contemporary changes in sediment yield in an alpine mountain basin due to afforestation the upper drome in france abstract the baurieres plain within the upper drome river basin was used to reconstruct recent changes in sediment supply in relation to changes in land use within an alpine catchment a considerable body of archival information is available furthermore the plain acts as a natural sediment trap and the reach basin interaction has not been disrupted by human activity based on archival data channel geometry measurements dendrogeomorphological and radionuclide analysis cs137 and unsupported pb210 the trends in channel change and sediment supply over the past two centuries are assessed and their causes are interpreted dendrogeomorphology and radionuclide profiles show that the floodplain is characterised by a decrease in sedimentation rate in the 1960s the ex pb210 profiles also suggest a spatial modification of the relative contribution in sediment supply of the catchment bedload yields are estimated to be at least 26 m3 km 2 year 1 between 1928 and 1996 based on an estimate of storage over a channel length of 11 5 km archival data concerning bedload removal from traps yields an estimate of 25 6 m3 km 2 year 1 between 1993 and 2001 these two values are very comparable suggesting no major modification in bedload transport within the reach during the 20th century if the bedload supply has not strongly decreased in the studied reach during this period the bedload sources have changed the volume of sediment stored in the beaurieres area between 1928 and 1996 corresponds to at least 40 of the sediment delivered by channel degradation from an upstream alluvial reach both changes in floodplain sedimentation as well as changes in bedload and suspended contributions from catchment sources are interpreted as responses to land use but also flow regime hillslope sediment production strongly decreased due to planned hillslope afforestation and torrent regulation at the end of the 19th century and spontaneous hillslope afforestation resulting from grazing decline mainly in the two decades following world war ii the observed change in suspended sediment supply which occurred around 1960 1965 has a clear synchronicity with spontaneous catchment afforestation following world war ii after this period a decrease in sediment supply a change in source but also a decrease in peak flow were observed changes in run off are complex and cannot be caused with only land use change flood hydrographs underwent peak decreases and duration increases through the 20th century because of increase in water retention capacity of the forested catchment in addition flood seasonality has changed with september and october flood events being much less frequent in the last part of the 20th century

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

crystallinity and diagenesis of sedimentary apatites the crystallinity of sedimentary apatites was determined by fourier transform infrared spectroscopy ft ir using the splitting of a triply degenerate antisymmetric bending vibration of orthophosphate the crystallinity indices of recent marine apatites are low 3 0 3 6 while those of onland ancient apatites are high 4 5 7 8 indicating post depositional recrystallization the infrared spectra reveal that recrystallization is associated with a decrease in carbonate content substituting for po43 and an increase in fluoride order within the apatite structure the relationship between the crystallinity index and po43 18o suggests alteration of the primary isotopic composition by exchange reactions between po43 oxygens and surrounding waters the monterey samples have a large range of crystallinity index that reflects a set of complex and highly variable diagenetic conditions this demonstrates the use of ft ir criteria for differentiating between pristine and altered apatites and as a consequence for relating geochemical markers to formation or diagenetic environments it is suggested that only those samples that have low crystallinity indices c i 3 8 should be considered as pristine apatite spectra of fish remains indicate that differences in rare earth element ree patterns correspond to variations in crystallinity carbonate content and f order in the apatite lattice the fact that crystallinity is not correlated with geologic age suggests that environmental factors such as accumulation rate and pore water chemistry govern the recrystallization process in general sr content decreases and 18op exhibits high variability with increasing crystallinity

chemistry microstructure petrology and diagenetic model of jurassic dinosaur bones dinosaur national monument utah abstract the fossil bone mineral in dinosaurs from the morrison formation is well crystallized stoichiometric francolite the closely packed subparallel francolite crystals have equidimensional cross sections mostly 10 40 nm wide in contrast crystallites in unaltered mammal bone tissue are poorly crystallized nonstoichiometric carbonate hydroxyapatite a few nanometers thick and plate rod or needle shaped the diagenetic francolite crystals are elongated in the c axis direction as are bone tissue crystallites along permeable cracks francolite crystals grew to 250 nm wide compared to unaltered crystallites in mammal bones the francolite has higher concentrations of ba ce cr f la mn ni pb rb sr th u v and y and perhaps zr na and mg are lower in concentration diagene ic francolite grew from groundwater enriched in ions from silicic ashes in the brushy basin member and from dissolution of bone tissue crystallites after burial francolite grew on crystallite seeds filling the space formerly occupied by collagen perhaps half the tissue volume and dissolved crystallites the micron scale structures such as haversian canals and laminae are preserved because the diagenetic francolite retains the orientations of the seeds the laminae 1 10 m thick commonly preserve an orthogonal plywood structure the diagenetic growth of francolite during this type of bone fossilization implies that oxygen isotopic ratios measured in dinosaur bones even those that appear fresh and unaltered may dominantly reflect groundwater temperature rather than dinosaur body temperature trace element concentrations in the francolite may reflect groundwater composition rather than dinosaur diet pore filling cements precipitated in the sands and bones at shallow burial depths as evidenced by the 35 52 minus cement porosities of the sandstones and numerous uncompacted oversize pores filled by cements gypsum and calcite were precipitated from shallow alkaline groundwater as the groundwater became increasingly dominated by ions from silicic ash argentite chalcopyrite native gold native silver tiemannite and uraninite replaced areas of bone a few microns to tens of microns in size along cracks a thin chlorite crust commonly mantled francolite crystals along bone cracks and lined openings in bones and sandstones pervasive precipitation of a chalcedony crust followed with pseudomorphs of chalcedony after gypsum in larger cancellous openings the remaining space was fi led by the various forms of silica the bones are brown due to goethite filled cracks that cut pore filling minerals

the effect of diagenesis on oxygen isotope ratios of biogenic phosphates the effect of diagenesis on the oxygen isotope composition of ancient biogenic phosphates was evaluated by measuring different types of material from middle triassic localities in the southern alps dentin bone and tooth enamel of different taxa hosted by different rock types and metamorphosed to differing degrees were analyzed for their 18 o and 13 c values using a new microanalytical gc irmms technique the 18 o values of the majority of bone and bulk tooth samples were 18 to 19 permil smow with three samples below this range and one close to 20 permil in contrast samples of tooth enamel were 19 4 to 20 7 permil significantly higher than bone and bulk tooth without the enamel data the 18 to 19 permil data could be misinterpreted as primary only when the higher 18 o values of the enamel are considered is it apparent that the bulk data have undergone diagenesis and temperature estimates are 5 c lower than would otherwise be calculated alteration of bulk tooth is also seen in a miocene shark tooth where 18 o values of enamel are 3 permil higher than those of bulk tooth although enamel is routinely analyzed for paleoclimate work of herbivorous mammals bulk bone teeth or shells are almost exclusively used for older marine samples the results of the present study indicate that bulk data should be treated with caution

physical properties geochemistry and diagenesis of xenarthran teeth prospects for interpreting the paleoecology of extinct species abstract xenarthrans also called edentates include modern armadillos sloths and numerous extinct clades e g glyptodonts and ground sloths that lack enamel on their teeth in contrast to mammals with tooth enamel which oftentimes preserves geochemical proxy data paleoecological interpretations of xenarthrans based on geochemical analyses e g stable isotopes have been limited xenarthrans have evolved a distinctive outer dentine layer that seems to be the functional analog of enamel here we evaluate the physical and chemical properties of xenarthran outer dentine to understand its potential use for investigating geochemical proxies the mean hardness h of xenarthran outer dentine 3 8 is significantly less than that of enamel 5 7 and there is no difference in h between the two main groups i e armadillos cingulates and pilosans sloths although the mean h does not change significantly during diagenesis its range increases indicating the replacement of secondary minerals e g carbonate representing the lower range within the original hydroxylapatite mineral lattice results of ft ir analyses indicate that xenarthran outer dentine has a high degree of organics and h2o similar to normal dentine and its crystallinity index and carbonate content are affected in varying degrees during diagenesis thus although xenarthran outer dentine functions like enamel it retains compositional similarities to dentine the uptake of rare earth elements ree was analyzed from three late neogene localities in florida as a proxy for understanding diagenesis in xenarthrans as compared to other mammals relative to modern specimens the fossils have about two orders of magnitude higher concentrations of ree uptake rates vary significantly among different dental tissues i e bone dentine both inner and outer enamel ree concentrations of fossil vertebrate specimens vary significantly between different localities the ree index ratio of outer dentine bone or enamel bone for a given specimen is proposed here to evaluate relative diagenesis in xenarthrans and other mammals respectively other non xenarthran mammals tend to have a lower ree index interpreted to represent less diagenesis nevertheless many xenarthrans likewise have a low ree index relative to other mammals at the same locality indicating a similar degree of diagenesis while the ree index will likely be a reliable indicator of relative diagenesis in xenarthrans the outer dentine provides challenges to the ultimate goal of interpreting proxy geochemical e g stable isotope data from these extinct mammals

the retention of primary oxygen isotope compositions of fossil elephant skeletal phosphate fossil elephant remains from sediments of plio pleistocene age in the vicinity of lake turkana kenya provide insights into the ability of the phosphate oxygen system to preserve original 18o values 18op in the depositional environment individual fossil specimens exhibit systematic variations in the 18op values of their various tooth and bone components differences in 18op values between these skeletal components can be as high as 3 6 despite the fact that equivalent phases for individual modern elephants have 18op values which vary by less than 0 6 xrd traces of the different skeletal phases of modern and fossil samples also infer differential preservation of primary apatite crystallinities among the various fossil phases fossil samples of dentine cementum and bone have x ray spectra with sharper and more intense peaks compared to their modern counterparts but little change in crystallinity is observed for fossil enamel samples a model based on the premise that the enamel phase preserves primary isotope signatures and that the accompanying skeletal phases are partially re equilibrated with the fluids associated with the microbial decomposition of the elephant s carcass is consistent with the features of the 18op dataset this isotopic evidence in conjunction with the physical and chemical attributes of enamel has led us to postulate that enamel could be preserving primary isotope signatures while other skeletal components are affected to varying degrees by alteration processes in the burial environment

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

diagenetic effects on the oxygen isotope composition of bones of dinosaurs and other vertebrates recovered from terrestrial and marine sediments assessing effects of diagenesis on oxygen isotope composition of bone is essential to its use in reconstructing habitats and lifestyles of ancient vertebrates these effects are a matter of controversy particularly in the case of extinct animals such as dinosaurs to investigate the effects of diagenesis on isotopic composition of fossil bone bone samples from both marine and terrestrial campanian sediments from alberta canada have been analysed the isotopic compositions of oxygen 18 o smow were determined in bones sampled from articulated skeletons of exclusively terrestrial animals recovered from the terrestrial dinosaur park formation and compared with bones from the marine bearpaw formation the articulated skeleton of an exclusively terrestrial dinosaur hadrosaur found in marine sediments yielded similar 18 o values for both structural carbonate and phosphate fractions mean 18 o smow values 22 6 and 16 9 respectively in bone to marine reptiles mosasaurs recovered from the same locality mean 18 o smow values 24 2 and 17 3 respectively the isotopic composition of both skeletons recovered from marine sediments was significantly more positive than that of articulated hadrosaur skeletons recovered from contemporaneous terrestrial sediments mean phosphate 18 o smow value 12 9 and outside the range of phosphate 18 o smow values previously reported for terrestrial dinosaur skeletons c 9 14 these data suggest that the isotopic composition of oxygen in the phosphate and structural carbonate ions in the bone apatite was altered during diagenesis and can be used for neither palaeoclimate nor physiological reconstruction

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

the isotopic composition and diagenesis of human bone from teotihuacan and oaxaca mexico we analyzed archaeological human bone from teotihuacan and oaxaca dating from about 300 bc to 750 ad to distinguish ethnic groups within teotihuacan using oxygen isotopes sixty eight analyses of bone phosphate 6180 were made of 64 individuals in addition to oxygen isotopic analysis the bones were examined using ftir spectra with some additional dnaa and icp ms analyses little change occurs in the bone apatite until the amount of collagen as combustible organics has been reduced considerably when the bone becomes softer and ftir crystallinity increases the 6180 of the phosphate p appears to be unaltered even after extensive diagenesis and probably solution on ftir plots the relative area of the carbonate peak to the main phosphate peak decreases with diagenetic level the bones absorb some metals rapidly after burial for example uranium which then leach out as diagenesis of the bone apatite progresses other metallic elements increase irregularly in concentration as alteration proceeds

early diagenetic evolution of bone phosphate an x ray diffractometry analysis abstract a new crystallinity index ci based on the x ray powder diffractometric pattern of fossil bone carbonate hydroxylapatite is defined this ci value provides a semi quantitative way to estimate the diagenetic changes in archaeological and palaeontological bone phosphate the studied samples are 71 human bones from the french merovingian cemetery of saint linaire 1200 1700 bp 37 human bones from two necropoleis in niger 1000 5000 bp two cave bear bones from aldene cave southern france around 70 000 bp five bones of miocene mammals and 14 bones of mesozoic reptiles the main results are that 1 there is no correlation between the increase in the ci and the age of the sample even in one given locality 2 the ci seems to be related to the taphonomical conditions in archaeological and fossil bones 3 an increase in the ci is correlated with a loss in organic matter in one archaeological site but the quality of preservation of organic matter in fossil bones does not depend on the changes in the ci 4 the correlation between the increase in the ci and the decrease of co3amount in bones from the niger necropolies suggests a possible mechanism for the increase in crystallinity the changes of crystallinity reflect early diagenetic changes and depend on the burial environments

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

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

modelling of the oxygen isotope evolution of seawater implications for the climate interpretation of the δ18o of marine sediments it is often argued that the 18o value of oceanic water was maintained close to 0 for hundreds of millions of years as a consequence of oxygen isotope exchange between oceanic crust and seawater however for several decades the interpretation of the biosedimentary oxygen isotope record has conflicted with the igneous record because with increasing age a general trend of decreasing 18o values about 6 is observed in most carbonates cherts and phosphates especially for the paleozoic and early mesozoic we developed a dynamical model of seawater crust interaction that computes the 18o value in these two reservoirs as function of time this model takes into account the continuous production of crust at oceanic ridges its expansion rate the permeability profile with space and time the mineralogical mode of the crust and the kinetics of oxygen isotope exchange between rock forming minerals and seawater the model indicates that the 18o value of seawater may vary by 2 with a time response ranging from 5 to 50 ma for expansion rates of 1 to 10 cm a 1 the variation of 2 is fixed by both integrated water rock ratio and closure time of the seawater crust system by sediments variations in the oxygen isotope ratio of seawater through time have important implications for the interpretation of the systematically low 18o values of pre jurassic marine sediments according to our model marine paleotemperatures could be up to 10 c lower than those expected when applying the classical hypothesis of an ice free ocean with a 18o value of 1

oxygen isotope compositions of phosphate from middle miocene early pliocene marine vertebrates of peru phosphatic remains of marine vertebrates recovered from five fossil sites of the pisco formation ranging from the latest middle earliest late miocene ca 11 13 ma to the early pliocene ca 3 5 ma have been analysed for their oxygen isotope compositions 18op coexisting seals dolphins whales penguins and sharks from each locality have distinct 18op values reflecting ecology and physiology differences ranging from 18 2 to 21 4 for marine mammals from 19 5 to 21 5 for marine birds and from 20 9 to 23 1 for sharks systematic offsets observed between dolphin teeth and bones as well as between dolphin and whale bones indicate that the fractionation equation established by using data from extant cetaceans may not be directly applicable to miocene cetaceans in order to estimate water 18ow values assuming that polar ice caps were not totally developed during this time interval marine palaeotemperatures ranging from 13 0 1 3 c to 17 2 1 3 c were estimated comparison of our results with those obtained in other world s areas suggests that the oxygen isotope ratios of pisco vertebrates reflect the influence of both global and local events such as the setting of the atacama desert the cold humboldt current or the global phases of ice cap growth and decay

raman spectroscopy of fossil bioapatite a proxy for diagenetic alteration of the oxygen isotope composition abstract fossil bioapatite may yield biogeochemical signals of paleoenvironments captured by living organisms bioapatite may be diagenetically altered however with ions added or removed post mortem such change is typically assessed using destructive and demanding techniques here raman spectroscopy is used as a rapid and non destructive way to identify significant diagenetic alteration of fossil bioapatite we found spectral parameters of phosphate symmetric stretching 1 po43 to be very sensitive to variations in apatite chemistry particularly with respect to common diagenetic components co32 f sr2 the raman spectral parameters were subsequently applied to a set of modern biogenic and geologic magmatic apatite samples as potential endmembers for diagenetic alteration raman spectra were also collected from enamel and dentin respectively resistant vs alteration prone of fossil teeth phosphate oxygen isotopic values from the same enamel dentin samples were used as an index of alteration and provided definition of raman spectral parameters as relates to diagenetic alteration diagenetically altered samples were characterised by spectra with 1 po43 widths at half maximum height less than 13 0 cm 1 and 1 po43 band positions greater than 964 7 cm 1 raman spectroscopy is shown to have potential as a tool for pre screening fossil apatite samples before further analyses

evolution of cenozoic seaways in the circum antarctic region abstract a complete circum antarctic seaway did not open until both the south tasman rise cleared the oates land coast of east antarctica and drake passage opened between the southern tip of south america and the northern end of the antarctic peninsula major plate motions based on dated seafloor spreading anomalies and distinct fracture zone lineations constrain the age of the opening of a seaway between the south tasman rise and antarctica as very close to the eocene oligocene boundary with an unrestricted opening deeper than 2000 m dating from 32 ma timing of the opening of drake passage is more circumstantial because the exact motions of certain micro continental fragments are not known the motion of africa with respect to south america as well as the motion of east antarctica with respect to africa are well constrained for the cenozoic these major plate motions are used with the reasonable assumption of no cenozoic motion of the antarctic peninsula with respect to east antarctica to constrain the location of the antarctic peninsula with respect to the southern tip of south america for the critical period of late eocene to late oligocene uncertainty of motion of the south georgia and south orkney microcontinents and other possible continental fragments make an exact time for opening of drake passage difficult to ascertain even so the early oligocene position of the antarctic peninsula with respect to south america requires a through going deep water seaway to have been open at drake passage prior to 28 ma even given the unconstrained motion of various high standing crustal fragments in the scotia sea with reasonable assumptions concerning motion of the crustal fragments in the western and central scotia sea it is likely that drake passage or passage through powell basin was open to deep water circulation by 31 2 ma

the preservation of glacial interglacial climatic signatures in the oxygen isotopes of elephant skeletal phosphate abstract phosphate 18o values 18op of modern elephant bone and teeth are found to vary linearly according to the 18o of local meteoric water 18omw a parameter with close ties to regional and local climatic conditions enamel dentine cementum and bone separates from individual fossil elephant specimens of late pleistocene age have op values which vary by up to elephant specimens the larger spread in the 18op values of the various skeletal phases for the fossil samples is interpreted as evidence for post depositional alterantion of primary 18op signatures of some if not all of these fossil skeletal components in the fossil samples investigated enamel and dentine phases have systematically lower 18o values than associated bone and cementum phases differential re equilibration with soil waters either by the wholesale replacement of primary apatite or by processes of isotopic exchange is suggested as a mechanism to account for the observed spread in the fossil phosphate 18o data

diagenesis and the reconstruction of paleoenvironments a method to restore original δ18o values of carbonate and phosphate from fossil tooth enamel abstract intra tooth 18 o variations within the carbonate 18 oc and phosphate 18 op components of tooth apatite were measured for miocene and pliocene hypsodont mammals from afghanistan greece and chad in order to evaluate the resistance of enamel to diagenetic alteration application of water apatite interaction models suggest that the different kinetic behaviours of the phosphate water and carbonate water systems can be used to detect subtle oxygen isotope disequilibria in fossil enamel when intra individual variations are considered selective alteration of the oxygen isotope composition from the carbonate component of afghan and greek enamels suggests inorganic isotopic exchange processes microbially induced isotopic exchange for phosphate is demonstrated for the first time in enamel samples from chad in association with extensive recrystallization in chad 18 op values were derived from partial isotopic exchange with fossil groundwater during early diagenesis mass balance calculations using average carbonate content in enamel as a proxy for recrystallization and the lowest 18 op value of dentine as a proxy for the isotopic composition of the diagenetic fluid indicate that diagenesis can alter 18 op by as much as 3 in some enamel samples this diagenetic alteration is also responsible for a decrease in intra individual variations of up to 1 in affected specimens the effects of diagenesis on 18 op values of fossil enamel are not systematic however and can only be estimated if sequential 18 op and 18 oc analyses are performed on fossil enamel and dentine reconstruction of large temporal or spatial scale paleoclimates based on 18 op analyses from mammalian teeth cannot be considered valid if enamel has been affected by bacterial activity or if the data cannot be corrected for diagenetic effects

oxygen and strontium isotopes from fossil shark teeth environmental and ecological implications for late palaeozoic european basins article i nfo fossil shark remains occur in both marine and nonmarine late palaeozoic deposits therefore their palaeo ecology is controversial the oxygen and strontium isotopic composition of biogenic fluorapatite in 179 teeth scales and spines predominantly of hybodontid lissodus and xenacanthiform orthacanthus xenacanthus bohemiacanthus triodus sharks from various late carboniferous moscovian to early permian artinskian basins of europe are used as ecological tracers to decipher diadromous or obligate freshwater lifestyle of the investigated taxa the 18 op values of the different shark teeth range from 11 7 to 20 2 within the different basins with mean values of 16 9 0 5 for the bohemian massif 16 2 0 8 for eastern germany 18 2 1 0 for southwestern germany 18 5 0 7 for southern central spain 17 6 0 4 for