cosmogenic 3he production rates from 39 n to 46 n latitude western usa and france the in situ production rate of cosmogenic 3he was determined in seven different olivine or pyroxene bearing rocks between the latitudes 39 n and 46 n the integrated production rate over the last 17 500 years is about 115 4 atoms gram yr for high latitude at sea level the variation in the integrated production rate between 2000 and 18 000 years is less than 30 and is probably on the order of 20 or less

planktonic foraminiferal depth habitat and δ18o calibrations plankton tow results from the atlantic sector of the southern ocean varies by several orders of magnitude across a large gradient in sea surface temperature and other hydrographic features demonstrating high sensitivity of foraminiferal populations to regional differences in water properties the depth of maximum abundance for key species such as globigerina bulloides and neogloboquadrina pachyderma is not constant from station to station the pattern suggests that their abundance and shell chemistry are tied to density horizons or other conditions such as food availability that become more sharply defined with depth in the northern subantarctic the consistent observation of globorotalia inflata and globoratalia truncatulinoides as relatively deep dwelling species confirms their utility as indicators of upper thermocline properties in d 18 o all species are observed to be isotopically lighter than predicted from water properties but the species specific offset is fairly uniform at all stations these observations define the utility of multispecies d 18 o for reconstructing temperature and density stratification from past surface oceans index terms 4267 oceanography general paleoceanography 4572 oceanography physical upper ocean processes 4870 oceanography biological and chemical stable isotopes 3030 marine geology and geophysics micropaleontology keywords stratification d 18 o

an evaluation of lohmann s foraminifera weight dissolution index down water column traverses of core top weights for three planktonic species confirm lohmann s 1995 relationship between foraminifera shell weight loss and bottom water carbonate ion content however they also suggest that the initial shell thickness varies with growth habitat and that the offset between bottom water and pore water carbonate ion concentration varies even on small space scales

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

the 21ne production rate in quartz revisited abstract i have revised our earlier production rate determination of 21ne in terrestrial quartz s niedermann th graf j s kim c p kohl k marti and k nishiizumi 1994 earth planet sci lett 125 341 355 taking account of improved knowledge about the exposure age of samples used in that work and applying distinct procedures for scaling to sea level and high latitudes the corrected value of 19 0 3 7 atoms g 1 a 1 is in excellent agreement with expectations based on nuclear properties j masarik and r c reedy 1995 earth planet sci lett 136 381 395 and closely corresponds to the present day production rate in the case of substantial variations of the geomagnetic field in the past as proposed by several studies the revised value can consistently be used with suitable correction methods

reconstructing past planktic foraminiferal habitats using stable isotope data a case history for mediterranean sapropel s5 abstract a high resolution stable o and c isotope study is undertaken on all planktic foraminiferal species that are reasonably continuous through an eemian sapropel s5 from the western side of the eastern mediterranean the data are considered within a context of high resolution isotope records for two further s5 sapropels from the central and easternmost sectors of the basin alkenone based sea surface temperature records for all three sapropels and planktic foraminiferal abundance records for the same sample sets through all three sapropels results are compared with similar data for holocene sapropel s1 the adopted approach allows distinction between species that are most suitable to assess overall changes in the climatic hydrographic state of the basin including depth related differentiations and the main seasonal developments and species that are most affected by variable biological controls or local regional and transient physico chemical forcings it is found that a priori assumptions about certain species palaeohabitats based on modern habitat observations may become biased when non analogue conditions develop in the case of mediterranean sapropel s5 these consisted of enhanced freshwater dilution elevated productivity shoaling of the pycnocline between intermediate and surface waters and stagnation of the subsurface circulation under these conditions some species are found to shift into habitat settings that differ considerably from those occupied today the present multiple species approach can identify such anomalous responses and thus offers a sound background for further shell chemistry investigations and quantitative interpretation of the isotopic profiles we capitalise on the latter potential and offer the first quantitative estimates of monsoon flooding into the mediterranean during the deposition of eemian sapropel s5

dating of sirius group tillites in the antarctic dry valleys with cosmogenic3he and21ne we measured in situ produced cosmogenic3he and21ne in boulder and bedrock surface samples in and near sirius group tillites from two localities in southern victoria land antarctica pyroxene quantitatively retains cosmogenic3he for millions of years the deposit at mt fleming has a minimum exposure age of 6 5 ma while 6 ma is a probable minimum age for the table mountain tillite these lower limits not taking into account erosion of the sampled surfaces are based on the samples with the highest concentrations of cosmogenic noble gases and currently accepted production rates since the plagioclase bearing mt fleming samples almost certainly lost part of their cosmogenic ne the minimum exposure age at this location is presumably even 50 higher than the stated value the concentrations of cosmogenic ne in our samples constrain uplift rates of the transantarctic mountains to 170 m ma these data contradict the hypothesis of a collapse of the east antarctic ice sheet in the pliocene coupled with high uplift rates and support the model of a stable ice sheet since the middle miocene

unmixing of stable isotope signals using single specimen δ18o analyses 1 the resolution at which foraminiferal stable isotopes are applied in paleo environmental studies is ever increasing resulting in continuous sampling of sediment cores the resolution of such continuously sampled records depends on the rate of sedimentation of foraminiferal shells in its relation to the intensity of bioturbation bioturbation essentially mixes sediment layers of different age altering the primary climate signal thereby impacting the accuracy of both the timing and magnitude of reconstructed climate changes a new approach to assess and correct the impact of bioturbation is investigated here based on the 18o of individual specimens of planktonic foraminifera globorotalia inflata from a series of boxcore samples in the eastern north atlantic average 18o values decrease southward from 1 62 to 1 07 with the exception of site t86 11 1 35 the 18o distribution of each station can be fitted with a uni to polymodal distribution a nonunimodal distribution strongly suggests admixing of bioturbated individuals quantification of these distributions allows deconvolving the original and bioturbated signals and subsequently provides a correction for bioturbation

planktonic foraminiferal area density as a proxy for carbonate ion concentration a calibration study using the cariaco basin ocean time series 1 biweekly sediment trap samples and concurrent hydrographic measurements collected between march 2005 and october 2008 from the cariaco basin venezuela are used to assess the relationship between co32 and the area densities a of two species of planktonic foraminifera globigerinoides ruber pink and globigerinoides sacculifer calcification temperatures were calculated for each sample using species appropriate oxygen isotope 18o temperature equations that were then compared to monthly temperature profiles taken at the study site in order to determine calcification depth ambient co32 was determined for these calcification depths using alkalinity ph temperature salinity and nutrient concentration measurements taken during monthly hydrographic cruises the a which is representative of calcification efficiency is determined by dividing individual foraminiferal shell weights 0 43 g by their associated silhouette areas and taking the sample average the results of this study show a strong correlation between a and ambient co32 for both g ruber and g sacculifer r2 0 89 and 0 86 respectively confirming that co32 has a pronounced effect on the calcification of these species though the a for both species reveal a highly significant p 0 001 relationship with ambient co32 linear regression reveals that the extent to which co32 influences foraminiferal calcification is species specific hierarchical regression analyses indicate that other environmental parameters temperature and po43 do not confound the use of g ruber and g sacculifer a as a predictor for co32 this study suggests that g ruber and g sacculifer a can be used as reliable proxies for past surface ocean co32

planktic foraminiferal sedimentation and the marine calcite budget 1 the vertical flux and sedimentation rate of planktic foraminiferal tests are quantified and a global planktic foraminiferal cac0 3 budget is presented test and calcite flux rates are calculated according to the distribution of species obtained from multinet and sediment trap samples modern planktic foraminiferal population dynamics are discussed as a prerequisite for the quantification of the calcite budget highlighting the importance of ecological autecological e g reproduction and biogeochemical conditions that determine the presence or absence of species to complete the open marine particulate caco 3 inventory the contribution of coccolithophores pteropods and calcareous dinophytes is discussed based on the studied regions the global planktic foraminiferal calcite flux rate at 100 m depth amounts to 1 3 3 2 gt yr 1 equivalent to 23 56 of the total open marine caco 3 flux the preservation of tests varies on a regional and temporal scale and is affected by local hydrography and dissolution during most of the year off peak periods many tests dissolve above 700 m water depth while settling through the water column with on average only 1 3 of the initially exported caco 3 reaching the deep seafloor pulsed flux events mass dumps of fast settling particles yield a major contribution of tests to the formation of deep sea sediments on average 25 of the initially produced planktic foraminiferal test cac0 3 settles on the seafloor the total planktic foraminiferal contribution of caco 3 to global surface sediments amounts to 0 36 0 88 gt yr 1 32 80 of the total deep marine calcite budget

palaeoceanographic and environmental changes in the eastern fram strait during the last 14 000 years based on benthic and planktonic foraminifera abstract benthic and planktonic foraminifera stable isotopes and other geochemical and sedimentological parameters have been investigated in a sediment core from vestnesa ridge 79 n nw svalbard margin 1300 m water depth in order to reconstruct the palaeoceanographic and palaeoenvironmental evolution of the eastern fram strait during the last 14 000 years our multiproxy data and in particular our high resolution benthic foraminiferal record allow a detailed reconstruction of the intermediate water flow in the eastern fram strait during the bolling allerod warm interstadials the high proportion of the benthic atlantic species cassidulina neoteretis suggests the presence of chilled atlantic derived water at the bottom of the vestnesa ridge while the dominance of the polar planktonic species neogloboquadrina pachyderma s indicates cold polar surface conditions during the younger dryas cold stadial the inflow of atlantic derived water was weakened and of lower temperature compared to the previous interval as suggested by the increase in the glacio marine indicator cassidulina reniforme and the lower percentages of c neoteretis after 11 000 cal yr bp the abrupt increase in relative abundance of the benthic species cibicides wuellerstorfi and oridorsalis umbonatus indicates a shift to interglacial conditions with deep convection and generation of cold intermediate water warm surface water conditions were finally established at about 10 300 cal yr bp when turborotalita quinqueloba became the dominant planktonic species generally warmer conditions than today were recorded in the middle holocene with a mild cooling at about 8200 cal yr bp and a more pronounced cool interval with an abrupt decrease in t quinqueloba between 7000 and 6200 cal yr bp cold climatic conditions were established around 4100 cal yr bp when n pachyderma s became again the dominant species and the polar benthic species cribroelphidium excavatum appeared

stable oxygen isotope composition is biased by shell calcification intensity in planktonic foraminifera planktonic foraminifera are widely used for environmental reconstructions through measurements of their shell s geochemical characteristics including its stable oxygen and carbon isotope composition using these parameters as unbiased proxies requires a firm knowledge of all potential confounding factors influencing foraminiferal shell geochemistry one such parameter is the shell calcification intensity shell weight normalized for shell size that may influence the shell delta 18o value either bioenergetically by reducing energy available and required for equilibrium isotope fractionation during faster calcification or kinetically by influencing calcification depth through the shell s density contrast with seawater specimens from the globigerinoides ruber elongatus compound from a sediment trap in the north atlantic have been used to quantify the influence of shell calcification intensity on shell delta 18o values shell calcification intensity was found to have a significant effect on the shell stable oxygen isotope composition in all species through model fitting it is suggested that the effect size may be in a range of 1 to 2 depending on species depth migration and local oceanographic conditions we show that the confounding effect of shell calcification intensity on stable oxygen isotope composition can be of importance depending on the anticipated precision of the derived reconstructions a framework is provided to quantify this effect in future studies

mg ca ratios of two globigerinoides ruber white morphotypes implications for reconstructing past tropical subtropical surface water conditions 1 tests of the planktonic foraminifer globigerinoides ruber white d orbigny have become a standard tool for reconstructing past oceanic environments paleoceanographers often utilize the mg ca ratios of the foraminiferal tests for reconstructing low latitude ocean glacial interglacial changes in sea surface temperatures sst we report herein a comparison of mg ca measurements on sample pairs n 20 of two g ruber white morphotypes g ruber sensu stricto s s and g ruber sensu lato s l from surface and downcore samples of the western pacific and indian oceans g ruber s s refers to specimens with spherical chambers sitting symmetrically over previous sutures with a wide high arched aperture whereas g ruber s l refers to a more compact test with a diminutive final chamber and small aperture the g ruber s s specimens generally show significantly higher mg ca ratios compared to g ruber s l our results from the mg ca ratio analysis suggest that g ruber s l specimens precipitated their shells in slightly colder surface waters than g ruber s s specimens this conclusion is supported by the differences in 18o and 13c values between the two morphotypes although it is still unclear if these two morphotypes represent phenotypic variants or sibling species our findings seem to support the hypothesis of depth and or seasonal allopatry within a single morphospecies

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

biomineralization in perforate foraminifera in this paper we review the current understanding of biomineralization in perforate foraminifera ideas on the mechanisms responsible for the flux of ca2 and inorganic carbon from seawater into the test were originally based on light and electron microscopic observations of calcifying foraminifera from the 1980s onward tracer experiments fluorescent microscopy and high resolution test geochemical analysis have added to existing calcification models despite recent insights no general consensus on the physiological basis of foraminiferal biomineralization exists current models include seawater vacuolization transmembrane ion transport involvement of organic matrices and or ph regulation although the magnitude of these controls remain to be quantified disagreement between currently available models may be caused by the use of different foraminiferal species as subject for biomineralization experiments and or lack of a more systematic approach to study dis similarities between taxa in order to understand foraminiferal controls on element incorporation and isotope fractionation and thereby improve the value of foraminifera as paleoceanographic proxies it is necessary to identify key processes in foraminiferal biomineralization and formulate hypotheses regarding the involved physiological pathways to provide directions for future research

three hundred eighty thousand year long stable isotope and faunal records from the red sea influence of global sea level change on hydrography stable isotope and faunal records from the central red sea show high amplitude oscillations for the past 380 000 years positive 18o anomalies indicate periods of significant salt buildup during periods of lowered sea level when water mass exchange with the arabian sea was reduced due to a reduced geometry of the bab el mandeb strait salinities as high as 53 and 55 are inferred from pteropod and benthic foraminifera 18o respectively for the last glacial maximum during this period all planktonic foraminifera vanished from this part of the red sea environmental conditions improved rapidly after 13 ka as salinities decreased due to rising sea level the foraminiferal fauna started to reappear and was fully reestablished between 9 ka and 8 ka spectral analysis of the planktonic 18o record documents highest variance in the orbital eccentricity obliquity and precession bands indicating a dominant influence of climatically driven sea level change on environmental conditions in the red sea variance in the precession band is enhanced compared to the global mean marine climate record specmap suggesting an additional influence of the indian monsoon system on red sea climates

alpha thermochronology of carbonates abstract step heating experiments on 17 calcites from 11 different samples and 6 dolomites from 5 samples suggest a closure temperature of he in carbonates 70 10 c for a cooling rate of 10 c m y the bulk closure temperature in some samples may tend slightly higher due to the presence of diffusion domains larger and therefore more retentive than the sites in which the majority of he resides the diffusivity of he in calcite is independent of the genesis of the mineral igneous sedimentary metamorphic or the source of the he radiogenic common or laboratory induced and in all samples analyzed the effective diffusion dimension for he is smaller than the size of the crystals investigated although calcite is a low u mineral this shortcoming can be overcome by analyzing large samples 2 mm diameter provided samples have a minimum of 0 3 ppm u samples with smaller concentrations of alpha producers are unlikely to produce enough radiogenic 4he sufficient to overwhelm he present in the crystals at the time they passed through their closure temperature

benthic foraminiferal shell weight deglacial species specific responses from the santa barbara basin abstract here we present a record of size normalized shell weight for four species of benthic foraminifera through a period of rapid environmental change during the most recent deglaciation santa barbara basin ca a strong oxygen minimum zone omz the product of high surface productivity and poor ventilation characterizes the eastern pacific this subsurface zone is mechanistically coupled with high concentrations of dissolved inorganic carbon the omz migrated vertically during warming of the last deglaciation leading to rapid shifts in the oxygenation and inorganic carbon system of the benthos the size normalized weight snw of benthic foraminifers uvigerina peregrina bolivina interjuncta and bolivina tumida reflects only the broad trends of the vertical migration of the omz and inorganic carbon system overshadowed by clear species specific trends the relative importance of omz migrations versus other environmental variables and optimal growth conditions differs across species of benthic foraminifera in u peregrina snw primarily peaks with foraminiferal density and increased abundance of that species while b interjuncta and b tumida increase in snw with a shrinking of the omz and carbon maximum in the late holocene bolivina argentea shows no long term trends in snw potentially due to its ability to migrate through the sediment our results suggest that while inorganic carbon and dissolved oxygen may play a role in determining shell weight across species of benthic foraminifera neither parameter alone is responsible for changes in benthic foraminiferal shell weight in the fossil record

an intensity ratio calibration method for the accurate determination of mg ca and sr ca of marine carbonates by icp aes an inductively coupled plasma atomic emission spectroscopy icp aes method for the accurate and precise simultaneous measurement of the mg ca and sr ca content of carbonates was established while a precision of 0 3 1 standard deviation sd is easily obtainable for both mg ca and sr ca analysis a ca matrix effect complicates achieving similar levels of accuracy with conventional calibration procedures an alternative ratio calibration procedure is proposed which overcomes the ca matrix effects and ensures the accuracy of the mg ca and sr ca analysis of marine carbonates to 0 3 almost an order of magnitude better than conventional calibration methods the longer term precision is 0 1 if the batch run average values are corrected for longer term drift the method is suitable for analysis of foraminiferal calcite and coral aragonite and can easily be adjusted for the analysis of other carbonates or microsamples

impacts of ph and co32 on the incorporation of zn in foraminiferal calcite the trace elemental composition of foraminiferal shell calcite is known to reflect the environment in which the shell was precipitated whereas conservative elements incorporated in foraminiferal shell carbonate reflect factors such as temperature mg carbonate chemistry b and salinity na the nutrient type elements ba cd and possibly zn are useful tools to reconstruct biogeochemical cycling and past ocean circulation still also nutrient type elements will be most likely influenced by factors other than their relative concentrations culturing benthic foraminifera under controlled carbonate chemistry conditions allows for disentanglement of impacts of different parameters of the carbon system on the elemental composition of foraminiferal calcite here we show that zinc incorporation in cultured specimens of the benthic foraminifer ammonia tepida is correlated to changes in carbonate ion concentration co32 by modeling activities of different chemical species of zn in seawater over a range of co32 we suggest that zn2 rather than other relatively abundant zn species e g znco30 and znhco3 is taken up during biomineralization our results suggest that foraminiferal zn ca might be especially useful when combined with other co32 proxies enabling reconstruction of past seawater element concentrations conversely when the nutrient type element concentrations are known incorporation of zn in foraminiferal shells can be used to reconstruct past sea water carbon speciation

micron scale intrashell oxygen isotope variation in cultured planktic foraminifers abstract in this study we show that the rate of shell precipitation in the extant planktic foraminifer orbulina universa is sufficiently rapid that 12 h calcification periods in 18 o labeled seawater can be resolved and accurately measured using secondary ion mass spectrometry sims for in situ 18 o analyses calcifying o universa held at constant temperature 22 c were transferred every 12 h between ambient seawater 18 o w 0 4 vsmow and seawater with enriched barium and 18 o w 18 6 vsmow to produce geochemically distinct layers of calcite separated by calcite precipitated with an ambient geochemical signature we quantify the position of the ba labeled calcite in the shell wall of o universa via laser ablation icp ms depth profiling of trace element ratios and then measure intrashell 18 o calcite in the same shells using sims with a 3 m spot and an average precision of 0 6 2 sd measured 18 o calcite values in o universa shell layers are within 1 1 of predicted 18 o calcite values elemental and oxygen isotope data show that la icp ms and sims measurements can be cross correlated within the spatial resolution of the two analytical techniques and that 18 o calcite and elemental tracers appear to be precipitated synchronously with no measurable spatial offsets these results demonstrate the capability of sims to resolve daily growth increments in foraminifer shells and highlight its potential for paleoceanographic and biomineralization applications on microfossils

a new boron isotope ph calibration for orbulina universa with implications for understanding and accounting for vital effects boron isotope ratios as measured in planktic foraminifera can be a useful tracer of past ocean ph and hence help to discern the concentration of co2 in the ancient atmosphere however different species of planktic foraminifera demonstrate different patterns of boron isotope variation with ambient seawater ph therefore when applying the proxy to questions in the geological past species specific calibrations are preferable beyond the evolutionary history of a calibrated species we must rely on our understanding of the causes of the observed vital effects in the modern ocean and the applicability of that understanding to extinct species here we present a new open ocean calibration of the planktic foraminifera orbulina universa measured via multi collector inductively coupled mass spectrometry mc icpms unlike other symbiont bearing foraminifera o universa record a 11b 11b and hence ph that is lower than its surrounding seawater but with a ph sensitivity roughly equal to that of aqueous borate ion we discuss the significance of this for application of the boron isotope proxy in deep time with recommendations for best practice and future research directions

cosmogenic 3he and 21ne production rates calibrated against 10be in minerals from the coso volcanic field this study calibrates the production rate of cosmogenic 3 he in pyroxene olivine garnet zircon and apatite as well as 21 ne in quartz and pyroxene against the known production rate of 10 be in quartz the devil s kitchen rhyolite from the coso volcanic field in southeastern california elev 1300 m was chosen for this study due to its young age 610 ka and diverse mineral assemblage based on 10 be our two rhyolite samples have apparent exposure ages of 49 and 93 ka indicating substantial erosion after eruption combining data from the two samples we estimate sea level high latitude 3 he spallation production rates of 145 11 141 16 and 144 30 at g 1 a 1 2 for pyroxene olivine and spessartine garnet respectively for zircon and apatite we estimate apparent 3he spallation production rates of 114 8 and 149 28 at g 1 a 1 2 respectively the rates for zircon and apatite are reported as apparent production rates because we do not explicitly address the redistribution of spallation produced 3 he from adjacent minerals these estimates quantitatively account for production of 3 he from both cosmogenic and radiogenic neutron reactions on 6 li within the analyzed phases and also implanted from nuclear reactions in neighboring minerals the high u th and li content of this rhyolite provides a particularly rigorous test of this correction we estimate 21 ne production rates of 17 7 1 6 and 34 1 3 2 at g 1 a 1 2 in quartz and pyroxene fe mg 0 7 by mass respectively although high u and th contents create the potential for significant production of nucleogenic 21 ne this component is small due to the young eruption age of the rhyolite

mg ca variation in planktonic foraminifera tests implications for reconstructing palaeo seawater temperature and habitat migration the nature of compositional variability within the tiny calcitic shells tests that are precipitated by planktonic foraminifera has been investigated using laser ablation inductively coupled plasma mass spectrometry la icp ms systematic large and correlated variation of mg ca mn ca ba ca and zn ca but relatively uniform sr ca are observed through the test walls of analysed species globigerinoides sacculifer globigerinoides ruber neogloboquadrina pachyderma and neogloboquadrina dutertrei distinct chamber and chamber wall layer compositions can be resolved within individual tests and mg ca compositional differences observed in sequentially precipitated test components of the different species analysed are consistent with seawater temperature changes occurring with habitat migration during their adult life cycle stages estimated test calcification temperatures are in keeping with available seawater temperature constraints indicating the potential for accurate seawater temperature reconstruction using la icp ms mg rich 1 6 mol mg surface veneers that are also enriched in mn ba and zn have been found on all species and all fossil tests as well as on live sampled tests of g ruber with the latter suggesting a possible biogenic origin these mg rich surfaces bias bulk test compositions toward higher mg ca values by between 5 and 35

habitats abundance patterns and isotopic signals of morphotypes of the planktonic foraminifer globigerinoides ruber d orbigny in the eastern mediterranean sea since the marine isotopic stage 12 article i nfo the chemical composition of shells of the planktonic foraminifer globigerinoides ruber white is frequently used to determine past sea surface conditions recently it has been shown that arbitrarily defined morphotypes within this species exhibit different chemical and isotopic signatures here we investigate the occurrence through time and in space of morphological types of g ruber white in late quaternary and holocene sediments of the central and the eastern mediterranean sea in 115 samples representing two distinct time intervals mis 1 2 and mis 9 12 at odp site 964 and the piston core geotu sl96 we have defined three morphological types within this species and determined their relative abundances and stable isotopic composition a quantitative analysis of morphological variation within g ruber white in four samples revealed that the subjectively defined morphotypes occupy separate segments of a continuous and homogenous morphospace we further show that the abundance of the morphotypes changes significantly between glacials and interglacials and that the three morphotypes of g ruber show significant offsets in their stable isotopic composition these offsets are consistent within glacial and interglacial stages but their sign is systematically reversed between the two sites since the isotopic shifts among the three g ruber morphotypes are systematic and often exceed 1 their understanding is essential for the interpretation of all g ruber based proxy records for the paleoceanographic development of the mediterranean during the late

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

assessing the effect of dissolution on planktonic foraminiferal mg ca ratios evidence from caribbean core tops in order to assess the dissolution effect on foraminiferal mg ca ratios we analyzed mg ca of seven planktonic foraminiferal species and four of their varieties from caribbean core tops from 900 4700 m water depth depending on the foraminiferal species and variety mg ca start to decline linearly below co32 levels of 18 26 mol kg by 0 04 0 11 mmol mol per 1 mol kg co32 similar to decreases of 0 5 0 8 mmol mol per kilometer below 2500 3000 m water depth above these species specific critical levels mg ca remains stable with higher intraspecific mg ca variability than below we developed routines to correct mg ca from below these critical thresholds for dissolution effects which reduce the overall intraspecific variability by 24 64 and provide dissolution corrected mg ca appropriate to calculate holocene paleotemperatures when taking into account only dissolution unaffected mg ca from 2000 m the systematic succession of foraminiferal species according to their mg ca reflects expected calcification depths

isotopic signals in two morphotypes of globigerinoides ruber white from the south china sea implications for monsoon climate change during the last glacial cycle abstract based on the study of surface and downcore sediment samples from the south china sea scs two morphotypes of globigerinoides ruber white have been differentiated by taxonomic criteria at species and or subspecies level and also by their stable isotopic compositions of oxygen and carbon the two morphotypes g ruber sensu stricto s s and g ruber sensu lato s l represent two groups with different depth habitats with g ruber s s living in the upper 30 m of the water column and g ruber s l living at depths below 30 m the different depth habitats are indicated by the comparison between the present oceanographic data and isotopic signals of the two morphotypes in the surface sediment from the scs application of this information to a hemipelagic sediment core in the northern scs shows that drastic changes existed in the morphotypes isotopic records during the last glacial cycle the isotope difference between the two morphotypes diminished during 18 o stage 2 especially during the last glacial maximum it is inferred that this is the result of intensified monsoon winds which caused mixing of the upper layer of the water column during stage 2 the proportion of g ruber s l increased which is interpreted as a result of the increased productivity due to mixing of the subsurface nutrient rich water into the surface layer

direct assessment of stable isotope variability in planktonic foraminifera populations abstract a large number of tests of three species of planktonic foraminifera globigerinoides sacculifer orbulina universa and pulleniatina obliquiloculata were analyzed for stable oxygen and carbon isotopes in a western equatorial pacific box core estimates of population variance were calculated using a statistical technique known as the jackknife these estimates were used to generate sampling curves which provide the number of foraminiferal tests required in an isotopic analysis when precision and reliability criteria are specified the jackknife results have important sampling implications 1 a large number of foraminiferal tests are required to obtain statistically reliable isotope data for example given a machine precision standard deviation of 0 09in0 417 tests g sacculifer 355 420 m are required to obtain a 18 o precision of 0 1in0 with 90 reliability 2 variance is a function of test diameter with greater variance being found in larger size fractions 3 variance is dependent on foraminiferal species 4 variance differences between glacial and interglacial samples are not significant 5 in the size interval 600 900 m a systematic relationship is not seen between size and 18 o or 13 c 6 replicate analysis is a practical method of improving isotope data quality size and species related variance differences are probably related to a number of factors including depth habitat seasonal production of tests species vertical migrations and vital and or symbiosis caused effects knowledge of data variance permits error assessment in sediment unmixing analyses and optimization of spectral estimates

in situ cosmogenic 10be and 21ne in sanidine and in situ cosmogenic 3he in fe ti oxide minerals abstract we report concentrations of in situ cosmogenic 10 be and 21 ne from coexisting quartz and sanidine separates and of cosmogenic 3 he in coexisting fe ti oxide minerals from ignimbritic successions of northern chile oxaya and lauca ignimbrites new mineral isotope pairs such as sanidine and fe ti oxide minerals are helpful in quantitative geomorphology for geological settings where the lithology lacks the commonly used minerals quartz pyroxene or olivine production rates in sanidine and fe ti oxide minerals were determined by normalizing nuclide concentrations to established production rates in quartz the experimentally determined production rates are compared to model production rates calculated with new cross sections for 3 he 21 ne and 10 be production from the individual target elements the mean experimental 21 ne production rate for five sanidine samples is 30 4 3 7 atoms g 1 yr 1 30 4 5 4 atoms g 1 yr 1 including the uncertainty of the 21 ne production rate in quartz p 21 ne qtz this is in excellent agreement with the modelled value of 28 3 atoms g 1 yr 1 which has an estimated uncertainty of 20 the 21 ne production rate in sanidine is thus about 50 higher than that in quartz the cosmogenic neon in sanidine is entirely released in low temperature steps 400 600 c and no signs of an interfering nucleogenic neon component were observed this is in stark contrast to quartz and makes sanidine an attractive mineral for terrestrial cosmogenic neon studies 3 he diffuses out of the sanidine structure preliminary results also indicate that sanidine is well suited for 10 be studies the mean experimental 10 be production rate from two sanidine samples is 4 45 0 38 atoms g 1 yr 1 4 45 0 42 atoms g 1 yr 1 including uncertainty of p 10 be qtz very close to the modelled value of 4 55 atoms g 1 yr 1 which has an estimated uncertainty of 20 we emphasize that 10 be and 21 ne production in sanidine is composition dependent therefore major element analyses should be carried out and production rates calculated on a sample by sample basis fe ti oxide minerals retain 3 he quantitatively experimentally derived production rates are in excellent agreement with new values derived from physical modelling the mean experimental 3 he production rate for five fe ti oxide minerals samples is 120 11 atoms g 1 yr 1 120 12 atoms g 1 yr 1 including the uncertainties of p 21 ne qtz compared to a mean modelled value of 124 atoms g 1 yr 1 which has an estimated uncertainty of 20 the variable chemical and structural composition of the solid solution lines of fe ti oxide minerals has little effect on the total 3 he production rate cosmogenic 21 ne is not produced in significant quantities in fe ti oxide minerals due to the absence of suitable target elements

reconstruction of hydrographic changes in the southern norwegian sea during the past 135 kyr and the impact of different foraminiferal mg ca cleaning protocols uit arctic university of norway the mohn foundation the research council of norway through its centres of excellence funding scheme project grant number 223259

cosmogenic noble gas studies in the oldest landscape on earth surface exposure ages of the dry valleys antarctica extraordinarily high surface exposure ages have been determined for sirius group tillites of mt fleming and mt feather as well as at localities in the inner dry valleys using cosmogenic helium and neon ages of 10 ma at mt fleming 5 3 ma at mt feather and 6 5 ma at insel mountain are among the highest nominal exposure ages published so far these values are minimal ages as they are based on the assumption of zero erosion and uplift the mt feather sample independently confirms the pre pliocene age of the sirius group sediments in the dry valleys as previously determined at mt fleming the insel mountain samples provide evidence for a landscape formation of the inner dry valleys not later than late miocene time assuming conservatively low values of 2 5 cm ma 1 for erosion rate and 50 m ma 1 for uplift rate we infer that the sirius group tillites at mt fleming were deposited earlier than 20 ma ago this indicates that the overriding of the dry valleys block of the transantarctic mountains by the east antarctic ice sheet occurred not later than the early miocene maximum long term erosion rates in the inner dry valleys must be 15 cm ma 1 down to altitudes 1000 m since such low erosion rates require permanently cold and hyperarid conditions the response of antarctica to the pliocene warm climatic episode must have been small cosmogenic nuclide data from both the inner dry valleys and the sirius group sediment localities support the hypothesis of a stable east antarctic ice sheet since at least late miocene time implying that the climate of antarctica was decoupled from that of lower southern latitudes we present also new elemental 21ne production rates of p21 mg 196 atoms g 1 yr 1 and p21 al 55 atoms g 1 yr 1 at sea level and high geomagnetic latitude these figures are consistent with a 3he production rate of p3 110 atoms g 1 yr 1 similar to previously published values this consistency provides evidence that pyroxene is retentive for both helium and neon over at least 10 ma cosmogenic ne in quartz and pyroxene has a 22ne 21ne cos ratio of 1 266 0 040 and 1 159 0 040 respectively

cosmic ray exposure dating with in situ produced cosmogenic 3he results from young hawaiian lava flows in an effort to determine the in situ production rate of spallation produced cosmogenic 3 he and evaluate its use as a surface exposure chronometer we have measured cosmogenic helium contents in a suite of hawaiian radiocarbon dated lava flows the lava flows ranging in age from 600 to 13 000 years were collected from hualalai and mauna loa volcanoes on the island of hawaii because cosmic ray surface exposure dating requires the complete absence of erosion or soil cover these lava flows were selected specifically for this purpose the 3 he production rate measured within olivine phenocrysts was found to vary significantly ranging from 47 to 150 atoms g 1 yr 1 normalized to sea level although there is considerable scatter in the data the samples younger than 10 000 years are well preserved and exposed and the production rate variations are therefore not related to erosion or soil cover data averaged over the past 2000 years indicate a sea level 3 he production rate of 125 30atoms g 1 yr 1 which agrees well with previous estimates the longer record suggests a minimum in sea level normalized 3 he production rate between 2000 and 7000 years 55 15atoms g 1 yr 1 as compared to samples younger than 2000 years 125 30 atoms g 1 yr 1 and those between 7000 and 10 000 years 127 19atoms g 1 yr 1 the minimum in production rate is similar in age to that which would be produced by variations in geomagnetic field strength as indicated by archeomagnetic data however the production rate variations a factor of 2 3 0 8 are poorly determined due to the large uncertainties in the youngest samples and questions of surface preservation for the older samples calculations using the atmospheric production model of o brien 1979 35 and the method of lal and peters 1967 11 predict smaller production rate variations for similar variation in dipole moment a factor of 1 15 1 65 because the production rate variations archeomagnetic data and theoretical estimates are not well determined at present the relationship between dipole moment and production rate will require further study precise determination of the production rate is an important uncertainty in the surface exposure technique but the data demonstrate that it is feasible to date samples as young as 600 years of age providing that there has been no erosion or soil cover therefore the technique will have important applications for volcanology glacial geology geomorphology and archaeology

dusty deep convection in the mars year 34 planet encircling dust event dusty convection convective activity powered by radiative heating of dust is a ubiquitous phenomenon in mars s atmosphere but is especially deep that is impactful on the middle atmosphere and widespread during planet encircling dust events pede that occur every few mars years my yet the relative roles of dusty deep convection and global dynamics such as the principal meridional overturning cell pmoc and the radiative tides in dust storm development and the vertical transport of dust and water are still unclear here observations from the mars climate sounder on board mars reconnaissance orbiter mro mcs are used to study dusty deep convection and its impact on middle atmospheric water content during the my 34 pede commenced june 2018 additional context is provided by mro mcs observations of the my 28 pede commenced june 2007 this investigation establishes that a few localized centers of dusty deep convection in the tropics formed in the initial phases of both pede simultaneously with a substantial increase in middle atmospheric water content the growth phase of the my 34 pede was defined by episodic outbreaks of deep convection along the acidalia and utopia storm tracks as opposed to less episodic more longitudinally distributed convective activity during the my 28 pede the most intense convection during both pede was observed in southern eastern tharsis where mro mcs observed multiple instances of deep convective clouds transporting dust to altitudes of 70 90 km these results suggest that martian pede typically contain multiple convectively active mesoscale weather systems

stable isotopes of planktonic foraminifera from tropical atlantic caribbean core tops implications for reconstructing upper ocean stratification abstract 18o values of nine tropical subtropical planktonic foraminiferal species with different preferential habitat depths collected from 62 core top samples along an east west transect across the tropical atlantic caribbean were used to test the applicability of interspecific 18o gradients for reconstructions of tropical upper ocean stratification in general the 18o difference 18o between intermediate and shallow dwelling species decreases and 18o between deep and intermediate dwellers increases with increasing thermocline depth towards the west the statistical significance of regional differences in 18o highlights 18o between the intermediate dwellers in particular globorotalia scitula and globorotalia tumida and the shallow dweller globigerinoides ruber pink as well as 18o between the deep dwellers globorotalia crassaformis or globorotalia truncatulinoides dextral and intermediate dwellers as most sensitive to changes in tropical atlantic thermocline depth based on the observed regional variations in interspecific 18o we propose a multispecies stratification index stratrop 18ointermediate 18oshallow 18odeep 18oshallow for the tropical ocean statistically significant differences in stratrop values between the e atlantic and the caribbean suggest that this index may be a useful tool to monitor variations in tropical upper ocean stratification in the geological record

paleoenvironmental changes from stable isotopes in planktonic foraminifera from eastern mediterranean sapropels abstract parallel stable oxygen isotope analyses of six planktonic foraminiferal species from an eastern mediterranean deep sea core present clear evidence for abnormal hydrographic regimes during deposition of sapropels s6 and s7 samples from s7 are characterized by a strong depletion of 18 o in epipelagic species while meso and bathypelagic forms are much less depleted this indicates a shallow pycnocline during deposition of s6 all species show a tendency towards lower values pointing to a far more extended pycnocline density stratification of the watercolumn is suggested by the isotopic differences between the species neogloboquadrina dutertrei globigerina bulloides and globorotalia scitula the latter represents the deepest element and shows the highest 18 o values carbon isotopes show two species groups each containing an epi meso and bathypelagic species under normal marine conditions group i globigerinoides ruber neogloboquadrina dutertrei and globorotalia truncatulinoides has relatively high 13 c values while species of group ii globigerina bulloides globorotalia scitula and globigerina quinqueloba show relatively low 13 c values indicating a stronger vital effect during sapropel deposition 12 c isotopes are enriched which we interpreted as the result of increased biological activity due to low oxygen stress conditions g scitula shows different eco phenotypes during times of sapropel deposition and the same may be true for the other members of group ii failure to adapt to adverse environmental conditions may be the cause for the absence of the two group i members globigerinoides ruber and globorotalia truncatulinoides in sapropel s6

large and mesoscale variability of the water masses and the deep chlorophyll maximum in the azores front 1 coupling between the physical and biological fields in the upper ocean around the azores front af was studied in summer 1998 during an oceanographic cruise to the southern azores islands 30 n 38 n and 20 w 33 w on the basis of conductivity temperature depth ctd acoustic doppler current profiler adcp and fluorescence data several large scale mesoscale and submesoscale physical features are described the adcp data and geostrophic field revealed an eastward transport associated with the azores current ac and weak countercurrents to the south and north of the ac the water mass field shows a strong latitudinal variation in the af with an eastward modification from the surface to 300 dbar the saline distribution strongly defined the af as a very sharp vertical front the horizontal thermohaline gradient increased to the east and reached a maximum at approximately 150 dbar the 16 2 c isotherm and 36 2 isohaline at 150 dbar precisely located the af along the whole area in agreement with the dynamic field to the west of 26 w the azores current was 140 km wide while the af was only 15 25 km wide to the east of 26 w the ac underwent a strong meandering the water mass characteristics in the southern part of the af show an eastward evolution between 18 c seawater and madeira mode water data from a ctd fluorometer mounted on an undulator system allowed the small scale structure of af to be mapped describing several eddies and meanders the deep chlorophyll maximum dcm showed highest values 0 9 to 1 2 mg chl m 3 toward the west 32 w on the southern side of the af chlorophyll concentrations at the dcm 0 4 0 6 mg chl m 3 on the northern side of the study area were moderate and fairly constant whereas low values 0 3 mg chl m 3 were measured at the very deep dcm 120 140 m in the southeast associated with high saline waters examination of a cold eddy showed similar chlorophyll concentrations to those found on the northern side of the af the thermohaline structure of the eddy was similar to the af with northern water enclosed within saline and warm southern water

opening the carbon isotope vital effect black box 2 quantitative model for interpreting foraminiferal carbon isotope data interpretation of carbon isotope records from late quaternary planktonic foraminifers are confounded due to the presence of a significant physiological component in the carbon isotopic signal a quantitative carbon isotope qc model is presented which relates the carbon isotopic composition of a foraminiferal shell to the physiological processes of respiration and symbiont photosynthesis and to the 13c value of seawater co2 the qc model is calibrated with physiological and stable isotopic data from laboratory experiments with living planktonic foraminifers model simulations of chamber and shell 13c values with the symbiont bearing foraminifers orbulina universa and globigerinoides sacculifer suggest 1 variations in symbiont density and photosynthetic rate light level or habitat depth are the primary physiological parameters controlling intraspecific carbon isotopic variability in these species 2 respiration has little effect on the 13c of o universa and 3 each chamber in a multichambered foraminiferal test will have a distinct 13c value depending on its position in the test whorl size 13c value relationships reported for g sacculifer from fossil assemblages can be explained as a function of increasing symbiont density during ontogenetic development

detailed japan sea paleoceanography during the last 25 kyr constraints from ams dating and δ18o of planktonic foraminifera abstract we have reconstructed paleoceanographic changes in the japan sea for the period from the last glacial maximum lgm to the present using expanded paleoclimate proxy records from two cores together with previously published results from three others a suite of new accelerated mass spectrometer ams 14 c dates provides chronologies that differ from earlier age models and suggest correlation between conditions in the japan sea changes in the north pacific and global sea level and climate changes we present evidence that reduced salinity of the japan sea surface water during the late pleistocene was due primarily to the increased importance of the precipitation evaporation balance at a time when lowered sea level had reduced water exchange with the pacific to a few percent of the present value

helium isotopic composition of the tabar lihir tanga feni island arc papua new guinea helium abundances and isotopic ratios have been measured in samples of geothermal gases submarine ultramafic xenoliths and subaerial mafic phenocrysts and xenoliths from the tabar lihirtanga feni tltf arc in the bismarck archipelago of papua new guinea these unusual volcanoes are produced by adiabatic decompression melting of subduction modified upper mantle and apparently carry an exceptionally large slab derived component they therefore provide an ideal setting for studying the role of subducted helium in arc volcanoes helium isotopic ratios in the geothermal fluids submarine xenoliths and most helium rich subaerial samples indicate the mantle source regions beneath the tabar island group and lihir island have 3he 4he ratios of about 7 2 times the atmospheric ratio r a whereas the mantle source for ambitle island feni group in the more southern tltf arc has a lower ratio of about 6 6 r a these ratios are only slightly lower than typical depleted upper mantle values of about 8 5 r a indicating that even severely slab modified mantle wedge carries a relatively minor slab derived helium component the systematically lower 3he 4he ratios of the ambitle samples are interpreted to reflect a slightly greater slab derived helium component helium isotopic ratios as low as 2 r a which are correlated with low total helium abundances were observed in subaerial augitic clinopyroxene phenocrysts coexisting olivine and sodium rich acmitic clinopyroxene have higher helium abundances and isotopic ratios this isotopic disequilibrium between coexisting mineral phases is interpreted as crustal level addition of a low 3he 4he component to an actively outgassing magma from which different mineral phases trap helium sequentially

the amplitude and phasing of climate change during the last deglaciation in the sulu sea western equatorial pacific 1 variations in tropical sea surface temperature patterns and the phasing relative to climate change in higher latitudes provide insight into the mechanisms of climate change on both orbital and shorter time scales here we present well dated high resolution records of planktonic foraminiferal 18o and mg ca based sst spanning the last deglaciation from the sulu sea located in the western equatorial pacific the results indicate that the last glacial maximum was 2 3 0 5 c cooler than present in the sulu sea with a concomitant decrease in sea surface salinity the similarity between variations in surface salinity in the sulu sea the western and eastern equatorial pacific and the greenland ice core record suggests that the observed changes in salinity reflect large scale rearrangement of atmospheric patterns which were coherent and synchronous throughout the northern hemisphere the results suggest that the glacial equatorial pacific climate was strongly influenced by both tropical and extra tropical forcing although it is not clear whether interannual enso variability is a good analogue of glacial interglacial climate change

vital effects and beyond a modelling perspective on developing palaeoceanographical proxy relationships in foraminifera this paper primarily reviews our recent work on the biology and geochemistry of foraminifera with respect to their use as paleoceanographic proxies our approach to proxy validation and development is described primarily from a modeler s point of view the approach is based on complementary steps in understanding the inorganic chemistry inorganic isotope fractionation and biological controls that determine paleo tracer signals in organisms used in climate reconstructions integration of laboratory experiments field and culture studies theoretical considerations and numerical modeling holds the key to the method s success we describe effects of life processes in foraminifera on stable carbon oxygen and boron isotopes as well as mg incorporation into foraminiferal calcite shells stable boron isotopes will be used to illustrate our approach we show that a mechanism based understanding is often required before primary climate signals can be extracted from the geologic record because the signals can be heavily overprinted by secondary non climate related phenomena moreover for some of the proxies fundamental knowledge on the thermodynamic inorganic basis is still lacking one example is stable boron isotopes a paleo ph proxy for which the boron isotope fractionation between the dissolved boron compounds in seawater was not precisely known until recently attempts to overcome such hurdles are described and implications of our work for paleoceanographic reconstructions are discussed

impact of the ocean carbonate chemistry on living foraminiferal shell weight comment on carbonate ion concentration in glacial age deep waters of the caribbean sea by w s broecker and e clark broecker and clark 2002 use the size normalized weight of planktic foraminifera to estimate the carbonate ion concentration co3 of atlantic glacial upper deep water this method was introduced by lohmann 1995 and is based on the fact that within a defined size fraction dissolution decreases shell weight in proportion to the degree of undersaturation with respect to caco3 based on the following assumptions 1 the thickness of the foraminiferal shell wall does not depend on growth conditions 2 the saturation co3 for calcite co3 sat increases by 20 mol kg 1 km 1 broecker and clark 2001 3 the weight loss slope is universal and ca 0 3 g mol kg 1 1 broecker and clark 2001 4 the offset between the bottom water and pore water co3 was the same during glacial time as during the holocene broecker and clark 2002 calculate that the co3 of atlantic glacial upper deep water was 14 mol kg 1 higher than during the holocene although they recognize that some of their assumptions are not strictly valid they do not assess the impact of those assumptions on their co3 estimate here we comment on several of those assumptions and attempt to quantify their impact on broecker and clark s 2002 calculations

planktic foraminiferal dissolution in the twilight zone abstract calcite dissolution of planktic foraminifers that settle from the surface ocean to depths has been assessed using the weight size relationship of tests and correlated to carbonate ion concentration co 3 2 of ambient sea water globigerina bulloides and globigerinita glutinata were sampled from the north atlantic and the arabian sea during different seasons spring and fall and the monsoons respectively test weight has been determined for single tests from narrow size classes 250 8 m and 300 7 m minimum test diameter initial test weight of both species in surface waters differs between regions and seasons weight loss of settling tests in the twilight zone between 100 and 1000 m water depths averaged 19 below the twilight zone 1000 2500 m no weight loss occurs on average and tests may even gain weight remineralization of settling planktic foraminiferal tests is most pronounced at maximum co 3 2 accordingly strong dissolution occurs in the twilight zone at the depth of maximum decrease in co 3 2 it is assumed that dissolution of planktic foraminiferal calcite is caused by co 3 2 under saturation inside the test buffered by diffusive exchange of co 3 2 ions with the ambient sea water through the pores and aperture consequently reconstruction of small scale differences in seawater co 3 2 from test weight alone is not feasible and systematic correlation between test weight and co 3 2 of the ambient sea water is statistically not significant at constant co 3 2 remineralization cannot be deduced from test weight neither at high nor low co 3 2 saturation in total our data suggest that the global vertical planktic foraminiferal caco 3 flux is about 19 lower than calculated by schiebel 2002 planktic foraminiferal sedimentation and the marine calcite budget global biogeochemical cycles 16 4 1065 doi 10 1029 2001gb001459

geochemical imprints of genotypic variants of globigerina bulloides in the arabian sea planktonic foraminifera record oceanic conditions in their shell geochemistry many palaeoenvironmental studies have used fossil planktonic foraminifera to constrain past seawater properties by defining species based on their shell morphology recent genetic studies however have identified ecologically distinct genotypes within traditionally recognized morphospecies signaling potential repercussions for palaeoclimate reconstructions here we demonstrate how the presence of globigerina bulloides cryptic genotypes in the arabian sea may influence geochemical signals of living and fossil assemblages of these morphospecies we have identified two distinct genotypes of g bulloides with either cool water type ii or warm water type i temperature preferences in the western arabian sea we accompany these genetic studies with analyses of mg ca and stable oxygen isotope 18o compositions of individual g bulloides shells both mg ca and 18o values display bimodal distribution patterns the distribution of mg ca values cannot be simply explained by seawater parameters and we attribute it to genotype specific biological controls on the shell geochemistry the wide range of 18o values in the fossil assemblage also suggests that similar controls likely influence this proxy in addition to environmental parameters however the magnitude of this effect on the 18o signals is not clear from our data set and further work is needed to clarify this we also discuss current evidence of potential genotype specific geochemical signals in published data on g bulloides geochemistry and other planktonic foraminiferal species we conclude that significant caution should be taken when utilizing g bulloides geochemistry for paleoclimate reconstruction in the regions with upwelling activity or oceanographic fronts

oxygen and carbon isotopes of individual shells of planktonic foraminifera from ontong java plateau equatorial pacific abstract analyses of single shells of orbulina universa and two other species show ranges of 2 in 18 o and 13 c at various levels in a box core from the western equatorial pacific seasonal and inter annual variations can account for only about half of this range variations in depths of calcification and in metabolic effects must account for the rest the large range must introduce considerable noise in multi shell analysis unless the number of shells in the sample is of the order of 50 or more we did not find a change in the range downcore nor did we find any evidence for the deglacial meltwater spike

morphology and relative frequency of planktic foraminiferal species in relation to oxygen isotopically inferred depth habitats abstract in modern low latitude open oceans planktic foraminiferal species with complex morphologies and or thickened shells usually dwell in the subsurface and deeper waters morphologically simple species with globular chambers and an umbilical aperture tend to be surface water dwellers this has led to the widely held belief that the relative depth habitats of extinct forms can be deduced from their test shape with planoconical or keeled species dwelling below globigerinids yet oxygen isotope ratios have shown some globorotaliids e g morozovella to have been surface dwellers by determining the relative depth position of many different fossil groups from their oxygen isotope ratios i found no relationship between test shape and preferred depth habitat many keeled and or planoconical forms globotruncana contusotruncana morozovella fohsella and turborotalia as well as unkeeled groups acarinina globigerinatheka some jenkinsella and globoconella were surface or subsurface dwellers deep dwellers include the keeled planomalina globotruncanita and planorotalites the unkeeled catapsydrax some jenkinsella and most paleogene globigerinids usually the most common group shows relatively low oxygen isotope ratios indicating that surface dwelling species are more abundant and or had a shorter life cycle with a larger shell output the tests of most inferred surface dwellers are relatively susceptible to dissolution with the globigerinathekids and acarinina senni as notable exceptions the low diversity oligocene faunas dominated by globigerinids followed the extinction of the morphologically diverse surface dwelling part of the late eocene fauna not the elimination of deep dwelling species

late quaternary biostratigraphy and paleotemperatures of the red sea and the gulf of aden based on planktonic foraminifera and pteropods abstract the quantitative distributions of planktonic foraminifera and pteropods were analyzed in seven red sea cores and two deep sea cores from the gulf of aden and off sokotra island biostratigraphic intervals were distin guished corresponding to oxygen isotope stages 1 5 in the red sea and stages 1 3 in the gulf of aden the faunal assemblages demonstrate that in the red sea hydrological conditions changed significantly during the late quaternary especially at the last glacial maximum when water exchange at the bab el mandeb straits was at a minimum and at the pleistocene holocene boundary at the end of deglaciation water exchange renewal and pluvial conditions resulted in surface salinity decrease and stable stratification which was followed by a rise in planktonic fauna abundance and stagnation of bottom waters the more constant composition of rather cold water subtropical faunal assemblages in the gulf of aden during the last 40 000 50 000 yrs points to more stable hydrological parameters and to local upwelling or influx of arabian upwelling waters during the last stadial mean annual sea surface temperatures fell by at least 5 c compared to the present in the central part of the red sea and by 3 5 c in the western gulf of aden

silicon isotope fractionation by marine sponges and the reconstruction of the silicon isotope composition of ancient deep water the silicon isotope composition d30si of biogenic opal provides a view of the silica cycle at times in the past reconstructions require the knowledge of silicon isotope fractionation during opal biomineralization the d30si of specimens of hexactinellid sponges and demosponges growing in the modern ocean ranged from 1 2 to 3 7 n 6 corresponding to the production of opal that has a d30si value 3 8 0 8 more negative than seawater silicic acid and a fractionation factor a of 0 9964 this is three times the fractionation observed during opal formation by marine diatoms and terrestrial plants and is the largest fractionation of silicon isotopes observed for any natural process on earth the d30si values of sponge spicules across the eocene oligocene boundary at ocean drilling program site 689 on maud rise range from 1 1 to 3 0 overlapping the range observed for sponges growing in modern seawater

calcification of the planktonic foraminifera globigerina bulloides and carbonate ion concentration results from the santa barbara basin planktonic foraminiferal calcification intensity reflected by shell wall thickness has been hypothesized to covary with the carbonate chemistry of seawater here we use both sediment trap and box core samples from the santa barbara basin to evaluate the relationship between the calcification intensity of the planktonic foraminifera species globigerina bulloides measured by area density g m2 and the carbonate ion concentration of seawater co32 we also evaluate the influence of both temperature and nutrient concentration po43 on foraminiferal calcification and growth the presence of two g bulloides morphospecies with systematically different calcification properties and offset stable isotopic compositions was identified within sampling populations using distinguishing morphometric characteristics the calcification temperature and by extension calcification depth of the more abundant normal g bulloides morphospecies was determined using 18o temperature estimates calcification depths vary seasonally with upwelling and were used to select the appropriate co32 temperature and po43 depth measurements for comparison with area density seasonal upwelling in the study region also results in collinearity between independent variables complicating a straightforward statistical analysis to address this issue we use additional statistical diagnostics and a down core record to disentangle the respective roles of each parameter on g bulloides calcification our results indicate that co32 is the primary variable controlling calcification intensity while temperature influences shell size we report a modern calibration for the normal g bulloides morphospecies that can be used in down core studies of well preserved sediments to estimate past co32

distribution and ecology of the globigerinoides ruber globigerinoides elongatus morphotypes in the azores region during the late pleistocene holocene abstract globigerinoides ruber is the dominant taxon in the north atlantic subtropical gyre nowadays limited to the north by the azores current it is highly sensitive to recent and late pleistocene azores front current system variability in this study we analyse the distribution of five individual morphotypes of the g ruber g elongatus plexus g ruber s s g ruber cyclostoma type g elongatus g elongatus cf 1 g elongatus pyramidical type and g ruber kummerform gr in a core ata13 of kt1 collected southwest of the azores islands and located in a strategical position near the present day boundary of the subtropical gyre azores front current system stg afcs micropaleontological and stable isotope analyses can provide new insights on the ecological preferences of the g ruber chromotypes and some selected morphotypes especially the less studied g ruber cyclostoma type their distribution pattern shows cyclic oscillations linked to climatic variability at orbital and millennial scales g elongatus clearly dominated the g ruber g elongatus assemblage during the interglacials while g ruber cyclostoma type reached their maxima abundances during glacial periods furthermore changes in the relative abundance of warm g elongatus and cool water g ruber cyclostoma type morphotypes represent a powerful tool to track the position occupied by the subtropical gyre azores current stg ac boundary during the last 74 7 kyr

mass spectrometric identification of cosmic ray produced neon in terrestrial rocks with multiple neon components studies of cosmic ray produced nuclides in terrestrial rocks are expected to provide important geomorphological and glaciological information such as surface exposure ages erosion rates and extent of glacial cover in the case of the stable nuclide21ne the cosmic ray produced component may represent but one of several components and a component resolution based on three isotope correlations is essential we developed analytical techniques which permit accurate corrections for all interfering ions we show for our modified nier source that corrections for doubly charged species based on constant charge state ratios are not satisfactory the improved techniques permit isotopic studies of 106 atoms of21ne the spallation ratio 22ne 21ne c from si was calibrated using a quartz separate from an allan hills sandstone and yields a value of1 243 0 022 this ratio is expected to be essentially constant for terrestrial quartz samples and should be useful in component resolutions the stepwise release of ne at increasing temperatures shows that cosmic ray produced ne is released from quartz at rather low temperatures this permits an estimate of the activation energy for ne diffusion in quartz 90 10 kj mol

δ18o seasonality of planktonic foraminifera from southern ocean sediment traps latitudinal gradients and implications for paleoclimate reconstructions abstract the oxygen isotopic record obtained from globigerina bulloides globorotalia inflata and neogloboquadrina pachyderma s was analysed for 5 sediment traps moored in the southern ocean and southwest pacific the traps extend from subtropical to the polar frontal environments providing the first analysis of seasonal foraminiferal 18 o records from these latitudes comparison between the foraminiferal records and various equations for predicted 18 o of calcite reveals that the predicted 18 o is best captured by the equations of epstein et al 1953 epstein s buchsbaum r lowenstam h a urey h c 1953 revised carbonate water isotopic temperature scale geological society of america bulletin 64 1315 1326 and kim and o neil 1997 kim s t o neil j r 1997 equilibrium and non equilibrium oxygen isotope effects in synthetic carbonates geochimica et cosmochimica acta 61 3461 3475 the epstein equation shows a constant offset from the 18 o of g bulloides and n pachyderma s across the full range of latitudes the seasonal range in 18 o values for these two species implies a near surface habitat across all sites while g inflata most likely dwells at 50 m depth a significant finding in this study was that offsets from predicted 18 o for g bulloides do not correlate to changes in the carbonate ion concentration this suggests that co 3 2 in and of itself may not capture the full range of carbonate chemistry conditions in the marine system this sediment trap deployment also reveals distinct seasonal flux patterns for each species comparison between flux weighted isotopic values calculated from the sediment traps and the isotopic composition of nearby surface sediments indicates that the sedimentary records retain this seasonal imprint at the 51 s site g bulloides has a spring flux peak while n pachyderma s is dominated by summer production the imprint of these differing seasonal production patterns on the flux weighted 18 o values results in more depleted 18 o for n pachyderma s than for g bulloides interpretations of n pachyderma s isotopic composition as a record of subsurface conditions may therefore need to be refined with implications for interpretation of depleted glacial 13 c for this species sigman boyle 2000 sigman d m boyle e a 2000 glacial interglacial variations in atmospheric carbon dioxide nature 407 859 869

oxygen isotope fractionation between calcite and fluid as a function of growth rate and temperature an in situ study the 18o content of carbonates expressed as 18o is widely used in paleothermometry yet it is clear from comparison of experimental results and natural carbonate samples that chemical isotopic equilibrium is not always achieved in nature this observation underscores the importance of exploring possible effects of growth rate on isotopic fractionation which is the focus of this study in situ secondary ion mass spectrometry sims analyses of 18o were performed on single crystals of experimentally grown calcite the change in growth rate v over time within each crystal was monitored by addition of multiple rare earth element ree spikes into the fluid from which the calcite grew the values of 18o in bulk calcites and experimental fluids were measured by stable isotope ratio mass spectrometers the average sims 18o overlaps with those determined by conventional mass spectrometry within analytical uncertainty the fractionation factor expressed as 18o approaches its equilibrium value in slowly grown calcites v 0 02 nm s and decreases by 1 5 with increasing growth rate from 10 3 to 0 34 nm s here 18o 103 ln 18o and 18o 18o 16o calcite 18o 16o fluid our results provide the first in situ evidence that under equilibrium conditions 18o may be depleted in the near surface region of calcite relative to the bulk crystal lattice and that this 18o depleted zone can be captured during rapid crystal growth crystal growth rate is therefore a potentially important consideration when using 18o in natural carbonates as a proxy for ocean and terrestrial temperature