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

strontium contents of a porites coral from xisha island south china sea a proxy for sea surface temperature of the 20th century 1 a porites coral collected from xisha island south china sea represents a skeleton secreted in the period from 1906 to 1994 the sr contents of the coral vary linearly with the instrument measured sea surface temperature sst giving a sr thermometer sst 1 9658 x sr 193 26 the reconstructed sst data show that the late 20th century was warmer about 1 degreesc than the early 20th century and that two cooling 1915 1916 and 1947 1948 and three warming 1935 1936 1960 1961 and 1976 1977 shifts occurred in the century the temperature shifts are more pronounced for winters implying a close effect of the west pacific warm pool and asian monsoon and suggesting that the former is a primary force controlling the climatic system of the region results of this study and previously published data indicate a close link of temperature shifts between the boreal summer and the austral winter or the boreal winter and the austral summer the annual sst anomalies in the south china sea and the south pacific reveal the existence of harmonic but opposite sst variations between the two regions on the decadal scale the comparative annual sst anomalies for the south china sea and for the equatorial west pacific show a similarity in temperature variations implying that the south china sea climate is coherent with climatic regime of the tropical west pacific

a multiproxy approach to reconstructing sea surface conditions using coral skeleton geochemistry 1 we use elemental ratio mg ca sr ca u ca and ba ca and oxygen isotope data from a porites lutea coral head collected from offshore amedee island new caledonia 22 29 s 166 28 e to assess the degree to which changes in these geochemical variables reflect variations in sea surface conditions we have assessed the robustness of each geochemical proxy by comparing 25 years 1992 1968 of monthly geochemical variations with a local record of sea surface temperature sst and with the appropriate 1 by 1 grid box from a global gridded sst data set we conclude from our comparison that the most consistent proxies of monthly sst variations at this site are 18o r2 0 84 p 0001 and sr ca r2 0 84 p 0001 the fidelity of the coral based sr ca sst proxy was assessed via calibration verification exercises at new caledonia and rarotonga the paleoclimate accuracy of the coral sr ca sst technique is judged to be robust and the precision of the technique is estimated to be 0 3 0 5 2 based on the calibration verification exercise in contrast monthly variations in mg ca and u ca ratios are only moderately correlated with monthly sst variations r2 0 55 p 0001 for mg ca and r2 0 47 p 0001 the strength of the correlation between sst and mg ca and u ca varies as a function of time suggesting that variations in these ratios are not a simple function of sst variations this variability in goodness of fit between u ca sst and mg ca sst may ultimately limit the use of these ratios as coral paleothermometers averaging or stacking individual proxy sst records sr ca mg ca and u ca to generate a composite proxy sst record does not necessarily improve the proxy record if the signal to noise ratio in each proxy is highly variable for example stacking of sr ca mg ca u ca records at new caledonia produces a proxy sst time series that has greater standard error than the individual sr ca sst time series cf ordinary least squares standard error of 1 16 c versus 0 86 c ba ca variations have little correlation with sst sr ca mg ca or u ca variations at new caledonia in conclusion variations in oxygen isotopic composition of seawater calculated by removing the sr ca based temperature component of the 18o signal agree reasonably well with observed variations in sea surface salinity especially at the interannual timescale

a multiproxy record of terrestrial inputs to the coastal ocean using minor and trace elements ba ca mn ca y ca and carbon isotopes δ13c δ14c in a nearshore coral from puerto rico 1 small mountainous rivers smrs despite their disproportionate size relative to larger rivers may contribute as much as one third of the total terrigenous material exported to the coastal ocean corals growing near the mouths of tropical smrs have the potential to provide records of terrigenous material fluxes because they are long lived and elemental and isotope signatures within their skeletons are useful proxies of palaeoceanographic variability here a 56 year record of coral skeletal ba ca mn ca y ca 13c and 14c measurements is presented from a montastraea faveolata colony growing 1 km from the mouth of an smr in eastern puerto rico coral ba ca was coherent with river discharge and coral skeletal 13c at annual periodicity corresponding to synchronous depletions of both 13c and 14c in the coral skeleton and mn ca and y ca were not coherent with river discharge at annual periodicity coherence between river discharge and ba ca and the concurrent timing of increases in ba ca with decreases in 13c and 14c indicate that river discharge is simultaneously recorded by all three geochemical tracers a reconstruction of rio fajardo discharge is presented for a period in which no instrumental discharge records exists shows good fidelity with the timing of increased discharge during the wet season thus coral based multiple proxy records can be valuable tools for reconstructing the timing and variability of smr discharge to the coastal ocean such records are critical to understanding changes in material fluxes and biogeochemical cycles in coastal environments due to land use and climate change

is xrf core scanning a viable method for coral palaeoclimate temperature reconstructions abstract the use of x ray fluorescence xrf core scanning for continuous high resolution analysis of sr ca in corals is investigated here as a new method for analyzing coral material corals are valuable archives for generating high resolution palaeoclimate records of sea surface temperatures of the tropical oceans but traditional methods of analyzing coral geochemistry involve extensive subsampling and wet chemistry techniques to obtain high precision elemental records more recent developments of micro beam techniques have limitations in the length of core that can be scanned at any one time xrf core scanning provides a fast non destructive method of analyzing long sections of coral cores whilst maintaining a high sampling resolution here we apply this method to two modern corals from the sunda strait indonesia and one tree island great barrier reef australia we find that results show that xrf core scanning of corals produce sr ca records that capture the annual cycle particularly from reef sites with a large sea surface temperature range coupled density measurements of the coral skeleton also aid in increasing the utility of xrf measurements obtained from coral material although difficulties remain in reliably reconstructing interannual temperature variability using xrf sr ca determinations we recommend that xrf can provide a valuable method of quick and non destructive screening of coral material prior to more targeted analysis using traditional destructive geochemical analysis

surface ocean variability at galapagos from 1936 1982 calibration of geochemical tracers in corals a variety of geochemical tracers has been developed in reef corals as a means of reconstructing the natural variability of the tropical surface ocean over wide ranging time frames the purpose of this paper is to calibrate the performance of five of these tracers in a modern coral colony over an extended period a 47 year growth interval 1936 1982 in a colony of pavona clavus taken from san cristobal island galapagos islands was sectioned into 187 quarterly intervals and analyzed for 18o 13o ba ca cd ca and mn ca the resulting time series are compared with eastern pacific sea surface temperatures one of few instrumental data bases available for calibration over this time period linear least squares regressions of four of the tracers 18o 13o ba ca cd ca against peruvian sst show highly significant correlations p 0 0001 over the annual biennial and enso 3 8 years frequency bands cross spectral comparisons show even stronger coherency with sst frequently accounting for 70 80 of the variance in these tracers these results as well as the phase relationships determined from the spectral analyses suggest that the coupling between sst and 18o and the nutrientlike tracers ba and cd is controlled principally by seasonal upwelling cycles and interannual interruptions of these cycles brought about by el nino and anti el nino phenomena an inverse relationship between sst and 13c has its primary origins in the co occurrence of the warm sst phase with high light levels during the first half of the calendar year the association with sunlight derives from the photosynthetic response of algal symbionts which results in fractionation of light and heavy carbon isotopes between soft tissues and caco3 skeleton the fifth tracer the transition metal mn exhibits poorer correlations against both sst and the other tracers slight shifts in phasing of the historical mn ca annual cycle suggest that the general water column distribution of this tracer which is the reverse of a nutrient may not be stable the erratic behavior of mn illustrates how complex hydrography near galapagos may influence tracers with diverse source signatures

strontium calcium ratios in modern porites corals from the great barrier reef as a proxy for sea surface temperature calibration of the thermometer and monitoring of enso high precision sr ca ratios are reported for porites corals from davies reef at 19 s on the midshelf of the great barrier reef australia skeletal growth parameters were also determined from coral slabs using x ray photographs and densitometry measurements a calibration of the sr ca thermometer has been obtained using in situ measured sea surface temperatures which gives sr ca 10 10 48 0 01 0 0615 0 0004 t wheret is in c this calibration applies to different species of porites and a large range of annual extension and calcification rates provided sampling follows a major growth axis biases of 1 2 c have been observed in the low density margins where growth is hampered by interfering fans of corallites the analytical and the long term reproducibility of sr ca derived temperatures are both better than 0 3 c 2 coral growth parameters such as the extension rate or density generally appear to respond to environmental changes such as rainfall but do not affect the sr ca partitioning between coralline aragonite and seawater no correlation has been found between calcification rate and sr ca variations consistent with sr ca being mainly controlled by temperature in the great barrier reef the interannual variability in sst is primarily related to the el nino southern oscillation phenomenon and is typically marked by a cold anomaly during the winter preceding the mature warm phase instrumental records show that the surface waters of the coral sea around 19 s have experienced a significant cooling associated with the el ninos of 1965 1972 and 1982 1983 which the porites corals record faithfully the coral derived temperatures for the period from 1965 to 1993 show an increase of 1 3 c which has occurred mainly since 1979 this warming is larger in magnitude but consistent with the trend for the southern hemisphere land and marine temperature records which shows an increase of around 0 4 c

the skeletal geochemistry of the sclerosponge astrosclera willeyana implications for biomineralisation processes and palaeoenvironmental reconstruction abstract to investigate the controls on the geochemistry of aragonitic sclerosponge skeletons we used secondary ion mass spectrometry sims to analyse an astrosclera willeyana specimen the high spatial resolution of sims allows the independent analysis of the two key crystal structures in the skeleton i e the fused spherulites formed intracellularly and fused together at the surface of the skeleton and the epitaxial backfill deposited extracellularly at the base of the sponge tissue we analysed sr ca mg ca and ba ca across a short 5 mm transect of fused spherulites which represented several years growth we observe cyclical variations with a length of 0 1 to 0 6 mm in both sr ca and mg ca in some but not all sections of the transect the observed ranges of sr ca and mg ca over the presumed seasonal cycles are 9 5 to 11 5 mmol mol 1 and 0 6 to 1 0 mmol mol 1 respectively the annual seawater temperature range at the study site is 4 3 c so the inferred temperature sensitivity of skeletal sr ca and mg ca is 0 5 mmol mol 1 c or 5 c 1 and 0 1 mmol mol 1 c or 13 c 1 respectively this is higher than observed in most previous sclerosponge studies or anticipated from studies of synthetic aragonite this indicates that the chemistry of the a willeyana skeleton is affected by one or more additional influences besides temperature which are currently unresolved the ph of the precipitating fluid estimated from skeletal 11b is 8 1 8 2 for both fused spherulites and epitaxial backfill epitaxial backfill contains significantly higher sr ca mg ca and b ca and significantly lower ba ca than the fused spherulites but sr ca and mg ca are positively correlated by the same relationship in both skeletal features this suggests that the geochemistry of each feature is predominantly controlled by a common process this is unlikely to be rayleigh fractionation which is indicated by negative correlations between sr and mg in aragonite

intensified mid holocene asian monsoon recorded in corals from kikai island subtropical northwestern pacific abstract coupled records of sr ca and oxygen isotope ratios 18 o of coral skeletons have been used to produce quantitative estimates of paleo sea surface temperature sst and 18 o of surface seawater that can in some cases be converted to sea surface salinity sss two fossil corals from kikai island in the subtropical northwestern pacific a location affected by east asian summer and winter monsoons were analyzed to investigate differences between mid holocene and present day sst and sss at 6180 cal yr bp ssts were roughly the same as today both in summer and winter 18 o seawater and sss values were higher both in summer 0 5 1 1 psu and in winter 0 2 0 6 psu than modern values at 7010 cal yr bp ssts were slightly cooler both in summer and winter 0 8 and 0 6 c whereas 18 o seawater and sss had higher values in summer 0 3 0 6 psu and in winter 0 8 1 9 psu than present day values these results are consistent with other marine records for the mid holocene of the low and midlatitudes in the northwestern pacific such regional conditions indicate that the east asian summer and winter monsoons were more intense in the mid holocene which was likely a function of the mid holocene insolation regime

geochemistry based coral palaeoclimate studies and the potential of non traditional non massive porites corals recent developments and future progression understanding the natural variability of the earth s climate system and accurately identifying potential anthropogenic influences requires long term geographically distributed records of key climate indicators such as temperature and precipitation that extend prior to the last 400 years of the holocene reef corals provide an excellent source of high resolution climate records and importantly represent the tropical marine environment where palaeoclimate data are urgently required recent decades have seen significant improvement in our understanding of coral biomineralisation the associated uptake of geochemical proxies and methods of identifying and understanding the effects of both early and late post depositional diagenetic alteration these processes all have significant implications for interpreting geochemical proxies relevant to palaeoclimatic reconstructions this paper reviews the current state of the art in terms of coral based palaeoclimate reconstructions and highlights a key remaining problem the majority of coral based palaeoclimate research has been derived from massive colonies of porites however massive porites are not globally abundant and may not provide material of a particular age of interest in those regions where they are present therefore there is great potential for alternate coral genera to act as complimentary climate archives while it remains critical to consider five key factors vital effects differential growth morphologies geochemical heterogeneity in the skeletal ultrastructure transfer equation selection and diagenetic screening of skeletal material in order to allow the highest level of accuracy in coral palaeoclimate reconstructions it is also important to develop alternate taxa for palaeoclimate studies in regions where porites colonies are absent or rare currently as many as nine genera other than porites have proven at least limited utility in palaeothermometry most of which are found in the atlantic caribbean region where massive porites do not exist even branching taxa such as acropora have significant potential to preserve environmental archives increasing this capability will greatly expand the number of potential geochemical archives available for longer term temporal records of palaeoclimate

novel heating cooling stage designed for fluid inclusion microthermometry of large stalagmite sections liquid vapour homogenisation temperatures of fluid inclusions in stalagmites are used for quantitative temperature reconstructions in paleoclimate research specifically for this application we have developed a novel heating cooling stage that can be operated with large stalagmite sections of up to 17 35 mm2 to simplify and improve the chronological reconstruction of paleotemperature time series the stage is designed for use of an oil immersion objective and a high na condenser front lens to obtain high resolution images for bubble radius measurements the temperature accuracy of the stage is better than 0 1 c with a precision reproducibility of 0 02 c

mg ca ratios of the benthic foraminifera oridorsalis umbonatus obtained by laser ablation from core top sediments relationship to bottom water temperature 1 a laser ablation system connected to an inductively coupled plasma mass spectrometer was used to determine mg ca ratios of the benthic foraminifera oridorsalis umbonatus a set of modern core top samples collected along a depth transect on the continental slope off namibia 320 2300 m water depth 2 9 to 10 4 c was used to calibrate the mg ca ratio against bottom water temperature the resulting mg ca bottom water temperature relationship of o umbonatus is described by the exponential equation mg ca 1 528 e0 09 bwt the temperature sensitivity of this equation is similar to previously published calibrations based on cibicidoides species suggesting that the mg ca ratio of o umbonatus is a valuable proxy for thermocline and deep water temperature

a review of modern coral δ18o and δ14c proxy records abstract this paper is a review of published modern coral 18 o and 14 c isotopic records that are at least 30 and 20 years long respectively the data are presented to show basin scale trends in both of these proxy records on decadal to centennial timescales the goal was to qualitatively integrate the general inter annual to centennial timescale variability revealed in these data as well as the statistical and modeling output results that have been produced using these coral records while many review papers typically include a representative subset of the data available this review aims to include as much of the available data as possible in general coral 18 o records show a long term warming and or freshening throughout the tropical oceans and agree with the noaa extended reconstruction sea surface temperature 2 ersst on decadal timescales in the western pacific it is most likely a freshening of the seawater 18 o that dominates the signal el nino southern oscillation enso variability dominates most 18 o records either by varying local seawater temperature or salinity depending on the regional oceanography climatology outside of the pacific enso affects seawater temperature and salinity via atmospheric or oceanic teleconnections post bomb coral 14 c records collectively show that the uptake of 14 c has been greatest in gyre water fed sites followed in descending order by western boundary current areas equatorial upwelling regions and eastern tropical pacific upwelling sites these surface water 14 c values indicate the proportion of surface water and or the residence time of water at the surface at a given location and can be used to model water mass mixing rates such models have only begun to be run and show that the amount of eastern pacific water entering the central south pacific increases during el ninos and that the indonesian throughflow is supplied year round by the north pacific comparing ocean circulation models with coral 14 c modelled circulation enables researchers to explore the mechanisms that drive seawater 14 c variability and fine tune their models in addition our comparison between the rate of coral 14 c increase between 1960 and 1970 and total anthropogenic co 2 uptake rates show general agreement demonstrating the value of coral records in understanding past carbon fluxes overall coral 18 o and 14 c proxy records represent natural archives of seawater conditions and are critical for studying the natural variability in local and regional patterns within and teleconnection patterns between the tropics extra tropics temperate and polar regions on intra annual to centennial timescales

interpreting environmental signals from the coralline sponge astrosclera willeyana coralline sponges sclerosponges have been proposed as a new source for paleo subsurface temperature reconstructions by utilizing methods developed for reef building corals however unlike corals coralline sponges do not have density variations making age determination difficult in this study we examined multiple elemental rations b mg sr ba u in the coralline sponge astrosclera willeyana we also measured skeletal density profiles along the outer living edge of the sponges and this data indicates significant thickening of skeletal material over intervals of 2 3 mm or 2 3 years this suggests that any skeletal recovered environmental record from astrosclera willeyana is an integration of signals over a 2 3 year period sponge sr ca seemed to hold the most promise as a recorder of water temperature and we compared sr ca from 2 sponges in the great barrier reef and one from truk in micronesia to their respective sea surface temperature record the correlations were not that strong approx r 0 5 but they were significant it appears that the signal smoothing due to thickening or perhaps even some biologic control on sr skeletal partitioning limits the use of sr ca as an indicator of water temperature in astrosclera willeyana

fidelity of δ18o as a proxy for sea surface temperature influence of variable coral growth rates on the coral porites lutea from hainan island china 1 the extremely high temporal resolution nearly daily interval measurement was conducted on the coral porites lutea oxygen isotope compositions 18oc to examine the detailed relationship between 18oc and sea surface temperature sst and seawater oxygen isotope composition 18ow from hainan island china although sst and sea surface salinity sss or 18ow varied in a wide range at the studied site the dynamic range of 18oc recorded in coral was much smaller than expected from sst and sss 18ow changes the extremely high 30 c and low 22 c sst and low 27 sss are not suitable for coral calcification and coral could not record the information as their skeletal 18o estimated coral extension rates the overall rate is 15 mm year varied by a factor of about 18 within one year from very slow in winter to very fast in spring light availability could affect the extension rate of coral skeleton through the activity of photosynthesis of symbiont algae such cessation and acceleration of calcification cause a serious distortion of the 18o profile which makes it difficult to make a correlation between 18o and sst because high and low extension rates correspond to low and high density bands respectively a detailed examination of the density structure may assist the correction for distortion of the 18o profile

calcite filled borings in the most recently deposited skeleton in live collected porites scleractinia implications for trace element archives abstract skeletons of the scleractinian coral porites are widely utilized as archives of geochemical proxies for among other things sea surface temperature in paleoclimate studies here we document live collected porites lobata specimens wherein as much as 60 of the most recently deposited skeletal aragonite i e the part of the skeleton that projects into the layer of living polyps and thus is still in direct contact with living coral tissue has been bored and replaced by calcite cement calcite and aragonite were identified in situ using raman microspectroscopy the boring filling calcite cement has significantly different trace element ratios sr ca mmol mol 6 3 1 4 mg ca mmol mol 12 0 5 1 than the host coral skeletal aragonite sr ca mmol mol 9 9 1 3 mg ca mmol mol 4 5 2 3 the borings appear to have been excavated by a coccoid cyanobacterium that dissolved aragonite at one end and induced calcite precipitation at the other end as it migrated through the coral skeleton boring activity and cement precipitation occurred concomitantly with coral skeleton growth thus replacing skeletal aragonite that was only days to weeks old in some cases although the cement filled borings were observed in only 20 of sampled corals their occurrence in some of the most recently produced coral skeleton suggests that any corallum could contain such cements irrespective of the coral s subsequent diagenetic history in other words pristine skeletal aragonite was not preserved in parts of some corals for even a few weeks although not well documented in coral skeletons microbes that concomitantly excavate carbonate while inducing cement precipitation in their borings may be common in the ubiquitous communities that carry out micritization of carbonate grains in shallow carbonate settings thus such phenomena may be widespread and failure to recognize even very small quantities of early cement filled borings in corals used for paleoclimate studies could compromise high resolution paleotemperature reconstructions the inability to predict the occurrence of cement filled borings in coralla combined with the difficulty in recognizing them on polished blocks highlights the great care that must be taken in vetting samples both for bulk and microanalysis of geochemistry

tarbellastraea scleractinia a new stable isotope archive for late miocene paleoenvironments in the mediterranean abstract geochemical proxy records of sea surface temperature sst or sea surface salinity sss variability on intra and interannual time scales in corals from geological periods older than pleistocene are extremely rare due to pervasive diagenetic alteration of coralline aragonite very recently however stable isotope data 18o 13c from specimens of porites of late miocene age 10 ma have been shown to preserve original environmental signatures in this paper we describe new finds of the zooxanthellate corals porites and tarbellastraea in exceptional aragonite preservation from the island of crete in sediments of tortonian 9 ma and early messinian 7 ma age systematic comparative stable isotope analysis of massive tarbellastraea and porites sampled from the same beds and localities reveal identical stable isotope fractionation patterns in both genera therefore extinct tarbellastraea represents an additional environmental archive fully compatible and mutually exchangeable with porites provided that seasonal variations in 18o reflect sst changes only seasonal sst contrasts of 7 3 c for the tortonian and 4 8 c for the early messinian are inferred implying warmer summer and cooler winter ssts during the tortonian than during the messinian however reduced 18o seasonality 1 1 in the tortonian and 0 7 in the messinian and slightly less negative mean 18o in messinian corals 2 4 compared to tortonian specimens 2 7 may not necessarily indicate a long term fall in ssts but changes in surface water 18o i e global ice build up or enhanced evaporation during summer or increased precipitation river discharge during winter and changes in insolation on the other hand coral communities of tortonian and messinian age in central crete are identical and compatible annual extension rates indicate similar average ssts during the two investigated time periods in addition lithological and paleobotanical data from central crete document a change from humid to dry climatic conditions during the late miocene therefore a likely explanation for the observed shift in coral mean 18o and reduced 18o seasonality from the tortonian to the early messinian is a change in ambient seawater 18o caused by a change in the hydrological balance towards high evaporation high salinity during summer

strontium and oxygen isotopic constraints on fluid mixing alteration and mineralization in the tag hydrothermal deposit abstract strontium and oxygen isotopic measurements of samples recovered from the trans atlantic geotraverse tag hydrothermal mound during leg 158 of the ocean drilling program provide important constraints on the nature of fluid rock interactions during basalt alteration and mineralization within an active hydrothermal deposit fresh mid ocean ridge basalt morb with a 87 sr 86 sr of 0 7026 from the basement beneath the tag mound was altered at both low and high temperatures by seawater and altered at high temperature by near end member black smoker fluids pillow breccias occurring beneath the margins of the mound are locally recrystallized to chlorite by interaction with large volumes of conductively heated seawater 200 c the development of a silicified sulfide mineralized stockwork within the basaltic basement follows a simple paragenetic sequence of chloritization followed by mineralization and the development of a quartz pyrite paragonite stockwork cut by quartz pyrite veins initial alteration involved the development of chloritic alteration halos around basalt clasts by reaction with a mg bearing mixture of upwelling high temperature 300 c black smoker type fluid with a minor 300 c interaction between the wallrock and these mg bearing fluids results in the complete recrystallization of the wallrock to chlorite quartz pyrite the quartz pyrite paragonite assemblage replaces the chloritized basalts and developed by reaction at 250 360 c with end member hydrothermal fluids having 87 sr 86 sr 0 7038 similar to present day vent fluids the uniformity of the 87 sr 86 sr ratios of hydrothermal assemblages throughout the mound and stockwork requires that the 87 sr 86 sr ratio of end member hydrothermal fluids has remained relatively constant for a time period longer than that required to change the interior thermal structure and plumbing network of the mound and underlying stockwork precipitation of anhydrite in breccias and as late stage veins throughout most of the mound and stockwork down to at least 125 mbsf records extensive entrainment of seawater into the hydrothermal deposit 87 sr 86 sr ratios indicate that most of the anhydrite formed from 2 1 mixture of seawater and black smoker fluids 65 15 seawater oxygen isotopic compositions imply that anhydrite precipitated at temperatures between 147 c and 270 c and require that seawater was conductively heated to between 100 c and 180 c before mixing and precipitation occurred anhydrite from the tag mound has a sr ca partition coefficient kd 0 60 0 28 2 this value is in agreement with the range of experimentally determined partition coefficients kd 0 27 0 73 and is similar to those calculated for anhydrite from active black smoker chimneys from 21 n on the east pacific rise the 18 o so 4 of tag anhydrite brackets the value of seawater sulfate oxygen 9 5 dissolution of anhydrite back into the oceans during episodes of hydrothermal quiescence provides a mechanism of buffering seawater sulfate oxygen to an isotopically light composition in addition to the precipitation and dissolution of anhydrite within the oceanic basement during hydrothermal recharge at the mid ocean ridges

sr ca profile of long lived tridacna gigas bivalves from south china sea a new high resolution sst proxy abstract high resolution 18o and sr ca ratio profiles of a modern live caught and a fossil dead collected giant bivalve shell tridacna gigas from northern south china sea were analyzed the high resolution 18o profiles as documented in most of previous studies showed pronounced seasonal cycles and recorded the combined influence of seawater 18o and sea surface temperature the sr ca ratio profiles derived from icp oes had well defined annual cycles and significant and negative correlation with sea surface temperature while the sr ca profiles derived from la icp ms did not reveal clear annual cycles this difference was likely caused by the organics contents in t gigas shells which had a chemical composition different than caco3 crystals and a heterogeneous distribution across the shell the sampling methods and the experimental errors two calibration equations between sr ca ratios determined by icp oes of modern t gigas shell and instrumental sst were calculated based on all monthly and extremum sst data and the equation from extremum data produced better sst predictions these results suggested that the high resolution icp oes derived sr ca ratios of t gigas in the south china sea had the potential of providing a good proxy of historical sst

reproducibility of ba ca variations recorded by northeast pacific bamboo corals trace elemental ratios preserved in the calcitic skeleton of bamboo corals have been shown to serve as archives of past ocean conditions the concentration of dissolved barium basw a bioactive nutrientlike element is linked to biogeochemical processes such as the cycling and export of nutrients recent work has calibrated bamboo coral ba ca a new basw proxy using corals spanning the oxygen minimum zone beneath the california current system however it was previously unclear whether ba cacoral records were internally reproducible here we investigate the accuracy of using laser ablation inductively coupled plasma mass spectrometry for ba cacoral analyses and test the internal reproducibility of ba ca among replicate radial transects in the calcite of nine bamboo corals collected from the gulf of alaska 643 720 m and the california margin 870 2054 m data from replicate ba ca transects were aligned using visible growth bands to account for nonconcentric growth smoothed data were reproducible within 4 for eight corals n 3 radii coral this intracoral reproducibility further validates using bamboo coral ba ca for basw reconstructions sections of the ba ca records that were potentially influenced by noncarbonate bound ba phases occurred in regions where elevated mg ca or pb ca and coincided with anomalous regions on photomicrographs after removing these regions of the records increased ba cacoral variability was evident in corals between 800 and 1500 m these findings support additional proxy validation to understand basw variability on interannual timescales which could lead to new insights into deep sea biogeochemistry over the past several centuries

last interglacial coral record of enhanced insolation seasonality and seawater 18o enrichment in the ryukyu islands northwest pacific we present a calibrated high resolution 18o 16o and 13c 12c record for a well preserved last interglacial porites sp coral u th age of 127 6 ka from the sea level high stand terrace of yonaguni island japan seasonal variations in the 18o and 13c values for the fossil coral are greater than those observed in modern coral records from the same reef setting and appear to be driven by the enhanced insolation seasonality in the northern hemisphere during the last interglacial maximum the 18o enrichment of 1 1 in the fossil coral compared to the modern analogue cannot be due entirely to a reduction in sea surface temperature because corals in this region are already growing at their lower thermal limit instead most of the 18o enrichment must be due to a change in the 18o of the surface seawater probably in response to enhanced evaporation of the ocean or a higher volume flux of the kuroshio current

delta o 18 sr ca and mg ca records of porites lutea corals from leizhou peninsula northern south china sea and their applicability as paleoclimatic indicators combined seasonal to monthly resolution coral skeletal delta 18 o sr ca and mg ca records are reported for one modem and two late holocene porites lutea corals from a fringing reef at leizhou peninsula the northern coast of the south china sea scs all the profiles for the period 1989 2000 reveal annual cycles well correlated with instrumental sea surface temperatures sst and display broad peaks in summer and narrow troughs in winter reflecting seasonal growth rate variations calibration against instrumental sst yields the following equations delta 18 o 0 174 0 010 xsst degrees c 1 02 0 27 mswd 5 8 sr ca mmol mol 0 0424 0 0031 xsst degrees c 9 836 0 082 mswd 8 6 and mg ca mmol mol 0 110 0 009 xsst degrees c 1 32 0 23 mswd 55 the scatter in the mg ca sst relationship is much larger than analytical uncertainties can account for suggesting the presence of sst unrelated components in the mg ca variation calculated sr ca sst values for two later holocene porites lutea samples u series ages similar to 541 bc and similar to 487 ad respectively from the same reef suggest that sst in the scs at similar to 541 bc was nearly as warm as in the 1990s the warmest decade of the last century but at similar to 487 ad it was significantly cooler this observation is consistent with climatic data reported in chinese historic documents confirming that the sr ca sst relationship is a reliable thermometer removing the sst component in the delta 18 o variation based on calculated sr ca sst values the residual delta 18 o reflects the deviation of the holocene seawater delta 18 o from the modem value which is also a measure of the holocene sea surface salinity sss or the summer monsoon moisture level in mainland china such residual delta 18 o was close to zero at similar to 541 bc and 0 3 parts per thousand at similar to 487 ad suggesting that it was as wet as in the 1990s at similar to 541 bc but significantly drier at similar to 487 ad in mainland china which are also consistent with independent historic records calculated mg ca sst values for the two late holocene corals are significantly lower than the sr ca sst values and are also in conflict with chinese historic records suggesting that coral mg ca is not reliable proxy for sst at comparable sr ca ranges fossil corals always display negative mg ca offsets if compared with the modem coral of the same site we interpret this observation as due to preferential loss of mg during meteoric dissolution of cryptic mg calcite bearing microbialites in the exposed fossil corals microbialites mgo up to 17 sr only 100 300 ppm are ubiquitous during reef building processes and their presence in only a trace amount will have a significant impact on coral mg ca ratios without detectable influence on coral sr ca ratios c 2004 elsevier b v all rights reserved

annual cycles of u ca in coral skeletons and u ca thermometry abstract we have discovered annual variations in the 238 u 40 ca ratio of porites coral skeletons measurements were made using thermal ionization mass spectrometric techniques yielding precisions of 2 2 for 238 u 40 ca and l 2 for 88 sr 40 ca coralline aragonite subsamples weighed 2 mg enabling submillimeter sampling resolution corresponding to monthly temporal resolution the annual nature of the cycles was confirmed by comparison with annual banding observable in x radiographs for two modern and one fossil sample the amplitude of the u ca variation ranges from 6 to 23 well outside of analytical error as annual u ca cycles appear to be a general feature of primary coralline aragonite the preservation of such features will be important in identifying unaltered coral for u series dating studies u ca variations mimic and are in phase with annual variations in 88 sr 40 ca for a given fractional shift in sr ca the fractional shift in u ca is about 6 times larger for the two modern corals 238 u 40 ca is strongly anticorrelated with measured temperature suggesting that 238 u 40 ca has potential as a paleothermometer if temperature is the only significant control on coralline 238 u 40 ca we reach the following conclusions from analyses of fossil samples a vanuatu sample which grew halfway through the last deglaciation gives u ca temperatures 4 to 5 c below modern values u ca thermometry applied to published data for barbados corals indicates that 1 temperature generally correlates with sea level 2 glacial temperatures stages 2 and 4 were 4 to 6 c lower than interglacial temperatures stages 7a 5e and 1 and 3 temperatures rose from glacial to interglacial values early in the last deglaciation thermometry applied to papua new guinea corals indicates that 1 temperatures were 5 to 6 c lower than interglacial temperatures from 13 to 10 ky bp then rose to present values 9 ky bp 2 the temperature depression between 13 and 10 ky bp is consistent with low temperatures observed in vanuatu during the same time interval and 3 the papua new guinea deglacial temperature history differs from that of barbados the results generally support estimates of tropical temperatures obtained from sr ca thermometry and snow line elevation data but disagree with those based on foram transfer functions a thermodynamic model suggests that coralline 238 u 40 ca may also be sensitive to marine carbonate ion concentration raising the possibility that some of the observed glacial interglacial 238 u 40 ca variation may result from glacial interglacial carbonate ion changes however the key experiments that might establish a coralline 238 u 40 ca carbonate ion relationship have yet to be performed

coprecipitation and isotopic fractionation of boron in modern biogenic carbonates abstract the abundances and isotopic composition of boron in modern biogenic calcareous skeletons from the gulf of elat israel the great barrier reef australia and in deep sea sediments have been examined by negative thermal ionization mass spectrometry the selected species foraminifera pteropoda corals gastropoda and pelecypoda yield large variations in boron concentration that range from 1 ppm in gastropod shells to 80 ppm in corals the boron content of the biogenic skeletons is independent of mineralogical composition and is probably related to biological vital effects the 11 b values of the carbonates range from 14 2 to 32 2 relative to nbs srm 951 and overlap with the 11 b values of modern deep sea carbonate sediments 11 b 8 9 to 26 2 the variations of 11 b may be controlled by isotopic exchange of boron species in which 10 b is preferentially partitioned into the tetrahedral species and coprecipitation of different proportions of trigonal and tetrahedral species in the calcium carbonates carbonates with low 11 b values 15 may indicate preferential incorporation of tetrahedral species whereas the higher 11 b values 30 may indicate 1 1 uptake of both boron species assuming equilibrium with seawater 2 2 preferential incorporation of b oh 4 from in situ high ph internal fluids of organisms that are isolated from seawater the b content and 11 b values of deep sea sediments foraminifera tests and corals are used to estimate the global oceanic sink of elemental boron by calcium carbonate deposition as a result of enrichment of b in corals a substantially higher biogenic sink of 6 4 0 9 10 10 g yr is calculated for carbonates this is only slightly lower than the sink for desorbable b in marine sediments 10 10 10 g yr and approximately half that of altered oceanic crust 14 10 10 g yr thus carbonates are an important sink for b in the oceans being 20 of the total sinks the preferential incorporation of 10 b into calcium carbonate results in oceanic 11 b enrichment estimated as 1 2 0 3 10 12 per mil g yr the boron isotope composition of authigenic well preserved carbonate skeletons may provide a useful tool to record secular boron isotope variations in seawater at various times in the geological record the potential use of boron isotope geochemistry in skeletons as a tracer for palaeoenvironments is demonstrated in ostracoda and foraminifera from the gulf of carpentaria australia the 11 b values of glacial age buried skeletons 4 0 and 4 9 respectively are lower than that of their modern equivalents 17 6 and 13 3 respectively this may reflect a terrestrial boron isotope signature of the water in the gulf during the late quaternary when it was isolated from the ocean

multi colony calibrations of coral ba ca with a contemporaneous in situ seawater barium record abstract the coral skeleton barium to calcium ratio ba cacoral a proxy for seawater barium concentrations basw has been interpreted as a tracer of upwelling based on the characteristic nutrient like depth profile of basw however in some tropical regions such as the gulf of panama substantial influence of terrestrial runoff inputs and differences between the vertical distribution of basw and that of the major nutrients nitrate and phosphate in the upper water column can complicate the interpretation of ba cacoral as an upwelled nutrient proxy in the gulf of panama contemporaneous ba cacoral records from multiple colonies of porites lobata pavona gigantea and pavona clavus corals record a nearly twofold change in surface water basw as a 20 70 increase in skeletal ba ca with excellent correlation among ba ca records from co located colonies r 0 86 0 99 these results provide for the first time an absolute calibration of the coral ba proxy with a contemporaneous basw record compiling the ba cacoral records from three co located colonies of each species into taxon specific composite regressions reveals strong statistically significant correlations with the basw time series record p

sr ca and δ18o seasonality in a porites coral from the mis 9 339 303 ka interglacial abstract past changes in the seasonal distribution of insolation across the earth s surface are thought to play a critical role in quaternary climate cycles in this study we use sr ca and 18 o as geochemical proxies in the skeleton of a fossil porites coral to reconstruct the seasonal cycle of sea surface temperature sst at henderson island southeast pacific 24 s 128 w during the marine isotope stage mis 9 interglacial 339 303 ka previously published closed system u series ages provide broad age constraints for the timing of reef growth for this unit on henderson island ranging between 334 and 306 ka we apply published 18 o sst slope relationships to the stacked 18 o annual cycle in the fossil porites and find the amplitude of the seasonal cycle of sst recorded by the mis 9 coral to be 4 1 0 57 c which agrees within error with the modern seasonal cycle of sst 4 1 c sr ca sst slope relationships applied to the fossil porites stacked sr ca annual cycle suggest the amplitude of the seasonal cycle of sst was 4 7 0 75 c exceeding the modern cycle by 15 but within error of the modern value taken together these results suggest the seasonal cycle of sst at henderson island during mis 9 equaled or exceeded the modern amplitude using modern latitudinal relationships between insolation seasonality and sst seasonality we present a new application for sst amplitudes reconstructed from fossil corals that can be used in conjunction with u series ages to provide additional geochronological constraints on the development of open ocean interglacial reefs

the non tropical coral cladocora caespitosa as the new climate archive for the mediterranean high resolution weekly trace element systematics abstract high resolution weekly laser ablation icp ms trace element analyses b sr u mg ba are reported for the scleractinian coral cladocora caespitosa collected from the northern adriatic sea geochemical ratios sr ca b ca mg ca u ca ba ca were measured in a 38 mm long 10 years growth external coralline portion wall region and generally exhibit a close relationship with the in situ measured weekly fortnightly data on sea surface temperature sst available for the last 6 years in particular b ca ratios tuned to fine scale variations in sst show a high degree of correlation r 0 856 n 136 with sst and indicate that coral calcification only occurs above a minimum temperature threshold of 14 16 c in addition the ranges of trace element variability are larger than those typically recorded in tropical corals consistent with the large seasonal variations in sst of the adriatic this study thus demonstrates the feasibility of extracting and exploiting high resolution geochemical records from non tropical corals such as c caespitosa as a proxy for sst

coral record of equatorial sea surface temperatures during the penultimate deglaciation at huon peninsula uplifted coral terraces at huon peninsula papua new guinea preserve a record of sea level sea surface temperature and salinity from the penultimate deglaciation remnants have been found of a shallow water reef that formed during a pause similar to the younger dryas in the penultimate deglaciation at 130 000 2000 years ago when sea level was 60 to 80 meters lower than it is today porites coral which grew during this period has oxygen isotopic values and strontium calcium ratios that indicate that sea surface temperatures were much cooler 22 2 c than either last interglacial or present day tropical temperatures 29 1 c these observations provide further evidence for a major cooling of the equatorial western pacific followed by an extremely rapid rise in sea level during the latter stages of termination ii

non river flood barium signals in the skeletons of corals from coastal queensland australia abstract two corals from coastal queensland cow and calf islands and orpheus island have been analysed for a suite of trace elements by laser ablation icp ms la icp ms barium signals in these two corals are anomalous in comparison with ba behaviour seen in other near shore corals from this region the two corals display large sharp peaks in spring which do not correlate with markers of river discharge y ca and fluorescence this ba pattern contrasts with normal behaviour characterised here by the patterns previously published for two other coastal queensland corals king reef and pandora reef which display ba peaks in summer associated with flooding of nearby rivers 1 d j sinclair m t mcculloch corals record low mobile barium concentrations in the burdekin river during the 1974 flood evidence for limited ba supply to rivers palaeogeogr palaeoclimatol palaeoecol 214 1 2 2004 155 174 similarities are observed between the anomalous ba in the queensland corals and other published patterns of ba behaviour in corals from south africa and the arabian sea this non river flood ba behaviour is characterized by large sharp spikes of ba which are resistant to oxidative cleaning and form a continuous horizon within the coral curiously not all corals from a region display anomalous ba behaviour despite being in similar environments the timing of anomalous ba is consistent within a coral but may vary from one location to the next anomalous ba spikes are too large to be caused by ba rich upwelling and no single environmental forcing function seems to be able to account for their timing this combination of observations argues against an exogenous abiotic source for the anomalous ba signal instead it may result from a biological event triggered by a combination of environmental parameters three hypotheses are presented and critically tested against the observations barite inclusion following phytoplankton blooms decaying blooms of the blue green algae trichodesmium and physiological perturbations associated coral mass spawning none of the three hypotheses are fully consistent with all of the observations and it is concluded that no satisfactory explanation currently exists for the anomalous ba spikes

strontium in coral aragonite 2 sr coordination and the long term stability of coral environmental records we have used x ray diffraction xrd and sr k edge extended x ray absorption fine structure exafs to determine the structural state of sr in a suite of coral aragonite samples our samples encompassed a selection of coral species porites lobata porites lutea pocillopora eydouxi montastrea annularis pavona gigantea and pavona clavus including some commonly used for palaeoenvironmental reconstruction aragonite was the only carbonate observed by xrd we refined the isolated exafs against structural models for sr in aragonite and two phase strontianite aragonite mixes our data are indistinguishable from sr ideally substituted in aragonite and strontianite was present below detection levels estimated at 5 of sr present comparisons of recent and ancient coral aragonite show no sign of exsolution either by spinodal decomposition or by the direct nucleation of strontianite domains published diffusion rates of sr in ionic solids support the view that exsolution would occur prohibitively slowly coral aragonites are metastable materials with slow diffusion kinetics that have the potential to encode environments over timescales of millions of years

high frequency winter cooling and reef coral mortality during the holocene climatic optimum a detailed ecological micro structural and skeletal sr ca study of a 3 42 m thick goniopora reef profile from an emerged holocene reef terrace at the northern south china sea reveals at least nine abrupt massive goniopora stress and mortality events occurred in winter during the 7 0 7 5 thousand calendar years before present cal ka bp within the holocene climatic optimum whilst calculated sr ca sst sea surface temperature maxima during this period are comparable to those in the 1990s sr ca sst minima are significantly lower probably due to stronger winter monsoons such generally cooler winters superimposed by further exceptional winter cooling on inter annual to decadal scales may have caused stress and mortality of the corals about every 50 years sea level rose by similar to 3 42 m during this period with present sea level reached at similar to 7 3 ka bp and a sea level highstand of at least similar to 1 8 m occurred at similar to 7 0 ka the results show that it took about 20 25 years for a killed goniopora coral reef to recover c 2004 elsevier b v all rights reserved

sea surface temperature variability in the 16th century at bermuda inferred from coral records abstract records of skeletal 18 o in monthly and sr ca ratios in half yearly resolution were obtained from a bermuda coral diploria labyrinthiformis for the time period 1520 1603 15 yr ad within the little ice age annual and decadal averages of both sea surface temperature proxies indicate temperature variabilities of 0 5 c standard deviation and 0 3 c respectively both numbers are close to recent instrumental observations approximately 30 of the interannual time series variance of 18 o is concentrated in broad bands centered at periods of 30 16 and 7 8 yr the last two reflecting the influence of the north atlantic oscillation although this large scale climate signal is present in the record there is no correlation with other contemporaneous northern hemisphere proxy data resulting from spatial differences in climate variability

porites corals as recorders of mining and environmental impacts misima island papua new guinea abstract in 1989 open cut gold mining commenced on misima island in papua new guinea png open cut mining by its nature causes a significant increase in sedimentation via the exposure of soils to the erosive forces of rain and runoff this increased sedimentation affected the nearby fringing coral reef to varying degrees ranging from coral mortality smothering to relatively minor short term impacts the sediment associated with the mining operation consists of weathered quartz feldspar greenstone and schist these rocks have distinct chemical characteristics rare earth element patterns and high abundances of manganese zinc and lead and are entering the near shore environment in considerably higher than normal concentrations using laser ablation inductively coupled plasma mass spectrometry la icp ms we analyzed eight colonies two from high sedimentation two transitional two minor and two unaffected control sites for y la ce mn zn and pb all sites show low steady background levels prior to the commencement of mining in 1988 subsequently all sites apart from the control show dramatic increases of y la and ce associated with the increased sedimentation as well as rapid decreases following the cessation of mining the elements zn and pb exhibit a different behavior increasing in concentration after 1989 when ore processing began and one year after initial mining operations elevated levels of zn and pb in corals has continued well after the cessation of mining indicating ongoing transport into the reef of these metals via sulfate rich waters rare earth element ree abundance patterns measured in two corals show significant differences compared to coral sea seawater the corals display enrichments in the light and middle rees while the heavy rees are depleted relative to the seawater pattern this suggests that the nearshore seawater ree pattern is dominated by island sedimentation trace element abundances of misima island corals clearly record the dramatic changes in the environmental conditions at this site and provide a basis for identifying anthropogenic influences on corals reefs

the coral record of last interglacial sea levels and sea surface temperatures abstract the rise and fall of the last interglacial li sea levels and sea surface temperatures ssts are evaluated using u series dating combined with sr ca ratios in corals from both stable and tectonically uplifted sites along the stable coastal margin of western australia an extensive series of li coral reefs occur at heights of 2 3 m above present day sea level these corals have a very tight cluster of 234u 230th ages ranging from 129 1 to 119 1 ka as well as a narrow range of initial 234u values of 150 5 similar to modern seawater bahamas which is also a stable site has an essentially identical pattern of u series ages from 130 1 to 120 1 ka barbados and huon peninsula are tectonically active sites where the li terraces are found at elevations of 50 and 200 m respectively u series ages from corals exposed in the lower footwall of these uplifted reefs allow better constraints to be placed on the rate of sea level rise which initiated the li corals from the huon peninsula constrain sea level at 80 10 m at 131 2 ka and from barbados at 30 5 m at 129 1 ka combined with constraints from stable sites these observations require an exceedingly rapid rise in sea level of 30 50 m per 1000 years at 130 1 ka this indicates that large scale catastrophic melting of the once massive continental ice sheets occurred in phase with the rapidly increasing northern hemisphere nh summer insolation consistent with the orbital forcing being the main driver of glacial interglacial climate change there is also some evidence from huon peninsula although still not conclusive for a precursor oscillation in sea level during the penultimate deglaciation that may have been within 20 m of present day levels at 135 ka ssts for the li porites corals from the huon peninsula and western australia have mean annual temperatures and seasonal ranges that are remarkably similar to present day patterns the tropical site of huon peninsula has ssts of 29 1 c which is indistinguishable from the ssts given by modern corals at ningaloo reef in western australia similar mean annual 24 c and summer maximum ssts of 27 29 c are found in both li and modern corals the only significant difference is the 1 c cooler winter minimum ssts of 21 c for the li compared to present day minimums of 22 c li ssts from these southern hemisphere sh sites were thus very similar or at most only slightly cooler than today despite sea levels being up to 4 m higher this maybe indicative of asymmetric warming of the earth with the increased nh insolation during the li period being responsible for the extensive melting of the mainly nh based ice sheets and hence higher global sea levels the observation of relatively high sea levels in the li together with the rapid pulses of sea level rise indicates that the potential now exists for greenhouse warming to initiate increases in sea level of at least several metres on relatively short time scales 102 years

high temporal resolution mg ca and ba ca records in modern porites lobata corals 1 secondary ion mass spectrometry sims was used to determine mg ca and ba ca variations across two skeletal structures the fasciculi and the centers of calcification cocs in two porites lobata corals of different linear extension rates from oahu hawaii both corals exhibit large mg and ba heterogeneity which is not related to sea surface temperature sst or composition higher concentrations of ba occur in the fasciculi and higher mg in the cocs of the slowly extending coral compared to the fast growing coral mg and ba concentrations are significantly higher in the cocs of both corals compared to the fasciculi trace element variations may reflect changes in the calcifying fluid composition or changes in skeletal trace element incorporation regressions between mg ba and sr reported in a prior publication indicate that the skeletal incorporation of each element is affected by a different factor or combination of factors smoothed sims records of ba ca variations across the fasciculi of the fast growing coral follow the seasonal trend predicted from sst and expected seawater chemistry variations smoothed sims mg ca records do not correlate with sst indicating that sims mg ca records cannot be used to estimate past ssts

determination of intratest variability of trace elements in foraminifera by laser ablation inductively coupled plasma mass spectrometry 1 we have developed a technique to determine the variability of trace elements including li b na mg mn cu zn sr and ba within foraminifera tests using laser ablation inductively coupled plasma mass spectrometry la icp ms this technique has a high spatial resolution width 40 80 m depth 0 5 m is reproducible 8 external reproducibility and has low detection limits generally 0 05 g g 1 we demonstrate that normalization of data to a calcite standard usually gives results that are more consistent with solution icp ms data than normalization to nist 612 rastering into the wall of the final chamber of globigerinoides sacculifer shows that the outermost 1 5 m of the test is enriched in trace elements including mn relative to the interior indicating the presence of a contaminant surface phase pustule calcite close to the aperture of globorotalia tumida has different sr ca and ba ca compared to other parts of the test sr ca and ba ca partition coefficients suggest that the pustule calcite is diagenetic and or formed in a more open system multiple analyses of orbulina universa tests recovered from a latitudinal transect in the north atlantic give a relationship between mg ca and sea surface temperature similar to that reported elsewhere in the literature these initial data demonstrate the validity of this technique and show that it is potentially an extremely powerful microanalytical tool for palaeoceanographic and palaeontological studies

sea surface temperature and salinity reconstruction from coral geochemical tracers massive scleractinian corals secrete an aragonitic skeleton which incorporates a large array of chemical tracers corals present several advantages for palaeoclimate research they grow continuously and can live up to 1000 years they are easy to date and they can be sampled at high resolution weekly to monthly resolution both live and fossil corals can be collected in the field in the past two decades significant efforts have been made to identify robust tracers of sea surface temperature sst and salinity sss in corals to date sr ca and 18o are considered to be the most reliable sst tracers although changes in seawater 18o can significantly alter sst reconstructed from coralline 18o because these variations in seawater 18o can be linked to sss changes this initial problem can in fact be turned into an advantage and provide us with an sss tracer the sst component in the coral 18o signal can either be evaluated through sr ca measurements or in some case simply filtered out however there is still much uncertainty concerning the exact mode of incorporation of trace elements and stable isotopes into the coral skeleton the effects of growth rate light intensity feeding habits ph and water chemistry are still poorly documented a review of the strength and weaknesses of sr ca and 18o is presented together with some examples of sst and sss reconstructions other potential sst tracers are also reviewed it is expected that the ability to grow corals in aquarium under controlled conditions and that the development of sophisticated analytical techniques at the micrometric level should help us understand better the robustness of each tracers and the factors controlling their incorporation in coral aragonite

corals record low mobile barium concentrations in the burdekin river during the 1974 flood evidence for limited ba supply to rivers porites corals collected from two coastal locations in the great barrier reef gbr of australia have been analysed for trace elements by laser ablation icp ms and fluorescence by photographic techniques the sites were selected because they experience freshwater discharge from nearby river systems pandora reef from the burdekin river king reef from several rivers including the tully river the analyses spanned approximately 6 years from the late 1960s to mid 1970s and included the year 1974 which is the largest recorded flood of the burdekin river both corals display large enrichments in ba ca by up to 4 which coincide with the timing of river flood plumes as indicated by the luminescent flood bands from these observations it is inferred that peaks in coralline ba are caused by ba desorbing from suspended sediment in the low salinity region of the flood plume and being taken up by the coral as a dissolved component the effective river end member ba concentration ba erem for floods from both the burdekin and tully rivers are calculated from ba ca anomalies in the corals and salinity models generated by the australian institute of marine sciences aims the ba erems in the pandora reef coral are negatively correlated with river discharge especially notable is the very low erem for the 1974 burdekin river flood 226 13 nm ba erems are more variable in the king reef coral reflecting a complex mix of freshwaters from several rivers the 1974 event however is dominated by freshwater from the burdekin river and the erem determined from ba in the king reef coral 196 20 nm is identical to that calculated from the pandora coral the low erem for the large 1974 flood and the negative trend with discharge suggest that the supply of mobile dissolved and labile particulate ba to the burdekin river may be limited

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

relationship between water and aragonite barium concentrations in aquaria reared juvenile corals abstract coral barium to calcium ba ca ratios have been used to reconstruct records of upwelling river and groundwater discharge and sediment and dust input to the coastal ocean however this proxy has not yet been explicitly tested to determine if ba inclusion in the coral skeleton is directly proportional to seawater ba concentration and to further determine how additional factors such as temperature and calcification rate control coral ba ca ratios we measured the inclusion of ba within aquaria reared juvenile corals favia fragum at three temperatures 27 7 24 6 and 22 5 c and three seawater ba concentrations 73 230 and 450 nmol kg 1 coral polyps were settled on tiles conditioned with encrusting coralline algae which complicated chemical analysis of the coral skeletal material grown during the aquaria experiments we utilized sr ca ratios of encrusting coralline algae as low as 3 4 mmol mol 1 to correct coral ba ca for this contamination which was determined to be 26 11 using a two end member mixing model notably there was a large range in ba ca across all treatments however we found that ba inclusion was linear across the full concentration range the temperature sensitivity of the distribution coefficient is within the range of previously reported values finally calcification rate which displayed large variability was not correlated to the distribution coefficient the observed temperature dependence predicts a change in coral ba ca ratios of 1 1 mol mol 1 from 20 to 28 c for typical coastal ocean ba concentrations of 50 nmol kg 1 given the linear uptake of ba by corals observed in this study coral proxy records that demonstrate peaks of 10 25 mol mol 1 would require coastal seawater ba of between 60 and 145 nmol kg 1 further validation of the coral ba ca proxy requires evaluation of changes in seawater chemistry associated with the environmental perturbation recorded by the coral as well as verification of these results for porites species which are widely used in paleo reconstructions

climatic constraints on growth rate and geochemistry sr ca and u ca of the coral siderastrea stellata in the southwest equatorial atlantic rocas atoll brazil although relatively rare compared to similar latitudes in the pacific or indian oceans massive coral colonies are present in the tropical equatorial southwestern atlantic ocean however detailed geochemical compositions of these corals are still largely unknown in this work we present growth rates sr ca and u ca ratios of the coral colony siderastrea stellata sampled at rocas atoll off the brazilian coast these variables are primarily affected by sea surface temperature sst at seasonal scale and by wind stress at interannual scale these results represent a broad new finding a lower significance at the interannual time scale between sr ca and u ca with respect to sst is attributed to the low sst amplitude closed to equator an investigation on the dependence of coral growth rates with respect to the cloud shading effect promoted by the intertropical convergence zone itcz does not show significant influence additionally rain seems to act on local geochemistry of sr ca ratios and growth rate at the decadal scale

high resolution coral cd measurements using la icp ms and id icp ms calibration and interpretation abstract cadmium cd concentrations in coral skeleton track oceanic upwelling which brings cd rich deep water to the surface in this study we report sub monthly measurements of cd coral measured via laser ablation inductively coupled plasma mass spectrometry la icp ms in three species of coral porites lobata pavona gigantea and pavona clavus from an upwelling site in the gulf of panama although single la tracks in all species yielded variable results the average of multiple tracks mirrored changes in in situ seawater cd cd sw with an offset between peaks in addition cd coral determined by la icp ms and isotope dilution id icp ms was compared in p clavus and found to be highly correlated despite consistently lower concentrations measured using the id method two 5 5 month long high resolution p clavus cd coral records revealed that the maximum cd coral values occurred after the sea surface temperature minimum at the same time as the seawater phosphate concentration and coral p ca maximum and approximately one month before peak cd sw based on these findings we hypothesize that corals are actively taking up cd and incorporating it into their skeleton and that cd sw only increases once cd is no longer being rapidly removed from the water column via biological processes after accounting for a 1 month offset between the coral and seawater cd maxima both la and id derived cd coral values were significantly correlated to cd sw providing a calibration for this cd sw proxy in p clavus a three year high resolution p clavus la cd coral record demonstrated the potential of cd coral to generate a high resolution cd sw record however due to the natural variability in high resolution la icpms cd coral values within and among coral colonies three laser tracks per colony and at least three colonies of p clavus need to be analyzed to produce a reliable coral cd coral record

twentieth century warming of the tropical atlantic captured by sr u paleothermometry coral skeletons are valuable archives of past ocean conditions however interpretation of coral paleotemperature records is confounded by uncertainties associated with single element ratio thermometers including sr ca a new approach sr u uses u ca to constrain the influence of rayleigh fractionation on sr ca decarlo et al 2016 here we build on the initial pacific porites sr u calibration to include multiple atlantic and pacific coral genera from multiple coral reef locations spanning a temperature range of 23 15 30 12 c accounting for the wintertime growth cessation of one bermuda coral we show that sr u is strongly correlated with the average water temperature at each location r2 0 91 p 0 001 n 19 we applied the multi species spatial calibration between sr u and temperature to reconstruct a 96 year long temperature record at mona island puerto rico using a coral not included in the calibration average sr u derived temperature for the period 1900 1996 is within 0 12 c of the average instrumental temperature at this site and captures the 20th century warming trend of 0 06 c per decade sr u also captures the timing of multi year variability but with higher amplitude than implied by the instrumental data mean sr u temperatures and patterns of multi year variability were replicated in a second coral in the same grid box conversely sr ca records from the same two corals were inconsistent with each other and failed to capture absolute sea temperatures timing of multi year variability or the 20th century warming trend our results suggest that coral sr u paleothermometry is a promising new tool for reconstruction of past ocean temperatures

ostracod shell chemistry as proxy for paleoenvironmental change abstract the application of ostracod shell chemistry as a paleoenvironmental tool has grown within the past decades most studies have investigated mg and sr in ostracod shells as proxies for temperature and salinity and the use of a wide range of trace elements as prospective paleoenvironmental indicators has yet to be developed for lacustrine systems only a few preliminary studies have used trace metals in paleolimnological studies such as cd ba and zn as paleonutrient indicators or mn fe and u as redox and oxygenation indicators this paper reviews the state of the art of geochemical analyses in microfossils such as ostracods foraminifera and corals and provides insights in new trace element proxies with the goal to promote the use of trace elements in ostracod shells as paleoenvironmental proxies in paleoceanography foraminifera and corals are most prominently used to reconstruct past climate conditions well established proxies such as 18o mg ca and sr ca provide information about changes in sea surface temperatures in addition a great number of new proxies have been developed recently such as radiogenic isotopes and redox sensitive trace elements in paleolimnology ostracod shell chemistry is widely used to assess paleohydrological changes reconstruction of temperature and salinity changes in lake environments is often achieved by oxygen isotopes as well as mg ca and sr ca ratios but depending on the hydrological and geological settings of the lake system local calibrations are needed to assess which proxy is suited to reflect which processes new proxies need to be tested by novel techniques that recently have become available compared to conventional instrumentation used in ostracod shell chemistry methods such as laser ablation icp ms and nanosims allow single shell analysis and provide high resolution data the potential of ostracods in paleolimnology is not yet fully assessed but can be developed by learning from paleoceanographic studies

acme and demise of the late palaeozoic ice age a view from the southeastern margin of gondwana abstract palaeoenvironmental reconstructions from across the globe indicate that the climatic and oceanographic changes that accompanied the permian transition from deep icehouse to greenhouse conditions were uneven and asynchronous because of a paucity of well constrained data environmental changes in gondwana remain poorly understood relative to tropical pangaea in this regard the permian system of eastern australia provides a unique record of this transition along a high latitude open marine shelf not only was glaciation protracted here relative to other regions of gondwana but the record also spans temperate to polar palaeolatitudes providing an opportunity to examine environmental changes along a latitudinal transect we integrate proxies for 18oseawater palaeotemperature pco2 and depositional environment to assess the evolution of nearshore conditions through the permian glaciation was not continuous but rather focused into four discrete glacial epochs p1 p4 each several million years in length which alternated with nonglacial intervals of similar duration during the asselian mid artinskian p1 p2 time uniform conditions along the full extent of the margin were maintained by a cold boundary current coupled with oceanic upwelling increased spatiotemporal variability is evident at the end of glacial p2 mid artinskian perhaps due to tectonic changes that impacted the palaeogeography of the margin although glaciers had disappeared by this time elsewhere in gondwana eastern australia saw two additional periods of glaciation p3 roadian earliest captianian and p4 early wuchiagingian continued albeit intermittent glaciation was facilitated by drift toward higher palaeolatitudes orogenic activity that led to the development of areas of high elevation that could serve as nucleation points for glaciers and transient drops in atmospheric pco2 variations in meltwater input exerted a strong effect on local 18oseawater values complicating attempts to reconstruct latitudinal gradients in palaeotemperature results point to atmospheric co2 as the primary driver responsible for the dynamic climate variations evident in the record

boron isotopic compositions of corals seawater or diagenesis record abstract the first analyses of modern and fossil corals calcite free using a positive ion cs2bo2 tims technique and a chemical procedure for b extraction are reported the 11b for modern corals fluctuates between 23 3 and 25 5 the range of variation of fossil corals from the last interglacial period is greater from 23 5 to 27 3 and the lowest 11b corresponds to the corals close to last glacial maximum boron concentrations show a variation from 49 to 58 ppm in the recent corals and from 39 to 52 ppm in ancient corals for the ancient corals linear correlations are observed in both 11b vs b concentration and 11b vs 1 b plots but these correlations are not observed for modern corals two interpretations are presented to account for these observations and to test the potential of 11b for reconstructing paleo ocean ph the first interpretation assumes a thermodynamic partitioning of b between seawater and carbonates and shows that both boron isotopic compositions and concentrations can be used to calculate the ph of seawater in which corals grow for our data such a model requires that both the ph and the co2 of the deglacial ocean was lower than present day values the second interpretation is based on the correlation observed for ancient corals between boron isotopic compositions and 1 b we suggest that the measured boron isotopic compositions of ancient corals are caused by the mixing of a primary aragonite the coral skeleton and secondary aragonite precipitated from 10b enriched reef pore fluids the characteristics 11b and b concentrations of the diagenetic aragonite and the fluids from which it precipitates can be constrained if this proves correct only the non recrystallised parts of ancient corals can be used for paleo ph reconstructions these recrystallisation processes did not affect the 234u 238u ratios of the corals

seasonal changes in sea surface temperature and salinity during the little ice age in the caribbean sea deduced from mg ca and 18o 16o ratios in corals abstract the oxygen isotopic composition 18 o of coral skeletons reflects a combination of sea surface temperature sst and the 18 o of seawater which is related to sea surface salinity sss in contrast the magnesium calcium mg ca ratio of a coral skeleton reflects sst independent of salinity by using the relationships among coral mg ca ratios coral 18 o seawater 18 o and sst it is possible to determine past sst and sss uniquely such determinations were made and calibrated using the mg ca ratio and the 18 o of the modern part of a 3 m long coral core montastrea faveolata collected from the southwest coast of puerto rico in the caribbean sea where both sst and sss changes seasonally and the seawater 18 o measured at the coral site our results yielded three relationships coral mg ca sst 18 o coral 18 o water sst and 18 o water sss with these calibration equations seasonal changes in sst and sss during the little ice age lia in the caribbean sea were reconstructed the 18 o and mg ca ratio of the coral skeleton between 1699 and 1703 suggests that the sst during the lia was approximately 2 c cooler than present with the sss showing greater seasonal changes as well these results are in good agreement with climate based reconstruction from corals based on oxygen isotopes although the possibility of some uncertainty remain in our estimation including long term decadal scale trends in climate

the temperature relationship in coralline aragonite influence of variability in and skeletal growth parameters this paper provides an evaluation of two of the most likely pitfalls of sr ca thermometry i e the effect of biogenic cycling of sr vs ca in the surface ocean and the effect of variable extension rate on sr incorporation in coralline aragonite the authors also report calibration of the sr ca temperature relationship for three coral species porites lobata pocillopora eydouxi and pavona clavus collected for the hawaiian and galapagos islands analyses of seawater samples show significant spatial and depth variability in the sr ca ratio the uncertainty introduced by this effect is estimated to be 0 2 degrees c for corals located in tropical oligotrophic waters and potentially larger for corals located in upwelling areas sr ca along two different growth axes of a galapagos pavona clavus with annual extension rates of approximately 6 and 12 mm y respectively indicate an offset of 1 2 degrees c with higher sr ca values associated with slower extension rates the offset observed between the two growth axes may be the result of variations in extension and or calcification rate these results are important in determining past sea surface temperatures for reconstruction of paleoclimates

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

a high resolution sr ca and δ18o coral record from the great barrier reef australia and the 1982 1983 el nino abstract a high resolution near weekly sr ca and oxygen isotopic record is presented for a coral from the pandora reef in the great barrier reef gbr of australia during the period 1978 to 1984 the records are well correlated except for periods of high rainfall when river runoff has significantly modified the 18o value of seawater using the sr ca temperature calibration of de villiers et al 1994 the sr ca records exhibit seasonally controlled cyclical sst sea surface temperature variations of from 21 to 28 c during the very strong el nino of 1982 1983 the sr ca systematics indicate a sharp drop in the winter sst to 18 5 c this represents a temperature anomaly of 3 c which is approximately twice that given by the 18o variations suggesting an 2 amplification of the anomaly by the sr ca system possibly due to the increasing dominance of inorganically controlled aragoniteseawater fractionation the oxygen isotopic systematics show the combined effects of both temperature and changing seawater 18o values the latter reflecting the influx of 18o depleted runoff during periods of high rainfall due to the extremely low 10 3 sr and ca contents of river run off relative to seawater it is possible to use the sr ca thermometer to calculate temperatures independent of major floods and hence deconvolve the combined effects in the oxygen isotopic record of variable temperature and the 18o value of seawater using this approach it is possible to quantitatively reproduce the volume of runoff from the burdekin river during the periods of major flooding that occurred in early 1979 and 1981 the results of this study demonstrate that the combined use of high resolution sr ca and 18o systematics in scleractinian corals is a powerful tool for providing quantitative constraints on past climate

coral climate proxy data from a marginal reef area kuwait northern arabian persian gulf we present the first coral climate proxy data sr ca 18o 13c from the persian arabian gulf using a porites lutea coral collected offshore kuwait both oxygen isotope and sr ca ratios of the coral core investigated are statistically correlated with instrumental sea surface temperatures sst for the area from 1980 2002 however the temperature calibration curve for sr ca differs from other published curves in that its slope is much lower the correlation coefficient between 18ocoral and instrumental sst is at the lower limit as compared to other sites these differences most likely relate to insufficient data representation of cold winters and hot summers and indicates that much higher sampling resolution is needed in marginal reef areas such as kuwait with extreme environmental fluctuations i e intra annual sst variation of 16 34 c as compared to low latitude locations with relatively low sst variation variations of carbon isotopes of the coral skeleton do not exhibit climate control however a negative excursion in 1991 might be attributed to the massive oil field fires of the ii gulf war

coral barium calcium record of mid holocene upwelling activity in new caledonia south west pacific abstract a variety of inimical factors i e sea surface temperature nutrient input nature of substrates were invoked previously to explain the retardation in reef settlement in new caledonia during the holocene in order to clarify the respective role played by temperature and nutrient level in the growth of fringing reefs along the southwest coast of the island trace element ratios i e sr ca and ba ca were used respectively as a paleothermometer and as a tracer of nutrient load from modern and mid holocene about 6000 calendar years old massive porites coral colonies the results obtained from the modern coral record indicate that near the outer barrier reef upwelling activity is controlled by southeast winds blowing in summer by contrast along the southwest coastline the fringing reefs are subjected to barium input mainly derived from weathering of barite rich rocks cropping out in the adjacent mainland comparison between the fossil and modern coral sr ca and ba ca records shed light on three different aspects of the mid holocene climate and coral reef evolution in new caledonia 1 the variability of paleo sea surface temperature sst seems to have been similar to the modern one although the island probably experienced sst about 1 c higher than at present 2 upwelling activity appears to have been greater than at present barium being supplied from the open sea to coastal zones by strong wind generated upwelling currents in relation to cooling events 3 the onset of reef development in the southwest areas of new caledonia was delayed due to the stronger upwelling of nutrient enriched waters during the early middle holocene the flowing of upwelled waters over the southwest coastal areas began at 8200 calendar years bp and ceased at the time when the outer barrier reef crest reached present day sea level about 5500 to 5000 calendar years ago

corals at their latitudinal limits laser ablation trace element systematics in porites from shirigai bay japan the rapid analytical technique of laser ablation inductively coupled plasma mass spectrometry la icp ms was used to measure the trace elements b mg sr ba and u in a high latitude coral colony porites lobata taken from shirigai bay japan 32 n a wide range of sea surface temperatures ssts 14 5 28 c and upwelling events influenced this coral cold winter ssts caused a decrease and or cessation of skeletal extension measurements of u ca and sr ca indicate an approximately linear response to ssts above 18 c and a non linear response below 18 c mg ca and b ca measurements both showed annual cycles broadly consistent with sst variations but also exhibited intra annual fluctuations not associated with temperature suggesting that the incorporation of mg and b into the coral skeleton was not simply regulated by temperature it is shown that ba ca ratios provide a proxy for wind induced seasonal upwelling this is inferred from the strong correlations between the strength of zonal winds 1 month prior to the sst minimum and the ba ca maximum secondary upwelling events occurred during the summers of 1982 1987 1991 and 1992 these summers were cooler than average and were associated with el nino southern oscillation events

coral ba ca molar ratios as a proxy of precipitation in the northern yucatan peninsula mexico the yucatan peninsula consists of a karstic terrain that allows the aquifer to directly recharge from rainfall due to the various dissolution precipitation reactions occurring during groundwater flow the groundwater discharge in the coastal zone becomes a source of trace elements including ba the aim of this study was to use the coralline ba ca record as a proxy of precipitation under the consideration that rainfall rates vary at inter annual time scales annual ba ca ratios both the total content ba catc and the ca substitutive fraction ba cacaf were quantified in a 52 a old coral colony of montastraea annularis from the punta nizuc reef mexican caribbean average ba catc 5 90 0 56 lmol mol was 20 higher than ba cacaf 4 85 0 33 lmol mol indicating that ba is also incorporated in other fractions correlation between annual precipitation and ba catc time series is significant r 0 77 p 0 05 allowing the use of the ba catc ratio as a proxy of precipitation and hence enabling the reconstruction of precipitation patterns through time likewise the ba cacaf ratio can be used for the reconstruction of dissolved ba in coastal seawater 2012 elsevier ltd all rights reserved

brucite microbialites in living coral skeletons indicators of extreme microenvironments in shallow marine settings brucite mg oh 2 microbialites occur in vacated interseptal spaces of living scleractinian coral colonies acropora pocillopora porites from subtidal and intertidal settings in the great barrier reef australia and subtidal montastraea from the florida keys united states brucite encrusts microbial filaments of endobionts i e fungi green algae cyanobacteria growing under organic biofilms the brucite distribution is patchy both within interseptal spaces and within coralla although brucite is undersaturated in seawater its precipitation was apparently induced in the corals by lowered pco2 and increased ph within microenvironments protected by microbial biofilms the occurrence of brucite in shallow marine settings highlights the importance of microenvironments in the formation and early diagenesis of marine carbonates significantly the brucite precipitates discovered in microenvironments in these corals show that early diagenetic products do not necessarily reflect ambient seawater chemistry errors in environmental interpretation may arise where unidentified precipitates occur in microenvironments in skeletal carbonates that are subsequently utilized as geochemical seawater proxies

uranium uptake history open system behaviour and uranium series ages of fossil tridacna gigas from huon peninsula papua new guinea abstract molluscs incorporate negligible uranium into their skeleton while they are living with any uranium uptake occurring post mortem as such closed system u series dating of molluscs is unlikely to provide reliable age constraints for marine deposits even the application of open system u series modelling is challenging because uranium uptake and loss histories can affect time integrated uranium distributions and are difficult to constrain we investigate the chemical and isotopic distribution of uranium in fossil tridacna gigas giant clams from marine isotope stage mis 5e 128 116 ka and mis 11 424 374 ka reefs at huon peninsula in papua new guinea the large size of the clams enables detailed chemical and isotopic mapping of uranium using la icpms and la mc icpms techniques within each fossil tridacna specimen marked differences in uranium concentrations are observed across the three tridacna growth zones outer inner hinge with the outer and hinge zones being relatively enriched in mis 5e and mis 11 tridacna the outer and hinge zones contain approximately 1 ppm and 5 ppm uranium respectively in addition to uptake of uranium loss of uranium appears prevalent especially in the mis 11 specimens the effect of uranium loss is to elevate measured 230th 238u values with little effect on 234u 238u values closed system age estimates are on average 50 too young for the mis 5e tridacna and 25 too young for the mis 11 tridacna a complex multi stage uptake and loss history is interpreted for the fossil tridacna and we demonstrate that they cannot provide independent reliable geochronological controls on the timing of past reef growth at huon peninsula

tropical marine climate during the late paleozoic ice age using trace element analyses of brachiopods abstract the late paleozoic ice age can be considered an important analogue to the modern ice age but comparisons between the two time intervals have been hampered by the difficulty of resolving climatic changes that occur over short e g seasonal time scales in the paleozoic record as a first step toward overcoming these limitations this study employed mg ca trace element ratios sampled across the growth bands of six specimens of the brachiopod composita to assess differences in tropical marine mean temperature and seasonality in visean and moscovian time these time intervals bracket the onset of the late paleozoic ice age which occurred in mid serpukhovian time and thus provide a snapshot of climate changes from a greenhouse to an icehouse world shells were screened for diagenetic alteration by cathode luminescence and by comparing the values of mn sr na and b to those reported for modern brachiopods in addition a 87sr 86sr value measured for one specimen agreed with a published strontium isotope curve for the late paleozoic era both the mean and range of mg ca values were larger in visean than moscovian time suggesting colder and less seasonal temperatures during the late paleozoic ice age the decline in seasonality was due to a greater proportional reduction of maximum values which presumably represent summer temperatures than minimum values these relative differences between the pre ice age and ice age tropical climate provide a first step toward understanding the broad patterns of seasonal scale changes in temperature during a critical time in earth s history