profiles of trace elements and stable isotopes derived from giant long lived tridacna gigas bivalves potential applications in paleoclimate studies this study investigates the environmental and biological controls on trace element partitioning and stable isotope composition of modern giant long lived bivalves tridacna gigas with the aim to use these archives for paleoclimatic reconstructions firstly the intra shell variability is studied by measuring time equivalent profiles in the different shell layers characterised by different growth rates secondly the inter site variability is studied by comparing profiles derived from three modern specimens collected in sites across the indo pacific region characterised by different ranges of temperature and productivity these results show that 18o profiles are highly reproducible across the shell regardless of significantly different growth rates shell 18o is primarily controlled by water 18o and temperature comparison of intra shell mg ca profiles shows a clear and systematic partitioning where inner layer mg ca values are a least 2 3 times higher than outer layer and hinge areas inner layer mg ca shows seasonal oscillations but superimposed on an ontogenetic trend with increasing values and increasing amplitude mg ca oscillations with age the sr ca profiles do not show clear reproducible seasonal trends in the different shell zones it is concluded that mg ca and sr ca profiles appear to reflect a combination of biological and environmental controls that will need to be disentangled before using these proxies in paleoclimatic studies finally intra shell ba ca profiles are reproducible in great detail for all modern specimens studied inter site comparison shows that the amplitude and the timing of the ba ca peaks appear to reflect the timing and the amplitude of the chlorophyll peaks associated with phytoplankton blooms at each locality making this tracer a potential paleoproductivity indicator

assessing the reliability of magnesium in foraminiferal calcite as a proxy for water mass temperatures though many studies on the mg contents in the calcitic tests of foraminifers exist the processes controlling its uptake are still a matter of debate laboratory cultures offer an excellent opportunity to reveal these mechanisms the mg concentrations within single chambers of the planktic foraminifer globigerinoides sacculifer brady maintained under controlled laboratory conditions were measured 1 at variable temperatures 19 5 29 5 c and constant salinity and 2 at variable salinity 22 45 and constant temperature the experimental results suggest that under natural conditions temperature is the leading mechanism controlling the mg ca ratio temperature and magnesium are related proportionally a temperature increase of ca 10 c gives rise to an increase of the magnesium concentrations of ca 130 drastic unnatural salinity changes dominate the effects of temperature a 110 change in the mg ca ratio was observed when salinity was elevated or reduced by more than ca 10 specimens which underwent gametogenesis reveal significantly higher mg concentrations than specimens that did not release gametes partition coefficients for mg in foraminiferal calcite are orders of magnitude lower than values from inorganically precipitated calcite when comparing observed mg ca ratios of foraminiferal tests with predicted mg ca ratios calculated according to empirical equations it becomes evident that foraminiferal tests are undersaturated with respect to mg for the water temperature they have experienced apparently foraminifers are capable of controlling their mg concentration the physiological processes presumably responsible for such depressed mg ca ratios appear to be temperature controlled as deduced from the close relationship of the observed mg ca ratios and water temperature this study demonstrates that variations in temperature and salinity are definitely reflected in the mg content of foraminiferal tests magnesium may thus serve as a paleo proxy for past surface water temperatures as long as postdepositional changes and salinity variations are of subordinate importance or can be excluded

trace and minor element records in aragonitic bivalve shells as environmental proxies abstract investigation of the geochemical composition of bivalve shells can provide information on changes in the marine environment occurring during the lifespan of an organism three species locally abundant in the adriatic sea were chosen in this study namely glycymeris pilosa callista chione and venus verrucosa of these g pilosa has the longest lifespan exceeding 50 years and therefore presents a potential archive of decadal climate variability the other two species c chione and v verrucosa are commercially important samples were collected alive by scuba diving in the north adriatic sea near barbariga istria major growth increments in these shells form on an annual basis and are clearly visible in shell cross sections enabling correct temporal positioning of geochemical data obtained from different shell parts in this study we applied laser ablation inductively coupled plasma mass spectrometry la icp ms in line scan mode to determine the trace and minor element composition along the major growth axis in the hinge area of the shells objectives of this study were to compare signals within and between species and to relate results to available environmental parameters high resolution time series of na cashell mg cashell and sr cashell display characteristic cyclic variations na cashell minima and mg cashell and sr cashell maxima occur near shell annual growth lines in all three studied species results indicate that seawater temperature is not a main driver for incorporation of these elements ba cashell data vary between years and species and have noncyclic sharp peaks callista chione and v verrucosa specimens show higher peaks and background ba cashell values than g pilosa most pronounced peaks in ba cashell occurred at the beginning of the growing season corresponding to the end of year 2011 and beginning of year 2012 and coincided with unusual dense water formation and subsequent changes in the plankton communities in the adriatic sea implications of our study suggest that synchronous peaks in studied specimens are caused by external forcing which could occur on larger regional scales encouraging future studies covering wider area in the adriatic sea and other parts of the mediterranean

a history of jokulhlaups from strandline lake alaska u s a les vidanges brutales du strandline lake se produisent tous les 1 a 5 ans la vidange est precedee par le developpement d un golfe de velage dans le lobe du triumvirate glacier qui barre le lac et par le remplissage de petits lacs sur le glacier on analyse le mecanisme a partir de cartes photogrammetriques dressees avant et apres la vidange

on the strength of oceanic fracture zones and their influence on the intraplate stress field we use the locations and source mechanisms of oceanic intraplate earthquakes to test the hypothesis that the strength of oceanic fracture zones is less than that of normal oceanic lithosphere if fracture zones are weaker than the surrounding lithosphere they should be sites of concentrated intraplate seismicity and the lithospheric stress field should be perturbed in their vicinity the 77 earthquakes selected for the study have well determined focal mechanisms and epicenters in regions where fracture zones are well mapped we have searched for dependence of faulting style fault orientation or principal stress direction on the distance from the nearest fracture zone if fracture zones were generally weaker than the surrounding lithosphere one of the principal horizontal stresses would be oriented nearly perpendicular to the fracture zone we find no evidence that principal stresses near fracture zones are oriented preferentially in this manner there is a slight tendency for earthquakes to occur near fracture zones and patterns of fault orientation and sense of slip support the view that differential cooling and horizontal contraction on fracture zones may contribute seismogenic stress these patterns are not demonstrable at high significance however if oceanic transform fault zones are weak relative to the surrounding lithosphere these results suggest that the strength of the fracture zones increases within a few million years after cessation of transform motion to levels comparable with that of normal oceanic lithosphere

crystal fabrics and element impurities sr ca mg ca and ba ca in shells of arctica islandica implications for paleoclimate reconstructions sr ca mg ca and ba ca values are heterogeneously distributed in shells of arctica islandica these patterns are largely associated with crystal fabrics size habit and orientation of crystals or the processes controlling them the outer sublayer of the outer shell layer oosl homogenous and irregular simple prismatic crystal fabrics contained element ca values up to 62 higher than the inner sublayer iosl crossed acicular crossed lamellar fine crossed lamellar and irregular simple prismatic crystal fabrics a gradual decrease in sr ca and mg ca values was observed from the outer portions of the oosl toward the oosl iosl transition zone this chemical shift was accompanied by a gradual transition from homogenous crystal fabrics into crossed lamellar acicular crystal fabrics near annual growth lines irregular simple prisms i e during periods of slow growth sr and mg seemed to be deposited in equilibrium with the ambient environment because the sr ca and mg ca values approached values typical for seawater during the remainder of the growing season sr ca and mg ca remained far below values expected for thermodynamic equilibrium ba ca peaks however occurred erratically at different times of the year without any noticeable changes in crystal fabrics likely the environmental information contained in these peaks was less severely filtered by vital effects than in sr and mg the findings of the present study can help to develop new techniques with which extract environmental signals from the metal to calcium ratios of bivalve shells

micro x ray fluorescence μxrf line scanning on cretaceous rudist bivalves a new method for reproducible trace element profiles in bivalve calcite the reconstruction of palaeoclimate on a sub annual scale requires the measurement of chemical proxies in fossil material at a high spatial resolution while various methods for trace element analysis on the micrometre scale are available they are usually destructive to the sample or not widely accessible this study evaluates the performance of a table top micro x ray fluorescence scanner in obtaining reproducible trace element profiles on bivalve calcite standard calibration and repeatability tests demonstrate the robustness of results obtained with this new generation micro x ray fluorescence device that uses a comparatively high excitation energy of 30 w results show that elemental abundances measured using this fast readily accessible and non destructive analytical setup are reproducible on the g g level and therefore suitable for the analysis of the abundance of commonly studied elements in bivalve calcite for example sr mn and fe spectra obtained in this study show considerable improvement in terms of signal to noise ratio compared to earlier table top xrf studies reliability of the measurements is tested using a conservative detection and quantification limit count rates of ca are used to check for point measurements disturbed by irregularities on the sample surface furthermore the method allows semi quantitative two dimensional element mapping which is a convenient tool for the detection of diagenetic alteration in fossil samples the method reveals records of sr ca fe ca and mn ca ratios in a late campanian vaccinites vesiculosus shell with sr ca ratios showing a trend opposite to mn ca and fe ca resulting trace element records are discussed in terms of seasonal cyclicity in the late cretaceous and diagenetic alteration of the fossil shell this article is protected by copyright all rights reserved

trace element heterogeneity along isochronous growth layers in bivalve shell consequences for environmental reconstruction to precisely reconstruct environmental changes from high resolution bivalve shell geochemistry the shell layers must represent environmental conditions at the time of deposition therefore calcium carbonate along growth lines that formed at the same time should show the same geochemical signature we test this assumption by evaluating the geochemical spatial homogeneity along growth layers i e shell secreted at a given time on shell cross sections of modern shells of the bivalve protothaca thaca for ontogenitically young and old specimens analyses were carried out using laser ablation icp ms and solution nebulization icp ms scanning electron microscope images showed signs of early diagenesis of old shell sections close to the umbo compared with recent close to the ventral margin the spatial distribution of sr ca mg ca and ba ca along growth layers differed consistently between old and recent shell sections elemental distribution at the ventral margin of young specimens was similar for the two specimens analyzed and similar to the element distribution in the older specimens at a similar ontogenic stage closer to the umbo if a balancing of the shell composition with the surrounding seawater between the old and recent part of the shell supported by diagenesis cannot be excluded we assume that trace element incorporation process at a given time varied with the age of the specimen in connection with changes of mantle characteristics whereas ba ca and sr ca were almost constant for shell secreted at a given time close to the current ventral margin all individuals showed significant mg ca heterogeneities with reproducible patterns we assumed that this would be due to a zonation of the outer epithelium of the mantle that would favor or inhibit the transport of mg into the extrapallial fluid and subsequently into the shell time series obtained crossing successive growth layers using laser ablation icp ms and solution nebulization icp ms on a same shell growth section were similar for sr ca and ba ca ratios and not for mg ca which reflected both the different spatial resolutions of the analytical techniques and the heterogeneous distribution of mg ca in the p thaca shells sr and ba seemed to be most promising as potential high resolution environmental proxies our study showed that the location of high resolution analyses points in shell cross section must be i precisely defined and ii consistently followed along the shell section to provide accurate environmental records i e without bias related to shell layer heterogeneities

chemical labelling of oyster shells used for time calibrated high resolution mg ca ratios a tool for estimation of past seasonal temperature variations abstract the geochemical compositions of biogenic carbonates are increasingly used for palaeoenvironmental reconstructions the skeletal 18o temperature relationship is dependent on water salinity so many recent studies have focused on the mg ca and sr ca ratios because those ratios in water do not change significantly on short time scales thus those elemental ratios are considered to be good palaeotemperature proxies in many biominerals although their use remains ambiguous in bivalve shells here we present the high resolution mg ca ratios of two modern species of juvenile and adult oyster shells crassostrea gigas and ostrea edulis these specimens were grown in controlled conditions for over one year in two different locations in situ monthly mn marking of the shells has been used for day calibration the daily mg ca ratios in the shell have been measured with an electron microprobe the high frequency mg ca variation of all specimens displays good synchronism with lunar cycles suggesting that tides strongly influence the incorporation of mg ca into the shells highly significant correlation coefficients 0 70

early jurassic climatic trends in the south tethyan margin abstract the early jurassic period was characterized by extreme environmental changes as reflected by major global carbon isotope anomalies and abrupt changes in oxygen isotope and elemental records of marine organisms available data suggest an overall warm early jurassic climate interrupted by periods of severe cooling with a climatic optimum during the early toarcian available geochemical studies however have mainly focused on the northern margin of the tethys ocean so that the palaeogeographic extent of these environmental perturbations latitudinal palaeotemperature gradients and climate belt boundaries remain poorly constrained here we report the first stable isotope records of brachiopod shells 13c and 18o values from the upper sinemurian middle toarcian interval in the southern margin of the tethys ocean northwest algeria these data were used to better constrain the palaeoenvironmental evolution of the north gondwana margin during the early jurassic which likely played an important role on supra regional climate the diagenetic history of the analysed brachiopod shells was monitored using scanning electron microscopy and elemental manganese and strontium compositions the brachiopod 13c and 18o data show very similar trends as those reported for various tethyan regions and record negative carbon and oxygen isotope excursions near the sinemurian pliensbachian and pliensbachian toarcian transitions and during the toarcian oceanic anoxic event t oae despite these similarities the carbon and oxygen isotope records are systematically offset towards more positive 13c values average 0 5 and more negative 18o values 1 0 compared to those obtained from sites of higher palaeolatitudes in the northern tethyan margin these offsets suggest a spatial heterogeneity in the stable isotope composition of dissolved inorganic carbon in the early jurassic ocean and a marked latitudinal temperature gradient between the southern and northern margins of the tethys

oxygen isotope records of the australian flat oyster ostrea angasi as a potential temperature archive abstract the response of the oxygen isotope ratio 18o in shells of the australian native flat oyster ostrea angasi to changes in water temperature has been assessed using growth experiments conducted for one year at two locations on the east coast of australia the analysed 18o of the oyster shells 18oshell closely follows the predicted oyster shell 18o constructed from measured 18o in the water 18owater and water temperature influxes of freshwater that occur in the estuarine habitats of o angasi can modify the 18owater and consequently 18oshell salinity fluctuations can also cause interruptions to shell growth in this species this can cause overestimated temperatures in o angasi 18oshell temperature reconstructions a 18oshell temperature calibration was established for o angasi yielding the relationship t c 13 97 3 57 18oshell 18owater 0 17 18oshell 18owater 2 n 79 r2 0 79 which within the experimental uncertainties of the data is similar to other published biogenic carbonate paleotemperature equations

a key to the past element ratios as environmental proxies in two arctic bivalves 2016 elsevier b v understanding rapid climate change in the arctic and its ecosystem implications requires more information on the environment at temporal resolutions and time periods not available from instrumental records such information can be acquired through geochemical proxy records but sub annual records are rare we analyzed shell material of bivalve mollusks serripes groenlandicus and ciliatocardium ciliatum placed on oceanographic moorings for one year in two arctic fjords to assess the potential use of shell elemental ratios as environmental proxies li ca mg ca li mg li sr mn ca sr ca mo ca and ba ca were determined using laser ablation inductively coupled plasma mass spectrometry combining data from moorings with previously derived sub annual shell growth models allowed us to relate the elemental ratio patterns to oceanographic parameters temperature salinity and fluorescence shell ba ca profiles were characterized by abrupt peaks occurring 11 to 81 days after the phytoplankton bloom as indicated by an index of seawater fluorescence li ca and mg ca values exhibited significant logarithmic relationships with shell growth rate indicated by marginal r2 values of 0 43 and 0 30 respectively these ratios were also linearly related to temperature with marginal r2 values of 0 15 and 0 17 respectively mn ca and sr ca ratios exhibited variability among individuals and their temporal pattern was likely controlled by several unidentified factors mo ca patterns within the shells did not demonstrate correlations with any of the oceanographic parameters our results reflect complex relationships between elemental ratios and bivalve metabolism methodological limitations as well as contemporaneous environmental processes suggesting that none of the studied elemental ratios can be used as unequivocal proxies of seawater temperature salinity paleoproductivity or shell growth rate despite this ba ca and li ca can be used as sub annual temporal anchors in further studies because the variability of these elements was synchronized in each fjord

seasonal temperature salinity changes and thermocline development in the mid atlantic bight as recorded by the isotopic composition of bivalves stable isotope records across annual growth increments in specimens of the surf clam spisula solidissima from the mid atlantic bight shelf from 10 m and 45 m depths reflect the changes in temperature and nutrient concentrations on the shelf over the year the 18 o and 13 c records from clams at the two depths record well mixed conditions in the water column during the winter months and the development of a thermocline during the summer spring high productivity and a transient salinity excursion in surface waters are also recorded reconstructing the paleoceanography of late cenozoic temperate continental shelves may be possible using stable isotope records from fossil spisula solidissima and other bivalves

element ca c and o isotope ratios in modern brachiopods species specific signals of biomineralization fossil brachiopods are of major importance for the reconstruction of palaeoenvironmental conditions particularly of the paleozoic in order to better understand signals of ancient shell materials modern analogue studies have to be conducted here we present c and o isotope data in conjunction with mg ca sr ca mn ca and fe ca data for nine modern rhynchonellid and terebratulid brachiopod species from tropical to intermediate latitudes and shallow to very deep marine settings c and o isotope signals of most species suggest formation of secondary shell layers near or in isotopic equilibrium with ambient seawater some species especially in the suborder terebratellidina show partly distinct disequilibrium signals suggesting some degree of phylogenetic control on the expression of vital effects mn ca and fe ca ratios measured in the modern species form a baseline to assess fossil preservation but also yield environmental information mg ca and sr ca ratios follow previously observed patterns with all studied brachiopod species comprising low mg calcite strong covariation of sr ca ratios with mg ca ratios is only observed in rhynchonellids and possibly one terebratulid species potentially linking the incorporation behaviour of alkaline earth metals to phylogeny sr ca show a strong negative correlation with 13c values in terebratellidinid species which exhibit major isotopic disequilibrium and also combined data from three localities for which two species were studied indicate such a negative relation the observed covariation of sr ca ratios with 13c values may therefore become a useful tool to detect 13c disequilibrium and to robustly estimate 13c values of ambient dic in deep time

quaternary deep sea temperature histories derived from benthic foraminiferal mg ca abstract we have generated benthic foraminiferal mg ca records from eastern tropical atlantic core m16772 3 9 km and eastern tropical pacific core tr163 31p 3 2 km to assess the potential for using benthic mg paleothermometry to reconstruct quaternary bottom water temperature histories variations in mg ca records from both the atlantic and pacific show a significant correlation with climatic oscillations of the last 330 kyr shell mg ca peaks during interglacial episodes with marine isotope stage mis 5e mg ca nearly matching holocene values in both cores lower mg ca values occur during glacial intervals to estimate temperatures from downcore mg ca we have augmented the published cibicidoides sp mg ca temperature dataset rosenthal et al geochim cosmochim acta 61 1997 3633 3643 with new data to include the temperature range of deep waters applying the 10 9 change in mg ca per c defined by the expanded calibration to the deep atlantic data implies glacial interglacial shifts in deep water temperature of 2 4 c over the last 300 kyr temperature estimates are comparable to deep atlantic temperature changes proposed by labeyrie et al nature 327 1987 477 482 there is greater uncertainty in deriving temperatures from the tropical pacific core due to a limited uvigerina spp core top calibration set however glacial interglacial temperature oscillations appear to be on the order of 2 3 c in addition core tr163 31p records clear millennial scale mg ca and 18 o oscillations in mis 3 corresponding to temperature fluctuations of 0 5 c additional calibration studies are needed to address potential secondary effects on mg ca

calibrating the element composition of donax deltoides shells as a palaeo salinity proxy abstract bivalve shell chemistries provide valuable insights into past environments if relationships between shell chemistry and environmental conditions are known this study assessed the suitability of goolwa cockle donax deltoides shell element composition as an environmental proxy for southern australia a region lacking high resolution environmental records cockles were collected along an environmental gradient and the element composition of corresponding water and shell samples were quantified using a combination of icp aes and icp ms for water samples and la icp ms for shells of the elements analysed ba ca li ca and mg ca in shells reflected ambient water chemistries shell ba ca concentrations showed a significant negative relationship with recorded salinities and a positive non significant trend was observed between mg ca and water temperature further assessment of environmental and biological controls on element incorporation are required however ba ca in d deltoides shells appears a suitable palaeo salinity tool and has the potential to provide an easily accessible and valuable proxy to gain insights into past environmental conditions over extensive time scales

mississippian paleocean chemistry from biotic and abiotic carbonate muleshoe mound lake valley formation new mexico u s a abstract it has been proposed that phanerozoic variation in the mg ca ratio of seawater has resulted in variation in the primary mineralogies of shallow water carbonates between aragonite and calcite dominated seas to test this hypothesis this study estimates the mississippian oceanic mg ca and sr ca ratios from the composition of marine carbonate cements and crinoidal carbonate both of which have been suggested to faithfully record seawater chemistry the early mississippian tournaisian visean muleshoe mound lake valley fm alamogordo nm u s a lends itself well to this endeavor because it contains abundant crinoids and marine carbonate cement stable isotope and elemental analyses as well as cathodoluminescence characteristics elucidate the diagenetic history of the bioherm and identify the least diagenetically altered materials for reconstruction of paleoseawater chemistry isotopic analyses document two diagenetic trends one meteoric and one burial diverging from values similar to literature estimates of mississippian marine calcite 1 5 18o 4 5 13c the burial diagenetic trend follows from this origin to more negative oxygen values 7 18o 3 13c the meteoric diagenetic trend is defined by a meteoric calcite line at 3 18o similarity of non luminescent marine cement and non luminescent crinoid isotopic and elemental compositions suggests that crinoidal carbonate was completely replaced by cement in the marine environment average elemental ratios for least altered marine cements are mg ca 11 mmol mol sr ca 0 2 mmol mol mn ca 0 2 mmol mol and fe ca 0 4 mmol mol early mississippian seawater is estimated to have had a mg ca ratio of 0 2 0 3 mol mol this mg ca ratio is compatible with the early mississippian being an interval of calcite sea conditions and compares well with the devonian estimate from marine cements 0 5 though it is 5 10 times lower than estimates from mass balance modeling the sr ca for early mississippian seawater was between 0 5 and 0 9 mmol mol which is much lower than previous estimates of 6 mmol mol from brachiopod calcite and argues for the development of a sr sink aragonite in the latest devonian to earliest mississippian

environmental controls on the stable isotopic composition of mercenaria mercenaria potential application to paleoenvironmental studies 1 we have investigated the environmental controls of seasonally resolved records of oxygen and carbon isotopes of modern mercenaria mercenaria bivalves collected live from five coastal sites along the east coast of north america seasonal profiles of 18o and 13c obtained by subsampling the incremental growth layers of aragonite were compared with in situ historical records of temperature and salinity we show that m mercenaria 18o profiles track accurately the seasonal variations of water temperature and that variations in growth rates do not affect the shell 18o values growth rates are strongly reduced or interrupted below water temperatures ranging from 8 to 10 c implying that only bivalves sampled in tropical areas track the full amplitude of seasonal variations although further measurements of water 18o and a better understanding of seasonal variations of the water 18o salinity relationships are necessary mercenaria mercenaria bivalves appear to precipitate their shell close to isotopic equilibrium whereas the amplitude of the seasonal profiles of 18o reflects variations in water temperature the annual average 18o decreases with latitude reflecting the trend of rainfall and riverwater 18o with latitude over the northern american continent

a high resolution study of trace elements and stable isotopes in oyster shells to estimate central asian middle eocene seasonality modern asian climate is characterized by strong seasonality caused by the duality between monsoon dominated conditions in southeastern asia and semi arid to arid conditions in central asia eocene high resolution proxy records which enable the reconstruction of the onset and magnitude of changes in seasonality are lacking to understand in details how and when this climatic turnover pattern occurred here we propose an original method to estimate inter and intra annual variabilities in seawater temperature and salinity recorded by carbonate shell growth increments of the fossil oyster sokolowia buhsii grewingk collected from late lutetian marine strata of the proto paratethys in the southwestern tarim basin western china elemental ratio mg ca mn ca and carbonate stable isotope composition 18o were determined perpendicular to the growth lines of foliated calcite accumulated in the ligamental area during the oyster s lifetime we use temperature dependant mg incorporation to estimate seasonal temperature contrast in the past results suggest a warm annual average temperature 27 28 c with large offset between summer and winter temperatures until t 19 c combining these temperature estimates with stable oxygen isotope analyses from the same growth increments we deconvolve seawater 18osw as a proxy for salinity this suggests an average annual salinity about 34 35 increasing strongly during summer months and decreasing in winter based on these data we conclude that during the middle eocene central asian climate was characterized by a strong intra seasonal variability in both temperature and salinity although the subtidal setting might have contributed to the strong seasonal offsets this still suggests that semi arid to arid conditions prevailed during summer whereas winter was characterized by enhanced rainfall these results are consistent with previous regional palaeoenvironmental data and climate modelling experiments they thus attest for the reliability of the method developed here as a seasonal palaeoclimatic indicator

an integrated carbon and oxygen isotope approach to reconstructing past environmental variability in the northeast atlantic ocean abstract the combined influence of temperature and the isotopic composition of the seawater 18ow often precludes the use of oxygen isotope 18o records derived from marine carbonates to reconstruct absolute seawater temperatures without the application of an independent 18ow proxy here we investigate the application of carbon isotope records 13cshell derived from the long lived marine bivalve glycymeris glycymeris as a proxy for 18ow variability our analyses indicate g glycymeris 13cshell data derived from growth increments 20 years of age contain strong ontogenetic trends 0 013 yr 1 r 0 98 p

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

tropical atlantic seasonal dynamics in the early middle eocene from stable oxygen and carbon isotope profiles of mollusk shells there are disagreements whether the tropical sea surface temperature during the warm early to early middle eocene was equal to the present temperature or significantly lower in order to determine the sea surface temperature of the eastern tropical atlantic in the early middle eocene we have established 18o and 13c profiles along the transect of growth of excellently preserved shells of turritella gastropods and a macoma bivalve from tropical west africa this method makes possible a distinction between the winter and the summer temperature the 18o and 13c data indicate sea surface temperatures of 29 31 c which declined to 23 25 c during seasonal upwelling these conditions are similar to those of today and suggest that significant seasonal dynamics prevailed in the early middle eocene tropics the new data further contradict that the tropics cooled during the generally warm early to early middle eocene as inferred in studies on foraminifera 18o

environmental and physiological controls on daily trace element incorporation in tridacna crocea from combined laboratory culturing and ultra high resolution la icp ms analysis abstract recent advances in spatially resolved in situ geochemical analysis enabled recognizing daily variability in b mg sr and ba within bivalve shells of the genus tridacna e g sano et al 2012 warter and muller 2017 however the causes for such daily chemical variations are not fully understood we carried out laboratory culture experiments to investigate the effect of varying temperatures and light levels on organism physiology and shell geochemistry of the giant clam tridacna crocea at daily time resolution we find that both temperature and light strongly influence shell growth rates besides demonstrating light enhanced calcification we also observe growth inhibition during culture in continuous darkness ultra high resolution la icp ms analysis warter and muller 2017 in tandem with 135ba labelling allows both to identify newly secreted cultured aragonite and investigate its trace elemental composition at sub daily resolution b ca mg ca sr ca ba ca overall average element calcium el ca ratios reveal an inverse relation with temperature and light strikingly an increasing trend in all el ca ratios is observed in the direction of shell growth which is interpreted to be metabolically controlled possibly related to organism stress daily cyclic trace element variability can be clearly resolved at 5 15 m in relatively fast growing shells which experienced a diurnal light cycle but constant temperatures we conclude that light but not temperature is the primary controlling factor responsible for daily trace element variability we further demonstrate that high el ca ratios correspond to growth during night time i e low light intensities corroborating field observations by sano et al 2012 yet because light levels were kept constant during night and day respectively light intensity cannot account for the entire range of the el ca variability we hypothesize that tridacna physiology and biochemistry is controlled by a circadian rhythm initiated by the external factor light but endogenously mediated by the giant clam and or its photosynthetic symbionts

increased seasonality in the western mediterranean during the last glacial from limpet shell geochemistry the seasonal cycle is a fundamental aspect of climate with a significant influence on mean climate and on human societies assessing seasonality in different climate states is therefore important but outside the tropics very few palaeoclimate records with seasonal resolution exist and there are currently no glacial age seasonal resolution sea surface temperature sst records at mid to high latitudes here we show that both mg ca and oxygen isotope 18o ratios in modern limpet patella shells record the seasonal range of sst in the western mediterranean a region particularly susceptible to seasonal change analysis of a suite of fossil limpet shells from gibraltar shows that sst seasonality was greater during the last glacial by 2 c as a result of greater winter cooling these extra tropical seasonal resolution sst records for the last glacial suggest that the presence of large ice sheets in the northern hemisphere enhances winter cooling this result also indicates that seasonality in the mediterranean is not well represented in most palaeoclimate models which typically show little change in seasonal amplitude and provides a new test for the accuracy of climate models

and ratios in skeletal calcite of mytilus trossulus covariation with metabolic rate salinity and carbon isotopic composition of seawater minor element and isotopic compositions of marine bivalve calcite are frequently used as proxy records of seawater temperature and salinity although molluscan calcite is secreted at or near oxygen isotope equilibrium the influence of metabolic activity i e vital effects on skeletal srca ratios and 13c values is not well known we present measurements of skeletal chemistry from a consecutive samples milled in chronological order from the organism s final year of growth and b adjacent samples within three separate growth bands of the marine mussel mytilus trossulus to investigate chemical disequilibrium effects among different parts of the shell seawater temperature and salinity were monitored for one year at squirrel cove british columbia at the end of the year a young rapidly growing mussel mussel a and an old slowly growing mussel mussel b were harvested from this site growth bands within the shells were sampled to provide a chronological record of shell carbonate chemistry results from consecutive samples show 1 a significantly higher average srca ratio in mussel a than that in mussel b and 2 13c values that correlate well with salinity in mussel a but not in mussel b results from time equivalent adjacent samples show 1 higher srca and 13c values near the ventral margin than at time equivalent regions on lateral margins of the shell and 2 little or no variation in 18o values these observations suggest that skeletal chemistry srca and 13c is primarily controlled by rate of mantle metabolic activity and secondarily modified by variation in seawater salinity because metabolic activity in the mantle at the site of carbonate precipitation varies with shell curvature the composition of calcite secreted along lateral margins is influenced to a greater extent by metabolic activity than calcite secreted coevally at the central margin of the shell hence the chemistry of calcite secreted at the ventral margin is precipitated in near equilibrium with seawater and allows accurate estimation of seawater srca ratios and carbon isotopic composition in contrast shell precipitation along lateral margins is dominantly controlled by metabolic activity and calcite chemistry is not in equilibrium with ambient seawater in this context we present a biomineralization model where variations in skeletal srca and 13c values are explained in the context of mantle metabolic activity and seawater salinity

geochemical fingerprints of climate variation and the extreme la nina 2010 11 as recorded in a tridacna squamosa shell from sulawesi indonesia abstract we used a tridacna squamosa tridacnidae bivalvia shell that lived between 2006 and 2012 to reconstruct environmental conditions in south east sulawesi indonesia we focused mainly on estimating the influence of temperature and rainfall on the shell geochemistry as well as enso anomalies comparison of the measured and theoretical 18 o values show clear seasonal variations and confirms that this species secretes its shell at isotopic equilibrium the 18 o in t squamosa shows how the increased rainfall associated with monsoon precipitations in this area influences the 18 o shell signal during the rainy season the correlation between shell 18 o and sst r 2 0 62 decrease in warm wet seasons sst 28 5 c shell mg ca profiles presents better correlation with sst r 2 0 8 than sr ca profiles r 2 0 52 shell ba ca ratio increases during each dry season when primary productivity is maximum secondary ba ca peaks also occur during the certain wet seasons and appear associated with abnormal enhanced runoff shell 13 c co varies with primary productivity and salinity with highest 13 c values occurring during the dry seasons during 2010 11 abnormal values were detected in all geochemical proxies as result of the strong la nina event this calibration study demonstrates the ability of t squamosa shells to accurately reflect present day environmental processes with seasonal resolutions and to define the local signature of hydrological changes associated with enso

calibration of the mg ca of globorotalia truncatulinoides r for the reconstruction of marine temperature gradients 1 recent work has provided useful mg ca to water temperature calibrations for shallow dwelling planktonic foraminifer species globorotalia truncatulinoides right coiling r is a deep dwelling species that can serve as a source of information about the temporal variability in the water characteristics of the thermocline we present a temperature calibration for the mg ca in the shell of g truncatulinoides r and examine some of the practical issues associated with evaluating the usefulness of the technique the mg ca in the primary and the secondary calcite of individual g truncatulinoides r correlates exponentially with water column temperatures showing a change of 10 in the mg ca per 1 c r2 0 92 a limited comparison with plankton tow samples demonstrates that the average mg ca temperature was offset 1 c from the average temperature calculated using the 18o calibration of o neil et al 1969 and the mg ca temperatures have a range similar to the 18o temperatures comparisons of the mg in the core top samples to water depth of deposition indicates that dissolution does not alter the measured value of mg in the primary calcite

sea surface water temperatures over the period 1884 1983 reconstructed from oxygen isotope ratios of a bivalve mollusk shell arctica islandica southern north sea although climate system modeling cannot be imagined without long sea surface temperature sst records observational data is spatiotemporally incomplete and inhomogeneous prior to about 1950 moreover almost no high resolution sst proxies exist from temperate and boreal marine settings here we present a temporally equidistant high resolution sst proxy record of the southern north sea during the period 1884 1983 calculated from oxygen isotope ratios 18oaragonite of arctica islandica l a bivalve mollusk shell arctica islandica produces daily growth increments which enable precise intraannual dating the growing season of specimens from about 25 m water depth upper well mixed layer of the ocean started in february and ended in september observational coads etc and 18oaragonite derived sst data during february through september compare well to each other especially after 1950 apart from similar overall sst trends we found north atlantic oscillation type cycles of 7 9 years in our proxy sst record and in various different instrumentally determined sst chronologies no vital effects exist so that 18oaragonite ratios determined across the shell i e throughout lifetime of the studied specimen reflect ambient water temperatures that occurred during shell growth results of our study demonstrate that a islandica provides long independent and high resolution sst proxy chronologies from higher latitudes such records can complement and further validate observational sst data and help improving climate system models

mg ca sr ca and stable isotope δ18o and δ13c ratio profiles from the fan mussel pinna nobilis seasonal records and temperature relationships 1 we present new annually resolved 18o 13c mg ca and sr ca ratio records for two shells of the fast growing mediterranean fan mussel pinna nobilis collected from proximal spanish coast sea grass meadows the relationship between the potential geochemical proxies and ontogenetic and environmental controlling factors is investigated specifically the use of shell mg ca and sr ca ratios as potential calcification temperature proxies the latter calculated from measured shell 18o values has been assessed the 18o cycles along the growth axis indicate that our p nobilis specimens are 10 5 and 4 5 years old shell sr ca ratios do not exhibit any consistent interannual cyclicity and are not correlated to temperature a subtle ontogenetic effect on shell mg ca ratios was observed during the first 4 5 years of recorded growth but was highly evident during the organism s later growth years in p nobilis shells different mechanisms influence ontogenetic variation in shell mg ca and 18o records shell mg ca ratios from the first 4 5 years of growth correlate significantly to temperature in a best fit relationship described by the equation mg ca 17 16 1 95 exp 0 022 0 004 t p nobilis shell mg ca records therefore are a valid temperature proxy only during an early growth phase for the same range of temperatures shell mg ca ratios in p nobilis are approximately 1 3 lower than those reported for inorganic calcite but 3 to 4 times higher than in another bivalve species mytilus trossulus and 4 to 16 times higher than in foraminifera we suggest these offsets are due to a higher degree of similarity between seawater and calcification fluid composition in p nobilis than in other bivalves and foraminifera the observed shell mg ca ratio change per c of 2 2 also is lower than that observed for inorganic and other biogenic calcites our findings strongly support taxon and species specific mg ca temperature relationships for bivalves and other calcifying organisms an appreciation of the physiology and calcification mechanisms of any biogenic carbonate archive therefore is paramount prior to the application of stable isotope and element ca ratio proxies for paleotemperature reconstructions

the nature and origin of a jokulhlaup near casey station antarctica description de la nature de l episode d eruption d eau et resultats des etudes menees pour determiner l origine et la source de cette eau

mollusc and brachiopod skeletal hard parts intricate archives of their marine environment the biogenic carbonate hard parts of fossil bivalves cephalopods and brachiopods are among the most widely exploited marine archives of phanerozoic environmental and climate dynamics research the advent of novel analytical tools has led many workers to explore non traditional geochemical and petrographic proxies and work performed in neighbouring disciplines sheds light on the complex biomineralization strategies applied by these organisms these considerations form a strong motivation to review the potential and problems related to the compilation and interpretation of proxy data from bivalve cephalopod and brachiopod hard parts from the viewpoint of the sedimentologist and palaeoceanographer specific focus is on the complex biomineralization pathways of a given dissolved ion or food particle from its aquatic environment via the digestion and biomineralization apparatus in molluscs and brachiopods and its incorporation into a biomineral given that molluscs and brachiopods do not secrete their hard parts from seawater but rather from their mantle and periostracum this paper evaluates differences and similarities of seawater versus that of body fluids cephalopods bivalves and brachiopods exert a strong biological control on biomineralization that to some degree may buffer their shell geochemistry against secular changes in seawater chemistry disordered amorphous calcium carbonate precursor phases later transformed to crystalline biominerals may be significant in carbonate archive research due to expected geochemical offset relative to the direct precipitation of stable phases a reasonable level of understanding of the related mechanisms is thus crucial for those who use these skeletal hard parts as archives of the palaeo environment the impact of what is commonly referred to as biological factors on the geochemistry of mollusc and brachiopod hard parts is explored for conventional isotope systems such as carbon oxygen strontium and traditionally used element to calcium ratios in particular the often used 13ccarb or the mg ca and sr ca elemental proxies are fraught with problems an interesting new research field represents the analysis calibration and application of non traditional proxies to mollusc and brachiopod hard parts examples include the carbonate clumped isotope 47 approach and the analysis of the isotopes of ca mg n li s or element to ca ratios such as li ca or b ca and rare earth elements based on considerations discussed here a series of do s and don ts in mollusc and brachiopod archive research are proposed and suggestions for future work are presented in essence the suggestions proposed here include experimental work also field experiments making use of recent archive organisms or where possible a reasonable recent analogue in the case of extinct groups moreover the detailed understanding of the architecture of mollusc and brachiopod hard parts and their ultra structures must guide sampling strategies for geochemical analyses where feasible a detailed understanding of the diagenetic pathways and the application of multi proxy and multi archive approaches should form the foundation of fossil carbonate archive research the uncritical compilation of large data sets from various carbonate shelled organisms collected at different locations is not encouraged

isotopic evidence of cool winter conditions in the mid piacenzian pliocene of the southern north sea basin oxygen isotope thermometry of aequipecten opercularis and atrina fragilis bivalves which demonstrate all year growth provides quantitative evidence of cool temperate winter conditions below 10 c during deposition of the mid piacenzian oorderen sands and time equivalent strata in the southern north sea basin snsb isotopic summer temperatures seafloor are within or only marginally above the cool temperate range upper limit 20 c the occurrence of warm temperate dinoflagellate cysts alongside and presumably contemporaneous with the bivalves indicates the development of a correspondingly warm surface layer in summer encystment allowing the dinoflagellates to survive cool winter conditions this evidence of greater surface seasonality than now is consistent with greater global warmth and a reduction in the vigour of the gulf stream north atlantic drift gs nad leading to a reduced supply of winter heat this reduction in gs nad strength may be linked to breaching of the emerging isthmus of panama

mg ca in fossil oyster shells as palaeotemperature proxy an example from the palaeogene of central asia fossil oyster shells are well suited to provide palaeotemperature proxies from geologic to seasonal timescales due to their ubiquitous occurrence from triassic to quaternary sediments the seasonal nature of their shell growth and their relative strong resistance to post mortem alteration however the common use to translate calcitic oxygen isotopes into palaeotemperatures is challenged by uncertainties in accounting for past seawater 18o especially in shallow coastal environment where oysters calcify in principle the mg ca ratio in oyster shells can provide an alternative palaeothermometer several studies provided temperature calibrations for this potential proxy based on modern species nevertheless their application to palaeo studies remains hitherto unexplored here we show that past temperature variability in seawater can be obtained from mg ca analyses from selected fossil oyster species and specimens high resolution mg ca profiles combined with 18o were obtained along 41 fossil oyster shells of seven different species from the palaeogene proto paratethys sea central asia found in similar as well as different depositional age and environments providing comparison suitable mg ca profiles defined by continuous cyclicity and reproducibility within one shell are found to be consistent for specimens of the same species but differ systematically between species implying a dominant species specific effect on the mg ca signal two species studied here ostrea turkostrea strictiplicata and sokolowia buhsii provide an excellent proxy for palaeoclimate reconstruction from china to europe in palaeogene marine sediments more generally the protocol developed here can be applied to identify other fossil oyster species suitable for palaeoclimate reconstructions

assessment of mg ca in saccostrea glomerata the sydney rock oyster shell as a potential temperature record bivalve shell mg ca records can be important potential tracers of paleo temperature but evidence has shown that the temperature dependence of trace metal incorporation rates can vary significantly between different species and even within the same species this study assesses one such bivalve specimen as a potential temperature proxy for the east coast of australia specimens of the sydney rock oyster saccostrea glomerata were cultured for approximately one year at two locations on the east coast of australia moreton bay queensland a semi enclosed bay with consistently marine conditions and pambula lake new south wales a tidal lake which can undergo significant variations in salinity as a result of rainfall and river discharge transects of the oysters growth axis were analysed via la icp ms mg ca temperature relationships for the oysters show a robust temperature dependence but there is also a clear discrepancy between the two sites however this discrepancy was not evident when the temperature dependence of mg partition coefficients dmg was determined indicating that the difference seen in the direct mg cashell temperature relationships can be accounted for by variation in salinity at the estuarine site of pambula lake this has implications for the use of mg ca as a paleo temperature tracer within estuarine fauna as knowledge of the water chemistry is required to determine dmg values however s glomerata mg ca remains a promising paleo temperature tracer as the direct mg ca temperature relationships can still be applied to samples from environments that experienced little variation in salinity combined analysis of mg ca coupled with 18oshell records has the potential to enable the deconvolution of the combined salinity temperature signal in the 18oshell and mg cashell records

the shell of the queen scallop aequipecten opercularis l as a promising tool for palaeoenvironmental reconstruction evidence and reasons for equilibrium stable isotope incorporation abstract the queen scallop aequipecten opercularis has been an important part of the marine fauna of the northeast atlantic region since the miocene and is a suitable candidate for palaeoenvironmental studies using stable isotopes modern shells were investigated to determine if carbonate is precipitated in isotopic equilibrium in this species and to confirm that growth continues through the year specimens of a opercularis were cultured under monitored semi natural conditions over an autumn winter period and the analyses of these specimens were supplemented with isotope data from preserved indigenous north sea specimens the results indicated that the cultured specimens grew in relatively low temperatures that oxygen isotopes of shell exterior carbonate were precipitated in isotopic equilibrium and that a large proportion of the ambient temperature range was recorded in shell carbonate the indigenous north sea specimens exhibited a good correspondence to predicted oxygen isotope values for summer the isotopic record related to winter was however somewhat truncated due to growth decelerations in the specimens carbon isotopes of shell exterior carbonate were calculated as being derived primarily from external sources and showed comparatively little influence from metabolically derived carbon this suggests that carbon isotopes were at least close to equilibrium with ambient waters the limited incorporation of metabolic products suggests that a opercularis would be a good monitor of changing carbon isotope ratios in seawater dissolved inorganic carbon the occurrence of equilibrium shell precipitation is explained using a pteriomorph shell calcification model which proposes that transport of ions through the periostracum caused the composition of the extrapallial fluid to be effectively the same as seawater carbonate secretion is therefore not influenced significantly by biological vital effects

controls on magnesium manganese strontium and barium concentrations recorded in freshwater mussel shells from ohio abstract freshwater bivalve shells may record inter annual fluctuations in water chemistry which in turn may archive variations in solute load due to pollution or discharge events here using weekly surface water chemistry collected at two locations and shells of lampsilis cardium grown in the surface water we investigate if the mg ca mn ca sr ca and ba ca ratios measured at high resolution in the shells on an intra annual time scale consistently reflect the chemistry of the surface water two relationships appear highly correlated sr cacarb and sr cawater and mn cacarb and temperature ba cacarb correlated strongly with ba cawater in one shell but temperature in another shell yielding inconclusive results mn cacarb and mg cacarb were not strongly correlated with elemental ratios in the water but mn cacarb did show variable weak to moderate correlation with ph we found consistent partition coefficient dme values between individual shell samples grown in the same water with mean dmg 0 0006 dmn 17 dba 0 13 and dsr 0 176 sr cacarb and sr cawater exhibited the strongest most consistent correlation with partitioning coefficients that were consistent with published values suggesting sr cacarb can be used as a proxy for sr cawater in freshwater mussels

the long lived mollusc arctica islandica a new paleoceanographic tool for the reconstruction of bottom temperatures for the continental shelves of the northern north atlantic ocean the carbonate shell of the bivalve arctica islandica has been recognized for more than a decade as a potentially important marine geochemical biorecorder owing to this species great longevity 200 years and wide geographic distribution throughout the northern north atlantic ocean a region vital to global climate and ocean circulation however until now this potential has not been realized owing to the difficulty of precisely sampling the shell of this slow growing species using newly available automated microsampling techniques combined with micromass stable isotope mass spectrometry a stable oxygen isotope record 1956 1957 and 1961 1970 has been obtained from a live captured 38 year old a islandica specimen collected near the former position of the nantucket shoals lightship 41 n 69 w the shell s 18o signal is compared with an expected signal derived from ambient bottom temperature and salinity data recorded at the lightship for the same period the results show that a islandica s 18o record 1 is in phase with its growth banding confirming the annual periodicity of this species growth bands 2 is in oxygen isotopic equilibrium with the ambient seawater 3 shows a consistent shell growth shutdown temperature of 6 c which translates into an 8 month may december shell growth period at this location and 4 records the ambient bottom temperature with a precision of 1 2 c these results add important information on the life history of this commercially important shellfish species and demonstrate that a islandica shells can be used to reconstruct inter and intra annual records of the continental shelf bottom temperature

isotope paleontology growth and composition of extant calcareous species abstract isotope paleontology uses the isotopic composition of fossil remains of organisms to make inferences about the physical surroundings of growth of the organisms especially temperature and to obtain clues about life history and modes of growth in calcareous fossils oxygen isotopes are mainly used in the former and carbon isotopes in the latter however since physical surroundings and organism response are intimately associated both types of information are contained in each of the isotopic signals to explore the potential of isotope paleontology and to provide a basis for reconstruction a broad range of extant organisms has been studied taking the pioneering work of epstein and associates as a starting point results are summarized for a representative sampling of these studies with emphasis on work at the laboratories of the authors from the mid seventies to the present the organisms considered are nannoplankton benthic algae planktonic and benthic deep sea foraminifera larger foraminifera sponges corals bryozoans polychaetes arthropods bivalves gastropods cephalopods and vertebrates fish otoliths the survey broadly suggests that regarding oxygen isotopes materials tend to be precipitated close to equilibrium with the surrounding seawater as postulated by urey and that for carbon isotopes disequilibrium is the rule life spans growth rates differential seasonal growth and age of reproductive activity can be extracted under favorable circumstances from individual shells and skeletal parts in detail the interpretation of isotope records of individual shells is quite complicated and simple models will fail to give satisfactory results in many or most cases

strontium magnesium and barium incorporation in aragonitic shells of juvenile arctica islandica insights from temperature controlled experiments abstract in order to constrain spatial and temporal temperatures and environmental conditions in the north atlantic ocean during the holocene high resolution seasonal to annual marine proxies with excellent chronological constraints are needed the long lived ocean quahog arctica islandica which has the potential to provide a precise annually dated record via crossdating techniques is a fairly well developed and tested marine proxy archive in particular oxygen isotopes derived from a islandica shell carbonate have provided a wealth of information on marine climate and ocean circulation dynamics however shell derived oxygen isotopes are influenced by both the isotopic source water signature covarying with salinity and seawater temperature if seawater isotopic signature is not known temperature reconstructions become challenging thus an independent technique to estimate past seawater temperatures is highly desired however based on previous studies on adult and juvenile clams the utility of elemental ratios in a islandica shell material as environmental proxies remains questionable to further evaluate the influence of seawater temperature on elemental and isotopic incorporation during biomineralization a islandica shells were grown at constant temperatures under two regimes during a 16 week period from march 27 to july 21 2011 at the darling marine center in walpole maine individual juvenile clams were stained with calcein and cultured at 10 30 0 30 c for six weeks after this the clams were again stained with calcein and cultured at 15 00 0 40 c for an additional 9 5 weeks average salinity values were 30 20 0 70 and 30 70 0 70 in the first and second phases of the experiment respectively continuous sampling within and across the temperature conditions from 10 30 c to 15 00 c coupled with the calcein markings provided the ability to place each sample into a precise temporal framework and to establish exact average growth rates for the shells sampled after accounting for changes in the isotopic composition of seawater oxygen isotopes from one sampled shell effectively recorded seawater temperatures during the study and also gave confidence to the temporal fit of the data elemental ratios sr ca mg ca ba ca from five aragonitic shells were determined via laser ablation inductively coupled plasma mass spectrometry sr ca and mg ca data showed little coherence with temperature during the culture experiment including the rapid 5 c increase in seawater temperature however ba ca ratios showed an inverse relationship with seawater temperatures although this relationship was noisy additionally salinity interactions were present during the 15 00 c treatment further highlighting complex incorporation of elements during biomineralization incorporation of sr mg and ba were strongly and variably impacted by growth rates combined the results from these culture experiments demonstrate that sr ca mg ca ba ca ratios in juvenile a islandica shell material are dominated by physiological processes and thus not reliable as environmental proxies

evidence for enhanced mixing over rough topography in the abyssal ocean the overturning circulation of the ocean plays an important role in modulating the earth s climate but whereas the mechanisms for the vertical transport of water into the deep ocean deep water formation at high latitudes and horizontal transport in ocean currents have been largely identified it is not clear how the compensating vertical transport of water from the depths to the surface is accomplished turbulent mixing across surfaces of constant density is the only viable mechanism for reducing the density of the water and enabling it to rise however measurements of the internal wave field the main source of energy for mixing and of turbulent dissipation rates have typically implied diffusivities across surfaces of equal density of only approximately 0 1 cm2 s 1 too small to account for the return flow here we report measurements of tracer dispersion and turbulent energy dissipation in the brazil basin that reveal diffusivities of 2 4 cm2 s 1 at a depth of 500 m above abyssal hills on the flank of the mid atlantic ridge and approximately 10 cm2 s 1 nearer the bottom this amount of mixing probably driven by breaking internal waves that are generated by tidal currents flowing over the rough bathymetry may be large enough to close the buoyancy budget for the brazil basin and suggests a mechanism for closing the global overturning circulation

the peridotite ridge province in the southern iberia abyssal plain seismic constraints revisited the west iberia margin has become the type example of a magma starved margin in which extension during breakup led to the exhumation of mantle rocks apparently over a broad area much of our understanding of this process is based on geophysical and drilling data from the southern iberia abyssal plain where the seaward part of the region of exhumed mantle is comprised of a series of margin parallel basement ridges here we analyse wide angle and normal incidence seismic data from a series of intersecting profiles across this peridotite ridge province and develop a three dimensional picture of its structure using these seismic data we infer a location and age magnetic anomaly m1 125 127 ma of first formed oceanic crust in this region that are consistent with ocean drilling program data and data from the conjugate margin we infer that the peridotite ridge province is about 70 km wide with strong serpentinization 75 at the top of basement reducing to much lower degrees 25 around 2 km below we map the geometry of some prominent reflectors on the landward margin of the peridotite ridge province that likely represent detachment faults and show that one of these has a domal structure similar to that of detachment faults at slow to ultra slow spreading mid ocean ridges

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

glaciofluvial crevasse and conduit fills as indicators of supraglacial dewatering during a surge skeiðararjokull iceland

tropical seasonality in the late campanian late cretaceous comparison between multiproxy records from three bivalve taxa from oman abstract geochemical proxy records from calcite shells of bivalves constitute an important archive for the reconstruction of palaeoenvironmental conditions on sub annual timescales however the incorporation of these trace element and stable isotope proxies into the shell is influenced by a multitude of physiological and environmental factors that need to be disentangled to enable reliable reconstruction of palaeoclimate and palaeoenvironment in this study records of multiple proxies in three bivalve taxa from the same late campanian locality in oman are used to study the expression of various geochemical proxies in relation to each other and to the palaeoenvironment micro x ray fluorescence mapping allows the localization discussion and evasion of diagenetically altered parts of the fossil shells x ray fluorescence line scanning calibrated with laser ablation inductively coupled plasma mass spectrometry is used to measure trace element profiles through well preserved calcitic parts of the shells records of stable carbon and oxygen isotope ratios of shell calcite are combined with these high resolution trace element concentration profiles to study sub annual variations in shell chemistry and reconstruct changes in the palaeoenvironment of the bivalves on a seasonal scale spectral analysis routines are used to detect cyclicity in stable isotope 18o and 13c and trace element mg ca sr ca s ca and zn ca records differences in seasonal expression between these chemical proxies and between individual shells are discussed in terms of the relative influence of palaeoenvironment and potential species specific physiological effects stable oxygen isotope ratios between shells suggest a local palaeotemperature seasonality of 8 c around an annual mean of 28 c with the shell of the rudistid torreites sanchezi milovanovici yielding slightly higher average temperatures the discussion of the application of various mg ca palaeotemperature calibrations on mg ca records in these bivalve species emphasizes the complexity of using trace element proxies in extinct bivalve species it shows that long term changes in mg ca ratios in ocean water need to be taken into account and that mg ca ratios in bivalves might be influenced by vital effects sr ca and s ca ratios in these fossil taxa are likely controlled by growth and metabolic rates of the shell although an influence of local salinity on strontium to calcium ratios cannot be excluded sub annual variations in zinc concentrations in shell calcite may reflect seasonal variations in palaeoproductivity and redox conditions in the water column

the potential of combined mg ca and δ18o measurements within the shell of the bivalve pecten maximus to estimate seawater δ18o composition the combined use of 18o and another independent palaeotemperature proxy from the same carbonate biomineral archive forms the basis of a much desired palaeosalinity proxy by circumventing the main source of uncertainty in interpreting 18o palaeorecords i e variations in the isotopic composition of seawater contrary to the 18o proxy transferring the mg ca temperature proxy to marine bivalves has proved problematic since a strong seawater temperature control on shell calcite mg ca has rarely been observed in this study a preliminary evaluation of the combined use of 18ocalcite and mg ca from pecten maximus inner shell calcite to estimate 18owater is reported new mg ca data obtained by milling the inner shell regions from p maximus specimens grown in laboratory aquaria under constant seawater temperatures between 10 and 20 c exhibit a strong relationship between mg ca and temperature mg ca 2 56 0 42 0 17 0 03 t r2 0 77 p 0 001 n 54 while the relationship between sr ca and temperature was not strong r2 0 30 p 0 001 n 54 using specimens grown in a separate aquaria validation experiment estimated mg ca derived seawater temperature was within 0 48 c of measured seawater temperature while estimated 18owater was within 0 05 to 0 15 of measured seawater 18o composition depending on the 18o temperature equation used and with uncertainty estimates of 0 63 and 0 35 such observations indicate the strongest potential to date for the development of valid temperature and 18owater salinity proxies in bivalves from the combined application of mg ca and 18ocalcite in the inner shell regions of p maximus further studies for a wide range of pectinid species ages and different natural environmental settings are needed to validate the observations of this study

exploring aberrant bivalve shell ultrastructure and geochemistry as proxies for past sea water acidification throughout much of earth s history marine carbonates have represented one of the most important geological archives of environmental change several pivotal events during the phanerozoic such as mass extinctions or hyperthermal events have recently been associated with ocean acidification nevertheless well defined geological proxies for past ocean acidification events are at best scarce here experimental work explores the response of bivalve shell ultrastructure and isotope geochemistry c 13 o 18 and mg 26 to stressful environments in particular to sea water acidification in this study the common blue mussel mytilus edulis was cultured from early juvenile stages to one year of age at four ph regimes ph nbs 72 to ph 80 shell growth rate and ultrastructure of mainly the calcitic portion of the shells were compared between experimental treatments specimens exposed to low ph environments show patches of disordered calcitic fibre orientation in otherwise well structured shells furthermore the electron backscattered diffraction analyses reveal that under acidified conditions the c axis of the calcite prisms exhibits a bimodal or multi modal distribution pattern similar shell disorder patterns have been reported from mytilids kept under naturally acidified sea water conditions in contrast this study found no evidence that different ph regimes affect shell carbon oxygen or magnesium isotope ratios based on these observations it is proposed that i stressful environments in this case low sea water ph predictably affect bivalve biomineralization patterns and ii these findings bear potential as a novel petrographic proxy for ancient sea water acidification an assessment of the applicability of these data to well preserved fossil shell material from selected time intervals requires additional work

the ormer haliotis tuberculata a new promising paleoclimatic tool abstract this study aimed to investigate the environmental controls on the oxygen isotope composition of shells of the european abalone haliotis tuberculata seasonal 18 o profiles from the outer prismatic layer of four abalone shells collected live in northwest brittany france in 2002 and 2012 were compared to local temperatures and salinities according to the findings herein 18 o variations in abalone shells corresponded to seasonal variations and thus shell composition represented a reliable tool for aging and growth studies seawater temperatures estimated from the abalone collected in 2012 reflected the in situ measured temperatures but the reconstructed temperatures from shells of the three specimens collected in 2002 deviated from measured temperatures by 2 5 c this overestimation of temperatures corresponded to a kinetic effect related to very high annual abalone growth rates thus it could be corrected by applying 0 53 to the 18 o shell this methodology was then applied to a fossil 6000 cal yr bp collected in the bay of biscay given the worldwide distribution of both live and fossilized abalones the results of the present study showed that this genus represents a promising paleoclimatic tool

ecological and paleoenvironmental information using stable isotope profiles from living and fossil molluscs stable oxygen and carbon isotopic profiles from recent specimens of spisula solidissima and placopecten magellanicus collected off the virginia coast are used to calibrate annual temperature controlled cycles in the 18o profile and shell growth characteristics the amplitude of the annual 18o cycles decreases with increasing water depth and may be used as a relative depth indicator the isotopic of profiles of two fossil specimens of pleistocene spisula are very similar in amplitude and character to modern analogues and verify the formation of annual growth increments in these fossil specimens offsets between the 18o profiles of the fossil and modern specimens are related to known temperature and ice volume effects during the late pleistocene and support the utility of mollusc isotope records as a stratigraphic tool carbon isotopic profiles from all specimens show light values in the spring and or fall associated with seasonal phytoplankton productivity offsets in the carbon isotopic composition between infaunal and epifaunal species may be related to sediment porewater geochemistry and oxidation of organic matter trends toward lighter 13c values through ontogeny suggest the effects of metabolic changes from a fast growing juvenile into a slower growing sexually mature adult anomalies in both the oxygen and carbon isotopic profiles identify the formation of minor shell growth increments as corresponding to hydrographic perturbations and to winter cold temperatures

benthic foraminiferal mg ca paleothermometry a revised core top calibration core top samples from different ocean basins have been analyzed to refine our current understanding of the sensitivity of benthic foraminiferal calcite magnesium calcium mg ca to bottom water temperatures bwt benthic foraminifera collected from hawaii little bahama bank sea of okhotsk gulf of california ne atlantic ceara rise sierra leone rise the ontong java plateau and the southern ocean covering a temperature range of 0 8 to 18 c were used to revise the cibicidoides mg ca temperature calibration the mg ca bwt relationship of three common cibicidoides species is described by an exponential equation mg ca 0 867 0 049 exp 0 109 0 007 bwt stated errors are 95 ci the temperature sensitivity is very similar to a previously published calibration however the revised calibration has a significantly different preexponential constant resulting in different predicted absolute temperatures we attribute this difference in the preexponential constant to an analytical issue of accuracy some genera notably uvigerina show apparently lower temperature sensitivity than others suggesting that the use of constant offsets to account for vital effects in mg ca may not be appropriate downcore mg ca reproducibility as determined on replicate foraminiferal samples is typically better than 0 1 mmol mol 1 2 s e thus considering the errors associated with the cibicidoides calibration and the downcore reproducibility bwt may be estimated to within 1 c application of the revised core top mg ca bwt data to cenozoic foraminiferal mg ca suggests that seawater mg ca was not more than 35 lower than today in the ice free ocean at 50 ma

seasonality in sea surface temperatures from δ18o in cladocora caespitosa modern adriatic to late pleistocene gulf of corinth high resolution stable isotope analysis of coral skeletons is an established method to help reconstruct seawater growth temperatures for palaeoenvironmental reconstructions here we investigated the temperate colonial mediterranean scleractinian coral cladocora caespitosa we first studied modern adriatic corals from mljet croatia where growth temperatures were known a clear sinusoidal cyclicity is present in the d18o of the modern coral skeletons with average cycle minima 3 3 and average maxima 1 6 cyclicity approximately matches the number of seasonal growth band pairs in each sample implying a genetic link between d18o cyclicity and factors that determine seasonal growth band development here mainly water temperature a derived and calibrated species specific d18o temperature relationship was then used to reconstruct growth temperatures from fossil c caespitosa this was applied to well preserved material collected from late pleistocene deposits mis 1 5 and 7 around the gulf of corinth greece clear seasonal d18o signals are seen in all the fossil samples mis 5e was the warmest period studied with a lower than modern seasonal temperature range the early to mid holocene probably experienced the lowest temperatures while conditions in mis 7a c were probably the wettest with most freshwater input into the gulf

oxygen isotopes in glacier river water austre okstindbreen okstindan norway there is no discernible river discharge from austre okstindbreen norway in winter any water formed by basal melting is likely to be stored in isolated cavities or sediments at the bed in summer a baseflow component of discharge relatively depleted of 18 o is diluted by water more enriched in 18 o glacier ice meltwater with a high 18 o value passes rapidly through channelized systems and emerges in the glacier river within a few hours headward extension of the systems in late summer may tap water stored within the glacier since the previous summer s close down stored water also is released during early melt season events when the low capacity drainage systems cannot accommodate inputs the high 18 o value indicates that the probable source of the released water is glacier ice or low altitude snowfall stratigraphic variations of 18 o values resulting from changing weather conditions characterize the accumulating winter snowpack during the melt season the mean 18 o value of the residual pack rises the water leaving it depleted of 18 o passes slowly through the glacier smoothing out variations of supply 18 o values of rain vary between and within events and their effect on glacier river 18 o values is unpredictable

seismic constraints on the crustal structure within the vema fracture zone results from recent studies of the in well surveyed areas such as the famous area in kane and oceanographer fracture zones suggest that the central north atlantic ramberg et al 1977 significant variations in crustal thickness are transform faults are found every 50 to 100 km associated with parts of these fracture zones making them one of the most common tectonic with total crustal thicknesses in places less than features in the ocean basins morphologically half the thickness of normal oceanic crust the fracture zones on slowly spreading ridges display extent of this anomalous crust and its origin are many similar characteristics deep closed con still very poorly constrained by available geo tour depressions are usually present at ridge physical data here we report results from a 75 axis transform intersections sleep and biehler km long refraction line shot in late 1977 over 1970 the axis of the transform is typically three hawaii institute of geophysics ocean bottom defined by a deep linear trough bounded by escarpments rising eimom uuyuu withe ve valley near its western intersection with the mid transform valley floor a diverse suite of atlantic ridge 10o53 n 43o39 w we show that the apparent crustal thickness beneath this por tion of the vema transform valley is about 5 km not substantially different from crustal thick nesses typically associated with oceanic crust however the vema fracture zone crust is clearly anomalous and similar in many respects to crust reported from the kane and oceanographer fracture zones it is characterized by low compressional wave velocities a relatively uniform velocity gradient throughout most of the crust and the absence of a typical layer 3 refractor this anomalous crust is interpreted as intensely fractured hydrothermally altered and serpenti nized crustal and upper mantle rocks overlain by locally thick accumulations of basaltic rubble from the adjacent fracture zone walls the large variation in moho depths found in these large offset slowly slipping transforms is attributed to differences in the depth and extent of serpen tnnization of ultramafics lying beneath a thin and highly fractured basaltic and gabbroic layer one important consequence of the relatively low seismic velocities and densities inferred for the crust in these fracture zones is that transform valleys are not in local isostatic equilibrium with the surrounding seafloor

in situ study of the eastern ridge transform intersection of the vema fracture zone abstract fourteen dives of the submersible nautile have been carried out at the eastern intersection of the vema fracture zone with the mid atlantic ridge direct observations allow us to locate precisely the surficial expression of the transform fault motion in the southern trough of the fracture zone valley the present day displacement zone corresponding to an extremely narrow less than 300 m transform fault zone is confined to a belt of disturbed terrain situated at the foot of the southern wall and characterized by transform parallel 30 100 m high ridges of basaltic fragments and pelagic sediments active splays of the transform fault zone lie generally between these ridges creating steep v shaped furrows despite a rather sinuous trend one of the fault strands appears to be laterally continuous and other minor active splays branch out from it or run parallel to it the surface manifestations of the tectonic activity along the present day displacement zone include r riedel shears low angle shears p shears en echelon structures open fissures small pull apart structures and funnel alignments in the sedimentary cover the transform fault motion reactivates large normal faults on the adjacent flanks of the southern wall and the median ridge the transform parallel topography defines a 10 km wide zone with dip slip motion the ridge transform intersection area is entirely floored by fresh basalts contrasting with other intersections of major fracture zones such as the kane and oceanographer fracture zones recent volcanic activity is not restricted to the central volcanic ridge but is widespread across the whole nodal basin area the present day displacement zone cross cuts the neovolcanic zone and the disconnected northernmost extension of the volcanic ridge is attached to the median ridge and so belongs to the african plate the extensive volcanism is suggestive of a magmatic production phase in the intersection area extremely fresh pillowed lava forms have been observed at the rti inside corner high indicating possible off axis volcanism

habitat characterization of the vema fracture zone and puerto rico trench abstract although many of the regions on and close to the mid ocean ridges have been extensively mapped and sampled the abyssal intraplate regions remain essentially unsampled and unmapped leaving huge gaps in our understanding of their geologic history and present activity prominent bathymetric features in these intraplate regions are fracture zones here we present bathymetric and sampling information from a transatlantic transect along the vema fracture zone ca 11 n covering crustal ages from 109 0 ma on the african plate and 0 62 ma on the south american plate the vema fracture zone is the intraplate trace of the active vema transform plate boundary which offsets the present day mid atlantic ridge by ca 300 km left laterally juxtaposing zero age crust with crust of 20 million years age our results show clear evidence of tectonic activity along most of the fracture zone in most places likely associated with active fluid flow within the active vema transform at crustal ages of ca 10 ma we found clear indications of fluid flow both in the sediments and the overlying water column this region is 120 km from the nearest spreading axis and increases by almost an order of magnitude the maximum off axis distance that active hydrothermal discharge has been found on the oceanic crust sampling of the igneous seafloor was possible at all crustal ages and the accretionary fabric imprinted on the plate during its production was prominent everywhere seafloor sediments show signs of extensive bioturbation in one area high concentrations of spherical mn nodules were also found and sampled at the end of the transect we also mapped and sampled the puerto rico trough a 8000 m deep basin north of the caribbean arc here the seafloor morphology is more complicated and strongly influenced by transpressive tectonics

did the mediterranean marine reflooding precede the mio pliocene boundary paleontological and geochemical evidence from upper messinian sequences of tuscany italy abstract the events related to the messinian salinity crisis are among the most deeply investigated of earth s history according to the current hypothesis of neogene paleogeographic evolution approximately 5 5 ma ago after evaporitic sedimentation and before the mio pliocene boundary the mediterranean was characterized by the widespread development of non marine environments inhabited by molluscs and ostracods of brackish affinity the messinian post evaporitic deposits that testify such a dramatic environmental change are commonly referred to as lago mare and have been reported from several outcrops and boreholes throughout the entire mediterranean basin the origin of lago mare conditions is commonly interpreted as the result of the synergistic effect of both the humid climatic conditions and change of the drainage patterns at the mediterranean scale with the capture of paratethyan brackish waters a few recent studies however suggest that such a scenario probably represents an oversimplification of the original context from both a paleogeographical and paleoenvironmental point of view unfortunately the results of these studies have never been commonly accepted and the proposed evidences have been considered questionable in this paper we describe the fish assemblages from the lago mare deposits of two localities cava serredi and podere torricella located in the neogene hinterland basins of tuscany central italy these assemblages consists of a mixture of marine euryhaline and stenohaline taxa suggesting that the depositional environments were characterized by permanently open connections with a marine basin filled with normal marine waters in order to better define the paleontological significance of these upper messinian fish assemblages the oxygen carbon and strontium isotopic composition of fish otoliths and other fossils has been measured these isotopic compositions are strongly indicative of the presence of normal marine conditions close to the depositional environments testified by the sedimentary sequences thereby implying that the interpretation of the geochemical results are consistent with those derived from the paleoecological analyses of the fish assemblages based on the integrated paleoichthyological geochemical approach discussed in this paper it is possible to unambiguously demonstrate that normal marine rather than fresh or brackish waters were present in the mediterranean at least during the upper part of the lago mare event providing an unquestionable evidence that the marine refilling of the basin preceded the mio pliocene boundary

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

application of a radially viewed inductively coupled plasma optical emission spectrophotometer to simultaneous measurement of mg ca sr ca and mn ca ratios in marine biogenic carbonates 1 we developed and applied an analytical system for the simultaneous determination of magnesium calcium strontium calcium and manganese calcium ratios in biogenic carbonates using a perkin elmer 4300 optima dv inductively coupled plasma optical emission spectrophotometer in radial mode intensity ratio responses to calibration standard elemental ratios were linear over suitable working ranges we evaluated instrumental response using solution replicates and we analyzed planktonic foraminifera in multiple runs ca concentrations were kept in a relatively narrow range typically 0 6 2 4 mm ca although we found no resolvable ca matrix effect over a much wider range each analysis required a minimum sample volume of 300 l and took 3 5 min instrument time an analytical run of 30 samples plus standards blanks and control materials typically took 5 6 hours reproducibility interrun precision 1s rsd for solutions was 1 2 1 5 and 1 2 for mg ca sr ca and mn ca ratios far smaller than reproducibility for foraminiferal replicates over multiple analytical runs there was no independent reference material for assessing accuracy detection limits were equivalent for an 0 5 mm ca solution to 0 058 mmol mol for mg ca 0 015 mmol mol for sr ca and 0 005 0 020 mmol mol for mn ca precautions included limiting length of time the peristaltic tubing for the autosampler was used avoiding mg contamination from plastic ware and screening out results from samples with very low ca concentrations 0 25 mm ca

daily growth and tidal rhythms in miocene and modern giant clams revealed via ultra high resolution la icpms analysis a novel methodological approach towards improved sclerochemistry abstract we present a novel approach for ultra high resolution laser ablation inductively coupled plasma mass spectrometry la icpms analysis which not only allows us to clearly resolve tridacna giant clam shells daily element ca variability preserved within microscopically visible growth increments is resolved by utilizing the combined capabilities of a rotating rectangular aperture spot size on target 4 50 m the rapid signal washout of a laurin two volume laser ablation cell and slow compositional profiling 1 5 m s striking co variation between oscillating cycles in b ca mg ca sr ca and ba ca is discernible yet also tantalizingly sub daily shifts between these element ca ratios can be observed in comparison to a lower resolution seasonally resolved 18 o mg ca record warter et al 2015 the 10 20 m element ca cycles are determined to be daily in origin and a further 14 15 day cyclicity is superimposed on the daily cycles the latter is interpreted to reflect miocene tidal periodicity changes in pixel intensity during thin section observation associated with micro and macroscopically visible low and high density bands have been quantified via image processing analysis this reveals close correspondence to the measured trace elemental cyclicity indicating a coupling between the geochemical composition of the shell and the incremental growth pattern a comparison between the elemental and image processing results reveals that ultra high resolution la icpms analysis surpasses the latter in detecting environmental rhythms including daily and tidal cycles highly resolved la icpms analysis is a viable alternative to nanosims and opens up routine investigation of long term deep time paleoenvironmental records at daily resolution

influence of temperature on the composition of magnesian calcite overgrowths precipitated from seawater a constant disequilibrium technique was used to determine the composition of magnesian calcite overgrowths precipitated on pure calcite seeds from artificial seawater at 5 25 and 40 c the amount of magnesium incorporated in the overgrowths at a given temperature is independent of the precipitation rate over a wide range of saturation states and is believed to correspond to a composition in true equilibrium with seawater the distribution coefficient of magnesium dmg2 c in the magnesian calcite overgrowths increases almost linearly with temperature being 0 0121 0 0013 at 5 c 0 0172 0 0022 at 25 c and 0 0271 0 0013 at 40 c these values apply only to magnesian calcites precipitated from standard composition seawater since a previous study has shown dmg2 c to be a function of the mg2 ca2 ratio in the parent solution results of this study are compared with values reported previously by other workers and with the compositional distribution of naturally occurring magnesian calcite cements and ooids found in seawater it appears that variations in temperature are not sufficient to account for the compositional variability of naturally occurring inorganic marine magnesian calcite cements

paleoceanographic conditions at approximately 20 and 70 ka recorded in kikaithyris hanzawai brachiopoda shells abstract the 13c and 18o values of fossil brachiopod shells have been widely used as paleoenvironmental proxies in this study we investigated intrashell and intraspecific variations in the isotopic and minor element concentrations of well preserved shells of the brachiopod kikaithyris hanzawai yabe from the last glacial period 20 ka last glacial maximum lgm and 70 ka marine isotope stage 4 mis4 collected in the central ryukyus and used these data to estimate the paleoceanographic conditions seawater temperature concentration of dissolved inorganic carbon dic and 13c value of dic 13cdic the 13c and 18o profiles along the maximum growth axis obtained from the inner shell surface show three distinct intervals corresponding to changes in shell morphology these results suggest that the bulk isotopic compositions of brachiopods with complex shell morphologies are unsuitable for paleoenvironmental reconstructions nevertheless there exists a specific shell portion with relatively small intrashell and intraspecific variations the past seawater temperatures derived from the 18o values of this portion are consistent with the alkenone and planktic foraminiferal mg ca based past seawater temperatures reported in previous studies the past 13cdic values estimated from the 13c values of the specific shell portion are within the range of the past 13cdic values calculated from known atmospheric and oceanographic parameters the past dic concentrations reconstructed from the brachiopod based 13cdic values are lower than the present concentrations in the east china sea which can be explained by low partial pressure of co2 during the last glacial period these results indicate that the 13c and 18o values obtained from k hanzawai shells are potential paleoenvironmental indicators the intrashell and intraspecific variations in the k hanzawai shells are different for each minor element some anomalously high mn and fe concentrations in the shells are probably caused by metabolic factor s not by meteoric diagenesis this suggests that the minor element concentrations are useful but not perfect for distinguishing diagenetically altered and unaltered portions of the shells of k hanzawai in the studied succession

micro scale geochemical and crystallographic analysis of buccinum undatum statoliths supports an annual periodicity of growth ring deposition abstract the whelk buccinum undatum is commercially important in the north atlantic however monitoring the ontogenetic age and growth of populations has been problematic for fisheries scientists owing to the lack of a robust age determination method we confirmed the annual periodicity of growth rings present in calcified statoliths located in the foot of field collected and laboratory reared whelks using microscale measurements of trace element geochemistry using secondary ion mass spectrometry sims annual trace element profiles were quantified at 2 m resolution in statoliths removed from whelks collected alive from three locations spanning the length of the uk the shetland isles north the menai strait north wales mid and jersey south clear cycles in the mg ca ratio were apparent with minimum values corresponding with the visible dark statolith rings and comparatively higher ratios displayed in the first year of growth statoliths from one and two year old laboratory reared whelks of known age and life history contained one and two mg ca cycles respectively and demonstrated that the statolith growth ring is formed during winter february and march cycles of na ca were found to be anti correlated to mg ca cycles whilst ratios of sr ca were inconsistent and showed an apparent ontogenetic increase suggesting strong physiological control variability in elemental data will likely limit the usefulness of these structures as environmental recorders the results obtained using sims for trace element analysis of statoliths confirms the robustness of the statolith rings in estimating whelk age xrd at 2 m spatial resolution demonstrated the statoliths were wholly aragonitic and thus trace element variation was not the result of possible differences in caco3 polymorph within the statolith changing xrd patterns along with sem imaging also reveal an hourglass microstructure within each statolith the validation of the annual periodicity of statolith growth rings now provides a robust and novel age determination technique that will lead to improved management of b undatum stocks

a biomineralization model for the incorporation of trace elements into foraminiferal calcium carbonate measurements of srca of benthic foraminifera show a linear decrease with water depth which is superimposed upon significant variability identified by analyses of individual foraminifera new data for cdca support previous work in defining a contrast between waters shallower and deeper than 2500 m measured element partition coefficients in foraminiferal calcium carbonate relative to sea water d have been described by means of a one box model in which elements are extracted by rayleigh distillation from a biomineralization reservoir that serves for calcification with a constant fractionation factor such that d 1 f 1 f where f is the proportion of ca remaining after precipitation a modification to the model recognises differences in element speciation the model is consistent with differences between dsr dba and dcd in benthic but not planktonic foraminifera depth variations in d for sr and ba are consistent with the model as are differences in depth variation of dcd in calcitic and aragonitic benthic foraminifera the shallower depth variations may reflect increasing calcification rates with increasing water depth to an optimum of about 2500 m observations of unusually lower dcd for some deep waters not accompanied by similar dsr or dba may be because of dissolution or a calcification response to a lower carbonate saturation state

glacial interglacial changes in subantarctic sea surface temperature and δ18o water using foraminiferal mg laboratory culturing experiments with living globigerina bulloides indicate that mg ca is primarily a function of seawater temperature and suggest that mg ca of fossil specimens is an effective paleotemperature proxy using culturing results and a core top neogloboquadrina pachyderma calibration we have estimated glacial interglacial changes in sea surface temperature sst using planktonic mg ca records from core rc11 120 in the subantarctic indian ocean 43 s 80 e and core e11 2 in the subantarctic pacific ocean 56 s 115 w our results suggest that glacial sst was about 4 c cooler in the subantarctic indian ocean and 2 5 c cooler in the subantarctic pacific comparison of sst and planktonic 18o records indicates that changes in sst lead changes in 18o by on average 1 3 kyr the glacial interglacial temperature change indicated by the subantarctic mg ca records suggests that temperature accounts for 40 60 of the foraminiferal 18o change we have used the mg ca based sst estimates and 18o determinations to generate site specific seawater 18o records which suggest that seawater 18o was on average 1 more positive during glacial episodes compared with interglacial episodes

the oxygen and carbon isotope distribution in the mediterranean water masses abstract the oxygen and carbon stable isotope compositions of the present day mediterranean waters have been measured in order to evaluate their variability which is related to the specific climatic and hydrological conditions within the basin the experimental equation between the 18 o value and the salinity of water based on 300 measurements on surface intermediate and deep waters sampled during the vicomed 2 and 3 cruises in the western central and eastern mediterranean has a slope of 0 27 a value which is significantly lower than the slope of 0 45 as defined in the northeast atlantic ocean this difference in the 18 o salinity relationship which occurs immediately in the alboran basin is basically a characteristic of the climatic regime of the mediterranean i e of an excess evaporation over fresh water input the largest variations of these two parameters 18 o of water and 13 c of co 2 are observed in the surface waters mostly in the western mediterranean this evolution mirrors the progressive eastward restriction which separates the less evaporated and more productive western basins from the more evaporated and less productive eastern basins the intermediate waters constitute a homogeneous layer however their 18 o values decrease eastward by 0 35 at maximum due to progressive dilution by mixing with overlying and underlying water masses their 13 c values decrease also eastward by 0 35 at maximum due to an increasing input of nutrients issued from the regeneration of sinking organic particles the deep waters have similar 18 o values but slightly higher 13 c values often by less than 0 1 than the overlying intermediate waters indicating generally well ventilated conditions due to active winter convection