authigenic uranium relationship to oxygen penetration depth and organic carbon rain we have measured u in benthic incubation chambers sediment pore waters and in sediments along the california continental margin sedimentary u uptake rates based on a combination of sediment pore water profiles and benthic incubation chambers generally agree with those predicted from sediment accumulation rate data this agreement supports the view that most of the continental margin sedimentary u is delivered by diffusion across the seawater sediment boundary the average rate of authigenic u accumulation for all the sites examined here is 0 2 nmol cm 2 y 1 which is consistent with published global estimates of sedimentary u uptake in addition the accumulation rate of u in sediments exhibits a nonlinear relationship with the oxygen penetration depth and a linear relationship with the organic carbon rain rate these relationships highlight the potential utility for the u accumulation rate as a proxy for these processes

eccentricity paced monsoon like system along the northwestern tethyan margin during the valanginian early cretaceous new insights from detrital and nutrient fluxes into the vocontian basin se france high resolution changes in terrigenous and nutrient fluxes into the vocontian basin northwestern tethyan margin were investigated for the late berriasian late valanginian time interval in order to assess the precipitation patterns in the source areas and to evaluate the effect of orbital forcing on the strength of the hydrological cycle in this study new high resolution mineralogical bulk rock and clay fraction and geochemical phosphorus and oxygen isotope data are used from the astronomically calibrated orpierre section for the first time kaolinite detrital and phosphorus accumulation rates kar dar and par are calculated and compared to a set of 547 geochemical and 260 mineralogical published data from other vocontian sections it appears that three regional increases in the kar document three successive humid episodes during the valanginian this is confirmed by contemporaneous increases in dar and partly also in par which highlight higher terrigenous and nutrient fluxes to the vocontian basin during these episodes concomitant decreases in the 18owhole rock signals may reflect higher sea surface temperatures during the early valanginian and the early late valanginian transition the occurrence of the three humid episodes is interpreted to relate to an orbital paced monsoonal circulation pattern through seasonally reversing movements of air mass heat and precipitation over the northwestern tethyan margin in particular based on the correlation between the 405 kyr eccentricity cycles and the kar signal obtained at orpierre an eccentricity influenced monsoonal circulation is proposed as the possible forcing factor behind these climatic patterns the average duration between the climaxes of the three regional wetter episodes is approximately 2 43 myr the wetter and likely also warmer episode at the early late valanginian transition is in step with the onset of the weissert episode in this regard the intensification of monsoonal driven precipitations appears as a possible external forcing factor leading or at least accelerating the important perturbation in the global carbon cycle associated with the weissert episode

orbital control on carbon cycle and oceanography in the mid cretaceous greenhouse we established a new high resolution carbonate carbon isotope record of the albian interval of the marne a fucoidi formation central apennines italy which was deposited on the southern margin of the western tethys ocean bulk carbonate sampled with 10 15 cm spacing was used for the construction of a continuous carbon isotope curve through the albian stage spectral analyses reveal prominent 400 kyr cyclicity in the 13c curve which correlates with milankovitch long eccentricity changes cycles occurring in our record resemble those observed in several cenozoic 13c records suggesting that a link between orbital forcing and carbon cycling existed also under mid cretaceous greenhouse conditions based on comparisons with cenozoic eccentricity carbon cycle links we hypothesize that 400 kyr cycles in the mid cretaceous were related to a fluctuating monsoonal regime coupled with an unstable oceanic structure which made the oceanic carbon reservoir sensitive to orbital variations in the tethys these oceanographic conditions lasted until the late albian and then were replaced by a more stable circulation mode less sensitive to orbital forcing

a study of cleaning procedures used for foraminiferal mg ca paleothermometry the various cleaning steps required for preparation of foraminiferal samples for mg ca and sr ca analysis are evaluated for their relative importance and effects on measured elemental ratios it is shown that the removal of silicate contamination is the most important step for the measurement of mg ca ratios in an example bulk sample mg ca decreases from 10 5 to 2 5 mmol mol 1 during clay removal oxidation of organic material causes a lowering of sample mg ca in the order of 10 or approximately 1 c when converted to temperature use of dilute acid leaching to remove adsorbed contaminants causes partial dissolution of the sample carbonate and a corresponding decrease in mg ca reductive treatment also causes dissolution of the sample and a decrease in the mg ca ratio of up to 10 15 sample preparation for sr ca analysis does not require the same degree of rigor as is necessary for mg ca work the within run reproducibility of the method described here for g ruber in a core top sample from the arabian sea was 1 8 mean sample ratio was 4 72 mmol mol 1 when converted to temperature this becomes 28 0 2 c the equivalent result for sr ca was 0 5 mean ratio 1 44 mmol mol 1

biotic and geochemical δ 18 o δ 13 c mg ca ba ca responses of globigerinoides ruber morphotypes to upper water column variations during the last deglaciation gulf of mexico abstract within the gulf of mexico gom the bryant canyon is exceptional in that rapid sedimentation sustained by high rates of terrigenous sediment delivery and surface marine productivity make this basin an excellent recorder of paleoenvironmental and paleoclimatic conditions we present a new 21 kyr record of sea surface temperature sst and local salinity changes from the nw gom core jpc 26 approximated from combined globigerinoides ruber morphotype specific 18 o and mg ca as well as ba ca which reflect the subtropical gom hydrographic dynamics and their relationship to both mississippi river discharges and climate evolution during the last deglaciation overall the reconstructed sst and sss related patterns reveal notable variations in amplitude between the analyzed morphotypes adding valuable insights to previously published g ruber w mixed gom records especially during the deglaciation bryant canyon meltwater flooding events bcdfs and associated sea surface freshening seem to be more pronounced than the sst reduction our mg ca derived sst records of both morphotypes g ruber sensu stricto s s and g ruber sensu lato s l show comparable general trends but with important sst differences t we interpret down core t as a record of changing upper water column hydrography with particular influence from the deglacial meltwater bcdfs or holocene bchfs flooding events during the warm intervals the deeper thicker and probably more seasonally persistent mixed layer led to more uniform thermal conditions for both g ruber morphotypes and therefore to a minimum t on the contrary during the cold and low salinity periods the shallower mixed layer favored more habitat divergence and caused a maximum thermal gradient in the well stratified upper water column overall this supports the notion that g ruber s s is consistently calcifying in warmer waters than g ruber s l either due to a shallower depth habitat or to a more summer weighted seasonal distribution moreover intra specific paired 13 c and ba ca differences show that g ruber s l is more sensitive to river water influence than g ruber s s due to its ability to change its depth habitat and therefore exploit optimal temperature salinity productivity stratification conditions during the low salinity events overall our observations support the current practice of treating the two g ruber morphotypes separately and further illustrate the necessity to map both their spatial and temporal distribution

a simple evaluation of cleaning procedures on fossil benthic foraminiferal mg ca 1 recent studies suggest that benthic foraminiferal mg ca may be useful in reconstructing deep water temperature changes during the quaternary and on longer timescales rosenthal et al 1997 lear et al 2000 martin et al 2002 because changes in deep water temperature may be small sample preparation could play an important role in reconstructing accurate temperatures from shell mg ca a simple examination of changes in measured shell chemistry of benthic foraminifera from two intervals subjected to increasingly rigorous cleaning reveals that fossil benthic foraminiferal samples cleaned by oxidation yield lower mg ca values than samples only rinsed and weak acid leached reductive cleaning further lowered the shell mg ca of one of the two benthic species examined lower mg ca values following oxidation and reduction appear to reflect removal of contaminant mg associated with remnant organic matter and adsorbed phases

fidelity of radially viewed icp oes and magnetic sector icp ms measurement of mg ca and sr ca ratios in marine biogenic carbonates are they trustworthy together improving interlaboratory reproducibility in both precision and accuracy of mg ca and sr ca determination in marine biogenic carbonates is critical in optimizing their utility as paleothermometers coupled with a need for uniform sample cleaning practices there is a need for more exacting methods and procedures across laboratories using varied instrumentation here we employ an intensity ratio matrix effect correction methodology to a suite of solution standards and biogenic carbonates foraminifera tests and a gastropod shell to investigate short term and long term mg ca and sr ca precision and accuracy by different instruments a magnetic sector inductively coupled plasma mass spectrometer icp ms and a radially viewed inductively coupled plasma optical emission spectrophotometer icp oes over an extended 1 0 24 5 mm ca concentration range both instruments have significant ca matrix effects for mg ca and somewhat less for sr ca over our working ca range 1 8 mm ca mg ca matrix effects are significant requiring correction and sr ca matrix effects are small to negligible occasionally requiring correction linear or logarithmic fit using a suite of matrix standards for both instruments the short term intrarun precision for a suite of solution standards is 0 2 1 rsd for mg ca and sr ca for both instruments a long term interrun precision of 0 9 is demonstrated for mg ca and 0 6 for sr ca on both instruments the accuracy of measured mg ca and sr ca values for short and long term standards is similar on both instruments at better than 1 0 5 on par with our long term precision an interinstrument comparison of the same measured suite of biogenic carbonates demonstrates that after accounting for matrix effects data generated on either instrument are essentially interchangeable within analytical precision to a high degree of fidelity

evidence for a complex valanginian nannoconid decline in the vocontian basin south east france the early cretaceous is punctuated by widespread biocalcification crises these are characterized by decrease in the carbonate platform growth and in the pelagic realm by a decline in nannoconus relative abundance in the calcareous nannofossil assemblages the valanginian nannoconus decline started before the positive 13c excursion characterizing the weissert event the nannoconid decline is investigated in two sections of the vocontian basin la charce and vergol which are biostratigraphically well constrained and contain wellpreserved calcareous nannofossils absolute and relative abundances of nannoconus show a polyphased decline with a first decrease in the interval from the campylotoxus to the verrucosum ammonite subzones before the positive 13c shift and a second decrease from the end of the peregrinus to the base of the radiatus ammonite zones concomitant with the long term decrease in 13c these two declines are separated by an important increase in the nannoconus abundance from the verrucosum to the peregrinus ammonite subzones concomitant with a slight short term decrease of 13c biometric analysis shows size changes of n steinmannii and n kamptneri along the nannoconid decline the patterns of abundances and size changes seem to be related to paleoenvironmental changes mainly characterized by a temperature decrease and variable nutrient supply the described valanginian nannoconid recovery seems to occur during the most intense phase of the cooling event and is recorded in the vocontian basin as well as in the atlantic and tethys oceans these spatial correlations suggest a supra regional character for the valanginian nannoconid recovery event best recorded in the vocontian basin and at low latitudes

bayesian hierarchical regression analysis of variations in sea surface temperature change over the past million years statistical challenges often preclude comparisons among different sea surface temperature sst reconstructions over the past million years inadequate consideration of uncertainty can result in misinterpretation overconfidence and biased conclusions here i apply bayesian hierarchical regressions to analyze local sst responsiveness to climate changes for 54 sst reconstructions from across the globe over the past million years i develop methods to account for multiple sources of uncertainty including the quantification of uncertainty introduced from absolute dating into inter record comparisons the estimates of local sst responsiveness explain 64 62 to 77 95 interval of the total variation within each sst reconstruction with a single number there is remarkable agreement between sst proxy methods with the exception of mg ca proxy methods estimating muted responses at high latitudes the indian ocean exhibits a muted response in comparison to other oceans i find a stable estimate of the proposed universal curve of change in local sst responsiveness to climate changes as a function of sin2 latitude over the past 400 000 years sst change at 45 n s is larger than the average tropical response by a factor of 1 9 1 5 to 2 6 95 interval and explains 50 35 to 58 95 interval of the total variation between each sst reconstruction these uncertainty and statistical methods are well suited for application across paleoclimate and environmental data series inter comparisons

environmental and biological controls on mg and li in deep sea scleractinian corals abstract deep sea scleractinian corals precipitate aragonite skeletons that provide valuable archives of past ocean conditions during calcification biological mediation causes variability in trace metal incorporation and isotopic ratios of the aragonite such that signals caused by environmental controls can be overwhelmed this complicates the interpretation of geochemical proxies used for paleo reconstructions in this study we examine the environmental controls on the mg li ratio of 34 individuals from seven genera of deep sea scleractinian corals desmophyllum balanophyllia caryophyllia enallopsammia flabellum trochocyanthus and lophelia in addition we examine the microscale distributions of mg and li in desmophyllum and balanophyllia using laser ablation inductively coupled plasma mass spectrometry la icp ms both mg ca and li ca ratios increased by more than a factor of two in the center of calcification regions compared to the outer fibrous regions of the coral skeleton as a result replicate 10 mg subsamples of coral show less variability in the mg li ratio than mg ca microscale mg and li results are consistent with rayleigh type incorporation of trace metals with additional processes dominating the composition within centers of calcification comparison of mg li to seawater properties near the site of collection shows that the ratio is not controlled by either carbonate ion or salinity it appears that temperature is the major control on the mg li ratio for all 34 samples the temperature correlation r2 0 62 is significantly better than for mg ca r2 0 06 for corals of the family caryophyllidae the r2 value increases to 0 82 with the exclusion of one sample that was observed to have an altered chalky texture despite this excellent correlation the scatter in the data suggests that the mg li ratio of deep sea corals cannot be used to reconstruct temperature to better than approximately 1 6 c without better temperature control and additional calibration points on modern coral samples

automated cleaning of foraminifera shells before mg ca analysis using a pipette robot the molar ratio of magnesium to calcium mg ca in foraminiferal calcite is a widely used proxy for reconstructing past seawater temperatures thorough cleaning of tests is required before analysis to remove contaminant phases such as clay and organic matter we have adapted a commercial pipette robot to automate an established cleaning procedure the mg cleaning protocol of barker et al 2003 efficiency of the automated nine step method was assessed through monitoring al ca of trial samples geob4420 2 core catcher planktonic foraminifera globigerinoides ruber globigerinoides sacculifer and neogloboquadrina dutertrei from this sample gave mg ca consistent with the habitat range of the three species and 40 60 sample recovery after cleaning comparison between manually cleaned and robot cleaned samples of g ruber white from a sediment core geob16602 showed good correspondence between the two methods for mg ca r 0 93 p 0001 n 27 average al ca in robot cleaned samples was 0 05 mmol mol showing that the samples are cleaned effectively by the robot the robot offers increased sample throughput as batch sizes of up to 88 samples blanks can be processed in 7 h with little intervention

high sea surface temperatures during the early cretaceous epoch the early cretaceous epoch about 145 100 million years ago is generally thought of as a greenhouse period with high atmospheric co2 concentrations1 and high global mean temperatures2 but evidence for episodes of cooler conditions and even transient glaciations has been proposed3 4 5 6 7 8 9 here we present sea surface temperature records spanning the period from 142 to 128 million years ago berriasian barremian ages from low and mid latitudes reconstructed using the tex86 palaeotemperature proxy during this period we find sea surface temperatures exceeding 32 c at 15 20 n and averaging 26 c at 53 s these temperatures substantially exceed modern temperatures at equivalent latitudes and are incompatible with the notion of consistently cooler conditions in the earliest cretaceous moreover we find little variability in the sea surface temperature records even during the valanginian carbon isotope excursion 138 135 million years ago which was thought to be associated with marked temperature fluctuations5 we conclude that the earliest cretaceous was characterized by a warm stable climate with a lower meridional temperature gradient than today

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

adaptation of a flow through leaching procedure for mg ca paleothermometry 1 mg ca ratios in planktonic foraminifera reflect calcification temperatures and are thus useful for sea surface temperature sst reconstructions despite the obvious utility of this paleoceanographic tracer problems of dissolution gametogenic calcification and contaminant phases have thus far limited confidence in mg ca based reconstructions here we show strong evidence of mg heterogeneity in foraminiferal calcite by sequentially measuring the composition of different forms of calcite ontogenetic gametogenic diagenetic in the same shells while monitoring and removing contaminant phases a new flow through method combines chromatographic technology and inductively coupled plasma mass spectrometry icp ms in a series of cleaning and dissolution reactions monitored continuously with time resolved analysis tra this combination of slow controlled dissolution and tra provides a complete elemental description of contaminant phases and sorts the cleaned calcium carbonate based on dissolution sensitivity examination of partially dissolved shells with electron microscopy suggests that the flow through method simulates the natural dissolution sequence and effectively separates the different calcite domains within a single foraminiferal shell heterogeneity of mg ca in foraminiferal calcite is clearly demonstrated in flow through analysis foraminiferal shells have initially high mg levels that decrease steadily throughout dissolution later dissolution yields lower mg ca which is likely due to a combination of subsurface calcification and biomineralization effects mg ca ratios from the most dissolution sensitive high mg portions of surface dwelling species in core tops are used to calculate calcification temperatures a comparison of late holocene core top data with world ocean atlas sst data indicates that the flow through method does yield viable sst estimates furthermore a depth transect in the eastern tropical pacific suggests that this approach provides the opportunity to extract initial calcification temperatures despite partial dissolution of foraminiferal shells

multi elemental composition of authigenic carbonates in benthic foraminifera from the eastern bering sea continental margin international ocean discovery program site u1343 abstract bering sea sediments represent exceptional archives offering the potential to study past climates and biogeochemistry at a high resolution however abundant hydrocarbons of microbial origin especially along the eastern bering sea continental margin can hinder the applicability of palaeoceanographic proxies based on calcareous foraminifera due to the formation of authigenic carbonates nonetheless authigenic carbonates may also bear unique opportunities to reconstruct changes in the sedimentary redox environment here we use a suite of visual and geochemical evidence from single specimens of the shallow infaunal benthic foraminiferal species elphidium batialis saidova 1961 recovered from international ocean discovery program iodp site u1343 in the eastern bering sea to investigate the influence of authigenic carbonates on the foraminiferal trace metal composition our results demonstrate that foraminiferal calcite tests act as a nucleation template for secondary carbonate precipitation altering their geochemistry where organoclastic sulphate reduction and anaerobic oxidation of methane cause the formation of low and high mg calcite respectively the authigenic carbonates can occur as encrusting on the outside and or inside of foraminiferal tests in the form of recrystallization of the test wall or as banding along natural laminations within the foraminiferal test walls in addition to mg authigenic carbonates are enriched in u ca mn ca fe ca and sr ca depending on the redox environment that they were formed in our results demonstrate that site specific u ca thresholds are a promising tool to distinguish between diagenetically altered and pristine foraminiferal samples important for palaeoceanographic reconstructions utilising the primary foraminiferal geochemistry consistent with previous studies u mn ratios of foraminifera at iodp site u1343 increase according to their degree of diagenetic alteration suggesting a potential response of authigenic u mn to the microbial activity in turn linked to the sedimentary redox environment

an evaluation of benthic foraminiferal u ca and u mn proxies for deep ocean carbonate chemistry and redox conditions the deep ocean is thought to have played a crucial role in modulating atmospheric co2 changes and thus reconstructions of deep ocean conditions can place important constraints on the past global carbon cycle some previous studies suggested that foraminiferal u ca could be used to infer seawater carbonate chemistry changes but others showed complications from diagenesis and temperature a recent down core study suggested that foraminiferal u mn may be used for sedimentary redox conditions but no core top work has been done to investigate factors affecting u mn we investigate controlling factors on u ca and u mn in two benthic foraminiferal species from 120 global core tops and three atlantic sediment cores our core top data reveal no significant correlation between core top benthic u ca and carbonate system parameters the lack of an influence of deep water co32 on u ca is further supported by our down core results together our data highlight complications to use benthic u ca for deep water carbonate chemistry reconstructions although no correlation is found between core top u mn and hydrographic data high resolution u mn and u ca in core tno57 21 show similar patterns to authigenic u au and vary in tandem with atmospheric co2 on millennial timescales changes in u mn u ca and au in tno57 21 may reflect post depositional diagenesis linked to sedimentary oxygen which is controlled by subantarctic surface productivity and ventilation of deep south atlantic in the past we suggest that benthic u mn and u ca may be used as auxiliary indicators for past sedimentary redox conditions and along with other proxies could reflect deep water oxygenation this article is protected by copyright all rights reserved

systematic change of foraminiferal mg ca ratios across a strong salinity gradient abstract the mg ca ratio of foraminiferal calcite is an important proxy for estimating past ocean temperatures used in conjunction with 18 o of foraminiferal calcite it allows deconvolution of temperature and ice volume signals to infer past ocean temperatures and salinities assuming the relationship between seawater 18 o and salinity is known such work assumes that temperature is the only or at least the dominant environmental controller of foraminiferal mg ca the semi enclosed mediterranean sea where salinity varies from 36 to 40 psu over a seasonal temperature range of between only 5 c to 8 c provides a relevant setting to test this assumption outside the laboratory in this study planktonic foraminifera o universa g siphonifera g bulloides and g ruber white and pink were picked from 11 box core tops spanning the mediterranean salinity gradient and analysed for their trace element concentrations mg ca ratios are higher for the associated calcification temperatures than in other regions where calibrations have been conducted and correlate poorly with calcification temperature mg ca ratios are particularly high for samples from the eastern mediterranean where salinity is unusually high correlations of mg ca with the calcification salinity are statistically significant with mg ca changing by 15 59 per psu suggesting that salinity may act as a control on mg ca ratios in addition to the dominant temperature control we show that contamination by non carbonate material and diagenetic high mg carbonate overgrowths cannot account for the observed trend of increasing mg ca with salinity a relationship between mg ca and salinity is also suggested by re analysis of calibrations from open ocean settings these new mediterranean results are from a region with unusually high salinity but suggest that the effects of salinity on the mg ca palaeothermometer should be considered even in open ocean settings particularly where large salinity changes occurred in the past

environmental controls on mg ca in neogloboquadrina incompta a core top study from the subpolar north atlantic magnesium calcium paleothermometry is an established tool for reconstructing past surface and deep sea temperatures however our understanding of non thermal environmental controls on the uptake of mg into the calcitic lattice of foraminiferal tests remains limited here we present a combined analysis of multiple trace element calcium ratios and stable isotope 18o and 13c geochemistry on the subpolar planktonic foraminifera neogloboquadrina incompta to assess the validity of mg ca as a proxy for surface ocean temperature we identify small size specific offsets in mg ca and 18oc values for n incompta that are consistent with depth habitat migration patterns throughout the life cycle of this species additionally an assessment of non thermal controls on mg ca values reveals that 1 the presence of volcanic ash 2 the addition of high mg abiotic overgrowths and 3 ambient seawater carbonate chemistry can have a significant impact on the mg ca to temperature relationship for carbonate ion concentrations of values 200 mol kg 1 we find that temperature exerts the dominant control on mg ca values while at values 200 mol kg 1 the carbonate ion concentration of seawater increases the uptake of mg thereby resulting in higher than expected mg ca values at low temperatures we propose two independent correction schemes to remove the effects of volcanic ash and carbonate ion concentration on mg ca values in n incompta within the calibration data set applying the corrections improves the fidelity of past ocean temperature reconstructions

seismic activity offshore martinique and dominica islands central lesser antilles subduction zone from temporary onshore and offshore seismic networks this work focuses on the analysis of a unique set of seismological data recorded by two temporary networks of seismometers deployed onshore and offshore in the central lesser antilles island arc from martinique to guadeloupe islands during the whole recording period extending from january to the end of august 2007 more than 1300 local seismic events were detected in this area a subset of 769 earthquakes was located precisely by using hypoellipse we also computed focal mechanisms using p wave polarities of the best azimuthally constrained earthquakes we detected earthquakes beneath the caribbean forearc and in the atlantic oceanic plate as well at depth seismicity delineates the wadati benioff zone down to 170 km depth the main seismic activity is concentrated in the lower crust and in the mantle wedge close to the island arc beneath an inner forearc domain in comparison to an outer forearc domain where little seismicity is observed we propose that the difference of the seismicity beneath the inner and the outer forearc is related to a difference of crustal structure between the inner forearc interpreted as a dense thick and rigid crustal block and the lighter and more flexible outer forearc seismicity is enhanced beneath the inner forearc because it likely increases the vertical stress applied to the subducting plate

paleoclimate history of galapagos surface waters over the last 135 000 yr abstract records of planktonic and benthic foraminiferal 18 o and planktonic mg ca from core tr163 22 just northwest of the galapagos islands reveal a detailed 250 450 year resolution climate history of the region over the last 135 thousand years kyr sea surface temperatures ssts reconstructed from g ruber mg ca averaged 24 3 0 4 c during the holocene 22 6 0 6 c during marine isotope stage mis 2 3 and 4 and 26 0 0 9 c during mis 5e changes in sst lead changes in both planktonic and benthic 18 o by an average 3 kyr suggesting that sst changes in this region predated continental ice volume changes changes in sst display clear millennial scale variability especially in marine isotope stage 3 with behavior somewhat similar to antarctic proxy air temperature and south pacific sst records removal of the temperature component from the planktonic 18 o record demonstrates that glacial interglacial 18 o water changes at this site were 1 0 0 2 similar to estimates for mean ocean shifts implying that salinity changes due to regional hydrological variation between the last glacial maximum and holocene in the galapagos region were minimal comparison between the tr163 22 sst record and an sst record from core tr163 19 north of the equatorial front reveals a largely similar broad scale climate history suggesting that changes in the galapagos region were caused by large scale forcing rather than by local or regional dynamical changes changes in atmospheric greenhouse forcing are the most plausible explanation for the observed large scale climate changes in the eastern equatorial pacific

extended calibration of cold water coral ba ca using multiple genera and co located measurements of dissolved barium concentration abstract biological productivity and ocean circulation are both important oceanographic variables that control the distribution of dissolved barium in the ocean interior ba sw the ability to accurately reconstruct ba sw will provide key constraints on these processes in the past the geochemistry of cold water corals has the potential to unlock paleoceanographic records at spatial and temporal resolutions not available using other sedimentary archives previous studies have suggested that the ba ca ratio of coral skeletons is linearly related to ba sw however these efforts have used a limited number of species sparse global seawater databases or have not explicitly measured the ba ca ratio here we investigate the ba ca ratio in a well constrained set of cold water scleractinian aragonitic corals as a proxy for ba sw using 58 specimens from 7 coral genera along with co located measurements of ba sw we find that traditional chemical cleaning procedures do not significantly affect the ba ca ratio of cold water coral skeletons allowing rapid sample throughput we also determine that intra sample variation in ba ca ratios can be reduced by using larger sample sizes e g 20 mg by combining our results with existing data we find that cold water coral ba ca is linearly related to ba sw according to the relationship ba ca mol mol 0 15 0 02 basw nmol kg 2 5 1 4 r2 0 7 we observe no species specific vital effects in cold water coral ba ca ratios but site specific effects could be a factor nevertheless our results highlight the potential of ba ca in cold water corals to reconstruct biological and physical changes in the ocean interior

modeling 100 000 year climate fluctuations in pre pleistocene time series a number of pre pleistocene climate records exhibit significant fluctuations at the 100 000 year 100 ky eccentricity period before the time of such fluctuations in global ice volume the origin of these fluctuations has been obscure results reported here from a modeling study suggest that such a response can occur over low latitude land areas involved in monsoon fluctuations the twice yearly passage of the sun across the equator and the seasonal timing of perihelion interact to increase both 100 ky and 400 ky power in the modeled temperature field the magnitude of the temperature response is sufficiently large to leave an imprint on the geologic record and simulated fluctuations resemble those found in records of triassic lake levels

authigenic uranium in foraminiferal coatings a proxy for ocean redox chemistry the rate of uranium accumulation in oceanic sediments from seawater is controlled by bottom water oxygen concentrations and organic carbon fluxes two parameters that are linked to deep ocean storage of co2 to investigate glacial interglacial changes in what is known as authigenic u we have developed a rapid method for its determination as a simple addition to a procedure for foraminiferal trace element analysis foraminiferal calcite acts as a low u substrate u ca 15 nmol mol upon which authigenic u accumulates in reducing sediments we measured a downcore record of foraminiferal u ca from odp site 1090 in the south atlantic and found that u ca ratios increase by 70 320 nmol mol during glacial intervals there is a significant correlation between u ca records of benthic and planktonic foraminiferal species and between u ca and bulk sediment authigenic u these results indicate that elevated u ca ratios are attributable to the accumulation of authigenic u coatings in sediments foraminiferal mn ca ratios were lower during the glacial intervals suggesting that the observed u accumulation on the shells is not directly linked to u incorporation into secondary manganese phases thus foraminiferal u ca ratios may provide useful information on past changes in sediment redox conditions

deglacial abrupt climate change in the atlantic warm pool a gulf of mexico perspective 1 during the last deglaciation greenland ice core and north atlantic sediment records exhibit multiple abrupt climate events including the younger dryas cold episode 12 9 11 7 ka however evidence for the presence of the younger dryas in the gulf of mexico gom and the relationship between gom sea surface temperature sst and high latitude climate change is less clear we present new mg ca sst records from two varieties of the planktonic foraminifer globigerinoides ruber white and pink to assess northern gom sst history from approximately 18 4 10 8 ka thirty five accelerator mass spectrometry ams 14c dates from orca basin core md02 2550 provide excellent age control and document high sedimentation rates 40 cm kyr g ruber white and pink mg ca sst data exhibit increases 4 6 0 6 c and 2 2 0 5 c respectively from at least 17 8 16 6 ka with nearly decadal resolution that are early relative to the onset of the bolling allerod interstadial moreover g ruber white sst decreases at 16 0 14 7 ka 1 0 0 5 c and 12 8 11 6 ka 2 4 0 6 c correlate to the oldest and younger dryas in greenland and cariaco basin the g ruber pink sst record which reflects differences in seasonality and or depth habitat is often not in phase with g ruber white and closely resembles antarctic air temperature records overall it appears that orca basin sst records follow antarctic air temperature early in the deglacial sequence and exhibit enhanced seasonality during greenland stadials

asymmetric response of the subtropical western south atlantic thermocline to the dansgaard oeschger events of marine isotope stages 5 and 3 abstract the last glacial period 116 11 7 ka bp was an interval characterized by a sequence of abrupt millennial scale events well documented in greenland and antarctica ice cores throughout this period greenland cold stadials were accompanied by warm conditions in the thermocline to intermediate waters of the atlantic ocean that may have played a role in both the basal melting of ice shelves and the rapid atmospheric warming during the onset of warm interstadials climate model simulations indicated an accentuated response of the subtropical western south atlantic thermocline to the disturbances in the atlantic circulation such works encourage investigations upon thermocline deep dwelling planktic foraminifera in this region however a study with this aim was not performed here we present a paleoceanographic reconstruction from the subtropical western south atlantic based on the thermocline planktic foraminifera globorotalia inflata our high resolution 18o record for the last glacial period presents a millennial scale variability that strongly resembles the structure of the greenland dansgaard oeschger cycles during marine isotope stage mis 5 during mis 3 this millennial scale variability is absent or considerably dampened mg ca derived temperature and seawater 18o corrected for ice volume for the mis 5 interval demonstrate that the region was warmer and saltier colder and fresher during early glacial stadials interstadials our data suggest a reorganization of the northward heat transport throughout the last glacial in which regions as far south as 24 s acted as heat reservoirs in periods of weakened atlantic meridional overturning circulation during mis 5 but not necessarily or only marginally during mis 3

preferential dissolution of benthic foraminiferal calcite during laboratory reductive cleaning we have investigated the effect of cleaning procedures on eight element ca ratios in three widely used benthic foraminifera species from core top and down core sediments two cleaning techniques were employed 1 comparison between mg cleaning and cd cleaning methods and 2 comparison between the various constituent reagents li ca b ca and sr ca ratios remained unchanged for samples subjected to different treatments but mg ca mn ca zn ca cd ca and u ca were substantially decreased when foraminifera shells were cleaned with reagents containing citrate in contrast no significant decreases in element ca ratios were observed for samples cleaned in n2h4 without citrate indicating that the role of n2h4 was insignificant during reductive cleaning and that citrate is responsible for decreases of mg ca mn ca zn ca cd ca and u ca decreases in these ratios are most likely due to 1 removal of contaminant particles enriched in mg mn zn cd and u and or 2 preferential leaching of caco3 by the formation of stable metal complexes through chelation between citrate and metals heterogeneously distributed in foraminiferal shells due to the negligible effect of n2h4 and preferential dissolution of caco3 during reductive cleaning it is suggested that the reductive cleaning step should be omitted and the mg cleaning method barker et al 2003 could be employed to clean foraminiferal shells for trace element measurements

seasonal and interannual variation in santa barbara basin water temperatures observed in sediment trap foraminiferal mg ca 1 we have generated a santa barbara basin sediment trap mg ca record to evaluate culture based calibration equations for the temperate subpolar planktonic foraminiferal species globigerina bulloides and neogloboquadrina pachyderma dextral g bulloides and n pachyderma mg ca are significantly correlated with seasonal variations in temperature of the near surface and subthermocline depths respectively the average deviation between mg based and 18o based temperature estimates is 0 6 c for g bulloides and 0 8 c for n pachyderma differences between mg derived temperatures and instrumental temperatures may be due to cleaning methods environmental factors such as seasonal variations in foraminiferal depth habitats or possible secondary effects on mg ca core top mg ca of both g bulloides and n pachyderma is in excellent agreement with average values from the sediment trap lending strong support for the interpretation of downcore mg ca from these species as annual average near surface and thermoclinal temperatures

surface hydrographic and water mass variability in the eastern equatorial pacific during interglacial like marine isotope stage 14 surface temperature and water masses variability in the eastern equatorial pacific eep is sensitive to global climate changes in response to either northern southern hemisphere forcing or low latitude atmosphere ocean feedback high latitude processes can influence tropical oceans via atmospheric bridges and oceanic tunnels whereas perturbations in the low latitude atmosphere ocean modulate the behavior of low latitude oceans for climate paradoxes of prolonged warmth mis marine isotope stage 15 13 little has known about any causes or any possible tele connections between the eep and high low latitudes because lack of observations to address this issue multiple sea surface temperature sst records i e faunal transfer function based mg ca ratio on mono species and uk 37 derived temperature estimates and faunal derived water masses are generated from the eep core odp 1240 our results reveal a glacial eep mis 14 cooling 1 2 c with higher eastern boundary current faunal abundances as compared to adjacent interglacial stages in a glacial mis 14 scenario we suggest that the eep areas would receive more nutrient rich cold waters from high latitudes via the peru chile current the atmospheric bridge of a northwardly intertropical convergence zone itcz shift and the resulting heat moisture transport across the eastern equatorial atlantic eea would weaken the magnitude of the eep cold tongue in mis 14 we also think of another scenario in that the orbital variations in glacial mis 14 was characterized by higher obliquity fluctuations lower eccentricity precession the orbital variations shape an inter hemispheric asymmetry with higher seasonality this scenario could result in a stagnant an inactive atlantic meridional ocean circulation and northward shifts in the itcz southward displacement of westerlies in the southeastern pacific during mis 14 the retreat of the west antarctic sea ice and enhancement of the antarctic circumpolar current would also bring less high latitude cold upwelled water the subantarctic mode water antarctic intermediate water into the eastern tropical pacific atlantic oceans we suggest that a diminished la nina like condition and a relatively weakened eep eea cold tongue developed in glacial mis 14 compared to other glacial mis in the late quaternary the interglacial like mis 14 is therefore characterized by a small magnitude of eastern tropical upwelling areas and greater extension of western pacific atlantic warm surface waters such amplifications in glacial mis 14 could lead to less fluctuation of termination vi and persistent warmth in mis 15 13

core top calibration of mg ca in tropical foraminifera refining paleotemperature estimation 1 optimal use of mg ca as a paleotemperature proxy requires establishing calibrations for different species of foraminifera and quantifying the influence of dissolution to achieve this goal we have measured mg ca and 18o in a series of tropical and subtropical core tops including four depth transects the ceara rise the sierra leone rise and the rio grande plateau in the atlantic and the ontong java plateau in the pacific focusing on spinose mixed layer dwelling species globigerinoides ruber and globigerinoides sacculifer and nonspinose thermocline dwelling neogloboquadrina dutertrei shell mg ca in g sacculifer is 5 15 lower than in g ruber while n dutertrei mg ca is 49 55 lower than in g ruber this statistically significant offset has allowed us to establish different calibrations for each species multilinear regression analysis was used to develop calibration equations that include a correction term for the dissolution effect on mg ca in foraminiferal calcite presented in this paper are two sets of calibrations one set using core depth as a dissolution correction and another using co32 as a dissolution parameter the calibrations suggest that g ruber is the most accurate recorder of surface temperature while g sacculifer records temperatures below the surface at 20 30 m the depth habitat of n dutertrei is more uncertain owing to the wide range in habitat depths depending on hydrographic conditions but on average mg ca and 18o data suggest it is at 50 m of the three species n dutertrei is the most sensitive to dissolution up to 23 decrease in shell mg ca per km while g sacculifer is the most resistant

influence of volcanic shards on foraminiferal mg ca in a core from the galapagos region 1 variability in the mg fe al mn and u to ca composition of the planktonic foraminifera g ruber in core tr163 22 an 8 8 m long piston core from just northwest of the galapagos islands reveals distinct patterns of downcore behavior mg ca data follow a general climatic trend with lower values during cold intervals i e marine isotope stages mis 2 4 and higher values during warm intervals i e mis 1 and 5 fe ca and al ca data reveal distinct intervals in which concentrations are elevated tenfold or more over baseline values with highly variable elemental ratios in these intervals the mg ca data are highly correlated with the fe ca and al ca data in these intervals with slopes of 1 13 0 03 and 0 66 0 07 mole mole respectively examination of the sediments from these intervals reveals that they are rich in volcanic debris that is likely derived from galapagos volcanic rocks the presence of small amounts of this volcanic debris can bias shell mg ca to elevated values attempts to use enhanced cleaning to remove the volcanic particles were largely unsuccessful the most successful strategy is to use the fe ca and al ca from the shell digests along with the fe to mg ratio of the volcanic debris to correct the mg ca data for al silicate contamination in which case the corrected data more clearly reveal the primary climatological patterns mn ca and u ca data are characterized by cycles of 20 200 cm length with mn ca having a distinct trend toward higher values between the core top and 200 cm these trends appear to be related to diagenetic coatings on the foraminifera shells most likely in the form of mn carbonates

persistent sea surface temperature and declined sea surface salinity in the northwestern tropical pacific over the past 7500 years abstract to understand holocene climate evolutions in low latitude region of the western pacific paired 18o and mg ca records of planktonic foraminifer globigerinoides ruber 250 300 m sensu stricto s s from a marine core ori715 21 121 5 e 22 7 n water depth 760 m underneath the kuroshio current kc off eastern taiwan were analyzed over the past 7500 years the geochemical proxy inferred sea surface temperature sst hovered around 27 28 c and seawater 18o 18ow slowly decreased 0 2 0 4 for two kc sites at 22 7 and 25 3 n comparison with a published high sst and high salinity equatorial tropical pacific record md98 2181 located at the mindanao current mc at 6 3 n reveals an anomalous time interval at 3 5 1 5 kyr ago before 1950 ad sst gradient between the mc site and two kc site decrease from 1 5 2 0 c to only 0 1 c and 18ow from 0 1 0 3 to 0 for this 2 kyr time window the high sst and low gradient could result from a northward shift of the north equatorial current which implies a weakened kc the long term descending 18ow and increasing precipitation in the entire low latitude western pacific and the gradually decreasing east asian summer monsoonal rainfall during middle to late holocene is likely caused by different land and ocean responses to solar insolation and or enhanced moisture transportation from the atlantic to pacific associated with the southward movement of itcz

comparison of mg ca and alkenone based sea surface temperature estimates in the fresh water influenced gulf of guinea eastern equatorial atlantic this study presents a comparison of sea surface temperature sst estimates based on mg ca ratios of globigerinoides ruber and alkenone unsaturation index u37 k in core sediment recovered from the gulf of guinea eastern equatorial atlantic mg ca and u37 k based sst estimates yield fairly comparable results for the time interval 21 000 14 500 years and for the late holocene the early and middle holocene however are largely characterized by a discrepant trend with warm mg ca and cold u37 k based sst estimates this discrepant sst trend is accompanied by low sea surface salinity estimates high riverine runoff and biogenic sediment which is characterized by high biogenic opal content low carbonate content and relatively low alkenone concentration we hypothesize that the discrepancy in the reconstructed ssts during the middle and early holocene presumably suggests a period of elevated riverine input of dissolved silica and dominantly siliceous phytoplankton bloom in a low saline and warm surface water while alkenone producers were likely prevalent in a season of cold sst and low riverine silica input this study suggests that changes in the local hydrography and nutrient input have strong influence on the u37 k based sst estimate that may be unraveled by combining different sst proxies

new spatial mg ca temperature calibrations for three arctic benthic foraminifera and reconstruction of north iceland shelf temperature for the past 4000 years 1 we have developed cold end mg ca temperature calibrations for three common arctic benthic foraminifera islandiella norcrossi helenae melonis barleeanus and cassidulina neoteretis and compare the three calibrations in a late holocene downcore record 0 4000 cal yr b p the calibration and downcore trends for the three arctic species extend the observation that mg incorporation into benthic foraminifera is species specific for the calibration we use a set of ctd casts bottom water 18oseawater measurements and surface grab samples collected from the iceland margin cruise b997 and the greenland margin cruise bs1191 water depth of sites used ranges from 165 to 656 m while spatial bottom temperature ranges from 0 to 7 c mg ca values ranged from 1 02 to 1 47 for i norcrossi helenae 0 64 to 2 21 for m barleeanus and 0 93 to 1 38 mmol mol for c neoteretis we calibrated mg ca content against isotopic calcification temperature calculated using t 16 9 4 0 18ocalcite corrected for vital effect 18oseawater exponential calibrations for the three species are as follows i norcrossi helenae mg ca 1 051 0 03 exp 0 060 0 011 t m barleeanus mg ca 0 658 0 07 exp 0 137 0 020 t and c neoteretis mg ca 0 864 0 07 exp 0 082 0 020 t on the basis of mg ca in these benthic species the downcore record from core md99 2269 is reconstructed bottom temperature values are interpreted to reflect variable inflow of atlantic and arctic water to the north iceland shelf during the last 4000 cal yr b p all three reconstructions show a decline by 0 1 c per century from circa 1500 0 cal yr b p which coincides with an increase in arctic benthic foraminifera abundances and a rise in sea ice proxies in the same core intriguingly c neoteretis diverges periodically to higher average temperature atlantic water conditions than shown by m barleeanus or i norcrossi helenae which both show arctic water temperature circa 1500 4000 cal yr b p

insolation control on the late cretaceous hydrological cycle and tropical african climate global climate modelling linked to marine climate records data from late cretaceous paleoclimate simulations and their linkage to a geological model derived from long term high resolution proxy data indicate and support strong relationships between african climate and tropical atlantic sedimentation here we present results from an interdisciplinary study by varying only one parameter in the set of orbital boundary conditions of the numeric model we focus on the climatic impact of precessional forcing on the global and regional climate system as a result new insights to the internal dynamics of climate the different compartments and fluxes of the hydrological cycle and finally the sedimentary response within the oceanic realm during greenhouse conditions have been approached the climate models suggest that insolation changes at 25 55 s are the trigger for cyclic variations of the tropical hydrological cycle of northern africa between the various models a maximum difference in insolation at the top of the atmosphere of 14 w m2 is needed to produce the documented changes in the hydrological cycle first of all the simulations do not suggest any substantial latitudinal movement of the itcz over the course of one precessional cycle the models rather indicate cross latitudinal variation of pressure systems and variation in the magnitude and direction of surface winds linking tropical africa to the mid southern latitudes this cross latitudinal atmospheric teleconnection denotes a reduced role of the tropics as driver of cretaceous climate system therefore the linkage of proxy based geological and numeric models rather supports the idea that tropical atlantic black shale formation in the late cretaceous was ultimately triggered by climate change in mid southern latitudes with precipitation and river discharge being the transport mechanisms as a hypothesis that will be tested in the near future we speculate that the mid latitudes represent the ultimate region of climate signal formation during times of extreme global warmth

the use of foraminiferal uranium calcium ratios as an indicator of changes in seawater uranium content we examine the utility of the uranium u content of planktonic foraminifera tests as an indicator of past changes in seawater u content the u ca ratio in foraminifera from atlantic and caribbean cores is constant in the holocene and decreases by 25 during the last glacial period magnesium calcium mg ca ratios of the same samples show similar trends while the timing of the u ca changes appears to be associated with glacial interglacial changes the magnitude of the change is too large to be caused by variations in the extent of anoxic or suboxic sediments or by changes in riverine input we assume that the same process produced changes in both u ca and mg ca ratios because of a strong correlation between the two ratios partial dissolution of the calcite is ruled out because we observe the same changes in well preserved cores from basins with opposite dissolution histories we also reject exchange between foraminiferal and pore water u because of the oxic depositional environment of both cores and because of the consistency in the u ca trends from cores in different parts of the ocean we suggest that the observed foraminiferal u ca and mg ca trends may be the result of a temperature effect on the incorporation of these metals if this is true it introduces the possibility of a new paleotemperature indicator but complicates the use of u ca ratios in planktonic foraminifera tests as an indicator of past seawater u changes

global dissolution effects on planktonic foraminiferal mg ca ratios controlled by the calcite saturation state of bottom waters mg ca ratios of planktonic foraminiferal tests are important tools for reconstructing past ocean temperatures at different levels of the upper water column yet numerous studies suggest a significant influence of calcite dissolution on mg ca ratios lowering their initial signal recorded within a planktonic foraminiferal habitat to determine the effect of dissolution this study presents mg ca ratios of eight planktonic foraminiferal species from the south china sea sediment surface continuously decreasing with increasing water depth the mg ca ratios also decrease with calcite saturation states close to and below saturation bottom water delta co32 40 mu mol kg 1 this preservation pattern compares well with examples of mg ca dissolution from the tropical atlantic ocean and is independent of the foraminiferal species merging a global data set by separate normalization of 79 mg ca data sets from the pacific atlantic and indian oceans which removes thermal differences between the ocean regions and foraminiferal species enabled us to quantify a global decrease in planktonic foraminiferal mg ca ratios of 0 054 0 019 mu mol mol 1 per mol kg 1 below a critical threshold for dissolution of 21 3 6 6 mu mol kg 1 the absolute decline in mg ca ratios which is similar for all species affects temperature estimates from sub thermocline species more strongly than those from shallow dwellers the water depth of this critical threshold in the global oceans shoals from 3 5 km in the north atlantic to 0 5 km in the north pacific based on calculations of the global calcite saturation state from 6321 hydrographic stations above this critical threshold mg ca ratios are well preserved and paleotemperature estimates are broadly unaffected by dissolution

climatic precession is the main driver of early cretaceous sedimentation in the vocontian basin france evidence from the valanginian orpierre succession the valanginian sediments outcropping in the vocontian basin se france exhibit striking marl limestone alternations which were formed under the influence of orbital forcing and which have served for geochronological and paleoenvironmental studies previous studies have suggested an obliquity forcing during the late valanginian interval reflecting specific environmental conditions such as polar ice using a cyclostratigraphic correlation of previously studied sections and performing time series analysis on the most complete late valanginian interval we argue that the climatic precession cycle is the primary driver of these marl limestone alternations in addition we highlight the modulation of the precession by the 100 and 405 kyr eccentricity cycles we suggest that the cyclostratigraphic misinterpretation i e obliquity forcing hypothesis results mainly from poorly preserved 405 kyr eccentricity cycles due to local hiatuses and or missed beats this study shows the potential of cyclostratigraphic correlations for the detection and quantification of differential hiatuses and or missed beats within intrabasinal sequences hence providing constraints on cyclostratigraphic interpretations the recorded 405 kyr eccentricity cycle is of prominent amplitude and controlled the fourth order sea level sequences these latter are faithfully detected through cyclostratigraphically inferred sedimentation rate finally we show that the well known pronounced lithostratigraphic markers intervals in the basin were orbitally paced by the 405 kyr eccentricity extrema this is a good argument for the strong impact of this cyclicity on the sedimentary processes especially during greenhouse periods

millennial scale variability of deep water temperature and δ18odw indicating deep water source variations in the northeast atlantic 0 34 cal ka bp 1 paired measurements of mg ca and 18occ calcite 18o in benthic foraminifera from a deep sea core recovered on the iberian margin md99 2334k 37 48 n 10 10 w 3 146 m have been performed in parallel with planktonic 18occ analyses and counts of ice rafted debris ird the synchrony of temperature changes recorded in the greenland ice cores and in north atlantic planktonic 18occ allows the proxy records from md99 2334k to be placed confidently on the gisp2 time scale this correlation is further corroborated by ams 14c dates benthic mg ca measurements in md99 2334k permit the reconstruction of past deep water temperature tdw changes since 34 cal ka bp calendar kiloyears before present using these tdw estimates and parallel benthic 18occ measurements a record of deep water 18o 18odw has been calculated results indicate greatly reduced tdw in the deep northeast atlantic during the last glaciation until 15 cal ka bp when tdw warmed abruptly to near modern values in parallel with the onset of the bolling allerod interstadial subsequently tdw reverted to cold glacial values between 13 4 and 11 4 cal ka bp in parallel with the younger dryas cold reversal and the h0 ice rafting event similar millennial scale tdw changes also occurred during the last glaciation indeed throughout the last 34 cal ka millennial 18odw and tdw changes have remained well coupled and are linked with ird pulses coincident with heinrich events 3 2 1 and the younger dryas when transitions to lower tdw and 18odw conditions occurred in general millennial tdw and 18odw variations recorded in md99 2334k describe an alternation between colder low 18odw and warmer high 18odw conditions which suggests the changing local dominance of northern sourced north atlantic deep water nadw versus southern sourced antarctic bottom water aabw the observed similarity of the tdw and gisp2 18oice records would therefore suggest a common component of variability resulting from the coupling of nadw formation and greenland climate a link between greenland stadials and the incursion of cold low 18odw aabw in the deep northeast atlantic is thus implied which contributes to the relationship between greenland climate and the millennial benthic 18occ signal since 34 cal ka bp

climate impact of late quaternary equatorial pacific sea surface temperature variations magnesium calcium data from planktonic foraminifera in equatorial pacific sediment cores demonstrate that tropical pacific sea surface temperatures ssts were 2 8 0 7 c colder than the present at the last glacial maximum glacial interglacial temperature differences as great as 5 c are observed over the last 450 thousand years changes in sst coincide with changes in antarctic air temperature and precede changes in continental ice volume by about 3 thousand years suggesting that tropical cooling played a major role in driving ice age climate comparison of sst estimates from eastern and western sites indicates that the equatorial pacific zonal sst gradient was similar or somewhat larger during glacial episodes extraction of a salinity proxy from the magnesium calcium and oxygen isotope data indicates that transport of water vapor into the western pacific was enhanced during glacial episodes

determination of carbonate bound barium in foraminifera and corals by isotope dilution plasma mass spectrometry abstract the trace metal content of biogenic carbonates reflects seawater concentrations only if one can selectively determine the portion of metal bound into the ca lattice site we have developed a procedure to purify benthic foraminifera shells of extraneous sedimentary organic and diagenetic ba the purification procedure involves treatment similar to those developed for the determination of cd in foraminifera shells but with the addition of an alkaline dtpa step to dissolve away sedimentary barite associated with the shells paired sample studies and partial dissolution of benthic foraminifera confirm the effectiveness of this procedure ba ca is determined on the purified shells by measurement of ba by isotope dilution inductively coupled plasma mass spectrometry id icp ms and ca by flame atomic absorption long term precision of the foraminifera ba ca determinations is between 2 and 3 we have also developed a rapid procedure for id icp ms determination of ba in aragonite coral samples with routine precisions of

orbital tuning of a lower cretaceous composite record maiolica formation central italy 1 a high resolution pelagic bulk carbonate stable isotope record from a central tethyan lower cretaceous composite section is presented three well exposed sedimentary sequences chiaserna monte acuto bosso and gorgo a cerbara sections central italy cropping out throughout the maiolica formation were correlated by a detailed magnetostratigraphy lithostratigraphy and calcareous plankton biostratigraphy in order to reconstruct a continuous composite record from the middle berriasian to the lower aptian the integrated stratigraphy of the three sequences provided an accurate time framework for the new high resolution c isotope curve which is presented in this study the composite 13c signal recorded in the depth domain was analyzed by combined lomb scargle periodogram and weighted wavelet z transform wwz weighted wavelet amplitudes wwa foster wavelet spectral methodologies both appropriate for unevenly sampled curves these tools allowed us to unravel the main frequencies modulating the record and their hypothetical shift in depth respectively the long term 400 000 and 2 400 000 years eccentricity cycles were consistently recorded throughout all the composite record once band pass filtered in these two periodicity bands and compared to the lithologic pattern cycles identified throughout the composite sequence the 13c signal was used as a valuable proxy record for a reliable construction of an orbital tuning of the early cretaceous an estimated age for all the different stratigraphic events recognized throughout the composite record was reported in particular the reestimated ages of the paleomagnetic chrons documented in the upper part of the record show differences with those reported by gradstein et al 2004 up to 2 m y the valanginian carbon shift present in the middle part of the composite sequence was estimated to be 2 3 m y long the good agreement between the estimated age of the base of this positive carbon isotope excursion 136 34 m y and the predominant volcanic phase associated to the parana etendeka large igneous province intrusion confirmed a possible cause effect link between the two events

glacial rapid variability in deep water temperature and δ18o from the western mediterranean sea abstract deep water temperatures dwts from the western mediterranean sea are reconstructed for the last 50 ka based on the analysis of mg ca ratios in benthic foraminifera from core md95 2043 collected in the alboran sea the exceptionally high sedimentation rates of this core and the robust chronology available allow discussion of the results in the context of the dansgaard oeschger d o rapid climatic variability the applicability of mg ca thermometry in the western mediterranean deep water mass wmdw is first tested by the analysis of different benthic species in a collection of mediterranean core tops the results indicate the need of a readjustment of the existing cibicidoides spp calibrations in order to reconstruct present western mediterranean dwt values 12 7 c different physiological effects in the mg uptake between the c pachydermus living in different regions could account for this offset in the mediterranean samples consequently the obtained dwt record still has many uncertainties in absolute terms but trends provide valuable information on past changes in wmdw conditions the dwt record shows significant oscillations in relation to the d o cycles colder values occurred during the time of d o stadials and warmer ones during d o interstadials surprisingly the coldest dwts occurred during the time of heinrich event 4 he4 and not during the last glacial maximum lgm when dwts were mostly warm these and other particular features of the dwt reconstruction mimic changes in the vegetation from the eastern mediterranean indicating the control of the mediterranean climate on the dwt record paired analyses of mg ca and 18 occ calcite 18 o provide the opportunity to reconstruct deep water 18 o 18 odw and past salinities and hence changes in past wmdw density due to the large error associated with these calculations they can only be discussed in terms of relative changes between different intervals the results suggest the dominance of a heavier water end member during glacial times and a lighter one during the early holocene in relation to the 18 odw conditions present today densest wmdw were formed during most of marine isotopic stage mis 2 and during the d o stadials not associated with hes while lightest wmdw dominated during d o interstadials the 18 odw record shows a d o variability pattern likely controlled by changes in the composition and intensity of the local run off and also to changes in the 18 ow signal of the atlantic inflow changes in the residence time of the mediterranean waters governed by the global sea level are also considered to exert an important role governing mediterranean 18 ow and salinity particularly during mis 2 overall our results are consistent with the formation of dense wmdw during d o stadials and even denser during most of mis 2

manganese carbonate overgrowths on foraminifera tests below the zone where manganese is remobilized as mn2 aq reductively cleaned foraminifera in deep sea sediments have much higher mnca than those in core tops and sediment traps mnca ranges from less than 20 10 6 in and above the mno2 maximum to as high as 700 10 6 in reducing panama basin sediments the most plausible explanation for this enrichment is that the tests are coated with mn carbonate overgrowths these coatings can account for a significant proportion of the mn in reduced deep sea sediments uptake of manganous ion by carbonate may explain the absence of mn nodules in areas of high carbonate accumulation extreme degrees of overgrowth can alter foram trace element values but this artifact can be avoided by avoiding foraminifera with high mn ca

regional trends in clay mineral fluxes to the queensland margin and ties to middle miocene global cooling abstract three odp sites located on the marion plateau northeast australian margin were investigated for clay mineral and bulk mineralogy changes through the early to middle miocene kaolinite to smectite k s ratios as well as mass accumulation rates of clays point to a marked decrease in accumulation of smectite associated with an increase in accumulation of kaolinite starting at 15 6 ma followed by a second increase in accumulation of kaolinite at 13 2 ma both of these increases are correlative to an increase in the calcite to detritus ratio comparison of our record with published precipitation proxies from continental queensland indicates that increases in kaolinite did not correspond to more intense tropical humid conditions but instead to periods of greater aridity three mechanisms are explored to explain the temporal trends in clay on the marion plateau sea level changes changes in oceanic currents and denudation of the australian continent followed by reworking and eolian transport of clays though low mass accumulation rates of kaolinite are compatible with a possible contribution of eolian material after 14 ma when australia became more arid the lateral distribution of kaolinite along slope indicates mainly fluvial input for all clays and thus rules out this mechanism as well as oceanic current transport as the main controls behind clay accumulation on the plateau we propose a model explaining the good correlation between long term sea level fall decrease in smectite accumulation increase in kaolinite accumulation and increase in carbonate input to the distal slope locations we hypothesize that during low sea level and thus periods of drier continental climate in queensland early miocene kaolinite rich lacustrine deposits were being reworked and that the progradation of the heterozoan carbonate platforms towards the basin center favored input of carbonate to the distal slope sites the major find of our study is that increase kaolinite fluxes on the queensland margin during the early and middle miocene did not reflect the establishment of a tropical climate and this stresses that care must be taken when reconstructing australian climate based on deep sea clay records alone

the geochemistry of manganese carbonate in panama basin sediments abstract the mn distribution in panama basin area sediments and interstitial waters is discussed striking surficial mn enrichments produced by a well known diagenetic recycling process characterize the sediments of the region thermodynamic solubility calculations indicate that in at least one core interstitial waters approach saturation with respect to mnco3 a mixed carbonate phase of composition mn48 ca47 mg5 co3 was recovered from an ash band in the same core the association of this material with the coarse volcaniclastic debris is thought to result from facile manganous carbonate precipitation in sediment horizons of coarser mean grain size since sulphate reduction in the upper two metres of panama basin sediments is fairly minor little increase in alkalinity is observed and it is postulated that significant production of carbonate alkalinity is not a prerequisite for manganous carbonate generation in hemipelagic sediments a more important factor appears to be the availability of mn oxides for solution during early diagenesis stable c isotopic analyses indicate that little c of organic origin is used in the precipitation reaction in either panama basin or loch fyne scotland sediments

uranium in foraminiferal calcite as a recorder of seawater uranium concentrations abstract we present results of an investigation of uranium calcium ratios in cleaned foraminiferal calcite as a recorder of seawater uranium concentrations for accurate reconstruction of past seawater uranium content shell calcite must incorporate uranium in proportion to seawater concentration and must preserve its original uranium composition over time laboratory culture experiments with live benthic amphistegina lobifera and live planktonic globigerinella calida foraminifera show that the u ca ratio of cleaned calcite tests is proportional to the concentration of uranium in solution after correcting results for the presence of initial calcite the apparent distribution coefficient d u ca calcite u ca solution 10 6 0 3 10 3 for a lobifera and d 7 9 0 1 10 3 for g calida u ca ratios in planktonic foraminifera from core tops collected above 3900 m in the equatorial atlantic and above 2100 m in the pacific ocean show no significant difference among the species analyzed d estimated from core top samples ranges from 7 6 0 4 10 3 for o universa to 8 4 0 5 10 3 for g ruber in benthic species c wuellerstorfi d 7 0 0 8 10 3 u ca and mg ca in g tumida and g sacculifer from core tops taken near and below the regional lysocline decrease with water depth smaller decreases in u ca and mg ca with depth were observed in c wuellerstorfi in the planktonic species we believe that u ca and mg ca are lower in the more dissolution resistant fraction of calcite leading to lower u ca in more highly dissolved samples

effects of oceanic circulation and volcanic ash fall on calcite dissolution in bathyal sediments from the sw pacific ocean over the last 550 ka abstract the effects on calcite dissolution of both oceanic circulation and volcanic ash fall were evaluated in lower bathyal sediments over the last 550 ka record from core md 97 2114 recovered on the northern slope depth of 1936 m in the pacific deep water pdw of the chatham rise east of new zealand sw pacific ocean this area has been impacted by changes in glacial interglacial circulation and ocean chemistry as well as by the explosive volcanic activity of the taupo volcanic zone several micro paleontological dissolution proxies based on planktonic foraminifera and calcareous nannofossils were analysed in order to evaluate the calcite dissolution of the deep sea sediments these were compared with a couple of proxies of primary productivity benthic foraminiferal epifaunal infaunal ratio and 13cbenthic foraminifera and the abundance of volcanic glass the dissolution proxy data from md 97 2114 were compared with two nearby odp sites odp 1123 3290 m deep bathed by the lower circumpolar deep water lcdw and odp 1125 1365 m deep bathed by the antarctic intermediate water aaiw the results suggest 1 the calcite dissolution preservation cycles at all three core sites show glacial interglacial g i periodicities that match the previously described pacific style caco3 cycles 2 several short term dissolution events do not follow this general scheme and occur following tephra deposition the dissolution related to the tephra deposition seems to have mostly affected calcareous nannofossils thus we hypothesise that the ash fall induced a temporary reduction of the surface water ph below 7 8 which affected the coccolithophores that inhabit the surface waters 3 other short term dissolution events 1000 years are unrelated to tephra deposition and are possibly driven by the slowing of deep sea circulation and a reduced deep western boundary current dwbc this lead to the dominance of older more corrosive pacific deep water pdw flowing in to the region resulting in coeval dissolution episodes at all three core sites depth range from 1365 to 3290 m

identification and removal of mn mg rich contaminant phases on foraminiferal tests implications for mg ca past temperature reconstructions 1 the geochemical composition of foraminifera shells from an ocean drilling program site in the panama basin has been analyzed by several analytical techniques la icp ms icp ms xrd sem edx in order to identify and evaluate the occurrence of contaminant phases which may bias paleoenvironmental reconstructions la icp ms results on uncleaned tests indicate the presence of mnmg rich contaminant phases at the inner surfaces of the foraminiferal shells which have mn ca ratios up to 400 mmol mol 1 and mg ca ratios up to 50 mmol mol 1 we have rigorously assessed the ability of different cleaning protocols to remove these contaminant phases and have obtained satisfactory results only when a reductive step is included the analysis of cleaning residuals collected after each of the different cleaning steps applied reveals that high mn values are associated with at least two different contaminant phases of which only one is linked to high mg values xrd analysis further reveals that the mn mg rich phase is the ca mn mg carbonate kutnahorite ca mn mg co3 2 our results demonstrate that the presence of kutnahorite like minerals can bias mg ca ratios toward higher values by 7 36 and lead to significant overestimation of past seawater temperatures by 0 9 up to 6 2 c in the case of these panama basin samples components 11 867 words 13 figures 3 tables

interactions between environmental change and shallow water carbonate buildup along the northern tethyan margin and their impact on the early cretaceous carbon isotope record 1 the evolution of the early cretaceous northern tethyan carbonate platform was not only influenced by changes in sea level detrital influx and surface water temperature but also by changes in trophic levels we distinguish between phases of carbonate production dominated by oligotrophic photozoan communities and by mesotrophic and eventually colder water heterozoan communities superimposed on this bimodal trend in platform evolution were phases of platform demise for which we provide improved age control based on ammonite biostratigraphy the initial phase of these episodes of platform demise corresponds in time to episodes of oceanic anoxic events and environmental change in general on the basis of a comparison between the temporal changes in an early cretaceous ammonite calibrated d 13 c record from southeastern france and coeval changes in the platform record we suggest that the history of carbon fractionation along the northern tethyan margin was not only influenced by changes in the oceanic carbon cycle such as in the rate of production and preservation of organic and carbonate carbon and in the size of the oceanic dissolved inorganic carbon reservoir but it was also influenced by the above mentioned changes in the ecology and geometry of the adjacent carbonate platform phases of photozoan carbonate production induced positive trends in the hemipelagic carbonate d 13 c record phases of heterozoan carbonate production pushed the d 13 c system toward more negative values platform drowning episodes implied an initial increase in d 13 c values followed by a longerterm decrease in d 13 c values

thermal evolution of cretaceous tethyan marine waters inferred from oxygen isotope composition of fish tooth enamels 1 the evolution of subtropical 30 35 n upper ocean temperatures through the cretaceous is inferred from the oxygen isotope compositions of 64 fish teeth enamel coming from the western tethyan platform mean 18o values of 22 at the berriasian valanginian boundary decrease with oscillations to 18 5 around the cenomanian turonian boundary and progressively increase to 21 5 by the end of the cretaceous the similarity of this oxygen isotope curve for bioapatites from platform environments with those for foraminifera and bulk carbonates that were deposited in deeper waters and at other paleolatitudes indicates that they record global climatic signals major cooling events at the million year scale can be distinguished 1 at the berriasian valanginian boundary and 2 during the earliest late valanginian a third cooling event is detected during the earliest aptian these events already proposed as icehouse interludes during the lower cretaceous are also recorded at subtropical latitudes a progressive warming is identified from the aptian to the cenomanian turonian interval that corresponds to a thermal optimum and then upper ocean temperatures decreased to the maastrichtian minimum isotopic temperatures range from 15 c to 28 c assuming a 18oseawater of 1 for an ice free world taking more realistic 18oseawater values of 0 for tropical waters during glacial periods within the berriasian valanginian interval and earliest aptian or with above average salinities possibly the maastrichtian temperatures are increased by 4 5 c temperature differences between climatic extremes of the valanginian and cenomanian turonian are estimated to have been 10 c latitudinal thermal gradients for the albian cenomanian turonian and maastrichtian were 0 2 0 3 c latitude and thus weaker than modern oceanic values at about 0 4 c latitude

silicate weathering and carbon cycle controls on the oligocene miocene transition glaciation changes in both silicate weathering rates and organic carbon burial have been proposed as drivers of the transient mi 1 glaciation event at the oligocene miocene transition omt 23 ma however detailed geochemical proxy data are required to test these hypotheses here we present records of li ca mg ca cd ca u ca 18o 13c and shell weight in planktonic foraminifera from marine sediments spanning the omt in the equatorial atlantic ocean li ca values increase by 1 mol mol across this interval we interpret this to indicate a 20 increase in silicate weathering rates which would have lowered atmospheric co2 potentially forcing the antarctic glaciation circa 23 ma 13c of thermocline dwelling planktonic foraminifera track the global increase in seawater 13c across the omt and during the mi 1 event hence supporting a hypothesized global increase in organic carbon burial rates high 13c previously measured in epipelagic planktonic foraminifera and high cd ca ratios during mi 1 are interpreted to represent locally enhanced primary productivity stimulated by increased nutrients supply to surface waters the fingerprint of high export production and associated organic carbon burial at this site is found in reduced bottom water oxygenation inferred from high foraminiferal u ca and enhanced respiratory dissolution of carbonates characterised by reduced foraminiferal shell weight replication of our results elsewhere would strengthen the case that weathering induced co2 sequestration preconditioned climate for antarctic ice sheet growth across the omt and increased burial of organic carbon acted as a feedback that intensified cooling at this time

interlaboratory comparison study of calibration standards for foraminiferal mg ca thermometry an interlaboratory study of mg ca and sr ca ratios in three commercially available carbonate reference materials bam rs3 cmsi 1767 and ecrm 752 1 was performed with the participation of 25 laboratories that determine foraminiferal mg ca ratios worldwide these reference materials containing mg ca in the range of foraminiferal calcite 0 8 mmol mol to 6 mmol mol were circulated with a dissolution protocol for analysis participants were asked to make replicate dissolutions of the powdered samples and to analyze them using the instruments and calibration standards routinely used in their laboratories statistical analysis was performed in accordance with the international standardization organization standard 5725 which is based on the analysis of variance anova technique repeatability rsdr an indicator of intralaboratory precision for mg ca determinations in solutions after centrifuging increased with decreasing mg ca ranging from 0 78 at mg ca 5 56 mmol mol to 1 15 at mg ca 0 79 mmol mol reproducibility rsdr an indicator of the interlaboratory method precision for mg ca determinations in centrifuged solutions was noticeably worse than repeatability ranging from 4 5 at mg ca 5 56 mmol mol to 8 7 at mg ca 0 79 mmol mol results of this study show that interlaboratory variability is dominated by inconsistencies among instrument calibrations and highlight the need to improve interlaboratory compatibility additionally the study confirmed the suitability of these solid standards as reference materials for foraminiferal mg ca and sr ca determinations provided that appropriate procedures are adopted to minimize and to monitor possible contamination from silicate mineral phases

synchroneity of tropical and high latitude atlantic temperatures over the last glacial termination a high resolution western tropical atlantic sea surface temperature sst record from the cariaco basin on the northern venezuelan shelf based on mg ca values in surface dwelling planktonic foraminifera reveals that changes in sst over the last glacial termination are synchronous within 30 to 90 years with the greenland ice sheet project 2 air temperature proxy record and atmospheric methane record the most prominent deglacial event in the cariaco record occurred during the younger dryas time interval when ssts dropped by 3 to 4 c a rapid southward shift in the atmospheric intertropical convergence zone could account for the synchroneity of tropical temperature atmospheric methane and high latitude changes during the younger dryas