stable and clumped isotopes in shell carbonates of land snails cathaica sp and bradybaena sp in north china and implications for ecophysiological characteristics and paleoclimate studies knowledge of ecophysiological characteristics of different land snail species is crucial for defining climatic significance of snail faunal assemblages however little work has been done in this aspect hindering our obtaining unambiguous paleoclimatic information using these proxy indicators here we document for the first time the different ecophysiological characteristics of cathaica sp and bradybaena sp land snails using the stable isotopes and clumped isotope 47 of the shell carbonates the 47 derived temperatures for both species revealed a robust correlation with environmental temperatures moreover the temperatures for cathaica sp are 3 5 c higher than those for bradybaena sp land snails indicating different ecophysiological adaptations or growing seasons of the two species specifically cathaica sp snails prefer living in a warm humid summer whereas bradybaena sp snails are active in the relatively cool arid spring and or autumn the result testifies to the 47 in snail shell carbonates as a promising paleothermometer in monsoonal region and presents new insight into paleoclimatic explanation of these land snail species this finding highlights the importance of climatic seasonality in the changes of the faunal assemblages of land snails

the influence of diet on the δ13c of shell carbon in the pulmonate snail helix aspersa abstract the influence of diet and atmospheric co2 on the carbon isotope composition of shell aragonite and shell bound organic carbon in the pulmonate snail helix aspersa raised in the laboratory was investigated three separate groups of snails were raised on romaine lettuce c3 plant 13c 25 8 corn c4 plant 13c 10 5 and sour orange 12c enriched c3 plant 13c 39 1 the isotopic composition of body tissues closely tracked the isotopic composition of the snail diet as demonstrated previously however the isotopic composition of the acid insoluble organic matrix extracted from the aragonite shells does not track diet in all groups in snails that were fed corn the isotopic composition of the organic matrix was more negative than the body by as much as 5 whereas the matrix was approximately 1 heavier than the body tissues in snails fed a diet of c3 plant material these results indicate that isotopic composition of the organic matrix carbon cannot be used as an isotopic substrate for paleodietary reconstructions without first determining the source of the carbon and any associated fractionations the isotopic composition of the shell aragonite is offset from the body tissues by 12 3 in each of the culture groups this offset was not influenced by the consumption of carbonate and is not attributable to the diffusion of atmospheric co2 into the hemolymph the carbon isotopic composition of shell aragonite is best explained in terms of equilibrium fractionations associated with exchange between metabolic co2 and hco3 in the hemolymph and the fractionation associated with carbonate precipitation these results differ from previous studies based primarily on samples collected in the field that have suggested atmospheric carbon dioxide contributes significantly to the shell 13c the culture results indicate that the 13c of aragonite is a good recorder of the isotopic composition of the snail body tissue and therefore a better recorder of diet than is the insoluble shell organic carbon because the systematic fractionation of carbon isotopes within the snail is temperature dependent the 13c of the shell could provide an independent technique for estimating paleotemperature changes

carbonate clumped isotope variability in shallow water corals temperature dependence and growth related vital effects geochemical variations in shallow water corals provide a valuable archive of paleoclimatic information however biological effects can complicate the interpretation of these proxies forcing their application to rely on empirical calibrations carbonate clumped isotope thermometry 47 is a novel paleotemperature proxy based on the temperature dependent clumping of 13 c 18 o bonds similar 47 temperature relationships in inorganically precipitated calcite and a suite of biogenic carbonates provide evidence that carbonate clumped isotope variability may record absolute temperature without a biological influence however large departures from expected values in the winter growth of a hermatypic coral provided early evidence for possible 47 vital effects here we present the first systematic survey of 47 in shallow water corals sub annual red sea 47 in two porites corals shows a temperature dependence similar to inorganic precipitation experiments but with a systematic offset toward higher 47 values that consistently underestimate temperature by 8 c additional analyses of porites siderastrea astrangia and caryophyllia corals argue against a number of potential mechanisms as the leading cause for this apparent 47 vital effect including salinity organic matter contamination alteration during sampling the presence or absence of symbionts and interlaboratory differences in analytical protocols however intra and inter coral comparisons suggest that the deviation from expected 47 increases with calcification rate theoretical calculations suggest this apparent link with calcification rate is inconsistent with ph dependent changes in dissolved inorganic carbon speciation and with kinetic effects associated with co 2 diffusion into the calcifying space however the link with calcification rate may be related to fractionation during the hydration hydroxylation of co 2 within the calcifying space although the vital effects we describe will complicate the interpretation of 47 as a paleothermometer in shallow water corals it may still be a valuable paleoclimate proxy particularly when applied as part of a multi proxy approach

cryogenic brines as diagenetic fluids reconstructing the diagenetic history of the victoria land basin using clumped isotopes abstract the isotopic analyses 13c 18o and 47 of carbonate phases recovered from a core in mcmurdo sound by antarctic geologic drilling andrill 2a indicate that the majority of secondary carbonate mineral formation occurred at cooler temperatures than the modern burial temperature and in the presence of fluids with 18owater values ranging between 11 and 6 vsmow these fluids are interpreted as being derived from a cryogenic brine formed during the freezing of seawater the 47 values were converted to temperature using an in house calibration presented in this paper measurements of the 47 values in the cements indicate increasingly warmer crystallization temperatures with depth and while roughly parallel to the observed geothermal gradient consistently translate to temperatures that are cooler than the current burial temperature the difference in temperature suggests that cements formed when they were 260 100 m shallower than at the present day this depth range corresponds to a period of minimal sediment accumulation from 3 to 11 myr it is therefore interpreted that the majority of cements formed during this time this behavior is also predicted by time integrated modeling of cementation at this site if this cementation had occurred in the presence of these fluids then the cryogenic brines have been a longstanding feature in the victoria land basin brines such as those found at this site have been described in numerous modern high latitude settings and analogous fluids could have played a role in the diagenetic history of other ice proximal sediments and basins during glacial intervals throughout geologic history the agreement between the calculated 18owater value and the measured values in the pore fluids shows how the 47 proxy can be used to identify the origin of negative 18o values in carbonate rocks and that extremely negative values do not necessarily need to be a result of the influence of meteoric fluids or reaction at high temperature

strontium isotopes as tracers of ecosystem processes theory and methods abstract the strontium sr isotope method can be a powerful tool in studies of chemical weathering and soil genesis cation provenance and mobility and the chronostratigraphic correlation of marine sediments it is a sensitive geochemical tracer applicable to large scale ecosystem studies as well as to centimeter scaled examination of cation mobility within a soil profile the 87sr 86sr ratios of natural materials reflect the sources of strontium available during their formation isotopically distinct inputs from precipitation dryfall soil parent material and surface or groundwater allow determination of the relative proportions of those materials entering or leaving an ecosystem the isotopic compositions of labile soil exchange complex and soil solution strontium and sr in vegetation reflect the sources of cations available to plants strontium isotopes can be used to track the biogeochemical cycling of nutrient cations such as calcium the extent of cation contributions from in situ weathering and external additions to soil from dust and rain can also be resolved with this method in this paper we review the geochemistry and isotopic systematics of strontium and discuss the use of this method as a tracer of earth surface processes

siderite clumped isotope thermometry a new paleoclimate proxy for humid continental environments abstract clumped isotope measurements can be used to exploit the paleoclimatic potential of pedogenic siderite feco3 however the applicability of this method is held back by the lack of clumped isotope calibrations of mineralogies other than calcite and aragonite here we present an inorganic calibration of siderites grown in the laboratory between 21 and 51 c linear regression of 47 values and temperature 106 t2 k yields the following relationship r2 0 997 47 rf 0 0356 0 0018 10 6 t 2 0 172 0 019 we demonstrate that this calibration is indistinguishable from calcite at current levels of analytical precision our observations suggest that there is likely no large systematic bias in the clumped isotope acid fractionation factors between the two different carbonate minerals we also present clumped isotope measurements of a natural siderite collected from holocene sediments of the mississippi river delta we find that siderites record warm season marsh water temperatures instead of mean annual temperatures as it has long been presumed this finding has important implications for the accuracy of siderite stable isotope and clumped isotope based climate reconstructions

a three dimensional baroclinic model of the irish sea formation of the thermal fronts and associated circulation a high resolution three dimensional baroclinic shelf sea model is developed and applied to the determination of the various processes influencing the generation and position of thermal fronts and the associated circulation in the irish sea the model has a horizontal grid resolution of approximately 3 6 km by 3 0 km and can resolve the thermal fronts in the region in particular in the western irish sea although the grid is not sufficiently fine to resolve small scale features along these fronts produced by baroclinic instabilities using meteorological forcing from dublin airport located close to the center of the region and tidal forcing a series of numerical experiments were performed to examine the processes influencing the location and dynamics of thermal fronts and associated circulation in the irish sea the results show a reasonable qualitative agreement with observations of the thermal stratification and the associated circulation in the western irish sea the ability of the model to reproduce the main features of the frontal structures in the region having been established it is used to examine the interannual variability of the density flow field calculations using meteorological forcing from different years show that the western irish sea fronts and the associated cyclonic circulation are persistent features although exact details of the fronts and their times of formation and breakdown show a large interannual variability model results also reveal a patch of thermal stratification in the northern part of the eastern irish sea with northward thermal density driven currents in this region

residual currents in a semi enclosed bay of the seto inland sea japan 1 on the basis of the princeton ocean model a robust diagnostic model is developed to calculate the residual currents in the hiuchi nada a semi enclosed bay of the seto inland sea the input water temperature and salinity data are from six hydrographic surveys in 2002 and the model results in the summer show a clockwise eddy in the western part of the bay and an anticlockwise eddy in the eastern part the magnitude of two eddies is 10 cm s the modeled flow pattern is consistent with early observations derived from moored arrays the two eddies are persistent throughout the summer because winds are usually weak and cannot influence their existence the tide induced residual currents are appreciable only in the close vicinity of the kurushima strait and bisan strait the two straits connecting the bay to the other bays and have little affect on the two eddies that are inside the bay thus the two density driven eddies in the hiuchi nada are the basic pattern of circulation in the summer using the calculated residual currents we examined the intrusion route of waters from the kurushima strait and bisan strait with passive tracer experiments the results show that the water in the kurushima strait intrudes into the bay mainly through the middle and bottom layers while the water in the bisan strait intrudes mainly through the surface layer furthermore the tracer cannot reach the center of the anticlockwise eddy in the eastern part of the bay this indicates that the eddy prevents water exchange between its center and outer edges and provides favorable conditions for the formation of oxygen deficient waters in the central part of the eddy

the role of advection in determining the temperature structure of the irish sea abstract the temperature structure of the irish sea is investigated using a 3 yr simulation with a high resolution 1 8 km three dimensional baroclinic model the proudman oceanographic laboratory coastal ocean modelling system and ctd and advanced very high resolution radiometer observations this paper focuses on the extent to which horizontal advection determines the temperature structure it is found that it has a significant effect on the depth mean temperatures throughout the region and on the vertical profiles in seasonally stratified areas such as the celtic sea and western irish sea there is depth mean advective heating during the summer in these stratified regions whereas in well mixed regions advection tends to reduce the amplitude of the seasonal cycle through an analysis of the terms in the temperature equation the warming of the cool pool waters of the western irish sea can be attributed to the advection of partially well mixed waters into the stratified region from the north th

laboratory calibration of the calcium carbonate clumped isotope thermometer in the 25 250 c temperature range abstract many fields of earth sciences benefit from the knowledge of mineral formation temperatures for example carbonates are extensively used for reconstruction of the earth s past climatic variations by determining ocean lake and soil paleotemperatures furthermore diagenetic minerals and their formation or alteration temperature may provide information about the burial history of important geological units and can have practical applications for instance for reconstructing the geochemical and thermal histories of hydrocarbon reservoirs carbonate clumped isotope thermometry is a relatively new technique that can provide the formation temperature of carbonate minerals without requiring a priori knowledge of the isotopic composition of the initial solution it is based on the temperature dependent abundance of the rare 13c 18o bonds in carbonate minerals specified as a 47 value the clumped isotope thermometer has been calibrated experimentally from 1 c to 70 c however higher temperatures that are relevant to geological processes have so far not been directly calibrated in the laboratory in order to close this calibration gap and to provide a robust basis for the application of clumped isotopes to high temperature geological processes we precipitated caco3 mainly calcite in the laboratory between 23 and 250 c we used two different precipitation techniques first minerals were precipitated from a caco3 supersaturated solution at atmospheric pressure 23 91 c and second from a solution resulting from the mixing of cacl2 and nahco3 in a pressurized reaction vessel at a pressure of up to 80 bar 25 250 c the calibration lines of both experimental approaches overlap and agree in the slopes with theoretical estimates and with other calibration experiments in which carbonates were reacted with phosphoric acid at temperatures above 70 c our study suggests a universal 47 t calibration t in k 47 in 47 0 98 0 01 3 407 10 9 t 4 2 365 10 7 t 3 2 607 10 3 t 2 5 880 t 0 293 0 004 this new 47 t calibration given in the absolute reference frame that extends the experimentally calibrated temperature range for clumped isotopes to 250 c can be applied to carbonates that grew at intermediate temperatures 20 250 c

stable isotope δ18o δ13c and δd signatures of recent terrestrial communities from a low latitude oceanic setting endemic land snails plants rain and carbonate sediments from the eastern canary islands abstract stable isotopes of oxygen and carbon extracted from fossil land snail shells have been used increasingly to interpret past environments to evaluate the utility of this approach for low latitude oceanic islands populations of the modern helicid land snail theba geminata a species also abundant in the quaternary fossil record of the region were sampled at ten low altitude d and 2 v smow for 18 o ranging from 11 to 2 v smow and from 2 6 to 0 7 v smow respectively the local vegetation is heterogeneous including c 3 c 4 and cam plants 13 c values vary from 13 0 to 29 0 v pdb across plant species of the 24 species five are c 4 15 are c 3 and four are cam plants the 18 o values for shells represent a narrow range of values from 0 3 to 2 5 v pdb which is consistent with the low climate seasonality typifying low latitude oceanic settings hypothetical model of the expected 18 o value for shell aragonite precipitated in equilibrium suggests that the most negative 18 o shell represent the closest estimate for 18 o rain water the 13 c values of shells range from 9 4 to 1 7 v pdb the most positive 13 c values are attributed to a diet based on c 4 plants the comparison of 13 c values of soft tissues and shells suggests that snails ingested notable amounts from 20 up to 40 of foreign carbonates consequently fossil shells with the most negative 13 c values should be selected for radiocarbon dating in future geochronological studies of the region the 13 c values of body tissues vary from 12 0 to 27 2 v pdb indicating that land snails consumed c 3 and c 4 plants indiscriminately the mean carbon isotopic composition averaged across multiple fossil specimens may thus provide a useful tool for reconstructing paleoclimates and paleoenvironments throughout the quaternary history of the canary islands and other comparable low latitude oceanic settings

the use of land snail shells in paleoenvironmental reconstruction fossil land snail shells constitute a valuable source of paleoenvironmental information for the quaternary they can be dated by a variety of methods including radiocarbon amino acid racemization and epimerization and perhaps also thu and esr the vast majority of paleoenvironmental studies based on land snail shells have examined the faunal composition of fossil assemblages from which a variety of paleoenvironmental characteristics such as biome temperature and moisture conditions have been reconstructed still there are a number of problems involved in using this approach and these are discussed shell morphology has occasionally been used to reconstruct such factors as rainfall and temperature stable isotope studies on quaternary land snails include analysis of 18o values of organic matter in the shells to reconstruct c4 plant distributions from which rainfall amounts can be inferred and analysis of 18o values of shell carbonate from which trends in the oxygen isotope composition of rainfall can be reconstructed stable carbon isotopes of shell carbonate have also been studied but their interpretation is not clear amino acid epimerization analysis dalloisoleucinel isoleucine ratios of land snail shells has been used for estimation of paleotemperatures some potential uses of land snail shells for paleoenvironmental reconstruction include the study of stable isotopes of h and n periodic growth lines and deposits of pedogenic carbonates on the shells

the effect of h2o2 treatment on stable isotope analysis δ13c δ18o and δ47 of various carbonate minerals abstract in carbonate isotopic measurements h2o2 treatment is one of the most often used methods to remove organic matter contaminants from carbonate minerals for accurate analysis but the interaction between h2o2 solution and carbonate minerals may also lead to analytical bias in this study we quantitatively tested the effect of h2o2 treatment for 7 types of carbonate minerals and the influences on 47 values of calcium carbonate are systematically discussed for the first time most samples presented 47 offsets within the 2 sd of our analytical precision except the methane derived authigenic carbonate mdac the shift of 47 values in mdacs is attributed to the mixing effect of two types of carbonate minerals original one and isotopically altered one and the magnitude is determined by the differences of both 13c and 18o values between two endmembers regarding biogenic carbonate tested here the analytical bias of h2o2 treatment is relative small in 13c and 18o values and therefore the shift of 47 values is statistically neglectable the 13c and 18o values for most samples tested in this study became positive up to 1 7 after h2o2 treatment apart from previously well discussed mechanisms such as removal of organic contamination isotopic fractionation during the partial dissolution and dissolution of isotopic distinct carbonate compositions in the heterogeneous minerals we experimentally demonstrated carbon and oxygen isotopic exchanges between carbonate minerals and h2o2 solution for the first time the 13c and 18o values of carbonate were influenced by isotopic exchanges with atmospheric co2 in the co2 hco3 co32 system and h2o in h2o2 solution respectively rich transition metals in the authigenic carbonate minerals e g mdac travertine which catalyze h2o2 decomposition can enlarge this effect by altering h2o isotopic compositions though the small shift of 13c and 18o in biogenic carbonate observed here up to 0 6 would not change scientific interpretations and conclusions in most of previous studies cautions should be taken in the future based upon our new experimental results we suggest using a buffered h2o2 solution ph 8 isolated from atmospheric co2 to remove potential organic contaminations in biogenic carbonate for authigenic carbonate h2o2 treatment is not recommended if necessary decreasing the h2o2 concentration shortening the reaction time leaving the solution in a co2 free environment and adjusting the solution to a basic condition will improve the accuracy in isotopic analysis of these minerals

study of the diet effect on δ13c of shell carbonate of the land snail helix aspersa in experimental conditions abstract this study aims to demonstrate the influence of the metabolic co2 derived from the diet and of the atmospheric co2 on the shell carbonate 13c of the pulmonate snail helix aspersa maxima raised under controlled conditions adult snails were analyzed and compared with three hatching and 1 day old young snails stemming from the same breeding one day after the 2 day old individuals were raised during 1 month three groups of gastropods were fed with fresh lettuce c3 plant 13c 27 49 three groups with corn c4 plant 13c 11 7 and three groups ate alternately both c3 c4 the difference between the average 13c values of the adult snails on the one hand and the hatched and 1 day old snails on the other hand indicates a depletion of 2 47 therefore the isotopic parents offspring signal is not preserved the depleted ingested albumen by the snail embryo in the egg during the building of the shell could explain this depletion the c3 diet experiment gave the expected isotopic composition difference between the diet lettuce and the shells average 13cshell lettuce 13 75 0 52 this result shows a clear diet effect on the isotopic composition of the snail shells for the c4 experiment the difference in carbon isotope composition between the corn and the shell 13cshell corn yielded an average value of 4 89 0 87 the main result is that 13c is not constant and appears to depend on the type of ingested food several hypotheses can arise from this study to explain the different fractionations a differences in the quality of the two diets b differences in turnover rate for c3 and c4 feeders the groups regularly fed with mixed diet yielded 13c values showing a preferential use of c3 food for most values the c3 c4 mixed dietary alternation probably led snails to use mainly the lettuce instead of the corn powder

strontium isotope composition as a tracer of calcium sources in two forest ecosystems in belgium the two main sources of ca in forest ecosystems are mineral weathering release and atmospheric inputs we use the 87 sr 86 sr isotopic ratio sr is used as a proxy for ca to determine the ca contribution from atmospheric deposition input in two forest ecosystems beech stands growing on soils formed from parent materials with contrasting total ca contents and isotopic ratios pleistocene loess in central belgium acid leached soil and lower devonian shales in the ardenne massif of high belgium ochreous brown earth the 87 sr 86 sr ratio and the ca and sr contents were measured in bulk precipitation in vegetation beechwood growth rings and leaves and in main soil horizons total acid extractable and labile pools the relative contributions of atmospheric input and soil mineral weathering to vegetation were calculated using mixing equations calculations based on sr isotope ratios of bulk precipitation end member 1 87 sr 86 sr close to ocean water 0 7090 0 1 m hcl extractable soil fraction end member 2 and beech wood mixing compartment indicate that about 43 central belgium and 39 ardennes of sr uptake originates from atmospheric inputs for ca the contributions of atmospheric input are 75 and 78 respectively these estimations are however very sensitive to the choice of the appropriate 87 sr 86 sr and sr ca ratios for the weathering end member the isotopic composition of the mineral source is estimated from the soil mineralogical composition and the relative weatherability of the sr bearing minerals due to soil processes mineral weathering element recycling and geomorphological events addition of allochtonous minerals to the autochtonous pool inherited from the local bedrock the distribution of minerals in both soil profiles is heterogeneous and varies from horizon to horizon which horizons are relevant and which soil pool total soil acidextractable fraction or labile pool should be selected for isotopic measurement of the weathering end member is therefore open to uncertainty the choice of the appropriate 87 sr 86 sr and sr ca ratios for the weathering end member is discussed our results emphasize the importance of the atmospheric contribution of ca for tree mineral nutrition in the studied forest stands suggesting that these ecosystems on acid soils are sensitive to chemical changes in the atmospheric environment e g acid depositions associated with decreasing input of atmospheric cations our results support therefore

mixed geothermal and shallow meteoric origin of opal and calcite beds in pliocene lower pleistocene axial fluvial strata southern rio grande rift rincon hills new mexico u s a abstract exposed in upper pliocene fluvial strata in the eastern rincon hills and adjacent jornada del muerto basin southern rio grande rift new mexico usa are five laterally continuous beds 0 2 to 1 0 m thick of opal ct which straddle the east rincon hills normal fault four of these opal beds change basinward over 1 km or less to white friable lithofeldspathic sand with opal glaebules and then to microcrystalline calcite the opal and calcite generally replaced fine sand at shallow depths although two beds locally precipitated from standing water 87sr 86sr values 0 71301 to 0 71724 of the opal beds are consistent with precipitation from an advecting high temperature geothermal fluid that flowed through bedrock and or from a high temperature geothermal fluid derived from a deep crustal source carbon and oxygen isotopic values 13cpdb 7 1 to 0 6 18opdb 9 1 to 5 6 of the calcite beds lie between and overlap those of paleozoic carbonate and pliocene paleosol calcite suggesting precipitation from a mixture of a high temperature geothermal fluid that interacted with paleozoic carbonates and shallow meteoric groundwater for which paleosol calcite is a proxy the geothermal fluids are interpreted to have upwelled along the east rincon hills fault flowed laterally at or just below the surface and precipitated opal in response to rapid cooling and evaporation downflow precipitation of opal glaebules occurred as a result of decreasing silica concentrations and perhaps by mixing with shallow meteoric groundwater from which calcite precipitated probably by co2 degassing

an expression for the overall oxygen isotope fractionation between the sum of dissolved inorganic carbon and water 1 stable oxygen isotope fractionation factors s between individual dissolved carbonate species co2 aq h2co3 hco3 co32 and water and their sum co2 aq h2co3 hco3 co32 and water are fundamental geochemical parameters while values of and have recently been examined an overall mass balance for stable oxygen isotopes in the carbonate system still needs to be derived the theoretical treatment of this mass balance is not trivial in contrast to e g stable carbon isotopes because 1 oxygen is exchanged with h2o and 2 complications arise from the nature of the oxygen mole fractions i use the recently reported individual s to derive an expression for the overall oxygen isotope fractionation between and water this allows the calculation of h2o at any given ph of the solution the result differs from a relationship published earlier and implications for previous studies are discussed numerical routines in matlab and excel for the present calculation have been developed and are available as auxiliary material software s1 applications of the expression include for example examination of biomineralization mechanisms and corrections to isotopic paleotemperature equations the latter application can significantly alter reconstructions of phanerozoic climate change

13c 18o isotope signatures and clumped isotope thermometry in foraminifera and coccoliths accurate constraints on past ocean temperatures and compositions are critical for documenting climate change and resolving its causes most proxies for temperature are not thermodynamically based appear to be subject to biological processes require regional calibrations and or are influenced by fluid composition as a result their interpretation becomes uncertain when they are applied in settings not necessarily resembling those in which they were empirically calibrated independent proxies for past temperature could provide an important means of testing and or expanding on existing reconstructions here we report measurements of abundances of stable isotopologues of calcitic and aragonitic benthic and planktic foraminifera and coccoliths relate those abundances to independently estimated growth temperatures and discuss the possible scope of equilibrium and kinetic isotope effects the proportions of 13c 18o bonds in these samples exhibits a temperature dependence that is generally similar to that previously been reported for inorganic calcite and other biologically precipitated carbonate containing minerals apatite from fish reptile and mammal teeth calcitic brachiopods and molluscs aragonitic coral and mollusks most species that exhibit non equilibrium 18o 16o 18o and 13c 12c 13c ratios are characterized by 13c 18o bond abundances that are similar to inorganic calcite and are generally indistinguishable from apparent equilibrium with possible exceptions among benthic foraminiferal samples from the arctic ocean where temperatures are near freezing observed isotope ratios in biogenic carbonates can be explained if carbonate minerals generally preserve a state of ordering that reflects the extent of isotopic equilibration of the dissolved inorganic carbon species

oxygen isotope composition of living land snail shells data from italy sixty seven shells of living land snails were selected from 31 different localities across italy to investigate the relationships between their oxygen isotopic composition 18os and the mean value of local rainfall 18op despite the difficulty for some localities to correctly estimate the oxygen isotopic composition of local rainfall a good relationship was found this indicates that the oxygen isotopic composition of environmental water used by the snails is in italy strictly related to that of the local meteoric precipitation however the relationship found is substantially different from that previous established for central europe indicating that regional climatic conditions are important in defining the final isotopic composition of land snail shells moreover these equations may not hold for different climatic conditions existing during for instance glacial and interglacial periods the data also show that isotopic differences among species are relatively narrow and that they may depend on ecological factors i e style of life rather than any clearly identifiable different vital offset

carbon isotope signatures from land snail shells implications for palaeovegetation reconstruction in the eastern mediterranean in this study we compare carbon isotope values in modern helix melanostoma shell carbonate 13cshell from the gebel al akhdar region of libya with carbon isotope values in h melanostoma body tissue 13cbody local vegetation 13cplant and soil 13csoil all vegetation in the study area followed the c3 photosynthetic pathway however the 13cplant values of different species formed two distinct isotopic groups this can be best explained by different water use efficiencies with arid adapted species having significantly more positive 13cplant values than less water efficient species the ranges and means of 13cbody and 13cplant were statistically indistinguishable from one another suggesting that 13cbody was primarily a function of local vegetation composition h melanostoma 13cshell reflected the 13cplant of local vegetation with a positive offset between body diet and shell of 14 5 1 4 therefore in the gebel al akhdar where only c3 plants are present higher mean 13cshell values likely reflect greater abundances of water efficient c3 plants in the snails diet and therefore in the landscape whilst lower mean 13cshell values likely reflect the consumption of less water efficient c3 plants the distribution of these plants is in turn affected by environmental factors such as rainfall these findings can be applied to archaeological and geological shell deposits to reconstruct late pleistocene to holocene vegetation change in the southeast mediterranean

stable isotope composition of land snail body water and its relation to environmental waters and shell carbonate abstract day to day and within day diel variations in d and 18 o of the body water of the land snail theba pisana were studied at a site in the southern coastal plain of israel three phases of variation which relate to isotopic changes in atmospheric water vapor were distinguished 1 on rain days snail water becomes isotopically depleted approximately in the direction of the rain isotope values but always less depleted in d as is atmospheric water vapor 2 during the 1 3 days following a rain the snail water becomes isotopically enriched along a line with slope 18 o space this relates to an increasing influence of humidity derived from the mediterranean sea 3 a period of relative stability of the isotopic composition persists until the next rain event the isotopic variations can be explained by isotopic equilibration with atmospheric water vapor and or uptake of dew derived therefrom during the winter when the snails are active there is only very minor enrichment in 18 o relative to equilibrium with water vapor or dew apparently as a result of metabolic activity but this enrichment becomes pronounced after long periods of inactivity within day variation in body water isotopic composition is minor on non rain days shell carbonate is enriched in 18 o by ca 1 2 relative to equilibrium with body water in most regions the isotopic composition of atmospheric water vapor or dew is a direct function of that of rain because the isotopic composition of snail body water is related to that of atmospheric water vapor and the isotopic composition of shell carbonate in turn is related to that of body water land snail shell carbonate 18 o should provide a reliable indication of rainfall 18 o however local environmental conditions and the ecological properties of the snail species must be taken into account

a process based model for non equilibrium clumped isotope effects in carbonates abstract the equilibrium clumped isotope composition of carbonate minerals is independent of the composition of the aqueous solution however many carbonate minerals grow at rates that place them in a non equilibrium regime with respect to carbon and oxygen isotopes with unknown consequences for clumped isotopes we develop a process based model that allows one to calculate the oxygen carbon and clumped isotope composition of calcite as a function of temperature crystal growth rate and solution ph in the model carbon and oxygen isotope fractionation occurs through the mass dependent attachment detachment kinetics of the isotopologues of hco 3 and co2 3 to and from the calcite surface which in turn influence the clumped isotope composition of calcite at experimental and biogenic growth rates the mineral is expected to inherit a clumped isotopic composition that is similar to that of the dic pool which helps to explain 1 why different organisms share the same clumped isotope versus temperature calibration curves 2 why many inorganic calibration curves are slightly different from one another and 3 why foraminifera coccoliths and deep sea corals can have near equilibrium clumped isotope compositions but far from equilibrium carbon and oxygen isotope compositions some aspects of the model can be generalized to other mineral systems and should serve as a useful reference in future efforts to quantify kinetic clumped isotope effects

a reassessment of the precision of carbonate clumped isotope measurements implications for calibrations and paleoclimate reconstructions carbonate clumped isotopes offer a potentially transformational tool to interpret earth s history but the proxy is still limited by poor interlaboratory reproducibility here we focus on the uncertainties that result from the analysis of only a few replicate measurements to understand the extent to which unconstrained errors affect calibration relationships and paleoclimate reconstructions we find that highly precise data can be routinely obtained with multiple replicate analyses but this is not always done in many laboratories for instance using published estimates of external reproducibilities we find that typical clumped isotope measurements three replicate analyses have margins of error at the 95 confidence level cl that are too large for many applications these errors however can be systematically reduced with more replicate measurements second using a monte carlo type simulation we demonstrate that the degree of disagreement on published calibration slopes is about what we should expect considering the precision of 47 data the number of samples and replicate analyses and the temperature range covered in published calibrations finally we show that the way errors are typically reported in clumped isotope data can be problematic and lead to the impression that data are more precise than warranted we recommend that uncertainties in 47 data should no longer be reported as the standard error of a few replicate measurements instead uncertainties should be reported as margins of error at a specified confidence level e g 68 or 95 cl these error bars are a more realistic indication of the reliability of a measurement

clumped isotopic signatures in land snail shells revisited possible palaeoenvironmental implications abstract it is crucial to understand the clumped isotope compositions 47 of modern land snail shells and their relationship with environmental parameters for palaeoenvironmental studies previous studies have shown significant variations in relationships between snail shell 47 and ambient air temperature and the reliability of shell 47 in indicating air temperature remains uncertain this study examined the shell 47 from china with mean annual temperatures ranging from 5 to 23 c and the snail body fluid 18o estimated from shell 18o and 47 derived temperatures for all snails studied in this study site averaged 47 values yield snail calcification temperatures ranging from 25 to 36 c which are higher than expected in either environmental temperatures or estimated snail activity temperatures we suggest that snails up regulate their body temperatures towards their preferred living conditions likely through behaviour or and physiology adaptation especially at low temperature environments which is likely significant than observed previously 47 disequilibrium associated with co2 degassing during snail calcification is potential but it could possibly be corrected by using an empirical calibration based on natural land snails varying degrees of 18o enrichment 8 relative to rainwater are observed in snail body fluids possibly due to variable evaporation during shell calcification coupled with model calculations the relationship between snail body fluid 18o and rainwater 18o could be improved by using 47 based temperature and 18o thermometry if snails prefer to be active at 90 relative humidity this study highlights the importance of land snail shell 47 coupled with shell 18o to indicate temperature and rainwater 18o at micro environments scales

high regional climate sensitivity over continental china constrained by glacial recent changes in temperature and the hydrological cycle the east asian monsoon is one of earth s most significant climatic phenomena and numerous paleoclimate archives have revealed that it exhibits variations on orbital and suborbital time scales quantitative constraints on the climate changes associated with these past variations are limited yet are needed to constrain sensitivity of the region to changes in greenhouse gas levels here we show central china is a region that experienced a much larger temperature change since the last glacial maximum than typically simulated by climate models we applied clumped isotope thermometry to carbonates from the central chinese loess plateau to reconstruct temperature and water isotope shifts from the last glacial maximum to present we find a summertime temperature change of 6 7 c that is reproduced by climate model simulations presented here proxy data reveal evidence for a shift to lighter isotopic composition of meteoric waters in glacial times which is also captured by our model analysis of model outputs suggests that glacial cooling over continental china is significantly amplified by the influence of stationary waves which in turn are enhanced by continental ice sheets these results not only support high regional climate sensitivity in central china but highlight the fundamental role of planetary scale atmospheric dynamics in the sensitivity of regional climates to continental glaciation changing greenhouse gas levels and insolation

a revised calibration of the clumped isotope thermometer abstract a growing number of materials and environmental settings are studied using the carbonate clumped isotope 47 thermometer the method has been applied in both biogenic and non biogenic carbonate systems in marine and terrestrial settings over a wide range of geological timescales the current 47 temperature calibration gives good temperature estimates for most biogenic materials however systematic biases are commonly observed at low temperatures in this study we report additional calibration data that covers a wider temperature range at more evenly distributed temperatures and are measured at higher analytical precision than the original calibration combining these data with the original calibration yields a 47 t relationship that is similar to the original calibration though slightly less steep 47 0 0526 0 0025 10 6 t 2 0 0520 0 0284 this revised calibration is in better agreement with biogenic carbonates including those grown at low temperatures the difference between the original and revised calibrations is significant for carbonates forming below 16 c or above 49 c 47 values of 0 68 and 0 56 additionally we include a comprehensive analysis of the sources of error associated with 47 measurements and estimated temperatures and recommend measurement strategies for obtaining the desired precision as an illustration we apply the revised calibration and uncertainty analysis to 3 previously published studies at low temperatures the revised calibration results in significant differences from the original calibration and hence affects the interpretation of the environmental signal recorded in light of our 47 errors analysis in cases where the temperature signals are small we find that replicate analyses are critical to identify a temperature signal

seasonal evolution of the cold pool gyre in the western irish sea an extensive cruise program during 1994 1995 and 1996 provided observations that describe the seasonal evolution of the three dimensional density field in the western irish sea a cold dense pool flanked by strong nearbed density gradients was present from may until october in spring salinity had a dominant influence on the density structure but from june until october temperature controlled the density stratification the trajectories of 55 satellite tracked argos drifters demonstrated the existence of the cyclonic circulation pattern that constitutes the western irish sea gyre and defined the gyre s spatial extent several distinct recirculation paths were observed and the implications for planktonic organisms of the seasonal variability in the recirculation are discussed drifter speeds were in good agreement with geostrophic calculations based on the observed density field and with de tided acoustic doppler current profiler adcp measurements the dynamical significance of strong nearbed gradients bottom fronts is highlighted the location of the dynamically significant baroclinicity below the level of wind mixing explains the persistence of the cold pool and cyclonic circulation until late october the dataset described here is valuable for environmental management purposes and it facilitates testing of the prognostic capabilities of the present generation of density advecting numerical models

characterizing nutrient pathways in quebec canada vineyards insight from stable and radiogenic strontium isotopes abstract soils are a crucial interface of earth s critical zone responsible for the biogeochemical cycling of mineral nutrients while the sources of essential nutrients such as ca and sr in plants have been widely studied the processes by which these nutrients are transferred from the soil to the plants is less clear we present new evidence for systematic nutrient fractionation between soils grapes and wines from five vineyards from the quebec terroir canada using the novel stable sr 88 86sr isotope system we coupled this approach with traditional radiogenic 87sr 86sr measurements on the same samples bulk soils labile fraction of these soils whole grapes and wines from five vineyards from the quebec terroir canada to ensure that variations in 88 86sr values were provoked by processes involved in sr transfer instead of mixing between different sources the 88 86sr values generally decrease from the bulk to the labile fractions of the soils to the grapes a decrease in the difference between the soil fractions 88 86srbulk labile with increasing 88 86sr values in the labile fraction is interpreted to reflect increasing pedogenic mineral precipitation and higher soil fertility the depleted 88 86sr values of the grapes are consistent with a preferential uptake of lighter isotopes by plants this effect is magnified in soils showing higher secondary mineral precipitation an increase in the 88 86sr values from the grapes to the wines reflects the separation of the skin seeds and the juice pulp enriched in 88sr in the winemaking process this mixing relationship is supported by a correlation between the sr concentrations and the 88 86sr values of the wines and grapes these findings suggest promising new applications of stable sr isotopes values for studying soil fertility and the impact of nutrient availability for plant growth in agricultural ecosystems as well as the impact of the maceration processes in the production of wine the overall similarity of 87sr 86sr ratios of the labile soil fractions grapes and wines from the same vineyard support the hypothesis of a same sr source from the soil solution to its transfer to the grape and wine and confirm the potential of the 87sr 86sr ratios as a proxy for geographic provenance of wine however slightly lower 87sr 86sr ratios in the grape pulps by 0 00040 on average compared to the skins and seeds suggest that the sources of nutrients available for plant uptake vary during the vegetative cycle the grape seeds and skins formed in the early growth cycle are characterized by rapid growth due to enhanced rhizosphere activity enhanced mineral dissolution providing higher nutrient levels the enhanced mineral solubility results in higher 87sr 86sr ratios in the skin and seeds derived from enhanced dissolution of 87sr enriched silicate minerals in contrast the pulp develops later in the growth cycle when rhizosphere activity and mineral solubility is reduced resulting in a lesser contribution from silicate minerals and thus reflect a higher proportion of dissolved carbonate contributing to the lower 87sr 86sr ratios of the pulps

determination of sr and ca sources in small tropical catchments la selva costa rica a comparison of sr and ca isotopes summary a comparative study of sr and ca isotopes was conducted to assess solute sources and effects of biogeochemical processes on surface water and groundwater in four small tropical catchments located at la selva biological station costa rica variable concentrations of dissolved sr 2 and ca 2 in the catchments are related to mixing of waters from different origin three catchments are influenced by high solute bedrock groundwater while another catchment is primarily supplied by local recharge 87 sr 86 sr ratios were employed to discriminate contributions from mineral weathering and atmospheric sources solutes in bedrock groundwater have a predominant geogenic origin whereas local recharge is characterized by low solute inputs from rainwater and minor in situ weathering releases from nutrient depleted soils bedrock groundwater contributes more than 60 of dissolved sr 2 to surface discharge in the salto saltito and arboleda catchments whereas the taconazo catchment receives more than 95 of dissolved sr 2 from rainwater 44 40 ca values of dissolved ca 2 vary greatly in the catchments mainly as a result of heterogeneous ca isotope compositions of the contributing sources based on differences in 44 40 ca values two distinct bedrock groundwaters discharging at the salto and the arboleda catchments are suggested effects of biological processes in the plant soil system on solute generation in the catchments are indicated by variable ca sr ratios however these effects cannot clearly be assessed by ca isotopes due to the strong heterogeneity of 44 40 ca values of ca 2 sources and high ca 2 concentrations in bedrock groundwater

strontium stable isotopes fractionate in the soil environments abstract this study shows that the stable isotopic composition of strontium the 88sr 86sr ratio expressed as 88 86sr value relative to the nbs987 standard varies significantly in sedimentary terrestrial environments the abundances of 86sr 88sr isotopes were analyzed by mc icp ms nu plasma all studied rocks and waters show 88 86sr values that are distinctly different from the measured nbs987 standard yielding 0 01 0 05 all errors are reported as 2 modern corals from the northern gulf of aqaba red sea yielded significantly different value than seawater 88 86sr 0 22 0 07 compared to 0 35 0 06 respectively in an excellent correlation with the 88 86sr analyses reported by fietzke and eisenhauer fietzke j eisenhauer a 2006 determination of temperature dependent stable strontium isotopes 88sr 86sr fractionation via bracketing standard mc icp ms geochm geophys geosyst 7 no 8 on other coral samples all carbonate samples that originated in the marine environment corals porites and acropora from the northern gulf of aqaba cretaceous limestone and runoff from the judea mountains as well as lacustrine evaporitic aragonite dead sea and red sea and atlantic seawater yield an average 88 86sr value of 0 26 0 1 on the other hand secondary materials products of chemical weathering from the terrestrial environment of the judea mountain such as terra rossa soil and speleothem calcite that derives its sr from the above lying soil yielded significantly lower 88 86sr value of 0 17 0 06 this indicates that strontium isotopes fractionate in the soil environment calling for a possible development of strontium isotopes as a tracer for processes of chemical weathering and pedogenesis

clumped and stable isotopes of land snail shells on the chinese loess plateau and their climatic implications abstract we report stable 13cshell 18oshell and clumped isotope 47 compositions of modern and last glacial fossil snail shell carbonates from the luochuan and weinan sections on the central and southern chinese loess plateau clp our study reveals that the average 47 temperature t47 of modern snails is consistent with monitored temperatures during the snail growing season at the studied locations and is 10 c higher than that of fossil snails from glacial time moreover the average 13cshell of modern snails is more depleted than that of fossils we argue that the 13cshell cannot record changes in plant communities i e the c3 c4 ratio on the clp and may mainly indicate arid conditions with depleted values reflecting reduced aridity additionally the reconstructed snail body water 18o 18owater of modern snails is more enriched than 18o in modern growing season precipitation and 18owater of fossils this contrast may be related to the high degree of evaporative enrichment of environmental water 18o in the body ingested by modern snails under warm conditions therefore we suggest that using 18oshell to directly reconstruct the oxygen isotopes of precipitation is difficult and that higher 18oshell and 18owater values probably indicate higher environmental temperature stronger evaporative enrichment on glacial interglacial timescales on the clp

calibration of dolomite clumped isotope thermometry abstract use of the clumped isotope thermometer to decipher environments of dolomite formation has been inhibited by a lack of empirical data from dolomites formed at known temperatures calibrations for aragonite calcite siderite and apatite indicate that a universal 47 temperature relationship may exist across all carbonate bearing mineral phases however theoretical modeling and proposed acid fractionation differences have suggested that dolomites may have different 47 values relative to calcites precipitated at the same temperature to resolve this question we analyzed five synthetic and four natural dolomites formed at known temperatures these included synthetic dolomites grown in mg ca cl solutions at temperatures of 200 250 c and natural samples constrained by fluid inclusion analyses 70 c climate 28 and 27 c and deep ocean borehole temperature 21 c when using calcite 47 acid fractionation values these data result in a calibration line that is statistically indistinguishable from other clumped isotope calibrations at least with current precision we find no evidence for a consistent dolomite 47 offset these results further support a universal calibration for carbonate clumped isotope thermometry and enable new investigations into conditions of dolomite formation

observations of a seasonal jet like circulation at the central north sea cold pool margin in june july 1996 a survey of the offshore region between the north east coast of england and the dogger bank was undertaken using towed and conventional profiling ctd s and satellite tracked drifters strong bottom fronts bounded a pool of cold dense bottom water isolated below the seasonal thermocline these features extend continuously for 500 km along the 40 m contour from the firth of forth to the eastern end of the dogger bank geostrophic current estimates and drifter trajectories demonstrate the existence of persistent and narrow 10 15 km cores of cyclonic near surface flow cold bottom water to the left with velocities in excess of 0 1 m s 1 the results are consistent with a seasonal baroclinic flow skirting the north east coast of england which provides a direct pathway for material and fish larvae from coastal regions to the northern dogger bank and central north sea

calcium isotope constraints on the uptake and sources of ca2 in a base poor forest a new concept of combining stable δ44 42ca and radiogenic eca signals abstract plant available reserves of major base cations ca 2 and mg 2 decreased markedly in soils over the past century thus posing a potential threat to forest ecosystem health trees are thought to obtain dissolved ca 2 ions mainly from an easily accessible soil water reservoir also termed the exchangeable cation pool the status of ca reserves in this soil pool is sensitive to anthropogenic perturbations such as soil acidification induced by acid rain and or excessive timber harvesting here we show that in a base poor forest of the northeastern usa i e wachusett mountain massachusetts the exchangeable ca pool of deeper mineral soils has a unique isotope signature that is significantly enriched in the radiogenic 40 ca due to the dissolution of k rich silicate minerals such as biotite using a simple isotope mass balance and assuming that the input of ca from biotite has a e ca signature of 16 the results of our calculation indicate that the weathering of biotite may supply a sizeable fraction up to 25 of ca 2 ions into the exchangeable cation pool of deeper mineral soils importantly samples of local vegetation i e woody tissues of red oak show no detectable excess of the radiogenic 40 ca and based on our model the upper limit of a possible biotite derived ca contribution in vegetation is estimated at 5 we also found no evidence of the radiogenic 40 ca signal in the samples of forest floor and the uppermost organic rich soils 0 15 cm depth which in turn suggest that over the long term development of the forest and its organic matter accumulation the vegetation growth must have also relied primarily on the non radiogenic ca sources based on our experimental data such sources may include i wet atmospheric deposition ii the organically complexed ca in topsoil horizons and iii chemical weathering and or fungal mediated dissolution of apatite and ca rich plagioclase hence our stable and radiogenic ca isotope data indicate that the studied base poor forest is able to bypass the exchangeable cation pool of deeper i e below 15 cm mineral soils and still manages to meet its nutritional requirements with respect to ca another important implication of this study is that the organically complexed ca in the topsoil horizon 0 15 cm depth has to be tightly bound to the ion exchange sites otherwise the large radiogenic 40 ca signatures present in the exchangeable cation pool of deep mineral soils would be swamped by the downward gravitational flux of non radiogenic ca from the decaying organic matter and litterfall hence the limited mobility of the organically complexed ca in soils and its tight biological cycling could explain the lack of a significant impact of vegetation on the ca isotope systematics observed in large rivers

radiogenic and stable strontium isotopes in provenance studies a review and first results on archaeological wood from shipwrecks abstract different approaches are used to study wood provenance but most of them are based on tracers in wood that are generally controlled by climatic factors the strontium isotopic ratio 87 sr 86 sr in trees and soils is related to the signature of the local bedrock despite being used in diverse archaeological studies sr isotopes have rarely been used to trace the provenance of archaeological wood and especially wood from shipwrecks in addition recent analytical advances have allowed the detection of mass dependent fractionation of sr isotopes during biogeochemical processes as reflected in the variation of 88 86 sr values between different environmental materials the 88 86 sr values could be used in conjunction with the 87 sr 86 sr isotope ratio to improve constraints on the sources of sr in the archaeological materials being studied this paper discusses the potential and limitations of using both of these sr isotope ratios to trace the provenance of wood from shipwrecks we review the 87 sr 86 sr and 88 86 sr variations in rocks waters soils plants and other living organisms and discuss how to determine the local sr isotopic signature of potential sites we also compile a list of known wood post mortem modifications in seawater possible implications in terms of the modification of the original sr isotope ratios of wood during storage in seawater are illustrated through preliminary observations this paper points out some limitations and perspectives for using sr isotopes in provenancing wood from shipwrecks and suggests future research to test and apply this approach for tracing the origin of archaeological wood

iron age utilization of silver fir abies alba wood around the heuneburg local origin or timber import abstract the larger area of and around the early iron age fortress heuneburg is focus of decades of archaeological excavations and observations additionally to deciduous oak quercus sp known as the main timber during this period middle to late hallstatt c 750 450 bce silver fir abies alba was found recently on the heuneburg plateau itself and its surroundings silver fir is now recognized being a significant source of timber during the iron age in a region where its nowadays natural status is debated and its occurrence is rare the aim of this study was to determine the possible source of the used timber which might have been taken from the some 80 km distant abies rich black forest on the primary bed rock or from stands developed on younger geological formations nearer to the site for this approach radiogenic strontium isotope 87sr 86sr analyses were performed on waterlogged wood and on charcoal remains buried in four archaeological contexts from late hallstatt period around the princely seat heuneburg the 87sr 86sr ratios were compared to those of living trees soils and sediments with respect to the diverse geological background the geological ground of the archaeological wood was narrowed down to molasse for three structures and to loess moraine or mass chalk sites for one the isotopic ratio thus points to growing sites more in the surrounding of the concerned archaeological sites and a more distant black forest source can be ruled out local evidence of abies was additionally supported by palynological data from four archaeological sites and by anthracological data from a funeral context near the heuneburg

the history and variability of the east asian paleomonsoon climate abstract changes in the east asian paleomonsoon reflect interactions between the global atmosphere ocean land and ice systems and are also an expression of their combined effect within the boundary conditions imposed by the east asian continent and solar radiation the history of the east asian monsoon is an alternation between dominance by the dry cold winter and warm humid summer monsoons high resolution eolian sequences preserved in the chinese loess plateau reveal that the east asian monsoon may have commenced at least 7 2 ma ago they also provide evidence indicating that the pulsed uplift of the tibetan plateau at about 3 4 and 7 2 ma may have played an important role in inducing climate change the palaeoclimatic records of the last glacial cycle show high frequency variability on time scales of 1000 year or even shorter and instability of the east asian paleomonsoon system the high frequency variability could be due to a non linear response to orbital forcing or a result of the coupling processes between different components of the global system cold air activity in northern high latitudes the trans equatorial air streams from the southern hemisphere and possibly enso may have played an important role in east asian monsoon variability the synchroneity of all the palaeoclimatic events along the polar equator polar pep transect is still an open question correlation of limited palaeoclimatic records for the last 30 kyr obtained from east asia and australia suggests that the trans equatorial air streams driven by the monsoon and trade winds may have had an influence on opposite hemispheres

clumped isotope geochemistry the study of naturally occurring multiply substituted isotopologues clumped isotope geochemistry is concerned with the state of ordering of rare isotopes in natural materials that is it examines the extent to which rare isotopes d 13 c 15 n 18 o etc bond with or near each other rather than with the sea of light isotopes in which they swim abundances of isotopic clumps in natural materials are influenced by a wide variety of factors in most cases their concentrations approach within ca 1 relative the amount expected for a random distribution of isotopes deviations from this stochastic distribution result from enhanced thermodynamic stability of heavy isotope clumps slower kinetics of reactions requiring the breakage of bonds between heavy isotopes the mass dependence of diffusive and thermo gravitational fractionations mixing between components that differ from one another in bulk isotopic composition biochemical and photochemical fractionations that may reflect combinations of these simpler physical mechanisms and in some cases other processes we do not yet understand although clumped isotope geochemistry is a young field several seemingly promising applications have already emerged most importantly it appears that proportions of 13 c 18 o bonds in carbonate minerals are sensitive to their growth temperatures independent of bulk isotopic composition thus clumped isotope analysis of ancient carbonates can be used as a quantitative paleothermometer that requires no assumptions about the 18 o of waters from which carbonates grew this approach has been used to reconstruct marine temperatures across the phanerozoic reaching back to the silurian terrestrial ground temperatures across the cenozoic thermal histories of aqueously altered meteorites among other applications clumped isotope geochemistry is also placing new constraints on the atmospheric budget and stratospheric photochemistry of co 2 and should be capable of placing analogous new constraints on the budgets of other atmospheric gases finally this field could be extended to encompass sulfates volatile hydrocarbons organic moieties and other materials

13c18o clumping in speleothems observations from natural caves and precipitation experiments the oxygen isotope composition of speleothems is an important proxy of continental paleoenvironments because of its sensitivity to variations in cave temperature and drip water 18 o interpreting speleothem 18 o records in terms of absolute paleotemperatures and 18 o values of paleo precipitation requires quantitative separation of the effects of these two parameters and correcting for possible kinetic isotope fractionation associated with precipitation of calcite out of thermodynamic equilibrium carbonate clumped isotope thermometry based on measurements of 47 a geochemical variable reflecting the statistical overabundance of 13 c 18 o bonds in co 2 evolved from phosphoric acid digestion of carbonate minerals potentially provides a method for absolute speleothem paleotemperature reconstructions independent of drip water composition application of this new technique to karst records is currently limited by the scarcity of published clumped isotope studies of modern speleothems the only modern stalagmite reported so far in the literature yielded a lower 47 value than expected for equilibrium precipitation possibly due to kinetic isotope fractionation here we report 47 values measured in natural speleothems from various cave settings in carbonate produced by cave precipitation experiments and in synthetic stalagmite analogs precipitated in controlled laboratory conditions designed to mimic natural cave processes all samples yield lower 47 and heavier 18 o values than predicted by experimental calibrations of thermodynamic equilibrium in inorganic calcite the amplitudes of these isotopic disequilibria vary between samples but there is clear correlation between the amount of 47 disequilibrium and that of 18 o even pool carbonates believed to offer excellent conditions for equilibrium precipitation of calcite display out of equilibrium 18 o and 47 values probably inherited from prior degassing within the cave system in addition to these modern observations clumped isotope analyses of a flowstone from villars cave france offer evidence that the amount of disequilibrium affecting 47 in a single speleothem can experience large variations at time scales of 10 kyr application of clumped isotope thermometry to speleothem records calls for an improved physical understanding of dic fractionation processes in karst waters and for the resolution of important issues regarding equilibrium calibration of 47 in inorganic carbonates

the summer gyre in the western irish sea shelf sea paradigms and management implications a cyclonic near surface gyre has been discovered above the deep western irish sea basin the gyre present in spring and summer each year is formed when stratification isolates a dome of cold bottom water which then drives a baroclinic circulation simultaneous observations using ship mounted broad band acoustic doppler current profiler towed undulating ctd conductivity temperature depth and satellite tracked drifting buoys reveal the detailed horizontal and vertical structure of the gyre gyre dynamics have been investigated using a three dimensional steady diagnostic circulation model with realistic bathymetry the role of the gyre within the existing bowden simpson paradigm of shelf circulation is discussed knowledge of seasonal gyre systems is important when formulating management strategies for example there is evidence that the irish sea gyre acts as a retention system for the planktonic larvae of the commercially valuable norway lobster nephrops norvegicus linnaeus 1758 which inhabits the geographically isolated mud patch beneath the gyre moreover in the event of an accidental summer time spill the gyre could also act to retain contaminants suggesting that this system is at disproportionate risk from environmental damage

stable isotope ecology of land snails from a high latitude site near fairbanks interior alaska usa abstract land snails have been investigated isotopically in tropical islands and mid latitude continental settings while high latitude locales where snails grow only during the summer have been overlooked this study presents the first isotopic baseline of live snails from fairbanks alaska 64 51 n a proxy calibration necessary prior to paleoenvironmental inferences using fossils 13c values of the shell 10 4 0 4 and the body 25 5 1 0 indicate that snails consumed fresh and decayed c3 plants and fungi a flux balance mixing model suggests that specimens differed in metabolic rates which may complicate paleovegetation inferences shell 18o values 10 8 0 4 were 4 higher than local summer rain 18o if calcification occurred during summer a flux balance mixing model suggests that snails grew at temperatures of 13 c rainwater 18o values of 15 and relative humidity of 93 results from fairbanks were compared to shells from san salvador bahamas at 24 51 n average annual 18o values of shells and rainwater samples from the bahamas were both 10 18o enriched with respect to seasonal summer alaskan samples at a coarse latitudinal scale shell 18o values overwhelmingly record the signature of the rainfall during snail active periods while tropical snails record annual average environmental information high latitude specimens only trace summer season climatic data

carbonate clumped isotope thermometry of deep sea corals and implications for vital effects here we calibrate the carbonate clumped isotope thermometer in modern deep sea corals we examined 11 specimens of three species of deep sea corals and one species of a surface coral spanning a total range in growth temperature of 2 25 c external standard errors for individual measurements ranged from 0 005 to 0 011 average 0 0074 which corresponds to 1 2 c external standard errors for replicate measurements of 47 in corals ranged from 0 002 to 0 014 average 0 0072 which corresponds to 0 4 2 8 c we find that skeletal carbonate from deep sea corals shows the same relationship of 47 the measure of 13 c 18 o ordering to temperature as does inorganic calcite in contrast the 13 c and 18 o values of these carbonates measured simultaneously with 47 for every sample differ markedly from equilibrium with seawater i e these samples exhibit pronounced vital effects in their bulk isotopic compositions we explore several reasons why the clumped isotope compositions of deep sea coral skeletons exhibit no evidence of a vital effect despite having large conventional isotopic vital effects

fortnightly variation in the bottom thermal front and associated circulation in a semienclosed sea abstractsummer hydrographic data from 1971 to 2000 demonstrate the presence of bottom cold water bcw and a bottom thermal front around the bcw in a semienclosed sea in the seto inland sea of japan the horizontal gradient of water temperature across the bottom front was larger in neap tide than in spring tide which is the opposite the pattern observed in the fortnightly variations in other areas e g the irish sea a numerical model for the inland sea reproduced the presence of bcw and a bottom front as well as the same fortnightly variation in the horizontal gradient of water temperature across the bottom front as in observational data being the same bcw as those in other areas the presence of bcw in the inland sea is also caused by spatial variation in tidal mixing the intensification of the bottom front in neap tide in the inland sea results from a combination of tidal mixing and horizontal advection of warm water to the bcw the presence of a bottom residual current in the direction across th

paleoclimate reconstruction using carbonate clumped isotope thermometry carbonate clumped isotope thermometry is a relatively new paleotemperature proxy based on measurements of the degree of ordering of 13 c and 18 o into bonds with each other making the 13 c 18 o 16 o 2 2 ion group in lattices of carbonate minerals this technique has several unusual properties that complement existing methods of paleoclimate reconstruction most importantly it is based on a homogeneous isotope exchange equilibrium and thus constrains temperature independent of the isotopic composition of waters from which carbonates grew this method also appears to be generally insensitive to vital effects that compromise many other paleothermometers based on the chemical properties of biominerals or organic matter at least for those organisms that have been subjected to systematic study to date corals and foraminifera however discrepancies among some calibrations particularly at low temperatures may point toward the existence of vital effects in mollusks and other organisms this review discusses the principles and calibrations of the technique its uses in combination with conventional stable isotope measurements to constrain the 18 o of past waters preservation of paleotemperatures in ancient materials as well as current problems in our understanding of calibrations and interlaboratory data comparisons

marine climate in the irish sea analysis of a 489 year marine master chronology derived from growth increments in the shell of the clam arctica islandica abstract we demonstrate here that the growth increment variability in the shell of the long lived bivalve mollusc arctica islandica can be interpreted as an indicator of marine environmental change in the climatically important north atlantic shelf seas multi centennial up to 489 year chronologies were constructed using five detrending techniques and their characteristics compared the strength of the common environmental signal expressed in the chronologies was found to be fully comparable with equivalent statistics for tree ring chronologies the negative exponential function using truncated increment width series from which the first thirty years have been removed was chosen as the optimal detrending technique chronology indices were compared with the central england temperature record and with seawater temperature records from stations close to the study site in the irish sea statistically significant correlations were found between the chronology indices and a mean air temperature for the 14 month period beginning in the january preceding the year of growth b mean seawater temperatures for february october in the year preceding the year of growth c late summer and autumn air temperatures and sea surface temperatures for the year of growth and d the timing of the autumn decline in sst changes through time in the correlations with air and seawater temperatures and changes towards a deeper water origin for the shells in the chronology were interpreted as an indication that shell growth may respond to stratification dynamics

effects of biogeochemical processes on magnesium isotope variations in a forested catchment in the vosges mountains france abstract this study investigates the potential of mg isotopes as tracers of biogeochemical processes in a small forested catchment located on sandstones extremely poor in mg bearing minerals the average 26 mg is 0 63 0 12 and 0 0 14 for local rainwater and bedrock respectively from the c horizon to the upper eluvial e horizon soil 26 mg from 0 0 0 14 to 0 25 0 14 is close to the bedrock value while more than 70 of mg is lost suggesting a small isotopic shift during illite dissolution the surface soil horizon a h 26 mg is close to plant 26 mg and especially to the grass 26 mg value 0 49 the bulk 26 mg of trees and grass 0 32 and 0 41 respectively are higher than the average 26 mg values of the soil exchangeable fraction 0 92 to 0 42 and of rainwater 0 65 within plants roots are enriched in heavy isotopes whereas light isotopes are preferentially translocated and stored in the above ground parts in norway spruce the older needles forming the annual litterfall are isotopically lighter and strongly depleted in mg compared to more recent needles soil solution 26 mg shifts seasonally from low values lower than rainwater and close to litterfall during a high rainfall period in spring to higher values close to soil 26 mg in dryer periods of winter or summer at the watershed scale streamwater 26 mg varies between 0 85 0 14 and 0 08 0 14 and 26 mg values decrease linearly with discharge the high streamwater 26 mg at low flow close to bedrock 26 mg most likely reflects dissolution processes in the deep saprolite in relation to the very long water residence time conversely we suggest that low stream level 26 mg values are at least partly related to the contribution of surface flows from wet areas using a simple mass and isotopic balance approach we compute that mineral dissolution rates in the soil 0 35 kg mg ha 1 year 1 presently compensate for mg losses from the soil

near equilibrium 13 c 18 o bonding during inorganic calcite precipitation under chemo stat conditions we report results of 13 c 12 c 18 o 16 o and 13 c 18 o clumped isotope analyses from a series of calcite precipitation experiments from aqueous solutions under laboratory conditions chemo stat precipitation experiments were performed to synthetically form calcite from aqueous solution onto 43 ca labeled calcite seed crystals formation rate was controlled during the experiments to investigate the effect of precipitation rate and temperature on 13 c 18 o bonding in calcite where rates ranged from 10 6 88 to 10 8 20 mol m 2 s 1 at three temperatures 10 20 and 30 c no relation was observed between precipitation rate and 13 c 18 o bonding proportion over the range of precipitation rates used the relation between 47 and temperature produced was comparable to calibration studies which report a relatively high sensitivity of 13 c 18 o bonding to temperature over the range investigated comparing solution conditions across multiple experimental data sets indicates an inverse relation between saturation state and 13 c 18 o bonding where high super saturation conditions are likely to be furthest from equilibrium 13 c 18 o partitioning carbon fractionation between calcite and hco 3 aq was found to be a temperature independent value of 1 6 the temperature dependent calcite water 18 o 16 o fractionation relation determined in this study is slightly different larger calcite h 2o value than those measured in several previous investigations significantly we observe a dependence of the 18o 16o isotope fractionation factor on growth rate taken together these findings suggest carbonate growth in our experiments approached equilibrium more closely than previous experiments of this type yet did not achieve full o isotope equilibrium

oxygen and carbon stable isotopes of modern land snail shells as environmental indicators from a low latitude oceanic island abstract land snails provide a unique opportunity to study terrestrial paleoenvironments because their shells which are generally highly abundant and well preserved in the fossil record contain a temporal record of environmental change in the form of isotope codes to evaluate the utility of this approach for a low latitude oceanic setting 207 modern shells of 18 species of land snail were analyzed for their oxygen and carbon isotope composition along a north and south facing altitudinal gradient 10 2160 m a s l in tenerife island 28 n of the canary archipelago shells collected at each locality showed a relatively large range in isotope composition which was greater along the south facing transect drier and hotter suggesting that the variance in shell isotope values may be related to water stress although pooled isotope values did not generally show strong relationships with environmental variables i e altitude temperature and precipitation mean isotope values were strongly associated with some climatic factors when grouped by site the mean 18o value of the shell 18oshell by site displayed a negative correlation with elevation which is consistent with the positive relationship observed between temperature and the 18o value of rain 18orain calculated 18o values of the snail body water 18obody derived from observed temperatures and 18oshell values using the equation of grossman and ku grossman e l and ku t l 1986 oxygen and carbon isotope fractionation in biogenic aragonite chem geol isotope geosci sec 59 59 74 displayed a trend with respect to altitude that was similar to measured and hypothetical 18o values for local rain water the calculated 18obody values from the shell declined 0 17 vsmow per 100 m which is consistent with the altitude effect observed for tropical rains in western africa and it correlated negatively with rainfall amount accordingly lower 18oshell values indicate lower temperatures lower 18orain values and possibly higher rainfall totals a positive correlation between the mean 13c values of shells 13cshell and plants by site suggests that shells potentially record information about the surrounding vegetation the 13cshell values varied between 15 7 and 0 6 vpdb indicating that snails consumed c3 and c4 cam plants where more negative 13cshell values probably reflects the preferential consumption of c3 plants which are favored under wetter conditions individuals with more positive 13cshell values consumed a larger percentage of c4 plants other potential factors such as carbonate ingestion or atmospheric co2 contribution were unlikely that were more common at lower elevations of the hotter and drier south facing transect the relatively wide range of shell isotope values within a single site requires the analysis of numerous shells for meaningful paleoclimatic studies although small differences were observed in isotope composition among snail species collected at a single sampling site they were not significant suggesting that isotope signatures extracted from multi taxa snail data sets may be used to infer environmental conditions over a broad range of habitats

temperature dependence of oxygen and clumped isotope fractionation in carbonates a study of travertines and tufas in the 6 95 c temperature range conventional carbonate water oxygen isotope thermometry and the more recently developed clumped isotope thermometer have been widely used for the reconstruction of paleotemperatures from a variety of carbonate materials in spite of a large number of studies however there are still large uncertainties in both 18o and 47 based temperature calibrations for this reason there is a need to better understand the controls on isotope fractionation especially on natural carbonates in this study we analyzed oxygen carbon and clumped isotopes of a unique set of modern calcitic and aragonitic travertines tufa and cave deposits from natural springs and wells together these samples cover a temperature range from 6 to 95 c travertine samples were collected close to the vents of the springs and from pools and tufa samples were collected from karstic creeks and a cave the majority of our vent and pool travertines and tufa samples show a carbonate water oxygen isotope fractionation comparable to the one of tremaine et al 2011 with some samples showing higher fractionations no significant difference between the calcite water and aragonite water oxygen isotope fractionation could be observed the 47 data from the travertines show a strong relationship with temperature and define the regression 47 0 044 0 005 106 t2 0 205 0 047 the ph of the parent solution mineralogy and precipitation rate do not appear to significantly affect the 47 signature of carbonates compared to the temperature effect and the analytical error the tufa samples and three biogenic calcites show an excellent fit with the travertine calibration indicating that this regression can be used for other carbonates as well this work extends the calibration range of the clumped isotope thermometer to travertine and tufa deposits in the temperature range from 6 c to 95 c

carbon and oxygen isotope composition of shell carbonate of desert land snails abstract variation in 13 c 12 c and 18 o 16 o ratios in the shell carbonate of several species of land snails was studied along a climatic gradient in semi arid to arid areas in the southern levant 13 c was found to be enriched in snails from communities having plants with a c 4 photosynthetic pathway depleted 13 c values were found in areas with high mean annual rainfall apparently due to higher input of metabolic co 2 as a result of greater snail activity shell carbonate 18 o values show a weak relation to the 18 o values of rainwater the shell 18 o values are enriched by 2 8 relative to isotopic equilibrium with environmental waters enrichment is suggested to result from metabolic effects on body water with lower activity producing greater enrichment but evaporation could also be a factor consistent differences in both 13 c and 18 o were found among species and may relate to the time when shell deposition occurs as with most paleoenvironmental indicators the application of shell isotopes is complicated by the multiplicity of controls of isotopic composition

calibration of the carbonate clumped isotope paleothermometer for otoliths paleothermometry is an essential tool for understanding past changes in climate the carbonate clumped isotope thermometer is a temperature proxy related to ordering of 13 c and 18 o in the carbonate lattice based on measurements of 13 c 18 o 16 o in co 2 produced by acid digestion of carbonate this thermometer has been previously calibrated for inorganic calcite and aragonitic corals ghosh p adkins j affek h balta b guo w f schauble e a schrag d and eiler j m 2006 c 13 o 18 bonds in carbonate minerals a new kind of paleothermometer geochim cosmochim acta70 6 1439 1456 here we determine the relationship between growth temperatures of aragonitic fish otoliths and abundances of 13 c 18 o 16 o produced by acid digestion of those otoliths our calibration is based on analyses of otoliths from six species from four genera of modern fish sampled from a latitudinal transect of the atlantic ocean between 54 s and 65 n plus one species from the tropical western pacific the temperatures at which fish otoliths precipitated were estimated by the mean temperature in the waters in which they lived averaged over their estimated lifetimes estimated growth temperatures of our samples vary between 2 and 25 c our results show that the abundance of 13 c 18 o 16 o in co 2 produced by acid digestion of fish otolith aragonite is a function of growth temperature following the relationship 47 0 0568x10 6 t 2 where 47 is the enrichment in per mil of 13 c 18 o 16 o in co 2 relative to the amount expected for a stochastic random distribution of isotopes among all co 2 isotopologues and t is the temperature in kelvin this relationship closely approaches that previously documented for inorganic calcite and aragonitic coral ghosh et al 2006

equilibrated clumped isotope signatures of land snail shells observed from laboratory culturing experiments and its environmental implications abstract this study reports on the clumped isotope values 47 of land snail shells precipitated at known temperatures ranging from 20 c to 30 c our observed shell 47 values fall into the uncertainties of published 47 t calibration line e g kelson et al 2017 indicating the shell aragonite of land snails is precipitated at clumped isotopic equilibrium without an obvious 47 vital effect the 47 data are neither related to the various bulk isotopic input sources both for 13c and 18o which result from differences in the supplied food and water nor are they related to the ingested carbonate composition or snail growth rate furthermore we preliminarily applied the 47 t calibration kelson et al 2017 to calculate the mean growth temperatures of the parent snails results suggest that the clumped isotope values for land snail shells can be regarded as a useful tool to reconstruct the mean seasonal temperature of snail activity when the environmental parameters are optimum future studies should focus on the applicability of this relationship to snails in natural environments where the self preservation or acclimatization mechanisms are more complex

unexpected calcium sources in deep soil layers in low fertility forest soils identified by strontium isotopes lorraine plateau eastern france forest ecosystems are often found on acid soils where calcium availability depends on two main inputs atmospheric deposition and the weathering of soil minerals and on the biological cycling of nutrients in the context of global change decreasing atmospheric inputs increasing biomass exportation climate change it is important to determine calcium sources to the ecosystem and tree nutrition to better understand how forest ecosystems will respond to these changes over time the aim of this study was to study and compare ca pools and cycling in two mature forest ecosystems clermont en argonne and azerailles developed on two contrasting polycyclic soils lorraine plateau eastern france and identify the ca sources contributing to ecosystem functioning at both sites soil ca pools were measured atmospheric deposition of ca was monitored from bulk precipitation and throughfall chemistry ca biological cycling was assessed by measuring litterfall and by a litter decomposition experiment strontium 87sr 86sr isotope data in the soil profile fine roots exchangeable pool bulk soil was used to estimate the distribution of sr and ca uptake in the soil profile and the relative contribution of mineral weathering in the soil layers to total ecosystems inputs despite important differences in ca availability in the topsoil between both sites tree growth and nutrition indicators showed no significant difference this discrepancy is not explained by the biological cycling of ca but may be partly explained by higher ca deposition at the ca poorer site strontium isotope data enabled to show important differences of ca sources for tree uptake at the ca poorer site deep soil layers 105 cm potentially represent from 32 to 100 of total sr uptake at the ca richer site results suggest that uptake is more evenly distributed in the soil profile sr isotope data coupled with a modeling approach suggest that two different mineral sources exist in the soil profile a radiogenic sr source in the topsoil 87sr 86sr 0 717 and a less radiogenic source in depth 87sr 86sr 0 717 the deep mineral source may represent from 40 to 86 of total sr inputs at the poorer site and from 25 to 86 at the richer site the origin of this deep strontium source is unclear but soil mineralogy suggests an allochthonous origin we hypothesize that this deep source originates from capillary rise of the groundwater aquifer this nutrient input to forest ecosystems is not commonly taken into account but may strongly participate in maintaining the chemical fertility of soils over time

terrestrial mollusk records from chinese loess sequences and changes in the east asian monsoonal environment abstract the terrestrial mollusk fossils found in chinese loess strata have been studied for over one hundred years however the greatest progress in these studies has been made only in the last two decades in this paper we review the advancements advantages and limitations of terrestrial mollusk studies in chinese loess deposits improvements in research methods and approaches have allowed the extraction of more detailed paleoenvironmental and paleoclimatic information from mollusk assemblages the broadened research scope and content have yielded many new findings and results the mollusk record has thus become one of the most important proxies in the paleoenvironmental and paleoclimatic reconstruction of loess paleosol sequences in china the greatest progress in the studies of terrestrial mollusks in chinese loess sequences can be summarized as follows 1 modern mollusk assemblages can be classified into four ecotypes based on their temperature and humidity requirements including eurytopic semi aridiphilous and sub humidiphilous cold aridiphilous and thermo humidiphilous types 2 quaternary mollusk assemblages can be modified into the following three ecological types glacial loess interglacial paleosol and interstadial weakly developed paleosol assemblages 3 mollusk records successfully reveal long term climatic and environmental changes reflective of the history of east asian monsoonal variations since the late cenozoic and the succession of mollusk species also indicate short term environmental changes such as millennial climate variability during last glacial maximum and unstable climatic fluctuations during glacial and interglacial periods and 4 more recently new analytical approaches have offered increased research potential in areas such as paleotemperature reconstruction using the isotopic compositions of modern and fossil mollusk shells combined with higher accuracy 14 c dating of quaternary loess deposits which will greatly improve future loess paleoenvironmental research

evidence for mass dependent isotopic fractionation of strontium in a glaciated granitic watershed abstract the stable isotope composition of strontium expressed as 88 86sr may provide important constraints on the global exogenic strontium cycle here we present 88 86sr values and 87sr 86sr ratios for granitoid rocks a 150 yr soil chronosequence formed from these rocks surface waters and plants in a small glaciated watershed in the central swiss alps incipient chemical weathering in this young system whether of inorganic or biological origin has no resolvable effect on the 87sr 86sr ratios and 88 86sr values of bulk soils which remain indistinguishable from bedrock in terms of sr isotopic composition although due in part to the chemical heterogeneity of the forefield the lack of a resolvable difference between soil and bedrock isotopic composition indicates that these soils have thus far witnessed minimal net loss of sr a low degree of chemical weathering is also implied by bulk soil chemistry the isotopic composition of sr in streamwater is more radiogenic than median soil reflecting the preferential weathering of biotite in the catchment streamwater 88 86sr values however are indistinguishable from bulk soil 88 86sr values implying that no resolvable fractionation of sr isotopes takes place during release to the weathering flux in the damma forefield analyses of plant tissue reveal that plants rhododendron and vaccinium preferentially assimilate the lighter isotopes of sr such that their 88 86sr values are significantly lower than those of the soils in which they grow additionally 88 86sr values of foliar and floral tissues are lower than those of roots contrary to observations for ca for which sr is often used as an analogue in weathering studies we suggest that processes that discriminate against sr in favour of ca due to the different nutritional requirement of plants for these two elements are responsible for the observed contrast

glacial interglacial temperature variations in soreq cave speleothems as recorded by clumped isotope thermometry clumped isotope thermometry is based on analyzing mass 47 in co2 extracted from carbonates and uses the tracer mass 47 anomaly 47 47 is defined as the deviation of r47 from that expected for a random distribution of isotopologues and reflects a temperature dependent preference of 13c and 18o to create a bond with each other in co2 or in the carbonate lattice being an internal characteristic of the carbonate mineral it is independent of the isotopic composition of the water in which equilibrium precipitation of the carbonate occurs and can therefore be used to independently determine carbonate growth temperatures this work provides a first examination of the applicability of clumped isotopes thermometry to reconstructing the growth temperatures of speleothems by examining the glacial interglacial variations of the 47 values of speleothem carbonates from soreq cave israel the results indicate that the last glacial maximum temperatures were 6 7 c colder than modern day temperature and a sample at 56 ky bp was 3 c colder than the modern early holocene temperatures were slightly above modern day and late holocene temperatures were slightly below modern day these temperature variations are similar to those previously estimated for eastern mediterranean sea surface water cave water was 18o depleted in the holocene compared to modern day by 0 6 1 and 1 1 more enriched in the last glacial maximum comparison of these cave water 18o values with fluid inclusion d values indicated a late holocene d excess value within the range of modern rainfall implying not vert similar45 relative humidity last glacial maximum and early holocene d excess values were significantly lower suggesting relative humidity of not vert similar60 and not vert similar70 respectively the temperatures reported in this study were empirically corrected for a non equilibrium artifact observed in a modern speleothem the similarity of the temperature variations obtained here to other independent records in the region suggests that the 47 temperature calibration slope observed in inorganic synthetic calcite and marine organisms may also be applied in speleothems but the offset observed in modern temperature suggests that the intercept is different so that a separate calibration is needed for accurate absolute temperature reconstruction using speleothem clumped isotopes similar examination of additional caves would be necessary to determine whether such empirical correction can be generally applied or is it a unique characteristic of soreq cave

calcium isotopes in the global biogeochemical ca cycle implications for development of a ca isotope proxy abstract at the earth s surface calcium ca is a critical element at a variety of scales it is soluble in natural waters a biological nutrient and a major constituent of the dominant mineral sink for carbon in the ocean caco3 there is a 4 variation in the ca isotopic composition 44ca 40ca expressed as 44ca of various ca reservoirs on earth suggesting ca isotopes as a promising tracer of ca cycling in both the present and the past fifteen years of high precision ca isotope measurements has revealed much about the behavior of ca isotopes in the earth surface environment but there remain fundamental questions concerning how ca isotopes are used to elucidate the marine and terrestrial ca cycles the current work presents a data compilation of over 70 published ca isotope studies totaling over 2600 measurements presented on a common delta scale that includes data on rivers and groundwater dust soils and soil pore fluids vegetation rainwater silicate minerals rocks and authigenic marine minerals carbonates sulfates and phosphates both modern and ancient the data compilation suggests that 1 there is a significant difference between carbonate 0 60 and silicate 44ca 0 94 2 riverine 44ca 0 88 does not simply reflect the compiled carbonate 44ca and 3 terrestrial vegetation exhibits the largest range of ca isotopic compositions 3 5 in the terrestrial setting we discuss these observations in the context of the global ca cycle exploring the extent to which seawater 44ca variability is feasible and how we can achieve accurate reconstructions of seawater 44ca over geologic time scales the current study presents simple mass balance models that quantify the leverage of inputs to change the ca isotopic composition of the ocean as this directly impacts the manner in which ca isotopes are interpreted although ca fractionates isotopically in the modern system during continental cycling the 44ca range of riverine inputs to the ocean is considerably smaller than the variability observed in putative seawater proxies such as nannofossil ooze and marine barite in the terrestrial realm plants exhibit a wide 44ca range and there is evidence that ca fluxes via biomass degradation are significant at the catchment scale we therefore assess the ability of the continental biosphere to influence riverine and consequently seawater 44ca a steady state biosphere has little leverage to alter riverine 44ca except in cases where the 44ca of the recycling flux is isotopically distinct from the 44ca of the uptake flux a non steady state biosphere can substantially impact both soil and riverine 44ca driving exchangeable ca either heavier or lighter depending on the magnitude of the recycling flux relative to the uptake flux based on estimates of the size of the global biosphere 1 5 1015 mol ca we suggest a decaying biosphere has the potential to impact riverine 44ca by tenths of a permil over time scales in the marine realm we evaluate the effect of a variable fractionation factor accompanying global removal of ca from the ocean on seawater 44ca and suggest methods by which such a mechanism can be recognized in the rock record experimental data suggest that there is considerable leverage