holocene climate optimum and last glacial maximum in the mediterranean the marine oxygen isotope record reconstructions with comprehensive estimates of confidence intervals are presented of changes in the w e stable oxygen isotope gradient in mediterranean surface waters between the holocene climate optimum and the present and between the last glacial maximum and the present rigorous statistical assessment is made of the significances of the mean geographic trends observed in these reconstructions firstly it is concluded that any reconstruction should strictly be based on values obtained by analyses of one single foraminiferal species throughout the basin as different species are found to respond with isotopic variations of different amplitudes to climatic hydrographic change this difference is tentatively related to differences between the habitats and seasons of growth of the various species secondly a significant increase of roughly a factor 3 is found in the mediterranean w e oxygen isotope gradient during the last glacial maximum relative to the present this difference is almost entirely due to increased glacial values in the levantine sea which are considered to be a result of a combination of increased evaporation rates and or somewhat cooler than anticipated surface water conditions thirdly an eastward increase of roughly half the present day magnitude is found for the w e oxygen isotope gradient during the holocene climate optimum values in the levantine sea appear to have undergone up to 0 3 more depletion than those elsewhere in the eastern mediterranean however no significant trends are found between the eastern and western parts of the levantine sea nor between values near the nile delta and those from elsewhere in the levantine sea the holocene climate optimum s eastward increase in the mediterranean oxygen isotope gradient although weaker than the present suggests that the mediterranean continued to function as a concentration basin albeit in a less vigorous way than today finally simple mixing arguments are used to argue that inferred oxygen isotope ratios of surface waters may not be used as an indication of conservative property e g salinity distribution on geological timescales but instead show amplitudes of response to climatic hydrographic changes that likely are 2 times larger than the corresponding amplitudes of response for truly conservative properties

aridification of central asia and uplift of the altai and hangay mountains mongolia stable isotope evidence central asia has become increasingly arid during the cenozoic though the mechanisms behind this aridification remain unresolved much attention has focused on the influence and uplift history of the tibetan plateau however the role of ranges linked to india asia convergence but well north of the plateau including the altai sayan and hangay in creating the arid climate of central asia is poorly understood today these ranges create a prominent rain shadow effectively separating the boreal forest to the north from the deserts of central asia to explore the role of these mountains in modifying climate since the late eocene we measured carbon and oxygen stable isotopes in paleosol carbonates from three basins along a 650 km long transect at the northern edge of the gobi desert in mongolia and in the lee of the altai and hangay mountains we combine these data with modern air parcel back trajectory modeling to understand regional moisture transport pathways at each basin in all basins 13c increases with the largest increase in western mongolia the first 13c increase occurs in central and southwestern mongolia in the oligocene 13c again increases from the upper miocene to the quaternary in western and southwestern mongolia we use a 1 d soil diffusion model to demonstrate that these 13c increases are linked to declines in soil respiration driven by dramatic increases in aridity using modern day empirical relations between mean annual precipitation and soil respiration we estimate that precipitation has likely more than halved over the neogene given the importance of the hangay and altai in steering moisture in mongolia we attribute these changes to differential surface uplift of the hangay and altai surface uplift in the hangay began by the early oligocene blocking siberian moisture and aridifying the northern gobi in contrast surface uplift of the altai began in the late miocene blocking moisture from reaching western mongolia thus the northern gobi became increasingly arid east to west since the late eocene likely driven by orographic development in the hangay during the oligocene and the altai in the late miocene through pliocene

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

oxygen isotope signatures from land snail helix melanostoma shells and body fluid proxies for reconstructing mediterranean and north african rainfall abstract in this paper we show that oxygen isotope ratios from the shell carbonate of the land snail helix melanostoma reflect local rainfall parameters stable oxygen isotopes were measured in the body fluid 18 o body and shells 18 o shell of live collected h melanostoma along a north south transect across the gebel akhdar in northeast libya 18 o body ranged between 8 1 and 13 0 whilst 18 o shell ranged between 1 0 and 2 8 to investigate the relationship between snail oxygen isotope composition and climate these measurements were correlated with ambient air temperature relative humidity rainfall amount and the 18 o composition of rainwater 18 o rain strong and significant correlations were found between 18 o shell and 18 o rain and between 18 o shell and rainfall amount r 2 0 79 and 0 85 respectively suggesting that h melanostoma shells can be used as a proxy for past rainfall conditions when combined in multiple linear regressions 18 o rain and rainfall amount explained 90 of the variance in 18 o shell r 2 0 90 simple and multiple linear regressions were used to develop predictive models for these climate parameters as h melanostoma shells are commonly found in mediterranean and north african archaeological and geological deposits the predictive equations developed in this study hold great potential for reconstructing pleistocene to holocene rainfall and aridity patterns in the gebel akhdar and for assessing the relationship between environmental changes and human behavioural changes

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

isotopic composition δ18o and δd of precipitation and groundwater in a semi arid mountainous area guadiana menor basin southeast spain we characterize the precipitation and groundwater in a mountainous peaks slightly above 3000 m a s l semi arid river basin in se spain in terms of the isotopes 18o and 2h this basin with an extension of about 7000 km2 is an ideal site for such a study because fronts from the atlantic and the mediterranean converge here much of the land is farmed and irrigated both by groundwater and runoff water collected in reservoirs a total of approximately 100 water samples from precipitation and 300 from groundwater have been analysed to sample precipitation we set up a network of 39 stations at different altitudes 800 1700 m a s l with which we were able to collect the rain and snowfall from 29 separate events between july 2005 and april 2007 and take monthly samples during the periods of maximum recharge of the aquifers to characterize the groundwater we set up a control network of 43 points 23 springs and 20 wells to sample every 3 months the main aquifers and both the thermal and non thermal groundwater we also sampled two shallow water sites a reservoir and a river the isotope composition of the precipitation forms a local meteoric water line lmwl characterized by the equation d 7 72 18o 9 90 with mean values for 18o and d of 10 28 and 69 33 respectively and 12 9 for the d excess value to correlate the isotope composition of the rainfall water with groundwater we calculated the weighted local meteoric water line wlmwl characterized by the equation d 7 40 18o 7 24 which takes into account the quantity of water precipitated during each event these values of d d d 18o 8 and d excess d 8 18o 10 in each curve bear witness to the amount effect an effect which is more manifest between may and september when the ground temperature is higher other effects noted in the basin were those of altitude and the continental influence the isotopic compositions of the groundwater are represented by the equation d 4 79 18o 18 64 the groundwater is richer in heavy isotopes than the rainfall with mean values of 8 48 for 18o and 59 27 for d the isotope enrichment processes detected include a higher rate of evaporation from detrital aquifers than from carbonate ones the effects of recharging aquifers from irrigation return flow and or from reservoirs leakage and enrichment in 18o from thermal water copyright 2010 john wiley sons ltd

mediterranean moisture source for an early holocene humid period in the northern red sea paleosalinity and terrigenous sediment input changes reconstructed on two sediment cores from the northernmost red sea were used to infer hydrological changes at the southern margin of the mediterranean climate zone during the holocene between approximately 9 25 and 7 25 thousand years ago about 3 per thousand reduced surface water salinities and enhanced fluvial sediment input suggest substantially higher rainfall and freshwater runoff which thereafter decreased to modern values the northern red sea humid interval is best explained by enhancement and southward extension of rainfall from mediterranean sources possibly involving strengthened early holocene arctic oscillation patterns and a regional monsoon type circulation induced by increased land sea temperature contrasts we conclude that afro asian monsoonal rains did not cross the subtropical desert zone during the early to mid holocene

holocene climatic changes in the western mediterranean from south east france to south east spain abstract holocene climatic changes along coastal regions from south east france to south east spain were studied using pollen ratios comparing modern pollen rain vegetation and climate along selected transects from the atlantic ocean to the mediterranean we obtained threshold values of two different ratios corresponding to the different climatic conditions along the transects these pollen ratios and threshold values were employed to characterize the holocene climatic changes from nine mediterranean coastal sites the results were compared with data from marine and continental pollen sequences distributed in the western mediterranean basin and with additional regional data independent of human activity lake level fluctuations alpine glacier advance and retreat chronology 14 c anomaly and cooling phases in eastern france and central europe the role of anthropogenic activities and climate on the changes in vegetation is discussed six major changes in vegetation cover were identified they correspond to aridification phases that occurred around 9500 9000 yr bp 10 900 9700 cal bp 7500 7000 yr bp 8400 7600 cal bp 4500 4000 yr bp 5300 4200 cal bp 3700 3300 yr bp 4300 3400 cal bp 2600 1900 yr bp 2850 1730 cal bp and 1300 1000 yr bp 1300 750 cal bp these arid episodes were regional responses to more global climatic changes and determined the changes in the vegetation cover humans undoubtedly enhanced the vegetation changes but none the less had to adapt to these new climatic conditions

systematic variations in the carbon and oxygen isotopic composition of pedogenic carbonate along elevation transects in the southern great basin united states stable carbon and oxygen isotope variations in holocene soil carbonates that formed in the unsaturated zone were examined along several elevation transects in the southern great basin united states a region with a semi arid climate our intent was to study the relationship between the stable isotopic composition of pedogenic carbonates and climate ecological variations differences in parent material and soil depth 13 c of pedogenic carbonate in three different soil profiles from different elevations decreases with soil depth indicating a decrease in the ratio of atmospheric to plantderived co 2 downprofile pedogenic carbonate at the soil air interface approaches a 13 c value in equilibrium with atmospheric co 2 in all three soils observed 13 c profiles for pedogenic carbonate can be described using a one dimensional model for 12 co 2 and 13 co 2 assuming isotopic equilibrium between soil co 2 and soil carbonate the modeled best fit to observed isotopic profiles suggests that the profile differences in part result from differing soil respiration rates at each site 13 c in deep pedogenic carbonate 50 cm varies by about 12 per mil over a 2 440 m elevation range being enriched in 13 c at the lowest elevations the slope of 13 c for these carbonates versus elevation is very similar for soils developed on carbonate and on noncarbonate parent materials depletion by 4 6 to 4 7 per mil per 1 000 m increase in altitude between 300 to 2 740 m above mean sea level for the localities studied this concordance makes it likely that there has been complete isotopic exchange between hco 3 in solution and soil co 2 prior to carbonate precipitation soil co 2 and soil respiration rates increase systematically with elevation the plantderived component of soil co 2 indicates that c 3 plants dominate the biomass at most measured sites in agreement with plant surveys calculated equilibrium fractionation factors between soil co 2 and soil carbonate are very similar to those observed again indicating complete isotopic exchange between carbon species in all the soil co 2 and soil carbonate data suggest that the 13 c variation with elevation observed in the soil carbonates results from differing soil respiration rates at each site as well as from variations in the proportion of c 3 to c 4 and cam plants in each site9s surface biomass 18 o values in pedogenic carbonates are higher at lower elevations due in part to the more positive 18 o values for meteoric waters at lower elevations the average 18 o value of deep 50 cm pedogenic carbonate at all sites however is enriched 2 4 to 3 7 per mil with respect to values we predict should be in equilibrium with the isotopic composition of local meteoric waters this suggests that evaporative isotopic enrichment of soil waters may have occurred at all elevations prior to precipitation of carbonate or that seasonal differences in the isotopic composition of meteoric waters coupled with differential infiltration may be taking place one or both of these processes also may explain the 18 o decrease in soil carbonate with depth observed in two of three soil profiles

pedogenic carbonate proxies for amount and seasonality of precipitation in paleosols the depth to carbonate nodular bk horizon in soils d in cm is correlated with mean annual precipitation p in mm so that bk horizons are deep in subhumid regions but shallow in semiarid regions previous quantifications of this relationship are unchanged by this new compilation of 807 soils p 137 24 6 45 d 0 013 d 2 where r 2 0 52 and standard error s e 147 mm in most north american postglacial soils the bk horizon is thin and well defined whereas in monsoonal tropical soils of pakistan and kenya the bk horizon is thick and diffuse data from 675 modern soils define the relationship between the thickness of soil with nodules t in cm and mean annual range of precipitation m in mm difference between monthly means of wettest and driest months m 0 79 t 13 71 where r 2 0 58 and s e 22 mm the relationship between carbonate nodule size s in cm and soil age a in ka is quantified by 9 radiocarbon dated soils from las cruces new mexico a 3 92 s 0 34 where r 2 0 57 and s e 1 8 k y these transfer functions are applied to reconstructing paleoclimatic change from paleocene eocene paleosols of the north horn formation and flagstaff limestone of axhandle canyon utah the terminal paleocene spike of warmth recorded by fossil plants in nearby wyoming was coincident with a brief peak in both mean annual precipitation and mean annual range of precipitation in utah

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

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

calibration of the stable isotope composition and body size of the arid dwelling land snail sphincterochila candidissima a climatic archive abundant in mediterranean archaeological deposits land snails recovered from archeological deposits may be used to deduce climatic conditions during prehistoric occupation because their aragonitic skeletons are usually well preserved and document valuable climatic information in the form of isotope codes since the snail sphincterochila candidissima is common in archeological sites along the western mediterranean but has been minimally investigated the present work examines the relationship between the oxygen 18o and carbon 13c stable isotopes of modern specimens and relevant meteorological data individuals of sphincterochila were regularly live collected throughout 1 year from september 2013 to october 2014 in tarragona ne spain and the 18o and 13c values were measured at the shell lip or aperture which depicts the last growth episode closest to specimens collection date shell margin 18o values varied from 3 1 in september to 0 8 in april average shell margin 18o values per collection date positively correlated with monthly avera

limestone and the problem of radiocarbon dating of land snail shell carbonate in order to test the role of limestone in producing anomalously old radiocarbon ages in land snail shells 14 c analyses were performed on shell carbonate of modern land snails from limestone and nonlimestone areas of jamaica no anomaly was found in snails from the nonlimestone area implying that such material is suitable for radiocarbon dating snails from limestone areas produced variable anomalies of as much as 3 120 yr due to incorporation of 14 c free limestone into shell carbonate all rock scraping snails and most leaf litter feeding snails from limestone areas showed anomalous 14 c contents because of the variability in 14 c content even within species no standard correction factor for limestone anomaly can be applied however dating error can be minimized by selecting ecologically appropriate species or by comparison of analyses of several fossil species within a stratum to their modern counterparts

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

holocene palaeohydrological changes in the northern mediterranean borderlands as reflected by the lake level record of lake ledro northeastern italy a lake level record of lake ledro northern italy spans the entire holocenewith a chronology derived from51 radiocarbon dates it is based on a specific sedimentological approach that combines data fromfive sediment profiles sampled in distinct locations in the littoral zone on a millennial scale the lake level record shows two successive periods from 11 700 to 4500 cal yr bp and from 4500 cal yr bp to the present characterized by lower and higher average lake levels respectively in addition to key seasonal and inter hemispherical changes in insolation the major hydrological change around 4500 cal yr bp may be related to a non linear response of the climate system to orbitally driven gradual decrease in insolation the ledro record questions the notion of an accentuated summer rain regime in the northern mediterranean borderlands during the boreal insolation maximum moreover the ledro record highlights that the holocenewas punctuated by successive centennial scale highstands correlations with the preboreal oscillation and the 8 2 ka event and comparisonwith the atmospheric 14c residual record suggest that short lived lake level fluctuations developed at ledro in response to 1 final steps of the deglaciation in the north atlantic area and 2 variations in solar activity

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

middle pleistocene mis 14 environmental conditions in the central mediterranean derived from terrestrial molluscs and carbonate stable isotopes from sulmona basin italy abstract a paleosol from the middle pleistocene lacustrine fluvial succession of sulmona basin central italy was analysed for the land snail shell content and the stable isotope composition of the shells and associated pedogenic carbonates the paleosol known as fiorata paleosol is covered by a thick tephra layer dated to ca 527 ka allowing the pedogenetic horizons to be correlated to the marine isotope stage mis 14 early mis 13 interval the terrestrial mollusc assemblage contained few individuals and was characterized by a low number of species which predominantly indicate open and dry habitats thus suggesting that fiorata paleosol likely developed during glacial conditions of the mis 14 the 13 c values of pedogenic carbonates and terrestrial shells indicate prevailing c 3 type vegetation probably marked by some degree of water stress calculation of the 18 o precipitation values derived from pedogenic carbonates and shell 18 o values indicate that the average temperature was 3 5 c lower than present day this study highlights how paleosols despite offering only snapshots of past climate and environments provide valuable complementary information to paleoclimatic data obtained in the adjacent lacustrine intervals specifically for the sulmona successions

kinetics and fractionation of carbon and oxygen isotopes during the solid phase transformation of biogenic aragonite to calcite the effect of organic matter abstract the phase transformation of biogenic shells from aragonite to calcite can modify the primary carbon and oxygen isotopic values 13c and 18o and thus affect their significance as paleoenvironmental proxies while the biasing of 13c and 18o by dissolution and reprecipitation phase transformation dr has been extensively studied thermal solid phase transformation spt in archaeological shell middens is rarely considered in this study the effects of intra crystalline organic matter on the kinetics and carbon and oxygen isotopic fractionation during thermal spt are evaluated by comparing two sets of experiments on powdered aragonite snail shells heated in air and pure nitrogen atmospheres the results show that during heating temperature below 400 c the intra crystalline organic matter could inhibit the phase transformation due to the shielding effect of organic matter while during heating temperature above 400 c the decomposition of the intra crystalline organic matter increases the kinetic rate of the phase transformation the activation energy for the phase transformation was determined to be 150 5 kj mol 1 lower than that of 247 kj mol 1 obtained for abiogenic polycrystalline aragonite and close to that of 158 to 163 kj mol 1 for abiogenic single crystal aragonite this is attributed to the larger lattice parameter c in biogenic aragonite and the increasing porosity of calcium carbonate with the decomposition of organic matter in a nitrogen atmosphere the deviation of 13c and 18o between the heated sample the mixture of aragonite and calcite and the original shell aragonite 13cm a and 18om a is negligible during heating temperature below 400 c however 13cm a from 0 43 to 0 00 and 18om a from 1 54 to 0 02 are significant during heating temperature above 400 c the temperature dependence of 13cm a in biogenic carbonates is much more significant than that in abiogenic carbonates which clearly reflects the occurrence of isotopic exchange between the intra crystalline organic matter and the carbonates in air the heating induced calcium carbonate is depleted in 13c by up to 0 48 and in 18o by up to 3 46 compared with the original samples which is mainly caused by isotopic exchange with the external carbon dioxide in air and the intra crystalline organic matter with the latter being the dominant source our results demonstrate that the decomposition of the intra crystalline organic matter increases the kinetic rate and induces carbon and oxygen isotope fractionation during spt from aragonite to calcite this study provides direct evidence for evaluating the preservation of carbon and oxygen isotopes of biogenic calcium carbonate shells which have undergone the spt process in archaeological shell middens

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

the evolution of hydroclimate in asia over the cenozoic a stable isotope perspective abstract links between tectonics and regional climate have been extensively studied in asia however despite decades of research the relative roles of tectonics and global climate in pacing the long term evolution of climate in asia remain disputed today climate in asia is characterized by large scale monsoonal circulation over india and southern china and exceptionally arid deserts across much of central asia that to the north yield to the wetter conditions of the steppe and taiga how why and if these boundaries have changed during the cenozoic has been limited by the lack of paleoclimate proxy data that can be broadly applied over space and time we use a large compilation of pedogenic and lacustrine carbonate stable oxygen 18o and carbon 13c isotope data 7 700 samples which record large scale atmospheric circulation and primary productivity respectively to reconstruct cenozoic hydroclimate in asia and delineate the boundaries through time of monsoonal and mid latitude westerly moisture the 18o data indicate that atmospheric circulation has remained similar to today for at least 55 million years southern tibet has always received southerly likely monsoonal moisture and this southerly moisture has likely rarely extended northward of the central tibetan plateau in contrast northern tibet and central asia have received moisture dominantly via the mid latitude westerlies which have maintained a semi arid to arid climate in central asia since the early eocene thus the spatial extent of large scale atmospheric circulation appears largely unperturbed by contemporaneous changes in india asia collisional tectonics extent of the paratethys and in global climate the 13c data support this interpretation but yield additional details particularly low 13c across a wide swath of eastern china during the eocene suggests greater primary productivity due to a strengthened east asia monsoon perhaps driven by high atmospheric pco2 and globally warm temperatures consistently higher 13c in central asia indicates that central asia has remained more arid than surrounding regions such as northern india and southern china which have received abundant precipitation due to the presence of monsoonal moisture however increases in 13c across much of central asia throughout the cenozoic including particularly pronounced increases in mongolia and kazakhstan during the neogene imply that primary productivity has declined across much of asia this large scale de greening is attributable to the combined effects of cenozoic global cooling and the late cenozoic uplift of the tian shan and altai mountains which block westerly moisture the uplift of these ranges in the late miocene is supported by decreasing neogene 18o in eastern kazakhstan and sharply increasing 13c in the lee of the altai these regional data demonstrate that the tian shan and altai reached sufficient elevations to interact with the westerly jet by the late miocene establishing a substantial rain shadow and shifting the seasonality of precipitation in western central asia we conclude that paleoclimatic changes during the cenozoic in central asia are more tightly controlled by global climate and by the interaction of the mid latitude westerlies with the tian shan and altai rather than by changes in the height or extent of the tibetan plateau or paratethys

rainfall in the negev desert during the middle holocene based on 13c of organic matter in land snail shells abstract analysis of stable carbon isotope ratios 13 c 12 c of organic matter in land snail shells is used to infer middle holocene rainfall amounts in the negev desert by reconstructing the distribution of c 4 plants in the family chenopodiaceae the organics are derived from the diet of the snails which consists of plant material and are enriched in 13 c where c 4 plants are present a survey of modern plant communities indicates that in areas receiving 300 mm mean annual rainfall nearly all plant communities consist of c 3 species only no c 4 chenopodes whereas in areas under 230 mm rainfall most plant communities contain one or more c 4 chenopode species in between is a transition zone consisting of a mosaic of both pure c 3 and mixed c 3 c 4 plant communities isotopic results for fossil land snails indicate a consistent geographic pattern throughout the middle holocene from ca 6500 to 3000 yr b p with the transition zone located ca 20 km south of its present position this implies a near doubling of rainfall within this region as compared to present

role of the westerlies in central asia climate over the cenozoic abstract there remains substantial debate concerning the relative roles of tectonics and of global climate in pacing the evolution of aridity in central asia over the cenozoic tibetan plateau uplift variable monsoonal strength paratethys retreat and reduced moisture transport from the north atlantic have all been hypothesized to drive aridity in central asia distinguishing between these mechanisms requires knowledge of moisture transport pathways to central asia through time presently central asia receives recycled high 18 o moisture that has been transported across eurasia by the westerlies while southern tibet receives low 18 o moisture distilled by passage over the himalaya here we reconstruct the spatial distribution of oxygen isotopes in precipitation since the early eocene using a compilation of 18 o data from 2750 sedimentary carbonate samples across asia the spatial distribution of paleo precipitation 18 o remains remarkably similar through time with low 18 o values in the lee of the himalaya in southern tibet constant high 18 o values in central asia and intermediate values on the central plateau despite independent evidence for substantial changes in both topography and climate through time these results suggest that a long standing topographic feature has continuously blocked southerly moisture and subsequent progressive uplift of the tibetan plateau has had little impact on central asian climate in turn southerly monsoonal moisture has never persistently extended northward of the central plateau as a result the westerlies have remained the dominant moisture source in central asia since at least the early eocene therefore sedimentary aridity indicators in central asia such as loess deposition are controlled by the trans eurasian westerly moisture flux rather than tibetan plateau uplift

onset of aridification by 34 ma across the eocene oligocene transition in central asia cenozoic climate has changed markedly from a warm wet climate to the present cool dry glacial interglacial cycles the largest of these cooling steps is thought to have taken place across the eocene oligocene transition terrestrial airborne eolian loess is a direct result of land aridification therefore the prolonged formation of thick eolian loess deposits provides a key to aridification history in the geological past however the oldest eolian loess in the asian interior has been dated to only 25 22 ma here we present new sedimentological geochemical and magnetostratigraphic data from cenozoic sections in southwestern mongolia to show that the earliest eolian dust accumulation occurred by 34 ma 10 m y earlier than currently believed we suggest that this oldest eolian dust accumulation provides direct evidence for enhanced aridification across the eocene oligocene transition in central asia this is explicable by reduced moisture transport caused by prevailing westerlies during retreat of the neotethys ocean these climatic changes were related to the changing regional plate configuration as well as to global cooling and ice sheet growth in antarctica

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

carbon isotope ratio of cenozoic co2 a comparative evaluation of available geochemical proxies 1 the carbon isotope ratio 13c of plant material is commonly used to reconstruct the relative distribution of c3 and c4 plants in ancient ecosystems however such estimates depend on the 13c of atmospheric co2 13cco2 at the time which likely varied throughout earth history for this study we use benthic and planktonic 13c and 18o records to reconstruct a long term record of cenozoic 13cco2 confidence intervals for 13cco2 values are assigned after careful consideration of equilibrium and non equilibrium isotope effects and processes as well as resolution of the data we find that benthic foraminifera better constrain 13cco2 compared to planktonic foraminiferal records which are influenced by photosymbiotes depth of production seasonal variability and preservation furthermore sensitivity analyses designed to quantify the effects of temperature uncertainty and diagenesis on benthic foraminifera 13c and 18o values indicate that these factors act to offset one another our reconstruction suggests that cenozoic 13cco2 averaged 6 1 0 6 1 while only 11 2 million of the last 65 5 million years correspond to the pre industrial value of 6 5 with 90 confidence here 13cco2 also displays significant variations throughout the record at times departing from the pre industrial value by more than 2 thus the observed variability in 13cco2 should be considered in isotopic reconstructions of ancient terrestrial plant ecosystems especially during the late and middle miocene times of presumed c4 grassland expansion

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

stable isotope composition of late glacial land snail shells from grotta del romito southern italy palaeoclimatic implications abstract stable isotope composition of living and fossil land snail shells was determined at grotta del romito southern italy with the aim to reconstruct environmental and climatic variation in the area during late upper palaeolithic the investigated succession comprised 15 different excavated layers spanning between ca 13 000 and 14 500 yr cal bp the oxygen isotope composition of snail shells indicates a marked decrease at the layer d8 suggesting a climatic deterioration consistent with the gi 1d climatic event older dryas this climate deterioration may have been related to a substantial decrease of mean annual temperature with associated changes in the regional atmospheric circulation however the environmental conditions at the time of shell s growth in the other intervals sampled suggest condition comparable to the present day the carbon isotope composition of fossil snail shells is in agreement with other records which indicate a general increase of the 13 c values of organic matter during pleniglacial to late glacial caused by substantially lower atmospheric co 2 concentration at that time

aridification in continental asia after the middle eocene climatic optimum meco global climate cooling from greenhouse to icehouse conditions occurred across an enigmatic transitional interval during the eocene epoch characterized by incipient polar ice sheet formation as well as short lived warming events of which the middle eocene climatic optimum meco is most noticeable understanding this critical period requires high resolution records that are being gathered in marine basins but are still lacking in the terrestrial realm here we provide a precisely dated terrestrial record crossing the meco time interval from the xining basin nw china we document a rapid aridification step and the onset of obliquity dominated climate cyclicity indicated by lithofacies and pollen records dated at 40 0 ma at the base of magnetochron c18n 2n this shift is concomitant within error with the meco peak warming in ocean drilling program site 1258 for which we reassessed the magnetostratigraphic age at 40 0 ma also at base of magnetochron c18n 2n the rapidity of the shift observed in the xining basin and the region wide aridification and monsoonal intensification reported around 40 ma suggests asian paleoenvironments were responding to global climate changes associated with the meco however the xining records show only the permanent shift but not the transient peak warming observed in marine meco records we thus relate this permanent aridification to occur during the post meco cooling we propose the mechanisms linking global climate to asian paleoenvironments may be eustatic fluctuations driving the stepwise retreat of the proto paratethys epicontinental sea or simply global cooling reducing moisture supply to the continental interior in any case eocene global climate cooling from greenhouse to icehouse conditions seem to have played a primary role in shaping asian paleoenvironments

landslide faults and tectonic faults analogs the slumgullion earthflow colorado recent geophysical observations of landslide movement support the hypothesis that processes involved in landslide faulting are analogous to those that operate in crustal scale faulting relative to crustal faulting studies quantitative seismic geodetic and creep measurements of landslide deformation may be made in a very short time with readily available instrumentation and at relatively minimal expense our results indicate that the displacement of landslide material occurs along discrete faults exhibiting a combination of brittle failure indicated by slide quakes and creep events and as stable sliding observed as steady state creep although slide quakes were observed a more steady state failure process of relieving accumulating strain is indicated

the postglacial record of environmental history from lago di pergusa sicily lacustrine sedimients from lago di pergusa in central sicily provide a postglacial record of environmental change in the mediterranean magnetic susceptibility measurements lithofacies characterization and pollen analysis were carried out anid integrated to obtain a better reconstruction of the past 11000 years the chronoogy is provided by ams radiocarbon dates on macrofossils or bulk sediment and by a tephra correlative with a late holocene explosion from the etna volcano the transition period related to the present interglacial reafforestation characterized by increasing humidity started about 10700 years bp the onset of the wettest conditions of the postglacial occurred at about 9000 years bp and lasted until about 7200 years bp then a trend towards aridification began leading to very dry conditions at about 3000 years bp an unquestionable human impact on vegetation is found from 2800 years bp although earlier land use cannot be excluded as the climate had already induced change in the vege

modern soil system constraints on reconstructing deep time atmospheric co2 abstract paleosol carbonate based estimates of paleo atmospheric co 2 play a prominent role in constraining radiative forcing and climate sensitivity in the deep time large uncertainty in paleo co 2 estimates made using the paleosol carbonate co 2 barometer however arises primarily from their sensitivity to soil respired co 2 s z this parameter is poorly constrained due to a paucity of soil co 2 measurements during carbonate formation in modern soils and a lack of widely applicable proxies of paleo soil co 2 here the 13 c values of carbonate and soil organic matter som pairs from 130 holocene soils are applied to a two component co 2 mixing equation to define soil order specific ranges of soil co 2 applicable for constraining s z in their corresponding paleosol analogs equilibrium carbonate som pairs characterized by 13 c carb som values of 12 2 15 8 define a mean effective fractionation of 14 1 and overall inferred total soil co 2 contents during calcite formation of s z during calcite formation is 1500 2000 ppmv range of 500 2500 ppmv overall higher values 2000 5000 ppmv are indicated by the subset of these soils characterized by higher moisture content and productivity near atmospheric levels 400 200 ppmv of estimated s z are indicated by immature soils recording their low soil productivity vertisols define the largest range in total soil co 2 25 000 ppmv reflecting their seasonally driven dynamic hydrochemistry a s z range of 1000 10 000 ppmv is suggested for paleo vertisols for which calcite precipitation can be constrained to have occurred in an open system with two component co 2 mixing with a best estimate of 2000 ppmv 1000 ppmv appropriate for paleo vertisols for which evidence of protracted water saturation is lacking mollisol pairs define a best estimate of s z of 2500 ppmv range of 600 4000 ppmv for late cretaceous and cenozoic analogs non equilibrium pairs with 13 c values 16 make up 51 of the dataset lending support to the hypothesis that pedogenic carbonate precipitation occurs during periods of low productivity in a soil atmosphere with a large component of atmospheric co 2 predictable scaling between estimated soil co 2 and the difference in 13 c between measured pedogenic carbonate and that predicted to have formed from soil respired co 2 inferred from measured som can be used to further constrain appropriate ranges of s z for reconstruction of paleo atmospheric p co 2 soil co 2 estimates are poorly correlated to mean annual precipitation likely reflecting that for carbonate bearing soils where moisture limits co 2 production total soil co 2 is most strongly influenced by actual evapotranspiration

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

land snails from late glacial and early holocene italian sites abstract a survey of the literature published over the last 50 years on late glacial and early holocene malacofauna in italy shows that it is possible to obtain information on taxa their abundance chorological categories and palaeoenvironments however those aspects are only partly known for northern italy including only a few publications to the end of the 1990s thanks to greater interdisciplinary collaboration those of the past ten years are more useful providing data on palaeoenvironments and other aspects of more than forty caves and rockshelters that contain malacofauna only about a dozen scattered throughout northern central and southern italy proved useful for distinguishing natural deposits from artificial shell middens whereas the intentional gathering and transport of marine molluscs to places of consumption is perfectly plausible it remains problematic to understand what can and cannot be considered food waste in the case of land snails there are only a few sites for which there is evidence of potentially edible land snails in combination with other important archaeological and palaeontological analyses a better methodology for future research in italy is imperative

late miocene pliocene asian monsoon intensification linked to antarctic ice sheet growth environmental conditions in one of earth s most densely populated regions east asia are dominated by the monsoon while quaternary monsoon variability is reasonably well understood pre quaternary monsoon variability and dynamics remain enigmatic in particular little is known about potential relationships between northern hemispheric monsoon response and major cenozoic changes in antarctic ice cover here we document long term east asian summer monsoon easm intensification through the late miocene pliocene 8 2 to 2 6 ma and attribute this to progressive antarctic glaciation our new high resolution magnetic records of long term easm intensification come from the late miocene pliocene red clay sequence on the chinese loess plateau we identify underlying mechanisms using a numerical climate model simulation of easm response to an idealized stepwise increase in antarctic ice volume we infer that progressive antarctic glaciation caused intensification of the cross equatorial pressure gradient between an atmospheric high pressure cell over australia and a low pressure cell over mid latitude east asia as well as intensification of the cross equatorial sea surface temperature sst gradient these combined atmospheric and oceanic adjustments led to easm intensification our findings offer a new and more global perspective on the controls behind long term asian monsoon evolution

can carbon 13 in large herbivores reflect the canopy effect in temperate and boreal ecosystems evidence from modern and ancient ungulates abstract local environmental conditions under dense canopy are known to result in depletion in 13c abundance in plants compared to an open land context this canopy effect has been observed in tropical as well as in mid latitude forest ecosystems however the impact of the canopy effect on tissue 13c abundance of temperate and boreal forest dwelling herbivores has not been thoroughly explored nevertheless the canopy effect has been suggested to explain a decrease of about 3 in collagen 13c values in ancient large herbivores from western europe during the forest expansion of the late glacial early holocene period ca 15 000 6000 cal bp some papers have considered the 13c decrease in large herbivore as the main result of global change in atmospheric co2 content a detailed review of 13c values of large herbivores reindeer red deer roe deer and bison from open and closed environments from high and mid latitudes confirm that the canopy effect observed in plants is passed on to their consumers in the paris basin the decline in 13c values of large herbivores at the late glacial early holocene transition around 10 000 years bp appears to be different according to the considered species namely red deer roe deer and large bovines bison and aurochs moreover differences in the pattern of decrease in 13c values are observed in red deer between french northern alps and french jura these differences among species in their isotopic response through time for a given geographical location and within species from different locations suggest variance in ecological responses of species that are associated with the relative use of forested habitat as a result 13c abundances in collagen can be considered as a direct tracker of the degree of closure of the habitat of ancient herbivores

lateglacial and holocene palaeohydrology in the western mediterranean region the lake estanya record ne spain abstract the multi proxy analysis of sediment cores recovered in karstic lake estanya 42 02 n 0 32 e 670 m a s l ne spain located in the transitional area between the humid pyrenees and the semi arid central ebro basin provides the first high resolution continuous sedimentary record in the region extending back the last 21 000 years the integration of sedimentary facies elemental and isotopical geochemistry and biogenic silica together with a robust age model based on 17 ams radiocarbon dates enables precise reconstruction of the main hydrological and environmental changes in the region during the last deglaciation arid conditions represented by shallow lake levels predominantly saline waters and reduced organic productivity occurred throughout the last glacial maximum 21 18 cal kyrs bp and the lateglacial reaching their maximum intensity during the period 18 14 5 cal kyrs bp including heinrich event 1 and the younger dryas 12 9 11 6 cal kyrs bp less saline conditions characterized the 14 5 12 6 cal kyrs bp period suggesting higher effective moisture during the bolling allerod the onset of more humid conditions started at 9 4 cal kyrs indicating a delayed hydrological response to the onset of the holocene which is also documented in several sites of the mediterranean basin higher although fluctuating holocene lake levels were punctuated by a mid holocene arid period between 4 8 and 4 0 cal kyrs bp a major lake level rise occurred at 1 2 cal kyrs bp conducive to the establishment of conditions similar to the present and interrupted by a last major water level drop occurring around 800 cal yrs bp which coincides with the medieval climate anomaly the main hydrological stages in lake estanya are in phase with most western mediterranean and north atlantic continental and marine records but our results also show similarities with other iberian and northern african reconstructions emphasizing peculiarities of palaeohydrological evolution of the iberian peninsula during the last deglaciation

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

holocene cultural and climate shifts in nw africa as inferred from stable isotopes of archeological land snail shells cultural transitions or even societal collapses have often been associated with long term drought events linkages between humans and the environment are best documented in well constrained archeol

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

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

episodic deposition of illinois valley peoria silt in association with lake michigan lobe fluctuations during the last glacial maximum the chronology and cause of millennial depositional oscillations within last glacial loess of the central lowlands of the united states are uncertain here we present a new age model that indicates the peoria silt along the illinois river valley accumulated episodically from 28 500 to 16 000 cal yr bp as the lake michigan lobe margin fluctuated within northeastern illinois the age model indicates accelerated loess deposition coincident with regional glacial advances during the local last glacial maximum a weakly developed paleosol the jules geosol represents a period of significantly slower deposition from 23 700 to 22 000 cal yr bp a gastropod assemblage based reconstruction of mean july temperature shows temperatures 6 10 c cooler than modern during peoria silt deposition stable oxygen and carbon isotope values 18 o and 13 c of gastropod carbonate do not vary significantly across the pedostratigraphic boundary of the jules geosol suggesting slower loess accumulation was a result of reduced glacial sediment supply rather than direct climatic factors however a decrease in 18 o values occurred between 26 000 and 24 000 cal yr bp synchronous with the lake michigan lobe s southernmost advance this 18 o decrease suggests a coupling of regional summer hydroclimate and ice lobe position during the late glacial period

development of asian monsoon revealed by marked ecological shift during the latest miocene in northern pakistan carbon isotopes from soil carbonate1 4 and soil organic matter5 6 yield palaeoecological information because the carbon in the soil carbonate forms in isotopic equilibrium with local soil co2 refs 1 7 the isotopic composition of which is in turn determined by local plant cover siwalik group sediments in northern pakistan contain a well exposed palaeosol record spanning the past 18 myr here we report on stable carbon isotope results from associated pedogenic carbonate which indicate a dramatic ecological shift from to dominated floodplain biomass beginning 7 4 7 0 myr ago the earlier c3 floodplain biomasses were probably mainly composed of trees and shrubs whereas c4 grasslands dominated in the plio pleistocene oxygen isotopes also exhibit a shift in the latest miocene probably corresponding to a major climate change which may have induced the forest to grassland transition this dramatic ecological shift in the latest miocene may mark the inception or a marked strengthening of the asian monsoon system

hydrological conditions over the western mediterranean basin during the deposition of the cold sapropel 6 ca 175 kyr bp a new oxygen isotope record is reported from a stalagmite collected in the argentarola cave located on the tyrrhenian coast of italy as shown from observations and numerical modeling of n 18 o in modern precipitation the recorded n 18 o variability for this zone is dominated by the amount of precipitation so called amount effect the n 18 o profile measured in the stalagmite is characterized by a prominent negative excursion ca 2 3x between 180 and 170 kyr bp this paleoclimatic feature is interpreted as being due to a relatively wet period which occurred during the penultimate glacial period more precisely during marine isotope stage 6 5 this pluvial phase is shown to correspond chronologically to the deposition of the sapropel event 6 s6 although this particular sapropel event occurred during a cold phase the n 18 o excursion is similar to those corresponding to other sapropels s4 s3 and s2 the evidence for humid conditions during s6 in the western mediterranean basin agrees with previous studies based on deep sea sediment cores taken collectively the data suggest that during sapropel events dilution of ocean surface waters was not restricted to the output of the river nile but was rather widespread over the entire mediterranean sea due to increased rainfall 2002 elsevier science b v all rights reserved

holocene climate variability in the western mediterranean region from a deepwater sediment record 1 the detailed analysis of the international marine past global changes study core md99 2343 recovered from a sediment drift at 2391 m water depth north of the island of minorca illustrates the effects of climate variability on thermohaline circulation in the western mediterranean during the last 12 kyr geochemical ratios associated with terrigenous input resulted in the identification of four phases representing different climatic and deepwater overturning conditions in the western mediterranean basin during the holocene superimposed on the general trend eight centennial to millennial scale abrupt events appear consistently in both grain size and geochemical records which supports the occurrence of episodes of deepwater overturning reinforcement in the western mediterranean basin the observed periodicity for these abrupt events is in agreement with the previously defined holocene cooling events of the north atlantic region thus supporting a strong atlanticmediterranean climatic link at high frequency time intervals during the last 12 kyr the rapid response of the mediterranean thermohaline circulation to climate change in the north atlantic stresses the importance of atmospheric teleconnections in transferring climate variability from high latitudes to midlatitudes

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

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

strengthened east asian summer monsoons during a period of high latitude warmth isotopic evidence from mio pliocene fossil mammals and soil carbonates from northern china the east asian monsoons have fluctuated in concert with high latitude warmth during the past several hundred thousand years with humid summer monsoon dominant climates characterizing warm intervals including interglacials and interstadials and arid winter monsoon dominant climates characterizing cool intervals including glacials and stadials of the states comprising the mid pleistocene to recent climatic regime interglacials are most similar in terms of high latitude ice volumes and temperatures to those extant during the late miocene and early pliocene thus an important question is whether mio pliocene climates in northern china were analogous to a hypothetical prolonged interglacial state with increased summer monsoon precipitation and expansion of forest and steppe environments at the expense of desert environments we utilize new and previously published carbon isotopic data from fossil teeth and soil carbonates to place constraints on paleovegetation distributions and to help infer the behavior of the monsoon system between 7 and 4 ma we find that plants using the c 4 photosynthetic pathway which today are largely grasses found in regions with warm season precipitation were present in northern china by late miocene time demonstrating that the c 4 expansion in china was not significantly delayed compared to the global c4 event during the late miocene early pliocene interval soil carbonate and tooth enamel 13 c data indicate 1 that nearly pure c 3 plant ecosystems existed in the southern chinese loess plateau clp and therefore ecosystems there were dominated by woody dicot herbaceous dicot or cool season grass vegetation or a combination of these and 2 that the clp was characterized by a pattern of northward increasing c 4 vegetation and aridity utilizing a broadened conceptual model for interpreting 13 c data and citing independent faunal floral and lithostratgraphic data we suggest that these patterns reflect northward expansion of forest and steppe ecosystems and relatively humid monsoon climates during the late miocene and early pliocene an important implication of this interpretation is that the forcing mechanism illuminated by the temporal correlation during the pleistocene between warm high latitudes and strong east asian summer monsoons is a robust feature of the eurasian tectonic climatic system that predates the plio pleistocene climatic reorganization

paleoclimate change since the miocene inferred from clay mineral records of the jiuquan basin nw china abstract global cooling and the uplift of the tibetan plateau have long been considered the crucial controls of the climate change in inland asia since the cenozoic however which of these factors has played the leading role is unknown to understand climate change and the controlling factors in inland asia here we present new records of clay mineralogy and trace elements of clay fractions from the neogene sedimentary sequence in the jiuquan basin of the northeastern tibetan plateau the clay mineral records reveal four stages of paleoclimate changes from ca 24 ma to 17 ma the low total smectite and smectite i s mixed layers kaolinite illite chlorite and high illite contents suggest weak chemical weathering and hence arid climatic conditions for ca 17 14 ma the high total smectite and total smectite kaolinite illite chlorite and low illite contents suggest strong chemical weathering indicating a change in climate from cold and dry to warm and humid there was no palygorskite during this warm and humid period from ca 14 ma to 8 ma the low total smectite content high illite content and the appearance of palygorskite indicate that the climate turned to cold and dry since 8 ma low total smectite as well as high illite and chlorite contents suggest a colder and drier period the records of clay mineralogy illustrate that the jiuquan basin has experienced increasing aridity since ca 14 ma synchronous with the inland asian aridification given the synchroneity with the global cooling we suggest that the climate evolution in the jiuquan basin from the late oligocene to middle late miocene was mainly controlled by global climate change since the late miocene the uplift of the tibetan plateau and global cooling have significantly influenced the decreasing temperature and humidity of the jiuquan basin the uplift of tibetan plateau may intensify the aridity by blocking moisture from reaching the jiuquan basin

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

a late pleistocene refugium in mediterranean north africa palaeoenvironmental reconstruction from stable isotope analyses of land snail shells haua fteah libya abstract the late pleistocene to holocene archaeological record of north africa is key to understanding the emergence of anatomically modern humans into west asia and europe and the broadening of subsistence strategies in the shift from hunter gatherer to pastoral agricultural lifeways some contend that these developments were modulated by major shifts in climate and environment evaluation of this hypothesis requires the pairing of local and regional climate records with well dated archaeological sequences the haua fteah archaeological site in the gebel akhdar region of libya provides a key site to test this hypothesis as the cave contains one of the longest and most complete sequences of human occupation in north africa as well as abundant material for palaeoenvironmental reconstruction this study uses stable isotope analyses 18o and 13c of the terrestrial mollusc helix melanostoma to construct a palaeoenvironmental framework for interpreting north african human environment interactions from the upper palaeolithic to the neolithic 30 000 to 5000 years ago the land snail stable isotope records from haua fteah suggests that cool arid conditions in the cave peaked during marine isotope stage mis 2 this stage was however only marginally drier than previous and subsequent stages and coincided with an increase in occupation density in the cave this suggests that the gebel akhdar may have served as an environmental refugium from the more extreme aridity in the surrounding sahara and arid coastal plains for late stone age lsa populations in north africa conditions became progressively wetter towards the holocene however generally wetter conditions were interrupted by two arid episodes at c 8 0 ka and 7 3 ka that appear to coincide with regional changes reflected elsewhere in the mediterranean basin

spatio temporal patterns of holocene environmental change in southern sicily abstract few examples of natural forest remain near the mediterranean coast therefore it is difficult to study how coastal forests respond to climatic change or their resilience to human impact we developed new sedimentary record of holocene vegetation and fire history at lago preola a coastal lake in southwestern sicily italy in order to verify the existence of forest at large scale on the coast we compare pollen from lago preola a medium sized lake 33 ha to gorgo basso a small lake 3 ha located nearby with the aim of separating local from extra local vegetation dynamics through time using pollen percentages and influx we then compare lago preola pollen to the record from biviere di gela a large lagoon 120 ha situated 160 km to the east in southern sicily to examine differences in vegetation dynamics between the two coastal areas during the holocene lake level reconstructions and ostracode analyses from lago preola provide vegetation independent evidence of climate change and help to disentangle human and climatic impacts on vegetation pollen data indicate pistacia dominated shrublands replaced open grasslands in the region surrounding lago preola by 9500 cal yr bp this change coincided with rising lake levels and the development of an ostracode fauna typical of fresh waters evergreen forest dominated by quercus ilex and olea europaea started to expand by 7000 cal bp and consolidated at 6500 cal yr bp when lake levels were near their holocene high similarities between pollen from lago preola and gorgo basso demonstrate that forest was the dominant vegetation type in coastal sicily during the middle holocene at both regional and local scales and even developed in the drier climatic setting around biviere di gela lake levels fell at lago preola after 7000 cal yr bp with a strong decline accompanied by increasing salinity after 4500 cal yr bp however no transition in vegetation matched these inferred hydrological changes instead forests persisted in the surrounding region until 2200 cal bp when human disturbance intensified we propose that different climatic factors control lake levels and vegetation in coastal mediterranean ecosystems whereas lake levels are most sensitive to the abundance of winter precipitation coastal forests depend on spring precipitation and are limited by the length of summer drought moisture availability remained suitable for evergreen forests in coastal sicily during the late holocene and humans not a drier climate drove the regional forest decline

holocene 4 5 1 7 cal kyr bp paleoenvironmental conditions in central argentina inferred from entire shell and intra shell stable isotope composition of terrestrial gastropods the isotopic fingerprint of terrestrial gastropods has been increasingly used as a credible natural paleoenvironmental archive most published work has used this proxy at tropical and temperate latitudes of the northern hemisphere and focused on entire shell analysis the present study provides entire shell and intra shell isotopic profiles to infer average and seasonal late holocene environmental conditions in central argentina 30 s shells of plagiodontes daedaleus gastropoda odontostomidae were retrieved from the alero deodoro roca sector b site one of the few archaeological sites in central argentina rich in shells collected by pre hispanic hunter gatherer groups ancient entire shells exhibited values that were 2 5 higher in 13c and 1 8 higher in 18o than modern individuals pointing to higher abundance of c4 plants and overall drier conditions lower relative humidity and or higher rain 18o during 4 5 1 7 cal kyr bp than today in agreement with published regional proxies intra shel

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

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

holocene seasonality changes in the central mediterranean region reconstructed from the pollen sequences of lake accesa italy and tenaghi philippon greece this study presents pollen based climate reconstructions of holocene temperature and precipitation seasonality for two high resolution pollen sequences from the central lake accesa central italy and eastern mediterranean tenaghi philippon greece regions the quantitative climate reconstruction uses multiple methods to provide an improved assessment of the uncertainties involved in palaeoclimate reconstructions the multimethod approach comprises partial least squares regression weighted average partial least squares regression the modern analogues technique and the non metric multidimensional scaling generalized additive model method we find two distinct climate intervals during the holocene the first is a moist period from 9500 to 7800 cal bp characterised by wet winters and dry summers resulting in a strongly seasonal hydrological contrast stronger than today that is interrupted by a short lived event around 8200 cal bp this event is characterised by wet winters and summers at accesa wh

stable isotope composition of middle to late holocene land snail shells from the marroquies archeological site jaen southern spain paleoenvironmental implications abstract the marroquies archeological site located in the metropolitan area of jaen 37 46 southern spain contains land snail shells which have been preserved jointly with other human and zooarcheological remains new radiocarbon analyses carried out on pristine domestic animal and human bones confirmed that these remains belong to the copper age interval 4470 3880 cal bp n 8 land snail entire shells of two species one herbivorous and one omnivorous were analyzed for 13 c 12 c and 18 o 16 o ratios to estimate the paleoenvironmental conditions prevailing during the middle to late holocene in the southernmost part of europe the 13 c values of fossil shells ranged from 13 8 to 8 1 n 15 whereas modern specimens ranged from 10 8 to 8 6 n 20 the fact that ancient and modern shells generally exhibited similar 13 c values suggests that the 13 c values of the vegetation have remained relatively stable during 4470 3880 cal bp and the present snail species did not differ in 13 c values despite their differing dietary habits the 18 o values of fossil shells ranged from 4 9 to 1 2 n 15 whereas modern specimens ranged from 2 8 to 0 9 n 20 fossil shells were on average 2 lower in 18 o values than modern shells calculations from a snail evaporative steady state flux balance model suggest that shells at 4470 3880 cal bp precipitated under appreciably higher relative humidity conditions than today whereas rain 18 o values and air temperatures at the soil air interface during snail active period were possibly similar although samples from this study represent a time period in which the well documented late holocene aridification trend in southern spain already started snails suggest conditions at 4470 3880 cal bp were yet noticeably wetter than at present this study shows that land snail shells preserved in holocene archeological sites offer valuable paleoenvironmental information in their isotope codes

younger dryas early holocene transition in the south eastern iberian peninsula insights from land snail shell middens the land snail sphincterochila candidissima from archeological records in villena se spain was studied isotopically to estimate the younger dryas yd early holocene transition in the western mediterranean live collected individuals exhibited body 21 8 1 6 and shell 5 8 1 4 d 13 c values typical of a c3 plant diet probably combined with carbonate ingestion calculations of a carbon flux balance mixing model suggest that living specimens experienced similar metabolic rates with comparable ratio of input and output fluxes of bicarbonate from the snail hemolymph all fossil shells showed comparable d 13 c values among each other but values were 2 higher than living specimens this may be explained by higher water stress at the yd holocene transition or by the suess effect shell d 18 o values averaged 1 3 0 8 for living individuals 0 5 0 8 for holocene 8 4 10 2 cal ka bp specimens and 0 4 0 6 for yd 12 0 12 4 cal ka bp snails an oxygen flux balance mixing model suggests that yd shells precipitated during relative humidity rh values of 79 82 after which rh increased gradually reaching maximum values of 87 88 at 8 4 8 6 cal ka bp and from there rh eventually declined to present values of 82 comparisons with other snail data suggest that the xerophilous sphincterochila records different environmental signatures fro other contemporaneous taxa copyright 2013 john wiley sons ltd

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

asian monsoons in a late eocene greenhouse world the strong present day asian monsoons are thought to have originated between 25 and 22 million years myr ago driven by tibetan himalayan uplift however the existence of older asian monsoons and their response to enhanced greenhouse conditions such as those in theeocene period 55 34myrago are unknownbecause of the paucity of well dated records here we show late eocene climate records revealing marked monsoon like patterns in rainfall and wind south and north of the tibetan himalayan orogen this is indicated by low oxygen isotope values with strong seasonality in gastropod shells and mammal teeth from myanmar and by aeolian dust deposition in northwest china our climate simulations support modern like eocene monsoonal rainfall and show that a reinforced hydrological cycle responding to enhancedgreenhouse conditions counterbalanced the negative effect of lowertibetanrelief onprecipitation these strong monsoons later weakened with the global shift to icehouse conditions 34myr ago

onset of asian desertification by 22 myr ago inferred from loess deposits in china the initial desertification in the asian interior is thought to be one of the most prominent climate changes in the northern hemisphere during the cenozoic era1 2 3 4 but the dating of this transition is uncertain partly because desert sediments are usually scattered discontinuous and difficult to date here we report nearly continuous aeolian deposits covering the interval from 22 to 6 2 million years ago on the basis of palaeomagnetic measurements and fossil evidence a total of 231 visually definable aeolian layers occur as brownish loesses interbedded with reddish soils this new evidence indicates that large source areas of aeolian dust and energetic winter monsoon winds to transport the material must have existed in the interior of asia by the early miocene epoch at least 14 million years earlier than previously thought3 5 regional tectonic changes and ongoing global cooling are probable causes of these changes in aridity and circulation in asia

new evidence on the age of the taklimakan desert the taklimakan desert is the world s second largest shifting sand desert located in the rain shadow of the tibetan plateau the initiation of desert formation in the asian interior is one of the most prominent climate changes in the northern hemisphere during the cenozoic era dating the earliest formation of this desert is important for understanding the climatic effects of the uplifted tibetan plateau here we report 1071 m thick neogene deposits with inter calated eolian dune sands from the only outcrop in the central taklimakan desert based on paleo magnetic measurements biostratigraphic age control and previous electron spin resonance dating results the oldest in situ eolian dune sands were confi rmed to be ca 7 ma much older than the previous reported wind blown siltstone from the southern edge of the taklimakan desert this new result indicates that desert conditions initiated ca 7 ma in the center of the tarim basin we attribute this event to the late cenozoic climatic deterioration and or to the rain shadow effect caused by late miocene uplift of the northern tibetan margin

the neogene de greening of central asia there remains substantial debate concerning the relative roles of tectonics and global climate in driving the evolution of climate in central asia today interior asia including the taklamakan gobi and ordos deserts is exceptionally arid and is surrounded by distinct rainfall boundaries such as those generated by the asian monsoon systems to the east and south and those generated by high topography to the north and west determining how and why these boundaries have varied over the neogene is hindered by the lack of a single proxy that can be broadly applied through space and time we construct isoscapes of pedogenic carbonate 13 c 13 c c over the neogene in asia by combining a compilation of 2236 published measurements with new data from three localities in northern central asia pedogenic carbonate 13 c records local aridity excepting localities impacted by c 4 grasslands and during large changes in atmospheric p co 2 through variations in soil respiration depth of carbonate formation and the effect of water stress on plant 13 c together these effects reflect changes in both primary productivity and mean annual precipitation throughout the neogene we find consistent and exceptionally high 13 c c in interior asia with a ring of lower 13 c c that demarcates higher precipitation this persistent ring of lower 13 c c corresponds in the south and east with the influence of the asian monsoon systems in the west and north it reflects both orographic rainfall due to uplift of the tian shan and to moisture delivery by the mid latitude westerlies finally 13 c c and hence aridity increases regionally in the latest neogene reflecting the effects of northern hemisphere glaciation and cooling this widespread de greening would have increased regional albedo and modified basin scale water balances resulting in greater dust fluxes due to reduced vegetative cover and precipitation

increased seasonality and aridity drove the c4 plant expansion in central asia since the miocene pliocene boundary abstract continuous and high resolution records of the content mass accumulation rate mar and 13 c values of black carbon obtained from integrated ocean drilling program iodp site u1430 in the southwestern japan sea have been established and combined with previous results obtained from central asia the main objective of this work is to reconstruct the historical changes in vegetation types c3 c4 and to constrain the driving force of c4 plant expansion over the last 13 ma the stable carbon isotope value of black carbon 13 c bc shows a major shift since the miocene pliocene boundary 5 3 ma suggesting significant expansion of c4 plants in broad areas of central asia including the inland basins of northwestern china and the loess plateau however a decline in the content and mar of black carbon reveals the absence of any link between fire and c4 plant expansion in central asia due to the dramatic decrease in biomass under a drying regime on a global scale asynchronous expansion of c4 plants suggests that regional hydroclimatic change rather than decline in co 2 concentration was the most important factor to influence c4 expansion we propose that the increased seasonality and the enhanced long term aridity driven by the concurrent decline in winter westerly vapor and increase in east asian summer monsoon precipitation were the main driving forces of c4 plant expansion in broad areas of central asia variations in winter westerly moisture have played a significant role in changes of regional climate and vegetation in central asia since the late miocene