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

reevaluation of the oxygen isotopic composition of planktonic foraminifera experimental results and revised paleotemperature equations cultured planktonic foraminifera orbulina universa symbiotic and globigerina bulloides nonsymbiotic are used to reexamine temperature 18o relationships at 15 25 c relationships for both species can be described by linear equations equations for o universa grown under low light ll and high light hl share a slope of 4 80 0 21 c 1 with a hl ll offset of 0 33 due to symbiont photosynthetic activity the effect of co32 on o universa is 0 002 mol 1 kg 1 and is insensitive to temperature for g bulloides ontogenetic effects produce size related trends in temperature 18o whereby larger shells are enriched in 18o relative to smaller specimens the o universa temperature 18o relationships are more accurate than previously published equations for describing plankton tow data our equations do not explain planktonic core top data with the same precision but provide a good fit to benthic cibicidoides data below 10 c temperature 18o relationships for g bulloides provide good agreement with field data for this species from the northeast pacific

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

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

continuous co 2 escape from the hypersaline dead sea caused by aragonite precipitation abstract chemical precipitation of caco 3 occurs in diverse marine and lacustrine environments in the hypersaline ca chloride lakes that have been occupying the dead sea basin since the late pleistocene caco 3 precipitated mostly as aragonite the aragonite sediments precipitated mainly during periods of high lake level stands as a result of mixing of bicarbonate rich freshwater runoff with dead sea brine that is ca rich and have high mg ca ratio during periods of arid conditions with limited freshwater inflow water level declined salinity increased and gypsum and halite became the dominant evaporitic minerals to precipitate the present study investigates the carbon cycle of the dead sea under the current limited water and bicarbonate supply to the brine representing periods of extremely arid conditions the decrease of inflows to the dead sea in recent years stems mainly from diversion of freshwater from the drainage basin and results in dramatic water level decline and massive halite precipitation during 2013 2014 bi monthly depth profiles of total alkalinity dissolved inorganic carbon dic and its isotopic composition 13 c were conducted in the dead sea from surface down to the bottom of the lake 290 m mass balance calculations conducted for the period 1993 2013 show that while inventories of conservative ions such as mg 2 remained constant the net dic inventory of the lake decreased by 10 dic supply to the lake during this period however amounted to 10 of lake s inventory indicating that during 20 years the lake lost 20 of its 1993s inventory compilation of historical data with our data shows that during the past two decades the lake s low dic 1 mmol kg 1 and very high pco 2 1800 ppm v remained relatively constant suggesting that a quasi steady state situation prevails in spite of the surprisingly stable dic and co 2 concentrations during this 20 year period 13 c dic increased significantly from 1 4 to 2 7 an isotopic mass balance calculation together with the high pco 2 of the brine show that during that period the lake lost about 3 7 10 10 moles of dic of which 60 by co 2 degassing and 40 by aragonite precipitation the deviation from the common 1 1 co 2 caco 3 ratio in most aqueous systems is facilitated by the dominance of the borate alkalinity of the dead sea nucleation and crystal growth experiments suggest that throughout this time the dead sea remained supersaturated with respect to aragonite a situation facilitated by combination of slow nucleation rates and absence of growth surfaces the very high pco 2 of the dead sea is maintained by the low co 2 piston velocity of the brine calculated to be only 4 5 m yr 1 more than an order of magnitude slower than seawater value

controlling factors of ca isotope fractionation in scleractinian corals evaluated by temperature ph and light controlled culture experiments abstract in this study the 44ca 40ca ratios of porites australiensis grown under three different culture experiments composed of temperature ph and light controlled culture experiments are measured the temperature dependent isotope fractionation of 0 02 c deduced from this study is similar to inorganic aragonite but the degree of isotope fractionation is about 0 4 offset in corals these observations agree with earlier results on different coral species suggesting ca isotope fractionation during ca transmembrane transport in corals while in cultured corals a significant temperature dependence of 44ca is observed the relationships between calcium isotope fractionation and ph as well as light intensity are negligible therefore variation of 44ca in porites corals is mainly controlled by temperature a combination of 44ca and sr ca of corals in temperature controlled experiments cannot be explained by rayleigh type fractionation directly from a fluid which is seawater like in terms of 44ca and sr ca through coral specific biomineralization processes overall mean 44ca of scleractinian corals including previous studies are different from biogenic aragonites secreted by sclerosponges and pteropods but are comparable with those of bivalves as well as calcitic coccolithophores and foraminifers these findings are important for better understanding biomineralization in corals and in order to constrain the ca isotopic composition of oceanic ca sinks in response to climate changes and associated with shifts of calcite and aragonite seas

origin of strontium and calcium in pedogenic needle fibre calcite nfc abstract strontium sr and calcium ca isotopic compositions and sr ca ratios have been analysed in different fractions of pedogenic needle fibre calcite nfc from the swiss jura mountains villiers neuch tel switzerland in order to determine their ca sources and to investigate the potential role of fungi in the origin of nfc 87sr 86sr ratios have been measured to trace the ca trapped within different pedogenic carbonate this ratio was compared for previously identified microscopic morphological groups of nfc the bulk soil fine earth

reorganization of deep ocean circulation accompanying a late cretaceous extinction event deep ocean circulation may be a significant factor in determining global climate1 5 increases in the flux of warm saline waters from low to high latitudes would enhance the poleward transport of heat and thus help maintain the warm conditions at high latitudes typical of globally warm greenhouse periods but controversy exists1 2 as to whether the ocean s thermohaline circulation can transport enough heat to bring about the temperature distributions of these times such as the mid cretaceous and early eocene here we present stable isotope records of ocean temperature and salinity that indicate that bottom waters in late cretaceous oceans of the southern hemisphere became cooler and less saline at the same time about 70 myr ago as widespread biotic changes3 6 8 these findings support the idea that changes in deep ocean circulation can act as a climate switch

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

effects of seawater carbonate ion concentration and temperature on shell u mg and sr in cultured planktonic foraminifera we investigate the sensitivity of u ca mg ca and sr ca to changes in seawater co3 and temperature in calcite produced by the two planktonic foraminifera species orbulina universa and globige rina bulloides in laboratory culture experiments our results demonstrate that at constant temperature u ca in o universa decreases by 25 7 per 100 mol co3 k g 1 as seawater co3 increases from 110 to 470 mol kg 1 results from g bulloides suggest a similar relationship but u ca is consistently offset by 40 at the same environmental co3 in o universa u ca is insensitive to temperature between 15 c and 25 c applying the o universa relationship to three u ca records from a related species globigerinoides sacculifer we estimate that caribbean and tropical atlantic co3 was 110 70 mol kg 1 and 80 40 mol kg 1 higher respectively during the last glacial period relative to the holocene this result is consistent with estimates of the glacial interglacial change in surface water co3 based on both modeling and on boron isotope ph estimates in settings where the addition of u by diagenetic processes is not a factor down core records of foraminiferal u ca have potential to provide information about changes in the ocean s carbonate concentration below ambient ph ph 8 2 mg ca decreased by 7 5 o universa t o 16 6 g bulloides per 0 1 unit increase in ph above ambient ph the change in mg ca was not significant for either species this result suggests that mg ca based paleotemperature estimates for the quaternary during which surface ocean ph has been at or above modern levels have not been biased by variations in surface water ph sr ca increased linearly by 1 6 0 4 per 0 1 unit increase in ph shell mg ca increased exponentially with temperature in o universa where mg ca 0 85 exp 0 096 t whereas the change in sr ca with temperature was within the reproducibility of replicate measurements copyright 2004 elsevier ltd

on the response of calcareous dinoflagellates to oligotrophy and stratification of the upper water column in the equatorial atlantic ocean abstract large numbers of calcareous dinoflagellate cysts and the vegetative calcareous coccoid species thoracosphaera heimii are generally found in sediments underlying oligotrophic and or stratified sub surface water environments it is difficult to distinguish between the relative importance of these two environmental parameters on calcareous cyst and t heimii distribution as they usually covary but this information is essential if we want to apply cysts properly in the reconstruction of palaeoenvironments and past surface water hydrography in the multi proxy core geob 1523 1 from the ceara rise region in the western equatorial atlantic ocean covering the past 155 ka periods of greatest oligotrophy are not synchronous with periods of greatest stratification ruhlemann et al mar geol 135 1996 127 152 mulitza et al geology 25 1997 335 338 mulitza et al earth planet sci lett 155 1998 237 249 giving us the unique opportunity to differentiate between the effects of both parameters on cyst accumulation the calcareous cyst record of the core reflects prominent increases in accumulation rate of nearly all observed species only during the nutrient enriched but more stratified isotopic sub stages 5 5 5 3 5 1 and 1 in this respect the distribution trends in the core are more similar to those of the eastern equatorial upwelling region geob 1105 4 than they are to those of the oligotrophic north eastern brazilian continental slope geob 2204 2 even though temporal changes in bioproductivity are principally in antiphase between the eastern and western equatorial regions we conclude that stratification of the upper water column and the presence of a well developed thermocline are probably the more important factors controlling cyst distribution in the equatorial atlantic whereas the state of oligotrophy secondarily influences cyst production within a well stratified environment

salt precipitation and dissolution in the late quaternary dead sea evidence from chemical and δ 37 cl composition of pore fluids and halites abstract the chemical composition and 37 cl of pore fluids from the icdp core drilled in the deepest floor of the terminal and hypersaline dead sea and halites from the adjacent mount sedom salt diapir are used to establish the dynamics of halite precipitation and dissolution during the last interglacial and glacial periods between 132 and 116 thousand years ago ka halites precipitated in the lake resulting in the expulsion of na and cl from the residual solution over 50 of the cl reservoir was removed resulting in a decrease in the na cl ratio from 0 57 to 0 19 this process was accompanied by a decrease in 37 cl values in the precipitating halites and the associated residual cl in the lake the observed decrease fits a rayleigh distillation curve with a fractionation factor of nacl dead sea solution 0 32 0 12 determined in the present study this behavior implies negligible contribution of external sources of cl to the lake during the main peak of the last interglacial mis5e subsequently during the last glacial ca 117 to 17 ka dissolution of halite took place the na and cl inventory were replenished accompanied by an increase in na cl from 0 21 to 0 55 and in the 37 cl values from 0 46 to 0 12 while the lake underwent significant dilution during that time the decrease in salinity was somewhat suppressed by the dissolution of the halite which was mostly derived from mount sedom salt diapir

suitability of stable oxygen and carbon isotopes of calcareous dinoflagellate cysts for paleoclimatic studies evidence from the campanian maastrichtian cooling phase abstract in order to determine the possible usefulness of stable isotope measurements on calcareous dinoflagellate cysts for paleoceanographic and paleoclimatic studies we have produced oxygen and carbon isotope records of the species pirumella krasheninnikovii bolli h m 1974 jurassic and cretaceous calcisphaerulidae from dsdp leg 27 eastern indian ocean initial reports of the deep sea drilling project 27 843 907 for the latest campanian to earliest maastrichtian 73 68 ma of high latitude ocean drilling program hole 690c in the southern south atlantic eastern weddell sea foraminiferal stable isotope values characterize this time interval as a phase of continuous cooling superimposed by a short term strong cooling event between 71 and 70 ma that was detected at various sites in the mid to high latitudes this event is interpreted to reflect short term surface water cooling leading to changes in the mode and direction of deep water formation and possibly the growth of continental ice sheets our 18o values of calcareous cysts verify this event as well as the general cooling of surface waters during the latest campanian and early maastrichtian prior to this cooling event between 72 and 71 ma a negative excursion in accompanying 13c records of planktic and benthic foraminifera was observed this negative excursion and the subsequent positive one were proposed to reflect sea level fluctuations changes in productivity and or changes in the ratio of organic to inorganic carbon input to the ocean the 13c values of calcareous cysts show the positive excursion between 71 and 70 ma but don t show the expected negative excursion before in addition they yield extremely light carbon isotope values that probably resulted from photosynthetic processes as the stable oxygen isotope data of the calcareous dinoflagellate species p krasheninnikovii show isotopic shifts comparable to planktic foraminifera from the same locality and from various other sites in the pacific and south atlantic oceans we suggest that calcareous cyst oxygen isotopes can provide information for paleoceanographic reconstructions of sea surface water temperatures and paleoceanographic changes however the application of carbon isotope data from cysts of p krasheninnikovii appears to be questionable and investigations of different species are needed to further evaluate the reconstruction potential based on stable isotopes and to assess species specific vital effects

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

interpreting the ca isotope record of marine biogenic carbonates an 18 million year record of the ca isotopic composition 44 42ca of planktonic foraminiferans from odp site 925 in the atlantic on the ceara rise provides the opportunity for critical analysis of ca isotope based reconstructions of the ca cycle 44 42ca in this record averages 0 37 0 05 1 sd and ranges from 0 21 to 0 52 the record is a good match to previously published neogene ca isotope records based on foraminiferans but is not similar to the record based on bulk carbonates which has values that are as much as 0 25 lower bulk carbonate and planktonic foraminiferans from core tops differ slightly in their 44 42ca i e by 0 06 0 06 n 5 while the difference between bulk carbonate and foraminiferan values further back in time is markedly larger leaving open the question of the cause of the difference modeling the global ca cycle from downcore variations in 44 42ca by assuming fixed values for the isotopic composition of weathering inputs 44 42caw and for isotope fractionation associated with the production of carbonate sediments sed results in unrealistically large variations in the total mass of ca2 in the oceans over the neogene alternatively variations of 0 05 in the ca isotope composition of weathering inputs or in the extent of fractionation of ca isotopes during calcareous sediment formation could entirely account for variations in the ca isotopic composition of marine carbonates ca isotope fractionation during continental weathering such as has been recently observed could easily result in variations in 44 42caw of a few tenths of permil likewise a difference in the fractionation factors associated with aragonite versus calcite formation could drive shifts in sed of tenths of permil with shifts in the relative output of calcite and aragonite from the ocean until better constraints on variations in 44 42caw and sed have been established modeling the ca2 content of seawater from ca isotope curves should be approached cautiously

marine production in the congo influenced se atlantic over the past 30 000 years a novel dinoflagellate cyst based transfer function approach abstract the sediments from the congo deep sea fan contain valuable information about past environmental conditions of the east equatorial atlantic during the transition from the last glacial maximum lgm to present day climatic conditions the high resolution marine organic walled dinoflagellate cysts dinocysts and terrestrial pollen palynological records from two cores off equatorial west africa covering the last 30 000 years document three major phases in surface productivity 1 during the lgm relative sea level was low nutrient enrichment due to seasonal coastal upwelling prevailed off the congo mouth and high aridity prevailed in the catchment area 2 at around 15 2 cal ka bp monsoonal precipitation strengthened over the congo basin generating high river discharges river induced upwelling and increased nutrient flux to the ocean in parallel erosion of shelf sediments during shelf transgression further enhanced nutrient flux 3 at around 9 8 cal ka bp rainforest vegetation inhibited soil erosion depleted nutrient supply and restricted marine productivity to its modern levels the study presents the application of modern analogues and a dinocyst transfer function to the reconstruction of primary palaeoproductivity pp in a region of freshwater influence a database of recent dinocyst assemblages comprising of 208 sites in the equatorial atlantic enabled the reconstruction of sea surface annual pp 1 3 times higher during the lgm and also during the deglaciation between 15 2 and 13 2 cal ka bp the reconstruction is independent of and thus provides corroboration for other biological and geochemical proxies

microfractures and their role in deformation of a quartz arenite from the central appalachian foreland abstract microfractures are pervasive in the massanutten sandstone a quartz arenite exposed in a doubly plunging synclinorium in the central appalachian foreland they are present as fluid inclusion planes fips and microveins parallel the fips fips occur in three orthogonal sets horizontal vertical and normal to the fold axis and vertical and parallel to the fold axis the geometry distribution and age of fips relative to other microstructures shows that microfractures developed during folding microfracturing followed layer parallel shortening by dislocation flow and was coeval with the peak of pressure solution that marked the final stages of folding microfracture densities are extremely high 160 mm 1 in many samples rapid closure of microfractures suppressed brecciation and prevented microfractures from propagating unstably to form joints microfracture opening accounts for significant finite strain with extensional strains of up to 11 1 and associated volume increases of over 16 0 the general lack of shortening microstructures indicates that a net volume increase is likely and that the massanutten sandstone may have served as a sink for dissolved phases from adjacent units undergoing volume loss deformation

temperature dependence of δ 7 li δ 44 ca and li ca during growth of calcium carbonate abstract lithium and calcium isotope ratios together with the li ca element ratio have been measured in calcites precipitated inorganically at temperatures ranging from 5 to 30 c and on seasonal growth bands from a coral these measurements indicate the potential uses of these three environmental proxies carbonate li isotopes are lighter than the solution from which they grow probably due to equilibrium fractionation this fractionation is not significantly influenced by temperature and because li is not involved in any known biological process this suggests that carbonates will provide a recorder for the past li isotope composition of natural waters and hence for past weathering conditions as has been observed previously for inorganic aragonite the ca isotopes in inorganic calcite are lighter than the growth solution and are only weakly dependent on temperature this confirms that the temperature dependence observed in some species of foraminifera geochem geophys geosyst 1 2001 reflects additional isotope fractionation due to biological processes during mineralization ca isotopes may therefore provide a powerful tool with which to investigate the processes of biomineralization finally li ca ratios in inorganic and biogenic carbonates increase as temperatures decrease with a sensitivity of 4 per c this temperature dependence of li ca may prove useful to assess past temperatures in cold environments such as the deep ocean

formation of southern component water in the late cretaceous evidence from nd isotopes constraining deep ocean circulation during past greenhouse climatic periods such as the cretaceous is important for understanding meridional heat transfer processes controls on ocean anoxia and the relative roles of climate and tectonics in determining paleocirculation patterns ocean circulation models for the late cretaceous and early paleogene suggest that significant deep water production occurred in the southern ocean but cannot constrain when this process commenced or what the temporal relationship was between opening tectonic gateways and late cretaceous climatic cooling nd isotope data obtained from biogenic apatite fish teeth and bones are presented from lower bathyal and abyssal sites in the south atlantic and indian oceans during the mid cretaceous relatively radiogenic nd isotope values suggest that deep water circulation in these basins was sluggish with inputs likely dominated by seawater particle exchange processes and possibly easily weathered volcanic terranes in the campanian maastrichtian the nd isotopic composition of proto indian and south atlantic deep waters became less radiogenic suggesting the onset of deep water formation in the southern ocean southern component water scw consistent with paleogene reconstructions and ocean circulation models a combination of southern hemisphere cooling and the opening of tectonic gateways during the campanian likely drove the onset of scw

a sem cathodoluminescence study of quartz in mildly deformed granite from the region of the atotsugawa fault central japan abstract cathodoluminescence cl images of quartz in granite distributed around the atotsugawa fault in central japan were observed by scanning electron microscopy and compared to optical microscope observations of the same crystals narrow or wide dark bands or dots were commonly recognized in the cl images almost all dots or narrow bands correlate with isolated bubbles or semi planar bubble arrays along healed cracks respectively some wide bands correspond to cracks filled with other minerals chlorite calcite mica etc or can be distinguished as zones with an extinction differing from that of surrounding areas in quartz crushed zones composed of healed crack arrays other wide bands are healed cracks where quartz is precipitated in optical continuity the quartz cl images displayed overall textures composed of mineral filled cracks bubble arrays along healed cracks and crushed zones more clearly than normal optical images healed cracks containing quartz precipitated in optical continuity with the enclosing grains were distinctly revealed as dark bands in cl images the abundance of these minor deformation structures as revealed in cl images increases with proximity to the fault therefore cl textures of quartz are an important aid in examining brittle deformation textures and understanding the tectonic processes that produce them

changes in the thermo haline structure of the dead sea 1979 1984 abstract from 1979 to 1984 the overall water balance of the dead sea was characterized by a water deficit however an excess of freshwater inflow during the 1979 80 rainy season resulted in a 3 year long meromictic phase this was followed by three consecutive overturns of the water column in december 1982 1983 and 1984 the buildup and dissipation of the seasonal thermocline and halocline is followed throughout this period which covers a wide range of water balance situations the gravitational stabilities of the summer pycnoclines measured in terms of n 2 3 10 2 s 2 are at least one order of magnitude greater than the values reported in freshwater lakes and oceans the contributions of temperature and salinity to n 2 and to the integrated stability w are examined separately and their interdependence is pointed out two irreversible effects in the evolution of the properties of the water masses are identified 1 a monotonic increase in the density of the deep waters and 2 a monotonic shift of the nacl saturation curve towards higher salinities

the solubility of halite as a function of temperature in the highly saline dead sea brine system the dead sea brine is characterized by high ionic strength 9 10 m and a ca cl composition the lake is currently saturated with respect to aragonite gypsum and halite harned s rule is applied to calculate the saturation index of halite in the dead sea brine system this system includes brines at ionic strengths in the range of 9 l 6 1 derived from evaporating dead sea brine to facilitate the calculation we determined new interaction coefficients experimentally these were found to be a function of the ionic strength of the solution as well as of the temperature 25 c anaa mgc12 0 002611 0 00905 anac1 caci 0 001501 0 00650 3 5 c anac l m cl 0 002831 0 01972 anacl caci 0 002071 0 01851 50 c anaci m l 0 002261 0 01416 anaci cacl 0 001561 0 01315 the new parameters are used to predict the effect of temperature on halite precipitation in the lake from both the evaporating surface layer and the entire upper water body the calculated weight of halite expected to precipitate before the onset of carnallite precipitation is on the order of lo o t at the present rate of evaporation at least 120 yr will pass before that point is reached

optical properties of the dead sea 1 the dead sea located in the rift valley between jordan and israel is a hypersaline lake resulting in unique biogeochemistry and optical properties in the spring of 2004 we conducted two days of physical and optical measurements in the lake because of the significant effect of dissolved salts on the optical properties of water our analysis required a novel processing approach to obtain dissolved and total inherent optical properties from the measurements in addition we show that the lake s salinity can be estimated from measurements of hyper spectral absorption or attenuation spectra in the red and infrared parts of the spectrum using published values of specific absorption of dissolved nacl despite the fact that the lake s salt chemistry is complex in situ observations demonstrated that the lake has a two layer structure with a warm and more turbid layer at the top 20 30 m and a clearer colder layer below both the particulate and dissolved absorption are well approximated by exponentially decreasing functions with the spectral slope of the particulate absorption about half that of the dissolved fraction and consistent with other aquatic environments both have relatively low and similar magnitudes in the blue o 0 15 m 1 mean particle size was observed to increase with depth consistent with precipitating salt crystals observed in past campaigns shown here to play a major role in the lake s optical properties

middle late cretaceous climate of the southern high latitudes stable isotopic evidence for minimal equator to pole thermal gradients a detailed 18 o and 13 c stratigraphy has been generated from analysis of well preserved albian early maastrichtian foraminifera from deep sea drilling project dsdp sites 511 and 327 falkland plateau 58 s 62 s paleolatitude in the southern south atlantic and cenomanian and coniacian santonian foraminifera from dsdp site 258 naturaliste plateau 58 s paleolatitude in the southern indian ocean these results when combined with previously published maastrichtian stable isotope data from ocean drilling program odp site 690 weddell sea 65 s paleolatitude provide new insight into the climatic and oceanographic history of the southern high latitudes during middle late cretaceous time the planktonic foraminifer 18 o curves reveal a gradual warming of surface waters from the albian through the cenomanian followed by extremely warm surface waters from the turonian through the early campanian long term cooling of surface waters began in the late early campanian and continued through the end of the maastrichtian the benthic foraminifer 18 o record generally parallels changes in the oxygen isotopic curves defined by shallow dwelling planktonic foraminifera the vertical oxygen and carbon isotopic gradients were relatively low during the albian cenomanian high from the turonian early campanian and then low during the late campanian and maastrichtian foraminiferal oxygen isotopic data from published sources and this study are averaged for each site corrected for latitudinal changes in salinity based on modern day surface water values and plotted versus paleolatitude for the late albian coniacian santonian and late maastrichtian differences between lowand high latitude surface water paleotemperatures are estimated at 14 c during the late albian and late maastrichtian but the coniacian santonian reconstruction reveals only a 0 4 c latitudinal temperature gradient uncertainty regarding cretaceous salinity gradients and possible diagenetic alteration of 18 o values introduce error into our estimates of paleolatitudinal thermal gradients however apparent low equator to pole temperature differences could indicate much higher poleward heat transport than at present

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

seasonal variations of halite saturation in the dead sea hypersaline lakes and seas were common in the past precipitating thick evaporitic salt deposits the only modern analogue for the paleo limnology of deep salt saturated aquatic environments exists in the dead sea in this study we present new insights from the dead sea on the role of seasonal thermohaline stratification and water balance on the seasonal and depth variations of the degree of saturation of halite salt and the rate of halite growth along the water column we developed methodologies to accurately determine the empirical degree of halite saturation of the lake based on high accuracy densitometry and to quantify halite growth rate along the water column during summer the epilimnion is undersaturated and halite is dissolved whereas during winter the entire water column is supersaturated and crystallizes halite this result is not trivial because the variations in the water balance suggest the opposite summer is associated with higher loss of water by evaporation from the lake compared to the winter hence the thermal effect overcomes the hydrological balance effect and thus governs the seasonal saturation cycle the hypolimnion is supersaturated with respect to halite and crystallizes throughout the year with higher super saturation and higher crystallization rates during winter during summer simultaneous opposing environments coexist an under saturated epilimnion that dissolves halite and a supersaturated hypolimnion that crystallizes halite which results in focusing of halite deposits in the deep hypolimnetic parts of the evaporitic basins and thinning the shallow epilimnetic deposits this article is protected by copyright all rights reserved

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

trace element proxies for surface ocean conditions a synthesis of culture calibrations with planktic foraminifera abstract the trace element composition of planktic foraminiferal calcite provides a useful means of determining past surface ocean conditions we have assembled the results of culture experiments for three species of symbiont bearing planktic foraminifera globigerinoides ruber globigerinoides sacculifer and orbulina universa and one symbiont barren species globigerina bulloides to evaluate their responses to temperature salinity ph carbonate ion and dissolved inorganic carbon dic growth conditions trace element ratios li ca b ca mg ca sr ca mn ca cd ca ba ca na ca and u ca were measured simultaneously on samples grown with the same culture techniques which provides robust relatable calibrations that may be used together in multi proxy paleoceanographic studies our data confirm that temperature is the dominant control on foraminiferal mg ca under the ranges of conditions studied and that the potential effects of salinity and co32 on mg ca of these tropical species across late pleistocene glacial cycles are relatively small carbonate system experiments suggest that sr ca may be useful for reconstructing large dic changes na ca increases with salinity in g ruber pink but not in g sacculifer as these emerging proxy relationships become more firmly established the synthesis of multiple trace element ratios may help paleoceanographers isolate the effects of different environmental parameters in paleo records calcification rates g day vary among species and do not respond consistently to any experimental parameter comparison of our calcification rates with those observed in inorganic calcite precipitation experiments suggest that foraminifera calcify 100 more slowly than inorganic calcites grown in similar solutions we suggest that calcification rate does not typically exert a dominant control on trace element partitioning in planktic foraminiferal calcite though it may play a role for some elements under certain circumstances differences in average growth rate cannot explain composition differences among species pointing to alternative controls that may be biological in origin

maastrichtian climate productivity and faunal turnovers in planktic foraminifera in south atlantic dsdp sites 525a and 21 abstract stratigraphic faunal and isotopic analyses of the maastrichtian at dsdp sites 525a and 21 in the south atlantic reveal a planktic foraminiferal fauna characterized by two major events an early late maastrichtian diversification and end maastrichtian mass extinction both events are accompanied by major changes in climate and productivity the diversification event which occurred in two steps between 70 5 and 69 1 ma increased species richness by a total of 43 and coincided with the onset of major cooling in surface and bottom waters and increased surface productivity the onset of the terminal decline in maastrichtian species richness began at 67 5 ma and the first significant decline in surface productivity occurred at 66 2 ma coincident maximum cooling to 13 c in surface waters and the reduction of the surface to deep temperature gradient to less than 5 c major climatic and moderate productivity changes mark the mass extinction and the last 500 kyr of the maastrichtian between 200 and 400 kyr before the k t boundary surface and deep waters warmed rapidly by 3 4 c and cooled again during the last 100 kyr of the maastrichtian surface productivity decreased only moderately across the k t boundary species richness began to decline during the late maastrichtian cooling and by k t boundary time the mass extinction had claimed 66 of the species viewed within the context of maastrichtian climate and productivity changes the k t mass extinction could have resulted from extreme environmental stress even without the addition of an extraterrestrial impact

calcium isotopes in deep time potential and limitations abstract calcium is an essential element in the biogeochemical cycles that regulate the long term climate state of earth the removal of co2 from the ocean atmosphere system is controlled by the burial of carbonate sediments caco3 ultimately linking the global calcium and carbon cycles this fundamental link has driven the development of the stable calcium isotope proxy with application to both ancient skeletal and non skeletal bulk carbonate sediments calcium isotope ratios 44 40ca have been used to track long term changes in seawater chemistry e g aragonite vs calcite seas and to elucidate short term climatic perturbations associated with mass extinction events however developments in the calcium isotope proxy have shown that 44 40ca values in carbonate minerals also are sensitive to changes in precipitation rates mineralogy and diagenesis thereby complicating the application of the proxy to the reconstruction of global cycles first inorganic carbonate precipitation experiments have demonstrated that carbonate 44 40ca values are sensitive to precipitation rates with higher rates generally leading to larger fractionation second 44 40ca values are sensitive to carbonate mineralogy with inorganic aragonite and calcite being on average 1 5 and 0 9 depleted relative to contemporaneous seawater respectively the effects of both changes in carbonate mineralogy and precipitation rates affect primary and secondary minerals but are particularly pronounced during carbonate diagenesis where relatively slow rates of recrystallization and neomorphism can lead to significant changes in bulk sediment 44 40ca values third changes in faunal composition expressed in skeletal fossil archives can lead to large changes in carbonate 44 40ca values that are decoupled from changes in global cycles nevertheless when these factors are appropriately considered the application of calcium isotopes in ancient carbonate sediments becomes a powerful tool for understanding biogeochemical processes that operate over many scales from diagenetic changes within the sediment pore space to regional changes across ancient carbonate platforms and to global changes in seawater chemistry through time importantly the processes that contribute to variability in carbonate 44 40ca values are likely to impact other carbonate bound proxies highlighting the potential for calcium isotopes as a tool to better understand the variability of other isotope systems

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

kinetics of gypsum nucleation and crystal growth from dead sea brine abstract the dead sea brine is supersaturated with respect to gypsum 1 42 laboratory experiments and evaluation of historical data show that gypsum nucleation and crystal growth kinetics from dead sea brine are both slower in comparison with solutions at a similar degree of supersaturation the slow kinetics of gypsum precipitation in the dead sea brine is mainly attributed to the low solubility of gypsum which is due to the high ca 2 so 4 2 molar ratio 115 high salinity 280 g kg and to na inhibition experiments with various clay minerals montmorillonite kaolinite indicate that these minerals do not serve as crystallization seeds in contrast calcite and aragonite which contain traces of gypsum impurities do prompt precipitation of gypsum but at a considerable slower rate than with pure gypsum this implies that transportation inflow of clay minerals calcite and local crystallization of minerals in the dead sea does not prompt significant heterogeneous precipitation of gypsum based on historical analyses of the dead sea it is shown that over the last decades as inflows to the lake decreased and its salinity increased gypsum continuously precipitated from the brine the increasing salinity and ca 2 so 4 2 ratio which results from the precipitation of gypsum lead to even slower kinetics of nucleation and crystal growth which resulted in an increasing degree of supersaturation with respect to gypsum therefore we predict that as the salinity of the dead sea brine continues to increase accompanied by dead sea water level decline although gypsum will continuously precipitate the degree of supersaturation will increase furthermore due to progressively slower kinetics

44ca 42ca and 143nd 144nd isotope variations in cretaceous eocene tethyan francolites and their bearing on phosphogenesis in the southern tethys measurements of 4 4 ca 4 2 ca and 1 4 3 nd 1 4 4 nd isotope ratios in carbonate fluorapatite cfa through the aptian eocene section of the negev israel together with quantified rates of p and ca accumulation and bulk sedimentation permit an examination of the relationships of these five factors to tethyan phosphogenesis the data provide an aptian eocene ca 70 ma record of the ca isotope composition of 35 cfa samples 24 of which were also analyzed for nd isotopes representing 11 time stratigraphic phosphate horizons within the sequence the 4 4 ca values are significantly lower in the aptian albian samples 4 4 ca 0 11 to 0 06 than in the campanian eocene samples 4 4 ca 0 22 to 0 42 whereas the e n d values increase from continental crust like in the aptian albian e n d t 10 9 to more radiogenic pacific like e n d t 6 6 to 6 1 in the campanian both peaks of 4 4 ca and e n d t in the campanian coincide with the peak of tethyan phosphogenesis in the negev which is marked by a sharp increase of p accumulation rates from 200 mol cm 2 k y 1 in pre campanian time to 1700 mol cm 2 k y 1 in the campanian and a decrease in rates of ca accumulation and bulk sedimentation the coincident increases of 4 4 ca and e n d t values and p accumulation rates in the negev area during the campanian suggest that they are related in this time interval and were induced by the global late cretaceous sea level rise and increasing circumequatorial tethyan flow

chronology with a pinch of salt integrated stratigraphy of messinian evaporites in the deep eastern mediterranean reveals long lasting halite deposition during atlantic connectivity abstract the messinian salinity crisis msc 5 97 5 33 ma is considered an extreme environmental event driven by changes in climate and tectonics which affected global ocean salinity and shaped the biogeochemical composition of the mediterranean sea yet after more than 50 years of research msc stratigraphy remains controversial recent studies agree that the transition from the underlying pre evaporite sediments to thick halite deposits is conformal in the deep eastern mediterranean basin however the age of the base and the duration of halite deposition are still unclear also disputed is the nature of the intermediate and upper msc units which are characterized as periods of increased clastic deposition into the eastern mediterranean based on marginal outcrops and seismic data we provide a multidisciplinary study of sedimentary geochemical and geophysical data from industrial offshore wells in the levant basin which recovered a sedimentary record of deep basin mediterranean evaporites deposited during the msc in combination with previous observations of the msc throughout the mediterranean basin our results promote the need for a new chronological model remarkably the one kilometer thick lower part of the evaporitic unit is composed of essentially pure halite except for a thin transitional anhydrite layer at its base the halite is undisturbed and homogeneous lacking diverse features apparent in more proximal sections indicating a deep sea depositional environment we find that distinct meters thick non evaporitic intervals interbedded with the halite previously thought to be clastic layers are diatomites while xrd analysis confirms an increase in clastic components in these sediments they are composed primarily of well preserved marine and freshwater planktonic diatoms the occurrence of marine planktonic diatoms in these intervals indicates the input of atlantic waters into the mediterranean basin during the deposition of the massive halite unit seismic stratigraphy and well log cyclostratigraphy further support deep basin halite deposition which started about 300 kyr earlier than widely assumed 5 97 ma we propose that halite deposition in the deep mediterranean took place during stage 1 of the msc rather than being limited to the short 50 kyr msc acme when sea level was presumably at its lowest thus brine formation salt precipitation and faunal extinction occurred at least in part in a deep non desiccated basin with a restricted yet open mediterranean atlantic connection that allowed inflow of oceanic water we observe an increase in heavy minerals and reworked fauna within the clastic evaporitic interbedded evaporites of the basinal msc section and argue that these settings correspond in the deep basins with a significant sea level drawdown during stage 2 of the msc as observed in the marginal sections this correlation is corroborated by astrochronology and chemostratigraphic markers such as the distribution of n alkanes and biomarker based thermal maturity indices the levant deposits indicate that high sea level and partial connectivity with global oceans promoted the deposition of deep basin deep water halite while sea level drawdown promoted deposition of reworked and transported material from the margins into deep mediterranean basins this study modifies the current understanding of the mechanisms governing salt deposition throughout the msc with implications for other evaporitic events in the geologic record

ca isotopes in carbonate sediment and pore fluid from odp site 807a the ca2 aq calcite equilibrium fractionation factor and calcite recrystallization rates in pleistocene sediments abstract the calcium isotopic compositions 44ca of 30 high purity nannofossil ooze and chalk and 7 pore fluid samples from odp site 807a ontong java plateau are used in conjunction with numerical models to determine the equilibrium calcium isotope fractionation factor s f between calcite and dissolved ca2 and the rates of post depositional recrystallization in deep sea carbonate ooze the value of s f at equilibrium in the marine sedimentary section is 1 0000 0 0001 which is significantly different from the value 0 9987 0 0002 found in laboratory experiments of calcite precipitation and in the formation of biogenic calcite in the surface ocean we hypothesize that this fractionation factor is relevant to calcite precipitation in any system at equilibrium and that this equilibrium fractionation factor has implications for the mechanisms responsible for ca isotope fractionation during calcite precipitation we describe a steady state model that offers a unified framework for explaining ca isotope fractionation across the observed precipitation rate range of 14 orders of magnitude the model attributes ca isotope fractionation to the relative balance between the attachment and detachment fluxes at the calcite crystal surface this model represents our hypothesis for the mechanism responsible for isotope fractionation during calcite precipitation the ca isotope data provide evidence that the bulk rate of calcite recrystallization in freshly deposited carbonate ooze is 30 40 myr and decreases with age to about 2 myr in 2 3 million year old sediment the recrystallization rates determined from ca isotopes for pleistocene sediments are higher than those previously inferred from pore fluid sr concentration and are consistent with rates derived for late pleistocene siliciclastic sediments using uranium isotopes combining our results for the equilibrium fractionation factor and recrystallization rates we evaluate the effect of diagenesis on the ca isotopic composition of marine carbonates at site 807a since calcite precipitation rates in the sedimentary column are many orders of magnitude slower than laboratory experiments and the pore fluids are only slightly oversaturated with respect to calcite the isotopic composition of diagenetic calcite is likely to reflect equilibrium precipitation accordingly diagenesis produces a maximum shift in 44ca of 0 15 for site 807a sediments but will have a larger impact where sedimentation rates are low seawater circulates through the sediment pile or there are prolonged depositional hiatuses

variations in the marine ca cycle over the past 20 million years a 20 million year marine ca isotope record is constructed based on measurements of 36 nannofossil ooze samples from dsdp site 590 the ca isotopic composition d 44 ca relative to our bbulk earthq average of carbonate ooze samples varies between 0 2 and 0 9 and the inferred d 44 ca of seawater calcium varies between 1 1 and 0 4 modern seawater value is 0 95 on our scale fluctuations in the seawater ca isotope ratio occur in 2 to 4 million year intervals and indicate that the supply and removal of ca from the oceans are seldom in balance the ca isotope record is used to reconstruct past weathering fluxes and marine calcium concentrations the inferred marine concentration of ca fluctuates by about f20 on 2 4 million year time scales and by about f50 over the 20 million year record these variations are presumably superimposed on the previously inferred 100 million year variations the seawater ca concentration was about 0 5 times present at 20 ma and generally increased until 6 ma 1 7 times present local maxima in seawater calcium concentrations occur at 6 4 and 4 ma preceding periods of enhanced marine productivity and high mass accumulation rates at site 590 while the calculated calcium concentrations are sensitive to the assumed d 44 ca value for the weathering flux the 2 4 million year features of the derived

potential use of stable oxygen isotope composition of thoracosphaera heimii dinophyceae for upper watercolumn thermocline temperature reconstruction abstract to investigate the potential use of the stable isotope composition of the vegetative cysts of the photosynthetic dinoflagellate thoracosphaera heimii for quantitative palaeotemperature reconstructions a method has been developed to purify t heimii cysts from sediment samples stable oxygen and carbon isotopes have been measured on t heimii cysts from 21 surface sediment samples from the equatorial atlantic and south atlantic oceans calculated temperatures based on the palaeotemperature equation for inorganic calcite precipitation generally reflect mean annual temperatures of the upper water column notably of thermocline depths although the present results suggest that the isotopic composition of t heimii shells might be formed in equilibrium with the seawater in which the shells are being formed future investigations are required to determine possible effects of metabolic and kinetic processes on the fractionation process this pilot study therefore forms the basis for future investigations on the development of this tool and the determination of a species specific palaeotemperature equation the wide geographic and stratigraphic distribution of t heimii cysts in sediments the stable position of t heimii within the water column and the high resistance of its cysts against calcite dissolution underline its potential for a wide usability in palaeotemperature reconstructions

dinoflagellate cysts as indicators of water quality and productivity in british columbia estuarine environments abstract palynological analyses of 60 surface sediment samples from estuarine environments near vancouver island including the georgia strait gs the effingham eff and the seymour belize sb inlets were performed in order to document the distribution of dinoflagellate cyst assemblages and their relationship to hydrographic conditions productivity and nutrient concentrations we tested transfer functions using the analogue method and suggest that dinoflagellate cyst assemblages can be used to reconstruct primary productivity temperature and salinity the eff and sb inlets are characterized by a dominance of autotrophic taxa particularly operculodinium centrocarpum whereas the protoperidinioid and gymnodinial heterotrophic taxa such as quinquecuspis concreta and brigantedinium spp dominate the assemblages of the gs multivariate analysis shows that this distribution is closely linked to primary productivity sea surface temperature sst and spring silica concentration the abundance of autotrophic taxa in the eff and sb inlets is associated with high primary productivity and low summer sst indicating summer upwelling of coastal british columbia whereas the heterotrophic taxa that characterizes the gs assemblages are related to low productivity high summer sst and high silica concentration during spring multivariate analysis shows that the most important environmental parameters related to dinocyst distribution in the restricted embayment of the gs are distance to the shore distance to vancouver harbor spring sea surface salinity sss spring phosphate concentration and spring productivity the autotrophic taxa are generally more common in coastal and shallow waters but spiniferites ramosus and pentapharsodinium dalei show an opposite correlation to spring productivity and salinity p dalei is particularly abundant around vancouver harbor near highly urbanized shores and within the fraser river plume where salinity is low and spring productivity and continental runoff are high s ramosus shows its highest abundance on the western coast of gs protoperidinioid and gymnodinial cysts characterize distal zones within the central and southern gs that are associated with a mixture of brackish waters coming from the fraser river and deep upwelling waters entering the gs via juan de fuca strait the relationship between dinoflagellate cyst assemblages and primary productivity in these estuarine systems differs from that in oceanic and outer neritic zones where the abundance of heterotrophic taxa is commonly associated with upwelling and high productivity

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

evolution of middle to late cretaceous oceans a 55 m y record of earth s temperature and carbon cycle a new 55 m y global compilation of benthic foraminifera 13 c and 18 o for the middle to late cretaceous shows that there was widespread formation of bottom waters with temperatures 20 c during the cretaceous greenhouse world these bottom waters filled the silled north atlantic and probably originated as thermocline or intermediate waters in the tropical oceans carbon burial during the cretaceous oceanic anoxic events produced a positive 13 c shift in global carbon reservoirs but this is not particularly large especially by comparison with the remarkable late paleocene carbon maximum the interbasin 13 c gradient was unusually large during the cretaceous hot greenhouse probably because the north atlantic sills prevented the free exchange of waters in the deep basin the hot greenhouse ended when the equatorial atlantic gateway opened sufficiently to flood the deep north atlantic with relatively cool polar waters formed in the southern ocean

deep sea paleotemperature record of extreme warmth during the cretaceous oxygen isotope analyses of well preserved foraminifera from blake nose 30 n paleolatitude north atlantic and globally distributed deep sea sites provide a long term paleotemperature record for the late albian maastrichtian interval that is difficult to reconcile with the existence of significant cretaceous ice sheets given reasonable assumptions about the isotopic composition of cretaceous seawater our results suggest that middle bathyal water temperatures at blake nose increased from 12 c in the late albian through middle cenomanian to a maximum of 20 c during the latest cenomanian and earliest turonian bottom waters were again 12 c during the middle campanian and cooled to a minimum of 9 c during the maastrichtian correlative middle bathyal foraminifera from other ocean basins yield paleotemperature estimates that are very similar to those from blake nose comparison of global bottom water temperatures and latitudinal thermal gradients suggests that global climate changed from a warm greenhouse state during the late albian through late cenomanian to a hot greenhouse phase during the latest cenomanian through early campanian then to cool greenhouse conditions during the mid campanian through maastrichtian

correlation between deformation lamellae microfractures macrofractures and in situ stress measurements white river uplift colorado dynamic analyses of quartz deformation lamellae and microfractures in lower paleozoic quartzites from the white river uplift record a northwest direction of compression which can be related to joint and fault orientations and in situ stress determinations crystallographic orientations of deformation lamellae resemble those formed in the subbasal i relatively nonselective domain microfractures in quartz grains form orthogonal sets of generally north northeast and west northwest trending fracutres which are approximately normal to bedding the strongest set of microfractures in most samples lies in the 2 plane deduced from deformation lamellae analyses suggesting that the microfractures are extensional features maxima of microfractures correspond to maxima of joints measured at adjacent locations the strikes of prominent west northwest sets of microfractures and joints are subparellel to the dominant northwest strike of faults on the uplift in situ stress measurements conducted in the piceance basin and rangely colorado areas indicate principal stress orientations similar to those determined from quartz deformation lamellae microfractures and joints which are pre uplift to early uplift late laramide fabric elements

temperature seasonality control on modern halite layers in the dead sea in situ observations layered halite sequences are found in deep basins throughout the geological record however analogs for such sequences are commonly studied in shallow environments here we studied active precipitation of halite layers from the only modern analog for deep halite precipitating basins the hypersaline dead sea in situ observations in the dead sea link seasonal thermohaline stratification halite saturation and the characteristics of the actively forming halite layers the spatiotemporal evolution of halite precipitation in the dead sea was characterized by means of monthly observations of 1 lake thermohaline stratification temperature salinity and density 2 degree of halite saturation and 3 textural evolution of the active halite deposits we present the observed relationships between the textural characteristics of layered halite deposits i e grain size consolidation and roughness and the degree of saturation which in turn reflects the limnology and hydroclimatology the lake floor is divided into two principal environments a deep hypolimnetic lake floor and a shallow epilimnetic lake floor in the deeper hypolimnetic lake floor halite continuously precipitates with seasonal variations 1 during summer consolidated coarse halite crystals form rough surfaces under slight supersaturation 2 during winter unconsolidated fine halite crystals form smooth lake floor deposits under high supersaturation these observations support interpretations of the seasonal alternation of halite crystallization mechanisms the shallow epilimnetic lake floor is highly influenced by the seasonal temperature variations and by intensive summer dissolution of part of the previous year s halite deposit which results in thin sequences with annual unconformities this emphasizes the control of temperature seasonality on the characteristics of the precipitated halite layers in addition precipitation of halite on the hypolimnetic floor at the expense of the dissolution of the epilimnetic floor results in lateral focusing and thickening of halite deposits in the deeper part of the basin and thinning of the deposits in shallow marginal basins

isotope fractionation during ca exchange on clay minerals in a marine environment abstract in order to interpret marine porewater profiles it is mandatory to understand the behavior of calcium ca and its isotopes during cation exchange in marine sediments it has been proposed that the exchange of adsorbed ca 2 for ammonium which is a product of organic matter decomposition results in the releases of light ca from clay minerals into the porewater teichert et al 2009 in order to investigate the effect of ammonium on ca isotope fractionation experiments with clay mineral separates illites montmorillonite kaolinite and natural marine sediments from the north atlantic integrated ocean drilling project site u1306a in artificial seawater were carried out at different temperatures 4 14 21 c and ammonium concentrations 100 140 180 mm the results of the adsorption experiments carried out in artificial seawater show that during adsorption of ca 2 the light ca isotopes are favored over the heavier ca isotopes this effect is most prominent for the illite samples 1000ln 0 82 to 1 15 and kaolinite sample 1000ln 1 23 to 2 76 whereas montmorillonite and the natural marine sediments show smaller degrees of fractionation from the fluid in the range of 0 46 to 0 06 determination of the desorbed ca 2 is based on the adsorbed ca 2 left on the exchanger and reveals that the desorbed ca 2 has a significantly different isotopic signature from the surrounding fluid in general the degree of ca isotope fractionation is dependent on the ammonium concentration and does not show significant influence of temperature modeling the ca 2 desorption induced by ammonium adsorption demonstrates that according to the prevailing mineralogy and porewater sediment ratio desorbed ca 2 has the potential to shift the porewater isotopy by up to 2 5 and needs to be considered when interpreting ca isotope porewater profiles

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

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

evolution of early cenozoic marine temperatures the equator to high southern latitude sea surface and vertical temperature gradients are reconstructed from oxygen isotope values of planktonic and benthic foraminifers for the following five time intervals late paleocene early eocene early middle eocene late eocene and early oligocene paleotemperatures are calculated using standard oxygen isotope temperature equations with adjustments to account for 1 variations in sea water 18o related to changes in global ice volume over time and 2 latitudinal gradients in surface water 18o these reconstructions indicate that sea surface temperatures sst of the southern oceans in the early eocene were as high as 15 c whereas temperatures during the late paleocene and early middle eocene reached maximum levels of 10 12 c by the late eocene and early oligocene high latitude sst had declined to 6 and 4 c respectively for most of the early paleogene low latitude sub tropical temperatures remained constant and well within the range of holocene temperatures 24 ndash 25 c but by the late eocene and early oligocene declined to values in the range of 18 to 22 c the late paleogene apparent decline in tropical temperatures however might be artificial because of dissolution of near surface foraminifera tests which biased sediment assemblages toward deeper dwelling foraminifera moreover according to recent plate reconstructions it appears that the majority of sites upon which the late eocene and early oligocene tropical temperatures were previously established were located either in or near regions likely to have been influenced by upwelling global deepwater temperature on average paralleled southern ocean sst for most of the paleogene we speculate based on the overall timing and character of marine sea surface temperature variation during the paleogene that some combination of both higher levels of greenhouse gases and increased heat transport was responsible for the exceptional high latitude warmth of the early eocene

calcium isotope fractionation in selected modern and ancient marine carbonates the calcium isotope composition 44 42ca was analyzed in modern cretaceous and carboniferous marine skeletal carbonates as well as in bioclasts non skeletal components and diagenetic cements of cretaceous and carboniferous limestones in order to gain insight in ca2 aq caco3 isotope fractionation mechanisms in marine carbonates splits of samples were analyzed for sr mg fe and mn concentrations and for their oxygen and carbon isotopic composition biological carbonates generally have lower 44 42ca values than inorganic marine cements and there appears to be no fractionation between seawater and marine inorganic calcite a kinetic isotope effect related to precipitation rate is considered to control the overall discrimination against 44ca in biological carbonates when compared to inorganic precipitates this is supported by a well defined correlation of the 44 42ca values with sr concentrations in cretaceous limestones that contain biological carbonates at various stages of marine diagenetic alteration no significant temperature dependence of ca isotope fractionation was found in shells of cretaceous rudist bivalves that have recorded large seasonal temperature variations as derived from 18o values and mg concentrations the reconstruction of secular variations in the 44 42ca value of seawater from well preserved skeletal calcite is compromised by a broad range of variation found in both modern and cretaceous biological carbonates independent of chemical composition or mineralogy despite these variations that may be due to still unidentified biological fractionation mechanisms the 44 42ca values of cretaceous skeletal calcite suggest that the 44 42ca value of cretaceous seawater was 0 3 0 4 lower than that of the modern ocean

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

campanian maastrichtian ocean circulation in the tropical pacific the pacific ocean is the largest water body on earth and circulation in the pacific contributed significantly to climate evolution in the latest cretaceous the culmination of a period of long term cooling here we present new high resolution late campanian to maastrichtian benthic and planktic foraminiferal stable isotope data and a neodymium nd isotope record obtained from sedimentary ferromanganese oxide coatings of ocean drilling program hole 1210b from the tropical pacific ocean shatsky rise these new records resolve 13 million years in the latest cretaceous providing insights into changes in surface and bottom water temperatures and source regions of deep to intermediate waters covering the carbon isotope excursions of the campanian maastrichtian boundary event cmbe and the mid maastrichtian event mme our new benthic foraminiferal 18o and nd isotope records together with published nd isotope data show markedly parallel trends across the studied interval over a broad range of bathyal to abyssal water depths interpreted to reflect changes in the intensity of deep ocean circulation in the tropical pacific in particular we observe a three million year long period of cooler conditions in the early maastrichtian 72 5 to 69 5 ma when a concomitant change toward less radiogenic seawater nd isotope signatures probably marks a period of enhanced admixture and northward flow of deep waters with southern ocean provenance we suggest this change to have been triggered by intensified formation and convection of deep waters in the high southern latitudes a process that weakened during the mme 69 5 to 68 5 ma the early maastrichtian cold interval is closely related to the negative and positive carbon isotope trends of the cmbe and mme the millions of years long duration of these carbon cycle perturbations suggests a tectonic forcing of climatic cooling possibly related to changes in ocean basin geometry and bathymetry

scleractinian corals produce calcite and grow more slowly in artificial cretaceous seawater the mineralogies of most biotic and abiotic carbonates have alternated in synchroneity between the calcite hexagonal and aragonite orthorhombic polymorphs of caco3 throughout the phanerozoic eon these intervals of calcite and aragonite production or calcite seas and aragonite seas are thought to be caused primarily by secular variation in the molar magnesium calcium ratio of seawater mmg ca 2 5 aragonite 1 high mg calcite mmg ca 2 5 low mg calcite a ratio that has oscillated between 1 0 and 5 2 throughout the phanerozoic in laboratory experiments we show that three species of scleractinian corals which produce aragonite in modern seawater and which have flourished as important reef builders primarily during aragonite seas of the past began producing calcite in artificial seawater with an ambient mmg ca ratio below that of modern seawater 5 2 the corals produced progressively higher percentages of calcite and calcified at lower rates with further reduction of the ambient mmg ca ratio in artificial seawater of imputed late cretaceous composition mmg ca 5 1 0 which favors the precipitation of the calcite polymorph scleractinian corals produced skeletons containing 30 low mg calcite skeletal mmg ca 0 04 these results indicate that the skeletal mineral used by scleractinian corals is partially determined by seawater chemistry furthermore slow calcification rates resulting from the production of largely aragonitic skeletons in chemically unfavorable seawater mmg ca 2 probably contributed to the scleractinians diminished reef building role in the calcite seas of late cretaceous and early cenozoic time

early maastrichtian carbon cycle perturbation and cooling event implications from the south atlantic ocean published stable isotope records in marine carbonate are characterized by a positive 18o excursion associated with a negative 13c shift during the early maastrichtian however the cause and even the precise timing of these excursions remain uncertain we have generated high resolution foraminiferal stable isotope and grey scale records for the latest campanian to early maastrichtian 73 68 ma at two ocean drilling program sites 525 walvis ridge and 690 weddell sea we demonstrate that the negative 13c excursion is decoupled from the 18o increase with a lag of about 600 kyr our 13c records both planktic and benthic show an amplitude for the negative excursion of 0 7 that falls between about 72 1 and 70 7 ma our planktic 18o records indicate an overall increase of 1 2 from 73 to 68 ma at site 690 whereas at site 525 they record a slightly smaller increase 1 that peaks around 70 1 ma with decreasing values thereafter our benthic 18o data indicate an increase of 1 5 at site 525 and 0 7 at site 690 between about 71 4 and 69 9 ma benthic 18o values show different baseline values at the two sites before and after the excursion but the larger increase at site 525 means that the values attained at the peak of the excursion are similar at the two sites we interpret this observation in terms of water mass changes the excursion is interpreted to reflect a cooling of bottom waters in response to the strengthening contribution of intermediate to deep water production in the high southern latitudes rather than increased ice volume the associated carbon cycle perturbations that we observe are interpreted to reflect a weakening of surface water stratification and increased productivity as supported by our grey value data

evolution of tethyan phosphogenesis along the northern edges of the arabian african shield during the cretaceous eocene as deduced from temporal variations of ca and nd isotopes and rates of p accumulation abstract the evolution of tethyan phosphogenesis during the cretaceous eocene is examined to try to explain fluctuations of phosphogenesis through time and whether or not they reflect long term changes in ocean circulation or in continental weathering twenty seven time stratigraphic phosphate levels in various tethyan sites covering a time span of about 90 myr from the hauterivian to the eocene were analyzed for 44 ca 42 ca and 143 nd 144 nd in their carbonate fluorapatite cfa fraction p and ca accumulation rates and bulk sedimentation rates were quantified throughout the cretaceous eocene negev sequence to examine how changes in 44 ca 42 ca and 143 nd 144 nd are reflected in the intensity of phosphogenesis a clear cut change occurs in e nd t and 44 ca and in the rates of p and ca accumulation and bulk sedimentation through the time analyzed e nd t is much lower in the hauterivian lower cenomanian 12 8 to 10 9 than in the upper cenomanian eocene 7 8 to 5 9 much lower 44 ca values occur in the hauterivian turonian 0 22 to 0 02 than in the coniacian eocene 0 23 to 0 40 p accumulation rates in the negev steeply increase from 2 k yr 1 in the albian coniacian to 1500 mol cm 2 k yr 1 in the campanian whereas a strong decrease is concomitantly recorded in the rates of ca accumulation and bulk sedimentation in addition distinct e nd t values are shown by the phosphorites of the negev 6 7 to 6 4 and egypt 9 1 to 7 6 during the campanian and by those of the negev 7 8 to 6 3 and north africa 10 1 to 8 9 during the maastrichtian eocene the culmination of p accumulation rates in the negev during the campanian occurring with a high in e nd t and 44 ca and a low in sedimentation rates indicates that paleoceanographic and paleogeographical factors mostly governed phosphorite accumulation in this area the abrupt e nd t rise after the cenomanian is attributed to increased incursion of pacific radiogenic water masses into the tethys driven by the late cretaceous global sea level rise the connection between north and south atlantic the global post santonian cooling and the progressive widening of the caribbean threshold all acting in combination to significantly intensify the tethyan circumglobal current tcc it also reflects a weakening of the continental nd signal due to a reduction of exposed landmasses caused by increased flooding of continental shelves high 44 ca values at those times also point to a decrease in weathering ca 2 fluxes and expansion of carbonate sedimentation in shelves both enriching seawater with isotopically heavy ca 2 deep ocean circulation intensified by the post santonian cooling of high latitudes increased p inventory in the tethys basin whereas the strengthened tcc and the folded shelf likely resulted in coastal and topographically induced upwelling supplying p rich intermediate waters to southeastern tethys shelves only in the paleocene eocene following major changes in global circulation produced by narrowing of tethys and widening of the atlantic did phosphogenesis shifts its locus of high intensity to the western atlantic tethys and west african atlantic coasts this change in paleocirculation is expressed by distinctly differing e nd t in the middle east and the north and west african phosphorites suggesting different oceanic p sources and current systems for these two major groups of phosphorites our nd isotope results further suggest a weaker tcc during the mid cretaceous becoming more intense in late cretaceous times they also point to the north pacific ocean as major source of deep water formation for the intermediate deep waters in the tethys basin during the late cretaceous

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

the potential of organic walled dinoflagellate cysts for the reconstruction of past sea surface conditions in the southern ocean abstract in this study we investigate the potential of organic walled dinoflagellate cysts dinocysts as tools for quantifying past sea surface temperatures sst in the southern ocean for this purpose a dinocyst reference dataset has been formed based on 138 surface sediment samples from different circum antarctic environments the dinocyst assemblages of these samples are composed of phototrophic gonyaulacoid and heterotrophic protoperidinioid species that provide a broad spectrum of palaeoenvironmental information the relationship between the environmental parameters in the upper water column and the dinocyst distribution patterns of individual species has been established using the statistical method of canonical correspondence analysis cca among the variables tested summer sst appeared to correspond to the maximum variance represented in the dataset to establish quantitative summer sst reconstructions a modern analogue technique mat has been performed on data from three late quaternary dinocyst records recovered from locations adjacent to prominent oceanic fronts in the atlantic sector of the southern ocean these dinocyst time series exhibit periodic changes in the dinocyst assemblage during the last two glacial interglacial cycles during glacial conditions the relative abundance of protoperidinioid cysts was highest whereas interglacial conditions are characterised by generally lower cyst concentrations and increased relative abundance of gonyaulacoid cysts the mat palaeotemperature estimates show trends in summer sst changes following the global oxygen isotope signal and a strong correlation with past temperatures of the last 140 000 years based on other proxies however by comparing the dinocyst results to quantitative estimates of summer ssts based on diatoms radiolarians and foraminifer derived stable isotope records it can be shown that in several core intervals the dinocyst based summer ssts appeared to be extremely high in these intervals the dinocyst record seems to be highly influenced by selective degradation leading to unusual temperature ranges and to unrealistic palaeotemperatures we used the selective degradation index kt index to determine those intervals that have been biased by selective degradation in order to correct the palaeotemperature estimates we show that after correction the dinocyst based ssts correspond reasonably well with other palaeotemperature estimates for this region supporting the great potential of dinoflagellate cysts as a basis for quantitative palaeoenvironmental studies

carbonate ion effect on mg ca sr ca and stable isotopes on the benthic foraminifera oridorsalis umbonatus off namibia abstract we investigate the influence of carbonate system parameters carbonate ion concentration co32 carbonate ion saturation co32 on the trace element and stable isotope ratios in the endobenthic foraminifera oridorsalis umbonatus data from modern core top samples from the namibian continental slope suggest that the shell composition of this species is influenced by the chemistry of the pore water for these organic rich sediments the impact of ocean bottom water properties on both pore water and shell chemistry is surprisingly small sr ca correlates positively with co32 and to a lesser extent with co32 which is opposed to previous results a co32 decrease of 10 mol kg leads to an increase of 0 05 mmol mol in sr ca we observe a correlation between shell 18o corrected for temperature and 18o seawater and co32 however the variability of the corrected 18o is close to the analytical limit no clear dependences were observed for 13c and mg ca

evidence for thermohaline circulation reversals controlled by sea level change in the latest cretaceous fluctuations in oxygen 18 o and carbon 13 c isotope values of benthic foraminiferal calcite from the tropical pacific and southern oceans indicate rapid reversals in the dominant mode and direction of the thermohaline circulation during a 1 m y interval 71 70 ma in the maastrichtian at the onset of this change benthic foraminiferal 18 o values increased and were highest in low latitude pacific ocean waters whereas benthic and planktic foraminiferal 13 c values decreased and benthic values were lowest in the southern ocean subsequently benthic foraminiferal 18 o values in the indo pacific decreased and benthic and planktic 13 c values increased globally these isotopic patterns suggest that cool intermediate depth waters derived from high latitude regions penetrated temporarily to the tropics the low benthic 13 c values at the southern ocean sites however suggest that these cool waters may have been derived from high northern rather than high southern latitudes correlation with eustatic sea level curves suggests that sea level change was the most likely mechanism to change the circulation and or source s of intermediate depth waters we thus propose that oceanic circulation during the latest cretaceous was vigorous and that competing sources of intermediate and deep water formation linked to changes in climate and sea level may have alternated in importance

origin of rodingite forming fluids constrained by calcium and strontium isotope ratios in the leka ophiolite complex abstract alteration of oceanic lithosphere plays an important role in the global element cycling due to its dominant abundance on the earth s surface the formation of rodingites a ca rich lithology that occurs intimately associated with ca depleted serpentinite complexes is a widespread process during strong alteration of ocean floor lithologies and may represent a key process that influences the global ca cycle stable ca and radiogenic sr isotope compositions of rodingites and associated lithologies from the leka ophiolite complex norway preserve mantle signatures and thus provide evidence that the ca and sr sources for rodingitisation are dominantly mantle derived with no detectable seawater input the difference of 0 7 in 44 40ca of different phases found in the rocks is overall consistent with inter mineral fractionation at high temperatures related to the cao bonding environment but there are also indications for isotopic disequilibria between non cogenetic mineral phases while the water required for rodingite formation may originate from seawater the dissolved ca and sr involved in the mineral reactions during rodingitisation plg ca gros clz al can be balanced at a local scale being derived from the serpentinisation of mantle peridotites cpx1 h2o al srp chlorite ca cpx2 consequently rodingites do not act as a sink for oceanic ca instead they are a sink for ca released during serpentinisation of the oceanic lithospheric mantle

calibration of stable isotope composition of thoracosphaera heimii dinoflagellate calcite for reconstructing paleotemperatures in the intermediate photic zone in this study we investigate the temperature dependence of oxygen isotope ratios preserved in calcite formed by the dinoflagellate thoracosphaera heimii focusing primarily on the development of a geological proxy geochemical analysis of the calcite shells produced by this species represents a valuable proxy for reconstructing environmental conditions in the intermediate photic zone calibration is based on isotopic analysis from culture experiments performed in very dilute batch conditions as well as from near monospecific t heimii assemblages separated from core top sediments results are similar for both approaches and indicate that t heimii shells have oxygen isotope compositions close to equilibrium values predicted for inorganic calcite precipitation this calibration of the isotopic composition of dinoflagellate calcite indicates that monospecific assemblages of t heimii can be used to unravel paleotemperatures in the intermediate photic zone by applying isotopic transfer functions for equilibrium calcite in culture however a 18 o offset of a1 is observed at temperatures 17 c which falls below the natural temperature range of this species culture analyses also reveal a relationship between temperature and carbon isotope composition of calcite the mechanisms behind this relationship remain to be explored but their identification may provide a better understanding of carbon isotope systematics from both biogeochemical and geological perspectives comparison of the oxygen isotope composition of t heimii shells with that of shallower dwelling organisms such as the coccolithophores represents a valuable proxy for determining temperature gradients within the photic zone and may enable reconstruction of the evolution of the depth of the thermocline