boron isotopes and b ca in benthic foraminifera proxies for the deep ocean carbonate system abstract accurate records of the state of the ocean carbonate system are critical for understanding past changes in pco 2 ocean acidification and climate the chemical principles underlying the proxy of oceanic ph provided by the boron isotope ratio of foraminiferal carbonate are relatively well understood but the proxy s reliability has been questioned we present 76 new multi collector inductively coupled plasma mass spectrometry mc icpms 11 b measurements on a range of benthic foraminifera from 23 late holocene samples from the atlantic that reaffirm the utility of the 11 b ph proxy our boron isotope measurements on 10 benthic foraminifera tests typically yield a precision of 0 25 at 2 s d equivalent to 0 03 ph units 11 b values of epifaunal species are within analytical uncertainty of those predicted from a simple model assuming sole incorporation of b oh 4 from seawater and no vital effects using the independently determined fractionation factor of 1 0272 between 11 b 10 b of aqueous boron species infaunal foraminifera are consistent with this model but record the combined effects of lower pore water 11 b and ph no influence of partial dissolution or shell size on 11 b is observed we have also measured the b ca ratios of the same samples for individual cibicidoides species b ca shows a good correlation with co 3 2 but the b ca of different co occurring species morphotypes varies considerably these effects are not seen in 11 b which may therefore provide a more robust proxy of the ocean carbonate system whilst in theory 11 b and b ca can be combined to provide a quantitative reconstruction of alkalinity and dissolved inorganic carbonate dic in practice this is precluded by propagated uncertainties 11 b data give significant constraints on foraminifera calcification mechanisms and seem most simply explained by incorporation of b oh 4 into a hco 3 pool which is then completely incorporated in foraminiferal caco 3 our demonstration of the predictable variation of 11 b with ph across a wide range of species and locations provides confidence in the application of mc icpms measurements of foraminiferal 11 b to reconstruct past changes in the ocean carbonate system

seawater ph pco2 and co2 3 variations in the caribbean sea over the last 130 kyr a boron isotope and b ca study of planktic foraminifera abstract here a new analytical methodology is described for measuring the isotopic composition of boron in foraminifera using multicollector inductively coupled plasma mass spectrometry mc icpms this new approach is fast 10 samples analysed in duplicate per analytical session and accurate to better than 0 25 at 95 confidence with acceptable sample size requirements 1 3 mg of carbonate a core top calibration of several common planktic and two benthic species from geographically widespread localities shows a very close agreement between the isotopic composition measured by mc icpms and the isotopic composition of b oh 4 in seawater as predicted using the recently measured isotopic equilibrium factor of 1 0272 at the depth of habitat a down core and core top investigation of boron concentration b ca ratio shows that the partition coefficient is influenced by co2 3 complicating the application of this proxy nevertheless it is demonstrated that these two proxies can be used to fully constrain the carbonate system of surface water in the caribbean sea odp site 999a over the last 130 kyr this reconstruction shows that during much of the holocene and the last interglacial period surface water at site 999a was in equilibrium with the atmosphere with respect to co2 during the intervening colder periods although the surface water pco2 was lower than the holocene it was a minor to significant source of co2 to the atmosphere possibly due to either an expansion of the eastern equatorial atlantic upwelling zone or a more local expansion of coastal upwelling in the southern caribbean such reorganisation of the oceanic carbonate system in favour of a larger source of co2 to the atmosphere from the equatorial ocean may require mechanisms responsible for lowering atmospheric co2 during glacial periods to be more efficient than previously supposed

antarctic intermediate water properties since 400 ka recorded in infaunal uvigerina peregrina and epifaunal planulina wuellerstorfi benthic foraminifera reconstruction of intermediate water properties is important for understanding feedbacks within the ocean climate system particularly since these water masses are capable of driving high low latitude teleconnections nevertheless information about intermediate water mass evolution through the late pleistocene remains limited this paper examines changes in antarctic intermediate water aaiw the most extensive intermediate water mass in the modern ocean through the last 400 kyr using the stable isotopic composition 18o and 13c and trace element concentration mg ca and b ca of two benthic foraminiferal species from the same samples epifaunal planulina wuellerstorfi and infaunal uvigerina peregrina our results confirm that the most reasonable estimates of aaiw temperature and co2 3 are generated by mg cau peregrina and b cap wuellerstorfi respectively we present a 400 kyr record of intermediate water temperature and co2 3 from a sediment core from the southwest pacific dsdp site 593 40 30 s 167 41 e 1068 m water depth which lies within the core of modern aaiw our results suggest that a combination of geochemical analyses on both infaunal and epifaunal benthic foraminiferal species yields important information about this critical water mass through the late pleistocene when combined with two nearby records of water properties from deeper depths our data demonstrate that during interglacial stages of the late pleistocene aaiw and circumpolar deep water cpdw have more similar water mass properties temperature and 13c while glacial stages are typified by dissimilar properties between aaiw and cpdw in the southwest pacific our new co2 3 record shows short time scale variations but a lack of coherent glacial interglacial variability indicating that large quantities of carbon were not stored in intermediate waters during recent glacial periods

determination of b ca of natural carbonates by hr icp ms we report a new method for hr icp ms based accurate and precise b ca determination from low mass natural carbonates 5 g caco3 utilizing a mixed acid matrix 0 1 m hno3 and 0 3 m hf and accurate matrix matching technique our procedural b ca blank of 2 0 1 0 mol mol internal precision 1 0 average within run external precision 4 0 2 and rapid sample analysis 60 samples day make the method well suited for routine measurements established methods of b ca determination require 65 g caco3 to achieve a comparable external precision of 3 5 2 we report a b ca detection limit of 2 mol mol compared to 10 mol mol for previous methods a fivefold improvement the method presented here can determine a wide range of b ca 9 0 250 mol mol in mass limited samples with considerable tolerance for matrix matching efficiency 30 the long term reproducibility of b ca measured on cambridge in house consistency standards containing 20 85 and 200 mol mol of b ca are 3 7 2 n 100 3 9 2 n 150 and 3 2 2 s n 180 respectively a host of other trace element to ca ratios can also be determined at comparable external precision from samples containing 5 g caco3 this method is suitable for trace element analysis of single foraminifera shells

the annual cycle in equatorial convection and sea surface temperature abstract the coupled atmosphere ocean system in the equatorial eastern pacific and atlantic exhibits a distinct annual cycle that is reflected in contrasting conditions at the times of the two equinoxes the contrasts are so strong that they dominate the annual march of zonally averaged outgoing longwave radiation for the equatorial belt the march equinox corresponds to the warm season when the equatorial cold tongues in the eastern pacific and atlantic are absent with the onset of summer monsoon convection over colombia central america and west africa in may june northward surface winds strengthen over the eastern pacific and atlantic the equatorial cold tongues reappear and the marine convection shifts from the equatorial belt to the intertropical convergence zones itczs along 8 n as the northern summer program the itczs remain strong and shift northward to new 10 n while sea surface temperature sst continues to drop over the cold tongues and the southern tropics perhaps in response to the

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

dynamical diagnostics of the sst annual cycle in the eastern equatorial pacific part ii analysis of cmip5 simulations in this study a simple coupled framework established in part is utilized to investigate inter model diversity in simulating the equatorial pacific sst annual cycle sstac it demonstrates that the simulated amplitude and phase characteristics of sstac in models are controlled by two internal dynamical factors the damping rate and phase speed and two external forcing factors the strength of the annual and semi annual harmonic forcing these four diagnostic factors are further condensed into a dynamical response factor and a forcing factor to derive theoretical solutions of amplitude and phase of sstac the theoretical solutions are in remarkable agreement with observations and cmip5 simulations the great diversity in the simulated sstacs is related to the spreads in these dynamic and forcing factors most models tend to simulate a weak sstac due to their weak damping rate and annual harmonic forcing the latter is due to bias in the meridional asymmetry of the annual mean state of the tropical pacific represented by the weak cross equatorial winds in the cold tongue region

evolution dynamics of tropical ocean atmosphere annual cycle variability abstract the structure of ocean atmosphere annual cycle variability is extracted from the revised comprehensive ocean atmosphere data set ssts surface winds and the latent heat lh and net shortwave sw surface fluxes using the covariance based rotated principal component analysis method the coupled annual cycle variability is concisely described using two modes that are in temporal quadrature the first peaking in june july and dec jan represents monsoonal flow onto indochina central america and western africa the second mode peaks in september october and march april when it represents the extreme phases of the sst annual cycle in the eastern oceans analysis of the surface momentum balance in the pacific cold tongue core shows the equatorial flow and in particular the zonal wind to be dynamically consistent with the sst gradient during both the cold tongue s nascent jun jul and mature sep oct phases the dynamical consistency improves when the impact of near surface static stability v

lithium in foraminiferal shells implications for high temperature hydrothermal circulation fluxes and oceanic crustal generation rates the lithium content of planktonic foraminiferal calcite has been determined to evaluate temporal variability of seawater li concentrations over the past 116 m y mean foraminiferal calcite lithium calcium in each time interval is no more than 16 greater nor 25 less than the mean li ca of all samples li ca minima are observed for samples from 50 60 m y and 80 90 m y with li ca about 25 lower than in adjacent time intervals at no time during the past 40 m y does mean li ca appear to be higher than that at present subject to the limitations imposed by sample coverage and diagenesis a similar conclusion holds for the past 116 m y coupled with an oceanic mass balance model for li these data suggest that 1 oceanic li concentrations and therefore high temperature hydrothermal circulation fluxes during the past 40 m y and perhaps the past 100 m y have not been more than perhaps 30 40 greater than at present for intervals any longer than a million years at most and 2 these fluxes werenot a factor of two higher 100 m y ago by inference variations in oceanic crustal generation rates over these time periods are similarly limited decreases in hydrothermal circulation fluxes and crustal generation rates or fluctuations up to 20 in these rates of a few million years duration arenot necessarily ruled out by the li ca data the lack of variability in li ca over time is not unequivocal evidence that hydrothermal fluxes have not varied because the rates of removal processes may be linked to changes in input fluxes

composition and geochemistry of clay sediments offshore the northeastern sicilian coast southeastern tyrrhenian sea italy abstract grain size mineralogical and chemical analyses were carried out on fine fraction of sediments collected in the gulfs of patti and milazzo two borderland basins in the southern tyrrhenian extending offshore the northeastern sicilian coast results of granulometric analyses on size fractions smaller than 63 m showed that the investigated samples can be classified mainly as clayey silts the coarse fractions 63 m examined by optical microscopy consist of a terrigenous component representing in some samples about 98 99 of the total sediment and by a biogenic component this latter is mainly made up of benthic foraminifera the mineralogical composition of the fine fraction determined by x ray diffractometry is represented by muscovite quartz clay minerals carbonates calcite and in some samples by calcium and sodium rich plagioclases the method of saturation with k and mg followed by ethylene glycol solvation and heating are used for a qualitative determination of the clay minerals clay mineralogical composition is characterized by the dominance of clinochlore and illite with minor amounts of smectite especially montmorillonite and vermiculite the chemical data reflect the main mineralogical composition showing a uniform quantitative composition with high al 2 o 3 and sio 2 values and very few variations in the relative abundance of the other components the cr th th sc th co and la sc ratios suggest a felsic nature of the source rocks finally the geochemical parameters such as v cr u th ni co and cu zn ratios indicate that examined sediments were deposited under oxic environments

why the itcz is mostly north of the equator abstract although the distribution of sunshine is symmetrical about the equator the earth s climate is not climatic asymmetries are prominent in the eastern tropical pacific and atlantic oceans where the regions of maximum sea surface temperature convective cloud cover and rainfall are north of the equator this is the result of two sets of factors interactions between the ocean and atmosphere that are capable of converting symmetry into asymmetry and the geometries of the continents that determine in which longitudes the interactions are effective and in which hemisphere the warmest waters and the intertropical convergence zone are located the ocean atmosphere interactions are most effective where the thermocline is shallow because the winds can readily affect sea surface temperatures in such regions the thermocline happens to shoal in the eastern equatorial pacific and atlantic but not in the eastern indian ocean because easterly trade winds prevail over the tropical atlantic and pacific wher

metal organic associations in sediments i comparison of unpolluted recent and ancient sediments and sediments affected by anthropogenic pollution abstract the concentrations of 19 trace elements were determined by plasma emission spectrometry in organic fractions organic solvent extractables soluble humics protokerogen and kerogen concentrates separated from various recent and ancient sediments mangrove sediments algal mats oil shales phosphorites as well as sediments polluted by industrial metal emissions rhine river port pirie smelter effluent often the organic constituents were found to be enriched in trace elements especially b v mn co ni cu zn as mo ag cd sb hg and pb up to more than three orders of magnitude compared to the bulk sediments indicating the importancesof organic substances with respect to transport and fixation of trace elements within sediments the formation of metal organic associations was found to reflect the environment of deposition marine to terrestrial as well as diagenetic transformations recent to ancient against an unpolluted natural background increasing metal pollution led to increasing metal potake by organic substances especially for b cr fe co cu zn as cd and pb

caco3 dissolution in sediments of the ceara rise western equatorial atlantic we have used porewater sampling by in situ techniques including whole core squeezing as well as by shipboard sectioning and whole core squeezing to estimate the rates of sedimentary organic matter oxidation and caco3 dissolution at seven sites on the ceara rise in the western equatorial atlantic ocean porewater no3 profiles at all sites show a pattern indicative of active organic matter oxidation in the upper 15 20 cm of the sediments and in a buried organic rich layer the organic c oxidation rate generally decreases with increasing water depth from a value of 22 mol cm2 y at the shallowest site 3279 m to 14 mol cm2 y at the deepest site 4675 m over this depth range the bottomwaters vary from moderately supersaturated with respect to calcite to strongly undersaturated high resolution alkalinity profiles measured in porewaters collected by in situ whole core squeezing yield estimated ca2 fluxes of 11 mol cm2 y at a site located at the depth of the calcite saturation horizon and 7 6 zmol cm2 y at a moderately undersaturated site ca2 fluxes calculated from profiles in porewaters collected by relatively coarse resolution in situ sampling methods clearly indicate that there is caco3 dissolution above the calcite saturation horizon the dissolution of aragonite may contribute to the dissolution flux at the shallowest site these ca2 fluxes as well as fluxes estimated from a model of sedimentary organic matter oxidation and calcite dissolution indicate that 36 66 of the caco3 rain to the seafloor dissolves at sites at and above the calcite saturation horizon while 52 75 of the rain dissolves at sites below this depth when these results are incorporated into the oceanic caco3 budget of milliman 1993 they indicate that 35 of caco3 production is preserved in the deep sea they suggest a caco3 accumulation rate that is 27 lower than that estimated by milliman 1993 our corg oxidation caco3 dissolution model indicates that a large fraction of the caco3 dissolution that is occurring on the ceara rise is attributable to the neutralization of metabolic acids produced during organic matter oxidation the efficiency with which organic matter oxidation dissolves caco3 that is the ratio caco3 dissolution attributable to organic matter oxidation organic matter oxidation rate generally increases as degree of undersaturation of bottomwaters increases however there are deviations from the general trend that can be attributed to site to site variations in the kinetics of organic matter oxidation and calcite dissolution this result indicates that the dissolution of caco3 as a result of organic matter oxidation in the deep sea may mask the effects of variations in surface water caco3 productivity and bottomwater chemistry on the accumulation rate of caco3 in deep sea sediments

trace element distributions in surficial sediments of the northern tyrrhenian sea contribution to heavy metal pollution assessment the trace element distributions in surficial sediment of tyrrhenian sea have been investigated as a part of a series of studies on the environmental quality of the area off the tuscany coast west central italy this research has focused on the presence of possible contaminated zones it also provides data for the identification and future monitoring and control of pollution sources the study of numerous surface sediments and core samples has made it possible to distinguish between heavy metal enrichments related to natural sources and other anomalies caused by anthropogenic contamination over much of the basin the surface pb cu zn and as contents appear considerably enriched relative to those below 15 cm among these metals pb shows the highest and most widespread enrichment only in the case of some coarse grained sediments close to the mouth of cecina river it is possible to relate anomalously high zn contents to natural sources in all other sampling stations the enrichments of pb cu zn and as are ascribed to man s influence the sediment distributions of co cr and ni do not seem to be related to anthropogenic activities rather they mirror influx of materials derived from sources of ophiolitic rock the distribution of barium shows only two significant positive anomalies and both are related to natural causes concentrations of vanadium are high in a zone close to an important smelting plant these are thought to be of anthropogenic origin

formation and variability of a northerly itcz in a hybrid coupled agcm continental forcing and oceanic atmospheric feedback abstract despite the equatorial symmetry of the annual mean insolation the intertropical convergence zone itcz and the collocated band of high sea surface temperature sst assume perennial northern latitudes over the eastern pacific and atlantic an atmospheric general circulation model is coupled with an intermediate ocean model to study continental forcing and oceanic atmospheric interaction that act to break the equatorial symmetry the model reaches a statistically symmetric mean state under perfectly symmetric conditions with the continental coasts running along meridians when a bulge of landmass is added to the eastern continent north of the equator it initiates a coupled ocean atmosphere wave front that propagates westward across the ocean basin cooling the ocean surface and suppressing deep convection on and south of the equator as a result the itcz shifts into the northern hemisphere in contrast to this basinwide response little latitudinal asymmetry develops in the coupled model when

controls on boron incorporation in cultured tests of the planktic foraminifer orbulina universa culture experiments with living planktic foraminifers reveal that the ratio of boron to calcium b ca in orbulina universa increases from 56 to 92 mol mol 1 when ph is raised from 7 61 0 02 to 8 67 0 03 total scale across this ph range the abundances of carbonate bicarbonate and borate ions also change 530 500 and 170 mol kg 1 respectively thus specific carbonate system control s on b ca remain unclear complicating interpretation of paleorecords b ca in cultured o universa also increases with salinity 55 72 mol mol 1 from 29 9 35 4 and seawater boron concentration 62 899 mol mol 1 from 4 40 ppm b suggesting that these parameters may need to be taken into account for paleorecords spanning large salinity changes 2 and for samples grown in seawater whose boron concentration b sw differs from modern by more than 0 25 ppm while our results are consistent with the predominant incorporation of the charged borate species boh4 into foraminiferal calcite the behavior of the partition coefficient kd defined as b ca calcite boh4 hco3 seawater cannot be explained by borate incorporation alone and suggests the involvement of other ph sensitive ions such as co32 for a given increase in seawater boh4 the corresponding increase in b ca is stronger when boh4 is raised by increasing b sw than when it is raised by increasing ph these results suggest that b incorporation controls should be reconsidered additional insight is gained from laser ablation icp ms profiles which reveal variable b ca distributions within individual shells

comparison of atlantic and pacific paleochemical records for the last 215 000 years changes in deep ocean circulation and chemical inventories abstract detailed cd ca and 13 c data have been obtained for benthic foraminifera from western north atlantic and equatorial pacific sediment cores in the modern ocean both tracers are closely linked to nutrient distributions the sedimentary records for both tracers indicate that bottom waters overlying the atlantic site have been nutrient depleted relative to those at the pacific site over the last 215 000 years from this evidence it is reasonable to infer that there has been a continuous net flux of nutrient depleted water from the western north atlantic into the pacific this exchange has undergone significant fluctuations with the export of nutrient depleted atlantic water diminishing by about a factor of two relative to the inflow from southern ocean sources over the last 215 000 years carbon isotope fluctuations in both regions are dominated by variable storage of isotopically light carbon on continents with a lesser contribution from these deep ocean circulation changes the cadmium signal in the north atlantic is dominated by changes in deep ocean circulation patterns cadmium shows less variability in the pacific which may reflect changes in the global average cadmium content or minor changes in deep pacific circulation patterns using these records to estimate global averages it appears that glacial ocean water had 22 more cd and 0 46 less 13 c than the modern ocean these numbers are estimates which may be revised as more data become available although they are not likely to be as much as 20 in error for cd or 0 2 for 13 c relative north atlantic deep water nadw formation rates are modulated with a significant 41 kyr periodicity linked to obliquity induced variations in high latitude insolation nadw lags 8 2 kyr behind insolation however

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

li partitioning into coccoliths of emiliania huxleyi evaluating the general role of vital effects in explaining element partitioning in biogenic carbonates

west antarctic ice sheet retreat driven by holocene warm water incursions glaciological and oceanographic observations coupled with numerical models show that warm circumpolar deep water cdw incursions onto the west antarctic continental shelf cause melting of the undersides of floating ice shelves because these ice shelves buttress glaciers feeding into them their ocean induced thinning is driving antarctic ice sheet retreat today here we present a multi proxy data based reconstruction of variability in cdw inflow to the amundsen sea sector the most vulnerable part of the west antarctic ice sheet during the holocene epoch from 11 7 thousand years ago to the present the chemical compositions of foraminifer shells and benthic foraminifer assemblages in marine sediments indicate that enhanced cdw upwelling controlled by the latitudinal position of the southern hemisphere westerly winds forced deglaciation of this sector from at least 10 400 years ago until 7 500 years ago when an ice shelf collapse may have caused rapid ice sheet thinning further upstream and since the 1940s these results increase confidence in the predictive capability of current ice sheet models

determination of multiple element calcium ratios in foraminiferal calcite by quadrupole icp ms a method has been developed for rapid and precise simultaneous determination of nine element ca ratios in foraminiferal tests directly from intensity ratios using external matrix matched standards on a quadrupole inductively coupled plasma mass spectrometer icp ms all quantification isotopes are determined in pulse mode to avoid cross calibration small argide 40ar26mg interferences on 66zn are corrected by using two additional mg and zn standards a stable signal conducive for high precision measurements is obtained by cone conditioning variable calcium concentration has negligible effect on li al mn and sr but ca concentrations for standards and samples need to be constrained at a similar level for precise measurements of zn cd and u aliquots of samples are first analyzed for ca concentrations on an inductively coupled plasma atomic emission spectrometer icp aes and the remaining solutions are diluted to ca concentration of 100 ppm for ratio measurements to assure data quality the long term reproducibility of the method yielded precisions of li ca 2 4 b ca 4 2 mg ca 1 4 al ca 14 mn ca 0 9 zn ca 2 8 1 2 7 8 mol mol and 5 1 0 5 1 2 mol mol sr ca 0 9 cd ca 2 4 0 07 0 24 mol mol and 4 8 0 01 0 07 mol mol and u ca 2 5 for foraminiferal samples as small as 60 g

the effect of ocean alkalinity and carbon transfer on deep sea carbonate ion concentration during the past five glacial cycles abstract glacial interglacial deep indo pacific carbonate ion concentration co 3 2 changes were mainly driven by two mechanisms that operated on different timescales 1 a long term increase during glaciation caused by a carbonate deposition reduction on shelves i e the coral reef hypothesis and 2 transient carbonate compensation responses to deep ocean carbon storage changes to investigate these mechanisms we have used benthic foraminiferal b ca to reconstruct deep water co 3 2 in cores from the deep indian and equatorial pacific oceans during the past five glacial cycles based on our reconstructions we suggest that the shelf to basin shift of carbonate deposition raised deep water co 3 2 on average by 7 3 0 5 se mol kg during glaciations oceanic carbon reorganisations during major climatic transitions caused deep water co 3 2 deviations away from the long term trend and carbonate compensation processes subsequently acted to restore the ocean carbonate system to new steady state conditions deep water co 3 2 showed similar patterns to sediment carbonate content caco3 records on glacial interglacial timescales suggesting that past seafloor caco3 variations were dominated by deep water carbonate preservation changes at our studied sites

variations in mg ca and sr ca ratios of planktonic foraminifera caused by postdepositional dissolution evidence of shallow mg dependent dissolution a comparative study has been made of two species of planktonic foraminifera g tumida and g sacculifer in a depth transect on the ontong java plateau western equatorial pacific g tumida tests from core top sediments showed decreasing mg ca 2 65 1 25 mmol mol and sr ca 1 50 1 16 mmol mol ratios with increasing water depth 1600 4400 m while no such variation was found in g sacculifer tests in excess of 355 m average mg ca 3 6 mmol mol sr ca 1 4 mmol mol artificial dissolution of g tumida tests led to a decrease in both mg ca and sr ca but in g sacculifer there was no significant change in the ratios analyses by electron microprobe revealed that mg ca of the inner chamber calcite in g tumida tests was much higher than that of the calcite crust keel whereas sr ca was only slightly elevated there were no consistent spatial differences in either mg ca or sr ca for g sacculifer tests dissolution in the oceans gives rise to the removal of the chamber calcite in g tumida about 30 of the total calcite leaving the keel calcite although g tumida is thought of as a dissolution resistant form the majority of mg ca and sr ca depletion and chamber loss occurs above the lysocline it is also possible that much of the mg enriched gametogenic calcite has been lost by dissolution from g sacculifer above 1600 m mg content has a significant effect on the dissolution susceptibility of planktonic foraminifera calculations show that the saturation horizon for mg rich parts of tests may be elevated by several hundred meters compared with normal calcite

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

sediment accretion and recent sea level rise in the solent southern england inferences from radiometric and geochemical studies abstract a detailed radionuclide and geochemical study has been carried out on recent sediments from the solent estuarine system southern england the vertical distributions of a series of radionuclides 210 pb 137 cs 238 pu 239 240 pu 241 am and 60 co have been examined which provide a measure of the rate of sediment accumulation in southern england estuaries the reliable use of radionuclides as indicators of sediment accumulation depends in part on their chemical immobility lack of redox migration 60 co in particular shows evidence for redox mobilization hence it is essential to use a number of chemically different or inert radionuclides to eliminate possible bias in calculated sediment accumulation rates while local intra estuary effects influence rates of sediment accumulation the main control of vertical saltmarsh growth over the solent area is a rise in mean sea level dating of saltmarsh cores indicates a 4 5 mm year 1 rise in relative sea level over the last 100 years in good agreement with tide gauge data comparison with data from the literature implies that a recent acceleration in sea level rise has occurred from 1 2 mmyear 1 to 4 5 5 mm year 1 possibly due to changes in tidal regime or an acceleration in crustal subsidence

recent salt marsh development and natural regeneration of reclaimed areas in the plentzia estuary n spain the distribution of benthic foraminifera a range of elements and 137cs and 210pb were studied in surface sediments and 0 5 m cores from the plentzia estuarine marshes northern spain to determine the recent development of these previously reclaimed coastal areas these marshes receive abundant calcium carbonate from regional rocks and this allows calcareous foraminifera to colonize all marsh subenvironments good preservation of the original foraminiferal assemblages in the buried sediments is also favoured by high regional background carbonate benthic foraminifera are shown to be sensitive to both elevation above mean sea level exposure and salinity results from the chemical analyses indicate moderate anthropogenic pollution in the estuary and maximum input seems to have occurred in the 1960s recent marsh foraminiferal assemblages are good analogues for the palaeoenvironmental interpretation of historical and holocene cores and the combined micropalaeontological geochemical approach is demonstrated to be successful for the identification of short term anthropogenic impacts on this coastal region

the seasonal cycle over the tropical pacific in coupled ocean atmosphere general circulation models abstract the seasonal cycle over the tropical pacific simulated by 11 coupled ocean atmosphere general circulation models gcms is examined each model consists of a high resolution ocean gcm of either the tropical pacific or near global means coupled to a moderate or high resolution atmospheric gcm without the use of flux correction the seasonal behavior of sea surface temperature sst and eastern pacific rainfall is presented for each model the results show that current state of the art coupled gcms share important successes and troublesome systematic errors all 11 models are able to simulate the mean zonal gradient in sst at the equator over the central pacific the simulated equatorial cold tongue generally tends to be too strong too narrow and extend too far west ssts are generally too warm in a broad region west of peru and in a band near 10 s this is accompanied in some models by a double intertropical convergence zone itcz straddling the equator over the eastern pacific and in others

heavy metal and arsenic distributions in sediments of the elba argentario basin southern tuscany italy arsenic chromium cobalt copper lead nickel vanadium and zinc distributions in surficial and core sediments of the elba argentario marine basin southern tuscany central western italy are reported analysis of such distributions compared with grain size and mineralogical data allowed the identification of areas showing trace element enrichments with respect to natural background these enrichments are moderate and essentially restricted to pb and zn only as shows a widespread though not high positive anomaly this general pattern is in good agreement with the minor industrialization affecting the basin s watershed an unexpected anomaly concerning co pb and as as well as fe and ti has been pointed out close to montecristo island this has been ascribed to illegal local dumping of chemical waste

an evaluation of benthic foraminiferal b ca and δ11b for deep ocean carbonate ion and ph reconstructions reliable reconstructions of deep ocean carbonate ion concentration co32 and ph are crucial to understand mechanisms responsible for the past atmospheric co2 variations observed in ice cores however it is challenging to reconstruct past deep water co32 and ph and literature results from different proxies conflict warranting careful investigations on possible reasons for the existing inconsistencies here we present the first down core b ca and 11b records measured in an epifaunal benthic foraminifer cibicidoides wuellerstorfi from the caribbean sea during the last 160 kyr the two proxies yield quantitatively comparable deep water co3 2 and ph results showing high values during glacials relative to inter glacials differences in co32 and ph are 35 mol kg and 0 15 respectively consistent with past ocean circulation changes in the caribbean sea our data provide convincing evidence that both proxies serve as faithful proxies to estimate deep ocean co32 and ph despite our incomplete understanding of boron incorporation into foraminiferal carbonates

precise multielemental ratios in small foraminiferal samples determined by sector field icp ms inductively coupled plasma mass spectrometry icp ms holds two main advantages over other techniques for the measurement of foraminiferal elemental ratios 1 numerous trace metals may be precisely and simultaneously measured and 2 smaller samples may theoretically be used methods are presented for the precise determination of mg ca sr ca cd ca zn ca li ca u ca mn ca and fe ca by sector field icp ms analytical precision is largely independent of sample size over the range of 5 to 125 g caco3 eliminating the need for narrow target dilutions long term 1 precisions are as follows mg ca 0 54 sr ca 0 57 cd ca 1 8 zn ca 3 2 li ca 0 88 u ca 1 9 mn ca 0 97 and fe ca 1 4 for mg ca actual foraminiferal samples appear to give reliable results below 10 g caco3 postcleaning mass

rare earth elements in early diagenetic foraminifer coatings pore water controls and potential palaeoceanographic applications abstract rare earth element ree distributions in the ocean bear the fingerprints of several key environmental processes including vertical particle organic carbon fluxes water column pore water oxygenation and ocean transports the use of fossil ree analyses in the service of palaeoceanography as redox water transport or nutrient cycling proxies has long been a tantalizing possibility here we demonstrate the application of a novel laser ablation microanalysis approach for the rapid and accurate measurement of the ree composition of early diagenetic coatings on fossil foraminifera by applying this new method to a range of core top and multi core samples we show that authigenic ree enrichments on planktonic foraminifer surfaces reefs reflect a primary seawater signature that becomes overprinted during sediment burial due to early diagenetic processes that control the flux of rees to pore fluids thus light rees lrees and eventually middle rees mrees are generally enriched in foraminifer coatings relative to seawater while ce anomalies ce ce recorded in surface sediments are typically more positive than local seawater values and are further eroded during burial with the onset of anoxic conditions in the sediment similar patterns have previously been observed in pore fluid measurements indeed we show that mn and fe concentrations measured in foraminifer coatings track the availability of these elements in pore water indicating that they are not associated with a secondary oxide phase we propose that these elements along with rees are instead adsorbed directly from pore fluids in contrast u in authigenic coatings tracks the removal of this element from solution under sub oxic conditions supporting the use of u ca in foraminifer coatings as a redox proxy although our results confirm a significant early diagenetic influence on reefs we also demonstrate the potential utility of ce enrichment relative to expected seawater values as a palaeo oxygenation proxy we support this proposal with down core measurements of u ca and ce enrichment spanning the last deglaciation in the sub antarctic atlantic as well as a global array of lgm measurements which are found to co vary with parallel estimates of radiocarbon ventilation age consistent with a widespread drop in oxygen suggesting an increase in the efficiency of the biological pump our results suggest that laser ablation reefs measurements may hold some promise for palaeoceanographic reconstruction in particular through a shift in emphasis away from the reconstruction of primary seawater signals to the analysis of diagenetic impacts that are sensitive to changing hydrographic conditions

how surface complexes impact boron isotope fractionation evidence from fe and mn oxides sorption experiments abstract although the ph dependence of boron isotope fractionation between solution and precipitating minerals has been widely used in earth sciences especially for reconstructing ancient seawater ph the mechanisms by which boron adsorbs on solids or coprecipitates in minerals are still poorly known here we have investigated boron isotopic fractionation during its adsorption on goethite feooh and birnessite k0 1mno2 2 0 9h2o as a function of solution ph at t 25 c and i 0 1 m maximum partition coefficients kd between adsorbed and aqueous boron equal to 39 and 34 for goethite and birnessite respectively are observed at ph 8 9 b adsorption at the surface of goethite induces its strong ph dependent isotopic fractionation ranging from 40 10b enrichment on goethite at ph 10 during adsorption on birnessite at acid and neutral ph boron isotopic fractionation is lower than during its sorption on goethite 15 decreases increases with increasing ph above ph 8 and reverses at ph 9 11b enrichment 23 at ph 10 8 is observed at birnessite surface based on combined infrared drift spectroscopic analysis and modeling of b speciation at oxides solution interfaces the observed isotopic fractionations can be rationalized by the formation of trigonal and tetrahedral boron inner sphere complexes on goethite surface and tetrahedral inner sphere and trigonal outer sphere and inner sphere complexes on birnessite surface b isotopic fractionation is strongly dependent on the structure of surface complexes formed the high steric strain induced by the formation of trigonal boron bidendate binuclear complexes at goethite surface leads to a much higher isotopic fractionation isotopically lighter sorbed boron than that following the formation of tetrahedral bidendate binuclear complexes conversely the formation at birnessite surface of trigonal complexes having almost the same isotopic composition than aqueous boric acid accounts for the heavier isotopic composition of birnessite than goethite boron both at acid and alkaline ph these results show that in nature 11b enrichment is expected in waters in equilibrium with iron or manganese oxides and that this enrichment is a function of ph that changes boron speciation in solution and at solid surfaces this is typically the case for soil solution in fe and mn rich environments and in seawater in addition the markedly different isotopic fractionation factor at the same ph of boron sorbed on goethite and birnessite at ph 8 2 is equal to 0 967 and 0 986 for goethite and birnessite respectively may be used to determine past ocean ph values without requiring knowledge of past isotopic composition

b ca in planktonic foraminifera as a proxy for surface seawater ph boron isotope systematics indicate that boron incorporation into foraminiferal caco3 is determined by the partition coefficient k d frac left rm b rm ca right rm caco3 left rm b left rm oh right 4 rm hco 3 right rm seawater and b oh 4 hco3 seawater providing in principle a method to estimate seawater ph and pco2 we have measured b ca ratios in globigerina bulloides and globorotalia inflata for a series of core tops from the north atlantic and the southern ocean and in globigerinoides ruber white from ocean drilling program odp site 668b on the sierra leone rise in the eastern equatorial atlantic b ca ratios in these species of planktonic foraminifera seem unaffected by dissolution on the seafloor k d shows a strong species specific dependence on calcification temperature which can be corrected for using the mg ca temperature proxy a preliminary study of g inflata from southern ocean sediment core chat 16k suggests that temperature corrected b ca was 30 higher during the last glacial correspondingly ph was 0 15 units higher and aqueous pco2 was 95 atm lower at this site at the last glacial maximum the covariation between reconstructed pco2 and the atmospheric pco2 from the vostok ice core demonstrates the feasibility of using b ca in planktonic foraminifera for reconstructing past variations in ph and pco2

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

benthic foraminiferal b ca ratios reflect deep water carbonate saturation state boron calcium ratios were measured in four benthic foraminiferal species three calcitic cibicidoides wuellerstorfi cibicidoides mundulus and uvigerina spp and one aragonitic hoeglundina elegans from 108 core top samples located globally comparison of coexisting species shows b ca of c wuellerstorfi c mundulus h elegans uvigerina spp suggestive of strong vital effects on benthic foraminiferal b ca a dissolution effect on benthic b ca is not observed core top data show large intra species variations 50 130 mol mol in b ca within a single species benthic foraminiferal b ca show a simple linear correlation with deep water co32 providing a proxy for past deep water co32 reconstructions empirical sensitivities of co32 on b ca have been established to be 1 14 0 048 and 0 69 0 072 mol mol per mol kg for c wuellerstorfi and c mundulus respectively the uncertainties associated with reconstructing bottom water co32 using b ca in c wuellerstorfi and c mundulus are about 10 mol kg a preliminary application shows that the last glacial maximum lgm b ca ratios were increased by 12 at 1 2 km and decreased by 12 at 3 5 4 0 km relative to holocene values in the north atlantic ocean this implies that the lgm co32 was higher by not vert similar 25 30 mol kg at intermediate depths and lower by not vert similar 20 mol kg in deeper waters consistent with glacial water mass reorganization in the north atlantic ocean inferred from other paleochemical proxies

on the annual cycle of the eastern equatorial pacific abstract although the sun crosses the equator twice a year the eastern equatorial pacific has a pronounced annual cycle in sea surface temperature and in both components of the surface winds for example this is in contrast to the indian ocean and western pacific where a semiannual oscillation of the zonal wind is the dominant signal on the equator calculations with a relatively simple coupled ocean atmosphere model indicate that the principal reason for this phenomenon is the marked asymmetry relative to the equator of the time averaged climatic conditions in the eastern tropical pacific the important asymmetries are in surface winds oceanic currents and sea surface temperature the time averaged winds and currents have northward components at the equator and the warmest waters are north of the equator because of those asymmetries seasonally varying solar radiation that is strictly antisymmetric relative to the equator can force a response that has a symmetric component the amplitude of th

a stability analysis of tropical ocean atmosphere interactions bridging measurements and theory for el nino abstract interactions between the tropical oceans and atmosphere permit a spectrum of natural modes of oscillation whose properties period intensity spatial structure and direction of propagation depend on the background climatic state i e the mean state this mean state can be described by parameters that include the following the time averaged intensity of the pacific trade winds the mean depth h of the thermocline and the temperature difference across the thermocline t a stability analysis by means of a simple coupled ocean atmosphere model indicates two distinct families of unstable modes one has long periods of several years involves sea surface temperature variations determined by vertical movements of the thermocline that are part of the adjustment of the ocean basin to the fluctuating winds requires a relatively deep thermocline and corresponds to the delayed oscillator the other family requires a shallow thermocline has short periods of a year or two has sea surface tempe

background levels of potentially toxic metals from soils of the pisa coastal plain tuscany italy as identified from sedimentological criteria identification of reliable background values of potentially toxic metals in sediments requires detailed integration of geochemical data with accurate sedimentological studies through analysis of 60 soil samples from the pisa coastal plain this study shows to what extent sediment provenance and facies characteristics may influence the natural distribution of potentially toxic metals cr ni cu zn pb within alluvial and coastal sediments metals supplied to the alluvial plain are mostly concentrated within the finest sediment fraction floodplain clays while coarser crevasse and overbank deposits exhibit invariably lower metal contents beach ridge sands display the lowest metal concentrations transport of ophiolitic detritus by the longshore drift may account for locally high cr concentrations within beach deposits geochemical fingerprinting of individual facies associations in terms of natural metal contents results in the construction of a geologically based geochemical map this map offers a more reliable depiction of spatial distribution of background levels than interpolation techniques based uniquely upon statistical methods matching background values against metal concentrations from topsoil samples leads to the reliable assessment of the pollution status of pisa coastal plain metal contents exceeding the threshold values designated for contaminated areas cr simply reflect catchment geology and are not the product of artificial contamination on the other hand anthropogenic disturbance may be detected even where metal contents pb cu lie below the threshold values the use of sedimentological criteria is presented here as a pragmatic tool to enhance predictability of natural metal contents in sediments with obvious positive feedbacks for legislative purposes and environmental protection

temperature control on the incorporation of magnesium strontium fluorine and cadmium into benthic foraminiferal shells from little bahama bank prospects for thermocline paleoceanography surface sediments from little bahama bank lbb intersecting the subtropical thermocline were used to assess the influence of temperature on the incorporation of mg sr f and cd into shells of benthic foraminifera samples were obtained from twelve cores along the southern slope of lbb covering a temperature range of 18 4 5 c between 301 and 1585 m we studied the composition of ten calcitic and one aragonitic species which are often used in paleochemical reconstructions mg ca ratios decrease with increasing water depth in all benthic species both with calcitic and aragonitic mineralogy showing a strong correlation with water temperature similar decrease is seen in sr ca but with no correlation with temperature none of the benthic species studied here exhibits a depth or temperature related change in f ca similar trends are observed when using an ocean wide dataset which includes shallow and deep core tops 300 5000 m we suggest that temperature is the primary control on the mg content of benthic foraminifera based on inorganic precipitation experiments and thermodynamic considerations presented here a 30 40 decrease in the mg distribution coefficient in calcite may be expected as a result of a temperature change from 25 c to 5 c which is about half the observed change in lbb a calibration curve applied to c pachyderma data from core tops along the slope of little bahama bank suggests that water temperature may be inferred from mg ca ratios with an uncertainty of about 0 8 c therefore the mg content of benthic foraminifera may provide a new independent temperature proxy for studying shallow waters paleoceanography the linear decrease in sr ca with increasing depth is not correlated with temperature the trend is constant from the ocean surface down to 5 km suggesting that pressure related effects on the calcification process are a more likely explanation than post depositional dissolution mg ca ratios in aragonitic shells of h elegans covary with temperature in accord with recent observations from corals in contrast the sr and f chemistry of h elegans is very different than that of corals and inorganically precipitated aragonites the disparities between the elemental composition of biogenic and inorganic phases and the large intergeneric and interspecific differences observed both in planktonic and benthic foraminifera implicate temperature related physiological processes in regulating the coprecipitation of elements in foraminiferal shells our work demonstrates that cd ca ratios of shallow calcitic species reflect the vertical distribution of nutrients no significant influence of temperature on the partitioning of cd into the shells was found our data extend the previous deep water calibration boyle 1992 thereby allowing for the reconstruction of the nutrient chemistry of shallow thermocline waters

on the genesis of the equatorial annual cycle abstract a linear theory is proposed that can explain both the period and the westward propagation of the equatorial annual cycles in the sst and zonal wind a coupled model linearized about a mean state of the air sea system is used this model allows the surface winds to directly change the sst through surface evaporation and vertical mixing in contrast to the formulation of the conventional air sea coupling models that emphasize the effects of winds on ocean dynamics it is demonstrated that the characteristics of the equatorial seasonal cycle including its period phase and amplitude are determined to a large extent by the mean state of the air sea coupling system the meridional wind which is specified here is the most important forcing for the annual cycle in sst suggesting that the equatorial annual cycle is the response to an annual solar forcing in the off equatorial regions

the effects of diagenesis on lithium isotope ratios of shallow marine carbonates in this study we present new data on the 7li values and li ca mg ratios of carbonate cores from the great bahama bank clino unda a deep water core off of the bank top odp leg 166 site 1007 and the coralline key largo limestone we use these samples to evaluate the influence of meteoric diagenesis marine burial diagenesis and dolomitization on the li isotope system in carbonates we find that recrystallization of aragonite to low mg calcite in the presence of meteoric fluids results in a systematic decrease of the li ca mg ratio in clino unda and key largo samples due to the lower li ca mg ratio in meteoric fluids compared to seawater for li isotopes we observe that the 7li of meteorically altered low mg calcite is 22 0 3 8 n 28 1 which is coincidentally similar to the original aragonite rich sediments 22 1 in the bahamas 18 1 in key largo but with a larger variability from 15 to 27 we interpret these features as reflecting the overprinting of primary li during meteoric alteration with a highly variable isotope signature that may be controlled by a combination of local porewater and or global climatic conditions in either case meteoric diagenesis produces isotopic signatures that are unrelated to seawater composition in contrast marine burial diagenesis and dolomitization of clino and unda sediments under fluid buffered conditions result in li isotope composition that is similar 30 2 1 5 n 36 1 to modern seawater 31 for site 1007 the 7li values range between 23 permil and 31 permil we interpret this range as reflecting a combination of varying diagenesis style fluid to sediment buffered and varying contribution of calcite derived from pelagic sediments with distinct isotopic composition due to primary mineralogy altogether our results show that diagenesis does not invalidate the use of bulk carbonates for deriving li isotope paleo records but the reliability of past carbonates as recorders of seawater 7li values will depend on carefully characterizing their diagenetic history

determination of low b ca ratios in carbonates using icp qqq the very low b ca ratios characteristic of some natural biogenic carbonates are of interest for research in ocean acidification but represent an analytical challenge we describe a method using a novel instrument configuration icp qqq for which we are not aware of any previously published geological applications and for coccoliths a sample type unique in its low b content and organic phases detection limits as low as 0 41 mol mol were achieved isobaric interferences out of the reach even for sf icp ms can be solved using this instrument which permits the safe measurement of the lowest abundance ca isotope 46ca this allows maximizing the b concentration measured matrix concentration up to 800 ppm ca while maintaining both b and ca signals in counting mode more significantly for low b samples the icp qqq is also able to overcome the interference of the ubiquitous 12c tail on the 11b mass which otherwise leads to significant overestimates at very low b concentrations this could be a reason for the significantly lower b ca ratios observed for the low b content interlaboratory calibration standards carrara and oka while matching for the high b content standards was good finally results obtained in the analysis of coccoliths grown in laboratory culture seems to corroborate that sims analysis of the samples mounted in indium leads also to b ca overestimates due to porosity effects as previously observed using la icp ms this approach also permits the interference free measurement of p ca and s ca ratios which could be used as indicators of the complete removal of the organic matter from the samples

heavy metal origin and concentration in the sediments of the pointe a pitre bay guadeloupe lesser antilles sewage discharge chiefly waste waters into the pointe a pitre bay originates from the neighboring developing town 60 000 inhabitants a sampling campaign carried out in march 1984 permitted the assessment of both water and sediment quality in the bay as well as the evaulation of heavy metal contents industrial pollution appears insignificant whilst urban pollution dominates heavy metal contents lead pb zinc zn copper cu are high in the sediments of the inner end of the bay and eastern bank parallel to the urban agglomeration this anthropogenic origin is accounted for by comparison of heavy metal contents with those prevailing in the terrestrial environment

mg ca temperature calibration of polar benthic foraminifera species for reconstruction of bottom water temperatures on the antarctic shelf benthic foraminifera mg ca is a well established bottom water temperature bwt proxy used in paleoclimate studies the relationship between mg ca and bwt for numerous species has been determined using core top and culturing studies however the scarcity of calcareous microfossils in antarctic shelf sediments and poorly defined calibrations at low temperatures has limited the use of the foraminiferal mg ca paleothermometer in ice proximal antarctic sediments here we present paired ocean temperature and modern benthic foraminifera mg ca data for three species trifarina angulosa bulimina aculeata and globocassidulina subglobosa but with a particular focus on trifarina angulosa the core top data from several antarctic sectors span a bwt range of 1 7 to 1 2 c and constrain the relationship between mg ca and cold temperatures we compare our results to published lower latitude core top data for species in the same or related genera and in the case of trifarina angulosa produce a regional calibration the resulting regional equation for trifarina angulosa is temperature c mg ca 1 14 0 035 0 069 0 033 addition of our trifarina angulosa data to the previously published uvigerina spp dataset provides and alternative global calibration although some data points appear to be offset from this relationship and are discussed mg temperature relationships for bulimina aculeata and globocassidulina subglobosa are also combined with previously published data to produce calibration equations of temperature c mg ca 1 04 0 07 0 099 0 01 and temperature c mg ca 0 99 0 03 0 087 0 01 respectively these refined calibrations highlight the potential utility of benthic foraminifera mg ca paleothermometry for reconstructing past bwt in antarctic margin settings although further work is required before they are routinely used