic composition data on remains of contemporary wild or raised animals and on fossils of various ages and environments in living organisms tes incorporated in apatite are separated in two categories non essential elements whose concentration is compared to that of an essential element with similar behavior e g sr ca to reconstruct trophic chains and essential elements whose isotopic ratios are used to trace metabolic activity diet etc in fossils elements are incorporated during diagenesis such as rare earth elements rees and trace diagenetic processes ranging from very early quantitative adsorption likely mediated by chelators protracted diagenesis through inorganic adsorption and fractionation through diffusion adsorption to low grade metamorphism associated with intense redistribution under crystal chemical control these different steps are also identified as steps of radionuclide incorporation only samples where the earliest steps can be deciphered are useful for determining stratigraphic and archeological ages other samples will date late diagenetic events that have obliterated the paleoenvironmental signals but may be of geological significance e g tectonic events

cenozoic seawater sr ca evolution records of seawater chemistry help constrain temporal variations in geochemical processes that impact the global carbon cycle and climate through earth s history here we reconstruct cenozoic seawater sr ca sr casw using fossil conus and turritellid gastropod sr ca combined with an oxygen isotope paleotem perature record from the same samples the gastropod record suggests that sr casw was slightly higher in the eocene 11 4 3 mmol mol than today 8 54 mmol mol and remained relatively stable from the mid to late cenozoic we compare our gastropod cenozoic sr casw record with a published turritellid gas tropod sr casw record and other published biogenic benthic foraminifera fossil fish teeth and inorganic pre cipitate calcite veins sr casw records once the uncertainties with our gastropod derived sr casw are taken into account the sr casw record agrees reasonably well with biogenic sr casw records assuming a seawater ca history derived from marine evaporite inclusions all biogenic based sr casw reconstructions imply decreasing seawater sr through the cenozoic whereas the calcite vein sr casw reconstruction implies increasing sr through the cenozoic we apply a simple geochemical model to examine the implications of divergence among these seawater sr reconstructions and suggest that the interpretation and uncertainties associated with the gastropod and calcite vein proxies need to be revisited used in conjunction with records of carbonate depositional fluxes our favored seawater sr ca scenarios point to a significant increase in the proportion of aragonite versus calcite deposition in shelf sediments from the middle miocene coincident with the proliferation of coral reefs we propose that this occurred at least 10 million years after the seawater mg ca threshold was passed and was instead aided by declining levels of atmospheric carbon dioxide

calcium isotopes in archaeological bones and their relationship to dairy consumption abstract the calcium isotope ratios 44 42 ca of bones from humans and fauna from three archaeological sites taforalt abu hureyra and danebury are evaluated in order to assess whether calcium isotope ratios of bones can be used to detect dairy consumption by adult humans at each site the fauna 44 42 ca is the same regardless of species while the humans have lower 44 42 ca than the local animals by 0 24 0 41 site means however we cannot ascribe this difference to dairy consumption given this human faunal difference also occurs in epipalaeolithic and mesolithic adult humans where dairy consumption is unlikely rather this difference appears to be a result of differences in metabolic processes or other aspects of diet between humans and fauna minimal isotopic change in sequential acid leaches of bone powders and consideration of the high calcium concentration in bone suggest that bone calcium isotope ratios are not substantially affected by diagenetic change

rare earth element evolution of phanerozoic seawater recorded in biogenic apatites rare earth element ree contents of marine biogenic apatites have been shown to record seawater compositions a data base of available and newly acquired rare earth element ree contents of marine biogenic apatites has been created to assess the past seawater ree compositions to ensure that this data base contains only the pristine ree signals altered samples characterized by very low la sm n ratios where n stands for ree ratios normalized to the nasc composition gromet et al 1984 geochim cosmochim acta 48 1984 2469 acquired during apatite recrystallization are not included in the database these data reveal a change in the tethyan seawater composition between 110 and 80 ma after the end of the cretaceous the ree chemistry of seawater remains constant until present day this seawater composition change is likely due to concurrent changes in ree scavenging processes a strong correlation between decreasing sm yb n ratios and increasing ce anomalies for samples deposited during the 80 110 ma period is observed as ce anomalies are attributed to ocean water redox conditions changes in ree scavenging could reflect an evolution from stratified and poorly oxygenated waters towards well mixed and oxygenated waters this could have resulted from changing current patterns stemming from the contemporaneous opening of the atlantic ocean a major change in middle and late cretaceous oceanic circulation linked to plate tectonics would have favored the colonization of pelagic environments

water waves over a muddy bed a two layer stokes boundary layer model this study aims to develop an asymptotic theory for the flow kinematics of a thin layer of viscous mud under water surface waves the mud depth the mud stokes boundary layer thickness and the wave amplitude are assumed to be comparable with one another and much smaller than the wavelength by virtue of this sharp contrast in length scales boundary layer equations are used to describe motion of both the mud and the immediately overlying water analytical solutions are sought and explicit expressions are obtained under progressive waves for the fluid velocity fields interface wave characteristics and wave damping rate at the first order and the steady mean discharge rate and mass transport velocity of mud at the second order effects of the mud layer thickness density and viscosity ratios on these kinematic quantities are examined in detail

protracted diagenetic alteration of ree contents in fossil bioapatites direct evidence from lu hf isotope systematics abstract fossil bones and teeth are potentially important repository for geochemical proxy data and a target for radiometric dating the concentration of many trace elements in bones and teeth increases by orders of magnitude after death and it is this diagenetic incorporation that forms the basis for several areas of geochemical study the use of bones and teeth in this context relies on two assumptions first that target metal ions are incorporated rapidly after death reflecting a known environmental signal and second that after early incorporation the bone or tooth remains as an essentially closed system resistant to later diagenetic change a wide literature has developed exploring these assumptions but relatively little direct evidence has been used to assess the long term diagenetic stability of trace elements within bones and teeth in this study we use the lu hf isotope system to show that bones and teeth of cretaceous and triassic age from both terrestrial and marine settings experience continued long term diagenetic change most likely through gradual addition of trace elements modelling suggests that diagenetic addition after initial recrystallisation may account for 50 of the total ree content in the sampled bones the extent depending on initial uptake conditions tooth enamel and enameloid may be more resistant to late diagenetic changes but dentine is probably altered to the same extent as bone these results have significant implications for the use of bones and teeth as hosts of chronological palaeoceanographic palaeoenvironmental and taphonomic information particularly in mesozoic and palaeozoic contexts

patterns of chemical change during bone fossilization the uptake of elements by bone during fossilization is a well recognized phenomenon but the nature of and the factors leading to chemical heterogeneity in fossil bone are only just starting to be elucidated indeed in the recent past the assumption that fossil bone is chemically homogeneous has been commonly used in several investigations including those of bone dating and dietary studies in an attempt to understand the processes of element uptake we have investigated some chemical heterogeneities in a fossil bone and have assessed the potential use of bone composition as an indicator of the trace element contents of associated groundwater our study extends other work1 2 by giving the first analysis of rare earth element ree distribution in a fossil bone and by showing that information on the redox state and ree abundance pattern of the groundwater can be obtained the results contribute to the interpretation of bone analyses in studies on provenance and age determination as well as in the diet and health of past populations

dissolved rare earth elements in the southern ocean cerium oxidation and the influence of hydrography abstract analysis of dissolved ree distributions in the southeastern atlantic ocean has revealed that progressive oxidative removal of dissolved ce from deepwater 1 km occurs over the mixing time of the oceans ce anomaly ce ce values measured in deep waters from the southeastern atlantic are similar to but slightly higher than those from deep ocean stations throughout the indian and pacific oceans typically falling in the range 0 08ce ce 0 12 only deepwater samples from the north atlantic exhibit values greater than ce ce 0 12 with the exception of southeastern atlantic bottomwaters which are influenced by antarctic bottomwater covariation of dissolved ree concentrations with salinity and or dissolved si concentrations at this site has allowed dissolved ree compositions for various southern ocean water masses to be predicted end member concentrations for antarctic bottom water aabw derived in this way indicate high dissolved ree concentrations similar to average pacific deep water but with significantly enhanced dissolved ce concentrations and less pronounced hree enrichment this result is consistent with the proximity of our study site to active aabw deepwater formation and evolution of that water mass during transport to the pacific ocean

phosphate lu hf geochronology abstract igneous metamorphic and biogenic apatite contains lu and hf in proportions that make this mineral suitable for dating by the 176lu 176hf method we present a new method for separation of lu and hf from apatite that involves a single extraction column step for hf and a second exchange column step for lu this procedure allows rapid sample processing prior to analysis by mc icp ms results from the igneous gardiner skaergaard and khibina intrusions indicate that the closure temperature for the lu hf isotopic system in apatite is relatively high the lu hf isochron age of 60 ma for the skaergaard intrusion east greenland is older than the generally accepted emplacement age but does not appear to be a product of mixing a centimeter sized apatite from the otter lake area grenvillian province yields high and variable 176lu 177hf ratios showing that metamorphic apatite may in some cases allow for mono mineral dating the most important application of the method is undoubtedly its potential use for dating sedimentary formations although we find biogenic apatite in porous matrix highly susceptible to post depositional resetting of the lu hf isotopic system the preservation of a near depositional age for a shark tooth from the impermeable london clay and recent work on crystalline authigenic phosphorites earth planet sci lett 201 2002 203 show the lu hf system to be a promising tool for direct dating of sedimentary formations

partition coefficients of hf zr and ree between zircon apatite and liquid concentration ratios of hf zr and ree between zircon apatite and liquid were determined for three igneous compositions two andesites and a diorite the concentration ratios of these elements between zircon and corresponding liquid can approximate the partition coefficient although the concentration ratios between apatite and andesite groundmass can be considered as partition coefficients those for the apatite in the diorite may deviate from the partition coefficients the hree partition coefficients between zircon and liquid are very large 100 for er to 500 for lu and the hf partition coefficient is even larger the ree partition coefficients between apatite and liquid are convex upward and large d 10 100 whereas the hf and zr partition coefficients are less than 1 the large differences between partition coefficients of lu and hf for zircon liquid and for apatite liquid are confirmed these partition coefficients are useful for petrogenetic models involving zircon and apatite

ion probe measurement of rare earth elements in biogenic phosphates abstract the rare earth element ree distributions in individual fish teeth and conodonts have been measured by ion probe concentrations and la yb ratios show little variations except in the enamel which suggests that ree uptake from the sedimented biogenic debris takes place at the water sediment interface as an essentially quantitative process without fractionation late diagenetic disturbances remained of marginal importance hence ree in phosphatic debris might reflect the input from the overlying water column

crystal chemical controls on rare earth element concentrations in fossil biogenic apatites and implications for paleoenvironmental reconstructions abstract fossil biogenic apatites display rare earth element ree patterns which have been proposed to reflect environmental and biological controls on past seawater composition these patterns can be separated in two groups 1 patterns that are similar to those of open ocean and epicontinental waters and 2 patterns that exhibit a strong enrichment in intermediate ree bell shaped patterns because ree trapping in biogenic apatites occurs mostly post mortem it is essential to understand the crystal chemical inorganic factors that can influence the fractionation of ree between apatite and water a model is proposed by which partition coefficients of ree between apatite and water for a substitution mechanism can be extrapolated from mineral melt partition data to seawater or sedimentary basin conditions these are compared with available experimental partition coefficients for ree adsorption mechanism and used to discuss ree patterns in fossil biogenic apatites calculations of ree patterns for apatites at equilibrium with water show that the bell shaped patterns in fossil apatites can be explained by fractionation with seawater or continental fluids at low temperature under crystal chemical control involving a substitution mechanism and in the context of extensive or late diagenesis in that case the equilibrium composition of the fluid cannot be unequivocally determined from observed ree concentrations in fossil apatites this type of sample is inappropriate to discuss the past environmental or biological controls on ree concentrations in the ocean other sample compositions suggest little to moderate alteration of the original oceanic to freshwater pattern through the adsorption mechanism in the context of weak or early diagenesis and may be used with caution for that purpose

coupled dynamics of interfacial waves and bed forms in fluid muds over erodible seabeds in oscillatory flows recent field investigations of the damping of ocean surface waves over fluid muds have revealed waves on the interface between the thin layer of fluid mud and the overlying much thicker column of clear water accompanied by bedforms on the erodible seabed beneath the fluid mud the frequencies and wavelengths of the observed interfacial waves are qualitatively consistent with the linear dispersion relationship for long interfacial waves but the forcing mechanism is not known to understand the forcing a linear model is proposed based on the layer averaged hydrostatic equations for the fluid mud together with the meyer peter mueller equation for the sediment transport within the underlying seabed both subject to oscillatory forcing by the surface waves if the underlying seabed is non erodible and flat the model indicates parametric instability to interfacial waves but the threshold for instability is not met by the observations if the underlying seabed is erodible the model indicates that perturbations to the seabed elevation in the presence of the oscillatory forcing create interfacial waves which in turn produce stresses within the fluid mud that force a net transport of sediment within the seabed toward the bedform crests thus causing growth of both bedforms and interfacial waves the frequencies wavelengths and growth rates are in qualitative agreement with the observations a competition between mixing created by the interfacial waves and gravitational settling might control the thickness density and viscosity of the fluid muds during periods of strong forcing this article is protected by copyright all rights reserved

nonlinear long waves over a muddy beach we analyse theoretically the interaction between water waves and a thin layer of fluid mud on a sloping seabed under the assumption of long waves in shallow water weakly nonlinear and dispersive effects in water are considered the fluid mud is modelled as a thin layer of viscoelastic continuum using the constitutive coefficients of mud samples from two field sites we examine the interaction of nonlinear waves and the mud motion the effects of attenuation on harmonic evolution of surface waves are compared for two types of mud with distinct rheological properties in general mud dissipation is found to damp out surface waves before they reach the shore as is known in past observations similar to the eulerian current in an oscillatory boundary layer in a newtonian fluid a mean displacement in mud is predicted which may lead to local rise of the sea bottom

a bingham plastic model for a muddy seabed under long waves the dynamics of cohesive mud under wave action is important to the geological processes along some coastlines because of the complex rheological properties there have been vastly different models for predicting the effect of mud on wave attenuation this paper focuses on a non newtonian behavior of highly concentrated mud whereby shearing strain occurs only if the shear stress exceeds a certain threshold called the yield stress the wave induced motion in a thin mud layer beneath a clear water layer is studied there are circumstances in which the yield stress is dominant and acts like a coulomb friction mud motion can change from continuous to intermittent as the wave attenuates the effects of the non newtonian behavior on wave damping are compared to other more common causes of dissipation

detailed mass spectrometric u series analyses of two teeth from the archaeological site of pech de l aze ii implications for uranium migration and dating abstract we report th u ages obtained by thermal ionization mass spectrometry of cross sections of two teeth from the archaeological site of pech de l aze ii the aim of this study is to reconstruct the pathways and time dependency of uranium uptake into different constituents of the two teeth a previous esr dating study of the two teeth yielded age estimates in the range of about 130 000 to 200 000 years which was in agreement with the geological assignment of riss for layers from which the specimens were recovered the closed system u series ages of all analyses range from 48 to 137 ka thus yielding age estimates which are between 30 and 90 ka too young the apparent closed system u series ages of the dentine and cement fractions at the top of the teeth are the oldest becoming gradually younger towards the interior of the two teeth the difference between apparent u series ages of dentine at the outer and inner parts of the two teeth is about 35 ka the enamel sections show the same patterns in u concentration and progression of apparent th u ages as the adjacent dentine samples but with generally younger ages our results indicate that uranium migrates both from the top and the base into the dentine of the teeth and from there into the adjacent enamel depending on the position of the sample significant uranium uptake appears to have taken place over many tens of thousands of years modelling the u uptake histories using a parametric model shows that for the cement and dentine components uptake is intermediate between linear uptake lu and early uptake eu closed system the enamel although often assumed to approximate more closely a closed system shows evidence of more recent u uptake these results also imply that it is not possible to use a simple single parameter u uptake model for all components of a given tooth either for u series or esr dating

wave mud interaction over the muddy atchafalaya subaqueous clinoform louisiana united states wave processes 1 observations of wave and sediment processes collected at two locations on the atchafalaya inner shelf show that wave dissipation in shallow muddy environments is strongly coupled to bed sediment reworking by waves during an energetic wave event 2 m significant wave height in 5 m water depth acoustic backscatter records suggest that sediment in the surficial bed layer evolves from consolidated mud through liquefaction fluid mud formation and hindered settling to gelled under consolidated mud net swell dissipation increases steadily during the storm from negligible prestorm values consistent with bed softening but shows no correlation with detectable fluid mud layers remarkably the maximum dissipation rate occurs poststorm when no fluid mud layers are present in the waning stage of the storm the contribution of different wave forcing processes to wave dissipation is analyzed using an inverse modeling approach based on a nonlinear three wave interaction model although wave mud interaction dominates dissipative processes nonlinear three wave interactions control the shape of the frequency distribution of the dissipation rate in the wake of the storm the viscosity values predicted by the inverse modeling converge toward measured values characteristic for gelled mud in a trend that is consistent with a fluid mud entering dewatering and consolidation stages

determination of sr and ba partition coefficients between apatite from fish sparus aurata and seawater the influence of temperature abstract the sr ca and ba ca ratios in inorganic apatite are strongly dependent on the temperature of the aqueous medium during precipitation if valid in biogenic apatite these thermometers would offer the advantage of being more resistant to diagenesis than those calibrated on biogenic calcite and aragonite we have reared seabreams sparus aurata in tanks with controlled conditions during experiments lasting for more than 2 years at 13 17 23 and 27 c in order to determine the variations in sr and ba partitioning relative to ca dsr and dba respectively between seawater and fish apatitic hard tissues i e teeth and bones as a function of temperature the sensitivity of the sr and ba thermometers i e dsr t and dba t respectively are similar in bone d b w sr t 0 0036 0 0003 and d b w ba t 0 0134 0 0026 respectively and enamel d e w sr t 0 0037 0 0005 and d e w ba t 0 0107 0 0026 respectively the positive values of dsr t and dba t in bone and enamel indicate that dsr and dba increase with increasing temperature a pattern opposite to that observed for inorganic apatite this distinct thermodependent trace element partitioning between inorganic and organic apatite and water highlights the contradictory effects of the crystal chemical and biological controls on the partitioning of ca sr and ba in vertebrate organisms taking into account the diet sr ca and ba ca values it is shown that the bone ba ca signature of fish can be explained by ca biopurification and inorganic apatite precipitation whereas both of these processes fail to predict the bone sr ca values therefore the metabolism of ca as a function of temperature still needs to be fully understood however the biogenic sr thermometer is used to calculate an average seawater temperature of 30 6 c using the sr ca compositions of fossil shark teeth at the cretaceous tertiary boundary and a typical seawater sr ca ratio of 0 02 finally while the present work should be completed with data obtained in natural contexts it is clear that sr ca and ba ca ratios in fossil biogenic apatite already constitute attractive thermometers for marine paleoenvironments

a numerical study on nonlinear surface wave evolution over viscoelastic mud abstract accurate prediction of wave energy dissipation over mud is essential for understanding nearshore circulation sediment transport processes and design of engineering projects along muddy coasts it is desirable to be able to simulate wave propagation over a wide range of mud behaviors as wave evolution is highly dependent on mud rheological characteristics in this study we develop a numerical model to simulate surface wave evolution over viscoelastic muds this new wave mud interaction model is comprised of a frequency domain phase resolving model for wave propagation that explicitly solves nonlinear wave wave interactions and a model for mud induced surface wave dissipation and modulation model results show satisfactory agreement with laboratory measurements of wave height and attenuation rates over mud and shows improvement over the model with a viscous mud mechanism the model is then used to investigate the combined effect of mud viscoelasticity and nonlinear wave wave interactions on surface wave evolution cnoidal and random wave simulations are conducted in general qualitative measures such as shape of cnoidal waves or pattern of variation in h r m s of random waves are dictated by direct mud induced damping which due to resonance effects has a substantially different structure over viscoelastic mud compared to viscous mud nonlinear interactions affect spectral shape and distribution of energy loss across the spectrum subharmonic interactions cause indirect damping of high frequencies but ameliorate damping of harmonics around mud s resonance frequency therefore neglecting mud elasticity can result in significant errors in estimation of bulk wave characteristics and spectral shape

wave dissipation by muddy seafloors 1 muddy seafloors cause tremendous dissipation of ocean waves here observations and numerical simulations of waves propagating between 5 and 2 m water depths across the muddy louisiana continental shelf are used to estimate a frequency and depth dependent dissipation rate function short period sea 4 s and swell 7 s waves are shown to transfer energy to long period 14 s infragravity waves where in contrast with theories for fluid mud the observed dissipation rates are highest the nonlinear energy transfers are most rapid in shallow water consistent with the unexpected strong increase of the dissipation rate with decreasing depth these new results may explain why the southwest coast of india offers protection for fishing and for the 15th century portuguese fleet only after large waves and strong currents at the start of the monsoon move nearshore mud banks from about 5 to 2 m water depth when used with a numerical nonlinear wave model the new dissipation rate function accurately simulates the large reduction in wave energy observed in the gulf of mexico

ecological and physiological variability of sr ca and ba ca in mammals of west european mid wurmian food webs the middle to upper paleolithic transition in western europe is characterized from an ecological point of view by large ungulate communities adapted to cold climatic conditions the aim of this study is to reconstruct the trophic relationships prevailing in these paleoecosystems which have no equivalent in the modern world bone and dentine remains representing five mammalian assemblages dated around 35 ka bp one of which included a neandertal specimen are investigated for sr ca and ba ca of bioapatites examination of the n content and u ree luminescence of bulk material ca p ratios and mn and ca contents of purified samples demonstrates that the sr ca and the ba ca ratios of bone and dentine samples are not significantly altered by diagenesis as a consequence of the biological discrimination of sr and ba in relation to ca sr ca and ba ca values are impoverished with increasing trophic position and are strongly correlated within a trophic web the slopes of the linear regressions between sr ca and ba ca are consistent with modern variability furthermore a statistical difference was found between ba ca of foregut and hindgut herbivores when coexisting collagen is preserved the sr ba ca and 15n are strongly correlated the distribution of values suggests that the 15n range is mainly controlled by the variability of soil conditions whereas the 13c range may be related to resource availability

rare earth elements and yttrium in seawater icp ms determinations in the east caroline coral sea and south fiji basins of the western south pacific ocean abstract using inductively coupled plasma mass spectrometry icp ms vertical profiles of yttrium and all the rare earth elements rees in seawater were obtained at three locations in the western south pacific the east caroline coral sea and south fiji basins based on the data we have analyzed the inter ree iii relationships and found that ree iii s heavier than dy and particularly close neighbors show strong coherencies in their oceanic behavior considering that the heavy ree iii s are less particle reactive than the light and middle ree iii s and that they have very tight correlations with regressions passing almost through the origin the neighboring element ratios of the heavy ree iii s behave virtually conservatively and are suitable as tracers of water masses the dy ho er system is practically good because its dynamic range signal to noise ratio is large in the ocean the highest ho dy ratios 0 31 are found in intermediate and deep waters throughout the western south pacific which overlie the antarctic bottom water with a low ho dy ratio 0 27 these high ho dy waters are probably formed in the polar and subantarctic frontal zone and advect northward ree iii data provide better insights into the deep water recirculation in the south pacific than those discussed based upon the regular oceanographic properties alone

rare earth distributions with a positive ce anomaly in the western north atlantic ocean from the vertical distributions of the rare earth elements ree in the sargasso sea we now report the first profiles of pr tb ho tm and lu in seawater together with profiles for la ce sm eu and yb the first observations of positive ce anomalies in seawater are ascribed to reducing inshore sediments as a source for ce ref 1 all vertical profiles are consistent with adsorption of trivalent rare earths by settling particles possibly siliceous or calcareous followed by their release at or near the sea floor on dissolution of the carriers the very different ce profile demonstrates the additional effects of oxidation reduction reactions

rare earth elements in old biogenic apatites abstract the ree distributions in individual upper devonian conodonts have been measured by ion probe the patterns of all analyzed conodonts are enriched in middle ree eu gd and have a weak or no ce anomaly concentrations and la yb or la sm ratios vary very little within or among individuals from the same zone which suggests that uptake of labile ree from sediments was essentially quantitative therefore the ree signature of the primary carriers probably organic and oxyhydroxides particulates from marine suspensions was efficiently transferred to biogenic apatites and survived late diagenetic processes ree patterns of conodonts do not resemble those of present day seawater and post cretaceous biogenic phosphates which are typically depleted in nd and sm with a negative ce anomaly since ree distributions in the modern water column mimic those of nutrients we assume that in pre cretaceous seawater they were not controlled by surface biological activity we assume instead that ree in pre cretaceous seawater can be explained by mechanism of desorption adsorption on particle surfaces progressive extraction of lree from river water by oxyhydroxides leads to precipitates enriched in middle ree a simple quantitative model was calculated in order to illustrate the proposed mechanism

rare earth element contents of jurassic fish and reptile teeth and their potential relation to seawater composition anglo paris basin france and england the rare earth element ree chemistry of jurassic shelf seawater from western europe anglo paris basin was investigated by analyzing the fish and reptile teeth deposited in shallow to deeper water 200 m environments ree patterns in apatites are controlled by the host sediments vertebrate teeth sampled from the siliciclastic sediments calcareous sandstones and shales show flat shale normalized ree patterns that reflect the dominant influence of the continental source from which the ree were derived carbonate deposits protected from the clastic sources contain fish and reptile teeth whose ree patterns reflect more accurately the ree composition of the overlying water column the ree patterns are similar through the bajocian to the oxfordian and are characterized by a depletion in heavy rare earth element dy ybn 1 8 5 0 compared to modern seawater compositions dy ybn 0 8 0 9 the fractionations among hree in the jurassic seawater are more efficient than in modern oceans and increases with depth instead of decreasing these hree removal processes operated as early as the paleozoic and disappeared during the late cretaceous the fractionation of hree relative to lree is correlated with the increasing depth of the basin as indicated by two independent criteria that are the sedimentary structures and the oxygen isotope composition of coexisting brachiopods the dy ybn ratio of the marine biogenic phosphates can be used as a proxy of paleo water depths at the scale of a water mass ce anomalies ce in biogenic apatite bearing limestones are variable and systematically negative relative to modern surface seawater and bathonian values mean ce 0 63 0 10 weak ce anomalies during the callovian mean ce 0 21 0 09 suggest the onset of more reducing conditions this redox change coincided with an increase of seawater temperatures as suggested by the oxygen isotope compositions measured on the same teeth we speculated that the callovian low ce could result from a decrease in the po2 due to the warming of seawater

the ree and end of 40 70 ma old fish debris from the west african platform ree concentrations and nd isotopic compositions have been determined in late cretaceous early cenozoic fish debris from west african and israeli platform sediments and show a strong regional control independent of time except for those from the northern morocco it is suggested that although diagenetic fluids do not contribute ree s directly to the phosphatic debris they may significantly change the ce anomaly and the end t value of the epicontinental seas which in turn control the ree in marine phosphates it is shown that over the investigated period the north moroccan shelf seawater was progressively flushed by deep north atlantic water

the temperature relationship in coralline aragonite influence of variability in and skeletal growth parameters this paper provides an evaluation of two of the most likely pitfalls of sr ca thermometry i e the effect of biogenic cycling of sr vs ca in the surface ocean and the effect of variable extension rate on sr incorporation in coralline aragonite the authors also report calibration of the sr ca temperature relationship for three coral species porites lobata pocillopora eydouxi and pavona clavus collected for the hawaiian and galapagos islands analyses of seawater samples show significant spatial and depth variability in the sr ca ratio the uncertainty introduced by this effect is estimated to be 0 2 degrees c for corals located in tropical oligotrophic waters and potentially larger for corals located in upwelling areas sr ca along two different growth axes of a galapagos pavona clavus with annual extension rates of approximately 6 and 12 mm y respectively indicate an offset of 1 2 degrees c with higher sr ca values associated with slower extension rates the offset observed between the two growth axes may be the result of variations in extension and or calcification rate these results are important in determining past sea surface temperatures for reconstruction of paleoclimates

fractionation of rare earth elements within bone mineral a natural cation exchange system the distribution of rare earth elements rees within fossil bones is controlled by their partition coefficients between apatite and pore waters and the rate of diffusion through the bone using simple theoretical models we show that rees are strongly fractionated from one another during diffusive transport and adsorption fractionation occurs due to the relative ease of substituting ree ions of differing ionic radius into the ca sites in the apatite lattice and the degree of fractionation is dependent on the rate of diffusion of ions within bone and therefore the rate of recrystallisation variations in bone thickness recrystallisation rate and potentially pore water composition may all influence the relative distribution of rees and thus ree ratios within bones increases in bone thickness and reductions in either diffusion coefficients or the duration of ree uptake lead to enhanced fractionation of rees in our model simulations interpretations of ree ratios in fossil bones either for palaeoenvironmental or taphonomic applications must consider how fractionation will influence ree ratios within bones particularly when interpreting spatially resolved analyses within single bones

modelling study of wave damping over a sandy and a silty bed abstract laboratory experiments have been carried out to investigate wave damping over the seabed in which the excess pore pressure and free surface elevations are synchronously measured for examining the wave induced soil dynamics and wave kinematics two types of soil namely fine sand and silt are tested to examine the role of soil in the wave damping observation of experiments shows that i soil liquefaction takes place for some tests with silty bed and soil particles suspend into the water layer when the bed is made of silt ii sand ripples can be generated for experiments with sand bed measurements reveal that the wave damping greatly depends on the soil dynamic responses to wave loading and the wave damping mechanism over the silty seabed differs from that over the sand bed on the one hand the wave damping rate is greatly increased when soil liquefaction occurs in the silty bed on the other hand the presence of sand ripples generated by oscillatory flow in the sand bed experiments also increases the wave damping to some extent furthermore experimental results show that soil particle suspension in the silt bed test contributes to the wave damping theoretical analysis is presented to enhance discussions on the wave damping the theoretical calculations demonstrate that the wave damping is mainly induced by the shear stress in the boundary layer for the cases when no liquefaction occurs while for the cases when soil liquefaction takes place the viscous flow in the liquefied layer contributes most towards to the wave damping

wave sediment interaction on a muddy inner shelf during hurricane claudette measurements of wave and suspended sediment concentration ssc were conducted near the 5 m isobath on the muddy inner shelf fronting atchafalaya bay louisiana during hurricane claudette the data show that wave and current activity resuspended large quantities of sediment with ssc r 0 5 kg m 3 throughout the water column in the waning phase of the storm settling generated a suspension layer with concentrations over 1 7 kg m 3 measured as high as 1 m above the bottom numerical simulations of post storm sediment settling showed that observations are consistent with a high density fluid mud layer ssc between 10 and 20 kg m 3 and separated from the upper water column by a lutocline located at about 1 m above the bottom the formation of the fluid mud layer is correlated with strong broad spectrum wave dissipation consistent with the hypothesis that surface interface wave interaction plays an important part in the energy transfer from the surface to the soft bottom 2004 elsevier ltd all rights reserved

nonlinear wave dynamics in the presence of mud induced dissipation on atchafalaya shelf louisiana usa abstract the interplay between wave nonlinearity and mud induced dissipation is studied here using wave and sediment transport measurements collected in winter 2008 on the atchafalaya shelf louisiana between the 8 m and the 4 m isobaths this study focuses on the relatively energetic storm that occurred on march 4th 2 m wave height in 8 m water depth which caused significant bed reworking and left in its wake a 20 cm layer of hindered settling fluid mud while the net wave dissipation rate was maximal during the hindered settling phase after the storm consistent with previous observations significant dissipation was observed throughout the storm duration with a secondary maximum associated with the peak of the storm and the maximum bed reworking effects the effects of mud induced dissipation on the nonlinear shoaling process are investigated here using triads a newly developed spectral model for nonlinear shoaling of waves with mud parameter values estimated using a crude inverse modeling approach the model was used to separate the effects of mud induced dissipation from nonlinear transfers during both the erosion and deposition phases of bed reworking numerical simulations show that nonlinear transfers are always active even under strong dissipation regimes remarkably they also suggest that heavy mud induced dissipation causes the nonlinear energy cascade to revert direction with bulk transfers occurring from high frequency to low frequency spectral bands this supports the hypothesis that the interplay between mud induced dissipation which is much more significant than the bottom dissipation over sandy beds and wave nonlinearity can drain energy from the entire spectrum and not just from the frequency bands that interact directly with the seafloor the decay of high frequency variance induced by the reversal of spectral flux in effect reduces the nonlinearity of the wave field

observations on cohesive bed reworking by waves atchafalaya shelf louisiana 1 wave current acoustic backscatter and suspended sediment concentration measurements both single point and vertical profiles estimated by conversion of acoustic backscatter data are used to investigate wave current cohesive sediment interaction on the muddy atchafalaya inner shelf during an energetic storm we propose that bed state follows a cycle of dilation due to fluidization erosion deposition with fluid mud formation and consolidation a one dimensional vertical cohesive sediment transport model is calibrated using current and concentration profiles to estimate the physical parameters that could not be measured directly e g bottom stresses estimated bed position and computed bottom stresses suggest that the critical erosion threshold is in the range of 0 3 pa to 0 5 pa the study site is impacted by a sediment laden fresh water plume coming from the atchafalaya river mouth bed density evolution during the storm is estimated from vertical sediment exchange between the water column and the bed excluding the duration of passage of a sediment carrying water front the values are in the range of 1 030 kg m3 to 1 200 kg m3and indicate that the bed density increases during the erosion phase and decreases during deposition at the end of the storm it shows a steady increasing trend during hindered settling and exceeds the space filling value during consolidation both the critical erosion shear stress and bed density values are consistent with the results of laboratory tests on samples from the experimental site

direct u pb dating of cretaceous and paleocene dinosaur bones san juan basin new mexico vertebrate fossils have been important for relative dating of terrestrial rocks for decades but direct dating of these fossils has heretofore been unsuccessful in this study we employ recent advances in laser ablation in situ u pb dating techniques to directly date two dinosaur fossils from the san juan basin of northwestern new mexico and southwestern colorado united states a cretaceous dinosaur bone collected from just below the cretaceous paleogene interface yielded a u pb date of 73 6 0 9 ma in excellent agreement with a previously determined 40 ar 39 ar date of 73 04 0 25 ma for an ash bed near this site the second dinosaur bone sample from paleocene strata just above the cretaceous paleogene interface yielded a paleocene u pb date of 64 8 0 9 ma consistent with palynologic paleomagnetic and fossil mammal biochronologic data this first successful direct dating of fossil vertebrate bone provides a new methodology with the potential to directly obtain accurate dates for any vertebrate fossil

high resolution analysis of uranium and thorium concentration as well as u series isotope distributions in a neanderthal tooth from payre ardeche france using laser ablation icp ms we have mapped u 238 u and th 232 th elemental concentrations as well as u series isotope distributions in a neanderthal tooth from the middle palaeolithic site of payre using laser ablation icp ms the u concentrations in an enamel section varied between 1 and 1500 ppb the u concentration maps show that u migration through the external enamel surface is minute the bulk of the uranium having migrated internally via the dentine into the enamel the uranium migration and uptake is critically dependent on the mineralogical structure of the enamel increased u concentrations are observed along lineaments some of which are associated with cracks and others may be related to intra prismatic zones or structural weaknesses reaching from the dentine into the enamel the uranium concentrations in the dentine vary between about 25 000 and 45 000 ppb our systematic mapping of u concentration and u series isotopes provides insight into the time domain of uaccumulation most of the uranium was accumulated in an early stage of burial with some much later overprints none of the uranium concentration and u series profiles across the root of the tooth complied with a single stage diffusion adsorption d a model that is used for quality control in u series dating of bones and teeth nevertheless in the domains that yielded the oldest apparent u series age estimates u leaching could be excluded this means that the oldest apparent u series ages of around 200 ka represent a minimum age for this neanderthal specimen this is in good agreement with independent age assessments 200 230 ka for the archaeological layer in which it was found the th elemental concentrations in the dental tissues were generally low between about 1 and 20 ppb and show little relationship with the nature of the tissue 2008 elsevier ltd all rights reserved

video and field observations of wave attenuation in a muddy surf zone abstract besides the different scales within which coastal processes manifest their energy the majority of the world s coastal regions exhibit forms of sediment heterogeneity that are physically significant one example of a heterogeneous environment is cassino beach located at the southernmost part of brazil a fine grain sized sandy beach where fluid mud sporadically is transported to the nearshore and eventually onto the beach at this site in 2005 as part of a field experiment a video system was installed three years after the installation a large mud transgression event took place in february 2008 and had 5 km of extension in this context the goal of the present work is to characterize the mud deposition pattern across the surf zone describing the consequences of mud on nearshore dynamics using remote sensing techniques beach profiles and suspended matter concentration the surveyed beach profiles registered the deposition of fluid mud at the inner surf zone with concentrations up to 12 mg l the material was deposited close to the shoreline and had a cross shore width of 100 m during the first deposition day occupying the entire water column from surf zone time series of pixel intensity it was possible to detect the attenuation of the surface wave spectra due to the presence of fluid mud the combination of video techniques and field data allowed one to follow the formation of a double layer system where fluid mud overlays the sandy bottom the video based system at cassino demonstrated that remote detection of fluid mud and quantification of its effect on the nearshore dynamics is feasible the combination of beach profiles measurements of suspended matter concentration and intensity timestacks allowed the analysis of the short term evolution of the mud depositional processes

experimental study of igneous and sedimentary apatite dissolution control of ph distance from equilibrium and temperature on dissolution rates apatite dissolution experiments were conducted using both a fluidized bed and stirred tank reactor over a range of ph temperature solution saturation state and on non carbonated and carbonated apatite compositions igneous fluorapatite fap and sedimentary carbonate fluorapatite cfa respectively from 2 8 5 were not possible due to detection limits of the analytical techniques used in this study and the high insolubility of fap for the cfa compositions studied the dissolution rate decreased with increasing ph from 4 ph 7 during early stages of the dissolution reaction for both fap and cfa mineral components were released in non stoichiometric ratios with reacted solution ratios of dissolved ca p and ca f being greater than mineral stoichiometric ratios suggesting that ca was preferentially released compared to p and f from the mineral structure during the early stages of dissolution an increase in reacted solution ph accompanies this early elevated release of ca as the dissolution reaction proceeded to steady state dissolution became congruent when normalized to bet measured surface area fap dissolved faster from 4 ph 7 compared to cfa the apparent arrhenius activation energy ea of fap dissolution over the temperature range of 25 55 c at ph 3 0 i 0 1 and pco2 0 is 8 3 0 2 kcal mol 1 both the apparent exchange of solution h for solid bound ca at low ph in the early stage of dissolution and the ea of dissolution suggest a surface and not a diffusion controlled dissolution reaction for fap and cfa the degree of undersaturation of the solution gr with respect to fap was important in determining the dissolution rate at ph 3 0 i 0 1 and pco2 0 the dissolution rate of fap was 5 greater in the far from equilibrium region compared to the near equilibrium slope region a simple apatite weathering model incorporating the experimental results from this study was constructed and numerical calculations suggest that during the phanerozoic both the surface area of igneous rock available for weathering and the average global temperature were important factors in determining the p weathering flux from apatite dissolution it is possible that elevated global temperatures coupled with relatively high surface area of igneous rock during the early to mid paleozoic resulted in elevated p weathering fluxes which along with climatic evolutionary pressures of the neoproterozoic facilitated the radiation of multicellular organisms large scale phosphorite deposition and abundance of calcium phosphate shelled organisms during the early cambrian

differential diagenesis of strontium in archaeological human dental tissues the investigation of prehistoric human migration from the measurement of sr isotope ratios within preserved tissue is critically dependent on the preservation of biogenic sr a number of recent studies have involved isotope ratio measurements on samples of archaeological tooth and bone but doubt remains as to the extent of diagenesis in various skeletal tissues and the effectiveness of procedures designed to decontaminate them the authors have compared sr abundance and isotope ratios in enamel and dentine from archaeological teeth in order to assess the integrity of the biogenic sr signal preserved within the respective tissues it is concluded that enamel appears in most cases to be a reliable reservoir of biogenic sr but that dentine and by implication bone is not the diagenesis of dentine is highly variable even between burials within a single site for the majority of teeth dentine diagenesis was not simply by addition of soil derived sr but involved substantial sometimes complete turnover of the original biogenic material it is suggested that for most of the samples investigated current decontamination techniques may not have been effective in isolating biogenic sr from dentine similar considerations are likely to apply to archaeological and fossil bone but the possibility arises to use dentine and enamel measurements to assess the effectiveness of decontamination procedures which may then be used for bone

trace elements in conodont phosphates from the frasnian famennian boundary abstract rare earth elements ree and th concentrations on individual devonian conodonts were measured by icp ms from stratigraphic sections across the frasnian famennian f f boundary in the montagne noire southern france and morocco the present data confirm the reversed concavity of the ree spectra found by wright et al 1986 which is a characteristic although poorly understood feature of the ancient oceanic sediments within the layers corresponding to the upper kellwasser and the f f events the ce ce ratios show only minor changes with respect to younger and older sediments the magnitude of the ce anomaly is nevertheless consistently weak over all the sections if as in modern oceans the biologically mediated ce anomaly in particles and seawater originates in the uppermost water column the present observations suggest a global decrease in the biological productivity lower productivity is supported by the decreasing abundance of conodont elements during the upper kellwasser but continuing carbonate deposition through this period still makes evidence quite equivoqual as a proxy to th pa fractionation in modern sediments the th la fractionation is a potential tracer of the rate of horizontal exchange of seawater between deep sea and continental margins which may be correlated with eustatic sea level fluctuations during the upper kellwasser crisis the th la ratios fall significantly in all the sections this can reflect reduced exchanges between the deep sea and continental margins it is suggested that the f f extinction event was the result of the coincidence between a rather modest transgression event and global suboxia

regional variations of seismic attenuation from coda and l g waves in northern baja california attenuation of coda and lg waves was estimated from events recorded by the seismic network of northern baja california red sismica del noroeste de mexico resnom in the frequency band 1 to 12 hz in order to find a regional variation of qc crustal quality factor for s waves in northern baja california mexico we used the single scattering model of sato 1977 in the time domain to estimate quality factor qc and a spectral approach to relate acceleration spectra with distance to estimate the anelastic attenuation coefficient of lg waves we calculated qc for short 10 s and long lapse times 70 s using local events and the events that originated at the main tectonic features of the area assuming a frequency dependence of qc of the form qc qc we observed for short lapse times a regional variation of q0 with low values from about 53 in the inner continental borderland icb province to about 115 in the peninsular ranges pr and 144 in the gulf of california depression gcd province the values range from 0 70 and 0 85 for events in the icb and pr to 0 44 in the gcd region for long lapse times and for events located in the pr we found q0 values from 49 at stations within the icb to 101 at stations within the gcd attenuation coefficient of lg waves between 1 and 6 hz was also estimated using events located in southern california with source station distances up to 420 km we found that frequency dependence of was higher for source receiver paths going from a typical continental structure to a pull apart basin the gcd province than for paths within the pr using all data in a linear inversion process and assuming a group velocity vlg of 3 4 km s we obtained a power law dependence of the form qlg 288 20 0 32 02

sm nd in marine carbonates and phosphates implications for nd isotopes in seawater and crustal ages this study explores the possibility of establishing nd isotopic variations in seawater over geologic time calcite aragonite and apatite are examined as possible phases recording seawater values of nd modern biogenic and inorganically precipitated calcite and aragonite from marine environments were found to have nd concentrations of from 0 2 to 70 ppb showing that primary marine caco 3 contains little ree and that nd ca is not greatly enhanced relative to seawater during carbonate precipitation very young marine limestone and dolomite containing no continental detritus have 200 ppb nd all the carbonates are lree enriched 0 16 sm nd 0 45 modern and very young atlantic and pacific carbonates have nd in the range of shallow atlantic and pacific seawater respectively implying that they derive their ree from local seawater the nd in well preserved carbonate fossils is 4 10 4 ppb much greater than in their modern counterparts but like the high values found for carbonates in other studies we believe the high ree contents at the 500 ppb level in some detritusfree carbonates are due to ree rich fe hydroxide in on the carbonate in favorable cases such material may record seawater nd values however introduction of extraneous ree may obscure the original isotopic composition of pure caco 3 because of its very low intrinsic primary ree abundance modern biogenic apatite is also shown to have very low ree content 150 ppb nd but appears to quickly scavenge ree from seawater inorganically precipitated apatite from phosphorites has high concentrations of seawater derived ree young phosphorite apatite from the atlantic and pacific oceans has nd in the range of the seawater from these oceans older apatite samples of similar age from different localities bordering common oceans record similar values of nd t sedimentary apatite has sr t values in good agreement with the curves for 87 sr 86 sr of seawater as a function of time individual conodonts from a single formation yield the same sr t and nd t other workers have shown that sedimentary apatite preserves seawater ree patterns these characteristics suggest that sedimentary apatite can be used to determine nd t in ancient seawater the seawater values so inferred range between 1 7 and 8 9 over the last 700 my and lie in the range of modern seawater showing no evidence for drastic changes high values of seawater nd t in the triassic and latest precambrian may correlate with the breakup of large continental landmasses the initial nd t 15 0 of a 2 ae old phosphorite implies the presence of 1 5 ae old continental crust at 2 ae ago the approach outlined here can be used to constrain the age of the exposed crust as a function of time

field observation of wave damping by fluid mud abstract extensive mud deposits are found off cassino beach brazil the wave damping over the muddy bottom was studied using field measurements by applying a technique of spectral analysis we showed that the wave attenuation occurred differently throughout the wave spectra field measurements revealed that the maximum wave energy dissipation took place over the deposit s depocenter and that lutocline height varied significantly in the order of days the results indicated that short waves from 3 75 to 6 25 s underwent the greatest damping due to the interaction with fluid mud an idealized 1 d model helped to explain the observations

timescales and mechanisms of ree and hf uptake in fossil bones abstract rare earth element ree patterns of fossil bones and teeth are widely used as proxies for provenance taphonomy and palaeoenvironment in order to investigate if fossil bones behave as closed systems over geologic time ree profiles were analysed by la icpms along cross sections of 54 bones from various well characterised and well dated settings these include terrestrial and marine diagenetic environments covering early triassic to holocene ages in general all fossil bones exhibit the highest ree concentrations at the outer rim gradually decreasing by up to four orders of magnitude toward the inner bone cortex intra bone ree concentration gradients decrease significantly from quaternary via tertiary to mesozoic specimens suggesting long term ree uptake and open system behaviour of fossil bone this view is further corroborated by 176lu 176hf dating of selected samples all yielding significantly younger ages than the known chronostratigraphic ages hence there is clear evidence for long term open system behaviour of fossil bones with respect to ree which is in marked contrast to currently accepted models suggesting that ree uptake is only early diagenetic although unexpected statistically significant four to seven point isochrons are observed for four fossil dinosaur bone samples and one upper triassic mastodonsaurus tooth with mswds ranging from 0 083 to 4 5 notably mobility of lu alone cannot account for the observed age patterns assuming constant lu uptake rates over time the radiometric ages should only be as low as half of the chronostratigraphic age however a six point isochron defined by subsamples of a single upper triassic mastodonsaurus tooth yields an age of 65 2 1 1 ma mswd 0 68 much younger than half of the stratigraphic age ca 234 ma hence hf must also undergo late diagenetic exchange likely mechanisms to account for the presence of statistically meaningful isochrons as well as for the late diagenetic exchange of both ree and hf are diffusion adsorption and dissolution reprecipitation processes

source distribution and economic significance of trace elements in groundwaters from lake tyrrell victoria australia abstract anomalous radioactivity highlighted the lake tyrrell area as a potential mineral exploration target and prompted a 5 year study of its groundwater geochemistry the groundwaters are very acid median ph 4 2 and saline median ionic strength i 1 24 some samples contain unusually high concentrations of cu up to 3 5 mg l 1 pb up to 38 5 mg l 1 and al up to 155 mg l 1 concentrations of most other trace elements exceed seawater values but are not different from those in groundwaters near two other randomly selected australian salt lakes waters with elevated trace element concentrations are spread at isolated sites across the area but some clustering of cu pb enriched waters occurs in the west and southeast r and q mode correspondence analysis identifies factors which relate to both trace elements and samples and are interpreted as reflecting processes whereby trace elements are taken into groundwaters factor 1 involves al cu fe mn and zn whose concentrations relate directly to high acidity factor 2 involves b and sr and probably relates to local sediment enrichments of b and sr factor 3 is strongly weighted by pb and can be explained by contact between groundwaters and locations where clays organic solids and fe mn oxides are particularly enriched by heavy metals factor 4 involves f y and i and probably relates to residual mineral dissolution sample locations grouped according to the influence of each factor on each groundwater composition identify zones where a particular process is dominant laboratory leaching of blanchetown clay and parilla sand confirms that many of the trace elements could have entered the groundwater from local aquifer sediments the potential of these waters as agents of present or future ore formation is also considered by comparing amounts of trace elements carried into the salt lake basin over the last 30 kyr with what persists in present day lake brines results demonstrate that large tonnages of trace elements appear to have been deposited but that sediment dilution mitigates against ore grade concentrations

new lu hf and pb pb age constraints on the earliest animal fossils abstract the neoproterozoic doushantuo formation south china preserves a unique assemblage of early multicellular fossils and overlies rocks which are thought to have formed during an ice age of global extent the age of this formation is thus critical for understanding the important biological and climatic events that occurred towards the end of the proterozoic eon until now direct dating of sedimentary formations such as the doushantuo has been difficult and associated with large uncertainties here we show that dating of doushantuo phosphorites by a novel lu hf dating method and conventional pb pb geochronometry independently yield ages of 584 26 ma and 599 3 4 2 ma respectively these ages are in agreement with bio and chemostratigraphical observations and show that the doushantuo animal remains predate diverse ediacaran fossil assemblages making them the oldest unambiguous remains of metazoans currently known furthermore the pb pb age for the post glacial doushantuo rocks suggests that the neoproterozoic glaciation in china might predate glacial rocks in eastern north america commonly associated with the younger marinoan of two major neoproterozoic glaciations the combination of lu hf and pb pb dating shows considerable potential for dating other phosphorite successions and future application of these methods could therefore provide further constraints on proterozoic biological and environmental history

responses of bingham plastic muddy seabed to a surface solitary wave in this paper we investigate the dynamics of muddy seabed motions induced by a surface solitary wave the muddy seabed is characterized as bingham plastic mud we focus our attention on the situations where the horizontal scale of the wave induced mud flow is much larger than the vertical scale the thickness of the mud layer is also assumed to be much smaller than the water depth above with these simplifications the dynamic pressure in the mud column remains a constant and the vertical displacement of the water mud interface is negligible the horizontal gradient of the wave induced dynamic pressure along the water seabed interface drives the motions in the mud bed for a bingham plastic muddy seafloor the mud moves either like a solid plug flow or like a viscous fluid shear flow depending on whether the magnitude of shear stress is in excess of the yield stress velocities inside these two different flow regimes and the location s of the yield surface s vary in time as functions of water mud interfacial pressure gradient and the properties of the bingham plastic mud a semi analytical approach is developed in this paper to analyse the motions inside the mud bed under a surface solitary wave loading three possible scenarios are discussed to illustrate the complexity of the seafloor responses the formula for the damping rate caused by the energy dissipation inside the muddy seabed is also derived using realistic values of the physical parameters the present results for damping rate agree qualitatively with the available field observations

u pb dating of fossil enamel from the swartkrans pleistocene hominid site south africa abstract we demonstrate that young fossil enamel older than the range of the u series 300 ka can be dated by the u pb methods using new models of u and pb loss and uptake contrary to the current hypothesis of u uptake that only considers the adsorption diffusion mechanism we here develop a complete time dependent model which takes gains and losses of the most critical nuclides 238u 234u and 230th into account both during chemical dissolved u and physical th and u recoil processes lead is assumed to be a mixture between two components of common pb and a radiogenic component the proportions of these components are calculated from the pb isotope abundances and u pb ratios we apply this new u pb method to bovid enamel from the swartkrans cave gauteng province south africa this cave has yielded abundant early pleistocene hominid remains attributed to paranthropus and homo as well as various associated archaeological vestiges biochronological comparisons with east africa have provided age estimates ranging between 1 8 and 1 0 ma which however remain poorly constrained after correction for initial 234u disequilibrium and further 238u loss the u and pb isotope data yield ages of 1 83 1 38 1 36 0 29 and 0 83 0 21 ma for the three stratigraphic units members 1 2 and 3 respectively we discuss the consequences of these radiometric results for hominid evolution in south africa