trace and rare earth element compositions of silurian conodonts from the vesiku bone bed histological and palaeoenvironmental implications abstract in situ minor trace and rare earth element ree compositions have been measured in conodonts from the lower silurian vesiku bone bed estonia with the aim to visualize and to quantify conodont apatite elemental geochemistry to evaluate compositional differences between conodont histologies and to evaluate the use of conodont chemistry as a palaeobiological or palaeoenvironmental proxy tissue selective analyses of minor trace and rare earth element compositions of albid hyaline and basal tissues demonstrated significant chemical offsets among these histologies the albid tissue had the lowest ree and trace element concentrations suggesting crystallinity determined better resilience to diagenetic alteration as documented in previous studies conversely the basal tissue had highest concentrations of rees and many trace elements except for sr that showed an opposite trend the higher concentrations in albid and hyaline tissues supports the in vivo sr incorporation by conodont crown nonetheless the obtained sn normalized ree patterns were uniform through all the analyzed conodont taxa and different tissues implying common diagenetic history absence of a ce anomaly and defined negative eu anomaly indicate reducing conditions during early burial these results validate current interpretations of the palaeoenvironmental conditions during the deposition of vesiku bone bed and bolsters the use of rees in palaeozoic marine vertebrates as an important palaeoenvironmental proxy

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

provenance studies of esie sculptural soapstone from southwestern nigeria a group of soapstone statues found near the village of esie in southwestern nigeria is one of the largest collections of prehistoric sculpture found in sub saharan africa the statues were found at esie by people of the igbomina sub grouping of the yoruba ethnic group when they settled in the esie area some 300 years ago the origin of the statues remains unknown several areas of soapstone in the nigerian schist belt are considered as potential source areas for the esie statues mineral assemblages textures and compositions of talc cummingtonite and chlorite from some of the statues suggest a source for the statue soapstone from the agbonda area the closest proposed source area to esie however mineralogic data from one of the statues are unlike any of the proposed source areas the result of our study together with earlier studies of stevens hambolu and onabajo provides strong evidence that the soapstone statues were carved from local ultramafic rocks from esie area

diagenetic alteration of the structure and δ18o signature of palaeozoic fish and conodont apatite potential use for corrected isotope signatures in palaeoenvironmental interpretation abstract the oxygen isotopic compositions of carboniferous conodonts and fish microfossils ichthyoliths from identical samples were analysed in tandem in order to test whether these phosphatic media can be reliably used for palaeoclimatic reconstruction the structure of conodonts and of most ichthyoliths analysed are somewhat analogous to the enamel and dentine bone tissue respectively of modern mammals therefore the diagenetic susceptibilities of the taxa analysed may provide important clues to other palaeoclimatic studies utilising a variety of biogenic apatite thermal maturation indices and scanning electron microscopy were used to characterise the preservation of biogenic apatite despite a high conodont colour alteration index cai of 5 5 conodont elements appear to have been only mildly affected by diagenetic alteration in contrast ichthyoliths were commonly recrystallised and exhibited diagenetic apatitic overgrowths containing amorphous pyrolytic carbon interpreted as indicating that at least some overgrowth material derived from the original biogenic apatite diagenetic alteration has resulted in ichthyolith 18 o values being systematically lower by on average 2 9 1 0 3 relative to conodont apatite conodont samples yielded regionally correlatable isotope values which can be interpreted in terms of more palaeoenvironmentally sensible palaeotemperatures relative to ichthyolith values densely crystalline enamel like conodont elements are interpreted as the more robust phosphatic medium to preserve original isotopic compositions the strong correlation r 0 8 of the 18 o values of the more structurally pristine conodont and commonly recrystallised ichthyolith apatite indicates that i despite diagenetic lowering of absolute isotope values original palaeoenvironmental records may be preserved and ii diagenetic overprinting may result in a stable offset and therefore be correctable locally

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

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

rare earth elements in sedimentary phosphate deposits solution to the global ree crisis abstract the critical role of rare earth elements rees particularly heavy rees hrees in high tech industries has created a surge in demand that is quickly outstripping known global supply and has triggered a worldwide scramble to discover new sources the chemical analysis of 23 sedimentary phosphate deposits phosphorites in the united states demonstrates that they are significantly enriched in rees leaching experiments using dilute h2so4 and hcl extracted nearly 100 of their total ree content and show that the extraction of rees from phosphorites is not subject to the many technological and environmental challenges that vex the exploitation of many identified ree deposits our data suggest that phosphate rock currently mined in the united states has the potential to produce a significant proportion of the world s ree demand as a byproduct importantly the size and concentration of hrees in some unmined phosphorites dwarf the world s richest ree deposits secular variation in phosphate ree contents identifies geologic time periods favorable for the formation of currently unrecognized high ree phosphates the extraordinary endowment combined with the ease of ree extraction indicates that such phosphorites might be considered as a primary source of rees with the potential to resolve the global ree particularly for hree supply shortage

δ18o composition of conodont apatite indicates climatic cooling during the middle pridoli phosphatic microfossils such as conodonts and fish microremains dermal scales from the upper silurian pridoli of lithuania have been studied for their oxygen isotope composition the conodont c

upper proterozoic schist belts in the nigerian sector of the pan african province of west africa abstract schist belts in nigeria occur in a 400 km wide zone which trends nne parallel to the boundary between the pan african province and the west african craton a polycyclic migmatite gneiss granite terrain ranging in age from archaean to lower palaeozoic flanks the schist belt zone to east and west and separates the individual belts within the zone the schist belts fall into two age groups the earlier group contains assemblages of mafic igneous rocks pelitic schists and phyllites banded iron formation and locally coarse grained clastics and carbonate rocks these belts show complex structural styles and are extensively invaded by granitic plutons belonging to the widely distributed pan african magmatic suite schists and gneisses within and adjacent to some of these belts have been dated at 1100 ma and this group is thought to belong to the kibaran orogeny similar kibaran rock associations can be recognised elsewhere in the pan african province in the hoggar and cameroun the kibaran orogeny in this region is interpreted as a largely ensialic event although with possible minor ocean basin formation that led into the more intense and widespread pan african orogeny the later group of schist belts is characterised by coarse to fine grained clastics insignificant mafic igneous rocks a simple straight structural style and an absence of internal granite plutons these schist belts are believed to belong to the pan african orogeny their sediments may have been deposited in a back arc basin related to an e dipping subduction zone at the western margin of the pan african province

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

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

rare earth elements in solnhofen biogenic apatite geochemical clues to the palaeoenvironment rare earth element ree concentrations in biogenic apatite samples coprolite bone and soft tissue were used to investigate the environment of deposition of the celebrated solnhofen fossil lagerstatten the measured ree patterns are similar between different localities lithologies flinz faule and levels in the upper solnhofen plattenkalk suggestive of a stable ree supply during deposition the behaviour of cerium in the solnhofen samples implies that bottom water conditions were not anoxic and variations in the cerium anomaly can be explained by differences in burial rate these results provide further geochemical support for current depositional models barthel k w 1978 solnhofen ein blick in die erdgeschichte ott verlag thun barthel k w swinburne n h m conway morris s 1990 solnhofen a study in mesozoic palaeontology cambridge univ press cambridge that propose that extra basinal processes are responsible for the interbedded nature of the solnhofen deposits rather than intra basinal processes such as water turnover events

seawater rare earth element patterns preserved in apatite of pennsylvanian conodonts past workers have used rare earth element patterns recorded in biogenic apatite as proxies for original seawater chemistry to explore the potency of this approach we analyzed pennsylvanian conodonts from limestones gray shales and black shales of the fort scott and pawnee formations desmoinesian and swope and dennis formations missourian in kansas missouri and iowa u s a analysis of individual platform conodonts from seven taxa using laser ablation inductively coupled plasma mass spectrometry la icp ms revealed a consistent enrichment in the middle rare earth elements mree analogous mree enrichment has been observed in authigenic apatite and bulk samples of phosphate rich black shales from the same formations importantly however phosphate depleted shales intimately associated with the p rich intervals are relatively depleted in mree these antithetic patterns argue convincingly for secondary migration from the bulk sediment into the phosphate and the extent of mree enrichment in the conodonts is correlated positively with the total ree content mree enrichment in conodonts does not vary systematically as a function of lithology stratigraphic level conodont genus geographic location or with independent estimates of paleoredox conditions in the bottom waters collectively these results argue for postmortem diagenetic ree uptake resulting in a pronounced and progressive mree enrichment any cerium anomalies if initially present were masked by diagenetic uptake of ree paleoenvironmental interpretations of conodont ree particularly for samples exhibiting mree enrichment should therefore be viewed with caution

did cooling oceans trigger ordovician biodiversification evidence from conodont thermometry the ordovician period long considered a supergreenhouse state saw one of the greatest radiations of life in earth9s history previous temperature estimates of up to 70 c have spawned controversial speculation that the oxygen isotopic composition of seawater must have evolved over geological time we present a very different global climate record determined by ion microprobe oxygen isotope analyses of early ordovician silurian conodonts this record shows a steady cooling trend through the early ordovician reaching modern equatorial temperatures that were sustained throughout the middle and late ordovician this favorable climate regime implies not only that the oxygen isotopic composition of ordovician seawater was similar to that of today but also that climate played an overarching role in promoting the unprecedented increases in biodiversity that characterized this period

chemical characterization of some potsherd pavements from parts of yorubaland in southwestern nigeria several samples of potsherd pavement were recovered during excavation and archaeological reconnaissance of six sites along the trade and migration route of the yoruba of southwestern nigeria a significant feature of these pavements is the similarity to ife in design which consists of a herringbone design with a ritual pot embedded in their middle microscopic analysis of samples shows the presence of high proportions of non plastic grains mainly quartz micas minor plagioclases and traces of ferruginous grains tourmaline and amphibole interpreted as being produced by low temperature firing major trace and rare earth elements composition of 21 samples of sherds was determined using inductively coupled plasma icp ms technique the chemistry of the potsherd samples is generally similar to regolith derived from granitic rocks which are abundant in the area principal component analysis pca was used to reduce the number of variables and model based cluster analysis was used to find clusters in the pca scores model based clustering found one major cluster in the data set which corresponds to the local weathered granitic pegmatitic raw materials near the sites our work shows that the technology for the manufacture of these pavements might have originated from ile ife but the production was geologically controlled

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

effects of cloud diabatic heating on the early development of the fastex iop17 cyclone a set of numerical simulations is used to study the first development phase of the fastex cyclone a particularly well sampled frontal cyclone system that developed on the trailing front of a primary large scale baroclinic wave during intensive observation period 17 iop17 of fastex the fronts and atlantic storm track experiment the role of diabatically induced vertical circulations is investigated with a combination of diagnostic tools including a generalized omega equation and keyser s psi vector technique applied to the model outputs the full physics simulation shows a good agreement with observed data particularly the splitting of the upper level flow into a pair of jet streaks analysis of the contributions to the vertical ageostrophic transverse circulations near the jet streak pair structure shows that a positive feedback exists between the storm s dynamical configuration and the diabatic processes in the second part of the paper this interpretation is confirmed by a sensitivity analysis excluding cloud processes results suggest that after initial baroclinic growth the storm evolves towards a purely diabatic deepening regime leading to a diabatic rossby wave mechanism as proposed by recent wave cisk conditional instability of the second kind theoretical studies

variations in ce anomalies of conodonts through the frasnian famennian boundary of poland kowala holy cross mountains implications for the redox state of seawater and biodiversity abstract rare earth element ree concentrations on upper devonian conodonts distinguished by very low color alteration index were measured by inductively coupled plasma mass spectrometry from a stratigraphic section across the frasnian famennian f f boundary in the holy cross mountains poland the present data show a hat shaped pattern of the ree spectra similarly to other devonian conodont spectra already documented however our sample composition suggests little to moderate alteration of the original oceanic pattern through the adsorption mechanism in a context of weak or early diagenesis all along the section the magnitude of the ce anomaly is always negative and there is an inverse correlation between the ce anomaly and the la sm sn ratio this has been interpreted as an la enrichment due to a terrestrial input a mathematical procedure was used in order to restore the original ce anomalies that would reflect the seawater environment not contaminated by terrestrial inputs no noticeable change is observed in the frasnian with homogeneous values of ce model but a sharp increase is initiated just below the f f boundary with maximum values in the lowermost famennian the measured la sm sn ratios co vary with the ce model in agreement with the hypothesis of a terrigenous input finally the inverse correlation between the values of ce model and the relative abundance of palmatolepis during the famennian constitutes the first evidence known of a redox control on the presence of a conodont genus that is an indicator of deep water environment

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

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

diagenetic uptake of rare earth elements by bioapatite with an example from lower triassic conodonts of south china abstract the distribution patterns of rare earth elements rees are frequently used as proxies for ancient seawater chemistry or paleomarine environmental conditions however recent work has shown that diagenesis can lead to remobilization and inter elemental fractionation of rees and that these effects often occur in conjunction with redox reactions in sediment porewaters here we review existing literature on the diagenetic fluxes of rees in marine sediments and porewaters in order to systematize existing knowledge on this subject rees undergo significant redistribution among sediment phases during both early and late diagenesis as a consequence of adsorption and desorption processes remobilization of rees commonly leads to inter elemental fractionation variously leading to enrichment or depletion of the light middle or heavy ree fractions further ree remobilization can be facilitated by redox changes e g through reductive dissolution of host phases in suboxic and anoxic porewaters characteristic ree distribution patterns develop through these processes 1 a flat distribution signifying predominantly terrigenous siliciclastic influence 2 a middle ree bulge probably due to adsorption of light and heavy rees to mn and fe oxyhydroxides respectively and 3 heavy ree enrichment indicative of hydrogenous seawater influence note all patterns in this paper are normalized to the ree composition of average upper continental crust or ucc in the second part of this study we undertake an analysis of the ree distributions in conodonts and whole rock samples from west pingdingshan a permian triassic boundary section in south china using ree th and y ho ratios we show that almost all of the conodont samples have a strong diagenetic overprint and that the hydrogenous ree fraction is small and not isolatable furthermore the conodonts contain two diagenetic ree components one characterized by low ree 100 300 ppm high ree th ratios 1000 strong middle ree enrichment and eu eu ratios of 1 5 2 0 and the second by high ree 300 2000 ppm low ree th ratios 20 30 little or no middle ree enrichment and eu eu ratios of 1 0 the first component exhibits a pronounced middle ree bulge that represents an early diagenetic signature associated with suboxic conditions possibly related to adsorption of rees onto fe mn oxyhydroxides in the shallow subsurface environment the second component shows a flat ree distribution that is similar to both our whole rock samples and average ucc indicating derivation from rees released from detrital siliciclastics e g clay minerals probably at a range of burial depths from shallow to deep failure of the conodont samples to yield an isolatable hydrogenous component demonstrates that bioapatite does not always preserve a primary marine ree signature given that bioapatite rees have been widely used for this purpose often on the assumption of minimal or no diagenetic influence our findings are likely to necessitate a re evaluation of the results of many earlier studies in general we counsel caution in inferring a hydrogenous origin for rees in bioapatite owing to frequent diagenetic alteration of ree distributions

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

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

paleoenvironmental interpretations of rare earth element signatures in mosasaurs reptilia from the upper cretaceous pierre shale central south dakota usa abstract rare earth elements were analyzed from fossil marine reptile mosasauridae bones collected from five superposed members sharon springs gregory crow creek degrey and verendrye of the upper cretaceous pierre shale at localities along the missouri river in brule buffalo hughes and hyde counties in central south dakota fossil bones from each member of the pierre shale have different rare earth element ree signatures that may be distinctive over wide geographic areas fossils from the sharon springs member have distinctive ree signatures that may be further subdivided into three superposed groups that correspond with the upper middle and lower sharon springs member ree signatures are distinctive from each stratigraphic unit therefore fossils eroded from their stratigraphic context may be assigned to their proper depositional unit based on ree signature comparisons differences in ree compositions of bones among members appear to result from differential mixing of oxygenated and anoxic seawaters if differences in mixing are interpreted as depth differences the lower sharon springs member was deposited in deep anoxic water water depths decrease in the middle and upper sharon springs and the overlying gregory and crow creek members were deposited in even more shallow water finally according to this interpretation the overlying degrey and verendrye members were deposited in progressively deeper marine waters but not as deep as the lower sharon springs these interpretations are generally consistent with those based on faunal diversity and eustatic sea level curves

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

oxygen isotope variations in phosphate of biogenic apatites iii conodonts abstract the method for measurement of the isotopic composition of oxygen in phosphates has been improved and adapted for analysis of small quantities of apatite down to 10 mg this extension enables one to analyze hand picked conodont samples with an analytical reproducibility better than 0 5 1 46 samples of conodonts ranging from the ordovician to the pennsylvanian of north america were analysed some insoluble phosphatic residues ichthyoliths and inarticulate brachiopods of the same time range were also measured the range of the 18o values of the analysed conodonts is between 15 and 19 it shows a general trend of decreasing d18o with increasing age from an average value of about 19 in the pennsylvanian to 17 in the ordovician this trend parallels that previously detected in marine phosphorites for the time range between the devonian and pennsylvanian our data are in agreement with independent paleoclimatic information specifically we detect maximum18o enrichment at the end of the pennsylvanian and minimum enrichment at the end of the devonian the difference between these two extremes is equivalent to about 10 c from about 40 to 30 c assuming constant isotopic composition of ocean water the success of oxygen isotopic analysis of conodonts raises the possibility of their use in paleozoic paleo oceanography in a similar way to foraminifera in the mesozoic cenozoic

trace element geochemistry and petrogenesis of some meta ultramafites in apomu and ife ilesa areas of southwestern nigeria some high magnesian rocks mgo 23 32 having chemical similarity with rocks from komatititic suites were subjected to a detailed geochemical study which lead to a discussion of their petrogenesis all rocks were subjected to regional metamorphism of upper greenschist to amphibolite facies consequently the discussions on petrogenesis have relied heavily on the abundance of the less mobile elements such as rare earth elements and some transition elements e g ni and cr in general the meta ultramafites show almost flat heavy rare earth element and extensive enrichment in light rare earth elements la sm n 1 3 6 3 and ce yb n 0 8 28 ni 1700 4400 ppm and cr 1400 5200 ppm are enhanced which is consistent with their ultramafic parentage the komatiitic meta ultramafic rocks of southwestern nigeria are highly enriched in most trace elements relative to komatiites from well known areas of the world this extensive enrichment is considered to be mostly a characteristic of the source region of these rocks

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

oxygen isotope variability in conodonts implications for reconstructing palaeozoic palaeoclimates and palaeoceanography conodonts have the potential to elucidate the intricacies of palaeozoic climates especially if 18 o values of single apatitic tooth like elements can be used to map evolving sea surface temperatures and differentiate oceanic water masses their ecological distribution as pelagic and nektobenthic organisms high resolution biostratigraphy and abundance in cambrian triassic rocks qualifies them as potentially robust climate archives previous ion microprobe conodont 18 o studies have proceeded directly to palaeotemperature interpretation without appreciation of inter and intra element variability or post mortem artefacts here ion microprobe analyses of ordovician and silurian conodonts establishes that intra element crown tissue 18 o typically varies by 1 53 of conodonts analysed is normally 2 92 of analyses and rarely varies by 2 4 18 o can vary across elements suggesting a microstructural and or diagenetic control 18 o can vary between species representatives by c 3 18 o of pelagic and nektobenthic taxa can be offset by 2 3 elements processed with formic acid have highly variable 18 o and thermal alteration does affect 18 o conodont ion microprobe 18 o values are comparable with those of bulk methods but utilization of material with no consideration of geological context or processing history may introduce significant artefacts a protocol for future conodont oxygen isotope ion microprobe studies is proposed supplementary material full results of oxygen isotope analyses reported in this paper are available at www geolsoc org uk sup18516

oxygen isotope evolution of biogenic calcite and apatite during the middle and late devonian oxygen isotope ratios of well preserved brachiopod calcite and conodont apatite were used to reconstruct the palaeotemperature history of the middle and late devonian by assuming an oxygen isotopic composition of 1 v smow for devonian seawater the oxygen isotope values of eifelian and early givetian brachiopods and conodonts give average palaeotemperatures ranging from 22 to 25 c late givetian and frasnian palaeotemperatures calculated from 18o values of conodont apatite are close to 25 c in the early frasnian and increase to 32 c in the latest frasnian and early famennian oxygen isotope ratios of late givetian and frasnian brachiopods are significantly lower than equilibrium values calculated from conodont apatite 18o values and give unrealistically warm temperatures ranging from 30 to 40 c diagenetic recrystallization of shell calcite different habitats of conodonts and brachiopods as well as non equilibrium fractionation processes during the precipitation of brachiopod calcite cannot explain the 18o depletion of brachiopod calcite moreover the 18o depletion of brachiopod calcite with respect to equilibrium 18o values calculated from conodont apatite is too large to be explained by a change in seawater ph that might have influenced the oxygen isotopic composition of brachiopod calcite the realistic palaeotemperatures derived from 18o apatite may suggest that biogenic apatite records the oxygen isotopic composition and palaeotemperature of palaeozoic oceans more faithfully than brachiopod calcite and do not support the hypothesis that the 18o 16o ratio of devonian seawater was significantly different from that of the modern ocean

stable isotope composition and rare earth element content of vertebrate remains from the late cretaceous of northern spain lano did the environmental record survive abstract oxygen and carbon isotope measurements have been performed on phosphatic remains from faunal associations dinosaurs crocodiles turtles and fish of the late cretaceous continental and marine sediments from northern spain basque country the environmental meaning of the oxygen isotope record in fossil reptiles is discussed on the basis of known paleoecology modern fauna analogs and apatite chemistry rare earth elements ree co32 and po43 contents fossil remains in sandstones and argillites from two localities urria and cuezva have low down to 16 and scattered 18o po4 co3 and 13c values with ree patterns characterized by strong middle ree enrichments these geochemical compositions of the biogenic apatites have most likely been acquired during a multi stage late diagenesis involving complete recrystallization of the apatite in the presence of aqueous fluids ree contents of fossils preserved in the clayey sands from the site of lano suggest that samples have only been affected by early diagenesis despite the diversity of analyzed taxa and the close association of marine sharks and rays and freshwater species crocodiles and turtles evolving in a littoral environment the narrow range of phosphate 18o values is interpreted as reflecting the temperature and isotopic composition of groundwaters that prevailed in the burial environment the potential information relative to the physiology and thermal regime of the vertebrates has been erased during the process of early diagenesis if all oxygen in the phosphate has exchanged with groundwaters the oxygen isotope composition of vertebrate remains suggests that a warm climate t 20 25 c prevailed in northern spain during the late cretaceous

soapstone as a locally used and limited sculptural material in remote area of northern moravia czech republic in contrast to nordic countries talc rich rocks massive and schistose talc bearing rocks talcite magnesite talc schists chlorite talc schists and or chlorite actinolite talc schists often loosely classified as soapstone represented practically an unknown natural building and sculptural stone in the czech republic this extraordinary material was quarried and used in the only region of the czech republic where sobotin amphibolite massif sumperk district northern moravia outcrops metamorphosed basic igneous rocks contain small lenses of soapstone that were exploited in the past and used not only for refractory purposes but also as a construction and sculptural material occurrences of sobotin soapstone show distinct zone macrofabric marked by the occurrence of massive soapstone in the core that gradually changes to talc dominant schists later to actinolite tremolite rich schists and finally to chlorite schists at the contact with surrounding amphibolites the most typical sobotin soapstone exhibits high density up to 2 900 kg m 3 low water uptake maximum 0 68 wt favorable dynamic elastic properties p wave velocity 5 340 5 840 m s 1 s wave velocity 2 900 3 300 m s 1 and mechanical properties tensile splitting strength 5 2 6 9 mpa uniaxial compressive strength 17 5 24 1 mpa sobotin soapstone is relatively resistant to weathering action although schistose varieties show typical delamination when exposed to frequent freeze thaw cycling in harsh mountainous environment field survey of monuments architectural and building artefacts made from sobotin soapstone contributed to our knowledge on duration of exploitation of sobotin soapstone that was for sure utilised from the second half of seventeen century till the beginning of the twenty century the most characteristic feature of sobotin soapstone is its strict local use on the territory of about 20 villages surrounding previously exploited soapstone lenses