aspects of growth deceleration in bivalves clues to understanding the seasonal δ18o and δ13c record a comment on krantz et al 1987 discussion sur l article de krantz d e williams d f et jones d s paru en 1987 dans palaeogeogr palaeoclimatol palaeoecol vol 58 p 249 266

temporal and spatial variability of the oxygen isotopic composition of massive corals from the south china sea influence of the asian monsoon coral colonies of porites lutea and p lobata were collected from areas to the east and south offshore of hainan island south china sea oxygen isotope ratios o 18 o 16 were analyzed along the major axis of growth at a resolution of 25 28 samples within an annual band from three colonies giving data series lengths of 15 20 and 30 years coral delta o 18 correlates well with sea surface temperature sst throughout most years particularly when the asian winter monsoon prevails over the region due to the same seasonal phases of sst and sea surface salinity sss it is estimated that most of the seasonal features of coral delta o 18 are controlled by changes in sst with a significant contribution of sss this indicates the importance of temperature as determined by the asian winter monsoon as a control on seasonal coral delta o 18 variations in the south china sea given the fact that annual sss maxima show minor inter annual changes the inter annual change of annual coral delta o 18 maximum mainly reflects the sst induced by the winter monsoon while the coral delta o 18 is mainly controlled by sst deviations of the delta o 18 from sst correlate statistically with sea surface salinity particularly for summer extreme events when sst reaches its annual maximum with minor inter annual change therefore we suggest that the inter annual variation of the annual coral delta o 18 minima is mainly controlled by seawater composition seawater composition analysis indicates that its delta o 18 and salinity are simultaneously affected by freshwater inputs primarily from precipitation which is mainly supplied by the asian summer monsoon thus seasonal alternations of the winter and summer monsoon mainly control the coral delta o 18 thereby allowing reconstruction of these monsoonal variables the three coral records consistently reveal clear inter decadal trends in delta o 18 a gradual increase from 1968 to 1987 and a subsequent decrease from 1987 to 2003 these inter decadal trends are roughly consistent with salinity changes but not with temperature and precipitation suggesting that seawater composition controlled by freshwater inputs from distant source areas rather than from local precipitation is responsible for the trends in seawater composition and coral delta o 18 over the last 30 years comparison of the three coral records indicates that spatial variations in coral delta o 18 coincide with variations in seawater salinity and local precipitation but not with temperature this confirms the dominant role of seawater composition mainly controlled by monsoonal precipitation on the spatial variability of coral delta o 18 in the south china sea c 2006 elsevier b v all rights reserved

climate records from a bivalved methuselah arctica islandica mollusca iceland we measured annual shell growth rates of a 374 year old radiometrically confirmed bivalve mollusk specimen of arctica islandica linnaeus this bivalve represents the oldest ever reported individual animal in addition we analyzed 1051 individual powder samples from ontogenetic years two to 40 80 of the entire shell height for isotope analyses oxygen and carbon isotopes exhibit clear intra annual cycles the highest measured carbon isotope values on average 2 73x occurred during summer i e during maximum primary productivity the d 18 oaragonite derived temperature time series cover the period of ad 1496 1533 temperatures calculated from oxygen isotopes ranged from 4 5 to 9 3 8c and exhibit a mean value of 6 2 8c the latter coincides well with the 1854 2003 mean value of 6 81 8c for sea surface temperature between february and september growing season of a islandica neither oxygen nor carbon isotopes exhibit age related unidirectional trends however d 13 caragonite and d 18 oaragonite values fluctuated at decadal periods of four six and eight to nine years nao type periods as well as 12 14 years which may represent teleconnections to cycles in the tropical atlantic annual shell growth is positively correlated to intra annual d 18 oaragonite minima i e warm summer temperatures r 2 0 34 and to intra annual d 13 caragonite minima higher food supply r 2 0 42 using a linear multiregression model 65 of the variation in annual shell growth can be explained by summer temperature and food supply the formation of extremely narrow annual increments coincides with major volcanic eruptions e g tambora 1815 a period of extremely variable growth occurred during the culmination of the little ice age in iceland between ca ad 1550 and 1620 shell growth during ad 1765 1780 however was characterized by very little year to year variability probably as the result of extremely mild climate near the end of the little ice age this study demonstrates that shells of a islandica provide

a review of palaeoclimates and palaeoenvironments in the levant and eastern mediterranean from 25 000 to 5000 years bp setting the environmental background for the evolution of human civilisation abstract the southern levant has a long history of human habitation and it has been previously suggested that climatic changes during the late pleistocene holocene stimulated changes in human behaviour and society in order to evaluate such linkages it is necessary to have a detailed understanding of the climate record we have conducted an extensive and up to date review of terrestrial and marine climatic conditions in the levant and eastern mediterranean during the last 25 000 years we firstly present data from general circulation models gcms simulating the climate for the last glacial maximum lgm and evaluate the output of the model by reference to geological climate proxy data we consider the types of climate data available from different environments and proxies and then present the spatial climatic picture for key climatic events this exercise suggests that the major northern hemisphere climatic fluctuations of the last 25 000 years are recorded in the eastern mediterranean and levantine region however this review also highlights problems and inadequacies with the existing data

food for thought mathematical approaches for the conversion of high resolution sclerochronological oxygen isotope records into sub annually resolved time series abstract oxygen isotope 18 o records of incrementally banded marine calcifiers provide high resolution information about modern and past environmental conditions however given their biological origin these records are often distorted by ontogenetic and seasonal growth pattern to evaluate their reliability many studies correlate skeletal 18 o records with instrumentally measured time series of environmental conditions using a variety of methods to recalculate their temporal framework lacking consistency and a limited traceability of many temporal alignment methods underline the need for standardized and flexible method for the temporal alignment of sclerochronological records here two methods for the temporal alignment of sclerochronological data and their application on measured oxygen isotope signatures of a fish otolith and a marine bivalve shell are presented and compared the first method is a flexible approach using a linear interpolation between carefully selected temporal reference points for recalculating ontogenetic growth effects with an optional extension accounting for seasonal growth oscillations the second approach uses the seasonally oscillating von bertalanffy growth function parameterized based on the oxygen isotope record to reconstruct the underlying growth model and reconstruct thereby its temporal framework using these methods we re align 18 o based water temperature records of a carlarius heudelotii otolith and a venus crebrisulca shell with measured sea surface temperature time series and compare the resulting correlation as well as the different underlying growth models our results show that both methods represent useful tools for the temporal alignment of sclerochronological records however underlying growth models strongly differ depending on the temporal alignment method and the parameters used for the reconstruction of the temporal framework this underlines the importance of a careful selection of a particular alignment method depending on the complexity of distortion due to seasonal and ontogenetic growth trajectories moreover we show that both organisms represent reliable paleoenvironmental archives providing sub seasonally resolved water temperature records

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

reconstructing seawater δ18o from paired coral δ18o and sr ca ratios methods error analysis and problems with examples from tahiti french polynesia and timor indonesia we compare several statistical routines that may be used to calculate delta o 18 and sss from paired coral sr ca and delta o 18 measurements typically the delta o 18 coral sst relationship is estimated by linear regression of coral delta o 18 vs sst if this method is applied evidence should be given that at a particular site sst and sss do not co vary in the tropical oceans sst and delta o 18 sw sss often co vary and this will bias the estimate of the regression slope of delta o 18 coral sst using a stochastic model we show that covariance leads to a bias in the coefficients of the univariate regression equations as the slope of the delta o 18 coral sst relationship has known we propose to insert this value for gamma 1 in the regression models this requires that the constants of the regression equations are removed to omit the constants we propose to center the regression equations i e to remove the mean values from the variables the statistical error propagation is calculated to assess our ability to resolve past variations in delta o 18 sw sss at tahiti we find that the combined analytical uncertainties of coral delta o 18 and sr ca equal the amplitude of the seasonal cycle of delta o 18 sw sss therefore we cannot resolve the seasonal cycle of sss at tahiti at timor the error of reconstructed delta o 18 sw sss is lower than the magnitude of seasonal variations of delta o 18 sw sss and the seasonal cycle of delta o 18 sw sss can be resolved c 2008 elsevier ltd all rights reserved

late turonian climate variability in the bohemian cretaceous basin a sclerochronological study of inoceramus hercules shells from the upohlavy quarry czech republic abstract the 18o record of well preserved shells of the inoceramid inoceramus hercules from the upohlavy working quarry czech republic provides an insight into the climate variability in the late turonian benthic environment of the bohemian cretaceous basin similar to modern bivalves this inoceramid species built its shell near equilibrium with the oxygen isotope value of the ambient water due to the nearly year round shell growth sequentially sampled 18o values allowed to estimate the narrowest sub annual temperatures fluctuations that prevailed during lifetime of the organisms in accordance with previous studies reconstructed temperatures suggest colder water conditions 19 0 0 9 c during the earliest late turonian coinciding with the hyphantoceras event also known as hitch wood event than during the later part of the substage 20 9 1 1 c climate warming however did not affect the sub annual temperature fluctuations evenly but predominantly affected the warmest part of the year at least 4 0 c on the contrary the coldest recorded temperatures remained more or less invariant varying not much more than 1 0 c across the studied time interval the observed changes in the benthic temperature estimates likely reflect shifts in seasonal sea surface temperature amplitudes in response to climate forcing given the widespread distribution of i hercules in the upper turonian lower coniacian hemipelagic strata of europe the present study sets the basis for future continent wide sub annually resolved climate reconstructions

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

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

stable isotopic evidence from paleosol carbonates and fossil teeth in greece for forest or woodlands over the past 11 ma abstract mio pliocene fluvial rocks containing buried paleosols are common in greece and turkey we used the carbon and oxygen isotopic composition of pedogenic carbonates associated with these paleosols to estimate the proportion of c3 trees shrubs and cool growing season grasses and c4 warm growing season grasses plants once present on the landscape evidence from the paleosols in well known fossil bearing formations in the lower axios valley in macedonia and from samos pikermi near athens and rhodes all show that mio pliocene vegetation was dominated by c3 plants as the entire region is today in addition nearly all paleosols contained carbonate indicating that mean annual pitation has remained under about 1 m yr during the last 11 ma the carbon isotopic evidence thus precludes the presence of serengeti type c4 grasslands favored by summer precipitation but permits c3 forest or grasses fed by winter rains or forest with mixed seasonal precipitation however there is no evidence in the published palynological records from the region for abundant grasses given these lines of evidence we suggest that dry forest and woodland largely c3 dominated the vegetation of the region c3 grasslands if present were probably of very restricted extent this reconstruction is supported by carbon isotopic evidence from fossil teeth from samos and from pasalar in nw turkey and by published evidence on masticatory morphology of turolian age ruminants from samos and pikermi our findings imply that the classic fossil bearing localities on samos and at pikermi and from the lower axios valley in macedonia were not open savannas as has been previously suggested but rather woodlands or forests

reanalysis of ancient eclipse astronomic and geodetic data a possible route to resolving the enigma of global sea level rise predictions of the earth s response to the ice age appear to simultaneously reconcile a set of astronomical geodetic and ancient eclipse observations related to changes in rotation thus ruling out ice melting as a major contributor to 20th century sea level rise we demonstrate that the reconciliation disappears when an improved theory of rotational stability is applied furthermore our reanalysis of longer satellite records renders previous estimates of the secular change in rotation rate suspect the updated ice age predictions and observations permit an anomalous 20th century ice flux of 1 mm yr equivalent sea level rise thus the full suite of earth rotation observations are consistent with a connection between climatic warming and recent melting of ice reservoirs

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

spondylus gaederopus a new mediterranean climate archive based on high resolution oxygen and carbon isotope analyses abstract the presented study evaluates the potential of the mediterranean bivalve spondylus gaederopus linne 1758 as a palaeoclimatic archive its fixosessil life in water depths 18 o and carbon 13 c isotope data obtained from high resolution sampling of a modern s gaederopus from rhodes greece collected alive in 4 m water depth in spring 2002 suggest that the outer calcitic shell layer as well as the inner aragonitic shell layer is precipitated in equilibrium with seawater due to the complexity of the outer calcitic shell layer with its spines and prickles a chronological sampling of this part of the shell is not possible in contrast the inner aragonitic shell layer with its well developed growth bands allows a fast chronologic sampling 18 aragonite growth bands were sampled from the inner shell layer of the studied specimen corresponding to 9 years of growth with 9 10 samples per year carbon stable isotopes 13 c ar yield mean values of 0 70 0 6 and show a remarkable negative shift of about 1 8 from about 1 6 to about 0 2 through time this ontogenetic depletion in 13 c might be related to physiological developments like sexual maturity as it is the case in other bivalves seasonal variations with an average amplitude of 0 85 are superimposed on the observed secular trend these cycles show an increase in amplitude that has not been described before and cannot be explained so far oxygen isotopes 18 o ar exhibit mean values of 1 11 0 5 clearly pronounced seasonal cycles with an average amplitude of 1 45 show the same wavelength as the carbon cycles but run out of phase the 18 o ar correlates well with sea surface temperature and correlation fits best during summer periods deviations between measured and predicted 18 o ar input data sea surface temperature seawater 18 o show that maximal discrepancies occur during winter periods these discrepancies can be best explained by a decrease in local seawater 18 o due to increased freshwater influx on rhodes maxima in precipitation hence river runoff occur during winter months

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

sedimentary evolution of a late pleistocene temperate red algal reef coralligene on rhodes greece correlation with global sea level fluctuations autochthonous red algal structures known as coralligene de plateau occur in the modern warm temperate mediterranean sea at water depths from 20 to 120 m but fossil counterparts are not so well known this study describes from an uplifted coastal section at plimiri on the island of rhodes a 450 m long by 10 m thick late pleistocene red algal reef coralligene facies interpreted as being a coralligene de plateau and its associated deposits the coralligene facies constructed mainly by lithophyllum and titanoderma sits unconformably upon the plio pleistocene rhodes formation and is overlain by a maerl facies 2 m a mixed siliciclastic carbonate facies 0 2 m and an aeolian sand facies 2 5 m the three calcareous facies of heterozoan character are correlated with established members in the lindos acropolis formation in the north of the island while the aeolian facies is assigned to the new plimiri aeolianite formation the palaeoenvironmental and genetic stratigraphic interpretations of these mixed siliciclastic carbonate temperate water deposits involved consideration of certain characteristics associated with siliciclastic shelf and tropical carbonate shelf models such as vertical grain size trends and the stratigraphic position of zooxanthellate coral growths integration of these results with electron spin resonance dates of bivalve shells indicates that the coralligene facies was deposited during marine isotope stage 6 to 5e transgressive event ca 135 to 120 ka in water depths of 20 to 50 m and the overlying maerl facies was deposited during regression from marine isotope stage 5e to 5d ca 120 to 110 ka at water depths of 25 to 40 m the capping aeolian sand facies involving dual terrestrial subunits is interpreted as having formed during each of the glacial intervals marine isotope stages 4 71 to 59 ka and 2 24 to 12 ka with soil formation during the subsequent interglacial periods of marine isotope stages 3 and 1 respectively accumulation rates of about 0 7 mm year 1 are estimated for the coralligene facies and minimum accumulation rates of 0 2 mm year 1 are estimated for the maerl facies the existence of older red algal reefs in the plimiri region during at least marine isotope stages 7 245 to 186 ka and 9 339 to 303 ka is inferred from the occurrence of reworked coralligene type lithoclasts in the basal part of the section and from the electron spin resonance ages of transported bivalve shells

lithofacies modelling and sequence stratigraphy in microtidal cool water carbonates a case study from the pleistocene of sicily italy quaternary carbonates in se sicily were deposited in seamount and short ramp settings during glacio eustatically driven highstand conditions they provide an excellent opportunity to investigate the depositional and erosional aspects of cool water carbonate sedimentation in a microtidal marine water body the derived ramp facies model differs significantly from modern day open ocean ramp scenarios in projected facies depth ranges and in the preservation of inshore facies a sequence stratigraphic study of the carbonates has confirmed many established aspects of carbonate sedimentation e g production usually only occurred during highstands it has also revealed several new features peculiar to water bodies with little tidal influence including catch up surfaces taking the place of transgressive facies second order sequence boundary events being most important as triggers for initiating resedimentation and a virtual absence of sediment shedding to the basin during the terminal lowstand production in the carbonate factory lasted for about 0 5 myr despite this carbonate production was considerable and included both bioconstructional and bioclastic dominated facies and the production of abundant lime muds a model for eustatically controlled cool water carbonate production and resedimentation in microtidal marine water bodies is presented this is considered to be more applicable to neogene and quaternary strata in the mediterranean region than are current open ocean models

a holocene coral algal reef at mavra litharia gulf of corinth greece structure history and applications in relative sea level change a holocene coral algal reef at mavra litharia south central coast of gulf of corinth greece is exposed from ca 2 to 9 3 m above sea level on an uplifting footwall associated with the eliki fault the reef lacks sea level critical species but its coralline algal assemblage indicates a ca 10 m water depth reef frame components date from 9280 8730 years bp to 6343 5993 years bp so the reef frame grew between ca 10 000 and 6000 years bp the youngest dated shells 1860 305 years bp from the site are accessory organisms collected from the lowest 2 m of outcrop one of which dendropoma grew at sea level stiros s c and pirazzoli p 1998 late quaternary coastal changes in the gulf of corinth greece tectonics earthquake archaeology guidebook for the gulf of corinth field trip patras university greece patras september 14 16 1998 reef history has four phases a growth and lithification of reef b development of smooth walled dissolution pipes and caves in the reef c colonisation of dissolution surfaces by mn fe crusts that may be bacterially formed barnacles serpulid worms and rock boring bivalves and d uplift to present position where much of the reef is eroded sea level history after 11 500 years bp when rising post glacial sea level overtopped the rio sill and returned the gulf of corinth to a marine environment is reconstructed calculations of interplay between sea level rise and tectonic uplift suggest that between 11 500 and 10 000 years bp sea level rose very quickly associated with deglaciation at the close of the younger dryas mwp 1b at a maximum of 25 6 mm year broadly consistent with other studies then slowed to ca 4 4 mm year until 6000 years bp when sea level was ca 3 m below modern after which sea level rose at ca 0 5 mm year to modern day tectonic uplift rate of maximum 3 mm year slower than sea level rise means that the reef could not catch up to sea level until recent times explaining its fossil assemblage the pipe cave system is interpreted as having formed when the reef top was emerged but much dissolution occurred beneath sea level because of insufficient time to allow uplift and resubmergence intense rainfall during the mid holocene pluvial phase ca 6000 years bp for the eastern mediterranean which affected large areas of the mediterranean is suggested as the mechanism and timing of submarine dissolution

effect of skeletal growth and lack of species effects in the skeletal oxygen isotope climate signal within the coral genus porites abstract we investigated variations in skeletal 18 o within the scleractinian coral species porites lutea p australiensis and p murrayensis looking at the intra colony inter colony and between species level this provides unambiguous information to test the existence of species specific effects and other non environmental sources of variation affecting the oxygen isotope climate signal comparing replicate isochronic 18 o time series revealed that there was no species specific effect on skeletal 18 o non environmental variation could be attributed to methodological constraints in sampling and to variations in annual linear skeletal extension lse annual lse was on average 10 mm 2 9 s d and ranged from 4 5 to 18 mm correlation analyses between mean annual 18 o and annual lse showed weak but significant and negative correlations for all years when the slope of 18 o vs lse of the respective years was used to correct monthly 18 o for variations due to lse the average standard deviation s d between the 12 replicate monthly 18 o values was reduced by 18 only after removing the effect of lse on coral 18 o it was possible to identify in the coral 18 o time series the severe drought in indonesia that preceded the 1982 1983 el nino event

intra annual isotopic variation in venericardia bivalves implications for early eocene temperature seasonality and salinity on the u s gulf coast abstract stable isotope compositions were determined for 166 microsamples of aragonite from the bivalve venericardia hatcheplata collected from the early eocene hatchetigbee formation in southwestern alabama these were milled from two transects one across the left valve hinge plate and one along the growth axis amplitude and spacing of about nine years of seasonal variation is very regular with peaks and troughs occurring at equal intervals and reaching consistent compositions except for some attenuation in both parameters during the last three years of life assuming an ice free world with an ocean 18o value of about 1 0 and using the aragonite water fractionation equation of grossman and ku 1986 isotope derived paleotemperatures are somewhat warmer 31 c than temperatures presently recorded anywhere on the earth s surface and exhibit significantly greater seasonality 12 c than regions with the warmest mean temperatures it is therefore likely that these very negative and extremely seasonal 18o values reflect the influence of seasonal discharge of 18o depleted river water into the eocene gulf of mexico comparison of these data with 1 mean annual temperature versus seasonal temperature variation from modern climates 2 isotopic compositions reported from coeval molluscs and 3 isotopic compositions of global meteoric precipitation and united states rivers suggest that mean annual temperature along this portion of the eocene gulf coast was in fact about 26 c and varied seasonally from a winter low of about 25 c to a summer high of 27 c differences between these temperatures and those derived from direct conversion of oxygen isotope values reflect the influence of seasonal influx of fresh 18o value of 4 7 water during deposition of this portion of the hatchetigbee formation ambient water 18o values varied between winter values of about 1 0 to less than 3 5 during the summer freshwater discharge served to seasonally depress salinity to 10 to 16 ppt along this part of the gulf coast the early eocene was perhaps the warmest time interval of the past 65 million years primarily manifest as lower equator to pole temperature gradients in this context an eocene mean annual temperature of 26 c is not much higher than modern surface water temperatures of about 24 c at 29 30 n immediately off the modern alabama coast seasonal temperature variation of 2 to 3 c about a mean of 26 c however is significantly lower than that off coastal alabama 19 to 30 c and occurs only along modern equatorial coasts at latitudes less than 19 this implies that early eocene tropical conditions extended well beyond modern latitudinal limits

the roles of fire in holocene ecosystem changes of west africa abstract the climate changes associated with the holocene wet phase in the sahara the african humid period are subject to ongoing debate discussing interactions between climate and vegetation and possible feedbacks between vegetation albedo desertification and dust however very little attention has been given to the role of fire in shaping the land cover although it is known that fires are important in the formation and consolidation of the african savanna to fill this gap we investigated the interaction between precipitation changes vegetation shifts and fire occurrence in west africa by combining stable isotope measurements on plant waxes with pollen and micro charcoal counts of marine sediments retrieved offshore of cape blanc our study focuses on the roles of fire at the dry limit of savanna during the holocene evolution of precipitation changes indicating that the impact of fire during a relative wet climate differs from that during aridification during the humid early holocene increased savanna extension and diversification ran parallel to increased fire occurrence in contrast after aridification of northern africa started at the end of the african humid period a maximum in fire occurrence correlated with a deterioration of the vegetation promoting desertification

dating and characterization of polymorphic transformation of aragonite to calcite in pleistocene bivalves from rhodes greece by combined shell microstructure stable isotope and electron spin resonance study absolute dating of diagenesis is a challenging yet significant problem reconstructing the depositional and diagenetic history of a late pleistocene coralligene type red algal reef and overlying maerl red algal sand from the plimiri coastal cliff se island of rhodes greece is enabled using a combination of microstructure stable isotope analyses and electron spin resonance of large bivalve shells partially altered by diagenesis these shells consisting of both original shell aragonite and polymorphic transformed rims now consisting of neomorphic spar provide the opportunity to date the primary age when the shells were precipitated as well as the age of their polymorphic transformation the contamination of samples presented a significant problem for interpreting ages based on data from electron spin resonance esr alone however sample contamination was evaluated with quantitative xrd providing the opportunity to apply corrections which increased reliability of the ages the carbon and oxygen stable isotope values and the neomorphic spar microtexture suggested that the polymorphic transformation at plimiri took place in a meteoric environment with a high and increasing fluid rock ratio the electron spin resonance dates combined with the vertical sedimentary evolution allowed to assign the formation of the red algal reef to the marine isotope stages 6 to 5e transgressive event ca 135 to 120 ka and to identify meteoric diagenetic phases during possibly the marine isotope stage 5d and the upper marine isotope stage 5c to lower 3 the use of electron spin resonance dating of neomorphic spar and age correction for sample contamination is presented herein for the first time and the results suggest that it might provide a useful tool to date late pleistocene diagenesis

pleistocene coralline algal build ups coralligene de plateau and associated bioclastic deposits in the sedimentary cover of cutro marine terrace calabria southern italy

elemental and isotopic proxies of paleotemperature and paleosalinity climate reconstruction of the marginal northeast pacific ca 80 ka isotope 18 o and minor element mg ca sr ca analyses of a fossil shell of the marine mussel mytilus trossulus gould from the whisky run terrace at coquille point bandon oregon enable reconstruction of a paleoclimatic profile for the temperate northeastern pacific ca 80 85 ka the whisky run terrace is correlative with marine oxygen isotope 18 o substage 5a the final sea level highstand of the last interglacial complex herein we provide sea surface temperature estimates and report on a new technique that allows estimates to be made of 18 o of seawater and riverine discharge from the skeletal chemistry of a single mussel shell estimates of mean annual temperature from mg ca ratios are lower than those suggested by the accompanying fossil fauna and significantly lower than present day conditions the data also suggest a decrease in the range of seasonal temperature extremes at 80 ka compared to today estimates of the fresh water and seawater 18 o end members 4 5 and 0 5 respectively are slightly greater than modern values

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

shell of the great scallop pecten maximus as a high frequency archive of paleoenvironmental changes 1 we investigate the environmental and biological controls on oxygen isotope ratios in the shells of modern pecten maximus bivalves collected alive in the bay of brest france seasonal 18o profiles obtained by drilling the daily calcite ridges deposited at the surface of the left valve were compared with in situ measurements of temperature and salinity we show that p maximus 18o values accurately track seasonal variations in bottom water temperature shell growth rate has no significant effect on shell 18o values our study demonstrates that daily variations in water temperature can be reconstructed within about 0 5 c temperatures estimated with the paleotemperature equation established in this study were compared with temperatures derived from previously published equations the comparison indicates that the most commonly used paleotemperature equation for biogenic calcite epstein et al 1953 provides inaccurate temperature estimates but the kim and o neil 1997 equation established from abiogenic calcite precipitation provides results very similar to ours and should therefore be used for scallop individuals coming from populations where proper empirical calibration cannot be done pecten maximus bivalves precipitate calcite in isotopic equilibrium with seawater produce large daily growth striae are stenohaline and are well preserved in archeological and geological deposits making them an excellent high frequency archive of paleoenvironmental change