revisiting the rare earth elements in foraminiferal tests are the rare earth elements rees in foraminifera a valuable proxy for use in paleoceanographic and climate change studies in order to investigate this we attempted a comprehensive study of rees in planktonic and benthic foraminifera several different cleaning protocols were tested although the hydroxylamine used to clean all foraminifera in this study removes an unidentified source of ree contamination it seems to remobilize metal oxides that are otherwise unaffected in flow through dissolution the calculated ree distribution coefficients kd ree s are between 100 and 500 for both planktonic and benthic foraminifera these kds are high compared to other elements in biogenic calcite but can be explained through a general model of element incorporation during foraminiferal calcification from data taken from eight core tops in the southeast pacific we conclude that the rees in planktonic foraminifera are indeed useful as a proxy for upper ocean water mass and mixed layer biogenic productivity alternatively the rees in benthic foraminifera are useful as a proxy for carbon flux to the sea floor these proxies should be robust down core unless the sediments have undergone anoxic diagenesis which stabilizes fe carbonate thus overprinting the primary ree signature however it is clear from ree distributions in foraminiferal tests if anoxic conditions have occurred

controls on phosphorus concentration and accumulation in oceanic sediments understanding phosphorus p sedimentation in the ocean is important both for quantifying outputs in the marine phosphorus cycle and for determining the controls on phosphogenesis the authigenic formation of carbonate fluorapatite and phosphorite deposition large accumulations of p rich sediments on continental margins in this study i have compiled literature data on sedimentary p concentrations and sedimentation rates from continental margins phosphogenic continental margins and open ocean environments i have also calculated p accumulation rates the product of p concentration sediment density and sedimentation rate in these settings sedimentary p concentrations exhibit a similar range in a wide variety of oceanic environments and sedimentation rate conditions for example p concentrations in continental margin sediments range from 8 to 108 mol p g 1 with sedimentation rates from 80 to 8 000 m my 1 in open ocean sediments the p concentration range is similar 7 307 mol p g 1 even though sedimentation rates are generally about 100 times lower 2 50 m my 1 the exception to this are phosphogenic environments where p concentrations are exceptionally high 580 3 700 mol p g 1 while sedimentation rates are relatively low 20 310 m my 1 phosphorus accumulation rates appear to be controlled by sedimentation rate in ocean sediments although p concentrations generally exhibit similar ranges the large difference in sedimentation rates between various environments results in p accumulation rates that are several orders of magnitude higher in continental margins 90 8 000 mol p cm 2 kyr 1 compared to open ocean sediments 2 75 mol p cm 2 kyr 1 in the case of phosphogenic environments low sedimentation rates result in p accumulation rates 80 6 300 mol p cm 2 kyr 1 that are surprisingly similar to those of non phosphogenic continental margin sediments

diagenetic evolution of the upper devonian phosphorites alborz mountain range northern iran abstract the upper devonian mixed siliciclastic carbonate stratigraphic succession of the geirud formation in the alborz mountain range north of iran hosts numerous phosphorites and phosphatic rocks these phosphorites which represent one of the most globally important deposits in the devonian have gained little attention regarding their genesis and diagenetic evolution this study focuses mainly on the post depositional changes that occurred during shallow to deep burial diagenetic evolution and subaerial weathering of the geirud phosphorites the phosphorites consist of phosphatic massive mudclasts detritus rich lithoclasts bioclasts and bones formed by several stages of phosphogenesis and erosion reworking winnowing and condensation associated with famennian sea level changes the phosphatic clasts consist of early diagenetic poorly crystalline carbonate fluorapatite cfa and pyrite cementing detrital quartz illite muscovite rutile and zircon phosphatic clasts are intensely compacted with sutured grain contacts along which dissolution and reprecipitation of chemically refined well crystalline cfa with a bright blue cathodoluminescence and illite occurred during deep burial diagenesis similarly quartz shows deformation planar features overgrowth cement was developed as a result of pressure dissolution in phosphatic sandstones followed by precipitation of ferroan dolomite ankerite and chlorite in secondary porosity subaerial weathering led to oxidation of pyrite and generation of acidic ph condition under which ca and p from phosphates fe and s from pyrite fe ca mg and mn from ferroan carbonates and al and si from aluminosilicates were released to form goethite psilomelane calcite gypsum and crandallite the paas normalized rare earth elements rees show bell shaped patterns with middle rees enrichment positive eu anomaly and a weak negative ce anomaly this implies recrystallization of cfa in phosphorites and phosphatic rocks during deep burial diagenesis deviating from the modern seawater like ree patterns in this regard deep burial diagenesis affecting the upper devonian geirud phosphorites is possibly a common process in the proterozoic paleozoic phosphorites in northern iran and elsewhere in the world

application of the ce anomaly as a paleoredox indicator the ground rules much attention has been paid in recent years to the potential application of the ce anomaly measured in various marine phases as a paleoceanographic indicator of widespread marine anoxia in this paper we present and discuss results from recent studies of present day rare earth element ree distributions and hence ce anomaly distributions in the marine environment which are particularly pertinent to paleoceanography subsequently we review and discuss the validity of the recent literature in which ce anomalies have been employed as paleoredox indicators

temperate carbonate platform drowning linked to miocene oceanographic events maiella platform margin italy carbonate platform drownings are frequent often synchronous global occurrences yet explanations for these world wide events remain unsatisfactory in the central apennines lower and middle miocene carbonate rocks deposited on a temperate ramp in the maiella platform margin record two episodes of platform drowning followed by hemipelagic sedimentation dated as latest oligocene aquitanian 26 23 ma and as burdigalian langhian 20 16 ma a high resolution stratigraphy based on strontium isotopes allows us to correlate key phases of platform evolution with events recorded in deep water ocean sediments this paper suggests that high weathering rates and nutrient input in the mediterranean during the early and middle miocene possibly linked to the uplift of the tibetan region set the preconditions for platform drowning which were ultimately caused by rapid eustatic sea level rises

identification of primary ce anomaly signatures in fossil biogenic apatite implication for the cambrian oceanic anoxia and phosphogenesis based on ree analyses of 105 world wide distributed cambrian fossil apatite samples and eight late neoproterozoic phosphate concretions a close relationship is established between the concentrations of mree and ce anomalies shale la smn ratios of 0 35 is suggested as a critical value for the discrimination of the natural ce anomaly acquired during pre burial early diagenesis by biogenic apatite from an artificial ce anomaly induced due to the calculation ce anomalies in apatites with flat ree distribution and la smn ratio 0 35 may be used as indicative of oceanic anoxia

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

evaluation of the application of rare earth elements to paleoceanography anomalous departures of rare earth elements ree from similarity of chemical behaviour are most evident in a comparison of ce with its neighbors under reducing conditions ce3 acts like other ree but oxidized ce4 is adsorbed on mn fe oxyhydroxides or organic particulates and consequently the remaining solution will tend to exhibit a negative ce anomaly in addition more subtle fractionations may emphasize the light or the heavy or the middle ree a pattern of ree may be recorded by immediate diagenesis on a suitable chemical substrate such as apatite fish debris conodonts carbonate or chert this record was originally thought to reflect the paleoredox conditions of primary deposition however any such primary record may be overprinted by late diagenetic alteration early analyses of ree in conodonts from a wide range of sediments suggested a prevalence of reducing conditions no ce anomaly in pre carboniferous oceans and more common oxidation negative ce anomaly in the late paleozoic however recent research by other investigators indicates that variations in cean are more diverse in origin and in particular many are distorted to an unknown extent by late diagenesis in any case it is now clear that geological age does not show a consistent relationship to the level of the ce anomaly the ce anomaly apparently does not play any regular role in the isotopic events that accompany prominent mass extinctions further research is required to understand and thus make useful the controls on the ce anomaly

orbitally paced phosphogenesis in mediterranean shallow marine carbonates during the middle miocene monterey event during the oligo miocene major phases of phosphogenesis occurred in the earth s oceans however most phosphate deposits represent condensed or allochthonous hemipelagic deposits formed by complex physical and chemical enrichment processes limiting their applicability for the study regarding the temporal pacing of miocene phosphogenesis the oligo miocene decontra section located on the maiella platform central apennines italy is a widely continuous carbonate succession deposited in a mostly middle to outer neritic setting of particular interest are the well winnowed grain to packstones of the middle miocene bryozoan limestone where occurrences of authigenic phosphate grains coincide with the prominent carbon isotope excursion of the monterey event this unique setting allows the analysis of orbital forcing on phosphogenesis within a bio chemo and cyclostratigraphically constrained age model la icp ms analyses revealed a significant enrichment of uranium in the studied authigenic phosphates compared to the surrounding carbonates allowing natural gamma radiation gr to be used as a qualitative proxy for autochthonous phosphate content time series analyses indicate a strong 405 kyr eccentricity forcing of gr in the bryozoan limestone these results link maxima in the gr record and thus phosphate content to orbitally paced increases in the burial of organic carbon particularly during the carbon isotope maxima of the monterey event thus phosphogenesis during the middle miocene in the mediterranean was controlled by the 405 kyr eccentricity and its influence on large scale paleoproductivity patterns rare earth element data were used as a tool to reconstruct the formation conditions of the investigated phosphates indicating generally oxic formation conditions which are consistent with microbially mediated phosphogenesis

chemical evolution of rare earth elements fractionation between colloidal and solution phases of filtered river water abstract within the dissolved fraction of connecticut river water there is large scale fractionation of rare earth elements between colloidal and solution phases colloidal particles carry a large part of the dissolved ree pool filtration through filters with progressively smaller pore size 0 45 0 22 and 0 025 m results in filtrates with lower absolute concentrations of ree and more fractionated compositions with decreasing pore size the filtrates have shale normalized abundances which become systematically more depleted in the lree relative to the hree hence both the solution and colloidal phases are significantly fractionated with respect to the dissolved fraction these conclusions are consistent with previous studies of ree in rivers estuaries and soils and with surface solution speciation models colloids play an important role in the aquatic geochemistry of rare earth elements they are responsible for the fractionation of ree during the estuarine removal of ree the removal of suspended and colloidal particles from river water leaves the solution phase of river water with compositions of ree as evolved as those of surface seawater hence the evolution of the composition of ree in river water and seawater is significantly influenced by colloid formation during chemical weathering on the continents

carbonate systems along nutrient and temperature gradients some sedimentological and geochemical constraints research over the past several decades has clearly demonstrated that changes in the ocean environment have had major impacts on carbonate systems changes in climate ocean circulation and seafloor spreading rates have influenced temperature and seawater chemistry including carbonate saturation state and nutrient availability and thereby have determined boundary conditions for the biota that form carbonate platforms in turn the biota determine accumulation rates and facies zonations thus controlling platform geometry and facies dynamics in the first section of this paper we examine how nutrient availability influences carbonate facies associations we first discuss the role of temperature and nutrient gradients in the modern ocean and their influence on biotic associations then we discuss how carbonate sedimentation can be characterized along nutrient gradients in the second section we review proxies currently used to reconstruct paleoproductivity in open ocean environments and discuss their applicability to neritic carbonate systems we highlight the variety of existing proxies and their limitations and suggest that multiple lines of evidence are needed for valid interpretations our short review discusses sedimentological biogenic and geochemical proxies that can be used to reconstruct past nutrient fluxes and to constrain paleoceanographic controls over the distribution of carbonate associations however it also reveals that more data and case studies are needed that integrate shallow and deep water carbonate sequences and elucidate the links between temperature vs nutrient supplies changes and facies in ancient carbonate sequences

rare earth elements and radiogenic strontium isotopes in carbonate minerals reveal diagenetic influence in shales and limestones in the appalachian basin abstract rare earth element ree signatures are often applied to interpret paleoenvironmental conditions in sedimentary basins however the complicated diagenetic histories in dynamic depositional environments can affect interpretation of measured ree signatures prior studies on ree content in shales and limestones indicated that ree in specific mineral phases may provide unique information concerning diagenetic reactions occurring in sedimentary rocks during burial and compaction application of sequential extraction techniques to target ree signatures in specific mineral fractions may provide greater insight into the complex processes that occurred during diagenesis and catagenesis thus using this technique this study provides a detailed account for ree 87sr 86sr and 13c in the carbonate fraction of the marcellus shale and adjacent formations in the appalachian basin a suite of 49 rock samples collected from two cores recovered from monongalia county west virginia usa was analyzed the results showed that the carbonate concretions in calcareous shales and carbonate cements in black shales were very distinct the ree plus yttrium rey were more concentrated in the carbonate concretions than in the carbonate cements the carbonate concretions displayed rey patterns that are closely similar to modern seawater while mree enrichment was observed in the carbonate cements likewise the 87sr 86sr values in the carbonate concretions were similar to those measured for unaltered middle devonian carbonates while the 87sr 86sr in the carbonate cements were much more radiogenic this observation indicates that the carbonate cement could have been inherited radiogenic 87sr expulsed from clays during illite smectite transition overall this study demonstrated two distinct processes involved with controlling the carbonate geochemistry within appalachian basin shales and limestones one fraction displaying minimal diagenetic alteration relative to depositional conditions carbonate concretions in calcareous shales and limestone carbonate in limestones and another fraction displaying the evidence for extensive chemical alteration during illite smectite transition and catagenesis carbonate cements in black shales in addition highly variable and significant enrichments of u and mo demonstrate that the union spring member and the lower oatka creek member of the marcellus shale in the southwestern appalachian basin mseel site were deposited under mainly anoxic environment whereas intermitted episodes of dysoxic to perhaps oxic conditions occurred during the deposition of the upper oatka creek member

ree patterns in latest neoproterozoic early cambrian phosphate concretions and associated organic matter abstract analyses of ree were conducted on phosphatic concretions and various types of associated organic matter in eight key latest neoproterozoic earliest cambrian inner to outer shelf marine phosphatic successions that are distributed worldwide a pronounced ree fractionation during diagenetic degradation of the organic matter has been revealed selective mree incorporation and bulk ree contents in some kerogens organic megascopic fossils and humic acid are compatible with those recorded in associated phosphate the similarity of ree patterns in apatite and organic matter suggests that early diagenetic microbial decomposition of organic matter does not only provide phosphorus and suitable sub oxic geochemical conditions but it is also a likely source of ree enrichment in authigenic apatite formed at shallow depths below the marine water sediment interface

reconstructing the depth of the permanent thermocline through the morphology and geochemistry of the deep dwelling planktonic foraminifer globorotalia truncatulinoides geochemical and morphological characteristics of globorotalia truncatulinoides a deep dwelling planktonic foraminifer have been used since the mid 1950s to infer paleo oceanographic conditions of the upper ocean the coiling ratio has been linked to different water masses and stable oxygen isotope signal of this species to changes in depth habitat and or season here we show that the isotopic composition of single specimens covering termination iii of multiple size fractions of north atlantic g truncatulinoidessinistral is indicative of a deeper calcification depth in the water column compared to g truncatulinoidesdextral as previously indirectly inferred in a plankton tow study furthermore the change in coiling ratio from dominantly g truncatulinoidesdextral 95 to brief episodes of dominantly g truncatulinoidessinistral 80 gives a strong indication of deepening of the permanent thermocline during periods in which g truncatulinoidessinistral was dominant the position of the permanent thermocline during marine isotope stages 8 and 7 echoes the relative strength of the atlantic meridional overturning circulation amoc dominated by interglacial glacial dynamics we demonstrate that glacial heinrich ice rafted debris events appear to proceed a permanent thermocline shoaling whereas interglacial heinrich events follow the shoaling of the permanent thermocline likely a result of a weakened amoc

paleoflood hydrology origin progress prospects from an origin in diverse studies of flood geomorphology and quaternary geology paleoflood hydrology emerged as a geophysical and an applied hydrological science during the 1970s and 1980s since acquiring its formal name in 1982 the most productive approach in paleoflood hydrology has become energy based inverse hydraulic modeling of discrete paleoflood events recorded in appropriate settings as slackwater deposits and other paleostage indicators swd psi or as various threshold indicators of non exceedence technological advances particularly in hydraulic modeling and geochronology were instrumental in moving the discipline to its present status the most recent advances include 1 new techniques for the accurate geochronology of flood sediments notably tams radiocarbon analyses and osl dating and 2 the phenomenal increase in computer power that allows complex hydraulic calculations to become feasible for routine studies from its initial demonstration in the southwestern united states swd psi paleoflood hydrology proved its widespread applicability to various landscape environments particularly important studies have been accomplished in australia china india israel south africa spain and thailand paleoflood hydrology has also generated its share of controversy in part because of the differing viewpoints and attitudes of the two scientific traditions from which it emerged quaternary geology geomorphology versus applied hydrologic hydraulic engineering nevertheless the future growth of the discipline is assured given the rapid pace of discoveries that it engenders indeed so many international studies exist that it is appropriate to pursue global syntheses to address interesting and timely questions of extreme flood phenomena in relation to global climatic change

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

bacterial origin of east australian continental margin phosphorites many models of the origin of marine phosphorites require a sediment rich in organic matter which by decomposition releases phosphorus for the precipitation of carbonate fluorapatite1 7 this concept is useful in explaining contemporary phosphorite in areas of very high productivity off the coasts of peru chile and south west africa8 10 where there are high organic matter fluxes to the sea floor4 7 11 it does not explain the origin of marine phosphorite deposits which formed in regions of limited oceanic upwelling and productivity12 14 the east australian continental margin an area of phosphogenesis throughout the late pleistocene and holocene13 14 is a modern analogue of an east coast phosphogenic province15 17 with low productivity over the upper slope region where the most recent phosphorites have been found18 evidence is reported here for the carbonate fluorapatite in the east australian phosphorites being located within bacterial cellular structures and a model proposed for the origin of these deposits through the slow bacterial assimilation of phosphorus from seawater in an area of restricted sedimentation

correlating carbon and oxygen isotope events in early to middle miocene shallow marine carbonates in the mediterranean region using orbitally tuned chemostratigraphy and lithostratigraphy during the miocene prominent oxygen isotope events mi events reflect major changes in glaciation while carbonate isotope maxima cm events reflect changes in organic carbon burial particularly during the monterey carbon isotope excursion however despite their importance to the global climate history they have never been recorded in shallow marine carbonate successions the decontra section on the maiella platform central apennines italy however allows to resolve them for the first time in such a setting during the early to middle miocene the present study improves the stratigraphic resolution of parts of the decontra section via orbital tuning of high resolution gamma ray gr and magnetic susceptibility data to the 405 kyr eccentricity metronome the tuning allows within the established biostratigraphic sequence stratigraphic and isotope stratigraphic frameworks a precise correlation of the decontra section with pelagic records of the mediterranean region as well as the global paleoclimatic record and the global sea level curve spectral series analyses of gr data further indicate that the 405 kyr orbital cycle is particularly well preserved during the monterey event since gr is a direct proxy for authigenic uranium precipitation during increased burial of organic carbon in the decontra section it follows the same long term orbital pacing as observed in the carbon isotope records the 405 kyr gr beat is thus correlated with the carbon isotope maxima observed during the monterey event finally the mi events can now be recognized in the 18o record and coincide with plankton rich siliceous or phosphatic horizons in the lithology of the section

accurate trace element analysis of speleothems and biogenic calcium carbonates by la icp ms the high spatial resolution of laser ablation inductively coupled plasma mass spectrometry la icp ms microanalysis of speleothems and biogenic calcium carbonates makes it possible to improve our understanding of past climatic conditions however there are analytical problems associated with this method such as molecular interferences elemental fractionation and mass load dependent matrix effects when using nist silicate reference glasses for calibration our study with a sector field icp ms shows that many masses are affected by interferences such as 24mg by 48ca or 31p by 15n16o elemental fractionation and mass load dependent matrix effects have been detected for both 213 and 193 nm nd yag lasers they are small for refractory lithophile elements in particular for the 193 nm laser 5 for chalcophile siderophile trace elements with low boiling points however these effects are large up to 40 and 20 for the 213 and 193 nm lasers respectively and variable for the nist glasses and carbonates in this paper a protocol for precise and accurate la icp ms analysis of calcium carbonates is established isotopes for interference free measurements at low m m 300 and medium m m 4000 mass resolution have been identified the nist glasses are suitable for calibration of refractory lithophile element concentrations however matrix matched calibration with carbonate reference materials such as usgs macs 1 or macs 3 is necessary for accurate analysis of chalcophile siderophile elements with low boiling points analytical reproducibility rsd is a factor of 2 better using the 193 nm laser than the 213 nm laser as shown by the analysis of macs 1 and macs 3 la icp ms analyses yield results that agree with the reference values within relative uncertainties of ca 5 10 at the 95 confidence level we have applied la icp ms for the determination of trace element concentrations in calcite and aragonite layers of a stalagmite and found large variations for mg zn sr and u in ostracod shells the concentrations of some trace elements e g sr and ba vary significantly indicating the potential for paleoclimate research

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

miocene phosphate rich sediments in salento southern italy abstract the upper middle to lower upper miocene serravallian to tortonian sedimentary succession in salento southern italy includes glauconite and phosphate rich deposits which are associated with pelagic micrite in baia del ciolo and marittima southern salento the succession is composed of shallow water platform carbonates of late oligocene age chattian porto badisco formation which are overlain by a 20 to 30 cm thick level of glauconite rich micrite with abundant reworked particles and fossils of the underlying porto badisco formation this interval is in turn covered by an up to 15 cm thick phosphatic crust livello ad aturia which itself is overlain either by a hemipelagic chalk like carbonate of middle to late miocene age pietra leccese marittima or directly by a micrite of late miocene age messinian novaglie formation baia del ciolo which shallows upwards into a shallow water platform carbonate a large hiatus is present in this succession which likely includes the lower and lower middle miocene in the region of lecce two discrete levels enriched in glauconite and phosphate each associated with a major discontinuity occur within the pietra leccese the strontium isotope ages derived on phosphate nodules and phosphatized and non phosphatized fossils and calcareous nannofossil ages indicate a time interval of phosphogenesis between 13 5 and 7 5 ma with two clusters at 12 and 10 5 ma the glauconite and phosphate rich sediments resulted from a current dominated regime which was characterized by low overall sedimentation rates erosion and sediment reworking and authigenesis this regime was likely related to a generally westward directed bottom current which was forced to upwell once it arrived at the western border of the eastern mediterranean basin the timing of the principal phosphogenic phases can only partly be correlated to those of other occurrences in this part of the mediterranean malta gozo southern sicily matese latium abruzzi platform the partial diachrony in phosphogenesis may express the effect of lateral switching in and or focusing of upwelling zones

phosphogenesis and organic carbon preservation in the miocene monterey formation at naples beach california the monterey hypothesis revisited the middle part of the miocene monterey formation at naples beach west of santa barbara california is predominantly composed of organic rich mudstone interstratified with phosphatic laminae minor lithologies include volcanic ash dolomite porcelanite and chert and condensed phosphatic beds sediments dated as 14 3 13 5 ma have average total organic carbon toc values around 8 5 wt and organic carbon oc accumulation rates are around 565 mg cm2 k y sediments dated as 13 5 13 ma are characterized by average toc values of 12 6 wt and oc accumulation rates of around 1130 mg cm2 k y the interval between 13 and 10 6 ma is marked by condensation average toc values are around 8 6 wt and oc accumulation rates diminished to around 55 mg cm2 k y the last interval studied is dated as 10 6 9 4 ma and average toc values are around 6 wt whereas oc accumulation rates rose again to 320 mg cm2 k y the presence of erosional surfaces angular unconformities and reworked clasts and nodules suggests that bottom current activity and gravity flow deposition have been instrumental in sediment accumulation the phosphatic laminae were precipitated at a very early stage of diagenesis during periods of nonsedimentation they formed less permeable sedimentary lids and may as such have contributed to enhanced oc preservation between 13 and 10 6 ma the thus formed phosphatic laminae were frequently subjected to subsequent sediment winnowing and reworking resulting in the formation of condensed phosphatic beds calculated p c molar ratios suggest that 1 the measured section is highly enriched in phosphorus p relative to oc 2 regeneration of organic p from organic matter decomposition was negligible and 3 the source of p was external likely upwelled bottom water rich in inorganic p in spite of good preservation conditions and correspondingly high toc contents the overall oc accumulation rates are moderate in comparison to those of actual high productivity areas which is mainly due to the episodic character of depositional processes and the intervening long periods of nondeposition and sediment reworking they preclude this section and by extrapolation the monterey formation in general from being an important oc sink during the middle miocene alternatively large oc sinks were probably created on the continent lignite deposits and in sedimentary depocenters which received increasing amounts of detrital sediments due to a combination of climate change spreading of grasslands and the increasing importance of mountain chains such as the himalaya the associated high nutrient fluxes may have been involved in the backstepping and drowning of carbonate platforms and in the generation of widespread phosphat rich deposits during the late early and early middle miocene

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

authigenic p formation and reactive p burial in sediments of the nazare canyon on the iberian margin ne atlantic profiles of different forms of sedimentary phosphorus were measured at four sites at the iberian margin ne atlantic which were chosen on the basis of differences in depositional environment a shelf site 113 m a mid slope station 1387 m and two stations at the head 396 m and base 3097 m of the nazarecanyon the sediment was sequentially extracted for fe bound p carbonate fluorapatite cfa biogenic p caco3 bound p and detrital ca p and non sequentially for total p and inorganic p where the difference between total and inorganic p was assumed to be organic p measurements of organic carbon and nitrogen citrate dithionite bicarbonate and citrate ascorbate bicarbonate extractable fe carbon oxidation rates fe reduction rates phosphate effluxes and sedimentation rates were used to quantify the cycling and burial of phosphorus at each site cfa formation was observed only in sediments of the nazarecanyon where enhanced rates of organic matter decomposition and fe reduction provided the necessary conditions the concentrations of reactive p were similar at all sites but the sediment accumulation rates differed greatly the high bulk accumulation rate at the base of the canyon results in a reactive p burial rate exceeding those estimated for continental margins including the iberian margin by an order of magnitude the estimated p burial efficiency is smallest at the slope station 3 24 reasonably high 63 86 at the shelf and head of the canyon stations and extremely high s 97 at the base of the canyon we propose that local depositories such as those at the base of canyons may be key sites for reactive p burial 2002 elsevier science b all rights reserved

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

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

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

early marine lithification and hardground development on a miocene ramp maiella italy key surfaces to track changes in trophic resources in nontropical carbonate settings abstract phosphatic and carbonate hardgrounds occur in a lower miocene nontropical carbonate succession in the maiella carbonate platform margin located in the central apennines multiple diagenetic events occurred at or near the sea floor before the deposition of the overlying sediment and included precipitation of inclusion rich calcite micrite iron oxides and phosphates later diagenetic features are limited to chemical compaction and precipitation of clear calcite cement we relate the development of these features to a two step model involving progressive intensification of upwelling on this carbonate margin which was triggered by regional changes in water circulation and modulated by sea level changes leading initially to precipitation of inclusion rich calcite with an increase in trophic resources related to the paleoceanographic conditions on the ramp increased flux of organic matter to the sea floor led to temporary formation of microbial biofilms these conditions were associated with extensive precipitation of micrite and phosphate microspherules in the uppermost sediment the lack of sedimentation provides the precondition to accumulate and preserve evidence for organic matter utilization in the uppermost sediment layer our study suggests that hardgrounds in nontropical carbonates might be used as indicators of circulation changes and can provide a useful link to major environmental changes in the ocean margin environment the occurrence of microbial micrite and phosphate microspherules precipitated in the absence of sedimentation near the sea floor as a response to higher nutrient supply provides a new and important criterion to differentiate nontropical carbonate facies deposited under the influence of higher nutrient supplies rather than temperature alone furthermore our study shows that local depletion in 13c at a key stratigraphic surface does not necessarily reflect meteoric exposure but may be related to microbial activity at the sea floor

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

the phosphorus cycle phosphogenesis and marine phosphate rich deposits abstract phosphorus in the form of phosphate is an essential nutrient and energy carrier on many different levels of life and a key element in mediating between living and lifeless parts of the biosphere one of the most important aspects of the phosphorus cycle is its vital role in governing productivity thereby interacting with the exogenic part of the carbon cycle which in turn is important in regulating earth s climate phosphorus is a prime element to be traced in earth s history because it allows for the reconstruction of long term feedback mechanisms between climate environment and ecology and of global change as such marine sedimentary phosphate deposits are particularly suited to study aspects of the phosphorus cycle because in the case of ubiquity their origin may result from a general acceleration of the global phosphorus cycle sources of sedimentary phosphate are microbial breakdown of buried organic matter and redox driven phosphate desorption from iron and manganese oxyhydroxides dissolved sea water phosphate represents an additional source which may become important in the formation of phosphatic hardgrounds the main locus of phosphogenesis is near the sediment water interface but phosphogenesis also occurs at greater sediment depths current induced winnowing and transport processes along the sea floor concentrate phosphate precipitates into deposits which exhibit internal stratification patterns typical for the prevailing hydraulic energy regime in a sequence stratigraphic context phosphate deposits preferentially occur along marine or maximum flooding surfaces consequent sedimentary reworking may result in the transfer of phosphates to highstand or lowstand deposits bio chemical weathering on continents represents the most significant source of bioavailable phosphorus this implies that long term changes in marine phosphorus levels and with these changes in marine ecology productivity rates and ratios of exported carbonate carbon and organic carbon are a response to changes in continental weathering rates a compilation of marine sedimentary phosphorus burial rates for the last 160 myr suggests that natural variations have occurred that span one order of magnitude for the late jurassic cretaceous and most of the paleogene the phosphorus cycle appears to have been accelerated in times of climate warming which was most likely due to the spreading of zones of humid climate and more intense continental weathering in the neogene the phosphorus cycle appears to have responded to changes in glacially induced weathering this suggests that uniform interpretations with respect to the emplacement of major phosphorite deposits should be treated with caution integrated analyses of the sedimentary and biogeochemical context of phosphorite occurrences may help to identify paleoenvironmental conditions as well as to improve our understanding of periods of enhanced phosphate accumulation periods which were usually characterized by steep gradients in the development of climate and environment with regard to the complexity of feedback mechanisms between the phosphorus cycle and the biosphere the present day input rates of phosphate into the world s oceans should be of great concern they are more than doubled by anthropogenic means and affect ecological systems on a rapidly increasing scale

the monterey event in the mediterranean a record from shelf sediments of malta oligo miocene carbonate platform and shelf sediments outcropping on the maltese islands provide an excellent archive of the paleoceanography of the central mediterranean a sequence of shallow water limestones than shelf limestones and marls followed again by shallow water limestones reflects drowning of a carbonate platform the establishment of a shelf environment and in the late miocene renewed progradation and aggradation of shallow water carbonates the sequence recording the deepening of the maltese platform contains several phosphorite hardgrounds and phosphorite pebble beds these phosphorites were dated with strontium isotopes major episodes of phosphogenesis occurred between 25 and 16 ma and they are coeval with those phosphorite events reported from florida and north carolina a miocene carbon isotope and oxygen isotope stratigraphy was established on planktic and benthic foraminifera and on bulk samples a major carbon isotope excursion with an amplitude of up to l between 18 and 12 5 ma can be correlated with the globally recognized monterey carbon isotope excursion this is the first record of this event both in shallow water sediments and in the mediterranean the carbon isotope excursion precedes an oxygen isotope excursion which also was recognized in deep sea records major episodes of phosphogenesis and platform drowning preceded the carbon isotope excursion by up to millions of years

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

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

rare earth elements 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

visualizing fossilization using laser ablation inductively coupled plasma mass spectrometry maps of trace elements in late cretaceous bones elemental maps generated by laser ablation inductively coupled plasma mass spectrometry la icp ms provide a previously unavailable high resolution visualization of the complex physicochemical conditions operating within individual bones during the early stages of diagenesis and fossilization a selection of la icp ms maps of bones collected from the late cretaceous of montana united states and madagascar graphically illustrate diverse paths to recrystallization and reveal unique insights into geochemical aspects of taphonomic history some bones show distinct gradients in concentrations of rare earth elements and uranium with highest concentrations at external bone margins others exhibit more intricate patterns of trace element uptake related to bone histology and its control on the flow paths of pore waters patterns of element uptake as revealed by la icp ms maps can be used to guide sampling strategies and call into question previous studies that hinge upon localized bulk samples of fossilized bone tissue la icp ms maps also allow for comparison of recrystallization rates among fossil bones and afford a novel approach to identifying bones or regions of bones potentially suitable for extracting intact biogeochemical signals

phosphogenesis and active phosphorite formation in sediments from the arabian sea oxygen minimum zone in this study porewater chemistry solid phase analysis and microscopic observations were combined to evaluate phosphogenesis in three boxcores located within the intensive oxygen minimum zone of the arabian sea three parameters namely a decrease of the dissolved phosphate and fluoride concentrations with depth saturation with respect to carbonate fluorapatite and the presence of a solid phase ca phosphate mineral all indicate that phosphogenesis is currently taking place at all three sites authigenic apatite precipitation rates vary between 0 076 and 1 04 molp cm 2 yr 1 and are of the same order of magnitude as reported for other high productivity areas precipitation of an intermediate precursor precedes francolite formation in the continental slope sediments on the karachi margin results of a diagenetic p model indicate that phosphogenesis is induced by high rates of organic matter degradation dissolution of fish debris is likely to provide a substantial additional source of phosphate redox iron cycling does not influence phosphogenesis in these environments model results suggest that sediment mixing is essential in promoting early diagenetic phosphogenesis the highest rate of francolite formation was observed in a boxcore taken on the oman margin where it contributes to the formation of a holocene phosphorite deposit this observation contrasts with previous reports of only old phosphorites in this area phosphorites are presently forming on the oman margin as a result of a deposition of older reworked material from the continental shelf which has undergone an earlier phase of phosphogenesis b a high input of reactive p fish debris and degradable organic matter c a relatively low sediment accumulation rate and d the absence of winnowing on this location holocene phosphorite deposits may be less common on the oman margin than in other coastal upwelling areas because of the narrowness of the shelf and the steepness of the slope which limit the area where phosphorite formation may occur

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

the impact of transport processes on rare earth element patterns in marine authigenic and biogenic phosphates abstract rare earth elements rees are commonly used proxies to reconstruct water chemistry and oxygen saturation during the formation of authigenic and biogenic phosphates in marine environments in the modern ocean rees exhibit a distinct pattern with enrichment of heavy rees and strong depletion in cerium ce the wide range of ree enrichment patterns found in ancient marine phosphates lead to the proposition that water chemistry has been very different in the earth s past however both early and late diagenesis are known to affect ree signatures in phosphates altering primary marine signals herein we present a dataset of ree signatures in 38 grain specific la icp ms measurements of isolated phosphate and carbonate grains in three discrete rock samples the phosphates mainly consist of authigenic phosphates and phosphatized microfossils that formed in a microbially mediated micro milieu in addition isolated biogenic and reworked phosphatic grains are also present the phosphates are emplaced in bioclastic grain to packstones deposited on a carbonate ramp setting in the central mediterranean sea during the middle miocene monterey event the results reveal markedly different ree patterns normalized to the post archean australian shale standard in terms of total enrichment and pattern shape analyses of ree diagenesis proxies show that diagenetic alteration affected the samples only to a minor degree grain shape and ree patterns together indicate that authigenic biogenic and reworked phosphates have distinct ree patterns irrespective of the sample our study shows that while ree patterns in phosphates do reflect water chemistry during authigenesis they are often already heavily altered during reworking a process which can occur in geologically negligible timespans ree patterns are therefore more likely to reflect complex enrichment processes after their formation similarities in the ree patterns of reworked and biogenic phosphate further suggest that the frequently observed hat shaped pattern in biogenic phosphates can result from increased middle ree neodymium to holmium scavenging during taphonomic processes prior to final deposition cluster analysis coupled with sedimentological and previously published geochemical data bulk carbon isotope and x ray fluorescence spectrometry allowed the characterization of ree patterns of phosphates in terms of their formation conditions and depositional history such as the distinction of phosphates formed in situ from reworked and transported phosphate grains

phosphorus accumulation in marine sediments and the oceanic phosphorus cycle ideas about key factors in the oceanic mass balance of dissolved reactive phosphate have changed substantially i present an integrated overview of these here with an emphasis on evaluating the burial sinks for p and defining areas needing further research the major source of reactive p to the ocean is river input reactive p is delivered to the oceanic sediment water interface primarily in particulate organic matter p scavenged by hydrothermal iron rich oxyhydroxide particles with uptake in proportion to deep water phosphate concentrations represents a substantially smaller flux to the sediment water interface diagenetic transformations are important influences on the form of reactive p burial in marine sediments p burial occurs with organic carbon burial and as p associated with iron rich oxyhydroxide particles and coatings formation of authigenic p rich phases presumably apatite at the expense of organic p and oxide associated p is significant in open ocean marine sediments the authigenic p sink may represent a substantially larger portion of the sedimentary burial than indicated by previous estimates focused on p burial in organic rich continental margin sediments

global perturbation of the carbon cycle at the onset of the miocene climatic optimum the miocene climatic optimum mco ca 17 14 7 ma represents one of several major interruptions in the long term cooling trend of the past 50 m y to date the processes driving high amplitude climate variability and sustaining global warmth during this remarkable interval remain highly enigmatic we present high resolution benthic foraminiferal and bulk carbonate stable isotope records in an exceptional continuous carbonate rich sedimentary archive integrated ocean drilling program site u1337 eastern equatorial pacific ocean which offer a new view of climate evolution over the onset of the mco a sharp decline in delta o 18 and delta c 13 at ca 16 9 ma contemporaneous with a massive increase in carbonate dissolution demonstrates that abrupt warming was coupled to an intense perturbation of the carbon cycle the rapid recovery in delta c 13 at ca 16 7 ma similar to 250 k y after the beginning of the mco marks the onset of the first carbon isotope maximum within the long lasting monterey excursion these results lend support to the notion that atmospheric pco 2 variations drove profound changes in the global carbon reservoir through the mco implying a delicate balance between changing co2 fluxes rates of silicate weathering and global carbon sequestration comparison with a high resolution delta c 13 record spanning the onset of the cretaceous oceanic anoxic event 1a similar to 120 m y ago reveals common forcing factors and climatic responses providing a long term perspective to understand climate carbon cycle feedbacks during warmer periods of earth s climate with markedly different atmospheric co2 concentrations

rare earth element geochemistry of oceanic ferromanganese nodules and associated sediments abstract analyses have been made of ree contents of a well characterized suite of deep sea 4000 m principally todorokite bearing ferromanganese nodules and associated sediments from the pacific ocean ree in nodules and their sediments are closely related nodules with the largest positive ce anomalies are found on sediments with the smallest negative ce anomalies in contrast nodules with the highest contents of other rare earths 3 ree are found on sediments with the lowest 3 ree contents and vice versa 143 nd 144 nd ratios in the nodules 0 51244 point to an original seawater source but an identical ratio for sediments in combination with the ree patterns suggests that diagenetic reactions may transfer elements into the nodules analysis of biogenic phases shows that the direct contribution of plankton and carbonate and siliceous skeletal materials to ree contents of nodules and sediments is negligible inter element relationships and leaching tests suggest that ree contents are controlled by a p rich phase with a ree pattern similar to that for biogenous apatite and an fe rich phase with a pattern the mirror image of that for sea water it is proposed that 3 ree concentrations are controlled by the surface chemistry of these phases during diagenetic reactions which vary with sediment accumulation rate processes which favour the enrichment of transition metals in equatorial pacific nodules favour the depletion of 3 ree in nodules and enrichment of 3 ree in associated sediments in contrast ce appears to be added both to nodules and sediments directly from seawater and is not involved in diagenetic reactions

the development of middle rare earth element enrichments in freshwaters weathering of phosphate minerals abstract many phosphatic minerals of biogenic authigenic and diagenetic origin are distinguished by rare earth element ree compositions which have a well developed middle rare earth element mree enrichment defined by a gradual increase in the shale normalized ratios of ree toward the middle of the ree series la to lu also the ree composition of dissolved matter in the waters of the amazon fly and sepik rivers as well as other river lake and ground waters have well developed mree enrichments the development of mree enrichments was studied through a series of leaching experiments using river bank sediments from the amazon fly sepik and mississippi rivers a well characterized phosphate mineral rich shale with a pronounced mree enrichment in its bulk composition was also leached in order to better assess the relationship between the weathering of phosphate minerals and the formation of mree enriched solutions the two leaching solutions per sediment consisted of filtered lake water at ph 5 and the same water adjusted to ph 2 leaching experiments with the four river sediments result in extensive fractionation whereby the ree compositions of the solutions develop mree enrichments from starting sediments that show no mree enrichments the ph 2 leachates have much higher concentrations of the ree and more fully developed mree enrichments than do the ph 5 leachates the mree enrichments at ph 2 usually form within an hour of starting the experiments the phosphatic shale results show that there is preferential release of large amounts of mree at ph 5 as well as at ph 2 demonstrating the weather ability of the phosphatic minerals at phs of natural freshwaters the sepik river ph 5 experiment also shows significant mree enrichment under near neutral conditions the development and retention of the mree enrichments in the leaching solutions is accompanied by an increase in dissolved phosphate concentrations although the magnitudes of the mree enrichment do not directly correlate with the percent of phosphate released the experimental data suggest that the preferential dissolution of phosphatic minerals during weathering can result in extensive ree fractionation between bulk river sediment and water leading to freshwaters with mree enrichments

origin and age of phosphorite from the south central florida platform relation of phosphogenesis to sea level fluctuations and δ13c excursions abstract francolite carbonate fluorapatite from predominantly peloidal phosphorite grains in the miocene hawthorn group from the babcock deep core southwestern florida is highly substituted with an average composition of ca4 61na0 22mg0 14k0 05sr0 02 po4 2 23 co3 0 62 so4 0 12 f 1 04 13c values of 1 0 7 8 pdb of the francolite co3 indicate a substantial contribution of c from an organic source the sulfur isotopic composition of francolite so4 is depleted to slightly enriched relative to miocene seawater and suggests that phosphogenesis occurred during early burial diagenesis in organicrich sediments above or in the zone of sulfate reduction the uniformly high sr na mg so4 and co3 contents of the francolite the 18o values of the francolite co3 0 2 4 2 pdb and the inclusion of pyrite and organic matter in phosphorite grains suggest that the francolite has had minimal chemical alteration since its formation phosphorite from the babcock deep core has sr 87 86 ratios that range from 0 708148 0 708880 and sr derived ages that range from late oligocene 25 6 0 7 ma to early late miocene 9 2 1 4 ma the sr derived ages of relatively fragile calcareous benthic foraminifers are consistently younger than associated hard tightly cemented phosphorite and support textural evidence of extensive reworking the age of the host sediment ranges from early miocene to pliocene and its depositional history is related to sea level fluctuations approximately three quarters of the total phosphorite in the babcock deep core formed during or within 2 my before the major early to mid miocene positive 13cshift as recorded at dsdp site 588 southwest pacific one third of the total phosphorite formed just prior to the carbon shift in the short interval between 21 9 and 20 4 ma these results indicate that reworked phosphorite deposits may provide a proxy of organic carbon cycling on continental shelves that correspond to sealevel fluctuations and to variations in the 13crecord

rare earth geochemistry of phosphorites abstract the abundance of rare earth elements ree s in francolite increases with increasing age as a result of post depositional enrichment abundances are higher in pelletal samples than in non pelletal ones because the higher surface mass ratio of pelletal francolite promotes enrichment during diagenesis onshore francolite has higher ree abundances than that found offshore distribution patterns in francolite may be similar to those reported for open ocean water or shale depending upon the dominant source of the ree s different patterns result from weathering and deep burial diagenetic modification of the original patterns and abundances negative ce anomalies occur in francolites containing structural sulphur that is isotopically indistinguishable from seawater of the same age zero or positive anomalies occur in francolites which contain sulphur that is isotopically lighter than seawater

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

distribution of rare earth and some trace elements in tertiary phosphorites from the senegal basin and their weathering products abstract the distribution of rare earth and some trace elements is studied in the eocene phosphate deposits of farim saliquinhe lam lam and n diendouri ouali diala from the mauritania senegal guinea basin the depth of weathering varies between the three deposits the strong weathering of lam lam is marked by the leaching of apatites ca phosphate and the appearance of epigenetic crandallites al ca phosphate in the void spaces that have resulted from leaching of apatites and then of crandallites ferruginous and kaolinitic fillings are epigenised in millisites al ca phosphate all the studied phosphates have high ree ba and sr abundances and present shale normalized patterns with a negative ce anomaly of variable intensity clay minerals of sediments smectites and of weathered rocks kaolinites are characterized by low ree and high v zn cu cr sc and zr abundances they have no ce anomaly the comparison of the ree patterns and of the trace element abundances lead to three important conclusions at first the genesis of al ca phosphates is marked by specific leaching of heavy ree relative to the light ones then millisites have a ree abundance and a ce anomaly less pronounced than those of apatites and crandallites they show also v zn cu cr sc and zr abundances like clay minerals these facts can be related to their epigenetic formation from clay minerals last but not least the negative ce anomaly of epigenetic crandallites follows the same trend as in apatites therefore this anomaly cannot constitute a proof of the primary character for apatites if such variations should be related to the paleogeographic setting of studied deposits they must be considered with prudence

carbonaceous and phosphate rich sediments of the miocene monterey formation at el capitan state beach california u s a abstract the organic and phosphate rich interval of the monterey formation at el capitan state beach west of santa barbara california u s a late early to early late miocene in age is composed of a carbonaceous marl toc contents between 1 2 and 23 2 wt with intercalated phosphate rich laminae lenses and layers subordinate lithologies include ash layers dolomitized horizons and siliceous beds we distinguished five lithological units 1 a gray marl unit lacking major phosphate accumulations 16 3 ma average toc content 2 by weight average sedimentation rate 75 m my average toc accumulation rate 0 19 mg cm2 yr 2 a black marl unit including light colored phosphatic laminae lenses and discrete particles 16 3 14 5 ma average toc content 7 5 by weight average sedimentation rate 20 m my average toc accumulation rate 0 19 mg cm2 yr 3 a red marl unit including light colored phosphatic laminae lenses and commonly reworked particles 14 5 12 7 ma average toc content 15 by weight average sedimentation rate 20 m my 14 5 13 3 ma and 2 m my 13 3 12 7 ma respectively average toc accumulation rate 0 39 mg cm2 yr 14 5 13 3 ma and 0 04 mg cm2 yr 13 3 12 7 ma respectively 4 a unit of complex and condensed phosphatic beds interbedded with red marl 12 7 10 8 ma average sedimentation rate 3 m my and 5 a black marl unit with intercalated phosphatic laminae and lenses 10 8 ma average sedimentation rate 9 m my average toc accumulation rate 0 09 mg cm2 yr phosphogenesis and accumulation of phosphate were dynamic processes which started with local phosphogenesis leading to the formation of phosphatized particles as well as stratigraphically bound phosphogenesis leading to the formation of phosphate laminae and lenses phases of subsequent sediment reworking resulted in the concentration of phosphate particles in phosphate rich layers and repeated phases of sediment reworking and phosphogenesis ultimately resulted in the formation of the complex phosphate condensed horizons preservation of organic matter was favored by high productivity rates and by the development of dysaerobic bottom water conditions the dynamic sedimentary environment likely led to the formation of early diagenetic phosphatic lids which may have sealed off subjacent organic rich layers as well as to the rapid deposition of entire layers in the form of mud flows thereby eventually enhancing the potential of organic matter preservation our new age data suggest that at the el capitan state beach section the intervals characterized by high toc values and maximum toc accumulation rates red marl as well as significant quantities of in situ phosphates appeared in the late middle miocene i e during and after the major cooling phase at around 14 5 ma this implies that deposition of phosphate and organic carbon continued well after this cooling phase thereby underlining the observation that preservation of organic carbon in the monterey formation is not only dependent on climate change during the mid miocene but also on regional conditions

orbitally paced climate evolution during the middle miocene monterey carbon isotope excursion one of the most enigmatic features of cenozoic long term climate evolution is the long lasting positive carbon isotope excursion or monterey excursion which started during a period of global warmth after 16 9 ma and ended at similar to 13 5 ma approximately 400 kyr after major expansion of the antarctic ice sheet we present high resolution 1 9 kyr astronomically tuned climate proxy records in two complete sedimentary successions from the northwestern and southeastern pacific odp sites 1146 and 1237 which shed new light on the middle miocene carbon isotope excursion and associated climatic transition over the interval 17 1 12 7 ma we recog nize three distinct climate phases with different imprints of orbital variations into the climatic signals 1146 and 123 7 delta 18 o delta 13 c 1237 xrt fe fraction 63 pm 1 climate optimum prior to 14 7 ma characterized by minimum ice volume and prominent 100 and 400 kyr variability 2 long term cooling from 14 7 to 13 9 ma principally driven by obliquity and culminating with rapid cryosphere expansion and global cooling at the onset of the last and most pronounced delta 13 c increase 3 icehouse mode after 13 9 ma with distinct 100 kyr variability and improved ventilation of the deep pacific the monterey carbon isotope excursion 16 9 13 5 ma consists overall of nine 400 kyr cycles which show high coherence with the long eccentricity period superposed on these low frequency oscillations are high frequency variations 100 kyr which closely track the amplitude modulation of the short eccentricity period in contrast to delta 13 c the delta 18 o signal additionally shows significant power in the 41 kyr band and the 1 2 myr amplitude modulation of the obliquity cycle is clearly imprinted in the 1146 delta 18 o signal our results suggest that eccentricity was a prime pacemaker of middle miocene climate evolution through the modulation of long term carbon budgets and that obliquity paced changes in high latitude seasonality favored the transition into the icehouse climate c 2007 elsevier b v all rights reserved