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

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

characterization of the unconventional tuscaloosa marine shale reservoir in southwestern mississippi usa insights from optical and sem petrography abstract this study presents new optical petrography and electron microscopy data interpreted in the context of previously published petrophysical geochemical and mineralogical data to further characterize the tuscaloosa marine shale tms as an unconventional reservoir in southwestern mississippi the basal high resistivity zone has a higher proportion of type ii sedimentary organic matter than the overlying tms indicating it is more prone to oil generation optical petrography and electron microscopy reveal a heterogeneous clay matrix with ubiquitous pyrite grains quartz feldspar glaucony foraminifera shell fragments and rarer occurrences of apatite and crinoid fragments as well as liptinite alginite inertinite and vitrinite our petrographic observations suggest that higher abundances of detrital quartz grains coupled with minimal authigenic cements result in higher porosity and permeability however the tms is also more clay rich than other unconventional shale oil and gas plays which can impair the effectiveness of hydraulic fracture stimulation thin section observations reveal alternating clay and calcium carbonate laminae that are interpreted to reflect changes in sediment flux planktonic foraminifera indicate an overlying oxygenated water column while benthic inoceramid fragments and pervasive authigenic pyrite suggest anoxic or dysoxic bottom water conditions apatite fragments in thin section suggest mixing events and an influx of nutrient rich sediments overall these observations suggest that a variety of paleodepositional environments occurred in the tms and the lithofacies diversity resulting from these small scale depositional cycles makes it difficult to determinatively identify areas conducive to enhanced economic hydrocarbon recovery

sulfur isotopic studies of archean slate and graywacke from northern minnesota evidence for the existence of sulfate reducing bacteria abstract sulfur isotopic studies of pyrite from metasediments in the 2 6 byr old deer lake green stone sequence minnesota have been conducted in order to evaluate the possible importance of sulfate reducing bacteria in sulfide formation pyrite occurs as ovules up to 2 cm in diameter within graphitic slates and as fine disseminations in metagraywacke units sem studies indicate the pyrite is framboidal in morphology 34 s values of pyrite from the deer lake sediments range from 2 3 to 11 1 with a peak at 2 isotopic data are consistent with either high temperature inorganic reduction of circulating seawater sulfate or low temperature bacterial reduction however the lack of sulfide bands or massive occurrences in the sediments the restriction of pyrite mineralization to the sediments and the absence of evidence for hot spring activity suggest that a diagenetic origin of pyrite is more feasible sulfide in such an environment would be produced principally by the action of sulfate reducing bacteria results of the study are in agreement with those of goodwin et al 1976 who suggest that dissimilatory sulfate reduction was operative in the archean ocean some 2 75 byr ago

apatite for destruction isotopic and geochemical analyses of bioapatites and sediments from the upper devonian escuminac formation miguasha quebec abstract the paleoenvironmental context and diagenetic history of the middle frasnian escuminac formation were investigated through geochemical rare earth elements and isotopic rb sr nd sm analyses of fossil fish material and sediments samples of sediments and bioapatite were collected from the base to the top of the escuminac formation strontium isotope ratios 87 sr 86 sr for bioapatites vary from 0 70804 to 0 70845 and overlap with frasnian seawater sr isotope compositions though most of the biogenic apatites analyzed show a variable drift from marine values toward a more radiogenic continental signature this trend is possibly the result of post mortem sr exchange between fossils and a fluid isotopically distinct from the waters in which they developed all bioapatites are heavily enriched in rare earth elements ree and display a shale normalized pattern that shows heavy ree hree depletion and a slight middle ree mree enrichment the e nd t values of the sediments range from 4 8 to 6 4 and are consistent with a sedimentary provenance derived from an appalachian source for the escuminac formation in contrast more radiogenic e nd t values ranging from 2 6 to 4 6 were obtained for the bioapatites the discrepancy between sediments and fossil material e nd t implies the presence of a second diagenetic nd reservoir for the escuminac bioapatites we propose that this reservoir reflects in part seawater the similarity between the nd isotope compositions of the escuminac fossils and late devonian conodonts from poland argues for a close connection between waters of the devonian rheic ocean and the escuminac formation collector basin

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

rapid and sustained surface ocean acidification during the paleocene eocene thermal maximum the paleocene eocene thermal maximum petm has been associated with the release of several thousands of petagrams of carbon pg c as methane and or carbon dioxide into the ocean atmosphere system within 10 kyr on the basis of the co occurrence of a carbon isotope excursion cie widespread dissolution of deep sea carbonates and global warming in theory this rapid carbon release should have severely acidified the surface ocean though no geochemical evidence has yet been presented using boron based proxies for surface ocean carbonate chemistry we present the first observational evidence for a drop in the ph of surface and thermocline seawater during the petm planktic foraminifers from a drill site in the north pacific ocean drilling program site 1209 show a 0 8 decrease in boron isotopic composition 11b at the onset of the event along with a 30 40 reduction in shell b ca similar trends in 11b are present in two lower resolution records from the south atlantic and equatorial pacific these observations are consistent with significant global acidification of the surface ocean lasting at least 70 kyr and requiring sustained carbon release the anomalies in the b records are consistent with an initial surface ph drop of 0 3 units at the upper range of model based estimates of acidification

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

neodymium isotope evolution of nw tethyan upper ocean waters throughout the cretaceous neodymium isotope compositions of twenty four fish teeth nineteen from the nw tethys and five from different locations within the tethys are interpreted to reflect the evolution of tethyan upper ocean water composition during the cretaceous and used to track changes in erosional inputs to the nw tethys and in oceanic circulation throughout the cretaceous the rather high end up to 7 6 of the nw tethyan upper ocean waters recorded from the late berriasian to the early aptian and the absence of negative excursions during this interval support the presence of a permanent westward flowing tethys circumglobal current tcc this implies that temperature variations during this time period inferred from the oxygen isotope analysis of fish tooth enamel were not driven by changes in surface oceanic currents but rather by global climatic changes the results presented here represent a significant advance over previously published cretaceous seawater nd isotope records our newly acquired data now allow the identification of two stages of low end values in the nw tethys during the early albian middle albian interval down to 10 and the santonian early campanian down to 11 4 which alternate with two stages of higher end values up to 9 during the late albian turonian interval and the maastrichtian used in conjunction with the oxygen isotope record the fluctuations of end values can be related to major climatic oceanographic and tectonic events that appeared in the western tethyan domain d 2005 elsevier b v all rights reserved

the behavior of rare earth elements in seawater precise determination of variations in the north pacific water column abstract we present new highly precise and accurate data for ten rare earth elements rees in two water column profiles and in bottom waters from three additional localities in the north pacific our results presented here and in an earlier publication indicate that the water column in the western north pacific is stratified with respect to the isotopic composition of nd as well as nd la sm nd and er la both the nd isotopic and the ree data show that ree transport is strongly influenced by horizontal advection even in the sluggish circulation of the pacific in general rees increase in concentration with depth at mid latitude they reach a maximum concentration at about 3000 m and then decrease to the bottom at high latitude heavy rees reach a maximum concentration near 3000 m whereas light rees continue to increase in concentration with depth the deep water maximum and bottom water depletion is interpreted as an advective feature resulting from the flow of a lower concentration of rees in antarctic bottom water under a higher concentration of rees in the north pacific concentrations of rees do not show a linear relationship with those of si indicating that the ree cycle is not directly coupled to that of the si cycle ree element ratios i e nd la correlate with hydrographie properties which suggests that major features of the ree patterns may be conserved during lateral transport comparison of our ree data to those in previously published reports on pacific seawater shows that the identification of ree distributions affected by advection is only made possible by the high precision analysis we developed for this study the ce concentration we observe is relatively constant over 200 4500 m depth at both sites where we have complete profiles this unique constancy of ce is in contrast to the contiguous rees la and nd which show substantial concentration variations with depth

tectonically restricted deep ocean circulation at the end of the cretaceous greenhouse the evolution of global ocean circulation toward deep water production in the high southern latitudes is thought to have been closely linked to the transition from extreme mid cretaceous warmth to the cooler cenozoic climate the relative influences of climate cooling and the opening and closure of oceanic gateways on the mode of deep ocean circulation are however still unresolved here we reconstruct intermediate to deep water circulation for the latest cretaceous based on new high resolution radiogenic neodymium nd isotope data from several sites and for different water depths in the south atlantic southern ocean and proto indian ocean our data document the presence of markedly different intermediate water nd isotopic compositions in the south atlantic and southern ocean in particular a water mass with a highly radiogenic nd isotope signature most likely originating from intense hotspot related volcanic activity bathed the crest of walvis ridge between 71 and 69 ma which formed a barrier that prevented deep water exchange between the southern ocean and the north atlantic basins we suggest that the cenozoic mode of global deep ocean circulation was still suppressed by tectonic barriers in the latest cretaceous and that numerous mostly regionally formed and sourced intermediate to deep waters supplied the deep ocean prior to 68 million yr ago

neodymium isotopic reconstruction of late paleocene early eocene thermohaline circulation abstract high resolution fish tooth nd isotopic records for eight deep sea drilling project and ocean drilling program sites were used to reconstruct the nature of late paleocene early eocene deep water circulation the goal of this reconstruction was to test the hypothesis that a change in thermohaline circulation patterns caused the abrupt 4 5 c warming of deep and bottom waters at the paleocene eocene boundary the paleocene eocene thermal maximum petm event the combined set of records indicates a deep water mass common to the north and south atlantic southern and indian oceans characterized by mean nd values of 8 7 and different water masses found in the central pacific ocean nd 4 3 and caribbean sea nd 1 2 the geographic pattern of nd isotopic values before and during the petm suggests a southern ocean deep water formation site for deep and bottom waters in the atlantic and indian ocean basins the nd data do not contain evidence for a change in the composition of deep waters prior to the onset of the petm this finding is consistent with the pattern of warming established by recently published stable isotope records suggesting that deep and bottom water warming during the petm was gradual and the consequence of surface water warming in regions of downwelling

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

rare earth element systematics of fossil bone revealed by la icpms analysis intra bone rare earth element ree fractionation trends were studied by la icpms analysis to put constraints on 1 the mechanisms controlling ree fractionation within fossil bones 2 the relative timing of ree uptake in various parts of fossil bone and 3 the origin of ree in fossil bones we have evaluated ree bone profiles across 54 fossil bones from a broad range of well characterised taphonomic settings ranging in age from triassic to early medieval ree patterns and concentration gradients are highly variable and intra bone fractionation trends in la yb n vs la sm n space of few specimens cover almost the entire range previously observed for bulk samples intra bone variability of ce anomalies as well as variable y ho and la la n is also observed sometimes diagenetic fluids with fractionated hree enriched compositions have entered the bone from the marrow cavity producing secondary ree uptake profiles theoretical intra bone fractionation trends modelled using lattice strain theory concur with most ree data but some trends cannot be modelled using realistic boundary conditions this fact as well as the occurence of positive and negative ce anomalies within the same fossil sample hint towards changing ree compositions of diagenetic fluids over the timescales of ree uptake because apparent ce anomalies frequently evolve over bone profiles and ce anomalies can be inherited from previous fractionation events ce anomalies are a highly ambiguous tracer for constraining ambient redox conditions in general bioapatite ree signatures may not always reliably reflect ambient taphonomic or redox conditions and diagenetic fluid compositions therefore ree patterns and ce anomalies of fossil bones must be interpreted cautiously as they vary spatially within skeletal remains and are affected by intra bone fractionation processes as well as changing compositions of the diagenetic fluid

formation of southern component water in the late cretaceous evidence from nd isotopes constraining deep ocean circulation during past greenhouse climatic periods such as the cretaceous is important for understanding meridional heat transfer processes controls on ocean anoxia and the relative roles of climate and tectonics in determining paleocirculation patterns ocean circulation models for the late cretaceous and early paleogene suggest that significant deep water production occurred in the southern ocean but cannot constrain when this process commenced or what the temporal relationship was between opening tectonic gateways and late cretaceous climatic cooling nd isotope data obtained from biogenic apatite fish teeth and bones are presented from lower bathyal and abyssal sites in the south atlantic and indian oceans during the mid cretaceous relatively radiogenic nd isotope values suggest that deep water circulation in these basins was sluggish with inputs likely dominated by seawater particle exchange processes and possibly easily weathered volcanic terranes in the campanian maastrichtian the nd isotopic composition of proto indian and south atlantic deep waters became less radiogenic suggesting the onset of deep water formation in the southern ocean southern component water scw consistent with paleogene reconstructions and ocean circulation models a combination of southern hemisphere cooling and the opening of tectonic gateways during the campanian likely drove the onset of scw

diagenetic constraints on the use of cerium anomalies as palaeoseawater redox proxies an isotopic and ree study of cambrian phosphorites seawater rare earth element ree distributions show heavy ree enrichment and cerium depletion but these characteristics are only rarely found in ancient marine authigenic minerals such as carbonate fluorapatite and calcite this enigma may be due to changing ree distributions in seawater through time or to post depositional redistribution of ree differentiating between these two factors is however far from straightforward as their relative importance is likely to vary and evidence is often ambiguous in this article we present ree as well as strontium and sulphur isotope data for basal cambrian phosphorites of south china which confirm the emerging rule of thumb that granular phosphorites seldom reveal extreme departures from the seawater norm and tend to undergo therefore less diagenetic alteration of ree spectra than skeletal apatites and other phosphate types this study reveals stratigraphic trends in ce anomalies ce ce that could be taken to imply the preservation of a palaeoenvironmental signal however further investigation of our data shows that such trends in phosphorites can also be caused by post depositional alteration which tends to 1 increase ree contents 2 reverse ce depletion 3 alter eu anomalies and 4 concentrate preferentially the middle ree mree further alteration which may be due to weathering has led to hree depletion and positive la and y anomalies tetrad effect this is the first study where ceanom and phosphate bound sulphate s isotope values could be compared for one particular stratigraphic section which provides us with an additional tool for the interpretation of diagenetic redox conditions least altered phosphorites from meishucun that yield a strongly negative ceanom constrain early cambrian seawater 34s to about 33 we conclude that phosphorite ceanom primarily records variations in the local conditions of diagenesis while outlining some special cases in which diagenetic redox conditions may broadly reflect local bottom water redox conditions

extraction of nd isotopes from bulk deep sea sediments for paleoceanographic studies on cenozoic time scales abstract nd isotopes preserved in fossil fish teeth and ferromanganese crusts have become a common tool for tracking variations in water mass composition and circulation through time studies of nd isotopes extracted from pleistocene to holocene bulk sediments using hydroxylamine hydrochloride hh solution yield high resolution records of nd isotopes that can be interpreted in terms of deep water circulation but concerns about diagenesis and potential contamination of the seawater signal limit application of this technique to geologically young samples in this study we demonstrate that nd extracted from the 63 m decarbonated fraction of older ocean drilling program odp sediments using a 0 02 m hh solution produces nd isotopic ratios that are within error of values from cleaned fossil fish teeth collected from the same samples indicating that the hh extractions are robust recorders of deep sea nd isotopes this excellent correlation was achieved for 94 paired fish teeth and hh extraction samples ranging in age from the miocene to cretaceous distributed throughout the north tropical and south atlantic and composed of a range of lithologies including carbonate rich oozes chalks and black shales the strong nd signal recovered from cretaceous anoxic black shale sequences is unlikely to be associated with ferromanganese oxide coatings but may be derived from abundant phosphatic fish teeth and debris or organic matter in these samples in contrast to the deep water nd isotopic signal sr isotopes from hh extractions are often offset from seawater values suggesting that evaluation of sr isotopes is a conservative test for the integrity of nd isotopes in the hh fraction however rare earth elements ree from the hh extractions and fish teeth produce distinctive middle ree bulge patterns that may prove useful for evaluating whether the nd isotopic signal represents uncontaminated seawater alternatively a few paired hh extraction and cleaned fish teeth samples from each site of interest can be used to verify the seawater composition of the hh extractions the similarity between isotopic values for the hh extraction and fish teeth illustrates that the extensive cleaning protocol applied to fish teeth samples is not necessary in typical carbonate rich deep sea sediments

water mass circulation on demerara rise during the late cretaceous based on nd isotopes abstract circulation in the north atlantic during the late cretaceous has implications for poleward heat transport and nutrient distribution during an extreme greenhouse interval with episodes of ocean anoxia nd isotopes of fossil fish teeth and debris represent one of the few water mass tracers that can be used to reconstruct deep ocean circulation we present nd isotopic data interpreted as bottom water values for 290 samples from three ocean drilling program sites on demerara rise sites 1258 1260 and 1261 along with 102 analyses from four other north atlantic sites cape verde goban spur bermuda rise and blake nose that provide additional geographic and bathymetric control our results confirm the presence of a water mass with low end values 14 to 17 that are believed to be influenced by continental material during local water mass formation at low latitudes this demerara bottom water dbw is the primary water mass in the region from the cenomanian to coniacian and from the late campanian through early maastrichtian following a hiatus of 10 my a positive 8 end unit excursion occurs during ocean anoxic event 2 oae2 that cannot be explained by changes in weathering inputs diagenesis or magmatic sources of nd instead it appears to represent an influx of bottom waters sourced from the tethys or north atlantic this replacement of dbw during oae2 argues for decreased production of dbw or enhanced production of tethys north atlantic waters during peak greenhouse conditions from the late campanian through early maastrichtian dbw becomes the only water mass recorded at demerara rise and it appears to expand to abyssal depths at cape verde in the campanian this water mass is ultimately replaced by waters that appear to be sourced from the north atlantic starting in the late maastrichtian observed variations in circulation in the tropical north atlantic during the late cretaceous can account for extensive deposition of black shales in the region prior to the hiatus as well as local warming during a global cooling event in the maastrichtian

importance of vertical geochemical processes in controlling the oceanic profiles of dissolved rare earth elements in the northeastern indian ocean vertical profiles of dissolved rare earth elements rees were obtained in the bay of bengal and the andaman sea the ree concentrations at various depths in the bay of bengal are the highest in the indian ocean this is attributable ultimately to the large outflow of the ganges brahmaputra and irrawaddy rivers but the dissolved ree flux to surface waters alone cannot explain the large and near constant ree enrichment throughout the entire water column the underlying fan sediments serve as not a source but a sink for dissolved ree iii s absence of excess 228ra in the deep waters suggests that lateral input of dissolved rees from slope sediments is also small in these regions partial 0 3 dissolution of detrital particles which are carried by the rivers and lateral surface currents and subsequently settle through the water column appears to be a predominant source for the dissolved rees vertical profiles showing an almost linear increase with depth are common features for the light and middle rees everywhere but their concentration levels are variable from basin to basin and from element to element this suggests that their oceanic distributions respond quickly to the variation of particle flux and its ree composition through reversible exchange equilibrium with suspended and sinking particles much like the case for th the relative importance of the vertical geochemical processes of reversible scavenging over the horizontal basin scale ocean circulation with passive regeneration like nutrients decreases systematically from the light to the heavy rees using a model the mean oceanic residence times of rees in the bay of bengal are estimated to range from 37 years for ce to 140 1510 years for the strictly trivalent rees in the deep water of the andaman sea isolated from the bay of bengal by the andaman nicobar ridge maximum sill depth of 1800 m the ree concentrations are almost uniform presumably due to rapid vertical mixing the ree iii concentrations are similar to that of 1250 m depth water in the bay of bengal consistent with other oceanographic properties however the ree composition of the deep water appears to be altered slightly by preferential scavenging of the light ree iii at the bottom boundary of the basin

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

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

ree y uptake and diagenesis in recent sedimentary apatites abstract rare earth elements and yttrium ree y distribution in authigenic phases are frequently used as proxies for reconstructing past seawater conditions sedimentary apatite precipitates near the sediment water interface and is therefore capable of recording the ree y composition of the overlying water column while the overprinting of primary ree y signal during late stage diagenesis is a widely known phenomenon less is known about early diagenetic effects in this study we investigate the ree y distribution in recent sedimentary apatites found on the namibian shelf using in situ mapping by laser ablation inductively coupled plasma mass spectrometry la icp ms the namibian phosphorite deposits consist of reworked and redeposited pelletal apatitic grains ranging from miocene to pleistocene in age and pristine concretionary apatitic grains that formed during pleistocene to recent the results of this study show that the ree y signatures of pelletal and concretionary apatitic grains are different with both types showing intragranular variability and differences between grain centers and rims the ree y are concentrated in the external part of the apatitic grains forming a 10 20 m wide enrichment zone while the central parts of apatitic grains are low in ree y ree y

shear and tensile earthquakes caused by fluid injection 1 we apply rock mechanics concepts to the seismological observations in order to explain why during hydraulic injection some events display tensile and some shear deformation the presence of non shear components depends on the differential stress and the fracture orientation with respect to the 1 direction provided the slip vector is parallel to the traction we define four types of earthquakes according to the ratio of the shear and tensile components assuming a griffith failure envelope hybrid events containing both shear and tensile components can occur for fractures striking within 22 5 of 1 we argue that pure tensile fractures striking parallel to 1 are unlikely in the presence of natural fractures the low shear traction of tensile events also implies their small stress drops by applying the analysis to two different data sets soultz sous forets and cotton valley we show that different orientations of natural fractures and differential stress in the targeted formations made each region favorable for different non dc components in the injection induced seismicity

anomalies in rare earth distributions in seawater gd and tb we have measured profiles of the rare earth elements ree in atlantic and pacific ocean waters the data normalized versus shales exhibit a pronounced anomaly in gd relative to its neighbors eu and tb in the ree series such that the gd concentrations are high by 30 50 closer inspection reveals that the anomaly is made up of both elevated gd and depressed tb concentrations likely associated with solution chemistry shifts in the transition from an exactly half filled 4f electron shell anomalies in gd and tb solution complexation are also indicated by the turner whitfield dickson speciation model the overall trend of heavy ree iii enrichment in seawater and the gdtb anomaly described here tend to support scavenging as an important removal mechanism for the ree from seawater

paleoredox variations in ancient oceans recorded by rare earth elements in fossil apatite abstract rare earth element concentrations in biogenic apatite of conodonts fish debris and inarticulate brachiopods were determined in over 200 samples from cambrian to modern sediments tests for experimental bias caused by the chemicals used to separate fossils from the rock matrix and for interlaboratory interexperiment or interspecies related variations clearly show that no resolvable fractionation of ree occurs incorporation of ree in biogenic apatite of recent fish debris occurs near the sediment water interface soon after deposition and reflects characteristics of seawater the original ree signature apparently survives subsequent burial and diagenesis cerium variations in fish debris from modern environments are controlled by redox potential ce is fractionated by co precipitation with metallic oxides under oxidizing conditions this fractionation produces a negative ce anomaly ce anom in seawater that is reflected in the sedimented fish debris conversely no fractionation of ce occurs under reducing conditions resulting in ce concentrations that are normal to enriched in anoxic seawater and fish debris deposited under local or basinwide anoxic conditions extrapolation of observations of the redox control of ce anom in modern oceans to fossil apatite indicates that anoxic conditions were prevalent in lower paleozoic and lower triassic oceans whereas in the upper paleozoic the world ocean was generally oxidizing

geochemical study of vertebrate fossils from the upper cretaceous santonian csehbanya formation hungary evidence for a freshwater habitat of mosasaurs and pycnodont fish abstract the diverse vertebrate remains from the upper cretaceous freshwater settings at iharkut hungary contain two fossil groups pycnodontiformes fish and mosasauridae that are almost exclusively known from marine palaeo environments hence their appearance in alluvial sediments is very unusual trace element and isotope compositions of the remains have been analyzed to investigate the taphonomy and the ecological differences among the different fossil groups present at iharkut all examined fossils have undergone post depositional diagenetic alteration which resulted in high concentrations of ree u and fe together with almost complete homogenization of 18oco3 values similar ree patterns in different fossils suggest a common origin for all remains hence the discovered species most likely lived in the same local ecosystem despite partial diagenetic overprinting the 18opo4 values of the fossils indicate sufficient taxon specific isotopic diversity to permit some broad conclusions on the palaeo environment of the fossils in particular it is apparent that the isotopic composition of the pycnodontiformes fish and mosasauridae remains is most compatible with a freshwater palaeo habitat and incompatible with a marine palaeo environment in addition the sr concentration and isotope data indicate that the pycnodontiformes and mosasauridae likely lived predominantly in a freshwater environment and were not simply occasional visitors to the iharkut river ecosystem regarding other fossil groups high 18opo4 values of alligatoroidea and iharkutosuchus teeth suggest that these small crocodile species might have inhabited swamps and ponds where the water was relatively rich in 18o due to evaporation

the effect of diagenesis and fluid migration on rare earth element distribution in pore fluids of the northern cascadia accretionary margin analytical challenges in obtaining high quality measurements of rare earth elements rees from small pore fluid volumes have limited the application of rees as deep fluid geochemical tracers using a recently developed analytical technique we analyzed rees from pore fluids collected from sites u1325 and u1329 drilled on the northern cascadia margin during the integrated ocean drilling program iodp expedition 311 to investigate the ree behavior during diagenesis and their utility as tracers of deep fluid migration these sites were selected because they represent contrasting settings on an accretionary margin a ponded basin at the toe of the margin and the landward tofino basin near the shelf s edge ree concentrations of pore fluid in the methanogenic zone at sites u1325 and u1329 correlate positively with concentrations of dissolved organic carbon doc and alkalinity fractionations across the ree series are driven by preferential complexation of the heavy rees simultaneous enrichment of diagenetic indicators doc and alkalinity and of rees in particular the heavy elements ho to lu suggests that the heavy rees are released during particulate organic carbon poc degradation and are subsequently chelated by doc ree concentrations are greater at site u1325 a site where shorter residence times of poc in sulfate bearing redox zones may enhance ree burial efficiency within sulfidic and methanogenic sediment zones where ree release ensues cross plots of la concentrations versus cl li and sr delineate a distinct field for the deep fluids z 75 mbsf at site u1329 and indicate the presence of a fluid not observed at the other sites drilled on the cascadia margin changes in ree patterns the presence of a positive eu anomaly and other available geochemical data for this site suggest a complex hydrology and possible interaction with the igneous crescent terrane located east of the drilled transect

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

composition and structural features of two permian parareptile deltavjatia vjatkensis kotelnich site russia bone fragments and their alteration during fossilisation abstract the kotelnich vertebrate fossil site one of the richest of the permian period is characterised by the excellent preservation of fossil remains due to their burial in a silty anaerobic environment similar to modern peat bogs the aim of the work is to carry out a comprehensive study of the composition and structure of bone fragments of the permian parareptile deltavjatia vjatkensis as well as that of its embedding rocks to support further paleoecological and fossilisation reconstructions fossil bones and their surrounding strata were investigated using optical and scanning electron microscopy raman spectroscopy x ray diffraction and inductively coupled plasma mass spectrometry icp ms the carbonate rich composition of the sediment was found to favour the preservation of the bone apatite the mineral phase of the bone tissue corresponds to fluorapatite organic matrix vibration bands arising on the raman spectra correspond to c h vibrations of lipids and proteins and possibly cholesterol the obtained data indicate a high degree of integrity of both bone mineral phase and its organic proteinaceous residue white blood cell wbc like structures were detected which possibly could be interpreted as leukocytes elemental mapping of fossil bones was used to reveal element distribution features uniform or with zones of apparent enrichment depletion and secondary mineralisation zones ca p mg mn and s are uniformly distributed through the bone conversely elevated quantities of fe are assigned to cracks and large pores formed as a consequence of the decomposition of organic materials as compared to bone apatite the authigenic calcite filling of bone porosities is significantly depleted in terms of microelements the apatite rare earth element ree composition of bone tissue which is inherited from seawater can be used for paleoreconstructions of redox conditions and water composition la sm ratios 0 4 0 5 high y ho ratios high uranium content and high la yb ratios 2 3 in the bone apatite indicate the absence of recrystallisation during the late stages of diagenesis a positive cerium anomaly detected in the bones indicates the presence of an oxidising and possibly alkaline environment during the early stages of diagenesis in shallow coastal basin of the kotelnich paleolocality it is shown that 10 to 20 of ree in bone apatite is derived from seawater absorption hydrogenous source with the remainder having been derived from host rock lithogenic sources

evolution of atlantic thermohaline circulation early oligocene onset of deep water production in the north atlantic the flow of deep water masses is a key component of heat transport in the modern climate system yet the role of deep ocean heat transport during periods of extreme warmth is poorly understood the present mode of meridional overturning circulation is characterized by deep water formation in both the north atlantic and the southern ocean however a different mode of meridional overturning circulation operated during the extreme greenhouse warmth of the early cenozoic during which time the southern ocean was the dominant region of deep water formation the combination of general global cooling and tectonic evolution of the atlantic basins over the past 55 m y ultimately led to the development of a mode of overturning circulation characterized by both southern ocean and north atlantic deep water sources the change in deep water circulation mode may in turn have affected global climate however unraveling the causes and consequences of this transition requires a better understanding of the timing of the transition new nd isotope data from the southeastern atlantic ocean indicate that the initial transition to a bipolar mode of deep water circulation occurred in the early oligocene ca 33 ma the likely cause of significant deep water production in the north atlantic was tectonic deepening of the sill separating the greenland norwegian sea from the north atlantic

la icp ms analysis of rare earth elements in marine reptile bones from the middle triassic bonebed upper silesia s poland impact of long lasting diagenesis and factors controlling the uptake abstract the rare earth elements ree contained in fossil bones are widely used for provenance and palaeoenvironmental studies earlier works suggested that the ree uptake is limited to early diagenesis but more recent research provided evidence of long term open system diffusion in fossil bones we analysed thin walled reptile bones all collected from the same middle triassic 245 ma marine bonebed comprising vertebrate remains of likely different ages to check the influence of the long term diagenesis on the concentrations of ree in terms of impact of pore water the upper parts of the bones are contained in a low permeability crinoidal limestone whereas their lower parts have been affected by diagenetic fluids for a long time we measured ree and other trace element contents in 29 bones using la icp ms totally 660 spots in 45 depth profiles neither the absolute concentrations of the ree and the ree intra bone paas normalised patterns nor the inter element ratios and the la ce and eu anomalies appear useful to distinguish between the likely older and younger bones in the bonebed the mree n enrichment combined with the flat intra bone distributions of the ree lead to conclusion that ree fractionation and substitution for ca were the most important processes responsible for the selective uptake the low permeability host rock and diagenetic fluids had a significant impact on the trace element uptake and their intra bone distribution patterns the lower parts of the bones that likely had a long lasting contact with the diagenetic fluids reveal a relative enrichment in the ree and their easier diffusion into the bone centres the ability of fossil bones to incorporate trace elements over a long time span strongly limits the usage of particularly the older samples for provenance and palaeoenvironmental reconstructions additionally the presented new analyses fill the gap between the available databases of trace element concentrations in fossil bones with regard to middle triassic samples

comprehensive stable isotope investigation of marine biogenic apatite from the late cretaceous early eocene phosphate series of morocco fossil biogenic apatites were studied for their geochemical composition across the late cretaceous early eocene moroccan phosphate series in the ouled abdoun and ganntour basins in morocco in order to characterize paleoenvironmental conditions and to improve stratigraphy the vertebrate remains show particularly good structural mineralogical and chemical preservations which relate to the favorable depositional environment of the phosphorite the main studied fossils shark tooth enameloid and dentine and coprolites show large range in 13c values from 14 to 6 which can be coupled to different carbon sources enameloid yielded mostly positive 13c isotopic compositions that are comparable with values reported from modern teeth coprolites have the lowest 13c values that reflect burial conditions with intensive organic matter recycling the large variation in 18opo4 values of the shark teeth can be related to ecological differences however the mean 18opo4 data reflect important temporal variation along the series together with the corresponding average 13c values comparisons with the global isotope records allow identifying the early eocene climatic optimum in the top of the ouled abdoun series above bed 0 the isotope data further suggest a sedimentary gap during the latest thanetian and the paleocene eocene thermal maximum the top of the paleocene series bed iia can be dated to late selandian early thanetian with the recognition of the early late paleocene event elpe the eritherium bone bed that yielded the earliest known placental mammals from africa would be located below the elpe and therefore cannot be younger than late selandian the isotope data from the older paleocene bed iib and cretaceous upper bed iii beds in the ouled abdoun basin can be correlated with the latest danian early selandian and the latest maastrichtian global isotope record respectively based on the 18opo4 data the cretaceous layers of the ganntour basin cover most of the maastrichtian period except the very early part all these early paleogene and cretaceous chemostratigraphic ages however need further confirmations from other proxies yet the interpretations are in general agreement with the biostratigraphy derived from the selachian fauna

rare earth elements and sr and nd isotopic compositions of dissolved and suspended loads from small river systems in the vosges mountains france the river rhine and groundwater abstract the aim of this study is to characterize the evolution of the rare earth elements ree in non mature streams from small catchment areas in the vosges mountains downstream to more mature plain rivers including the river rhine the dissolved load ree distribution patterns of the low ph vosges streams are very different from those of high ph plain rivers indicating that different physico chemical parameters control ree transport in these different water systems the plain rivers and groundwater show similar ree distribution patterns with a strong negative ce anomaly and heavy rare earth element hree enrichment in addition the river rhine has a positive gd anomaly which is of anthropogenic origin similar to the world s major rivers the light rare earth element lree enrichment in the plain rivers is mainly ph controlled their sm nd and 143 nd 144 nd isotope ratios are close to average continental crust values this is not the case for the less evolved non mature and low ph vosges streams their high sm nd and 143 nd 144 nd ratios but low 87 sr 86 sr ratios suggest that chemical alteration of accessory middle rare earth element mree enriched minerals such as apatites from rocks in the catchment area control the ree abundances of these waters a comparison of the dissolved load ree distribution patterns with those of the principal lithologies in the corresponding drainage basins illustrates that especially the eu anomalies of the vosges streamlets are strongly lithology dependent leaching experiments indicate that the suspended load is isotopically very inhomogeneous the ree distribution patterns of the suspended load leachates have no similarities with those of the corresponding dissolved load indicating that the leachable reservoir not only contains adsorbed ree but also ree from leachable mineral phases their 143 nd 144 nd sm nd and 87 sr 86 sr ratios support this suggestion being always higher and lower respectively than those of their corresponding dissolved loads they rather point to the presence of relic primary apatite in the leachable portion of the suspended load the flat paas normalized ree distribution patterns the high 87 sr 86 sr and low 143 nd 144 nd isotopic ratios of the corresponding residues suggest secondary silicate phases such as clay minerals in the residual phase of the suspended load leachates and corresponding residual phases define alignments in the sm nd isochron diagram whose slopes define ages ranging between 200 and 390 ma indicating that the mineral phases in the suspended load retain some memory of their primary precursor minerals in the hercynian granitic source rocks

geochemical evidence from bio apatite for multiple oceanic anoxic events during permian triassic transition and the link with end permian extinction and recovery abstract a detailed 20 myr redox history of permian to triassic oceans changhsingian to carnian stages has been constructed using ce anomaly ce and th u ratios from conodont albid crown apatite material the results show that the well established phenomenon of intense ocean anoxia coincident with the end permian mass extinction is faithfully recorded in conodont ce and th u data extending this conodont redox record shows that end permian anoxia persisted possibly into the earliest dienerian stage and that two intense oceanic anoxic events also occurred later in the early triassic earliest smithian earliest spathian and middle spathian followed by a weaker manifestation of anoxia in the anisian stage seen in ce data marine benthic radiation following the end permian mass extinction began after the smithian earliest spathian anoxic event suggesting a suppression of evolution prior to this due to these inimical conditions the failure of the middle spathian anoxic event to retard the evolutionary rebound implies shallow shelf seas remained well ventilated at this time even if the oceans did not other attributes of the early triassic record also closely coincide with redox fluctuations phases of anoxia intensification saw the proliferation of microbial carbonates and major negative carbon isotope swings that can be attributed to chemocline shallowing causing alkalinity pulses and enrichment in light remineralised carbon and or indicate a trigger meachnaims related to increased fluxes of light c from siberian volcanic sources

rare earth elements and stable isotope geochemistry δ13c and δ18o of phosphorite deposits in the gafsa basin tunisia rare earth elements ree and stable isotope compositions 13c and 18o of shark teeth and phosphatic coprolites were analyzed from the lower maastrichtian layers of the el haria formation and two sequences of the paleocene eocene p e chouabine formation in the gafsa basin south western of tunisia in order to trace the sedimentological climatic and oceanographic conditions the ree chemistry and their distribution in the two archives are the same for each of the studied layers indicating that the coprolites and shark teeth experienced the same early diagenetic environments however major differences occur between the maastrichtian and the p e reflecting changes in the depositional conditions the early maastrichtian burial environment tended to be more anoxic with ree derived from reduced feo while in the p e the ree patterns mimic the modern oxic suboxic seawater the ree source from remineralisation of organic coating could have more significance the oxygen isotope compositions of the structural phosphates 18opo4 indicate a stable and warm climate during both studied time intervals a small offset 0 4 in the 18o value between the coprolites and shark teeth show minor thermal gradient between bottom and surface water the pronounced negative shift of 3 4 in 13c values recorded in the upper part of the chouabine formation was ascribed to the paleocene eocene boundary at the same time the lack of negative change in the 18o is explained by the semi closed situation of the gafsa basin which situation also played an important role in the evolution of the organic matters in the sediment resulting in the exceptional low 13c values

migration of sharks into freshwater systems during the miocene and implications for alpine paleoelevation trace element and isotopic compositions of fossilized shark teeth sampled from miocene marine sediments of the north alpine molasse basin the vienna basin and the pannonian basin generally show evidence of formation in a marine environment under conditions geochemically equivalent to the open ocean in contrast two of eight shark teeth from the swiss upper marine molasse locality of la moliere have extremely low 18o values 10 3 and 11 3 and low 87sr 86sr ratios 0 707840 and 0 707812 compared to other teeth from this locality 21 1 22 4 and 0 708421 0 708630 the rare earth element ree abundances and patterns from la moliere not only differ between dentine and enameloid of the same tooth but also between different teeth supporting variable conditions of diagenesis at this site however the ree patterns of enameloid from the exotic teeth analyzed for o and sr isotopic compositions are similar to those of teeth that have o and sr isotopic compositions typical of a marine setting at this site collectively this suggests that the two exotic teeth were formed while the sharks frequented a freshwater environment with very low 18o content and sr isotopic composition controlled by mesozoic calcareous rocks this is consistent with a paleogeography of high elevation 2300 m miocene alps adjacent to a marginal sea

uranium oxidation state and related variations in geochemistry of phosphorites from the negev southern israel abstract study of the u iv fraction in mishash phosphorites of the negev reveals an apparently paradoxical trend the u iv fraction is very low less than 10 in the pristine organic rich laminated phosphorites while this proportion considerably increases up to 60 in the recycled mechanically reworked granular phosphorites which deposited under more oxidizing conditions this u iv trend seems to differ from that reported in other phosphate sequences elsewhere and is also quite unexpected in view of the sediment patterns and the specific formational conditions of the two phosphorite facies in addition a lower u iv in the analyzed granular phosphorites is coupled with a lower rare earth elements ree p 2 o 5 and y p 2 o 5 ratio a higher cd and zn concentration less negative ce ce ce and eu eu eu anomalies a lower hree dy er enrichment and a lower f p 2 o 5 and higher co 2 f ratio in francolites this u iv trend in the two negev phosphorite facies may be explained by varying time spans of apatite growth changes in sediment burial rates and principally different residence times of the phosphate fraction in the suboxic apatite forming diagenetic zone near the sediment water interface the associated varying concentrations of rees y cd and zn in phosphorites and of f and co 2 in francolites in the two granular phosphorite facies are apparently collectively regulated by the same sedimentary dynamics during phosphate deposition it is presumed that the u iv trend observed in the negev phosphorites could be detected in other phosphate sequences as well if pristine phosphorites are carefully identified and selectively analyzed

rare earth elements in pore waters of marine sediments abstract the rare earth elements rees were measured in pore waters of the upper 25 cm of sediment from one site off peru and three sites on the california margin the pore water ree concentrations are higher than sea water and show systematic down core variations in both concentration and normalized pattern from these analyses and from comparison to other chemical species measured dissolved fe mn ba oxygen nitrate phosphate it is suggested that pore water rees can be grouped into three categories those that are from an fe source those that are from a poc source and cerium oxide rees from the fe source appear where anoxia is reached they have a distinctive middle ree mree enriched pattern the concentrations in this source are so elevated that they dominate ree trends in the fe oxide reduction zone the net result of flux from the poc source is relative enrichment of heavy rees hrees over light rees lrees reflecting remineralizing poc and complexation with doc a common linear ree pattern seen in both oxic and anoxic sediments is associated with this poc source as well as a hree enriched pattern that is seen in surficial sediments at the peru site overall the pore water results indicate that mn oxides are not an important carrier of rees in the oceans a ree biogeochemical model is presented which attempts to reconcile ree behavior in the water and sediment columns of the oceans the model proposes that poc fe oxide and ce oxide sources can explain the ree concentration profiles and relative abundance patterns in environments ranging from oxic sea water to anoxic pore water the model is also consistent with our observation that the ce anomaly of pore water does not exceed unity under any redox condition

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

tracing papua new guinea imprint on the central equatorial pacific ocean using neodymium isotopic compositions and rare earth element patterns abstract the nd isotopic composition ic and rare earth patterns of hydrodynamic structures of the equatorial pacific ocean were characterized along 140 w the nd ic of antarctic intermediate water aaiw and of the lower layer of the equatorial undercurrent euc at 140 w 13 c water are much more radiogenic at the equator than at their origin in the south equatorial current 12 s revealing that these water masses have been in contact with the highly radiogenic papua new guinea png slope in both cases only a small fraction less than 9 of the sediment deposited on the png slope is required to be exchanged or dissolved to explain these nd ic variations whereas the hydrographic properties of the same water masses remain unchanged this confirms the usefulness of this tracer to identify pathways of water masses these results emphasize the importance of jets in transporting lithogenic material into the subsurface layers of remote areas where aeolian inputs are particularly weak and corroborate the previous results on fe and al maximum in this area m l wells g k vallis e a silver nature 398 1999 601 604 the nd ic of the upper layer of the euc contrasts strongly to that of the subpycnocline layer indicating that the equatorial upwelling only affects the surface waters and is not effective between 120 and 150 m we calculate that the nd imprint of the png input is likely to vanish from this surface layer as it traverses the basin due to the replacement of upwelled waters by non radiogenic ones

constraints on miocene oceanography and climate in the western and central paratethys o sr and nd isotope compositions of marine fish and mammal remains abstract the paratethys evolved as a marginal sea during the alpine himalayan orogeny in the oligo miocene sediments from the northern alpine molasse basin the vienna and the pannonian basins located in the western and central part of the paratethys thus provide unique information on regional changes in climate and oceanography during a period of active alpine uplift oxygen isotope compositions of well preserved phosphatic fossils recovered from the sediments support deposition under sub tropical to warm temperate climate with water temperatures of 14 to 28 c for the miocene 18o values of fossil shark teeth are similar to those reported for other miocene marine sections and using the best available estimates of their biostratigraphic age show a variation until the end of the badenian similar to that reported for composite global record the 87sr 86sr isotope ratios of the fossils follow the global miocene seawater trend albeit with a much larger scatter the deviations of 87sr 86sr in the samples from the well constrained seawater curve are interpreted as due to local input of terrestrially derived sr contribution of local sources is also reflected in the end values consistent with input from ancient crystalline rocks e g bohemian massif and or mesozoic sediments with end 7 excluding samples showing local influence on the water column an average end value of 7 9 0 5 may be inferred for the miocene paratethys this value is indistinguishable from the end value of the contemporaneous indian ocean supporting a dominant role of this ocean in the western and central paratethys

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

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

investigating the source characteristics of long period lp seismic events recorded on piton de la fournaise volcano la reunion abstract magmatic and hydrothermal processes play a significant role in generating seismicity at active volcanoes these signals can be recorded at the surface and can be used to obtain an insight into the volcano s internal dynamics long period lp events are of particular interest as they often accompany or precede volcanic eruptions but they are still not well understood piton de la fournaise volcano la reunion island is one of the most active volcanoes in the world however lp events are rarely recorded there a seismic network of 20 broadband seismometers has been operational on piton de la fournaise volcano since november 2009 between november 2009 and january 2011 the volcano erupted five times but only 15 lp events were recorded three of these eruptions were preceded by lp events and several lp events were recorded during an intrusive phase a family of three repeating lp events exists within the dataset in order to characterize these events we locate and perform moment tensor inversion on the lp family the lp events are located within the summit crater at shallow depths

mesozoic palaeoceanography of the north atlantic and tethys oceans summary the biogeography and preservation of calcareous nannofossil assemblages allow mapping of surface water fertility patterns and put constraints on carbonate dissolution in the global oceans of the middle cretaceous cyclic changes in carbonate dissolution and surface water biologic productivity in the cretaceous oceans were linked to oceanographic and climatic changes that had frequencies close to the milankovitch cycles tens of thousands to hundreds of thousand years evolution of calcareous nannoplankton during the jurassic and cretaceous periods occurred in two primary cycles of about 75 ma duration that were punctuated by major diversification events occurring every 15 30 ma that marked the beginning of periods of increased marine organic matter production and preservation stagnation events calcareous nannoplankton evolved largely in shallow seas during the rhaetian to kimmeridgian in the latest jurassic calcareous nannoplankton conquered the oceanic realm became major producers of pelagic carbonates and are thus responsible for the shift of carbonate deposition from shallow seas to the deep ocean in the late cretaceous chalk seas nannofossils replaced shallow water benthos as major carbonate producers warm climates due to high atmospheric co 2 concentrations and increased albedo during high sea level stands caused by global tectonic processes made these tiny creatures flourish during the late mesozoic

the geochemical balance of the rare earth elements and neodymium isotopes in the oceans profiles of ree concentrations and neodymium isotope measurements in the western indian ocean are consistent with published data from the other major oceans ree concentrations show a strong hydrographic control the influence of intermediate water masses is particularly significant surface water concentrations vary with salinity paniculate rees are less than 5 of dissolved concentration except for ce where up to 20 of total rees are present as 0 4 m particles in contrast to dissolved profiles concentration profiles of paniculate rees including ce all increase with depth ree concentrations correlate with silica over all but the deepest waters although in detail correlations are complex the neodymium isotopic composition of indian ocean seawater avg nd 0 8 3 is intermediate between that for the atlantic and pacific oceans comparison of ree data from the major oceans shows that the hrees behave more like si than do the lrees sm nd ratios are near constant for all oceans whereas ernd ratios vary between the atlantic indian and pacific oceans the fractionation of the rees in surface seawaters can be explained by fractionation factors relative to silica from 0 12 for la to 0 05 for er use of a seven box model shows that the interoceanic variations in neodymium isotopic compositions and nd concentrations cannot be reconciled unless particle water exchange is invoked the degree of exchange required is consistent with particle residence times of 1 10 yr

cerium a chemical tracer for paleo oceanic redox conditions abstract the ce anomalies found in marine carbonates provide a sensitive indicator for the study of paleo oceanic redox conditions the dependency of cce the observed ce concentration and cepo04 the activity of the cepo4 complex to the po2 ph and pco2 of seawater can be used for deciphering some aspects of the paleo ocean chemistry and is log c ce log cepo 0 4 13 2 0 25 log p o 2 3 0 ph 1 95 0 25 log p o 2 1 50 log p co 2 1 50 log ca the ph which is related to pco2 and po2 are major factors for controlling the ce concentration in seawater therefore ce anomalies ceas ce observed ce interpolated between la and pr or nd serve as indicators for ph or pco2 or po2 changes nearly uniform ce abundances found in pacific 5000 m water columns piepgras and jacobsen 1988 and the ceas in ichthyoliths can be explained using this model a general cea shift in sediments from d s d p holes 525a 530a b 516 516f suggest that the entire south atlantic water redox condition changed from reducing to oxidizing at 56 my in the north atlantic the galicia margin samples show a redox change between 132 148 my indicating active surface currents between the atlantic ocean and the shallow sea off the iberian peninsula the carbonate samples from d s d p hole 316 in the central pacific yielded an average cea of 0 15 0 01 which is 2 3 the ceas observed in deep pacific seawater by piepgras and jacobsen 1988 the relative enrichment of ce in these samples is ascribed to coprecipitation of ce oh 4 onto fe mn o coatings the striking similarities in the trace element profiles of ree sc hf th and ceas and the low u abundances 0 08 ppm in many marine carbonates indicate insignificant ce redox and trace elemental concentration changes for the pacific ocean over the past 95 my no significant ce redox change occurred in the pacific ocean within k t boundary one 240 my china limestone deposited under oxic sedimentary conditions yielded a cea of 0 53 calculations indicate a pco2 of 1 9 present value prevailed over the 240 my tethyan ocean u th ratios and low u concentrations are diagnostic indicators for obtaining reliable ceas in marine carbonates and perhaps for biogenic apatites and conodonts as well

geochemical taphonomy of shallow marine vertebrate assemblages abstract combined histological and geochemical analyses demonstrate complex processes leading to preservation of microbially altered bone in certain situations a chemical microenvironment distinct from surrounding pore waters is developed and maintained within the bone the bone acts as a closed system and hence palaeoenvironmental interpretations based on fossil bone apatite chemistry may not accurately reflect overall geochemical conditions of the sedimentary deposits where the bones were buried geochemical techniques based on variance in trace element compositions of bones from different assemblages can be used as a measure of the relative degree of mixing or taphonomic averaging within marine vertebrate assemblages

gradual changes in upwelled seawater conditions redox ph from the late cretaceous through early paleogene at the northwest coast of africa negative ce anomaly trend recorded in fossil bio apatite abstract marine vertebrate fossils from late cretaceous early paleogene shallow marine phosphorites of morocco were investigated for their trace element compositions and neodymium isotopic ratios in order to constrain marine and depositional conditions the various analyzed fossils are separated into two groups with different geochemical compositions 1 shark tooth enameloid with generally lower cu ba rare earth elements rees and u and higher na zn and sr concentrations than 2 dentine bone and coprolites these differences are related to the originally different structures of these fossils all the fossils revealed very similar shale normalized ree patterns with negative ce anomaly and heavy ree enrichment mimicking the ree pattern of modern oxic seawater the results therefore suggest ree uptake by the fossils from an early diagenetic pore fluid that was dominated by seawater importantly the ce anomaly does not vary among the different types of fossil remains and the values are very similar in a given layer moreover a step wise shift towards lower ce ce values from older to younger beds is apparent nd isotope analyses across the phosphorite succession yielded minor variation with an average end t value of 6 2 0 4 n 12 indicating no major changes in the ree source during the studied interval the relatively radiogenic values reflect tethyan connection and or important contribution of a mafic nd source from weathering in the region the age related trend in the ce anomaly is interpreted to be due to changes in redox and or ph conditions of the upwelling seawater on the shallow shelf areas the driving force of these changes was probably an extended global oceanic circulation especially enhanced connection and water exchange between the north and south atlantic

first carbon isotope chemostratigraphy of the ouled abdoun phosphate basin morocco implications for dating and evolution of earliest african placental mammals abstract the well known maastrichtian ypresian vertebrate bearing phosphate series in the ouled abdoun basin morocco is classically dated using regional selachian biostratigraphic zonation these marine sediments yielded paleocene and eocene mammals comprising the earliest known placentals from africa this study provides the first insight into the organic carbon isotope chemostratigraphy 13 c org of the moroccan phosphate series and a refined dating of its vertebrate bearing levels four paleocene eocene sections in the ne ouled abdoun quarries show consistent 13 c org long term evolutions from the base to the top 1 positive trend in phosphorite bed iia beginning with the lower bone bed yielding mammals such as eritherium ocepeia abdounodus lahimia of early thanetian and selandian age 2 transitional negative trend in the intercalary phosphorite beds ii i that includes the otodus obliquus and phosphatherium escuilliei bone bed of earliest ypresian age 3 negative trend to the lowermost 13 c org values that are correlative to the early middle ypresian interval including etm 2 and etm 3 hyperthermal events in the global record 4 positive trend in chert enriched facies containing the middle ypresian eeco global climatic event our chemostratigraphic study of the ouled abdoun phosphate series provides a new chronostratigraphic framework for calibrating the beginning of the evolution of placental mammals in africa the lower bone bed level from the paleocene phosphorite bed iia yielding eritherium is not younger than early thanetian and is most likely selandian the phosphatherium bone bed in the intercalary beds ii i is earliest ypresian the phosphorite bed 0 from which daouitherium probably came is early middle ypresian just below the eeco this suggests that the first large proboscideans evolved after the petm during mid ypresian warming events the 13 c org study does not support the presence of lutetian in the ne ouled abdoun phosphate series and suggests that a noticeable part of the upper thanetian is absent

long period seismic source characterization at popocatepetl volcano mexico 1 the seismicity of popocatepetl is dominated by long period and very long period signals associated with hydrothermal processes and magmatic degassing we model the source mechanism of repetitive long period signals in the 0 4 2 s band from a 15 station broadband network by stacking long period events with similar waveforms to improve the signal to noise ratio the data are well fitted by a point source located within the summit crater 250 m below the crater floor and 200 m from the inferred magma conduit the inferred source includes a volumetric component that can be modeled as resonance of a horizontal steam filled crack and a vertical single force component the long period events are thought to be related to the interaction between the magmatic system and a perched hydrothermal system repetitive injection of fluid into the horizontal fracture and subsequent sudden discharge when a critical pressure threshold is met provides a non destructive source process

evolution of tethyan phosphogenesis along the northern edges of the arabian african shield during the cretaceous eocene as deduced from temporal variations of ca and nd isotopes and rates of p accumulation abstract the evolution of tethyan phosphogenesis during the cretaceous eocene is examined to try to explain fluctuations of phosphogenesis through time and whether or not they reflect long term changes in ocean circulation or in continental weathering twenty seven time stratigraphic phosphate levels in various tethyan sites covering a time span of about 90 myr from the hauterivian to the eocene were analyzed for 44 ca 42 ca and 143 nd 144 nd in their carbonate fluorapatite cfa fraction p and ca accumulation rates and bulk sedimentation rates were quantified throughout the cretaceous eocene negev sequence to examine how changes in 44 ca 42 ca and 143 nd 144 nd are reflected in the intensity of phosphogenesis a clear cut change occurs in e nd t and 44 ca and in the rates of p and ca accumulation and bulk sedimentation through the time analyzed e nd t is much lower in the hauterivian lower cenomanian 12 8 to 10 9 than in the upper cenomanian eocene 7 8 to 5 9 much lower 44 ca values occur in the hauterivian turonian 0 22 to 0 02 than in the coniacian eocene 0 23 to 0 40 p accumulation rates in the negev steeply increase from 2 k yr 1 in the albian coniacian to 1500 mol cm 2 k yr 1 in the campanian whereas a strong decrease is concomitantly recorded in the rates of ca accumulation and bulk sedimentation in addition distinct e nd t values are shown by the phosphorites of the negev 6 7 to 6 4 and egypt 9 1 to 7 6 during the campanian and by those of the negev 7 8 to 6 3 and north africa 10 1 to 8 9 during the maastrichtian eocene the culmination of p accumulation rates in the negev during the campanian occurring with a high in e nd t and 44 ca and a low in sedimentation rates indicates that paleoceanographic and paleogeographical factors mostly governed phosphorite accumulation in this area the abrupt e nd t rise after the cenomanian is attributed to increased incursion of pacific radiogenic water masses into the tethys driven by the late cretaceous global sea level rise the connection between north and south atlantic the global post santonian cooling and the progressive widening of the caribbean threshold all acting in combination to significantly intensify the tethyan circumglobal current tcc it also reflects a weakening of the continental nd signal due to a reduction of exposed landmasses caused by increased flooding of continental shelves high 44 ca values at those times also point to a decrease in weathering ca 2 fluxes and expansion of carbonate sedimentation in shelves both enriching seawater with isotopically heavy ca 2 deep ocean circulation intensified by the post santonian cooling of high latitudes increased p inventory in the tethys basin whereas the strengthened tcc and the folded shelf likely resulted in coastal and topographically induced upwelling supplying p rich intermediate waters to southeastern tethys shelves only in the paleocene eocene following major changes in global circulation produced by narrowing of tethys and widening of the atlantic did phosphogenesis shifts its locus of high intensity to the western atlantic tethys and west african atlantic coasts this change in paleocirculation is expressed by distinctly differing e nd t in the middle east and the north and west african phosphorites suggesting different oceanic p sources and current systems for these two major groups of phosphorites our nd isotope results further suggest a weaker tcc during the mid cretaceous becoming more intense in late cretaceous times they also point to the north pacific ocean as major source of deep water formation for the intermediate deep waters in the tethys basin during the late cretaceous

satellite based evidence for a large hydrothermal system at piton de la fournaise volcano reunion island 1 hydrothermal systems are active structures present at many volcanoes their characterization is essential as they reveal the evolution of the magmatic source and may play a role in the eruptive style many studies have already suggested the existence of a shallow hydrothermal system beneath the summit craters at piton de la fournaise volcano la reunion although there is still no clear evidence here we present new arguments on the basis of satellite based data acquired during april 2007 eruption suggesting the existence of a large hydrothermal system beneath the dolomieu crater at piton de la fournaise so2 released during the collapse phase of the dolomieu crater april 6 13 has been estimated at 935 244 kilotons whereas erupted so2 calculated from lava effusion rates was found to be clearly insufficient 179 89 kilotons we suggest that the excess of so2 originated from a large hydrothermal system suddenly opened by the collapse

lu hf isotope systematics of fossil biogenic apatite and their effects on geochronology abstract reliable methods for direct dating of biogenic apatite from pre pleistocene fossils are currently not available and recent attempts using the lu hf decay system yielded highly inaccurate ages for both bones and teeth the geological processes accounting for this poor accuracy of lu hf chronometry are not yet understood here we explore lu hf systematics in fossil bones and teeth in detail by applying five different sample digestion techniques that are tested on bones and composites of bone and sediment our current dataset implies that dissolution methods only slightly affect the resulting lu hf ages while clear differences between the individual digestion techniques became apparent for element concentrations by analysing the insoluble leftovers from incomplete sample dissolution four main reservoirs of hf in fossil bones were identified 1 a radiogenic end member associated with apatite 2 an unradiogenic end member represented by the authigenic minerals or the embedding sediment 3 a highly unradiogenic end member that can be attributed to detrital zircon and 4 a moderately soluble phase probably a zr hf phosphate that yielded very low lu hf but a highly radiogenic hf isotope composition at the same time this zr hf phase must have been precipitated within the fossil bone sample at a late stage of burial history thereby incorporating radiogenic 176 hf released from apatite surfaces over geological timescales a second focus of our study is the effect of different sediment matrices and of crystal size on the preservation of pristine lu hf isotope compositions in bioapatite because near depositional lu hf ages of phosphate fossils have previously been reported for the london clay england and a calcareous marl from tendaguru tanzania we herein investigate specimens fossilised in carbonate matrices calcareous marl from oker germany carbonate concretions from the santana formation brazil carbonate from the eifel germany and argillaceous matrices with low permeability oil shale of messel germany posidonienschiefer of holzmaden germany materials analysed from these localities include bones teeth conodonts as well as coproliths and diagenetic minerals siderite montgomeryite and messelite near depositional lu hf ages were obtained for a bony fish sample notelops brama encapsulated in an early diagenetic carbonate concretion from the early cretaceous santana formation brazil and for conodonts from a middle devonian carbonate from the eifel germany low 176 lu 177 hf ratios in all materials from the middle eocene messel oil shale e g bones fish scales sediment siderite result in poor age precision and an age that is near depositional due to this large analytical error in agreement with previous results all other ages determined here for both bones and teeth are by far younger than respective chronostratigraphic ages a model illustrating the behaviour of lu and hf over time with respect to the fossilisation process is presented which accounts both for the formation of a late diagenetic radiogenic zr hf phase and long term open system behaviour the continuous lu hf element exchange between the fossils and the embedding sediment is probably related to the nm scale crystal size of fossil bones dentine and also of enamel that generate large surface areas facilitating sorption desorption processes and open system behaviour

preservation of seawater sr and nd isotopes in fossil fish teeth bad news and good news abstract we analyzed 87sr 86sr ratios in foraminifera pore fluids and fish teeth for samples ranging in age from eocene to pleistocene from four ocean drilling program sites distributed around the globe site 1090 in the cape basin of the southern ocean site 757 on the ninetyeast ridge in the indian ocean site 807 on the ontong java plateau in the western equatorial pacific and site 689 on the maud rise in the southern ocean sr isotopic ratios for dated foraminifera consistently plot on the global seawater sr isotope curve for sites 1090 757 and 807 sr isotopic values of the pore fluids are generally less radiogenic than contemporaneous seawater values as are values for fossil fish teeth in contrast pore fluid 87sr 86sr values at site 689 are more radiogenic than contemporaneous seawater and the corresponding fish teeth also record more radiogenic values thus sr isotopic values preserved in fossil fish teeth are consistently altered in the direction of the pore fluid values furthermore there is a correlation between the magnitude of the offset between the pore fluids and the seawater curve and the associated offset between the fish teeth and the seawater curve these data suggest that the hydroxyfluorapatite of the fossil fish teeth continues to recrystallize and exchange sr with its surroundings during burial and diagenesis therefore sr chemostratigraphy can be used to determine rough ages for fossil fish teeth in these cores but cannot be used to fine tune age models in contrast to the sr isotopic system our nd concentration data combined with published isotopic and rare earth element data suggest that fish teeth acquire nd during early diagenesis while they are still in direct contact with seawater the concentrations of nd acquired at this stage are extremely high relative to the concentrations in surrounding pore fluids as a result nd isotopes are not altered during burial and later diagenesis therefore fossil fish teeth from a variety of marine environments preserve a reliable and robust record of deep seawater nd isotopic compositions from the time of deposition

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

paleoenvironmental conditions and strontium isotope stratigraphy in the paleogene gafsa basin tunisia deduced from geochemical analyses of phosphatic fossils fossil shark teeth and coprolites from three major phosphorite occurrences in the gafsa basin southwestern tunisia were investigated for their geochemical compositions to improve local stratigraphy and to better assess paleoenvironmental conditions 87sr 86sr isotope ratios of shark teeth from the early maastrichtian el haria formation and from the early eocene metlaoui s s formation yielded sr isotope ages of 68 1 and 47 9 1 3 ma respectively which accord with the expected stratigraphic positions of these sediments conversely shark teeth from the paleocene eocene chouabine formation have large variation in sr isotope ratios even within individual layers after statistical treatment and then elimination of certain outlier samples three age models are proposed and discussed the most reasonable solution includes three subsequent sr ages of 61 8 2 2 ma 57 2 1 8 and 54 6 1 6 for layer ix layers viii v and layers iv 0 respectively three scenarios are discussed for explanation of the presence of the outliers 1 diagenesis 2 re working and 3 locally controlled seawater sr isotope ratio the most plausible account for the higher 87sr 86sr ratios relative to the global ocean in some fossils is enhanced intrabasinal re working due to low sea level conversely the sample with lower 87sr 86sr than the global seawater may link to diagenesis or to seawater influenced by weathering of late cretaceous marine carbonates which latter is supported by model calculation as well the end values of these fossils are very similar to those reported for paleogene and late cretaceous tethyan seawater and are compatible with the above interpretations the relatively low oxygen isotope values in shark teeth from the topmost phosphate bed of the chouabine formation together with the sr isotope results point toward recovering better connections with the open sea these 18o data reflect elevated ambient temperature which may link to the early eocene climatic optimum

nd isotope evidence for the evolution of the paleocurrents in the atlantic and tethys oceans during the past 180 ma the nd isotopic composition of atlantic and tethys seawater as deduced from marine phosphorites varied considerably during the past 180 ma the early tethys and central atlantic seawater from 180 to 160 ma ago early middle jurassic had a nd isotopic signature identical to that of the pacific end 6 suggesting that pacific seawater entered the newly forming tethys basin however with time continental runoff draining into the young basin became more important and led to a decrease in the nd isotopic composition and finally a decoupling from the pacific ocean during the late early cretaceous 120 90 ma ago atlantic and tethys seawater reached continental crust like nd isotopic composition values end 10 which could reflect high weathering rates induced by the warm and humid climate at that time in the time span between 80 and 50 ma late cretaceous early tertiary the nd isotopic composition of both tethys and atlantic seawater strongly increased towards pacific seawater values in the case of the atlantic ocean this change has been correlated with the opening of the south atlantic which enabled the more radiogenic pacific seawater to travel westwards around the southern edge of africa into the south and finally the north atlantic in the case of tethys seawater we have to assume that during this period large masses of pacific seawater entered the tethys again directly through the indian tethys seaway the renewed importance of this seaway might be related to the late cretaceous early tertiary first order global sea level highstand the most abrupt change towards lower more crust like values occurred in the early miocene 25 17 ma ago in the south and north atlantic as well as in the tethys during this period the143nd 144nd isotope ratios dropped from 0 5124 end 4 2 down to 0 5122 end 8 this change indicates a diminishing influx of pacif seawater into the atlantic and tethys oceans and can be correlated with the breakdown of the circum equatorial circulation patterns of the world oceans due to plate tectonics from 20 to 17 ma ago miocene the nd isotopic composition of the atlantic ocean increased again and reached values as high as 0 5123 end 6 6 whereas tethys seawater remained at low values this decoupling can be correlated with the incipient complete isolation of the tethys the nd isotopic composition was henceforth controlled by the continental runoff from surrounding land masses the major increase in the nd isotopic composition observed in the atlantic can be related to the opening of the drake passage and establishment of the circum antarctic current system this allowed pacific seawater to enter directly the south atlantic around antarctica a renewed drop in the nd isotopic composition of atlantic seawater during the late miocene can be related to the onset of north atlantic bottom water formation and its subsequent upwelling

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