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

comparing oxygen isotope records of silurian calcite and phosphate δ18o compositions of brachiopods and conodonts oxygen isotope compositions of silurian calcitic brachiopod shells from gotland are compared with those of phosphatic inarticulate brachiopod shells and conodonts from identical stratigraphic horizons the 18ophosphate values of inarticulate brachiopod shells vary widely 13 0 to 17 5 v smow and are significantly lower than those of coeval conodont samples 17 5 to 19 5 v smow conodont samples from individual beds have homogenous 18ophosphate values with variations close to the analytical precision 0 2 together with a significant correlation of conodont 18ophosphate and articulate brachiopod shell 18ocarbonate values r 0 85 this observation suggests that primary marine oxygen isotope compositions are better preserved in conodont apatite than in inarticulate brachiopod shell apatite however with decreasing 18ocarbonate values the 18ophosphate values of conodonts are higher than expected for theoretical isotopic equilibrium with brachiopod calcite different habitats of conodonts and brachiopods cannot account for the observed offset in 18o because both organisms were thriving on a broad shallow marine carbonate platform whereas 18ophosphate values of silurian conodonts are close to 18ophosphate values of modern and mesozoic tropical biogenic apatites most silurian calcitic brachiopod shells from gotland are depleted in 18o when compared to modern or mesozoic brachiopods we therefore suggest that silurian conodonts from gotland record paleotemperature and 18o of silurian sea water more faithfully than coeval calcitic brachiopod shells

geochemical compositions of neogene phosphatic brachiopods implications for ancient environmental and marine conditions abstract isotopic and trace element compositions of miocene and pliocene phosphatic brachiopods lingulidae and discinidae from southern north sea the central paratethys and the atlantic coast of europe were investigated in order to trace past environmental conditions and marine connections between the northern boreal and the southern subtropical tropical marine basins the north sea genus glottidia yielded low e nd and high 18 o po4 values through the mio pliocene indicating cold habitat temperature where the local seawater was dominated by the atlantic ocean in contrast the middle miocene lingulidae and discinidae of the paratethys inhabited warm subtropical seawater with the possible influence of the indian ocean via the mediterranean as supported by their average e nd value of 8 3 the combined geochemical data support a thermal and marine separation of the paratethys from the north sea with no direct connection or major exchange of water from the miocene onwards the temperature in the paratethys was very similar to that inferred from brachiopods from the middle miocene of western france but the seawater e nd value here is identical to that of contemporaneous atlantic ocean a late miocene lingulid brachiopod from southern portugal has a high 18 o po4 similar to the specimens investigated from the north sea reflecting either a deep water habitat or formation after the onset of major global cooling that resulted in an increased 18 o value of seawater the e nd value of 8 4 for this site is compatible with an influence of mediterranean outflow

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

pliocene dinoflagellate cyst stratigraphy palaeoecology and sequence stratigraphy of the tunnel canal dock belgium dinoflagellate cysts and sequence stratigraphy are used to date accurately the tunnel canal dock section which contains the most complete record of marine pliocene deposits in the antwerp harbour area the zanclean kattendijk formation was deposited between 5 0 and 4 4 ma during warm temperate conditions on a shelf influenced by open marine waters the overlying lillo formation is divided into four members the lowest is the luchtbal sands member estimated to have been deposited between 3 71 and 3 21 ma under cooler conditions but with an open water influence the oorderen sands kruisschans sands and merksem sands members of the lillo formation are considered a single depositional sequence and biostratigraphically dated between 3 71 and c 2 6 ma with the oorderen sands member no younger than 2 72 2 74 ma warm temperate conditions had returned but a cooling event is noted within the oorderen sands member shoaling of the depositional environment is also evidenced with the transgressive oorderen sands member passing upwards into near coastal high stand deposits of the kruisschans sands and merksem sands members as accommodation space decreased applying sequence stratigraphy to our section implies that the kattendijk lillo formation boundary corresponds to the sequence boundary sb za2 4 04 ma the luchtbal oorderen sands boundary to sb pia1 3 21 ma and the top of the merksem sands to sb pia2 2 76 ma finally the belgian deposits are compared with marine pliocene deposits of eastern england

high resolution dating of deep sea clays using sr isotopes in fossil fish teeth abstract strontium isotopic compostitions of ichthyoliths microscopic fish remains in deep sea clays recovered from the north pacific ocean odp holes 885a 886b and 886c are used to provide stratigraphic age control within these otherwise undatable sediments age control within the deep sea clays is crucial for determining changes in sedimentation rates and for calculating fluxes of chemical and mineral components to the sediments the sr isotopic ages are in excellent agreement with independent age datums from above diatom ooze below basalt basement and within cretaceous tertiary boundary the clay deposit the 87 sr 86 sr ratios of fish teeth from the top of the pelagic clay unit 0 708989 indicate an late miocene age 5 8 ma as do radiolarian and diatom biostratigraphic ages in the overlying diatom ooze the 87 sr 86 sr ratio 0 707887 is consistent with a cretaceous tertiary boundary age as identified by anomalously high iridium shocked quartz and sperules in hole 886c the 87 sr 86 sr ratios of pretreated fish teeth from the base of the clay unit are similar to late cretaceous seawater 0 707779 0 707519 consistent with radiometric ages from the underlying basalt of 81 ma calculation of sedimentation rates based on sr isotopic ages from hole 886c indicate an average sedimentation rate of 17 7 m myr in unit ii diatom ooze 0 55 m myr in unit iiia pelagic clay and 0 68 m myr in unit iiib distal hydrothermal precipitates the sr isotopic ages indicate a period of greatly reduced sedimentation or possible hiatus between about 35 and 65 ma eocene paleocene with a linear sedimentation rate of only 0 04 m myr the calculated sedimentation rates are generally inversely proportional to cobalt accumulation rates and ichthyolith abundances however discrepancies between sr isotope ages and cobalt accumulation ages of 10 15 myr are evident particularly in the middle of the clay unit iiia oligocene paleocene

tertiary oxygen isotope synthesis sea level history and continental margin erosion tertiary benthic and planktonic foraminiferal oxygen isotope records are correlated to a standard geomagnetic polarity time scale making use of improved chronostratigraphic control and additional oligocene isotope data synchronous changes in both benthic and planktonic 18o values which occurred in the oligocene to miocene 36 5 2 ma are interpreted in part to represent ice growth and decay the inferred ice growth events correlate with erosion on passive continental margins as interpreted from seismic and chronostratigraphic records this association is consistent with a link between oligocene to miocene erosional events and rapid 15 m m y glacioeustatic lowerings of about 50 m high benthic foraminiferal 18o values suggest the presence of continental ice sheets during much of the oligocene to recent 36 0 ma substantially ice free conditions probably existed throughout the paleocene and eocene 66 36 ma the mechanisms and rates of sea level change apparently were different between the early and late tertiary with glacioeustatic changes restricted to the past 36 m y pre oligocene erosion on passive continental margins was caused by eustatic lowerings resulting from global spreading rate changes we apply a model which suggests that large areas of the continental shelves were subaerially exposed during such tectonoeustatic lowstands stimulating slope failure and submarine erosion the different mechanisms and rates of eustatic change may have caused contrasting erosional patterns between the early and late tertiary on passive continental margins this speculation needs to be confirmed by examination of data from several passive margins

isotopic composition of recent shark teeth as a proxy for environmental conditions abstract the o c and sr isotope compositions of teeth from ten species belonging to five families and three orders of sharks were measured to determine the influence of habitat diet and possible species specific fractionation effects on the isotopic composition of biogenic phosphate from fish the sharks were recently caught in subtropical waters off the kwazulu natal kzn coast of south africa as well as from cold waters in prince william sound pws alaska and victor bay vb nunavut canada 18 o values of tooth phosphate 18 o p range from 20 9 to 23 5 for the kzn sharks for most species the range in measured 18 o p values is about 0 6 but it may be as high as 1 1 for different teeth from a single shark dentine and enameloid within individual teeth have no apparent differences in 18 o p values the 18 o p values of the kzn shark teeth reflect the typical habitat of the studied species primarily the thermal structure of the water column off kzn at depths between 20 and 280 m the 18 o p values of teeth from different greenland sharks from vb and pacific sleeper sharks from pws are very homogeneous averaging 25 8 and 24 7 respectively these values appear to be in equilibrium with deep 500 m ocean waters in each case at temperatures of about 0 3 c or less there is little discernable evidence for species specific fractionation effects for the oxygen isotope composition of phosphate in the studied marine fish the oxygen isotope composition of carbonate in apatite averages about 9 1 higher than corresponding 18 o p values in agreement with equilibrium fractionation between carbonate and phosphate but with a large variance 1 1 5 18 o c values also vary by up to 1 between enameloid and dentine within single teeth but in a non systematic way differences in 13 c values between carbonate in enameloid and dentine is also large up to 8 but the 13 c values vary systematically enameloid is always enriched in 13 c compared to dentine and the 13 c content increases with developmental stage of the teeth 13 c values measured for enameloid 1 6 to 4 8 appear to approach equilibrium with dissolved inorganic carbon in seawater in contrast 13 c values for dentine range from 6 4 to 2 3 for kzn sharks and 9 0 to 10 8 for the cold water sleeper sharks and are compatible with a predominantly dietary carbon source the 87 sr 86 sr ratios of teeth from kzn sharks as well as those from pws and vb are uniform averaging 0 709167 sr content varies from 1270 to 2100 ppm a range that is similar to that in well preserved fossilized teeth seawater sr is thus clearly incorporated in vivo concentrations of sm and nd are in the ppb range and contrast the ppm range in fossilized teeth indicating a postmortem incorporation of rare earth elements in apatite of the teeth

dinosaur bones fossils or pseudomorphs the pitfalls of physiology reconstruction from apatitic fossils abstract a prerequisite to any attempt to reconstruct thermophysiology of ancient animals through analysis of stable isotopes of oxygen is the assumption that apatitic fossils are isotopically unaltered parts of their original skeletons we suggest that sufficient evidence is available to seriously question this assumption because living bones contain about 1 3 by weight of organic matrix mass balance considerations show that at least half of an apatitic fossil must be new material added post mortem furthermore living apatitic skeletons contain almost no rare earth elements and uranium whereas apatitic fossils bear high concentrations of these elements additionally we found that while in living fish correlation between 18o of oxygen in the phosphate and that in the carbonate of apatite is poor these two values are linearly correlated in fossil fish this suggests diagenetic recrystallization has taken place perfect preservation of micro textures such as haversian canals does not prove the pristine condition of a fossil some of the most beautifully preserved fossils are highly silicified most apatitic fossils probably are pseudomorphs replacing original skeletal elements whereas distribution of stable isotopes of oxygen in fossils might provide information about their burial environment it could be misleading in attempts to interpret the organisms physiology this cautionary note is supported by the similarity of 18op in bones of coexisting fossil fish dinosaurs and various other reptiles at different latitudes the overlap of predicted 18op values in fish and mammals living in contact with the same environmental water also weakens the hope that ectotherms can be distinguished from endotherms by the isotopic composition of oxygen in their bones and teeth

design and operation of a portable digital impulse radar we have constructed a back portable impulse radar instrument that weighs roughly 12 kg can be powered by dry cells and records and stores data digitally the radar is controlled by an on board purpose built microcomputer that ensures simple field operation facilitates modifications and allows unattended operation when investigating time varying targets the transmitting unit is triggered from the receiver via an optical link and generates an electromagnetic wavelet by discharging two high voltage capacitors through back to back silicon controlled rectifiers into a resistively loaded dipole antenna successful field operations carried out during the summers of 1986 and 1987 include depth profiling as well as studies of englacial and subglacial targets on several temperate and sub polar glaciers

oxygen isotope analyses of co existing carbonate and phosphate in biogenic apatite a way to monitor diagenetic alteration of bone phosphate abstract the oxygen isotopic composition of phosphate 18 op and structural carbonate 18 oc of hydroxylapatite was determined in 31 bone and tooth samples of modern mammals from different countries these two variables are highly correlate r 2 0 98 and the calculated best fit of linear regression is very similar to the equation calculated from the phosphate and carbonate palaeotemperature equations 1 2 according to previous measurements 3 6 on fossils of different ages from different areas it seems quite improbable to find isotopically altered skeletal remains showing a good correlation between 18 op and 18 oc as is the case with modern samples it therefore seems possible at least in some cases to use these measurements for monitoring fossil bone and tooth diagenetic alteration when a set of points lie on the equilibrium line or close to it the 18 o values could be considered close to the original values in contrast when the points lie to the left or to the right of this line this probably means that the values are diagenetically modified due to interaction with meteoric water or 18 o enriched water respectively

oxygen isotope variations in phosphate of biogenic apatites i fish bone apatite rechecking the rules of the game abstract the major advantage of the oxygen in phosphate isotope paleothermometry is that it is a system which records temperatures with great sensitivity while bone and teeth building organisms are alive and the record is nearly perfectly preserved after death fish from seven water bodies of different temperatures 3 23 c and different 18 o values 16 to 3 of the water were analysed the 18 o values of the analysed po 4 vary from 6 to 25 the system passed the following tests a the temperatures deduced from isotopic analyses of the sequence of fish from lake baikal are in good agreement with the temperatures measured in the thermally stratified lake b the isotopic composition of fish bone phosphate is not influenced by the isotopic composition of the phosphate which is fed to the fish but only by temperature and water composition isotopic analysis of fossil fish in combination with analysis of mammal bones should be a useful tool in deciphering continental paleoclimates

actual timing of neodymium isotopic variations recorded by femn crusts in the western north atlantic hydrogenetic ferromanganese femn crusts from the western north atlantic record variations in the nd and pb isotopic composition of cenozoic deep water preserved during their growth the timing and cause of the most striking change have been the subject of debate some have proposed that the shift took place after 4 ma in response to the closure of the panama gateway others have argued that the major change in isotope composition occurred as early as 8 ma this study presents high resolution nd isotope records for crusts previously dated using 10be 9be chronology these data confirm that the shifts in nd occurred after 4 ma consistent with a likely relationship with the closure of the central american isthmus and intensification of northern hemisphere glaciation and in accordance with changes seen in other physical and chemical records these results illustrate the need for both a robust chronological framework and high resolution records before a reliable paleoceanographic interpretation can be made of the variations recorded by femn crusts

punctuated evolution of global climate cooling during the late middle to early late miocene high resolution planktonic foraminiferal and oxygen isotope records from the mediterranean high resolution planktonic foraminiferal and oxygen isotope records are presented from a mediterranean deep marine succession dated astronomically between 12 12 and 9 78 ma planktonic and benthic oxygen isotope records are punctuated by two episodes of 18o increase which have astronomical ages of 11 4 and 10 4 ma and correspond to the mi5 and mi6 events of miller et al 1991a these ice growth events coincide with low amplitude variations in the 1 2 myr obliquity cycle and are accompanied by significant faunal changes in the mediterranean such as the arrival of neogloboquadrinids the increase in abundance of the g apertura g obliquus group and the areal differentiation between n atlantica and n acostaensis short term variations in the planktonic foraminiferal and oxygen isotope records correspond to dominantly precession controlled sedimentary cycles features of the sapropel grey marl layers indicate that the short term astronomically controlled circum mediterranean climate changes remained basically the same over the last 12 myr

holocene evolution of the canet st nazaire lagoon golfe du lion france as determined from a study of sediment properties the sedimentation in the lagoons of the golfe du lion coast mediterranean sea france records their post holocene evolution the canet st nazaire lagoon provides an example of such an evolution eight cores ranging from 13 5 to 19 7 m in length from a transect of the lagoon provide a cross section of the late quaternary stratigraphy the sedimentary sequence comprises mud and sand layers the two sand formations are identified as parts of two distinct shelf sedimentary prisms stratigraphic analysis defines three stages in the recent muddy infilling corresponding to the last divisions of the holocene sedimentation rates of the muds related to climatic and palaeogeomorphological events largely determine their geotechnical and geochemical properties it appears indeed to be the most important factor in determining the compressibility index the saturated bulk density and the organic and water contents of the deposits subboreal muds poorly consolidated and rich in organic matter correspond to a high rate of deposition in the subatlantic muds in contrast the sedimentation rate is lower whilst there is a decrease in the organic matter and an increase in the degree of cohesion

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

δ18o and ree contents of phosphatic brachiopods a comparison between modern and lower paleozoic populations 18o values of both carbonate 18 7 25 1 and phosphate 15 1 16 7 components of the francolite from the fossil brachiopod shells are interpreted as the result of a partial resetting of pristine isotopic compositions the similarity of hat shape ree patterns of some lower ordovician linguloids with those of extant littoral specimens suggests the preservation of a 500 myr old record of ree marine chemistry in agreement with the known paleogeography the phosphatic brachiopods have been deposited in a coastal environment under shallow and oxygenated marine waters however the contents and distribution of ree in some strongly altered brachiopod shells reveal an alteration of the original negative ce anomalies and both nd and sm enrichments that transformed the initial hat shape patterns of linguloids into strongly convex or bell shape patterns

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

determination of oxygen isotope fractionation between water and phosphate from living lingulids potential application to palaeoenvironmental studies abstract lingulids are inarticulate brachiopods with phosphatic shells which live exclusively in marine waters their distribution is generally restricted to the continental shelf within the 40 belt from temperate to equatorial areas they show a range of morphological physiological and behavioral features that have remained remarkably constant since the cambrian the oxygen isotope fractionation between water and phosphate from living lingulids was determined as a tool to investigate the temperature and or salinity of past coastal seawater oxygen isotope measurements were performed according to the silver phosphate method on a collection of lingulids coming from well known and varied marine environments a global 18o variation of 3 5 was found for these lingulids which proves their good sensitivity to environmental factors namely the oxygen isotope composition and the temperature of seawater oceanographic data provided average temperature and salinity values in the living sites of the studied specimens least squares treatment of the data gave the following fractionation equation t c 112 2 15 3 4 20 0 71 18o po4 18o h2o which is similar to the equations determined by longinelli and nuti 1973a and kolodny et al 1983 for other phosphate bearing invertebrates and fishes all these results suggest that a unique equation describes the phosphate water fractionation of many marine organisms except for mammals

oceanographic and climatic evolution of the miocene mediterranean deduced from nd sr c and o isotope compositions of marine fossils and sediments isotopic compositions of marine sediments and fossils have been investigated from northern basins of the mediterranean to help constrain local oceanographic and climatic changes adjacent to the uplifting alps stable c and o isotope compositions of benthic and planktonic foraminifera from the umbria marche region umc have an offset characteristic for their habitats and the changes in composition mimic global changes suggesting that the regional conditions of climate and the carbon cycle were controlled by global changes the radiogenic isotope composition of these fossil assemblages allows recognition of three distinct periods in the first period from 25 to 19 ma high nd values and low 87sr 86sr of sediments and fossils support intense tectonism and volcanism related to the opening of the western mediterranean in the second period from 19 to 13 ma the 87sr 86sr ratio of mediterranean umc deviate from the global ocean which is compatible with rapid uplift of the hinterland and intense influx of sr from mesozoic carbonates of the western apennines this local control on the seawater was driven by a humid and warm climate and indicates restricted exchange of water with the global ocean generally the nd values of the fossils are very similar to those of indian ocean water with brief periods of a decrease in the nd values coinciding with volcanic events and maybe sea level variation at 15 2 ma in the third period from 13 to 10 ma the fossils have 87sr 86sr similar to those of miocene seawater while their nd values change considerably with time this indicates fluctuating influence of the atlantic versus the paratethys and or locally evolved seawater in the mediterranean driven by global sea level changes other investigated localities near the alps and from the odp 900 site are compatible with this oceanographic interpretation however in the late early miocene enhanced local control reflecting erosion of old crustal silicate rocks near the alps results in higher 87sr 86sr

high resolution analysis of δ18o in the biogenic phosphate of modern and fossil lingulid brachiopods abstract laser ablation and silver phosphate procedures were used to measure the oxygen isotope composition in organophosphatic shells of lingulid brachiopods at a variety of scales within valves between valves from the same individual between individuals collected at the same location at the same time between localities and between modern and fossil specimens specimens included modern lingulids from several patches in the northern gulf of california mexico and the gulf of nicoya costa rica and fossil specimens from the lower triassic dinwoody formation all specimens display a high degree of intrashell variability frequently exceeding 4 this variability is not symmetrical within the shell does not appear to reflect growth bands and is not consistent with a published lingulid phosphate oxygen isotope thermometer shells analyzed using silver phosphate preparations have variability similar 3 5 to that of shells analyzed using the laser ablation technique ruling out the influence of org

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

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

deciphering temperature and salinity from biogenic phosphates the δ18o of coexisting fishes and mammals of the middle miocene sea of western france abstract this study examines the possibility of estimating the oxygen isotopic composition and temperature of seawater by using a combination of 18o values of phosphate from coexisting fishes and mammals of the middle miocene sea of western france teeth of different species of teleosteans and selachians and rib fragments of metaxytherium medium related to modern dugongs were sampled in the langhian seravallian calcareous sediments of eastern brittany and touraine 18o values of fishes range from 21 4 to 22 7 while those of mammals range from 20 1 to 21 7 the variability in 18o values of miocene fishes is not related either to sampling localities or taxa oxygen isotope analyses were also carried out on living dugong dugon from djibouti 18 o 19 6 20 3 and on hydrodamalis gigas which lived two hundred years ago in the low salinity waters of the bering strait 18 o 17 3 the results show that the slope of the oxygen isotope fractionation curve between the dugongids and water is probably close to 1 18o variations within miocene fish and mammal populations are similar and close to or slightly higher than 1 this variation may be attributed mainly to a 18o change in the ambient seawater composition the miocene shallow water masses in western france were thus characterized by varying 18o values as well as average salinities equal to or higher than the contemporaneous open world ocean calculated average temperatures of 20 2 c are compatible with a sub tropical climate local and global causes for this variation in the oxygen isotope composition of miocene seawater are discussed