outgassed water on mars constraints from melt inclusions in snc meteorites the snc shergottite nakhlite chassignite meteorites thought to be igneous rocks from mars contain melt inclusions trapped at depth in early formed crystals determination of the pre eruptive water contents of snc parental magmas from calculations of the solidification histories of these amphibole bearing inclusions indicates that martian magmas commonly contained 1 4 percent water by weight when combined with an estimate of the volume of igneous materials on mars this information suggests that the total amount of water outgassed since 3 9 billion years ago corresponds to global depths on the order of 200 meters this value is significantly higher than previous geochemical estimates but lower than estimates based on erosion by floods these results imply a wetter mars interior than has been previously thought and support suggestions of significant outgassing before formation of a stable crust or heterogeneous accretion of a veneer of cometary matter

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

hydrous melting of the martian mantle produced both depleted and enriched shergottites the search for water in our solar system is one of the primary driving forces for planetary science and exploration because water plays an important role in many geologic processes and is required for biologic processes as we currently understand them excluding earth mars is the most promising destination in the inner solar system to find water as it is undoubtedly responsible for shaping many geomorphologic features observed on the present day martian surface however the water content of the martian interior is currently unresolved much of our information about the martian interior comes from studies of the basaltic martian meteorites shergottites in this study we examined the water contents of magmatic apatites from a geochemically enriched shergottite the shergotty meteorite and a geochemically depleted shergottite the queen alexandria range 94201 meteorite from these data we determined that there was little difference in water contents between the geochemically depleted and enriched shergottite magmas the water contents of the apatite imply that shergottite parent magmas contained 730 2870 ppm h 2 o prior to degassing furthermore the martian mantle contains 73 290 ppm h 2 o and underwent hydrous melting as recently as 327 ma in the absence of plate tectonics the presence of water in the interior of mars requires planetary differentiation under hydrous conditions this is the first evidence of significant hydrogen storage in a planetary interior at the time of core formation and this process could support elevated h abundances in the interiors of other terrestrial bodies like the moon mercury venus large differentiated asteroids and earth

maskelynite hosted apatite in the chassigny meteorite insights into late stage magmatic volatile evolution in martian magmas apatite hosting maskelynite and alkali maskelynite within regions interstitial to cumulus olivine differ compositionally from that found within melt inclusions in the chassigny martian meteorite feldspar glass compositions within the interstitial regions evolve along a high temperature crystallization path within the melt inclusions feldspar glass shows evolution to low temperatures extending into the subsolidus regime coupled with these differences in maskelynite compositions are differences in volatile abundance in apatite included within the maskelynite apatite found within the large olivine hosted polyphase melt inclusions is uniformly fluorapatite whereas that interstitial to cumulus olivine is chlor fluorapatite we propose that the differences in maskelynite and apatite compositions within the melt inclusion and interstitial regions arose primarily from different crystallization conditions melt inclusion maskelynite and apatite are consistent with nearly closed system buildup of magmatic volatiles during crystallization within the melt inclusions exsolution of a cl bearing fluid phase and retention of this fluid phase within the melt inclusions into the hydrothermal regime for the interstitial regions however the higher solidus temperatures of the interstitial melts the early crystallization of feldspar with significant ternary component and the cl rich nature of the apatite all suggest open system fluid migration through the cumulus pile ingress of cl rich h2o poor brine from a hotter less evolved portion of the magma plumbing system and interaction of this cl rich fluid with melt prior to the crystallization of feldspar such processes of fluid migration through a cumulus pile have been suggested on earth in layered intrusions and apatite is the primary recorder of this process

light lithophile elements in martian basalts evaluating the evidence for magmatic water degassing whether water has played a role in the petrogenesis of martian basalts remains a subject of significant debate estimates of pre eruptive water concentrations in martian magmas are impeded by the effects of degassing and shock however zoning trends of light lithophile elements lle in pyroxene have been interpreted as evidence for the degassing of magmatic water on the basis of the soluble behavior of these elements in hydrothermal fluids we provide ion microprobe analyses of lle in pyroxene in the zagami and shergotty martian basalts complemented by detailed electron microprobe analyses and major element x ray maps to independently verify the zoning of lle and its relationship to texture and major element variations our results corroborate previous results specifically that li concentrations are lower in rims than cores of shergotty and zagami pyroxene in contrast we see no evidence for a core to rim decrease in b in the absence of further data we interpret the decrease in li as reflecting either loss after crystallization of pyroxene cores consistent with magmatic degassing or the diffusive preferential loss of li from pyroxene rims possibly as a result of shock because the partitioning behavior of li between hydrous fluid minerals and melt under relevant conditions of pressure temperature and melt composition is unknown the viability of the water degassing hypothesis depends on experiments establishing the compatibility of li in hydrous fluid associated with martian basaltic melt and the incompatibility of li in pyroxene at elevated pressures

pedogenic carbonates forms and formation processes abstract soils comprise the largest terrestrial carbon c pool containing both organic and inorganic c soil inorganic carbon sic was frequently disregarded because 1 it is partly heritage from soil parent material 2 it undergoes slow formation processes and 3 has very slow exchange with atmospheric co2 the global importance of sic however is reflected by the fact that sic links the long term geological c cycle with the fast biotic c cycle and this linkage is ongoing in soils furthermore the importance of sic is at least as high as that of soil organic carbon soc especially in semiarid and arid climates where sic comprises the largest c pool considering the origin formation processes and morphology carbonates in soils are categorized into three groups geogenic carbonates gc biogenic carbonates bc and pedogenic carbonates pc in this review we summarize the available data and theories on forms and formation processes of pc and relate them to environmental factors after describing the general formation principles of pc we present the specific forms and formation processes for pc features and the possibilities to use them to reconstruct soil forming factors and processes the following pc are described in detail earthworm biospheroliths rhizoliths and calcified roots hypocoatings nodules clast coatings calcretes and laminar caps the second part of the review focuses on the isotopic composition of pc 13c 14c and 18o as well as clumped 13c and 18o isotopes known as 47 the isotopic signature of pc enables reconstructing the formation environment the dominating vegetation 13c temperature 18o and 47 and the age of pc formation 14c the uncertainties in reconstructional and dating studies due to pc recrystallization after formation are discussed and simple approaches to consider recrystallization are summarized finally we suggest the most important future research directions on pc including the anthropogenic effects of fertilization and soil management in conclusion pc are an important part of sic that reflect the time periods and formation processes in soils a mechanistic understanding of pc formation is a prerequisite to predict terrestrial c stocks and changes in the global c cycle and to link the long term geological with short term biological c cycles

holocene vegetation and climate of the alashan plateau nw china reconstructed from pollen data a set of 55 recent pollen spectra from the alashan plateau and the qilian mountains qilianshan northwestern china has been analyzed the established relationships between the pollen spectra and modern vegetation and precipitation patterns of the studied area have been applied to 65 fossil pollen spectra from a 825 cm long sediment record collected in the topographic depression formerly occupied by eastern juyan palaeolake 41 89 n 101 85 e 892 m a s l several qualitative approaches e g indicator plant species artemisia chenopodiaceae and ephedra fragilis type s l ephedra distachya type pollen ratios and quantitative methods of vegetation and climate reconstruction have been tested with the surface pollen and then applied to the eastern juyan pollen record fossil pollen data reveal pronounced environmental changes in the studied area of the alashan plateau between ca 10 700 and 1700 cal yr b p desert taxa as chenopodiaceae nitraria calligonum reaumuria were abundant in the vegetation cover around the study site through the whole record pollen spectra dated to ca 10 700 5400 cal yr b p are characterised by highest values of chenopodiaceae e fragilis type and other desert indicating taxa suggesting rather dry climate most favourable conditions are reconstructed between 5400 and 3900 cal year b p on the basis of relative increase in abundance of artemisia pollen a return to dry conditions occurred at about 3900 cal yr b p the lake finally desiccated after 1700 cal yr b p reconstructed dry climate oscillations between 5900 and 5400 and 3100 cal yr b p correlate well with similar events found in the published records from northern and western china and central mongolia however eastern juyan record does not show the early holocene humidity maximum as suggested by the sedimentary data from monsoon influenced areas of china

holocene climate variations from zhuyeze terminal lake records in east asian monsoon margin in arid northern china zhuyeze palaeolake is a terminal lake situated in the arid northern china in the east asian monsoon margin in order to examine the holocene palaeoclimatic change in the east asian monsoon margin qingtu lake section qtl from zhuyeze palaeolake is sampled in high resolution palaeoclimatic proxies such as grain size carbonate toc c n and delta 13 c of organic matter were analyzed eleven 14 c samples and six optically stimulated luminescence osl samples were dated to provide chronological control we also investigated the geomorphic features of lake shorelines in this area the results show that the climate was warm and dry in early holocene 9 5 7 0 cal ka bp cool and humid in mid holocene 7 0 4 8 cal ka bp and increasingly drier in late holocene since 4 8 cal ka bp comparisons of our records with other records in adjacent areas as well as with the records in the asian monsoon areas suggested that changes in effective moisture was synchronous in east asian monsoon marginal zone i e the pattern of dry early holocene humid mid holocene and aridity increasing late holocene and that the moisture optimum during the holocene was out of phase between asian monsoon margin and asian monsoonal dominated region possibly due to the high temperature at that time c 2010 university of washington published by elsevier inc all rights reserved zhuyeze palaeolake is a terminal lake situated in the arid northern china in the east asian monsoon margin in order to examine the holocene palaeoclimatic change in the east asian monsoon margin qingtu lake section qtl from zhuyeze palaeolake is sampled in high resolution palaeoclimatic proxies such as grain size carbonate toc c n and delta 13 c of organic matter were analyzed eleven 14 c samples and six optically stimulated luminescence osl samples were dated to provide chronological control we also investigated the geomorphic features of lake shorelines in this area the results show that the climate was warm and dry in early holocene 9 5 7 0 cal ka bp cool and humid in mid holocene 7 0 4 8 cal ka bp and increasingly drier in late holocene since 4 8 cal ka bp comparisons of our records with other records in adjacent areas as well as with the records in the asian monsoon areas suggested that changes in effective moisture was synchronous in east asian monsoon marginal zone i e the pattern of dry early holocene humid mid holocene and aridity increasing late holocene and that the moisture optimum during the holocene was out of phase between asian monsoon margin and asian monsoonal dominated region possibly due to the high temperature at that time c 2010 university of washington published by elsevier inc all rights reserved

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

lunar apatite with terrestrial volatile abundances the moon is thought to be depleted relative to the earth in volatile elements such as h cl and the alkalis nevertheless evidence for lunar explosive volcanism has been used to infer that some lunar magmas exsolved a co rich and co 2 rich vapour phase before or during eruption although there is also evidence for other volatile species on glass spherules until recently there had been no unambiguous reports of indigenous h in lunar rocks here we report quantitative ion microprobe measurements of late stage apatite from lunar basalt 14053 that document concentrations of h cl and s that are indistinguishable from apatites in common terrestrial igneous rocks these volatile contents could reflect post magmatic metamorphic volatile addition or growth from a late stage interstitial sulphide saturated melt that contained 1 600 parts per million h 2o and 3 500 parts per million cl both metamorphic and igneous models of apatite formation suggest a volatile inventory for at least some lunar materials that is similar to comparable terrestrial materials one possible implication is that portions of the lunar mantle or crust are more volatile rich than previously thought

amount effect recorded in oxygen isotopes of late glacial horse equus and bison bison teeth from the sonoran and chihuahuan deserts southwestern united states stable oxygen isotopes from fossils both vertebrate and invertebrate or inorganic sedimentary minerals frequently have been used to make interpretations about ancient global climates oxygen isotope values measured from terrestrial vertebrates or sedimentary carbonates provide information about paleotemperature and amounts of precipitation at a particular site in general these inferences are made on the centennial to millennial scale serial i e ontogenetic sampling of equus and bison tooth enamel provides climatic data on the scale of months to a few years we present models showing how annual environmental patterns of d 18 o would be replicated in the tooth enamel of equus and bison changes in d 18 o due to shifts in temperature in terrestrial environments d 18 o increases with increased temperature and amount and timing of precipitation increased precipitation may result in a decrease in d 18 o a phenomenon called the amount effect are archived in both equus and bison teeth the input signal is better resolved in bison due to its more rapid enamel growth modeled patterns are compared with actual data from modern sites in the sonoran and chihuahuan deserts of the southwestern united states the isotopic patterns from modern teeth agree with that predicted from known variations in meteoric water known floral and faunal assemblages as well as computer models suggest summer rain for the chihuahuan desert of late glacial time 15 000 10 000 years ago but little summer rain for the sonoran desert at that same time serial data from fossil teeth show a clear pattern interpreted to represent the amount effect that includes increased summer rains in the chihuahuan desert and only minor summer rains in the sonoran desert d 2004 elsevier b v all rights reserved

morphological characters and multi element isotopic signatures of carbonates from chinese loess paleosol sequences abstract morphological characters and multi element isotopic compositions of carbonates from the loess paleosol sequences in northwestern china are examined to explore the origin of the minerals samples are collected from various sections ranging from holocene to 0 9 ma within the sequences and fractions with grain sizes 45 and 45 m exhibit an almost perfect spherical shape while those 13 c and 18 o values between minerals and biologically originated samples indicates that the 206 pb 204 pb 207 pb 204 pb 208 pb 204 pb and 87 sr 86 sr these results suggest the utility of fine carbonate particles in the soil profile in reconstructing a potentially higher resolution 13 c and 18 o time series to elucidate the paleoclimatic fluctuation in the chinese loess plateau during pleistocene the discovery of the nano rod calcite in chinese loess together with previous findings of the similar mineral form in asian dust strongly suggests the possibility that these highly reactive caco 3 form may alter the aerosol properties during transport

younger dryas event recorded by the mirabilite deposition in huahai lake hexi corridor nw china abstract deposits from the huahai ancient lake in the hexi corridor were dated using conventional and ams 14c a 2500a carbon storage effect was defined at 9 25 m depth according to the 14c age difference between a plant macrofragment and detrital organic matter from the same layer the chronology of this strata indicated that the mirabilite layer at the depth of 8 05 m 9 15 m had formed during the younger dryas yd event the formation of the mirabilite layer indicated that the mean annual temperature in the hexi corridor dropped by 11 c during the yd event compared with today the lowest cold event occurred early in the yd which is consistent with what has been revealed by other high resolution records such as those of arctic ice cores and stalagmites in mid latitude regions

reconstructing palaeoenvironments on desert margins new perspectives from eurasian loess and australian dry lake shorelines abstract desert margins preserve evidence of more extensive arid conditions in the past and represent global hot spots with respect to climate change the balance of scientific evidence now suggests that dryland landscape reactivation did not correspond simply to ice age aridity peaks as previously assumed this paper provides a new perspective on and more nuanced understanding of desert marginal landscapes as palaeoenvironmental archives the two case studies represent ends of a sediment availability spectrum both environments experience substantial spatial and temporal variability in deposition with implications for reconstructing past environments at individual sites recently generated chronostratigraphic data from the dry subhumid dobrogea loess romania are synthesised to provide quantitative insights into the spatial and temporal organisation of loess plateaux loess accumulation peaks during the lgm and mis4 but not at all sites accumulation rates vary substantially between sites comparison of geographical context yields no clear driving mechanism for this variability secondly two transverse lunette dunes in semi arid willandra lakes australia yield comparable chronostratigraphies and distribution of stratigraphic units a first attempt is made to identify changes in wind regime through time on the australian desert margins and suggests that high latitude climate forcing may have acted upon semi arid australia over millennial scales the novel perspectives generated from the new datasets provide unprecedented insights into past climate circulation and land surface processes along desert margins these new perspectives coupled with the new geochronological and quantitative palaeoclimate proxy tools now available represent the next frontier for palaeoenvironmental research on desert margins

submarine hot springs and the origin of life the discovery of hydrothermal vents at oceanic ridge crests and the appreciation of their importance in the element balance of the oceans is one of the main recent advances in marine geochemistry1 it is likely that vents were present in the oceans of the primitive earth because the process of hydrothermal circulation probably began early in the earth s history2 here we examine the popular hypothesis3 7 that life arose in these vents this proposal however is based on a number of misunderstandings concerning the organic chemistry involved an example is the suggestion that organic compounds were destroyed on the surface of the early earth by the impact of asteroids and comets but at the same time assuming that organic syntheses can occur in hydrothermal vents7 the high temperatures in the vents would not allow synthesis of organic compounds but would decompose them unless the exposure time at vent temperatures was short8 11 even if the essential organic molecules were available in the hot hydrothermal waters the subsequent steps of polymerization and the conversion of these polymers into the first organisms would not occur as the vent waters were quenched to the colder temperatures of the primitive oceans

chassigny petrogenesis melt compositions intensive parameters and water contents of martian magmas abstract the snc meteorites are a class of eight basaltic achondrites that have extremely young crystallization ages 1 3 ga chassigny a unique snc meteorite is a dunite containing fo68 olivines and rare poikilitic ca pyroxenes it is one of the most primitive snc meteorites and thus is most likely to reveal information about the snc basalt source region this study presents a detailed examination of partially crystallized melt inclusions in cumulus olivine grains in chassigny these trapped melts are argued to be representative samples of the melt that existed when chassigny crystallized this melt has been modified however by interaction with the host olivine and by closed system crystallization the phases inside the melt inclusions include hydrous ti rich amphibole kaersutite biotite two pyroxenes and rhyolitic and alkali feldspar glasses all phases have been extensively analyzed with an electron microprobe the new mineralogical information is combined with a complementary experimental study of kaersutite melt equilibria this combined data set can be used to formulate a system of linear equations which can then be solved to determine the composition of the originally trapped melt this calculation reveals that the trapped melt was an feo rich and al2o3 poor basalt the melt composition is shown to be consistent with the crystallization sequence both inside the melt inclusions and in the rock matrix the major element chemistry of this liquid closely resembles terrestrial boninite lavas the new data also allow the intensive conditions temperature total pressure and water fugacity of chassigny crystallization to be estimated two pyroxene geothermometry indicates that equilibration temperatures were 1000 50 c although amphibole does not coexist with melt until t 960 c the trapped liquid initially contained 1 5 wt dissolved water crystallization of anhydrous phases caused water to buildup in the trapped melt prior to kaersutite crystallization the melt must have contained at least 4 wt dissolved water suggesting that a minimum of 1 5 kbar total pressure is required a maximum total pressure cannot be inferred but all available data are consistent with low pressure 5 kbar crystallization finally x h2o in the fluid in the melt inclusion is estimated to have been at least 0 8 in order to stabilize amphibole without plagioclase implying that the water fugacity was 1480 bars the existence of hydrous melts and conditions appropriate for amphibole crystallization suggest that evolved sio2 rich lavas exist on the chassigny parent body mars

stacked 2 6 ma grain size record from the chinese loess based on five sections and correlation with the deep sea δ18o record 1 this study aims to establish a stacked climate record of the quaternary period from the chinese loess sequence and to address the forcing mechanisms for the regional climate history of the loess plateau by correlating the stacked record with a composite 18o record in deep sea sediments a total of 18 352 samples were obtained from five loess sections located at baoji lingtai jingchuan puxian and pingliang in the southern and middle loess plateau these yielded high resolution grain size records between section correlation of these shows that although small depositional hiatuses are present in places within a single section most parts of the sections display near continuous dust deposition throughout the quaternary the grain size records were tuned simultaneously to the theoretical variations in obliquity and precession of the earth s orbit the grain size records plotted on their orbital timescales were then averaged to form a stacked loess grain size time series termed the chiloparts record this resolves most of the orbital timescale paleoclimate events buried in the loess soil sequences of the southern and middle loess plateau and can be used as a regional archive of the pleistocene climate history in the loess plateau comparison of the chiloparts record with a composite marine 18o record shows that for the past 1 8 ma the loess paleosol record can be correlated almost cycle by cycle with the marine record several discrepancies in the climatic events between the two records have also been identified implying that regional forcing mechanisms may have played a part in the climatic evolution of the chinese loess plateau

do stable isotope data from calcrete record late pleistocene monsoonal climate variation in the thar desert of india late pleistocene terrestrial climate records in india may be preserved in oxygen and carbon stable isotopes in pedogenic calcrete petrography shows that calcrete nodules in quaternary sediments of the thar desert in rajasthan are pedogenic with little evidence for postpedogenic alteration the calcrete occurs in four laterally persistent and one nonpersistent eolian units separated by colluvial gravel thermoluminescence and infrared and green light stimulated luminescence of host quartz and feldspar grains gave age brackets for persistent eolian units i iv of ca 70 000 60 000 ca 60 000 55 000 ca 55 000 43 000 and ca 43 000 25 000 yr respectively the youngest eolian unit v is 10 000 yr old and contains no calcrete stable oxygen isotope compositions of calcretes in most of eolian unit i in the upper part of eolian unit iv and in the nonpersistent eolian unit range between 4 6 and 2 1 pdb these values up to 4 4 greater than values from eolian units ii and iii are interpreted as representing nonmonsoonal18o enriched normal continental waters during climatic phases when the monsoon weakened or failed conversely 25 000 60 000 yr old calcretes eolian units ii and iii probably formed under monsoonal conditions the two periods of weakened monsoon are consistent with other paleoclimatic data from india and may represent widespread aridity on the indian subcontinent during isotope stages 2 and 4 the total variation in 13c is 1 7 0 0 1 7 and 13c covaries positively and linearly with 18o 13c values are highest when 18o values indicate the most arid climatic conditions this is best explained by expansion of c4grasses at the expense of c3plants at low latitudes during glacial periods when atmosphericpco2was lowered c4dominance was overridingly influenced by global change in atmosphericpco2despite the lowered summer rainfall

multiple expansions of c4 plant biomass in east asia since 7 ma coupled with strengthened monsoon circulation the expansion of plants using the c4 photosynthetic pathway is one of the most prominent changes in the global ecosystem during the cenozoic era a significant late miocene expansion is well documented however the existence and cause of subsequent expansions are still not clear owing in part to the lack of long continuous climate vegetation records here we present two high resolution carbon isotope time series covering the past 7 m y derived from eolian deposits on the chinese loess plateau the data indicate three intervals of significant c4 plant expansions within the semiarid monsoonal region of east asia ca 2 9 2 7 ma 1 3 0 9 ma and 0 6 ma present these expansions covary with strengthened east asian summer monsoon circulation we conclude that in east asia large scale late miocene c4 c3 vegetation changes in semiarid areas have been primarily driven by warm seasonal precipitation and temperature variations associated with changes in monsoon circulation

megarhizoliths in pleistocene aeolian deposits from gran canaria spain ichnological and palaeoenvironmental significance the pleistocene dune field of tufia located on the east of gran canaria spain contains different stratigraphic levels of indurated pillar like structures that are interpreted as megarhizoliths the megarhizoliths occur at the top of different aeolian sets and reach 31 5 cm in diameter and over 1 m in height these scattered free standing vertical cylindrical to slightly conical columns usually appear as hollow cylinders displaying elliptical cross sections aligned with the prevailing wind on the leeward side of some specimens the external wall shows a tail of rock matrix resembling a sort of wind shadow these tails and other remains of the associated rock matrix show a texture composed of long horizontal parallel cylinders orientated with the wind internally the most complete structures show five concentrically arranged zones zone a is a central pore corresponding to the cavity originally occupied by the root zones b and c which include alveolar and laminated carbonate textures indicating that carbonate precipitation was mostly induced by the roots and their associated microorganisms and zones d and e consisting mostly of aeolian sands in d the sand grains show thin micritic coatings whereas in e vadose aragonite cements can be seen on the grain surface suggesting a less biogenic influence in their formation the degree of cementation and the time of the precipitation of carbonate around the roots controlled the preservation of these zones thus in some cases zones b c and or d are not preserved cylinders are up to 30 the diameter of the root that nucleated them the presence of the megarhizoliths at the top of the aeolianite beds indicates that aeolian sedimentation halted several times allowing soil formation and plant colonisation during slightly more humid periods the occurrence of megarhizoliths is further proof of the alternation of arid and slightly more humid climates in the north atlantic during the last glacial period it is also noted that they may be misinterpreted as animal trace fossils or tree trunk casts resulting in incorrect ichnological or palaeoenvironmental interpretations

ice volume forcing of east asian winter monsoon variations in the past 800 000 years particle size measurements of some typical loess soil samples taken in different localities of the chinese loess plateau demonstrate that the grain size ratio of 10 m can be used as an indicator of variations in intensity of the east asian winter monsoon winds grain size curves of the baoji and weinan sections show that this proxy indicator is very sensitive to loess soil alterations analytical results also suggest that during soil forming periods eolian dust accumulation was still substantial and hence loess deposition can be regarded as a nearly continuous process during the quaternary period in this study we compared the baoji grain size time series with the specmap marine isotope record with the objective of elucidating the dynamic linkage between changes in global ice volume and the winter monsoon circulation both records show good agreement at both time and frequency domains in particular the winter monsoon variations are also dominated by a 100 000 yr period over the past 800 000 yr it is thus inferred that direct local insolation forcing could be less important in driving the east asian winter monsoon variability and alternatively variations in glacial age boundary conditions may have played a key role in modulating and pacing its strength and timing

holocene development of the yellow river s subaqueous delta north yellow sea high resolution seismic profiles from the north yellow sea reveal a 20 40 m thick subaqueous clinoform delta that wraps around the eastern end of the shandong peninsula extending into the south yellow sea this complex sigmoidal oblique clinoform containing an estimated 400 km 3 of sediment overlies prominent relict transgressive surfaces the nearshore topset of the clinoform 50 m contain less than 1 m of holocene sediment with low sedimentation rates 1 mm year in contrast to other clinoforms the shandong clinoform appears to be a compound subaqueous deltaic system with what we interpret to be proximal and distal phases of clinoform development the underlying proximal sequence formed proximally between f11 and 9 2 ka in response to a temporary pause in the rapid postglacial sea level rise after the meltwater pulse 1b mwp 1b and increased discharge from the yellow river to the north yellow sea due to intensification of the summer monsoon a flooding surface appears to separate the proximal and distal phases corresponding to the next rapid sea level rise 9 5 9 2 ka bp mwp 1c since 9 2 ka bp an overlying distal sedimentary sequence has accumulated reflecting the backstepping and shifting river mouth westward to the gulf of bohai some inputs from coastal erosion and nearby small streams may be locally important along shore transport cross shelf advection and upwelling in the north yellow sea have reworked post lgm sediment and have helped maintain the morphology of the clinoform in the shandong mud wedge d 2004 elsevier b v all rights reserved

radiocarbon dating of aquatic gastropod shells and its significance in reconstructing quaternary environmental changes in the alashan plateau of northwestern china abstract using landform evolution and lake sediment records to reconstruct quaternary environmental changes requires reliable chronology however there is an ongoing debate regarding the fossil shells of aquatic gastropods in carbonate rock area to be used for radiocarbon dating the focus of this debate is whether living gastropods incorporate the dead carbon which would affect the accuracy of the dating results living aquatic gastropods were selected from habitats on carbonate terrain in arid region in this study 64 shell samples from living gastropods including cipangopaludina chinensis gyraulus convexiusculus and radix auricularia collected from the alashan plateau of northwestern china were dated by accelerator mass spectrometry ams 14c dating the results revealed that only five samples 8 from the same site contained no dead carbon the other 59 samples 92 contained dead carbon in various amounts 59 samples contained 0 10 dead carbon and 33 samples contained more than 10 dead carbon of the samples 56 were radix auricularia and their 14c ages varied from present to 3253 cal yr bp two of the samples were gyraulus convexiusculus samples dated at 379 and 290 cal yr bp which are highly consistent with 14c ages of radix auricularia samples from the same site the other six cipangopaludina chinensis samples were dated at 407 863 cal yr bp thus most of living aquatic gastropods from habitats on carbonate terrain contained dead carbon the amount of dead carbon in the gastropod shells was nonselective among the three species radiocarbon dating of aquatic gastropod shells may not be useful for studying processes that occurred over multi millennial timescales at different localities in areas of carbonate rock it is difficult to establish high resolution chronologies using 14c ages of gastropod shells in arid regions with carbonate rocks unless the limestone effect has been corrected

a physiological mechanism for the formation of root casts abstract root casts are calcified structures in the shape of roots often found exposed on aeolian sand dunes a central channel of the cast may be void or filled with soft carbonate transpiration drives water flux towards the roots resulting in mass flow of dissolved nutrients towards the root it was hypothesised that root casts form in cation rich substrates as a consequence of transpiration driven mass flow of cations to roots in excess of that required by the plant with subsequent cementation of sediments around the root mould through formation of carbonates the elemental compositions of both ancient root casts 6870 60 bp of an unknown plant from still bay western cape south africa and concreted sediments associated with cluster roots of a presently occurring dune plant morella cordifolia l killick myricaceae were found to have similar elemental compositions and were positively correlated both root casts and cluster root sediments had higher ca and other cations and also higher inorganic c than that of dune sand from isotope analysis the most likely sources of c for formation of carbonates in the cluster root sediment 13c 0 8 0 29 and in the root casts 13c 5 3 0 6 to 7 6 0 3 was a varying combination of the bulk atmosphere predicted 13c of concretion 1 3 and plant respiration derived co2 predicted 13c of concretion 11 5 despite extremely low p 0 05 mol g 1 sand in dune sand the leaves of m cordifolia accumulated amounts of p comparable to other cluster rooted plants in the adjacent somewhat nutrient richer fynbos it was concluded that in the generally nutrient poor but cation rich sand transpiration driven water flux would deliver scarce nutrients to the cluster root rhizosphere of m cordifolia in the process of this mass flow ca is delivered in excess of plant demand and accumulates in both the root tissue and the rhizosphere this ca is chemically converted to caco3 over time resulting in the formation of persistent root casts

mio pliocene monsoonal record from himalayan foreland basin indian siwalik and its relation to vegetational change carbon and oxygen isotope ratios of soil carbonate nodules and carbon isotope ratio of associated organic matter were measured from three indian siwalik stratigraphic successions in order to reconstruct vegetational history and change in contemporaneous precipitation 13c values of soil carbonates show that from 10 5 to 6 ma the vegetation was c3 type and around 6 ma c4 grasses appeared the 18o variations of soil carbonates suggest that the monsoon system intensified with one probable peak at around 10 5 ma and a clear onset at 6 ma with peak at 5 5 ma after 5 5 ma monsoon strength decreased and attained the modern day condition with minor fluctuations which is supported by marine proxy of upwelling in the arabian sea and sedimentary morphology in siwalik the covariation between 18o and 13c data suggests that a change in precipitation pattern was partly responsible for expansion of c4 grasses in a mixed c3 c4 environment estimation of abundance of c3 and c4 plants using soil carbonate in one case and residual soil organic matter in another may differ this can be explained by assuming that the plant respired co2 is the main contributor of carbon in soil carbonate and may have different isotopic composition from that of the residual organic matter in the soil in addition the abundance estimate of c3 c4 plants also shows variation with time probably caused by change in growing season conditions through time

a probabilistic sediment cascade model of sediment transfer in the illgraben we present a probabilistic sediment cascade model to simulate sediment transfer in a mountain basin illgraben switzerland where sediment is produced by hillslope landslides and rockfalls and exported out of the basin by debris flows and floods the model conceptualizes the fluvial system as a spatially lumped cascade of connected reservoirs representing hillslope and channel storages where sediment goes through cycles of storage and remobilization by surface runoff the model includes all relevant hydrological processes that lead to runoff formation in an alpine basin such as precipitation snow accumulation snowmelt evapotranspiration and soil water storage although the processes of sediment transfer and debris flow generation are described in a simplified manner the model produces complex sediment discharge behavior which is driven by the availability of sediment and antecedent wetness conditions system memory as well as the triggering potential climatic forcing the observed probability distribution of debris flow volumes and their seasonality in 2000 2009 are reproduced the stochasticity of hillslope sediment input is important for reproducing realistic sediment storage variability although many details of the hillslope landslide triggering procedures are filtered out by the sediment transfer system the model allows us to explicitly quantify the division into transport and supply limited sediment discharge events we show that debris flows may be generated for a wide range of rainfall intensities because of variable antecedent basin wetness and snowmelt contribution to runoff which helps to understand the limitations of methods based on a single rainfall threshold for debris flow initiation in alpine basins

gravel deposits on the margins of the qinghai xizang plateau and their environmental significance abstract the thick deposits of quaternary gravels found along the margins of the qinghai xizang tibet plateau have been studied for decades here we concentrate on two sediment series widely developed along the kunlun tian shan and qilian mountains the xiyu formation a molassic series of lower pleistocene age and the middle and upper pleistocene gobi gravels these two series with their contained fossil assemblages throw light on the question of the mean altitudes and uplift rates of the tibetan plateau during the quaternary and on the related problem of the vigour and penetration of advected summer monsoonal moisture into central asia the sedimentary series on the northern piedmonts of the tibetan plateau considered here challege the view that plateau uplift accelerated in the upper pleistocene they indicate that the plateau had reached mean altitudes in the range 4000 5000 m perhaps by the end of the lower pleistocene and certainly by the middle pleistocene this diminished the incursion of southerly monsoonal moisture and so imposed arid and semi arid conditions across much of a vast region north of the plateau which among other effects precluded widespread mountain glaciation in the lower pleistocene and general ice sheet glaciation of the tibetan plateau as a whole

k and cl concentrations on the martian surface determined by the mars odyssey gamma ray spectrometer implications for bulk halogen abundances in mars 1 orbital gamma ray spectrometry shows that the martian surface has a mean cl k ratio of 1 3 0 2 indistinguishable from the ratio in ci chondrites 1 28 although cl and k fractionate by magma degassing and aqueous processing during igneous partial melting both elements are highly incompatible thus if the surface cl k reflects the bulk crustal value then the mantle hence primitive silicate mars also has a roughly ci ratio martian meteorite data indicate that cl br is also approximately chondritic suggesting that elements that condensed in the nebula between 1000 k k and cl to 500 k br are uniformly depleted in mars at about 0 6 ci chondrite concentrations mars clearly does not contain 0 6 ci levels of h2o which would be 6 wt indicating that mars was constructed by planetesimals rich in volatile elements but not in water

carbonate rhizoliths in loess and their implications for paleoenvironmental reconstruction revealed by isotopic composition δ13c 14c abstract loess paleosol sequences are important terrestrial archives for studying quaternary climate changes they often contain secondary carbonates including e g rhizoliths calcified roots these secondary carbonates are precipitated in isotopic equilibrium with root derived co2 and are therefore used to reconstruct the vegetation present during their formation based on stable carbon isotopic composition 13c usually the chronological context of secondary carbonates in general is not mentioned because it is assumed that they are formed synsedimentary with loess deposition the loess paleosol sequence at nussloch sw germany contains in its youngest part upper wurmian large carbonate rhizoliths with diameters of up to 5 cm and lengths of up to 1 m and more which have not been described in this profile so far we investigated rhizoliths as well as loess adjacent to and distant from rhizoliths for carbonatic carbon ccarb and organic carbon corg contents as well as their isotopic composition 13c radiocarbon dating to identify the rhizolith origin and the time frame of their formation considering the 13c fractionation by carbonate precipitation the 13ccarb values 10 9 0 1 revealed c3 plant origin of the rhizolith carbonate and the absence of large amounts of occluded primary loess carbonate similar 14c ages of rhizolith ccarb and corg 3788 59 years bp and 3150 59 years bp respectively argued for the absence of postsegregational alteration therefore they are suitable for the reconstruction of paleoenvironmental conditions after loess sedimentation the 14c ages clearly indicate that rhizoliths did not form synsedimentary roots penetrated the loess at nussloch after the deposition had ceased at 15 ka bp even in the loess adjacent to the rhizoliths up to a distance of 5 cm 13ccarb values indicate the presence of secondary carbonate deriving from postsedimentary organic matter of origin other than that of the reference loess material hence this postsedimentary input of younger root biomass might have masked the initial plant signal in loess paleosol sequences which could cause uncertainties for paleoenvironmental reconstructions based solely on loess organic matter

stable isotope compositions sources and paleoenvironmental significance of holocene calcareous root tubes in the tengger desert northwest china abstract valuable archives of paleoenvironmental changes are scarce in the hinterlands of deserts calcareous root tubes crts a form of pedogenic carbonate are widely distributed in the hinterland of the tengger desert northwest china the investigations of 13c and 18o values within crts from the tengger desert have a great potential to provide new significant archives for paleoenvironmental reconstructions in this area in this study 30 crt samples from the tengger desert were collected all the samples were described using cathodoluminescence cl and their 13c and 18o values were measured the results revealed that limited marine carbonate was incorporated in the crts in the tengger desert and 13c and 18o values of the inner belt of the crts were not affected by recrystallization therefore 13c and 18o values of the crts could accurately record environmental conditions in the tengger desert the carbon source of the crts was a mixture of soil co2 derived from root respiration and atmospheric co2 furthermore 13c values of most samples were lower than 3 0 indicating that c3 vegetation was the main vegetation in the tengger desert during the middle and late holocene moreover 18o values of the crts were ultimately inherited from summer precipitation influenced by the amount effect in summer and strong evaporation the lower 18o values of the crts revealed that relatively higher effective moisture occurred from 7 to 4 cal kyr bp while the higher 18o values indicated that relatively lower effective moisture occurred from 4 to 2 cal kyr bp in the tengger desert the holocene millennial scale moisture changes in the hinterland of the tengger desert suggest an arid early holocene 11 7 7 cal kyr bp a relatively humid mid holocene 7 4 cal kyr bp and a humid to arid late holocene 4 2 cal kyr bp the discrepancy of effective moisture change reconstruction based on the crts in the tengger desert and adjacent lake sediments during the early holocene demonstrated that the reliability of the reconstructed results from lake sediments during this period needs further investigation

fluorine geochemistry of basaltic rocks from continental and oceanic regions and petrogenetic application fluorine contents in about 300 samples of various types of basalts and related rocks from continental southwestern u s a zaire deccan and south africa and oceanic regions hawaii and mid atlantic ridge between 23 n and 40 n were determined by a selective ion electrode method

fluids on differentiated asteroids evidence from phosphates in differentiated meteorites gra 06128 and gra 06129 abstract paired meteorites graves nunatak 06128 and 06129 gra represent an ancient cumulate lithology 4565 9 ma 0 3 containing high abundances of sodic plagioclase textures and stable isotope compositions of gra indicate that superimposed on the igneous lithology is a complex history of subsolidus reequilibration and low temperature alteration that may have extended over a period of 150 myr in gra apatite is halogen rich with cl between 4 5 and 5 5 wt and f between 0 3 and 0 9 wt the cl cl f oh ratio of the apatite is between 0 65 and 0 82 the cl and f are negatively correlated and are heterogeneously distributed in the apatite merrillite is low in halogens with substantial na in the 6 fold coordinated na site 2 5 and mg in the smaller octahedral site the merrillite has a negative eu anomaly whereas the apatite has a positive eu anomaly the chlorine isotope composition of the bulk gra leachate is 1 2 relative to standard mean ocean chloride smoc ion microprobe chlorine isotope analyses of the apatite range between 0 5 and 1 2 textural relationships between the merrillite and apatite and the high cl content of the apatite suggest that the merrillite is magmatic in origin whereas the apatite is a product of the interaction between merrillite and a cl rich fluid if the replacement of merrillite by apatite occurred at approximately 800 c the fluid composition is f hcl f h2o 0 0383 and a hcl molality of 2 13 and f hcl f hf 50 100 it is anticipated that the calculated f hcl f h2o and a hcl molality are minimum values due to assumptions made on the oh component in apatite and basing the calculations on the apatite with the lowest xcl the bulk 37cl of gra is a 2 outlier from chondritic meteorites and suggests that parent body processes resulted in fractionation of the cl isotopes

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

recharge to the inter dune lakes and holocene climatic changes in the badain jaran desert western china we present new estimates on evaporation and groundwater recharge in the badain jaran desert western inner mongolia of northwestern china based on a modified penman equation suitable for lakes in china geochemical data and water balance calculations suggest that local rainfall makes a significant contribution to groundwater recharge and that past lake level variations in this desert environment should reflect palaeoclimatic changes the chronology of lake level change established by radiocarbon and u series disequilibrium dating methods indicates high lake levels and a wetter climate beginning at ca 10 ka and lasting until the late mid holocene in the badain jaran desert the greatest extension of lakes in the inter dune depressions indicates that the water availability was greatest during the mid holocene relicts of neolithic tools and pottery of qijia culture 2400 1900 bc suggest relatively intensive human activity in the badain jaran desert during the early and middle holocene supporting our interpretation of a less harsh environment wetter climates during the holocene were likely triggered by an intensified east asian summer monsoon associated with strong insolation

insights into martian water reservoirs from analyses of martian meteorite que94201 the martian atmospheric d h value of 5 2 times terrestrial is significantly higher than any found on earth and has been ascribed to preferential loss of h relative to d from the atmosphere through jeans escape over time here based on ion microprobe analyses of apatite grains from martian meteorite que94201 it is shown that the pre jeans escape martian water reservoir has a d h value twice that of terrestrial water rather than the terrestrial value that has been assumed in prior work the data support a two stage history for martian volatiles in which early hydrodynamic escape enriched martian water to 2x terrestrial d h values subsequent jeans escape to produce the current atmospheric values has thus been responsible for less d enrichment than previously thought a martian crust containing 2 3 times more water than previously proposed is implied by the results

compositional variability of terrestrial mantle apatites thermodynamic modeling of apatite volatile contents and the halogen and water budgets of planetary mantles abstract apatites in ultramafic xenoliths from hawaii kamchatka nunivak island lunar crater volcanic field and the navajo volcanic field have variable volatile f cl oh compositions that correlate with their petrogenesis apatites in metasomatized lherzolite harzburgite xenoliths are relatively cl rich whereas apatites in igneous pyroxenite and amphibolite xenoliths are relatively f rich our results support the generalization of o reilly and griffin 2000 that metasomatic apatites tend to be cl rich and magmatic apatites tend to be f rich mantle metasomatism may largely be the consequence of devolatilization of cl rich fluids from subducted lithosphere however the occurrence of metasomatic xenoliths far removed from subduction zones e g bullenmerri as well as the geochemistry of cl in some plume basalts and diamonds indicates that not all metasomatism is subduction triggered thermodynamic modeling of the influence on apatite compositions of variable f cl h2o and p abundances as well as temperature is consistent with the idea that terrestrial mantle fluids are h2o rich and that halogen enrichment in terrestrial apatites need not represent large absolute halogen abundances in the fluids the models indicate that the occurrence of volatile poor calcium phosphate merrillite whitlockite in the martian and terrestrial mantles is facilitated by halogen and phosphorus rich and water poor environments the rarity of this assemblage in the terrestrial mantle compared to mars is consistent with the relatively wet and halogen and phosphorus poor nature of the terrestrial mantle compared to that of mars

pedogenic carbonate cutans on clasts in soils as a record of history of grassland ecosystems pedogenic carbonate cutans coatings pendants rinds on coarse clasts are common in stony soils of arid and semiarid regions dominated by open vegetation this paper gives an overview of the potential of the carbonate cutans for paleograssland research using data from literature and personal observations carbonate coatings are stratified into distinct microlamina which can provide a record of local environmental changes lamina made of a rather pure calcium carbonate with better formed and parallel oriented crystals seem to be indicative of relatively dry phases that were less favorable for biological activity a high content of admixtures poorer formed and randomly oriented calcite crystals presumably mark wetter periods characterized by climatic amelioration at a most general level n 13 c of the cutan carbonate can provide information on the type of photosynthesis of local vegetation whereas n 18 o in carbonate material of the coatings correlates with oxygen isotopic composition of precipitation water at the site and is sensitive to fluctuations in temperature to obtain chronological evidence on cutan formation the 14 c and th u methods can be applied with certain limitations additionally cutan growth rates can be used to evaluate the age of these features fl 2002 elsevier science b v all rights reserved

geochemistry of intermediate olivine phyric shergottite northwest africa 6234 with similarities to basaltic shergottite northwest africa 480 and olivine phyric shergottite northwest africa 2990 the newly found meteorite northwest africa 6234 nwa 6234 is an olivine ol phyric shergottite that is thought based on texture and mineralogy to be paired with martian shergottite meteorites nwa 2990 5960 and 6710 we report bulk rock major and trace element abundances including li abundances of highly siderophile elements re os isotope systematics oxygen isotope ratios and the lithium isotope ratio for nwa 6234 nwa 6234 is classified as a martian shergottite based on its oxygen isotope ratios bulk composition and bulk element abundance ratios fe mn al ti and na al the li concentration and d 7 li value of nwa 6234 are similar to that of basaltic shergottites zagami and shergotty the rare earth element ree pattern for nwa 6234 shows a depletion in the light ree la nd compared with the heavy ree sm lu but not as extreme as the known depleted shergottites thus nwa 6234 is suggested to belong to a new category of shergottite that is geochemically intermediate in incompatible elements the only other basaltic or ol phyric shergottite with a similar intermediate character is the basaltic shergottite nwa 480 rhenium osmium isotope systematics are consistent with this intermediate character assuming a crystallization age of 180 ma we conclude that nwa 6234 represents an intermediate compositional group between enriched and depleted shergottites and offers new insights into the nature of mantle differentiation and mixing among mantle reservoirs in mars

partitioning in ree saturating minerals theory experiment and modelling of whitlockite apatite and evolution of lunar residual magmas we present compositions including rees determined by ion microprobe of apatite and whitlockite in lunar rock assemblages rich in incompatible trace elements total concentrations of ree oxides in whitlockites range from 9 13 wt and those in apatites range from 0 15 to 1 wt ratios of ree concentrations in whitlockite to those in coexisting apatite range from 10 to 60 the distribution of mg and fe between apatite and whitlockite is correlated to that of coexisting mafic silicates magnesium is strongly preferred by whitlockite and fe is preferred by apatite incorporation of rees in whitlockite is dominated by the coupled substitution of 2ree3 in ca b sites vacancy in ca iia for 2ca 2 in ca b sites and ca2 na in ca iia other substitutions account for only a small portion of the rees in whitlockite over the observed concentration range thus ree concentrations become partially saturated as the primary substitution approaches its stoichiometric limit of two rees per fifty six oxygens leading to reduced whitlockite melt distribution coefficients e g decreasing from twenty five to ten for nd the ree concentrations of lunar residual melts are not depleted by whitlockite crystallization in assemblages consisting mainly of other minerals in typical proportions distribution coefficients for the rees in lunar apatite appear to be low and variable e g 0 2 0 8 for nd variations in the modal ratio of whitlockite to apatite specifically the abundance of whitlockite lead to a range of ree concentrations in the phosphates and variations in the magnitude of ree concentration ratios between whitlockite and apatite if apatite crystallizes before whitlockite or in the absence of whitlockite as textures in several samples indicate then apatite zoned in rees and apatite crystals of different ree concentrations may occur in a given sample provided there is some amount of fractional crystallization and apatite does not later equilibrate this may occur because in the absence of whitlockite in the crystallizing assemblage the rees are highly incompatible relative to the crystalline assemblage so ree concentrations in lunar residual melts increase strongly during small increments of late stage crystallization once whitlockite begins to crystallize bulk distribution coefficients for the rees although still 1 are only mildly incompatible so the change in ree concentrations of residual melts with further crystallization is small consistent with the lack of ree zoning in whitlockite the ree concentrations in lunar whitlockites are modelled as resulting mainly from equilibrium crystallization of the assemblages in which they occur metasomatism or other secondary metamorphic processes are not indicated local melt pocket equilibrium at advanced stages of crystallization may lead to variable ree concentrations and variable whitlockite apatite concentration ratios within the same sample parent melts with extremely high ree concentrations are not required in order to crystallize ree rich lunar whitlockite if modal proportions of whitlockite are low

apatite as a probe of halogen and water fugacities in the terrestrial planets abstract apatite preserves a record of the halogen and water fugacities that existed during the waning stages of crystallization of planetary magmas when they became saturated in phosphates we develop a thermodynamic formalism based on apatite merrillite equilibria that makes it possible to compare the relative values of halogen and water fugacities in martian lunar and terrestrial basalts accounting for possible differences in pressure temperature and oxygen fugacities among the planets we show that each of these planetary bodies has distinctive ratios among volatile fugacities at apatite saturation and that these fugacities are in some cases related in a consistent way to volatile fugacities in the mantle magma sources our analysis shows that the martian mantle parental to basaltic snc meteorites was dry and poor in both fluorine and chlorine compared to the terrestrial mantle the limited data available from mars show no secular variation in mantle halogen and water fugacities from 4 ga to 180 ma the water and halogens found in present day martian surface rocks have thus resided in the planet s surficial systems since at least 4 ga and may have been degassed from the planet s interior during a primordial crust forming event in comparison to the earth and mars the moon and possibly the eucrite parent body too appear to be strongly depleted not only in h 2 o but also in cl 2 relative to h 2 o chlorine depletion is strongest in mare basalts perhaps reflecting an eruptive process characteristic of large scale lunar magmatism

formation and environmental significance of late quaternary calcareous root tubes in the deserts of the alashan plateau northwest china calcareous root tubes are widely distributed across the badain jaran desert and the tengger desert of the alashan plateau in northwest china however the reliability of their 14 c dating results and their environmental significance remain unclear in this study the conventional 14 c ages of 31 calcareous root tube samples and one aquatic mollusc shell sample which were all collected from the badain jaran desert and the tengger desert were measured the results reveal that nine of the 14 calcareous root tube samples from the badain jaran desert were from marine isotope stage mis 3 while two samples were from mis 2 the other three samples were dated to the mid holocene one of which is consistent with the aquatic mollusc shell sample collected from the shoreline of zhunzhahanjilin lake in the badain jaran desert moreover the 17 calcareous root tube samples from the tengger desert were all dated to the mid and late holocene most of which were from the mid holocene the results demonstrate that calcareous root tubes can be used as

radiocarbon dating of thin pedogenic carbonate laminae from holocene archaeological sites radiocarbon dating has been previously suggested to be applicable to pedogenic carbonate however until now the validity of radiocarbon dates from pedogenic carbonate remained poorly understood because of the relatively low resolution of chronological controls in this study we compared the radiocarbon dates a total of 21 of thin 0 2 0 3 mm in thickness laminae of pedogenic carbonate coatings on clasts from holocene archaeological sites in the eastern mediterranean and south siberia with independently estimated age ranges for these sites we obtained a high correlation between the oldest laminae of coatings with the site ages the 14 c ages of pedogenic carbonate were systematically younger by c 0 3 1 6 ka mean c 0 75 ka compared with archaeological sites this finding suggests that pedogenic carbonate despite potential complicating factors can be dated more accurately with 14 c than has been generally appreciated

crystallization conditions of los angeles a basaltic martian meteorite the texture of los angeles stone 1 is dominated by relatively large 0 5 2 0 mm anhedral to subhedral grains of pyroxene and generally subhedral to euhedral shocked plagioclase feldspar maskelynite minor phases include subhedral titanomagnetite and ilmenite fe rich olivine olivine augite dominated symplectites some of which include a si rich phase and some which do not pyrrhotite phosphate s and an impact shock related alkali and silica rich glass closely associated with anhedral to euhedral silica grains observations and model calculations indicate that the initial crystallization of mg rich pigeonitic pyroxenes at 1150 c probably concomitantly with plagioclase was followed by pigeonitic and augitic compositions between 1100 and 1050 c whereas between 1050 and 920 to 905 c pyroxene of single composition crystallized below 920 to 905 c single composition fe rich clinopyroxene exsolved to augite and pigeonite initial appearance of titanomagnetite probably occurred near 990 c and fmq 1 5 whereas at and below 990 c and fmq 1 5 titanomagnetite and single composition fe rich clinopyroxene may have started to react producing ilmenite and olivine however judging from the most common titanomagnetite compositions we infer that most of this reaction likely occurred between 950 and 900 c at fmq 1 0 0 2 and nearly simultaneously with pyroxene exsolution thus producing assemblages of pigeonite titanomagnetite olivine ilmenite and augite we deem this reaction as the most plausible explanation for the formation of the olivine augite dominated symplectites in los angeles but we cannot preclude possible contributions to the symplectites from the shock related alkali and silica rich glass or shocked plagioclase and the breakdown of fe rich pigeonite compositions to olivine augite silica below 900 c reactions between fe ti oxides and silicate minerals in los angeles and other similar basaltic martian meteorites can control the t fo2 equilibration path during cooling which may better explain the relative differences in fo2 among the basaltic martian meteorites

the ion chemistry of lakes and late holocene desiccation in the badain jaran desert inner mongolia china abstract in the markedly arid badain jaran desert one of the least studied areas in the world over a hundred permanent lakes exist among the dunes the geochemistry of water samples from nine lakes and from the groundwater in the desert and on its periphery was investigated ion chemistry of the water from these desert lakes changes considerably on a regional scale we argue that there is a positive correlation between the ages of these lakes and their totally dissolved solids tds varying between 1 2 and 398 2 g l tritium analysis of groundwater in wells gives an age generally older than four decades and younger than 100 years the lacustrine deposits freshwater fauna and shorelines indicate the existence of large water bodies with low salinities in the inter dune hollows of this desert during the early and middle holocene the precipitation in this desert during the early and middle holocene was estimated to be ca 200 mm year on average at least twice as high as at present on the basis of paleoecology tl and radiocarbon ages it was concluded that the huge enrichment of ions in the lakes and decrease of water availability originated from climatic desiccation during the last 4000 years the paleoclimate of the badain jaran desert reported here was remarkably consistent with the late quaternary climatic histories of the regions to the immediate north west east and south of the study area

evidence for holocene environmental changes in the northern fertile crescent provided by pedogenic carbonate coatings abstract holocene environmental changes in the northern fertile crescent remain poorly understood because of the scarcity of local proxy records in the region in this study we investigated pedogenic soil formed carbonate coatings on stones at the pre pottery neolithic site gobekli tepe as an indicator of local early mid holocene environmental changes the 14c ages and stable isotopic composition of carbon and oxygen in thin 0 2 0 3 mm thick pedogenic carbonate lamina indicate two main periods of coating formation the early holocene ca 10000 6000 cal yr bp and the mid holocene ca 6000 4000 cal yr bp during the first period there was an inverse relationship between 13c and 18o curves a decrease in 13c values coincide with an increase in 18o values for this period a trend towards higher temperatures is suggested in the mid holocene the mean rate of coating growth was 2 3 times higher than in the early holocene both 13c and 18o reached their maximum values during this time and the direction of changes of the 13c and 18o curves became similar the combination of data suggests that this period was the most humid in the holocene and on average warmer than the early holocene at ca 4000 cal yr bp secondary accumulation of carbonate ceased presumably reflecting a shift to a more arid climate

core formation in the earth and shergottite parent body spb chemical evidence from basalts constraints on processes of core formation in terrestrial planets may be inferred from the abundances of siderophile and chalcophile elements in their mantles of particular interest is a comparison of processes of core formation in the earth and in the shergottite parent body spb a terrestrial planet tentatively inferred to be mars to this end we i present new inaa and rnaa analyses of the non antarctic snc meteorites ii infer the composition of the spb mantle from the compositions of the snc meteorites iii infer the composition of the earth s mantle from the compositions of terrestrial basalts and iv deconvolve the effects of volatile depletion core formation and mineral melt fractionation on the abundances of siderophile and chalcophile elements in the spb and the earth element abundances in the mantles of the spb and the earth are estimated from element element correlations observed among basalt samples in basalts from the spb the snc meteorites four groups of covariant elements are observed highly incompatible moderately incompatible indifferent and compatible from correlations within these groups the spb mantle is found to be depleted in volatile elements and strongly depleted in siderophile and chalcophile elements for the earth the element element correlation method gives a mantle composition similar to previous estimates compared to the earth the spb mantle is richer in moderately siderophile elements e g w p consistent with its inferred higher oxidation state chalcophile elements in the spb mantle are more depleted than in the earth s mantle particularly when compared to estimates of the original abundances of volatile chalcophile elements in the two planets in the spb mantle the nico ratio is nonchondritic in contrast to the chondritic ratio in the earth s mantle abundances of siderophile and chalcophile elements in the spb mantle may be modelled by equilibrium with solid metal and metallic sulfide liquid with some metal and sulfide trapped in the mantle i e homogeneous accretion and inefficient core formation neither this model nor a heterogeneous accretion model is satisfactory in explaining element abundances in the earth s mantle particularly the abundances of ni co mo and w nevertheless it appears that core formation in the spb and the earth left quite different chemical signatures in their planetary mantles

tropical climate instability the last glacial cycle from a qinghai tibetan ice core an ice core record from the guliya ice cap on the qinghai tibetan plateau provides evidence of regional climatic conditions over the last glacial cycle 36 cl data suggest that the deepest 20 meters of the core may be more than 500 000 years old the 18 o change across termination i is 5 4 per mil similar to that in the huascaran peru and polar ice cores three guliya interstadials stages 3 5a and 5c are marked by increases in 18 o values similar to that of the holocene and eemian 124 000 years ago the similarity of this pattern to that of ch 4 records from polar ice cores indicates that global ch 4 levels and the tropical hydrological cycle are linked the late glacial stage record contains numerous 200 year oscillations in 18 o values and in dust nh 4 and no 3 levels

holocene shorelines and lake evolution in juyanze basin southern mongolian plateau revealed by luminescence dating holocene environment change in the gobi desert of mongolia and northwestern china is of global significance as it is one of the key dust source areas of the world the juyanze basin located in the central gobi desert of southern mongolian plateau is one of the three terminal basins of the heihe river that flows north from the qilian mountain a series of geomorphic shorelines at different elevations around the basin indicate that large lake levels fluctuated during the past in this study we measured the exact elevation of shorelines in the juyanze basin using digital global positioning system and found seven shorelines at 37 36 34 30 28 24 and 22 m above modern basin floor a m b f optically stimulated luminescence dating was employed to date the deposition of beach sand and gravel sequences at these shorelines results indicate a paleolake developed in the basin at 5 ka when lake levels reached 26 m a m b f the lake level then gradually increased to 29 m a m b f at 3 3 ka and r

primary and secondary carbonate in chinese loess discriminated by trace element composition abstract carbonate in the eolian deposits on the chinese loess plateau carries a significant amount of information on the evolution of paleo environment however the paleo proxies based on total carbonate are largely complicated by the coexistence of primary and secondary carbonate this work provides a new method to quantify the relative proportion of primary and secondary carbonate in these eolian deposits according to the mn ca and mg ca ratios of bulk carbonate the carbonate associated mg and mn which can be extracted by selective dissolution using diluted weak acid are mostly derived from primary carbonate because the secondary carbonate contains very little mg and mn the amounts of mg and mn associated with carbonate could thus serve as proxies for the pedogenic dissolution of primary carbonate which reflect clear glacial interglacial changes of summer monsoon a positive correlation between the mn ca and mg ca ratios of bulk carbonate has been observed indicating binary mixing between secondary carbonate with the low mn ca and mg ca ratios and primary carbonate with high mn ca and mg ca ratios the high mn ca and mg ca ratios of primary carbonate endmember also indicate alxa arid lands as the main source of eolian deposits on chinese loess plateau the mn ca and mg ca ratios of carbonate could be employed as a quick method to check the purity of the secondary carbonate used for paleo environmental studies and help to interpret the paleo proxies based on the bulk carbonate the results reveal significant amount of primary carbonate included in the traditionally believed pure authigenic carbonate phases such as carbonate concretion rhizolith and the fine grain sized carbonate the new method also helps to appraise the control of the relative portion of primary and secondary carbonates on the stable carbon and oxygen isotopes of bulk carbonate high mg ca ratio and low mn ca ratio of the carbonate in red clay formation is observed which confirms the existence of authigenic dolomite

oxygen and carbon stable isotope composition of authigenic carbonates in loess sequences from the carpathian margin and podolia as a palaeoclimatic record abstract samples were collected from the outcrops situated in the north and east of the carpathian margin in the transition zone between the area of loess covers of eastern and western europe the chosen localities include two zones of temperate climate with slightly different prevailing wind directions these loess palaeosol sequences formed and develop in different time intervals early quaternary epoch podolia ukraine and late quaternary epoch carpathian foothills poland the isotopic analysis was carried out on many types of authigenic soil carbonates including nodules rhizoliths rhizocretions calcified root cells and bioclasts the carbon isotopic compositions 13 c of different types vary markedly these differences seem to be more important than the variations within one type of carbonate at a particular section the 13 c values for authigenic carbonate cements rhizoliths rhizocretions and nodules vary in a narrow range from about 11 to 8 suggesting that calcite cements were precipitated under roughly similar conditions with a considerable supply of co 2 derived from biomineralization of organic matter predominantly from c 3 plants the 18 o record of the calcite cements within the upper quaternary deposits exhibits relatively slight variability suggesting that 18 o values in soil water were homogeneous the significant depletion of 13 c as well as 18 o in calcite from calcified root cells 12 and 7 respectively and to a lesser extent from calcitic globules with respect to calcite cements points to different environments of formation the morphology of calcite crystals replacing root cells and their carbon and oxygen isotopic composition indicate that they may precipitate inside the root cells from fluids with organic compounds in general the temperature reconstructions yield an average mat about 11 c for the upper quaternary sediments deposited during mis 2 the estimated mat for sediments of mis 3 5 range from 12 to 14 c mean annual temperatures estimated for the lower quaternary of podolia fall in the range from 9 to 11 c with two single minimums about 7 c probably corresponding to short lived environmental changes the mat curve throughout the lower part of lower quaternary is more variable and shows several local shifts up to 3 c

dolomite as a tracer for the source regions of asian dust 1 the possibility of using dolomite as a source tracer for asian dust was assessed samples of potential dust sources were systematically collected from the arid semiarid areas in north china dolomite of detrital origin was detected only in samples taken from the regions on the north margin of tibetan plateau nmtp thus the nmtp originated dust can be detected by the presence of detrital dolomite and applications are performed for the modern dust in beijing and the ancient dust deposits of loess in north china contribution of the nmtp originated particles to the spring dust in beijing and the loess in chinese loess plateau and eastern tibetan plateau are suggested however dolomite cannot be detected in the studied dust storm dust and the loess in northeast china indicating their sources other than the nmtp regions

developing inorganic carbon based radiocarbon chronologies for holocene lake sediments in arid nw china abstract inorganic carbonates are often used to establish radiocarbon 14c chronologies for lake sediments when terrestrial plant remains tpr are rare or when bulk organic matter is insufficient for dating a problem that is common for many lakes in arid regions however the reservoir effect re as well as old carbon contributed from the lakes catchment make it difficult to establish reliable chronologies here we present a systematic study of inorganic 14c ages of two lake sediment sequences one from a small enclosed saline lake lake gahai in qaidam basin and the other from a large freshwater lake lake bosten in xinjiang modern dissolved inorganic carbon dic of the lakes paleo lake sediments exposed in the catchment and mollusk shells in core sediments from lake gahai were dated to assess the re and the contribution of pre aged carbon to the old ages in the cores we propose a statistical regression to assess more than one re for the 14c carbonate ages within our sedimentary sequences old radiocarbon ages contributed by detrital carbonates were assessed by comparing the ages of mollusk shells with those of carbonates at the same sediment depths we established the re of the authigenic component and assessed detrital old carbon contributions to our two sites and this was used to correct the 14c ages based on this approach we developed age models for both cores and tested them using 210pb ages in both cores and tpr based 14c ages recovered from lake bosten we further tested our age models by comparing carbonate based oxygen isotope 18o records from both lakes to an independently dated regional speleothem 18o record our results suggest if sedimentary sequences are densely dated and the re and the contribution of old carbon from detrital carbonates can be ascertained robust chronological frameworks based on carbonate based 14c determinations can be established

alkalic parental magmas for chassignites detailed analysis of cumulate and melt inclusion assemblages in the chassignites provide important constraints on the nature of the melt trapped as inclusions in cumulus olivine and by extension parental magma compositions the pressures of crystallization and magmatic volatile contents these mineral assemblages show strong similarities to the experimental fractionation assemblages that produce the sodic silica saturated alkalic lavas on earth e g ascension island azores the nandewar volcano of australia the experimental assemblages were produced from silica saturated hawaiite at pressures above 4 3 kbar with dissolved water contents above 0 5 wt such pressures are consistent with ti al ratios of the melt inclusion pyroxenes in the chassigny meteorite pyroxene compositions suggest early high crystallization temperatures and thus relatively low initial water and f contents feldspars indicate that melt evolution proceeded to rhyolite compositions both within the interstices of the cumulate olivine and within the melt inclusions even though rhyolitic glass is only found within olivine hosted polyphase melt inclusions the observed rhyolite glass is compositionally similar to the alkali rich rhyolite of ascension island which is produced experimentally by crystallization of hawaiite it is proposed that the melt trapped in cumulus olivine of the chassigny dunite was similar to a terrestrial silica saturated hawaiite while that trapped in olivine of the northwest africa nwa 2727 dunite was less evolved perhaps mildly alkalic basalt melts similar to terrestrial intra plate tholeiite could be parental to the cumulus minerals and evolve upon crystallization at pressures above 4 3 kbar and water contents above 0 4 wt to mildly alkalic basalt silica saturated hawaiite and alkali rich rhyolite the melt inclusion assemblages are inconsistent with either crystallization of a low al high fe basalt or low pressure crystallization of a terrestrial like tholeiite

quaternary environmental changes in the drylands of china a critical review abstract this paper reviews our current understanding of quaternary climate and landscape changes in the desert areas of northern china a key portion of the middle latitude drylands on earth combining earlier studies with our recent research and experience we offer a comprehensive picture of the state of chinese deserts during the quaternary and in the interest of enhancing future research identify knowledge gaps and areas of uncertainty lacustrine deposits found over an area ranging from china s western taklamakan desert to the eastern hunshandake sandy lands suggest that extensive lakes occurred in china s deserts during the pleistocene analysis of digital elevation models from srtm shuttle radar topography mission data supports this interpretation and shows the significant extent of these former lakes new estimates of mean annual evaporation of ca 1000 mm from lake surfaces and ca 100 mm from land surfaces confirms that local and regional rainfall is critical for maintenance of desert lakes in this temperate zone especially during intervals when the mean annual rainfall is more than 100 mm rapid shifts between sand seas and lakes in geologically and environmentally diverse settings suggest that the drylands of china are very sensitive ephemeral systems and not long lasting as previously thought available chronologies suggest that there were large lakes in the western taklamakan desert and the chadamu basin during mis marine isotope stage 3 at 30 ka probably related to a period of strong influence of northern hemispheric westerly winds channels and elevation models revealed by srtm data and remains of lacustrine sediments also indicate that there was a large lake in the hunshandake sandy lands in the eastern portion of the desert belt during the quaternary there is significant evidence that during the middle holocene strong summer monsoons led to a relatively large increase in moisture availability in the entire desert belt of northern china lacustrine records from the badain jaran desert in western inner mongolia suggest that it was generally dry before 10 cal ka becoming wetter from 10 to 4 cal ka and dry again afterwards study of palaeosols widely occurring in dune stratigraphy in the eastern portion of the desert belt suggests that there was a period of wet and warm climate in this region during the mid holocene optimum at a minimum between 6 ka and 4 ka but possibly lasting longer recent observations dealing with the generation and transport of dust from central asia indicate that the causal relationship between sand seas and loess sequences is not as close as previously assumed these results suggest that there is an urgent need to examine whether the frequency and amplitude of climatic variation in chinese deserts are somehow similar to that having occurred in the sahara desert of north africa deserts in northern china were also important focal regions for neolithic cultures during intervals when environmental conditions supported a denser vegetative cover there is evidence that some areas of woody vegetation to the west of badain jaran desert were deforested by humans by ca 4000 yr b p although it is still debatable whether humans have had a significant impact in other areas at that time opinions on the severity of desertification vary and are sometimes contradictory due to the lack of long term field based investigations

quantitative reconstruction of holocene millennial scale precipitation in the asian monsoon margin of northwest china revealed by phytolith assemblages from calcareous root tubes in the tengger desert the spatio temporal characteristics and driving mechanisms of the asian summer monsoon asm during the early and middle holocene remain unclear moreover the timing of maximum monsoon precipitation in the asian monsoon margin of northwest china during this period is also a subject of considerable debate herein we analyzed phytolith assemblages within 55 calcareous root tube crt samples from the hinterland of the tengger desert to quantitatively reconstruct holocene millennial scale precipitation changes and discuss the potential forcing mechanisms our results revealed that the mean annual precipitation map was 138 53 to 149 18 mm during 10 0 7 0 cal kyr bp 179 26 to 192 26 mm during 7 0 5 0 cal kyr bp and 129 20 to 161 13 mm during 5 0 1 0 cal kyr bp the quantitative reconstruction results suggested that precipitation in this area was low in the early holocene then increased to a maximum in the middle holocene 30 higher precipitation than present and gradually decreased in the late holocene maximum monsoon precipitation did not occur until the middle holocene in this area because the northernmost margin of the asm reached its northernmost latitude lagging behind its maximum monsoon intensity suppressed by high northern latitude ice volume forcing during the early holocene despite high summer insolation in addition to quantifying the holocene millennial scale precipitation changes in the northwestern margin of the asm this study also provides new evidence for spatial and temporal variations of the asm during the holocene

the role of climate and aeolian dust input in calcrete formation in volcanic islands lanzarote and fuerteventura spain calcretes are widely described in non marine settings with carbonates in their catchment or vicinity areas but in volcanic islands without carbonates in their substrate calcretes are not very common in lanzarote and fuerteventura canary islands characterized by impressive volcanic landscapes the sedimentary carbonate rocks are rare except for some recent marine and aeolian deposits in these settings very well developed calcretes cover large areas of the present landscape the source of calcium required for the formation of these calcretes has not been discussed in much detail till now although its role is critical to an understanding of the climatic conditions in which calcium was transported and fixed and of the calcrete formation processes the petrological and geochemical studies 87sr 86sr ratios 13c 18o major trace and ree carried out in this paper do confirm the important role of aeolian dust input in the formation of these calcretes canarian calcretes were mainly generated by pedogenic processes and are composed of various irregular carbonate lamina interbedded with fine clastic deposits our study indicates that these interbeddings were the result of several stages in which during dry periods aeolian dust deposition alternated with leaching and calcite precipitation during wetter periods when plants insects and bacteria played an important role in carbonate precipitation the 18o 2 70 to 2 22 vpdb and 13c 8 21 to 0 24 vpdb values indicate that calcretes were formed by pedogenic processes comparison of calculated 18o values for the canary calcretes with continental mid latitude calcrete values reflects the more homogeneous temperature regimes of calcrete formation in island oceanic settings calcrete87sr 86sr ratios 0 706357 to 0 709208 show strong affinity with those obtained in aeolian carbonate dust and marine deposits and are relatively different from those obtained in basalts ree major and trace element concentrations show that ca bearing minerals from volcanic host rock contributed little to calcrete formation and most of the calcium was supplied by aeolian deposits such as the aeolian dust coming from the sahara and sahel or sand dunes

los angeles a tale of two stones we compare and contrast the mineralogy and petrology of the 2 stones of the extremely ferroan and cr poor martian meteorite los angeles the 2 stones are similar in many characteristics strongly suggesting that they originated from a single flow or shallow intrusion however stone 2 is more ferroan and enriched in late stage materials than its larger and more widely studied sibling stone 2 has a far higher abundance 25 vol than stone 1 10 vol of combined opaques meaning not only conventional opaque minerals but also and more abundantly fine grained symplectitic intergrowths of fayalite ferroan augite silica interpreted as pyroxferroite breakdown material pbm the bulk composition of the pbm is close to that of stoichiometric pyroxferroite with roughly 45 wt feo extensive zonation within the pyroxenes of both stones is consistent with origin by closed system fractional crystallization of the parent basaltic melt s however the compositional and modal disparity between the two stones suggests that they formed in an environment where at least mild multi cm scale differentiation occurred probably in both stones crystallization began from similar melts with mg 27 28 mol but during crystallization significant migration of the melt component occurred perhaps by crystal settling and or filter pressing stone 2 acquired an enhanced proportion of residual melt and thus higher proportions of late stage materials such as pbm oxides and phosphates within the pbm clinopyroxene poikiloblastically encloses fayalite and silica at least some of the pbm had already formed by decomposition of pyroxferroite before the major shock that caused the very scarce brecciation within los angeles however the low abundance of fractures within pbm in comparison to pyroxene and some other minerals may be an indication that the textures of pbm regions typically did not assume their final detailed configuration until after the last major shock the steep slope of a pyroxene mg cr correlation suggests that igneous crystallization occurred at higher fo2 in los angeles than in otherwise similar shergottites such as que 94201 shergotty and zagami

ion microprobe measurements of 18o 16o ratios of phosphate minerals in the martian meteorites alh84001 and los angeles abstract oxygen isotope ratios of merrillite and chlorapatite in the martian meteorites alh84001 and los angeles have been measured by ion microprobe in multicollector mode 18o values of phosphate minerals measured in situ range from 3 to 6 and are similar to martian meteorite whole rock values as well as the 18o of igneous phosphate on earth these results suggest that the primary abiotic igneous phosphate reservoir on mars is similar in oxygen isotopic composition to the basaltic phosphate reservoir on earth this is an important first step in the characterization of martian phosphate reservoirs for the use of 18o of phosphate minerals as a biomarker for life on mars cumulative textural major element and isotopic evidence presented here suggest a primary igneous origin for the phosphates in los angeles and alh84001 textural and chemical evidence suggests that phosphates in alh84001 were subsequently shock melted in a later event

aeolian activity in the south margin of the tengger desert in northern china since the late glacial period revealed by luminescence chronology abstract aeolian sediments from deserts in northern china have been widely used in the study of aeolian sedimentology and its dynamic association with past climate conditions the tengger desert the fourth largest desert in china is sensitive to the waxing and waning of the asian monsoonal system previous attempts to date aeolian deposits in the tengger desert concentrated solely on local scales and only a limited number of dates have subsequently been made available accordingly past sand dune activity in this desert remains poorly understood the aim of this study was to conduct a detailed historical investigation of aeolian activity in this region since the late glacial period and potential forcing mechanisms that governed the desert s evolution for this purpose we collected and dated eighteen samples from different geological sections along a west east transect in the desert s southern margin using optically stimulated luminescence osl our results in combination with previous aeolian sediment chronologies show that sand dune accumulation occurred before 10 ka sandy loess developed between 10 and 6 ka when sand dunes stabilized as a result of increased effective moisture levels and sand dunes again mobilized from 3 ka onwards as a result of increased aridity findings indicate that aeolian activity at the southern margin of the tengger desert was closely associated with asian monsoon circulation moreover the transition between mobilization and stabilization of sand dunes demonstrates the significance of effective moisture which is influenced by both monsoon precipitation and local convection and evaporation effects interacting together to control aeolian activity

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

geochemical evidence for magmatic water within mars from pyroxenes in the shergotty meteorite observations of martian surface morphology have been used to argue that an ancient ocean once existed on mars1 it has been thought that significant quantities of such water could have been supplied to the martian surface through volcanic outgassing but this suggestion is contradicted by the low magmatic water content that is generally inferred from chemical analyses of igneous martian meteorites2 here however we report the distributions of trace elements within pyroxenes of the shergotty meteorite a basalt body ejected 175 million years ago from mars3 as well as hydrous and anhydrous crystallization experiments that together imply that water contents of pre eruptive magma on mars could have been up to 1 8 we found that in the shergotty meteorite the inner cores of pyroxene minerals which formed at depth in the martian crust are enriched in soluble trace elements when compared to the outer rims which crystallized on or near to the martian surface this implies that water was present in pyroxenes at depth but was largely lost as pyroxenes were carried to the surface during magma ascent we conclude that ascending magmas possibly delivered significant quantities of water to the martian surface in recent times reconciling geologic and petrologic constraints on the outgassing history of mars

water in the martian interior evidence for terrestrial morb mantle like volatile contents from hydroxyl rich apatite in olivine phyric shergottite nwa 6234 abstract understanding the distribution and behavior of volatiles in martian magmas and the corresponding mantle provides crucial constraints on planetary properties such as mantle melting temperatures and melt production as well as the availability of magmatic fluids for any potential occurrences of life current evaluations of the pre eruptive volatile concentrations of martian magmas are based on analyses of hydrous minerals in martian meteorites such as apatite because they record the volatile content oh f cl and the halogen and water fugacities of their parental magmas estimates for the pre eruptive volatile contents of martian basaltic magmas range from nearly anhydrous to 2 wt h2o however these magmas may have potentially degassed upon eruption and or emplacement losing their magmatic water while retaining some halogens here we report apatite compositional data from the martian meteorite nwa 6234 an intermediate olivine phyric shergottite and calculate f2 cl2 h2o fugacity ratios for its parental magma apatites in nwa 6234 contain the highest observed oh f content among martian meteorites and importantly have volatile fugacity ratios similar to terrestrial basalts this suggests that the actual content of fluorine chlorine and water of the martian mantle parental to snc meteorites are higher than previously thought and are similar to the volatile content of the terrestrial mid ocean ridge basalt source region

soils at the hyperarid margin the isotopic composition of soil carbonate from the atacama desert northern chile we evaluate the impact of exceptionally sparse plant cover 0 20 and rainfall 2 114 mm yr on the stable carbon and oxygen composition of soil carbonate along elevation transects in what is among the driest places on the planet the atacama desert in northern chile d 13 c and d 18 o values of carbonates from the atacama are the highest of any desert in the world d 13 c vpdb values from soil carbonate range from 8 2 at the wettest sites to 7 9 at the driest we measured plant composition and modeled respiration rates required to form these carbonate isotopic values using a modified version of the soil diffusion model of cerling 1984 earth planet sci lett 71 229 240 in which we assumed an exponential form of the soil co2 production function and relatively shallow 20 30 cm average production depths overall we find that respiration rates are the main predictor of the d 13 c value of soil carbonate in the atacama whereas the fraction c3 to c4 biomass at individual sites has a subordinate influence the high average d 13 c value 4 1 of carbonate from the driest study sites indicates it formed perhaps abiotically in the presence of pure atmospheric co2 d 18 o vpdb values from soil carbonate range from 5 9 at the wettest sites to 7 3 at the driest and show much less regular variation with elevation change than d 13 c values d 18 o values for soil carbonate predicted from local temperature and d 18 o values of rainfall values suggest that extreme 80 in some cases soil dewatering by evaporation occurs at most sites prior to carbonate formation the effects of evaporation compromise the use of d 18 o values from ancient soil carbonate to

reflections of surface water seasonality and climate in stable oxygen isotopes from tyrannosaurid tooth enamel abstract patterns of isotopic variation in enamel of eight albertosaurus teeth from the campanian maastrichtian horseshoe canyon formation alberta were measured by serial sampling along the growth axis cycles in the isotopic values appear to correlate to published tooth growth rates for tyrannosaurids tyrannosaurid dinosaur teeth of 50 mm in length provide ideal repositories of terrestrial climatic information as each records a full annual cycle of body water isotopic variation the relatively thin enamel precludes problems associated with time averaging associated with complex growth patterns found in thick mammalian enamel the most consistent and striking pattern associated with all of the teeth are two relatively closely spaced subequal maxima these appear to be associated with onset of a seasonal episode of high humidity after the activation of the amount effect where the influence of ambient temperature on surface water and body water 18 o ends while temperatures remain above 20 c teeth within a single fossiliferous horizon show the same general isotopic pattern and range a notable difference in pattern shape and magnitude of isotopic variation between tyrannosaurid teeth from several stratigraphic intervals of the lower horseshoe canyon formation section indicates a climatic changes from strong seasonality high annual temperature range with distinct precipitation and humidity maxima during each year at the base of the section to milder seasonality at the top

nd and sr isotopic characteristics of chinese deserts implications for the provenances of asian dust silicate nd sr isotopes of the fine grained fractions of the 10 major deserts and sandy lands in north china and the loess in chinese loess plateau were systematically investigated wide ranges in nd sr isotopic compositions have been observed the results of the 7 0 b the deserts on the northern margin of tibetan plateau with end 0 ranging from 11 9 to 7 4 and c the deserts on the ordos plateau with the lowest end 0 11 5 the distribution of the threes isotopic regions is controlled by the tectonic setting in north china which implies that the materials of the deserts are derived from the locally eroded rocks from the surrounding mountains and the nd sr isotopic signatures of these deserts could be quit stable over the past million years on the sub tectonic time scales if there is any desert at those times the nd sr isotopic compositions of the loess are mostly close to those of the deserts in isotopic region b suggesting that the main source regions of the last glacial loess in the chinese loess plateau are badain jaran desert tengger desert and qaidam desert also the comparison between the nd sr isotopes of the 5 lm silicate fractions of the deserts and the ancient dust falls in the north pacific and greenland show that the asian end members of these dust falls are derived most from the deserts in the isotopic region b and less from those in the isotopic region c

hydrological and climatic changes in deserts of china since the late pleistocene article i nfo article history large areas in western china were wetlands or less arid between 40 and 30 ka corresponding to the greatest lake period on the adjacent tibetan plateau during the last glacial maximum some of these western chinese deserts again experienced wetter conditions however at the same time the sandy lands in the eastern chinese desert belt experienced an activation of aeolian dunes while interpretations of the mid holocene environment in the deserts of china are controversial it is quite likely that it was more humid not only in the eastern areas influenced by monsoon climate systems but also in the western deserts where moisture is currently associated with westerlies evaluation of lacustrine records in the lakes recharged by dryland rivers and the complex interactions of these systems as well as other paleoenvironmental proxies such as the artemisia chenopodiaceae ratio should be interpreted with greater caution facing the highlighted uncertainties in our understanding of climate changes in chinese deserts it is hoped that this special issue will improve our knowledge considerably

partitioning behavior of chlorine and fluorine in the system apatite silicate melt fluid the partitioning behavior of cl among apatite mafic silicate melt and aqueous fluid and of f between apatite and melt have been determined in experiments conducted at 1066 to 1150 c and 199 205 mpa the value of dclapatite melt wt fraction of cl in apatite cl in melt 0 8 for silicate melt containing less than 3 8 wt cl at higher melt cl contents small increases in melt cl concentration are accompanied by large increases in apatite cl concentration forcing dclapatite melt to increase as well melt containing less than 3 8 cl coexists with water rich vapor that containing more cl coexists with saline fluid the salinity of which increases rapidly with small increases in melt cl content analogous to the dependency of apatite composition on melt cl content this behavior is due to the fact that the solubility of cl in silicate melt depends strongly on the composition of the melt particularly its mg ca fe and si contents once the melt becomes saturated in cl additional cl must be accommodated by coexisting fluid apatite or other phases rather than the melt itself because cl solubility depends on composition the cl concentration at which dclapatite melt and dclfluid melt begin to increase also depends on composition the experiments reveal that dfapatite melt 3 4 in contrast to cl the concentration of f in silicate melt is only weakly dependent on composition mainly on melt ca contents so dfapatite melt is constant for a wide range of composition the experimental data demonstrate that the fluids present in the waning stages of the solidification of the stillwater and bushveld complexes were highly saline the cl rich apatite in these bodies crystallized from interstitial melt with high cl f oh ratio the latter was generated by the combined processes of fractional crystallization and dehydration by its reaction with the relatively large mass of initially anhydrous pyroxene through which it percolated

millennial scale environmental changes in the asian monsoon margin during the holocene implicated by the lake evolution of huahai lake in the hexi corridor of northwest china the pattern of holocene environmental changes in the asian monsoon margin on a millennial timescale remains controversial based on lithological characteristics and sedimentological proxies we reconstructed holocene effective humidity changes and the lake evolution of huahai lake in the marginal area of the asian monsoon in the hexi corridor of nw china our results show that alluvial and aeolian deposition before 10 4 cal ka bp indicate an arid environment that lacustrine deposition from 10 4 to 8 8 cal ka bp indicates a transition from an arid to a humid environment and that lacustrine deposition from 8 8 to 5 5 cal ka bp occurred during the most humid conditions indicated by proxy records grain size carbonate toc and c n after 5 5 cal ka bp a depositional hiatus implicates an arid environment in the late holocene holocene environmental changes on millennial timescales in huahai lake imply that climate was arid to humid in the early holocene most humid in the mid holocene and arid in the late holocene these moisture changes were influenced by the asian monsoon particularly the transportation of water vapor by the indian monsoon in addition these moisture changes could have been affected by westerly winds that could have contributed to the water vapor supply to this region during the mid holocene the most humid conditions that occurred in the study area during the mid holocene may have been caused by strong westerlies and low levels of evaporation

using petrography and geochemistry to determine the origin and formation mechanism of calcitic plant molds rhizolith or tufa rhizoliths root casts and rhizocretions are prolific in the geologic record and their morphology and isotopic signatures can be important indicators of paleoenvironment and paleoclimate in a semiarid playa in nevada the calcite plant encrustations preserved at the playa surface resemble rhizoliths morphologically and would seem to indicate pedogenesis and root activity the features are preserved as short thin upright and or overturned tubes that often exhibit an apron at the base branching is rare and the tubes can be filled with sediment or calcite or left open however detailed macroscopic microscopic and geochemical analyses of these features reveal that they are instead macrophyte stem encrustations that form in standing water while these features form in a manner similar to paludal tufa they do not resemble typical tufa deposits e g barrages mounds cascades instead they mimic rhizoliths this study describes the macroscopic and microscopic characteristics of these features and distinguishes them from rhizoliths so that they can be accurately identified in the geologic record furthermore this study identifies a more appropriate method of interpreting the stable isotope values of these tufa like plant molds these types of carbonates are faithful recorders of ambient aquatic conditions e g geochemistry as well as local hydrologic parameters e g water depth when the playa surface is flooded but their geological application is restricted to a partial annual signal e g plant growing season presence of standing water on the playa it is important to correctly identify these types of plant encrustations in the geologic record since 1 their presence indicates a shallow standing body of water rather than a paleosol and 2 their isotopic composition records not only an ambient aquatic signal but an extremely restricted climatic signal that should not be interpreted with models for pedogenic carbonates

a holocene climatic record from arid northwestern china abstract the history of climatic changes during the interval 8500 3000 cal yr b p has been reconstructed from stratigraphical and chronological studies and the results of total organic carbon toc total inorganic carbon tic element composition pollen and stable isotope analyses of a section along the hongshui river in the southern tengger desert nw china the record suggests that from 8450 bottom of the studied section to 7500 yr b p the climate was characterized by instability from 7500 to 5070 yr b p the climatic conditions improved and can be divided into two parts a warm humid spell between 7290 and 6380 yr b p during which the average temperature was 3 4 c higher than that of today and a warm dry spell lasting from 5950 to 5720 yr b p the climate deteriorated between 6380 and 5950 yr b p from 5720 to 5070 yr b p the temperature decreased but humidity increased an abrupt temperature drop occurred between 5340 and 5290 yr b p that indicated the decline of the warmer and humid mid holocene climate from 5070 yr b p onward the climate oscillated significantly and there were three large temperature decreases coinciding with high mountain glacier advances between 5070 4670 yr b p 4300 3740 yr b p and 3410 3230 yr b p top of the section respectively the climatic fluctuations recorded in the southern tengger desert appear in phase with climatic changes recognized in the tibetan plateau suggesting that the period between 7290 and 6380 yr b p was the most warm humid spell one extremely dry event occurred at ca 3000 yr b p and subsequently the fluvial lacustrine depositional process terminated and wind action prevailed in the area both of these features can be attributed to the rapid strengthening and weakening of the summer monsoon circulation which are closely connected with global changes

indication of millennial scale moisture changes by the temporal distribution of holocene calcareous root tubes in the deserts of the alashan plateau northwest china abstract calcareous root tubes or rhizoliths have a strong potential for paleoenvironmental studies especially in reconstructing paleoenvironmental conditions and paleovegetation previous studies suggested that the effectivity of the moisture level affects the formation of calcareous root tubes in the deserts of the alashan plateau northwest china however it remains unclear whether the temporal distribution of calcareous root tubes can be used to reconstruct paleo effective moisture in this area in this study based on conventional 14c dating results of 34 holocene calcareous root tube samples collected from the badain jaran desert the tengger desert and the ulan buh desert in the alashan plateau of northwestern china millennial scale changes in paleo effective moisture during the holocene in this area were reconstructed the frequency of the 14c dating results demonstrates that 62 of the holocene samples were dated to 7 5 cal kyr bp and 38 of the holocene samples were dated to 4 2 cal kyr bp indicating an arid period during the early holocene before 8 0 cal kyr bp a humid period during the mid holocene 8 0 5 0 cal kyr bp and a humid to arid period during the late holocene after 5 0 cal kyr bp the reconstruction results were consistent with other previous reconstruction results from lake sediments and aeolian sand lacustrine sequences which indicated that temporal distribution of calcareous root tubes can reflect millennial scale changes in paleo effective moisture in this area however a single sample could indicate local environmental changes that may differ from the overall desert environmental changes hence the relatively humid environmental record obtained from the presence of calcareous root tubes is a local signal or a regional signal that should be noted

a high resolution absolute dated holocene and deglacial asian monsoon record from dongge cave china abstract we present a continuous record of the asian monsoon over the last 16 ka from 18o measurements of stalagmite calcite over 900 oxygen isotopic measurements providing information on shifts in monsoon precipitation are combined with a chronology from 45 precise 230th dates 18o and therefore asian monsoon intensity generally follows changes in insolation although changes in 18o are generally accommodated in abrupt shifts in contrast to smoothly varying insolation indicating that threshold effects may be important 18o decreased dramatically 3 at the start of the holocene 11 5 ka and remained low for 6 ka four positive 18o events centered at 11225 97 yr bp 1 05 10880 117 yr bp 1 15 9165 75 yr bp 1 4 and a double event centered at 8260 64 yr bp 1 1 and 8080 74 yr bp 1 0 punctuated this period of high monsoon intensity all four events correlate within error with climate changes in greenland ice cores thus the relationship between the asian monsoon and the north atlantic observed during the glacial period appears to continue into the early holocene in addition three of the four events correlate within error with outburst events from lake agassiz the decline of monsoon intensity in the mid late holocene is characterized by an abrupt positive shift in 18o which occurs at 3550 59 yr bp 1 1 in 100 yr in addition the holocene is punctuated by numerous centennial and multi decadal scale events amplitudes 0 5 to 1 up to half the amplitude of the glacial interstadial events seen in the last glacial period thus holocene centennial and multi decadal scale monsoon variability is significant although not as large as glacial millennial scale variability the monsoon shows a strong connection with northern south american hydrological changes related by changes in itcz position spectral analysis of the 18o record shows significant peaks at solar periodicities of 208 yr and 86 yr suggesting variation is influenced by solar forcing however there are numerous other significant peaks including peaks at el nino frequencies observed for high resolution portions of the record between 8110 and 8250 yr which suggest that changes in oceanic and atmospheric circulation patterns in addition to those forced by solar changes are important in controlling holocene monsoon climate in addition for this high resolution portion we observe a distinctive biennial oscillation of the asian monsoon which has been associated with the tropospheric biennial oscillation tbo

pedogenic carbonates as a proxy for palaeo co2 in the palaeozoic atmosphere abstract according to a model by cerling cerling t e 1991 carbon dioxide in the paleoatmosphere evidence from cenozoic and mesozoic paleosols am j sci 291 377 400 cerling t e 1999 stable carbon isotopes in palaeosol carbonates in thiry m simon coincon r eds palaeoweathering palaeosurfaces and related continental deposits vol 27 of spec publ int assoc sediment pp 43 60 the carbon isotope composition of calcretes should depend on the soil type and the co 2 concentration in the atmosphere we have tested cerling s model by investigating 14 palaeozoic sections with soil profiles a large number of carbonate types of different genetic origin exist in the localities examined comparing the palaeozoic samples with recent and subrecent calcretes it can be demonstrated that anhedral cryptocrystalline 2 concentration

martian magmas contained abundant chlorine but little water the martian water cycle a key for the habitability of mars largely relies on the abundance of water in martian magmas and their mantle sources yet martian snc shergottite nakhlite and chassigny classes meteorites contain minimal water however some experimental studies have suggested that martian parental magmas contained as much as 2 h2o here we integrate mineral chemical experimental and cosmochemical constraints to show that martian magmas contained little water but abundant chlorine apatite and amphibole in martian meteorites are chlorine rich and water poor this constrains the chlorine contents in their parental magmas to 0 3 wt and water contents to 0 3 wt our experimental work has shown that large amounts of water are not needed to explain the mineralogy of the martian meteorites because chlorine has effects similar to those of water on crystallization such chlorine rich water poor martian magmas are consistent with mars being chlorine rich 2 5 compared with the earth furthermore the bulk cl composition of martian meteorites shows that they have not preferentially lost cl by degassing of an h2o rich vapor together these results show that chlorine not water was the dominant volatile species in martian basalts and that these basalts contributed little h2o to mars surface environment

reconstructing the response of c3 and c4 plants to decadal scale climate change during the late pleistocene in southern illinois using isotopic analyses of calcified rootlets abstract the 13c and 18o values of well preserved carbonate rhizoliths crs provide detailed insights into changes in the abundance of c3 and c4 plants in response to approximately decadal scale changes in growing season climate we performed stable isotope analyses on 35 40 crs sampled at 1 cm intervals from an 18 cm thick paleosol formed in southern illinois during wisconsin interstadial 2 minimum 13c values show little variation with depth whereas maximum values vary dramatically and average values show noticeable variability maximum 18o values vary less than the minimum 18o values these findings indicate that a diverse and stable c3 flora with a limited number of c4 grass species prevailed during this interval and suggest that the maximum growing season temperatures were relatively stable but minimum growing season temperatures varied considerably two general patterns characterize the relationships between the 13c and 18o values obtained from the 1 cm samples in some cases low 13c values correspond to low 18o values and high 13c values correspond to high 18o values suggesting that cooler growing season temperatures favored c3 and warmer growing season temperatures favored c4 plants in other cases low 13c values correspond to high 18o values likely suggesting that wetter growing season conditions were favorable to c3 plants the high density of well preserved crs in this paleosol provides a unique opportunity to study detailed ecological responses to high resolution variability in growing season climate