incorporation of ca isotopes in carapaxes of marine ostracods abstract we studied mg ca sr ca and ca isotope ratios of ostracod carapaxes from surface sediments retrieved during research cruises to the southern and equatorial eastern atlantic collected specimens originate from water depth between 30 and about 5000 mbsl and cover bottom water temperatures between 0 and 23 c analysed taxa include buntonia sp cytherella sp henryhowella sp krithe sp poseidonamicus sp and ruggieria sp calcium isotope ratios of the studied specimens are in the overall range of other marine calcifiers and show a variability of about 0 75 over a temperature range of 20 c there is no overall linear relation between temperature and ca isotope fractionation but some species show a maximum 44 40ca at intermediate temperatures mg ca and sr ca agree well with values of previously published carapaxes demonstrating large inter and intra species variability and different responses to bottom water temperatures magnesium is highly variably distributed within the carapax with mg enrichment in the inner part of the shell of most taxa this enrichment is independent from the incorporation of sr which shows less variability within the carapax the ca isotope vs sr ca systematic in the ostracods deviates from inorganic calcite and foraminifers the ostracod array is most likely controlled by either mixing of material originating from a precursor phase and newly grown calcite or rayleigh type fractionation during precipitation from a restricted fluid reservoir indicating varying degrees of ca and sr consumption during calcite precipitation the different slope of the ca isotope vs sr ca relation shown by the ostracods compared to those of inorganic calcite and foraminifers opens a new approach for the determination of ca isotope and sr ca ratios of past ocean water

reconstructing past seawater mg ca and sr ca from mid ocean ridge flank calcium carbonate veins proxies for past seawater chemistry such as mg ca and sr ca ratios provide a record of the dynamic exchanges of elements between the solid earth the atmosphere and the hydrosphere and the evolving influence of life we estimated past oceanic mg ca and sr ca ratios from suites of 1 6 to 170 million year old calcium carbonate veins that had precipitated from seawater derived fluids in ocean ridge flank basalts our data indicate that before the neogene oceanic mg ca and sr ca ratios were lower than in the modern ocean decreased ocean spreading since the cretaceous and the resulting slow reduction in ocean crustal hydrothermal exchange throughout the early tertiary may explain the recent rise in these ratios

interlaboratory study for coral sr ca and other element ca ratio measurements the sr ca ratio of coral aragonite is used to reconstruct past sea surface temperature sst twenty one laboratories took part in an interlaboratory study of coral sr ca measurements results show interlaboratory bias can be significant and in the extreme case could result in a range in sst estimates of 7 c however most of the data fall within a narrower range and the porites coral reference material jcp 1 is now characterized well enough to have a certified sr ca value of 8 838 mmol mol with an expanded uncertainty of 0 089 mmol mol following international association of geoanalysts iag guidelines this uncertainty at the 95 confidence level equates to 1 5 c for sst estimates using porites so is approaching fitness for purpose the comparable median within laboratory error is 0 5 c this difference in uncertainties illustrates the interlaboratory bias component that should be reduced through the use of reference materials like the jcp 1 there are many potential sources contributing to biases in comparative methods but traces of sr in ca standards and uncertainties in reference solution composition can account for half of the combined uncertainty consensus values that fulfil the requirements to be certified values were also obtained for mg ca in jcp 1 and for sr ca and mg ca ratios in the jct 1 giant clam reference material reference values with variable fitness for purpose have also been obtained for li ca b ca ba ca and u ca in both reference materials in future studies reporting coral element ca data should also report the average value obtained for a reference material such as the jcp 1

possible evidence for a large decrease in seawater strontium calcium ratios and strontium concentrations during the cenozoic article i nfo few constraints exist on the major element chemistry of ancient oceans turritellid marine snails precipitate aragonitic shells and are abundant in the cenozoic fossil record and therefore may be ideal for reconstructing past seawater chemistry here we report strontium to calcium sr ca ratios of modern and early cenozoic turritellid shells that still retain an aragonitic mineralogy by applying partition coefficients determined from modern specimens to data for paleocene and eocene shells we calculate paleo seawater sr ca values the high sr ca values recorded in fossil shells may imply that seawater sr ca ratios varied from at least 9 5 15 2 mmol mol much higher than modern average seawater values 8 6 mmol mol high paleo seawater sr ca ratios may indicate that substantial changes in the biogeochemical cycling of sr have occurred over the past 37 million years a decrease in seawater strontium concentrations could have arisen from an increase in the proportion of weathered radiogenic silicate rocks relative to carbonates reducing the riverine flux of strontium to the oceans or changes in the exposure and erosion of aragonitic carbonates on tropical shelves due to variations in sea level

mg ca sr ca and ca isotope ratios in benthonic foraminifers related to test structure mineralogy and environmental controls we analysed mg ca sr ca and ca isotope ratios of benthonic foraminifers from sediment core tops retrieved during several research cruises in the atlantic ocean in order to improve the understanding of isotope fractionation and element partitioning resulting from biomineralisation processes and changes in ambient conditions species include foraminifers secreting tests composed of hyaline low magnesium calcite porcelaneous high magnesium calcite as well as aragonite our results demonstrate systematic isotope fractionation and element partitioning patterns specific for these foraminiferal groups calcium isotope fractionation is similar in porcelaneous and hyaline calcite tests and both groups demonstrate the previously described anomaly with enrichment of heavy isotopes around 3 4 degrees c gussone and filipsson 2010 calcium isotope ratios of the aragonitic species hoeglundina elegans on the other hand are about 0 4 parts per thousand lighter compared to the calcitic species which is in general agreement with stronger fractionation in inorganic aragonite compared to calcite however the low and strongly variable sr content suggests additional processes during test formation and we propose that transmembrane ion transport or a precursor phase to aragonite may be involved porcelaneous tests composed of high mg calcite incorporate higher amounts of sr compared to hyaline low mg calcite in agreement with inorganic calcite systematics but also porcelaneous tests with reduced mg ca show high sr ca while calcium isotopes sr ca and mg ca in benthonic foraminifers primarily appear to fractionate and partition with a dominant inorganic control delta ca 44 40 temperature and growth rate dependencies of benthonic foraminifer tests favour a dominant contribution of light ca by transmembrane transport relative to unfractionated seawater ca to the calcifying fluid thus controlling the formation of foraminiferal delta ca 44 40 and sr ca proxy signals c 2015 elsevier ltd all rights reserved less

calcium isotope fractionation in ikaite and vaterite abstract we investigated the isotopic composition of calcium in the metastable calcium carbonate polymorphs vaterite and ikaite the synthetic vaterite precipitates show a smaller degree of ca isotope fractionation than calcite or aragonite at comparable temperatures and revealed no significant temperature sensitivity between 10 and 50 c ikaite the water bearing ca carbonate modification caco 3 6h 2 o was precipitated at 2 c in controlled laboratory experiments and in addition recovered from marine sediments and sea ice synthetic and natural ikaites show similar values of ca isotope fractionation in general ikaite is less depleted in heavy isotopes compared to calcite or aragonite at low temperatures the observed offset of vaterite and ikaite to calcite or aragonite precipitated at similar temperatures is presumably mainly related to differences in precipitation rates and regimes which seem however to be typical for the growth of these carbonate minerals small differences in ca isotope ratios of naturally formed ikaites from different locations seem to be related to different geochemical conditions in the respective sediment settings

dem analysis of soil fabric effects on behaviour of sand s yimsiri and k soga 2010 geotechnique 60 no 6 483 495

calcium isotope ratios in calcitic tests of benthic foraminifers abstract we analysed ca isotope ratios of the infaunal foraminiferal species cassidulina laevigata elphidium spp gyroidinoides spp and uvigerina peregrina as well as the epifaunal cibicidoides wuellerstorfi over a depth temperature gradient the calcium isotope ratios of the benthic foraminifers tests show a distinct anomaly around 4 c this anomaly is observed in both epi and infaunal species but there are also characteristic differences between both the 44 40 ca characteristics of benthic foraminifers may be explained by the interference of temperature and carbonate chemistry of the fluid on ca isotope fractionation we suggest that ca isotope composition of benthic foraminifer tests is dominantly controlled by temperature at temperatures higher than 5 c while in the temperature range below 5 c calcite saturation cc becomes an increasingly important controlling factor due to the non linear shape of the cc 44 40 ca relation of actively transported calcium the potential applicability of ca isotope ratios in benthic foraminifers for reconstruction of either temperatures or 44 40 ca sw is limited by the complex fractionation pattern below 5 c however due to the minor temperature dependence in the temperature range above 5 c benthic foraminifers might provide a possible alternative archive for 44 ca sw avoiding some uncertainties associated with planktic records relocation habitat calcification depth short time climate variability as long as a defined bottom water temperature above 5 c can be secured

north atlantic deepwater temperature change during late pliocene and late quaternary climatic cycles variations in the ratio of magnesium to calcium mg ca in fossil ostracodes from deep sea drilling project site 607 in the deep north atlantic show that the change in bottom water temperature during late pliocene 41 000 year obliquity cycles averaged 1 5 c between 3 2 and 2 8 million years ago ma and increased to 2 3 c between 2 8 and 2 3 ma coincidentally with the intensification of northern hemisphere glaciation during the last two 100 000 year glacial to interglacial climatic cycles of the quaternary bottom water temperatures changed by 4 5 c these results show that glacial deepwater cooling has intensified since 3 2 ma most likely as the result of progressively diminished deepwater production in the north atlantic and of the greater influence of antarctic bottom water in the north atlantic during glacial periods the ostracode mg ca data also allow the direct determination of the temperature component of the benthic foraminiferal oxygen isotope record from site 607 as well as derivation of a hypothetical sea level curve for the late pliocene and late quaternary the effects of dissolution on the mg ca ratios of ostracode shells appear to have been minimal

ostracode mg ca paleothermometry in the north atlantic and arctic oceans evaluation of a carbonate ion effect 1 the reconstruction of deep sea bottom water temperature bwt is important to assess the ocean s response to and role in orbital and millennial scale climate change deep sea paleothermometry employs magnesium to calcium mg ca ratios in calcitic benthic microfaunas foraminifera ostracodes as a primary proxy method mg ca paleothermometry may however be complicated by bottom water carbonate ion chemistry which might affect mg ca ratios in shells to address temperature and carbonate ion influence on mg ca ratios we studied mg ca ratios in the benthic ostracode genus krithe in the north atlantic and arctic oceans using a 686 specimen core top collection including 412 previously unpublished analyses mg ca ratios are positively correlated to temperature in multiple species from the north atlantic bwt 0 885 mg ca 5 69 r2 0 73 and for k glacialis in the arctic ocean and nordic seas bwt 0 439 mg ca 5 14 r2 0 50 consistent with previously published calibrations we found no evidence for a relationship between krithe mg ca and carbonate ion saturation in the north atlantic ocean nordic seas and arctic ocean supporting the use of krithe mg ca for reconstructing past bwt

calcium isotope fractionation during coccolith formation in emiliania huxleyi independence of growth and calcification rate 1 recently calcium isotope fractionation in the coccolithophore emiliania huxleyi was shown to exhibit a significant temperature dependency an important subsequent question in this context is whether the observed fractionation patterns are caused by temperature itself or related growth rate changes in order to separate growth and calcification rate effects from direct temperature effects batch culture experiments with the coccolithophore e huxleyi were conducted under varying light intensities despite large changes in cellular growth and calcification rates calcium isotope fractionation remained constant independence of calcium isotope fractionation on growth and calcification was also obtained in two additional sets of experiments in which growth rates changed in response to varying calcium concentration and seawater salinity these experiments also showed no direct effects of calcium concentration and salinity on calcium isotope fractionation values for calcium isotope fractionation of e huxleyi coccoliths fell within a range of 1 0 to 1 6 1000 ln confirming earlier results this range is similar to that observed in several foraminiferal species and coccolith oozes suggesting a rather homogeneous calcium isotopic composition in marine biogenic calcite our data further show that the calcium isotope fractionation does not change with changing isotopic composition of seawater this is a basic requirement for reconstructing the calcium isotopic composition of the ocean over time

calcium isotope fractionation in coccoliths of cultured calcidiscus leptoporus helicosphaera carteri syracosphaera pulchra and umbilicosphaera foliosa four species of marine calcifying algae the coccolithophores calcidiscus leptoporus helicosphaera carteri syracosphaera pulchra and umbilicosphaera foliosa were grown in laboratory cultures under temperatures varying between 14 and 23 c and one species c leptoporus under varying co32 ranging from 105 to 219 mol kg calcium isotope compositions of the coccoliths resemble in both absolute fractionation and temperature sensitivity previous calibrations of marine calcifying species e g emiliania huxleyi coccolithophores and orbulina universa planktonic foraminifera as well as inorganically precipitated caco3 but also reveal small species specific differences in contrast to inorganically precipitated calcite but similar to e huxleyi and o universa the carbonate ion concentration of the medium has no statistically significant influence on the ca isotope fractionation of c leptoporus coccoliths however combined data of e huxleyi and c leptoporus indicate that the observed trends might be related to changes of the calcite saturation state of the medium since coccoliths constitute a significant portion of the global oceanic caco3 export production the ca isotope fractionation in these biogenic structures is important for defining the isotopic composition of the ca sink of the ocean one of the key parameters for modelling changes to the marine ca budget over time for the present ocean our results are in general agreement with the previously postulated and applied mean value of the oceanic ca sink sed of about 1 3 but the observed inter and intra species differences point to possible changes in sed through earth history due to changing physico chemical conditions of the ocean and shifts in floral and faunal assemblages

cellular calcium pathways and isotope fractionation in emiliania huxleyi the marine calcifying algae emiliania huxleyi coccolithophores was grown in laboratory cultures under varying conditions with respect to the environmental parameters of temperature and carbonate ion concentration co32 concentration the ca isotope composition of e huxleyi s coccoliths reveals new insights into fractionation processes during biomineralization the temperature dependent ca isotope fractionation resembles previous calibrations of inorganic and biogenic calcite and aragonite unlike inorganically precipitated calcite the co32 concentration of the medium has no significant effect on the ca isotope composition of the coccoliths these results indicate a decoupling of the chemical properties of the bulk medium and the calcifying vesicle cellular ca pathways of e huxleyi indicate that fractionation cannot occur at the crystal surface as occurs during inorganic precipitation the dominant processes leading to the observed ca isotope fractionation pattern in e huxleyi are most likely the dehydration of the ca aquocomplex at the plasma membrane and the attachment of dissolved ca to proteins of ca channels the independence of ca isotope fractionation from co32 and the small temperature dependence of e huxleyi are also important for defining the isotopic signature of the oceanic ca sink since coccolithophores contribute to about half the global caco3 production a relatively uniform isotopic composition of the oceanic ca sink is further supported

a global evaluation of temperature and carbonate ion control on mg ca ratios of ostracoda genus krithe 1 improving estimates of past ocean temperatures is paramount to our understanding of ocean circulation and its role in climate change magnesium calcium mg ca ratios of carapaces of the benthic ostracod genus krithe were determined from new globally distributed core top samples from the norwegian sea cape hatteras shelf gulf of mexico sulawesi margin indonesia new zealand shelf ceara rise and the north atlantic a linear regression of the krithe mg ca ratios and bottom water temperature bwt reveals a significant correlation for locations where temperature during carapace calcification was above 3 c which can be described by the equation mg ca 0 972 0 152 bwt 7 948 1 103 consistent with previous north atlantic calibrations deviations from the global calibration line below 3 c follow the same pattern observed for benthic foraminifera suggesting that the incorporation of magnesium into ostracodal calcite may be secondarily controlled by changes in carbonate ion concentration therefore we propose a linear regression that describes the relationship between magnesium incorporation temperature and carbonate saturation for low temperatures 3 c mg ca 0 972 0 152 bwt 0 100 0 030 d co3 4 440 1 103 1 se 0 3 c while the standard error of the calibration is small it requires an accurate knowledge of past d co3 concentration which necessitates additional proxy data applying the calibration to glacial samples from the deep north atlantic ocean we show that estimates of bottom water temperatures generated from the new d co3 corrected equations are more consistent with results from oxygen isotopes and pore water studies

influences on the fractionation of calcium isotopes in planktonic foraminifera for paleoceanographic studies it is important to understand the processes that influence the calcium ca isotopic composition of foraminiferal calcite tests preserved in the sediment record seven species of planktonic foraminifera from coretop sediments collectively exhibited a ca temperature dependent fractionation of 0 013 per c thisisin agreement with previously published estimatesformostspecies ofplanktonic foraminifera as well asbiogenicandinorganiccalciteandaragonite fourspeciesofplanktonicforaminiferacollectedfromasedimenttrapshowedaconsiderableamountof scatterandnoconsistenttemperaturedependentfractionation analyzedsizefractionsofcoretopsamplesshownosignificantrelationshipwith 44 40 ca however preliminary results suggest that the symbiotic and spinose foraminifera globigerinoides sacculifer might exhibit a relationship between test size and 44 40 ca a one box model in which ca isotopes are allowed to fractionate by rayleigh distillation from a biomineralization reservoir internal pool was used to constrain the isotopic composition of the original biomineralization ca reservoir assuming around 85 of the ca reservoir is precipitatedandthefractionationfactorduringprecipitationis0 9985 0 00002 t c toexplaintheforaminiferalcaisotopedata thismodelindicates

evaluation of aeolian sand transport equations using intertidal zone measurements saunton sands england sand transport rates were measured using a vertical sand trap along the intertidal zone of a beach in north devon england together with simultaneous monitoring of the wind speed on the beach and moisture levels in the surface layers of sand the results of 88 sand trap samples in a wide range of wind speeds showed that moisture levels up to 14 in the top 1 2 mm of the beach sand have no discernible effect on the transport rates transport rates measured from areas of the beach where the moisture was below this level are compared with the rates predicted by seven expressions based on theoretical and wind tunnel research together with the empirical results of other published research measured transport rates range from 0 0001 to 0 22 kg m 1 s 1 the results indicate that expressions based on a power relation between the wind speed and the transport rate and which include a threshold velocity term provide the best estimates of the observed transport rates

minor element and ca isotope composition of calcareous dinoflagellate cysts of cultured thoracosphaera heimii abstract we investigated the influences of temperature salinity and ph on the calcium isotope as well as trace and minor element uranium strontium magnesium to ca ratios on calcium carbonate cysts of the calcareous dinoflagellate species thoracosphaera heimii grown in laboratory cultures the natural habitat of this species is the photic zone preferentially at the chlorophyll maximum depth of temperate to tropical oceans and it is abundant in deep sea sediments over the entire cenozoic in our experiments temperatures ranged from 12 to 30 c salinity from 36 5 to 38 8 and ph from 7 9 to 8 4 the 44 40ca of t heimii cysts resembles that of other marine calcifiers including coccolithophores foraminifers and corals however its temperature sensitivity is considerably smaller and statistically insignificant and t heimii might serve as a recorder of changes in seawater 44 40ca over geologic time the sr ca ratios of t heimii cysts show a pronounced temperature sensitivity 0 016 mmol mol c 1 and have the potential to serve as a palaeo sea surface temperature proxy no clear temperature and ph dependences were observed for mg ca u ca seems to be influenced by temperature and ph but the correlations change sign at 23 c and ph 8 2 respectively

modern and palaeo oceanographic environments under benguela upwelling cells off southern namibia averaged benthic physical and chemical and key microfaunal ostracoda parameters of the bottom waters and substrate allow a ranking of the intensity of upwelling in the modern cells off southwestern africa b1 b6 b1 namib cell temperature salinity dissolved oxygen total organic matter 10 3 c 34 94 1 2 ml l 6 2 palmoconcha walvisbaiensis cytherella namibensis garciaella knysnaensis robusta and neocaudites lordi b2 walvis cell 11 0 c 35 00 1 0 ml l 9 2 palmoconcha walvisbaiensis cytherella namibensis garciaella knysnaensis robusta buntonia rogersi neocaudites lordi and ruggieria cytheropteroides leeward side only b3 luderitz cell 9 1 c 34 77 1 8 ml l 6 3 palmoconcha walvisbaiensis cytherella namibensis incongruellina venusta kuiperiana angulata and ruggieria cytheropteroides leeward side only b4 namaqua cell 10 0 c 34 82 2 4 ml l 3 1 pseudokeijella lepralioides and ruggieria cytheropteroides b5 columbine cell 8 3 c 34 70 3 1 ml l 3 9 ruggieria cytheropteroides pseudokeijella lepralioides poseidonamicus panopsus and ambostracon a flabellicostata b6 peninsula cell 8 9 c 34 63 3 6 ml l 1 9 pseudokeijella lepralioides ambostracon a keeleri cytherella dromedaria neocytherideis boomeri xestoleberis africana neocaudites osseus coquimba birchi and urocythereis arcana pleistocene palaeo upwelling characteristics of the shelf north west of luderitz are investigated by analysing the ostracod faunas sediment textures and mineralogy of three large volume gravity cores q mode factor analyses using previously published transfer functions allow predictions for benthic environmental parameters during the late pleistocene the area experienced less intense upwelling and lower primary productivity than at present in an environment equated with a modified peninsula cell b6 b7 cell 9 6 c 34 73 3 2 ml l 3 9 neocaudites lordi ambostracon a keeleri bairdoppilata simplex paracypris lacrimata parakrithella simpsoni xestoleberis hartmanni ruggieria cytheropteroides and pseudokeijella lepralioides in middle and early pleistocene late pliocene times the core sites lay closer inshore adjacent to evaporite halite and authigenic phosphorite rich lagoons with a high intensity upwelling walvis like cell b1 to the north west and a low intensity upwelling cell b7 to the south

coccolith strontium to calcium ratios in emiliania huxleyi the dependence on seawater strontium and calcium concentrations in recent studies the sr ca ratio of coccolithophore calcite was used as a proxy for past coccolithophore growth and calcification rates since sr and ca concentrations in seawater have not remained constant through time interpretation of sr ca data from the coccolith dominated sedimentary record requires knowledge about the incorporation of seawater sr into coccolith calcite during coccolithogenesis here we show that sr ca of emiliania huxleyi coccoliths is linearly related to seawater sr ca meaning that the sr exchange coefficient does not change with changing seawater sr ca the exchange coefficient for sr in this study 0 39 is close to values presented in the literature and is high compared with values obtained by inorganic precipitation experiments this suggests a strong effect of cell physiology on biogenic calcite precipitation in coccolithophores we present a conceptual model based on the transmembrane transport of sr and ca which explains the offset

cretaceous calcareous dinoflagellate cysts as recorder of δ44 40caseawater and paleo temperature using sr ca thermometry abstract we evaluate the potential of calcareous dinoflagellates as archives for sr ca based paleo temperature reconstructions and 44 40caseawater fluctuations on sediments from ocean drilling program expedition 113 hole 690c weddell sea southern ocean between 73 and 68 ma sr ca ratios of two cretaceous dinoflagellate species pirumella krasheninnikovii and orthopithonella globosa show a pronounced decrease consistent with a significant drop in sea surface temperature as reflected by the 18o of planktic foraminifers the apparent temperature sensitivity of the dinoflagellate cysts sr ca is 0 06 and 0 08 mmol mol c 1 using 18o derived paleo sea surface temperatures which is significant and large enough to resolve paleoenvironmental temperature changes at current analytical precision as the chemical composition of the cyst calcite appears to have a good preservation the sr ca of calcareous dinoflagellates has a potential to serve as paleo temperature proxy although the chemical composition of the cretaceous seawater and potential impacts on the cyst geochemistry is pending further inspection the ca isotope composition of the two dinoflagellate species shows identical trends of increasing 44 40ca between 73 and 67 ma the planktic foraminifer archaeoglobigerina australis and the benthic foraminifer nuttallides truempyi reveal the same increase of about 0 4 but are offset relative to the dinoflagellates by about 0 5 presumably due to species specific ca isotope fractionation bulk carbonate sediment shows significant scatter likely caused by changes in faunal composition and does not reproduce the trend revealed by the dinoflagellate and foraminifer records these observations demonstrate the importance of taxon specific records and careful determination of fractionation factors of selected archives and highlight complications arising from utilizing less suitable archives such as bulk sediments for 44 40caseawater reconstructions our records indicate strong changes in the marine ca cycle associated with the global temperature decrease towards the end of the cretaceous

negligible temperature dependence of calcium isotope fractionation in 12 species of planktonic foraminifera the influence of temperature on calcium ca isotope fractionation during biomineralization was investigated through the paired analyses of d44 42ca via mc icp ms and d18o on the calcite tests of 12 species of planktonic foraminifera from coretop sediments samples were collected from a suite of box cores from sites between 608n and 308s in the north atlantic and west indian oceans spanning a range in sea surface temperature of 9 27 8c the d44 42casrm915a of the samples ranged from 0 21x to 0 81x over a range in the d18ovpdb of the foraminiferal calcite of between 2 3x and 2 1x the bulk of the species investigated produced calcite with an average calcite seawater ca enrichment factor e of 0 65f0 08x n 45 the globorotaliid species and a single globigerina bulloides sample were confined to the upper 0 4x of the observed range in d44 42ca values with the globorotaliids displaying a lesser degree of fractionation of 0 56f0 23x n 15 possibly as a result of physiological or metabolic processes such as the production of calcite crusts at depth leading to the depletion of internal stores of ca no significant correlation between temperature and ca enrichment factor was observed in any of the 12 species of foraminifera investigated the influence of temperature on e was close to zero for the combined non globorotaliid species 0 07f0 10 k e versus 1000 k 0 0008f0 0012x 8c1 the results suggest that the theoretically expected relationship between the ca enrichment factor and temperature can be obscured by as yet unquantified metabolic and physiological processes in nature these processes are particularly relevant to the globorotaliid species and g bulloides in this core top study consequently their effects must be better understood before laboratory determined temperature calibrations can be applied to downcore material with confidence provided that the effects of metabolic and physiological processes on e remain constant through time orbulina universa globigerinoides sacculifer neogloboquadrina pachyderma and globigerinella aequilateralis are suitable for the investigation of temporal changes in the calcium isotopic composition of seawater

faunal and geochemical evidence for changes in intermediate water temperature and salinity in the western coral sea northeast australia during the late quaternary abstract ostracod assemblages and geochemical analyses of valves of specific ostracod taxa are used to reconstruct both qualitatively and quantitatively bottom water temperatures bwt for the last 100 000 years in the western coral sea the investigated core 51gc21 is situated in the lower reaches of the antarctic intermediate water at 1630 m water depth first we ran a principal coordinate analysis pcoa of 42 surface samples from the coral sea and then compared fossil assemblages with results of the pcoa in addition we selected well preserved speciments of the two genera krithe and bythocypris for mg ca analyses the mg ca is used to infer past changes in bwt for intermediate waters of the western coral sea results indicate large temperature fluctuations over the last 100 000 years of interest is the documentation that the bwt was similar to the present day temperature during part of isotope stage 3 comparison between our temperature record and the benthic foraminifer 18o record of core 51gc21 and with the 18o variations in seawater as reconstructed by labeyrie et al 1987 allowed assessment of past changes in bwt salinity and density thus we identify for the western coral sea three distinct periods on the basis of water mass density changes i e for isotope stage 1 stages 2 3 and 4 and stage 5 our temperature record also indicates a good correlation with the 60 s summer insolation calculations for the period between 25 000 yr b p and 75 000 yr b p comparison of our results from this study with other records from the western pacific the ontong java plateau in particular reveal the role of new guinea as an oceanographic barrier a wet phase recorded on continental australia coincides with our high bottom water temperature record for isotopic stage 3

a cenozoic seawater sr ca record from benthic foraminiferal calcite and its application in determining global weathering fluxes a cenozoic multi species record of benthic foraminiferal calcite sr ca has been produced and is corrected for inter specific offsets typically less than 0 3 mmol mol and for the linear relationship between decreasing benthic foraminiferal sr ca and increasing water depth the water depth correction determined from holocene late glacial maximum and eocene paleowater depth transects is not vert similar0 1 mmol mol km the corrected cenozoic benthic foraminiferal sr ca record ranges from 1 2 to 2 0 mmol mol and has been interpreted in terms of long term changes in seawater sr ca enabling issues related to higher resolution variability in sr ca to be ignored we estimate that seawater sr ca was not vert similar1 5 times modern values in the late cretaceous but declined rapidly into the paleogene following a minimum in the eocene seawater sr ca increased gradually through to the present day with a minimum superimposed on this trend centered in the late miocene by assuming scenarios for changing seawater calcium concentration and using published carbonate accumulation rate data combined with suitable values for sr partition coefficients into carbonates the seawater sr ca record is used to estimate global average river sr fluxes these fluxes are used in conjunction with the seawater strontium isotope curve and estimates of hydrothermal activity tectonic outgassing to calculate changes in global average river 87sr 86sr through the cenozoic the absolute magnitude of sr fluxes and isotopic compositions calculated in this way are subject to relatively large uncertainties nevertheless our results suggest that river sr flux increased from 35 ma to the present day roughly two fold accompanied by an overall increase in 87sr 86sr by not vert similar0 to 0 001 between 75 and 35 ma river 87sr 86sr also increased by not vert similar0 001 to 0 002 but was accompanied by a decrease two to three fold in river sr flux

paleoceanographic events and deep sea ostracodes eight recognized or theorized paleoceanographic events during the past 70 million years were tested against changes in the global deep sea benthic ostracode fauna two events the sudden cretaceous tertiary boundary event at 66 million years ago and the more gradual 40 million year event formation of the psychrosphere show up most dramatically before the 40 million year event ostracodes freely radiated into the deeper water regions but were provincial the development of thermal stratification isolated these deep water taxa mostly the survivors of the cretaceous tertiary boundary event which adapted to a new free flowing but more frigid ecosystem and spread rapidly throughout the world

reconstruction of caribbean sea surface temperature and salinity fluctuations in response to the pliocene closure of the central american gateway and radiative forcing using δ44 40ca δ18o and mg ca ratios the 18o values of planktonic foraminifera increased in the caribbean by about 0 5 relative to the equatorial east pacific values between 4 6 and 4 2 ma as a consequence of the closure of the central american gateway cag this increase in 18o can be interpreted either as an increase in caribbean sea surface mixed layer salinity sss or as a decrease in sea surface temperatures sst this problem represents an ideal situation to apply the recently developed paleotemperature proxy 44 40ca together with mg ca and 18o on the planktic foraminifer globigerinoides sacculifer from odp site 999 although differences in absolute temperature calibration of 44 40ca and mg ca exist the general pattern is similar indicating a sst decrease of about 2 3 c between 4 4 and 4 3 ma followed by an increase in the same order of magnitude between 4 3 and 4 0 ma correcting the 18o record for this temperature change and assuming that changes in global ice volume are negligible the salinity induced planktonic 18o signal decreased by about 0 4 between 4 4 and 4 3 ma and increased by about 0 9 between 4 3 and 4 0 ma in the caribbean the observed temperature and salinity trends are interpreted to reflect the restricted exchange of surface water between the caribbean and the pacific in response to the shoaling of the panamanian seaway possibly accompanied by a southward shift of the intertropical convergence zone itcz between 4 4 and 4 3 ma differences in mg ca and 44 40ca derived temperatures can be reconciled by corrections for secular variations of the marine mg casw and 44 40ca a salinity effect on the mg ca ratio and a constant temperature offset of 2 5 c between both sst proxy calibrations

biological control of calcium isotopic abundances in the global calcium cycle measurements of 44ca 40ca expressed as 44ca were made on igneous rocks and on shell and bone material from modern organisms to investigate the magnitude and origins of calcium isotopic fractionation in nature the results document a span of 4 in 44ca measured with the double spike technique to a precision of 0 15 volcanic rocks including basalt and rhyolite show little variability and cluster near 44ca 0 0 2 systematic analysis of biological samples indicates that biological processing of calcium discriminates against heavy isotopes and that biological fractionation is the primary generator of calcium isotopic fractionation in nature preliminary data suggest that calcium becomes isotopically lighter as it moves through food chains calcium carbonate shells of marine microorganisms and deep sea carbonate ooze have 44ca about 1 0 lower than seawater this fractionation causes seawater to be enriched in heavy calcium 44ca 0 9 relative to igneous rocks marine organisms consequently are isotopically heavier than their terrestrial counterparts at similar trophic level the calcium isotopic composition of living and fossil organisms may record information on diet and environment

orbital and suborbital variability in north atlantic bottom water temperature obtained from deep sea ostracod mg ca ratios abstract magnesium calcium mg ca ratios were measured in the deep sea ostracod crustacea genus krithe from chain core 82 24 4pc from the western mid atlantic ridge 3427 m in order to estimate ocean circulation and bottom water temperature bwt variability over the past 200 000 years mg ca ratios have been used as a paleothermometer because the ratios are controlled primarily by ambient water temperatures at the time the organism secretes its adult carapace over the past two glacial interglacial cycles mg ca values oscillated between about 7 mmol mol and 12 mmol mol equivalent to a bwt range of 0 to 3 5 c the lowest values were obtained on specimens from glacial marine isotope stages miss 2 4 and 6 the highest values were obtained from specimens from the early part of the holocene interglacial mis 1 and also from miss 5 and 7 these trends suggest that bwts in the north atlantic ocean fluctuate over orbital time scales suborbital variability in mg ca ratios and bwt was also observed for the past 100 000 years ratios rose from 8 mmol mol to 10 mmol mol implying a bwt increase of 1 to 3 c during 14 mg ca excursions the highest ratios were found in krithe dated at approximately 32 36 38 43 48 73 85 and 93 ka although the age model for the chain 82 24 4pc and temporal resolution do not allow precise correlation some of these deep sea bottom temperature excursions appear to correspond to heinrich events recorded in other regions of the north atlantic and perhaps dansgaard oeschger interstadial events recorded in greenland ice cores if confirmed this would support the hypothesis that millennial scale oscillations of climate in the north atlantic are capable of affecting global climate via thermohaline circulation changes