oxygen and carbon isotope signatures in late neogene horse teeth from spain and application as temperature and seasonality proxies abstract here we describe a data set of 249 stable o and c isotope compositions from fossil horse teeth from the upper neogene of central spain and discuss their potential as environmental proxies it has been shown before that horse tooth enamel 18 o is a good proxy for local meteoric water 18 o h2o which in turn bears a distinct relation to temperature during precipitation formation at mid to high latitudes we discuss the reconstructed 18 o h2o values and apply modern 18 o h2o temperature equations for the iberian peninsula to these values results for the early pliocene suggest mean annual temperatures up to 2 3 c higher than today fitting pollen based estimates fairly well temperatures 5 c higher than today are predicted for the early late miocene 11 9 ma these estimations are feasible given the local occurrence of crocodilians and the presence of fruit eating hominids in iberia at that time the estimated amount of cooling since then is similar to the estimated decrease in nw europe based on plants the stable carbon isotope record indicates the virtual absence of c4 plants pointing to an environment consisting of c3 plants under slightly water stressed conditions the long term 13 c trend follows the expected decrease in average global 13 c co2 predicted from planktonic foraminifers within tooth variability is supposed to reflect seasonal change but the amplitude is expected to have been significantly damped by internal time averaging effects related to the mixing with atmospheric o 2 reservoir dynamics enamel maturation and sampling procedure the exact degree of damping is difficult to estimate but theoretical considerations suggest values between 50 and 75 depending on temporal resolution and element used c o reconstructed seasonal temperature ranges for central spain are equal or slightly less than the modern range within tooth 13 c variation is more difficult to explain as it can be attributed to multiple factors such as intra annual changes in 13 c co2 micrometeorology plant response and diet the occurrence of both positive and negative intra tooth 18 o 13 c correlations may be related to orbitally forced variations in seasonality

the stable isotopic composition of modern soil carbonate and its relationship to climate the oxygen isotopic composition of modern soil carbonate is well correlated with the isotopic composition of local meteoric water the carbon isotopic cycle for co 2 in soils can be described in terms of the proportion of biomass using the c 4 photosynthetic pathway and the co 2 respiration rate of the soil at low soil respiration rates significant atmospheric co 2 mixing can occur in general the carbon isotopic composition of soil carbonate is related to the proportion of c 4 biomass present in soil but soils that freeze to the depth of carbonate formation often have a significant atmospheric component this suggests that freezing of the soil solution should be considered as another important mechanism for soil carbonate formation because of these relationships the isotopic composition of soil carbonate may be a paleoclimatic and paleoecologic indicator in cases in which diagenetic alteration has not occurred

miocene burdigalian seawater and air temperatures estimated from the geochemistry of fossil remains from the aquitaine basin france abstract construction work of the highway a65 led the top of the burdigalian molasses de l armagnac formation to outcrop in two close localities near the town of bazas and marimbault situated on the western edge of the aquitaine basin france from this formation a rich fossil assemblage has been recovered and includes both marine and terrestrial fossil remains which offered the opportunity to reconstruct both seawater and terrestrial air temperatures at a regional scale during the burdigalian for this purpose two sets of fossil samples representative of the whole assemblage have been selected for each locality they include teeth and bones of sharks fish rays reptiles and mammals as well as tests of sea urchins and shells of bivalves first we performed rare earth element ree analyses of 53 apatite samples from both localities in order to characterize the diagenetic history of the assemblage we then analysed the oxygen isotope composition of 49 biogenic apatite phosphate samples and 6 biogenic carbonate samples representing both marine and terrestrial organisms using published isotopic fractionation equations both seawater and terrestrial air temperatures were reconstructed calculated seawater temperatures using phosphate and carbonate isotopic thermometers are 23 4 c and 25 1 c respectively for the locality of mendouillet bazas and 24 4 c and 26 1 c respectively for the locality of monbalon miron marimbault calculated terrestrial air temperatures are 18 2 c for the locality of mendouillet and 17 2 c for the locality of monbalon miron these regional temperatures are in good agreement with seawater and terrestrial temperatures calculated for other european localities of contemporaneous periods these results also fit the global climatic context of the mid miocene climatic optimum starting at the end of the burdigalian even though the global climatic conditions were warmer than today during the end of the burdigalian calculated continental and seawater thermal gradient at mid latitude appear to have been comparable to present day ones

intra tooth isotope variations in late miocene bovid enamel from afghanistan paleobiological taphonomic and climatic implications abstract the rich mid turolian site of molayan afghanistan has yielded more than 100 mandibles from the bovid tragoportax afghanicus in this study we document different aspects of the paleobiology and paleoecology of this fossil bovid by examining patterns of inter and intra tooth carbon and oxygen isotopic analyses in m1 to m3 molars from five specimens accurate paleoecological and paleoclimatic inferences based on carbon and oxygen isotope analyses in fossil enamel are directly dependent upon the way in which teeth are sampled as well as taphonomic processes which are responsible for fossil accumulation because this sampling methodology provides a unique opportunity to detect seasonal changes in diet and environment during tooth formation it also offers the possibility of testing between catastrophic and progressive deposition at this site preservation of 13c and 18o values is shown to be good and permits inter individual comparisons of isotopic trends to be made timing of molar crown formation and enamel growth rate were deduced from the pattern of intra tooth carbon and oxygen isotope variation the pattern of 18o variation found in the first and second molars is similar in all the individuals which suggests that a single birth season occurred probably before the hot dry season large differences in average 18o values 2 5 are found within a single cohort and indicate that fossil accumulation was progressive rather than catastrophic the hypothesis that t afghanicus evolved in an open environment is supported by high 13c values in a c3 context increasing temperature and or aridity eastward along the greco irano afghan biogeographic province is strongly suggested by increasing 18o values between greece and afghanistan

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

the spread of grass dominated habitats in turkey and surrounding areas during the cenozoic phytolith evidence abstract the arrival of hipparionine horses in the eastern mediterranean region around 11 ma was traditionally thought to mark the simultaneous westward expansion of savanna vegetation across eurasia however recent paleoecological reconstructions based on tooth wear carbon isotopes and functional morphology indicate that grasses played a minor role in late miocene ecosystems of the eastern mediterranean which were more likely dry woodlands or forests the scarcity of grass macrofossils and pollen in miocene floras of europe and asia minor has been used to support this interpretation based on the combined evidence it has therefore been suggested that late miocene ungulate faunal change in the eastern mediterranean signals increased aridity and landscape openness but not necessarily the development of grass dominated habitats to shed new light on the miocene evolution of eastern mediterranean ecosystems we used phytolith assemblages preserved in direct association with faunas as a proxy for paleovegetation structure grassland vs forest we extracted phytoliths and other biogenic silica from sediment samples from well known early to late miocene 20 7 ma faunal localities in greece turkey and iran in addition a middle eocene sample from turkey yielded phytoliths and served as a baseline comparison for vegetation inference phytolith analysis showed that the middle eocene assemblage consists of abundant grass phytoliths grass silica short cells interpreted as deriving from bambusoid grasses as well as diverse forest indicator phytoliths from dicotyledonous angiosperms and palms pointing to the presence of a woodland or forest with abundant bamboos in contrast the miocene assemblages are dominated by diverse silica short cells typical of pooid open habitat grasses forest indicator phytoliths are also present but are rare in the late miocene 9 7 ma assemblages our analysis of the miocene grass community composition is consistent with evidence from stable carbon isotopes from paleosols and ungulate tooth enamel showing that c4 grasses were rare in the mediterranean throughout the miocene these data indicate that relatively open habitats had become common in turkey and surrounding areas by at least the early miocene 20 ma 7 million years before hipparionine horses reached europe and arid conditions ensued as judged by faunal data

a 16 ma record of paleodiet using carbon and oxygen isotopes in fossil teeth from pakistan abstract the siwalik sequence of northern pakistan contains a 16 ma record of paleosol carbonate and fossil teeth from which a record of paleovegetation can potentially be reconstructed and compared the carbon isotopic composition of paleosol carbonate and organic matter from siwalik strata reflects a major paleoecological change on the floodplains of major rivers beginning7 3 ma ago by 6 ma c 3 dominated plant communities probably composed of mostly trees and shrubs were displaced by nearly continuous c 4 grassland we find that the carbon isotopic ratios in herbivore tooth enamel reflect this dramatic ecologic shift carbonate in enamel older than 7 ma averages 11 in 13 c pdb consistent with a largely c 3 diet enamel from the plio pieistocene averages 1 9 in 13 c similar to the value displayed by modern c 4 grazers analysis of post burial carbonate cements and the concordance with isotopic evidence from paleosols argues strongly against major isotopic alteration of the enamel while coexisting bone may have been altered early in burial this study confirms that enamel apatite is useful for paleodietary reconstruction much further back in the geologic record than was previously thought

late miocene and pliocene large land mammals and climatic changes in eurasia the fossil teeth of land mammals offer a powerful tool to map the regional details of past climate change in the terrestrial realm we use meanplant eaterhypsodonty molarcrownheight oflateneogenemammallocalitiestomaplatemioceneandpliocenepalaeoprecipitation on the eurasian continent and with higher temporal resolution in europe the results show that the mid latitude drying in eurasia affected thecentral parts ofthecontinentfirst and thatthedrying of western europeafter about7 8maseemstohavecoincidedroughlyintimewith a return to more humid conditions in eastern asia with a return to a drier east and more humid west in the pliocene within europe the hypsodonty based palaeoprecipitation maps suggest that the sequence from mn 9 to mn 12 ca 11 1 6 8 ma was dominated by an east west continental marine humidity gradient which gradually intensified and with a shift of dryer conditions eastwards in mn 12 ca 7 5ma thiswaspartlyoverlainfrommn13onwardsbyanorth southorientedgradient whichpersistedatleasttotheendofthepliocene the maps for both the earliest late miocene mn 9 ca 11 1 9 7 ma and the earliest pliocene mn 14 ca 4 9 4 2 ma show very low regional differentiation possibly suggesting perturbed phases in the evolution of the mammal communities analysis of hypsodonty and dietary structure of the mammalian plant eater community in europe during the entire interval shows that the miocene pliocene boundary was marked by a strong decrease in mesodont species and mixed feeders and an increase in brachydont species and omnivores in this view the shift in the latest miocene from east west to partly north south polarised hypsodonty patterns corresponds mainly to an increase in hypsodont species and grazers it seems probable that the east west gradient was primarily driven by precipitation while the north south gradient would also have been strongly influenced by temperature related effects of humidity

does δ13ccarb of the chinese loess indicate past c3 c4 abundance a review of research on stable carbon isotopes of the chinese loess current research on stable carbon isotopes of the chinese loess is reviewed the stable carbon isotopic composition of soil organic matter som 13corg of paleosols formed during interglacials is more positive than that within loess accumulated during glacials spatially it becomes progressively more negative from the eastern chinese loess plateau clp to the western however stable carbon isotopic composition of pedogenic carbonates 13ccarb from the same sequence produces an opposing trend both temporally and spatially and variation differs from expectations under conditions of equilibrium this indicates that 13ccarb in the chinese loess cannot be used to reconstruct the relative proportion of c3 c4 plants in past ecological communities furthermore use of 13ccarb to reconstruct the expansion of c4 plants in older tertiary red clay deposits is considered unreliable we believe 13ccarb may act as an indirect indicator of vegetation density following on changes in moisture supply controlled by the intensity of the asian summer monsoon but conclude that full understanding of the paleoclimatic significance of 13ccarb in the chinese loess and underlying tertiary red clay requires better understanding of modern isotopic processes

tide induced recirculation across the aquifer ocean interface a parametric analysis is conducted to examine the influence of tides inland hydraulic conditions and aquifer properties on the rate of tide induced seawater recirculation through the nearshore aquifer understanding such influence is crucial for accurate prediction of subsurface chemical fluxes to coastal waters via groundwater discharge the analysis is based on numerical simulations of density dependent groundwater flow in a coastal aquifer subject to tidal oscillations across a sloping beach face the results reveal that the amplitude of tidal oscillations and the inland hydraulic gradient are the primary parameters controlling the tide induced recirculation rates significant tidal exchange is expected when the ratio of tidal to inland forcing is large the horizontal tidal shoreline excursion and aquifer depth both display asymptotic behavior influencing recirculation rates for only small values where the exchange process is limited by the potential for infiltration and shallowness of the aquifer respectively the analysis also indicates that tidal effects increase density driven recirculation rates due to enhanced convective flow within the saltwater wedge

oxygen and carbon isotopic composition of quaternary meteoric carbonates from western and southern europe their role in palaoenvironmental reconstruction abstract the relationship between environmental conditions and the 18 o and 13 c values of soil and groundwater carbonates in europe is poorly understood consequently the use of the isotopic composition of these carbonate palaeoclimatic indicators in european sedimentary sequences is restricted in this study we examine the 18 o and 13 c values of soil and groundwater carbonates from western and southern europe in western europe there is no relationship between carbonate 18 o values and carbonate 13 c values the 18 o values of soil carbonate appears to be driven by temperature whilst the 13 c value of soil and groundwater carbonate reflects the persistent dominance of c 3 vegetation in this region during the quaternary the 18 o and 13 c values of soil carbonates from spain and crete show a strong degree of co variance suggesting that they are being controlled by the same environmental factor this is suggested to be aridity 18 o values are controlled by soil moisture evaporation whilst 13 c value is controlled by soil moisture degassing vegetation abundance and possible c 3 c 4 vegetation inputs the paper concludes by highlighting the fact that although currently under utilised the 18 o and 13 c values of soil and groundwater carbonates have a huge potential for providing important palaeoenvironmental information from sites across europe

correlation between isotope records in marine and continental carbon reservoirs near the palaeocene eocene boundary changes in the isotope content of the large marine carbon reservoir can force shifts in that of the smaller carbon pools in the atmosphere and on land the carbon isotope compositions of marine carbonate sediments from the late palaeocene vary considerably exhibiting a sudden decrease close to the palaeocene eocene boundary which coincides with deep sea benthic extinctions1 and with changes in ocean circulation here we report that these fluctuations in the marine carbon isotope record are closely tracked by the terrestrial records provided by palaeosol carbonates and mammalian tooth enamel in using palaeosol carbonates to reconstruct the co2 content of the ancient atmosphere2 isotope shifts of this sort will have to be taken into account the sharp decrease in 13c 12c ratios in the late palaeocene provides a datum for precise correlation of marine and continental records and suggests that abrupt climate warming at this time may have played an important role in the evolution of land mammals

stable isotopic evidence for terrestrial latitudinal climate gradients in the late miocene of the iberian peninsula abstract the late neogene of the mediterranean region is marked by significant faunal and floral turnover in terrestrial ecosystems paleogeographic and paleoceanographic changes associated with the messinian salinity crisis msc and regional climate transition associated with the onset of northern hemisphere glaciation in this paper we report stable oxygen isotope compositions 18o of terrestrial mammal faunas from the late miocene pliocene and pleistocene of spain and compare these data with late miocene mammal 18o values from northern libya since tooth enamel 18o from modern horses has been demonstrated to be a reasonable proxy for the 18o of local meteoric water which is in turn strongly dependent on mean annual temperature mat we use the 18o of fossil horse tooth enamel to estimate mat our paleotemperature reconstructions are consistent with global cooling during the late cenozoic with mat for the late miocene that is warmer than today by 1 2 c in ne spain and by 4 5 c in se spain the difference of 8 9 c between ne and se spain for the late miocene is 60 greater than the mat difference between these same areas today the 18o values from libya are lower than those for southern spain and may suggest cooler and or wetter climates in northeastern africa during the latest miocene and early pliocene we examined intrafaunal 18o patterns to make interpretations about paleoecology and to qualitatively assess paleoaridity comparisons of 18o values between clades are consistent with a semi aquatic lifestyle for anthracotheres hippopotamids and castorids we also compare intra tooth samples of enamel and dentine to examine possible diagenetic alteration of these materials comparisons of enamel and dentine 18o suggest slight diagenetic alteration of dentine but we demonstrate that these 18o values can be used to reconstruct reasonable values of diagenetic water 18o overall our data do not support large climatic changes in the iberian peninsula during the msc but are consistent with long term global cooling and sharper latitudinal climate gradients in spain during the neogene

stable isotope ecology of hippotherium from the late miocene pannonian basin system abstract the retreat of the paratethys sea in the middle to late miocene left behind a series of intermontane lakes across central europe ancient lake pannon which existed in present day hungary and surrounding countries was gradually filled in by fluvial sedimentation from 10 to 4 ma this infilling allowed for the migration of mammals such as the horse hippotherium into the pannonian basin system pbs stable carbon and oxygen isotope records from hippotherium are used here to reconstruct changing environmental conditions of the late miocene in this region our emphasis is on understanding the vegetation and surface water of the basin because these in turn affected the isotopic composition of lake pannon we analyzed the enamel of 68 hippotherium teeth from 23 localities in the pbs for carbon and oxygen isotope composition carbon isotope records indicate that hippotherium in the central regions of the basin were feeding in more open habitats than those in the northwest we find no evidence of the expansion of c4 grasses into the pbs oxygen and carbon isotope values from the vienna basin nw part of the pbs generally covary whereas those from more central regions do not the oxygen values of the central pbs are generally lower than those of the vienna basin these data suggest that the interior of the pbs was generally dry which forced hippotherium to use water sources that were not strongly evaporated such as rivers originating from outside the basin the dry interior was likely caused by a rain shadow east of the alps and north of the dinarides consequently much of the surface inflow into lake pannon would have been influenced by runoff from high elevations around or outside the basin by understanding the terrestrial environment better constraints can be placed on lake conditions in future work

the paleogeography of late neogene central crete inferred from the sedimentary record combined with albinaria land snail biogeography abstract phylogenetic and geographic relations of recent land organisms often agree with results from tectonical and paleogeographic reconstructions in the hellenic island arc greece albinaria land snails gastropoda pulmonata clausiliidae are used to provide paleogeographical information in a combined analysis of their present distributional ranges and the sedimentary record late tertiary neogene islands in the region of present day crete existed for 6 9 myear before the arc was uplifted 3 2 myear ago pliocene the albinaria fauna of crete is known to be relictual in central crete an area of 3800 km2 the distributional ranges of 15 parapatrically dispersed albinaria species were determined based on differences in their ecological behavour the species are subdivided into two groups group 1 exclusively living on pre neogene substrate is believed to have largely conserved pre pliocene ranges and group 2 partly living on neogene partly on pre neogene substrates is assumed to have occupied the land which appeared after late neogene uplift events together with the sedimentary record albinaria helps to reconstruct the dynamic paleogeographic developments and block movements in central crete since the serravallian the conclusions imply 1 that some of the involved populations have been separated from each other for up to 11 myear and 2 that providing information on paleoislands recent land snails may contribute to geoscientific questions concerning the rate and timing of uplift and erosion

paleosol organic matter and pedogenic carbonates and paleontological δ13c records applied to the paleoecology of late pleistocene holocene in mexico abstract stable isotopes of carbon 13 c in terrestrial geological materials paleosol humus and carbonates as well as fossil bones collagen and tooth enamel are established as highly specific records on paleoenvironmental characteristics it was assumed that comparing the results of different types of materials on regional or local scales provides more accurate and reliable reconstructions and even opens new aspects of interpretation this was tested by the comparison of the data obtained from the late pleistocene paleosols and or remains of pleistocene megafauna in various locations in northwestern mexico sonora paleosols formed in mis3 mis2 and mis1 central northern mexico san luis potosi teeth corresponding to mis2 and mis1 and central southern mexico puebla paleosols corresponding to mis3 and mis2 and teeth associated with these paleosols and state of mexico teeth corresponding to mis2 the results of isotopic studies are complemented with other paleoenvironmental proxies the 13 c values of paleosols of sonora is 19 8 to 16 95 in organic matter and shows little difference between paleosols and holocene soils 13 c values of pedogenic carbonates are 6 4 to 4 52 in san luis potosi the 13 c values of paleosol are 12 16 in organic matter in puebla they vary from 24 6 in paleosols to 15 16 in the modern surface soil pointing to contrasting vegetation change the 13 c values in fossils range from 10 7 to 1 2 in slp of 2 73 and 2 93 in puebla and 6 5 to 1 3 in state of mexico the 13 c values of paleosols and analysis of megafauna in northwest and central northern mexico matched each other indicating mixed c3 c4 vegetation while for central southern mexico paleosols indicated predominance of c3 plants and megafauna indicated mixed c3 c4 composition in general the results indicate that in northern mexico environmental conditions were slightly wetter than at present while for the central area there was a large change in the environmental conditions of high humidity in mis3 and mis2 with a trend to drier climates in mis1

stable carbon and oxygen isotopic evidence for late cenozoic environmental change in northern china abstract stable carbon and oxygen isotope ratios of 311 enamel samples from a diverse group of herbivorous mammals including equidae rhinocerotidae bovidae rodentia and ochotonidaewere were analyzed in order to reconstruct the late cenozoic history of vegetation and environmental change in the yushe basin in north china the 13c values of bulk and serial enamel samples from large mammals show a wide range of variation from 13 3 to 1 4 with a mean of 7 4 3 5 n 294 this indicates that large herbivorous mammals in the area had a variety of diets since 6 5 ma ranging from pure c3 to mixed c3 c4 and pure c4 diets in contrast the 13c values of small mammals vary from 11 9 to 7 6 with a mean of 9 7 1 1 n 17 indicating that rodents and ochotonids were feeding mostly on c3 plants variations in 13c values within and between species reflect the variations in the habitat and the vegetation consumed by the animals in general horses had higher amounts of c4 grasses in their diets than other contemporary taxa such as bovids rhinos rodents and deer suggesting that horses exploited more open habitats such as grasslands while deer rhinos and rodents may have preferred more c3 vegetation which is more indicative of forested environments the carbon isotope data show that c4 grasses have been an important component of horses diets and of local ecosystems since 6 5 ma confirming that the late miocene c4 expansion occurred in north china as it did in africa indian subcontinent and the americas this supports a global factor as a main driver of the late miocene c4 expansion the combined carbon and oxygen isotope data reveal major shifts in climate to drier and or warmer conditions after 5 8 4 1 3 3 and 2 5 ma and significant shifts to relatively wetter and or cooler conditions after 6 4 5 3 5 ma the shifts to drier and or warmer climate after 5 8 ma and 2 5 ma coincide with two major fauna turnover events intra tooth 13c and 18o values are negatively correlated within individual modern teeth and some fossil teeth displaying the characteristic pattern of the summer monsoon regime and confirming a strong monsoon influence in the area since at least the early pliocene the data also suggest that the c4 abundance in the area has fluctuated over the past 6 5 ma in response to changes in climate with more c4 grasses during warmer and or drier periods and a reduced c4 component at cooler and or wetter times

expansion of c4 grasses in the late miocene of northern pakistan evidence from stable isotopes in paleosols stable isotopic clay mineralogic and bulk chemical analyses were conducted on paleosols of the neogene siwalik sections in northern pakistan in order to reconstruct floodplain environments over the past 17 ma the stable carbon isotopic composition of soil carbonate mean 13c pdb 10 2 and associated organic matter mean 13c pdb 24 1 in paleosols representing 17 7 3 ma reveal that floodplain vegetation was dominated by c3 plants at 7 3 ma a shift toward more positive carbon isotopic values began signaling the gradual expansion of c4 grasses onto the floodplain from 6 ma to present carbon isotopic values for paleosol carbonate mean 13c pdb 0 6 and organic matter mean 13c pdb 14 4 are uniformly enriched in 13c indicating the presence of nearly pure c4 grassland the scarcity of kaolinite and abundance of smectite and pedogenic carbonate in most paleosols suggest that rainfall in the region remained 1 0 1 25 m yr or less for the entire 17 ma of record paleosols in the lower portion of the section lack organic a horizons but have reddish b horizons often containing secondary iron oxide nodules leaching depths of soil carbonate in these older paleosols are typically greater than those in the plio pleistocene part of the section where organic a horizons are common and b horizons are markedly more yellow the combined evidence suggests that the mature paleosols in the pre 7 3 ma part of the record are dominantly calcareous alfisols or mollisols that once underlay nearly pure c3 vegetation perhaps trees and shrubs while calcareous mollisols underlying c4 grassland dominate the upper part of the record the carbon and oxygen isotopic trends in the paleosol record in pakistan are also evident in the diet of fossil mammals and in paleosols from nepal thus demonstrating that these paleoenvironmental changes in floodplain vegetation may be continent wide local effects such as the development or intensification of the asian monsoon driven by uplift of the tibetan plateau may have led to the expansion of c4 grasses if however the expansion of c4 grasses proves globally synchronous then a larger scale cause such as a marked decrease in co2 may be the driving mechanism

on the origin of upper miocene sapropelites a case study from the faneromeni section crete greece for the first time results of an integrated geochemical and micropalaeontological study of upper miocene sapropelites in a land based section in the mediterranean are presented three sapropelites and adjacent homogeneous intervals in the cretan faneromeni section have been investigated in detail the chemical and foraminiferal characteristics were found to be markedly similar to those of plio pleistocene sapropelites as the physiography and climate of the late miocene mediterranean were not fundamentally different from those of today our preferred model for late miocene sapropelite formation is similar to the one recently developed for plio pleistocene sapropelites increased seasonality and freshwater input during northern hemisphere summer insolation maxima triggered high export production and oxygen consumption rates which in combination with a concomitant decrease in deep water formation rate resulted in the observed high organic matter content of the sapropelites

the pikermian event temporal and spatial resolution of the turolian large mammal fauna in se europe abstract during the turolian late miocene the eastern mediterranean region is considered to have been part of a single major ecological area supporting a particular savanna type large mammal community referred to as the pikermian biome analysis of the timing turnover patterns biogeographic relations and palaeoecological profile of the turolian large mammal faunas from either sides of the aegean sea failed however to confirm the presence of a homogeneous mammal community isotropically behaving through time for most of the turolian the large mammal assemblages from southern balkans and anatolia appear to have existed under different environmental conditions partly isolated by natural barriers overall climatic changes and regional physico geographic factors around 7 2 my allowed the southern balkan biogeographic region to be temporarily part of the sub paratethyan bioprovince as a result significant faunal reorganizations and interchanges triggered the emergence and expansion of the pikermian mammal fauna which collapsed soon after 7 0 my as a consequence of the early messinian global changes the pikermian large mammal event seems to follow known procedures related with contemporaneous marine and land faunal episodes across the mediterranean

quantitative paleoenvironmental and paleoclimatic reconstruction using paleosols abstract paleosols fossil soils are preserved throughout the geologic record in depositional settings ranging from alluvial systems to between basalt flows until recently paleosols were studied using primarily qualitative methods in recent years paleopedology has shifted from a largely qualitative field based on comparisons with modern analogues to an increasingly quantitative endeavor some of this change has been a result of applying existing techniques to new materials but many of the innovations have been the result of applying new techniques to new materials including thermodynamic modeling of soil formation isotope geochemistry and applications of empirical relationships derived from modern soils a variety of semi quantitative and quantitative tools has been developed to examine past weathering and pedogenesis and to reconstruct both paleoenvironmental and paleoclimatic conditions at the time that the paleosols formed though it is often not possible to achieve the same temporal resolution as with marine records for paleoclimatic reconstructions proxies based on paleosols are potentially a much more direct means of making paleoclimatic reconstructions because soils form at the earth s surface in direct contact with the atmospheric and climatic conditions at the time of their formation paleoclimatic and environmental properties that may be reconstructed using the new proxies include provenance weathering intensity mean annual precipitation and temperature during pedogenesis nutrient fluxes into and out of the paleosols the atmospheric composition of important gases including co2 and o2 the moisture balance during pedogenesis the soil gas composition reconstructed vegetative covering and paleo altitude

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

geographic and temporal patterns in the late neogene 12 3 ma aridification of europe the use of small mammals as paleoprecipitation proxies abstract present day relations between small mammal community structure and rainfall are used to predict late neogene 12 3 ma precipitation patterns in europe and anatolia new proxy methods are developed which include regressions of mean annual and minimum monthly precipitation on diet invertivory index and locomotion habitat arboreality index a series of precipitation maps and a set of regional precipitation curves through time at 1 myr resolution are presented precipitation curves at a higher temporal resolution are constructed for the region of central spain the miocene results show the existence between 12 and 9 ma of a large wet 800 1200 mm yr zone extending from northern spain to the ukraine and characterized by the whole year penetration of large amounts of moisture far into the continent between 10 9 and 5 ma this european temperate wet zone etwz shrinks and or moves northward resulting in diachronous aridification a coeval northward migration of the subtropical high pressure zone shpz is hypothesized which is also consistent with the predicted onset of seasonal summer dryness between 10 and 8 ma the maximum extension of the etwz at 12 9 ma temporally correlates with northern hemisphere cooling suggesting that climate zonation rather than the global amount of atmospheric moisture controlled european climate at this time the main aridification at 9 8 ma could best be explained by a northward extension shifting of the subtropical high pressure zone and a transition towards less zonal circulation processes which ultimately could have been triggered by uplift of the tibetan plateau a temporary increase of precipitation at 7 6 ma is associated with renewed global cooling the lowest precipitation values less than 400 mm yr occur during the pliocene in southern and eastern europe uplift in eastern europe carpathians shrinking of the paratethys could well explain the aridification in this area and the associated sharpening of east west precipitation gradients across the continent

pedogenic carbonates in texas stable isotope distributions and their implications for reconstructing region wide paleoenvironments abstract pedogenic carbonates are ubiquitous in paleosols through geologic history and have been widely used to speculate on paleoclimatic conditions during their formation they are widespread and well developed in large areas of texas a majority are of late quaternary age and have formed across a range of climatic conditions on various types of substrates to evaluate the usefulness of pedogenic carbonates as environmental indicators this study investigates regional scale trends in stable isotope compositions of pedogenic carbonates across approximately 900 km of texas the 13c values of 49 pedogenic carbonate profiles 182 analyses on various host strata e g limestone igneous rocks range from 10 6 to 0 7 v pdb most 13c values are evenly distributed between 9 and 1 and the 18o values range from 9 1 to 0 2 v pdb mainly between 6 and 2 there is no correlation between carbon and oxygen isotopic values r2 0 0002 pedogenic carbonates in the texas gulf coastal plains southern high plains and west texas exhibit higher 13c values than those in south and central texas which corresponds to the spatial change in vegetation between c4 dominated and c3 dominated plants the marked increase in 13c values of the pedogenic carbonates from the tertiary strata into the overlying quaternary strata confirms the invasion of a c4 biomass into the southern high plains since the early pliocene from east to west the 18o values of late quaternary pedogenic carbonates decrease gradually a trend that mimics the spatial variation of 18o values of modern meteoric water primarily due to the increased distance from the gulf of mexico source of most of the meteoric water in contrast to the regional trends the stable isotope values of some pedogenic carbonates developed on marine limestone and calcareous alluvium in central texas and south texas have isotopic signatures inherited from the host strata in addition some of the 13c values of pedogenic carbonate nodules in the gulf coastal plains have been affected by saline groundwater soil carbonates formed in the shallow parts of the profile such as petrocalcic horizons may have also been influenced by the atmospheric co2 nevertheless climatic trends are readily apparent in the isotopic data thus demonstrating their potential value in region wide paleoclimatic analyses

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

stable isotopic studies of palaeosol sediment from upper siwalik of himachal himalaya evidence for high monsoonal intensity during late miocene abstract palaeosols from sedimentary section exposed 2800 m at haripur kolar on somb river in himachal himalaya were studied for stable isotopes of carbon oxygen and hydrogen along with sr isotopic ratios stable isotopic studies of middle and upper siwalik sections from pakistan and nepal region have been used for inferring the palaeoclimate of the region during early and late miocene time the aim of our work was to extend this type of study to himachal himalaya india carbon isotopes in palaeosol carbonate nodule and associated organic matter indicate an abrupt transient of c3 vegetation dominance around 4 ma this transient disrupted the general trend of c4 ecological dominance observed from about 8 to 4 ma in this region of asian subcontinent we attribute this observation with the higher monsoonal intensity which also is supported by different archives from the region g bulloides abundance from dsdp core from the arabian sea and grass pollens abundances on land we propose that greater moisture availability around 4 ma due to higher monsoonal activity caused an abrupt transient of c3 dominance in this region the proposition is further supported by our data on 18o of carbonates and d of clay showing depletion around 4 ma observed high 87sr 86sr ratios in carbonates around the same time period suggest increased weathering and in turn higher rainfall activity

multiproxy reconstruction of the palaeoclimate and palaeoenvironment of the middle miocene somosaguas site madrid spain using herbivore dental enamel profound palaeoclimatic changes took place during the middle miocene the miocene climatic optimum 20 to 14 13 5 ma was followed by a sudden 200 ka decrease in temperature and an increase in aridity around the world as a consequence of the reestablishment of the ice cap in antarctica somosaguas palaeontological site madrid basin spain has provided a rich record of mammal remains coincident with this global event middle miocene biozone e 14 1 13 8 ma it contains four fossiliferous levels t1 t3 1 t3 2 and t3 3 with t1 being the oldest that span an estimated time of 105 125 ka scanning electron microscope sem and rare earth element ree analyses performed on herbivore tooth enamel gomphotherium angustidens anchitherium cf a cursor conohyus simorrensis prosantorhinus douvillei and ruminants indicate that diagenetic processes have not been intense enough as to obscure the original geochemical signal stable isotope 18oco3 13cco3 and 18opo4 analyses have been measured on the herbivore tooth enamel across these levels with the aim of determining to what extent the global cooling and aridity pattern is recorded at this site a decrease in 18oco3 and 18opo4 has been detected from t1 to t3 3 and t3 1 to t3 3 respectively indicating a progressive drop of about 6 c from around 18 c to 12 c in mean annual temperatures within t3 tooth enamel 13c values experience an increase from t3 1 to t3 3 suggesting an increase in aridity ba ca analyses have also been performed on the tooth enamel in order to detect changes in the palaeoecology of the studied taxa this ratio allows the establishment of particular feeding patterns such as a more browsing habit in the case of gomphotherium angustidens compared to anchitherium cf a cursor as suggested by higher ba ca values in the latter trace elements do not support any significant change across the succession in the dietary behaviour of the species analyzed despite the stable isotopes evidence of an important palaeoclimatic shift from t1 to t3 3

seven ambiguities in the mediterranean palaeoenvironmental narrative abstract a review of seven outstanding issues on mediterranean palaeoenvironments is presented these are related to the dominant orbital pacing of climate variability the length of the interglacial vegetation succession the influence of the african summer monsoon the seasonality of precipitation during boreal insolation maxima the moisture balance during glacial maxima and the appearance of the mediterranean type climate rhythm and evolution of mediterranean sclerophyllous plants what emerges is that 1 marine 18oplanktonic and sst records show that precession has been a fundamental tempo of mediterranean climate change representing both a low latitude signal runoff from north africa and the direct influence of insolation at mediterranean latitudes but high latitude glacial effects 41 kyr and 100 kyr cycles became superimposed after 2 8 ma sapropel and dust deposition patterns in marine cores reveal that obliquity also has an effect on mediterranean climate through dry wet oscillations which are independent of glacial interglacial variability 2 the temperate part of interglacial vegetation succession has a duration of approximately half a precession cycle this persisted during the interval of obliquity dominated glacial cycles 2 8 1 ma with distinct forest successions following the precessional cycles however these are not always separated by an open vegetation phase because of minimal ice growth producing an impression of a prolonged interglacial forest interval 3 the effect of an enhanced african monsoon during summer insolation maxima has been mainly indirect in terms of nile discharge and runoff along the north african coast leading to increased freshwater input into the mediterranean sea reduced deep water ventilation and sapropel deposition 4 the notion of an accentuated summer rain regime in the northern mediterranean borderlands also contributing to a freshening of the mediterranean sea during boreal insolation maxima is not supported by the available evidence which suggests increased summer aridity 5 recent improvements in chronological precision and data resolution point to an increase in aridity and decreased temperatures during the last glacial maximum 21 2 ka but suggest an increase in effective moisture during the immediately preceding interval of 24 27 ka 6 the mediterranean type climate is not exclusively a post 3 6 ma phenomenon but may have appeared intermittently during the course of the tertiary or before 7 if that is the case then the paradigm that the sclerophyllous evergreen habit represents a pre adaptation to summer drought may need re evaluation

changes in carbon isotope ratios in the late permian recorded in therapsid tooth apatite the end of the permian witnessed global extinctions of marine and terrestrial fauna1 as marine biogenic carbonate and atmospheric carbon dioxide are in long term isotopic equilibrium changes in carbon isotope ratios in marine carbonate strata should record changes that occurred at that time in atmospheric ratios one might then expect a correlation between 13c 12c ratios in such marine sequences and those in terrestrial records that derive from carbon bearing materials that incorporate atmospheric co2 an example of the latter is fossil tooth apatite from herbivorous fauna correlations of this sort between marine and terrestrial records are however difficult to establish as they rely on particular characteristics of the isotope curves here we show that stable carbon isotope ratios in tooth apatite from diictodon a mammal like reptile in the late permian lower beaufort succession of the south african karoo 260 245 myr show a progressive depletion in 13c that is very similar to trends in marine carbonates from late permian deposits in eurasia2 7 these results suggest that global changes in total biomass occurred towards the end of the permian primary production decreased and continental aridity increased8 leading to a depletion of 13c in atmospheric and oceanic co2

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

identifying evidence for past mining and metallurgy from a record of metal contamination preserved in an ombrotrophic mire near leadhills sw scotland uk this study presents a new 3600 year record of past metal contamination from a bog located close to the leadhills and wanlockhead orefield of southwest scotland a peat core collected from toddle moss was radiocarbon 14c dated and analysed for trace metal concentrations by emma and lead isotopes by icp ms to reconstruct the atmospheric deposition history of trace metal contamination in particular lead the results show good agreement with documented historical and archaeological records of mining and metallurgy in the region the peak in metal mining during the 18th century the decline of lead mining during the anglo scottish war and lead smelting during the early medieval period there may also have been earlier workings during the late bronze and iron ages indicated by slight increases in lead concentrations the pb ti ratio and a shift in 206pb 207pb ratios which compare favourably to the signatures of a galena ore from leadhills and wanlockhead in contrast to other records across europe no sizeable lead enrichment was recorded during the roman iron age suggesting that the orefield was not a significant part of the roman lead extraction industry in britain these findings add to the various strands of archaeological evidence that hint at an early lead extraction and metallurgical industry based in southern scotland the results also provide further evidence for specific regional variations in the evolution of mining and metallurgy and an associated contamination signal during prehistoric and roman times across europe

palustrine carbonates and pedogenic calcretes in the cal basin of sw anatolia implications for the plio pleistocene regional climatic pattern in the eastern mediterranean abstract sedimentologic and stable isotopic studies in the cal basin fill provide new insights on the late neogene quaternary climatic pattern in the eastern mediterranean long term subsidence and terrestrial sedimentation in the basin beginning in the late miocene are recorded in alluvial fan and fluvial deposits overlain by pliocene palustrine carbonates an erosional unconformity separates the pleistocene siliciclastic and calcrete deposits above as a single sedimentary unit resting on top of floodplain fines and restricted to the basin center the stable isotopic analysis of the palustrine carbonates and pedogenic calcretes displays a wide range of values 7 98

palaeoclimate and palaeoenvironmental responses in the western mediterranean over the last 140 ka evidence from mallorca spain climatic change in the western mediterranean basin over the last 140 ka has been investigated from sediment and soil sequences along the coast of the northeastern part of mallorca spain palaeoclimate and palaeoenvironments are reconstructed from sediment and soil structures marine and terrestrial molluscan fauna grain size distributions mineral magnetics sediment and soil chemistry sem and oxygen isotope values dating is by osl and amino acid geochronometry along with marine molluscan faunal assemblages all oxygen isotope stages and substages from ois 6 to 1 are recorded mean annual temperatures m a t of c 19 2 c for the climatic optimum of the last interglacial compare with c 17 3 c for the present and are associated with high sea level extensive woodland and stable soils although wide temperature ranges are detected during this stage with values as low as c 10 3 c through ois 5d to 5a m a t fluctuated from 8 2 c to 17 9 c low sea level open vegetation effective river activity and aeolian sand and dust deposition characterize 5d and 5b while relatively high sea level and soil development on stable landscapes dominate ois 5c and 5a ois 4 is represented by m a t of c 4 9 c with aeolian sand and loess deposition limited river activity and weak soil development loess deposition persisted into ois 3 but at this time the m a t was c 13 c and with higher humidity and vegetation growth during the lgm ois 2 m a t was c 8 1 c and effective river slope and aeolian processes along with associated with limited vegetation cover were responsible for the most extensive changes in the landscape major rates of change occur during periods of climatic deterioration when the high levels of geomorphic energy were imposed on a landscape undergoing a breakdown of vegetation cover

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

the impact of neogene grassland expansion and aridification on the isotopic composition of continental precipitation the late cenozoic was a time of global cooling increased aridity and expansion of grasslands in the last two decades numerous records of oxygen isotopes have been collected to assess plant ecological changes understand terrestrial paleoclimate and to determine the surface history of mountain belts the 18o values of these records in general increase from the mid miocene to the recent we suggest that these records record an increase in aridity and expansion of grasslands in midlatitude continental regions we use a nondimensional isotopic vapor transport model coupled with a soil water isotope model to evaluate the role of vapor recycling and transpiration by different plant functional types this analysis shows that increased vapor recycling associated with grassland expansion along with biomechanistic changes in transpiration by grasses themselves conspires to lower the horizontal gradient in the 18o of atmospheric vapor as an air mass moves into continental interiors the resulting signal at a given inland site is an increase in 18o of precipitation with the expansion of grasslands and increasing aridity matching the general observed trend in terrestrial cenozoic 18o records there are limits to the isotopic effect that are induced by vapor recycling which we refer to here as a hydrostat in the modern climate this hydrostatic limit occurs at approximately the boundary between forest and grassland ecosystems