stable isotope composition of late pleistocene holocene eobania vermiculata muller 1774 pulmonata stylommatophora shells from the central mediterranean basin data from grotta d oriente favignana sicily abstract this paper presents stable isotopic results oxygen and carbon from both modern and late pleistocene holocene shells of the land snail eobania vermiculata muller 1774 from favignana island sicily it aims to contribute to the understanding of climate and vegetation history of this region during formation of upper palaeolithic mesolithic and meso neolithic deposits of grotta d oriente ort results from both an evaporative model fbm and an empirical regional isotopic model i e linear relation between oxygen isotopic composition of shells 18 os and those of local precipitation 18 op indicate that the 18 os values of modern specimens are mainly controlled by local temperature relative humidity and 18 op at the time of snail activity data also suggest that the modern snails are nocturnally active almost all year round in the study area the carbon isotopic compositions of shells 13 cs of the same specimens indicate a diet prevalently or exclusively composed of c3 vegetation the 18 os values of late pleistocene specimens suggest that climate conditions at 14 2 ka cal bp were similar to the present day in agreement with additional 18 os records from southern italy by contrast early middle holocene shells are notably 18 o depleted and suggest wetter conditions possibly combined with a decrease in isotopic composition of precipitation source compared to the present day when compared with regional palaeoclimatic records a large scale isotopic response to millennial scale changes in atmospheric and hydrological conditions e g enhanced rainfall in the central eastern mediterranean is observed during the early middle holocene the 13 cs of late pleistocene and holocene specimens are consistently higher than those of modern ones for the late pleistocene this could be reasonably explained in terms of water stressed vegetation on the other hand this seems to be less valid for holocene counterparts when the climate was wetter probably 13 cs values result from the combination of distinct competing factors involving atmospheric co 2 concentration seasonal water budget vegetation type cover and other carbon sources results reveal coherent relationships between regional 18 os and 13 cs demonstrating that late pleistocene holocene land snail shell remains from archaeological sites may provide useful snapshots of past seasonal climate conditions

holocene hydrological changes in south western mediterranean as recorded by lake level fluctuations at lago preola a coastal lake in southern sicily italy abstract this paper presents a high resolution lake level record for the holocene at lago preola sicily southern italy based on a specific sedimentological approach with a chronology derived from ams radiocarbon dates it gives evidence of three major successive palaeohydrological periods with 1 a pronounced dryness during the early holocene until ca 10300 cal bp 2 a highstand from ca 10300 to 4500 cal bp and 3 a marked lowstand from 4500 cal bp to present large amplitude lake level fluctuations characterise two transition phases at ca 10300 9000 and 6400 4500 cal bp period 2 was interrupted between 8300 and 7000 cal bp by a dry phase that was punctuated to ca 7300 cal bp by the deposition of a tephra from neighbouring pantelleria island comparisons of the preola record with other palaeohydrological records along north south and west east transects in the mediterranean show contrasting patterns of hydrological changes north south of around 40 n latitude the records highlight a mid holocene period characterised by lake level minima maxima humid mid holocene conditions over the mediterranean south of 40 n were probably linked to a strong weakening of the hadley cell circulation and of monsoon winds we suggest that the maximum of humidity in the mediterranean during the mid holocene was characterised by humid winters to the north of 40 n and humid summers to the south on a multi centennial scale the high resolution palaeohydrological reconstructions in the central mediterranean area reveal a strong climate reversal around 4500 4000 cal bp with contrasting changes in the hydrological cycle in addition to seasonal and inter hemispherical changes related to orbital forcing this major oscillation might be related to non linear responses of the climatic system to the gradual decrease in summer insolation at northern latitudes another major climate oscillation around 7500 7000 cal bp may have resulted from the combined effects of 1 a strong rate of change in insolation and 2 variations in solar activity finally comparisons of the preola lake level record with sicilian pollen records suggest a strong influence of moisture availability on vegetation development in sicily very dry early holocene conditions probably prevented the expansion of coastal evergreen forests while decreasing moisture availability since the onset of the late holocene may have exacerbated effects of intensive land use

holocene trends in 18o in land snail shells from the negev desert and their implications for changes in rainfall source areas abstract the 18o value of the carbonate of land snail shells is related to the 18o content of precipitation which in turn relates to the source region and trajectory of the rain bearing air masses analyses of 18o of the shell carbonate of 76 radiocarbon dated holocene samples of the land snail trochoidea seetzeni from the northern negev desert in southern israel were carried out and the results were compared to modern snails from the same region early holocene 18o values are similar to modern but during the period centered around 6500 6000 yr b p a depletion of some 2 below modern is observed a change in the atmospheric circulation pattern for this period is thus indicated most likely an increase in the frequency of storm systems reaching the region from north eastern africa by 3500 yr b p 18o values had reached modern levels and indicate a stable pattern of atmospheric circulation since that time

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

geochemistry of rainfall at stromboli volcano aeolian islands isotopic composition and plume rain interaction the chemical and isotopic compositions of the precipitation at stromboli island italy were investigated between october 2003 and october 2005 we employed a rain gauge network designed to cover the range in exposures and elevations of the volcanic edifice the hydrogen and oxygen isotopic ratios vary greatly on a seasonal basis and correlate with air temperature deuterium excess values show a positive correlation with altitude no direct contribution of volcanogenic h or o is evident in the isotopic composition of the rainwater the chemical composition of the rainwater is principally controlled by the sea aerosol contribution at the coastal sites whereas it is significantly influenced by volcanic activity near the summit vents interaction with volcanic acid gases is indicated by the ph which is usually 1 2 units lower near the craters than at the coastal sites the s cl cl f and s f molar ratios in rainwater 1 5 km from the craters are consistent with those measured in the volcanic plume using other methods diffusive tubes and fourier transform infrared spectroscopy rising of undegassed magmas changes these molar ratios because of the differential degassing of sulphur chlorine and fluorine from the magma we therefore propose that the chemical composition of precipitation within 1 5 km of the craters provides additional information that is useful for monitoring volcanic activity at stromboli island moreover this paper presents estimates of the fluxes of f cl s na k ca and mg to the soil that could be useful for geochemical studies on groundwater

late glacial to holocene transition in northern spain deduced from land snail shelly accumulations abstract shells of the helicid cepaea nemoralis were studied using taphonomic isotopic and morphometric measurements to estimate late glacial holocene 12 1 6 3 cal ka bp environmental conditions in northern spain higher taphonomic alteration among holocene shells suggests lower sedimentation rates or higher shell destruction rates than during glacial conditions shells preserved the aragonitic composition despite differing degree of skeleton damage shell 13 c values were 10 3 1 1 8 2 2 3 and 7 3 1 6 for modern holocene and late glacial individuals respectively higher 13 c values during the late glacial and some holocene periods imply higher water stress of c 3 plants and or higher limestone contribution than today intrashell 13 c values were higher during juvenile stages suggesting higher limestone ingestion to promote shell growth shell 18 o values were 1 1 0 7 0 9 0 8 and 0 1 0 7 for modern holocene and late glacial specimens respectively a snail flux balance model suggests that during 12 1 10 9 cal ka bp conditions were drier and became wetter at 8 4 6 3 cal ka bp and today intrashell 18 o profiles reveal that glacial individuals experienced more extreme seasonality than interglacial shells despite possible larger hibernation periods shell size correlated positively with 18 o values suggesting that growth rates and ultimate adult size of c nemoralis may respond to climate fluctuation in northern spain

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

paleoclimatic implications of the spatial patterns of modern and lgm european land snail shell δ18o abstract the oxygen isotopic composition of land snail shells may provide insight into the source region and trajectory of precipitation last glacial maximum lgm gastropod shells were sampled from loess from belgium to serbia and modern land snail shells both record 18 o values between 0 and 5 there are significant differences in mean fossil shell 18 o between sites but not among genera at a single location therefore we group 18 o values from different genera together to map the spatial distribution of 18 o in shell carbonate shell 18 o values reflect the spatial variation in the isotopic composition of precipitation and incorporate the snails preferential sampling of precipitation during the warm season modern shell 18 o decreases in europe along a n s gradient from the north sea inland toward the alps modern observed data of isotopes in precipitation gnip demonstrate a similar trend for low altitude sites lgm shell 18 o data show a different gradient with 18 o declining toward the ene implying a mid atlantic source due to increased sea ice and a possible southern displacement of the westerly jet stream balkan lgm samples show the influence of a mediterranean source with 18 o values decreasing northward

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

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

holocene paleoenvironment 7200 4000 cal bp of the los castillejos archaeological site se spain inferred from the stable isotopes of land snail shells abstract neolithic copper age and modern land snail shells from the los castillejos archeological site 37 20 n se iberian peninsula were analyzed for 13 c 12 c and 18 o 16 o ratios to estimate the paleoenvironmental conditions during shell deposition modern and ancient 13 c values ranged from 9 2 to 7 7 and from 13 6 to 5 7 respectively and they differed among taxa 13 c values were similar for neolithic 13 c 8 1 2 3 copper age 13 c 8 4 0 6 and modern 13 c 8 4 0 5 herbivorous cernuella specimens alternatively fossil shells of the herbivorous ferussacia folliculum 13 c 9 9 1 2 and the omnivorous rumina decollata 13 c 11 1 2 showed substantially lower 13 c values than modern specimens which may suggest lower water stress during the early to mid holocene than today the 18 o values from modern specimens ranged from 1 1 to 0 6 while the 18 o values from fossil specimens ranged from 6 7 to 0 and they differed among species cernuella exhibited shell 18 o values that increased from the neolithic 18 o 2 3 1 8 and copper age 18 o 1 7 0 6 to the present 18 o 0 3 0 5 the 18 o values of fossil shells of f folliculum 18 o 3 7 1 0 and r decollata 18 o 4 0 1 6 were also lower than modern shells calculations of a published snail flux balance mixing model for 18 o values indicate that early to mid holocene shells precipitated during times when relative humidity was greater than today the se iberian peninsula was noticeably wetter 7200 cal bp and experienced drier conditions thereafter the results are consistent with other regional paleoclimatic proxies and reinforce the potential use of land snail shells as paleoenvironmental archives

reconstruction of late pleistocene climate in the valsequillo basin central mexico through isotopic analysis of terrestrial and freshwater snails we aim to reconstruct the climatic and environmental conditions in the valsequillo basin during the deposition of the valsequillo gravels between c 40 000 and 8000 years ago when large mega fauna and potentially humans occupied the basin fossil freshwater fossaria sp and sphaeriidae family and terrestrial polygyra couloni holospira sp and cerionidae family snail shells from sections within the barranca caulapan were collected for oxygen and carbon stable isotope analysis oxygen and carbon isotopes in terrestrial and freshwater snail shells relate to local climatic parameters and environmental conditions prevailing during the lifetime of the snail whole shell isotope analysis showed that c 35 000 years ago climate in the valsequillo basin was similar to the present day between c 35 000 and 20 000 bp conditions became increasingly dry after which conditions became wetter again although this record is truncated intra shell isotopic analyses show that the amount of precipitation varied seasonally during the late pleistocene if people did reach this part of the americas in the late pleistocene they would have experienced changing long term and seasonal climatic conditions and would have had to adapt their life strategies accordingly

holocene snail shell isotopic record of millennial scale hydrological conditions in western mediterranean data from bauma del serrat del pont ne iberian peninsula land snail shells are a common component in mediterranean holocene archaeological deposits providing the opportunity to explore their potential as source of information concerning human behaviour and palaeoclimatic conditions many well preserved shells of the caenogastropod pomatias elegans were recovered along the holocene succession of bauma del serrat del pont bsp in the iberian peninsula their oxygen 18os and carbon 13cs isotopic compositions were analysed and compared with that of modern shells of the same species collected in two distinct areas near the archaeological site modern shells from site a shady and b sunny show distinctly different oxygen isotopic ratios possibly due to the effect of microenvironmental conditions e g temperature and relative humidity carbon isotopes by contrast reveal similar values isotope mass balance suggests a prevalent contribution of vegetation 70 integrated with foreign carbonates 30 to 13cs of modern snails early late holocene shells 9 2 5 cal ka bp have lower 18os compared with modern counterparts which is consistent with prevailing wetter conditions compared with present day the 13cs reveals distinct hydrological regimes wet and dry conditions from early to late holocene respectively in general shell isotopic records from western and central mediterranean regions suggest wetter conditions during the middle holocene with a possible reduction in humidity from 4 cal ka bp the 18os indicates a possible latitudinal difference in hydrological balance between mediterranean and atlantic europe as inferred by previous studies of regional palaeoclimatic records carbon isotopes by contrast do not provide a clear climatic picture probably due to the effect of distinct vegetation structure and composition comparisons with other environmental archives reinforce the concept of regional shell oxygen isotopic response to millennial scale changes in hydrological condition over the western and central mediterranean during the late quaternary

enhanced rainfall in the western mediterranean during deposition of sapropel s1 stalagmite evidence from corchia cave central italy a stable isotope record from a stalagmite collected from antro del corchia cave apuan alps central italy supported by 17 uranium series ages indicates enhanced regional rainfall between ca 8 9 and 7 3 kyr cal bp at the time of sapropel s1 deposition within this phase the highest rainfall occurred between 7 9 and 7 4 kyr cal bp comparison with different marine and lake records and in particular with the soreq cave record israel suggests substantial in phase occurrence of enhanced rainfall between the western and eastern mediterranean basins there is no convincing evidence for major climatic change at the time of the 8 2 kyr event

early middle holocene land snail shell stable isotope record from grotta di latronico 3 southern italy this paper compares stable isotope d 18 o and d 13 c records of early middle holocene land snail shells from the archaeological deposits of grotta di latronico 3 ltr3 southern italy with modern shell isotopic data no substantial interspecific variability was observed in shell d 18 o d 18 os of modern specimens pomatias elegans cornu aspersum eobania vermiculata helix ligata and marmorana fuscolabiata in contrast interspecific shell d 13 c d 13 cs variability was significant probably due to different feeding behaviour among species the d 18 os values of living land snails suggest that species hibernate for a long period during colder months so that the signal of 18 o depleted winter rainfall in their d 18 os is lost this suggests that d 18 os and d 13 cs values of pomatias elegans from this archaeological succession provide valuable clues for seasonal spring autumn climatic con ditions during the early middle holocene the d 18 os values of fossil specimens are significantly lower than in modern shells and in agreement with other palaeoclimatic records suggesting a substantial increase of precipitation and or persistent changes in air mass source trajectories over this region between ca 8 8 cal ka bp and 6 2 6 7 ka ago the d 13 cs trend suggests a transition from a slightly 13 c enriched to a 13 c depleted diet between early and middle holocene compared to present conditions we postulate that this d 13 cs trend might reflect changes in the c3 vegetation community potentially combined with other environmental factors such as regional moisture increase and the progressive decrease of atmospheric co2 concentration copyright 2010 john wiley sons ltd

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

stable isotope record in mollusca and pedogenic carbonate from late pliocene soils of central italy abstract the late pliocene younger than 2 5 ma alluvial fan succession of toppetti quarry near todi umbria central italy includes many palaeosols pedogenic carbonate concretions and mollusc remains were separated from 73 palaeosols collected along 150 m of exposure and analysed for their oxygen and carbon stable isotope content 13c and 18o of the pedogenic carbonate and land snail shells suggest that no dramatic change in local climate took place values of the pedogenic carbonates are similar to other data reported for the mediterranean region 18o data suggest a mean annual temperature and or 18o similar to modern climatic conditions carbon isotope data from both land snails and pedogenic carbonate are consistent with a prevailing type c3 vegetation a mixture of forest and c3 grassland sustained by a mean annual precipitation between 300 and 1000 mm mainly in the cool periods of the year seems to be the most likely scenario the limited variation shown by the isotope composition of the biogenic and inorganically precipitated carbonate indicates that the environmental variations are referable mainly to change of humidity rather than temperature

oxygen and carbon isotopic composition of modern terrestrial gastropod shells from lipari island aeolian archipelago sicily abstract oxygen 18os and stable carbon 13cs isotopic compositions of modern terrestrial gastropod shells from lipari island in the aeolian archipelago sicily have been analysed and compared with local meteoric water 18o 18op and vegetation 13c 13cv respectively results reveal that the 18os 18op relationship over the study area differs from those obtained on continental europe and italian shells implying that even at the scale of the mediterranean basin different relationships may co exist these differences have been interpreted as the increasing influence of mediterranean vapour water on tyrrhenian coasts at relatively low altitude up to 600 m asl which compensates for the effect of the 18op and possibly of temperature on shell 18o the steady state flux balance model fbm in agreement with previous studies suggests that snails are active prevalently at night shell carbon isotope ratios reflect the 13cv as predicted by the metabolic model and represent a valuable tool for identifying c3 plants with very distinct isotopic signatures

the waterlogging of floating objects we consider the dynamical processes by which a dense porous object floating in a body of liquid becomes waterlogged and sinks we first generalize the classic model of capillary rise in a porous medium to present an analytically tractable model of the process which is valid for objects that are very shallow compared to their horizontal extent we find an analytical expression for the time taken for the object to sink under this approximation we use a series of boundary integral simulations to show that decreasing the horizontal extent of the object decreases the time taken to sink we find that the results of these numerical simulations are in good quantitative agreement with a series of laboratory experiments finally we discuss the implications of our work for pumice fragments often found floating in open water after a volcanic eruption occasionally even supporting plant animal and human remains

implications for late holocene climate from stable carbon and oxygen isotopic variability in soil and land snail shells from archaeological site 41km69 in texas usa abstract well preserved fossil land snail shell collected in a 115 cm soil profile from archaeological site 41km69 in texas usa minimally span the past 2200 years and provide an opportunity to explore the paleoclimate implications of isotopic variability in shell carbonates bulk soil carbonates and soil organic matter carbon isotopic compositions 13 c values of modern and archaeological adult snail shell carbonates suggest significant 60 dietary input of c 3 plants during all periods oxygen isotopic compositions of shells suggest that the isotopic composition of environmental water available at the time of shell growth has changed little over the period of the profile a linearly decreasing trend in 13 c of soil organic matter from 22 8 at the bottom of the profile 115 cm below surface to 25 6 for modern surface samples indicate an overall 20 increase in abundance of c 3 plants this implies a progressively wetter climate and less severe water stress conditions or decreasing summer rainfall that is in agreement with other studies on late holocene climate change in the southern great plains usa these results strongly suggest a stable climate that favored c 3 vegetation in this portion of texas during this period

stable carbon and oxygen isotopic variations in modern rabdotus land snail shells in the southern great plains usa and their relation to environment abstract variations of stable isotopic ratios of carbon 13c 12c and oxygen 18o 16o were investigated in modern shells of two species of rabdotus land snails r dealbatus and r alternatus in the southern great plains geographic variation in relation to climate and vegetation microgeographic variation variability among individuals and detailed records of seasonal variations within individual shells were studied stable carbon isotopic ratios in shell carbonate are primarily a function of the isotopic composition of the diet of the snails as represented by the isotopic composition of shell organic matter this in turn reflects the presence or absence of cam crassulacean acid metabolism or c4 plants vegetation density may have a small effect on the carbon isotope ratios microgeographic variation samples within 25 to 300 m is greater than that seen across different climatic regions and points to very local control of isotopic variations predominantly related to vegetation seasonal variations as assessed through serial analysis of individual shells up to 35 samples per shell may provide a means for distinguishing between isotopic influences of perennial cam vs annual c4 plants carbon isotopic variations in time series of shells from a site provide a means of reconstructing temporal changes in environment and climate oxygen isotopic values of shell carbonate are uniform across the region and also show no significant microgeographic variation the oxygen isotopic composition appears to be mainly a function of the rainwater isotopic composition with no direct influence of rainfall amount or evaporative effects the 18o values are only 2 enriched relative to estimated equilibrium with rainwater variability is low sd of 0 8 among sites so the isotopic composition of fossil rabdotus shells can provide a precise record of changes in the isotopic composition of rain over time

environmental significance of 13c 12c and 18o 16o ratios of modern land snail shells from the southern great plains of north america c 12 c and 18 o 16 o ratios of aragonite shells of modern land snails from the southern great plains of north america were measured for samples from twelve localities in a narrow east west corridor that extended from the flint hills in north central oklahoma to the foothills of the sangre de cristo mountains in northern new mexico usa across the study area shell y 18 o values pdb scale ranged from 4 1x to 1 2x while y 13 c values ranged from 13 2x to 0 0x y 18 o values of the shell aragonite were predicted with a published steady state evaporative flux balance model the predicted values differed with one exception by less than 1x from locality averages of measured y 18 o values this similarity suggests that relative humidity at the time of snail activity is an important control on the y 18 o values of the aragonite and emphasizes the seasonal nature of the climatic information preserved in the shells correlated y 13 c values of coexisting vallonia and gastrocopta suggest similar feeding habits and imply that these genera can provide information on variations in southern great plains plant ecology although there is considerable scatter multispecies transect average y 13 c values of the modern aragonite shells are related to variations in the type of photosynthesis i e c3 c 4 in the local plant communities the results of this study emphasize the desirability of obtaining isotope ratios representing averages of many shells in a locale to reduce possible biases associated with local variations among individuals species etc and thus better represent the bneighborhoodq scale temporal and or spatial environmental variations of interest in studies of modern and ancient systems d 2004 university of washington all rights reserved

isotopic composition of precipitation in italy a first overall map abstract composite monthly samples of atmospheric precipitation were collected over different periods of time ranging from one to seven years at 77 different locations throughout italy these samples were measured for their oxygen and hydrogen isotopic composition to obtain basic information for hydrological and meteorological studies in this area on the basis of the results obtained a first map of the isotopic composition of precipitations in italy has been drawn up the main features of this map are the following 1 no isotopic latitudinal gradient has been found along the tyrrhenian coast from sicily to the italian french border despite the considerable range of latitude 2 a minor latitudinal gradient is found in the southeasternmost section of the country apulia partially favored by the local morphology 3 a marked shadow effect of the apennines is apparent along the southern section of the po valley and along the central section of the adriatic coast 4 the contribution of water vapor from the northernmost section of the adriatic sea affects the eastern and central sections of the po plain 5 the shadow effect of the alps is considerably smaller than expected 6 the isotopic vertical gradients calculated in nine different areas and based on groups of two to five different stations vary but are essentially close to about 0 2 100 m 7 when mean monthly temperature values were available their relationship with the isotopic composition of precipitation was found to be on average very poor 8 the relationship between mean 18o and mean d calculated for the collection locations shows shifts of both the slope and the deuterium excess when compared to the global meteoric water line these shifts are different for northern central and southern italy 9 in a few cases anomalously low monthly values suggest the existence of pronounced amount effects

deciphering late quaternary land snail shell δ18o and δ13c from franchthi cave argolid greece this paper investigates the stable isotopic composition from late pleistocene holocene 13 to 10 5 cal ka bp shells of the land snail helix figulina from franchthi cave greece it explores the palaeoclimatic and palaeoenvironmental implications of the isotope palaeoecology of archaeological shells at the time of human occupation of the cave modern shells from around the cave were also analysed and their isotopic signatures compared with those of the archaeological shells the carbon isotope composition of modern shells depicts the consumption of c3 vegetation shell oxygen isotopic values are consistent with other mediterranean snail shells from coastal areas combining empirical linear regression and an evaporative model the 18os suggest that modern snails in the study area are active during periods of higher relative humidity and lower rainfall 18o probably at night late glacial and early holocene 18os show lower values compared to modern ones early holocene 18os values likely track enhanced moisture and isotopic changes in the precipitation source by contrast lower late glacial 18o could reflect lower temperatures and 18op compared to the present day shell carbon isotope values indicate the presence of c3 vegetation as main source of carbon to late glacial and early holocene snails