advances in global bioavailable strontium isoscapes abstract strontium isotope ratios 87sr 86sr are a popular tool in provenance applications in archeology forensics paleoecology and environmental sciences using bioavailable 87sr 86sr in provenance studies requires comparing the 87sr 86sr of a sample of interest to that of 87sr 86sr baselines historically these baselines required building empirical datasets from plants or local animals to characterize the 87sr 86sr available to local ecosystems bioavailable 87sr 86sr however researchers are increasingly relying on modeled bioavailable 87sr 86sr maps called isoscapes we review the advantages and limitations of existing approaches to mapping bioavailable 87sr 86sr for provenance studies and propose a globally applicable scalable and editable framework for creating bioavailable 87sr 86sr isoscapes this framework relies on 1 compiling global bioavailable 87sr 86sr data 2 mapping 87sr 86sr variability in rocks 3 leveraging global environmental covariates and 4 applying a random forest regression method that integrates these data to predict bioavailable 87sr 86sr when the random forest model is applied at the global scale it performs well explaining 60 of the variance of the global bioavailable 87sr 86sr dataset and accounts for geological geomorphological and atmospheric controls in data rich regions e g europe the global bioavailable 87sr 86sr isoscape can be successfully extrapolated to broad regions without bioavailable 87sr 86sr data however we also show that this extrapolation may not be valid in exceptionally geologically complex and data poor regions e g madagascar we suggest research directions to improve the accuracy of global bioavailable 87sr 86sr isoscapes which include 1 increasing the collection of bioavailable datasets in data poor regions 2 harmonizing data management practices and metadata collection for bioavailable 87sr 86sr data and 3 relying on advances in remote sensing and geological mapping techniques to improve geological covariates while significant potential to refine 87sr 86sr isoscapes remains the data products provided in this review form a basis for using 87sr 86sr data in large scale provenance studies opening new research avenues in a range of fields

low to medium temperature phase equilibria in a gas of solar composition equilibrium mineral assemblages in a gas of solar composition have been calculated in the temperature and pressure ranges of 423 1023 k and 1 to 10 8 bar respectively the results include the modal percent variation of all condensates and the chemical compositions of ideal and non ideal coexisting solid solutions the major mineral assemblage stable over most of the pressure and temperature field is and fe ni alloys olivine orthopyroxene clinopyroxene plagioclase ilmenite other minerals entering the field are orthoclase at 628 k and troilite fes at 621 k both with no effect of variation in pressure rutile is stable in parts of the high temperature field a typical model percent composition above 621 k is fe ni 2 46 fe ni 40 26 olivine 28 94 orthopyroxene 18 25 clinopyroxene 6 26 plagioclase 3 56 and ilmenite 0 27 t 663 k p 10 4 bar below 621 k there is a marked drop in the average density of the material a small amount of almandine rich garnet appears at 533 k the temperature of appearance decreasing slightly with decreasing pressure at low temperatures biotite tremolite and talc are stable at high pressures while graphite becomes important below 10 7 bar compositions of plagioclase olivine orthopyroxene ilmenite and garnet are found to be potential cosmobarometers and cosmothermometers

pedogenic origin of dolomite in a basaltic weathering profile kohala peninsula hawaii we document stoichiometric dolomite occurring in a nonsaline quaternary soil on the kohala peninsula northwestern hawaii geologic constraints and geochemical and isotopic data confirm that this dolomite is not the result of marine influence or wind blown dust the strontium isotopic composition of the dolomite 87sr 87sr 0 7045 0 7048 is indicative of its derivation primarily from the weathering of basaltic parent material rather than from meteoric water or seawater infiltration of soil waters with elevated mg ca 1 derived from alteration of ferromagnesian minerals such as olivine likely led to dolomitization of early precipitated soil calcite and or to direct dolomite precipitation in the profile this demonstrates that well ordered dolomite can form in a nonmarine environment at temperatures 100 c without undergoing burial diagenesis

contrasting styles of explosive eruption at sete cidades sao miguel azores in the last 5000 years hazard implications from modelling abstract the deposits of three eruptions in the last 5000 years are described in detail in order to constrain eruptive parameters and allow a quantitative assessment of the hazard from a range of explosive eruption types at sete cidades volcano sao miguel azores these deposits include the caldeira seca eruption p17 which occurred around 600 yr bp which was the last explosive event from inside the sete cidades caldera the p11 eruption dated at 2220 70 yr bp and the undated p8 eruption our studies reveal that the caldeira seca eruption p17 produced ash rich deposits probably as the result of hydromagmatic eruptions and several lapilli fall layers dispersed in different directions the lapilli fall layers were derived from eruption columns up to10 km high evidence indicates pyroclastic density currents pdcs only moved outside of the caldera on to the western flank the p11 deposit represents one of the largest eruptions at sete cidades in the last 5000 years the deposits are composed of two units the main lower one is a lapilli fall deposit inferred to be derived from an eruption column 18 km high evidence for pdcs outside of the caldera occurs to the southeast and northwest the p8 deposits are composed of numerous alternating lapilli and ash layers representing a highly pulsatory eruption almost all of which are of a fallout origin the lapilli are inferred to be derived from eruption columns up to 8 km in height using the eruptive parameters derived from these deposits we use hazmap macedonio g costa a longo a 2005 a computer model for volcanic ash fallout and assessment of subsequent hazard comput geosci 31 837 845 to constrain the probability of fallout of different loads and thicknesses two end member scenarios were used with hazmap one representing a p17 eruption and another representing a p11 eruption both scenarios use wind profile data averaged over 25 years for a p17 type event there is a 5 chance of tephra fallout exceeding 15 cm thickness in ponta delgada the capital of sao miguel indicating that roof collapse associated with such an event is unlikely the larger magnitude and higher intensity p11 type eruption provides a 5 probability that tephra loads thicknesses would exceed 92 cm in ponta delgada and that roof collapse could be a major problem to assess the distribution of pdcs from future eruptions we use a gis application of the energy line model toyos g cole p d felpeto a marti j 2006 a gis based methodology for hazard mapping of small volume pyroclastic density currents nat hazards 41 99 112 the model indicates that individual pdcs of up to 10 7 m 3 derived from a vent located centrally within the caldera and a fountain collapse height of 500 m above the caldera floor could be completely contained within the caldera however pdcs derived from a vent located at caldeira seca in the western part of the caldera show individual pdcs 10 5 m 3 would travel out of the caldera and down the western flank as the vent location from a future eruption within the sete cidades caldera is unknown the hazard from pdcs is high for anywhere on the immediate flanks of the volcano

oxygen isotopic heterogeneities their petrological correlations and implications for melt origins of chondrules in unequilibrated ordinary chondrites abstract ten whole chondrules separated from the dhajala h3 4 hallingeberg l3 and semarkona ll3 chondrites were individually analyzed for bulk element composition by instrumental neutron activation with half of each chondrule subsequently sacrificed for oxygen isotopic analysis and half retained for petrographic and electron microprobe analysis on a three isotope plot 17 o vs 18 o the chondrules neither cluster near their respective chondrite hosts nor in the vicinities of previously recognized chondrite group averages instead they define a trend resolvable into mixing and fractionation components but dominated by mixing in a manner similar to that previously observed for clasts from the ll3 chondrite alha76004 covariations of chondrule isotopic mixing and fractionation parameters with petrological parameters were sought by two variable linear least squares regression analyses however the only two isotopic petrological correlations significant at the 95 confidence level were 17 o vs total bulk fe r 0 68 and mixing parameter m 18 vs bulk weight ratio cao al 2 o 3 mgo r 0 67 other correlations of apparent statistical significance were found by treating the chondrules as separate porphyritic 3 porphyritic olivine pyroxene 1 porphyritic olivine 1 barred olivine and non porphyritic 4 radial pyroxene 1 granular pyroxene cryptocrystalline textural subgroups the reliability of the trends based on so few samples is not clear but the results at least indicate that possible existence of distinct isotopic petrological subgroups of chondrules should be further investigated absence of certain isotopic petrological trends expected as condensation effects argues against direct nebular condensation as the dominant process of chondrule formation instead a model involving melting of heterogeneous solids followed by various degrees of liquid gas exchange is favored in any case chondrule oxygen isotopic evolution was dominated by two component mixing fractional vaporization was at most a second order effect in addition to chondrules parent bodies of unequilibrated ordinary chondrites must have also incorporated a 16 o rich component which might have been fine grained matrix

mineralogical evidence for eolian contribution to soils of late quaternary moraines wind river mountains wyoming usa abstract volcanic heavy minerals are found in the a and b horizons of soils on moraines of the western wind river mountains of wyoming volcanic minerals do not occur in the underlying moraine sediments derived from plutonic and metamorphic bedrock sources of the volcanics are the sedimentary rocks of the green river basin the presence of volcanic minerals in the green river basin and their patterns of distribution in the moraine soils indicate eolian sedimentation is an important factor of soil genesis in this region moraines affected by eolian sediments include the pinedale and temple lake indian basin type localities the presence of eolian sediments in both pinedale and holocene deposits suggests eolian addition is not simply a late glacial phenomenon but continues throughout postglacial time relations between eolian sediments and soil development must be accounted for when comparing soil development on moraine chronosequences in this and possibly all alpine regions of western north america

refractory precursor components of semarkona chondrules and the fractionation of refractory elements among chondrites abstract chondrules from the semarkona ll3 0 chondrite show refractory and common lithophile fractionation trends similar to those observed among the chondrite groups it appears that chondrules are mixtures of a small number of pre existing solid components and we infer that chondrule precursor materials were related to the nebular components involved in the lithophile element fractionations recognized in ordinary chondrites compositional trends among the chondrules can be used to deduce the compositions of these components we use instrumental neutron activation analysis to measure many 20 of the lithophile elements in 30 chondrules the amounts of oxidized iron were calculated from other compositional parameters concentrations of si were estimated using mass balance considerations the data were corrected for the diluting effects of non lithophile constituents plots of lithophile elements versus a reference refractory element such as al show that there were two major chondrule silicate precursor components a refractory olivine rich feo free one and a non refractory sio 2 feo rich one the refractory component probably forms from olivine enriched condensates formed above the condensation temperature of enstatite the non refractory component must have formed from fine grained materials that were able to equilibrate down to lower nebular temperatures chondrite matrix may have had an origin similar to that of the non refractory material and constitutes a third lithophile bearing component that took part in chondrite fractionation processes the low abundance of refractories and mg in ordinary and enstatite chondrites was produced by the loss of materials having a higher refractory element mg ratio than that in the refractory component of chondrules

origin of chondrule rims and interchondrule matrices in unequilibrated ordinary chondrites optical microscopy electron probe microanalysis scanning electron microscopy and analytical transmission electron microscopy were used to study the interchondrule matrix and opaque chondrule rims in bishunpur krymka semarkona chainpur all ll3 tieschitz and sharps both h3 the size distribution of grains in matrix in bishunpur obeys a power law rims around chondrules tend to be finer grained than matrix and may be layered all rims and matrices studied contain clasts of forsteritic olivine and low ca pyroxene in bishunpur the clasts may be cemented by amorphous glue rich in normative albite and partly altered to smectite rims in krymka sharps chainpur and tieschitz have a densely packed olivine groundmass with a grain size of about 0 1 m in krymka groundmass olivine is fo20 30 and forms interlocking dendrites various fe oxides are present in rims and matrices grain size distribution and chemical data indicate that clastic olivines and pyroxenes are derived from chondrules from analyses matrices rims in the ll group apparently are enriched in a feldspathic component tieschitz rims are slightly enriched but here the feldspathic component is present as white matrix sharps rims are not enriched in a feldspathic component opaque interchondrule matrices and chondrule rims probably formed from the products of fragmentation of chondrules partly induced by contraction of protopyroxene on inversion to clinopyroxene fragmented silica rich chondrule mesostases reacted with fe oxides and na to form the groundmass of fayalitic olivine and feldspathic glue a low temperature nebular or pre solar component is limited to 3 vol of each meteorite so equilibrium condensate was not the carrier of volatiles such as tl and bi

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

kinetics of diffusion controlled evaporation of fe mg olivine experimental study and implication for stability of fe rich olivine in the solar nebula abstract evaporation is a process that caused chemical fractionation in the solar nebula the evaporation rates of meteorite forming minerals and silicate melts are key parameters for constraining the timescale of high temperature processes in the early solar nebula and for understanding the mechanisms of cosmochemical fractionation the kinetics of evaporation of olivine initial fo 92 the most common silicate in meteorites was experimentally investigated at 1414 c for various duration under continuous evacuation the surface of olivine becomes more magnesian and the interior becomes zoned as evaporation proceeds indicating preferential evaporation of the fayalite fa component the weight loss surface composition and interior zoning profile were analyzed using a semi infinite one dimensional diffusion model with boundary migration and the controlling model parameters were optimized by fitting the experimental results the evaporation rate of olivine shows notable composition and orientation dependence as olivine becomes more magnesian the evaporation rates of the 100 010 and 001 surfaces decrease among which the rate at the 001 surface is greatest 1 0 m h at fo 91 8 which is about 2 orders of magnitude faster than that of pure synthetic forsterite the estimated fe mg fractionation factor shows anisotropy ranging from 0 017 to 0 035 which is significantly greater than the equilibrium value of the fe mg distribution coefficient between olivine and gas suggesting kinetic suppression of evaporation of the fa component the fe mg interdiffusion coefficient at 1414 c which also shows notable composition and orientation dependence is estimated to be 8 7 10 15 m2 sec along the c axis the results were applied to constrain the timescale of heating for a spherical fo50 olivine grain to retain the fa component olivine dust 1 m in diameter can retain 80 of the initial fa component for one minute in vacuum and for 30 min at 10 pa ph2 when heated at 1414 c therefore fo50 olivine in chondrite matrices could have survived an incipient heating event depending on the ambient hydrogen pressure if they were originally present in the solar nebula

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

empirical relationships between elevation and the stable isotope composition of precipitation and surface waters considerations for studies of paleoelevation change a compilation of 68 studies from throughout many of the world s mountain belts reveals an empirically consistent and linear relationship between change in elevation and change in the isotopic composition of precipitation along altitudinal transects the isotopic composition of precipitation decreases linearly with increasing elevation in most regions of the world except in the himalayas and at elevations 5000 m there are no significant differences in isotopic lapse rates from most regions of the world 0 28 permil 100 m except at the extreme latitudes where isotopic lapse rates are higher given information on past changes in the isotopic composition of precipitation preserved in pedogenic or authigenic minerals this global isotopic lapse rate can be used to place numerical constraints on the topo graphic development of some ancient mountain belts or plateaus there are many complicating factors that can confound interpretation of paleoel evation change based on stable isotopes and many of these are unique to specific mountain belts or time periods relevant to all stable isotope based paleoelevation change studies is the temperature dependent isotope fractionation between a pedo genic or authigenic mineral and the water from which it forms in cases where isotopic proxy minerals are sampled from localities where temperature will change simulta neously with elevation change the apparent change in the isotopic composition of precipitation may be dampened by several permil this suggests that samples taken from the rainshadow side of an emerging orographic barrier may be more likely to preserve isotopic changes resulting from mountain uplift than samples taken from atop a rising mountain range or plateau

reconstructing middle horizon mobility patterns on the coast of peru through strontium isotope analysis the pre columbian coastal site of ancon peru frequently has been interpreted as an important outpost of the highland wari empire inhabited by individuals from the sierra and the coast in order to test this hypothesis bone tooth pairs from 35 middle horizon 550 ad 1000 ad ancon skeletons were analyzed for strontium isotopes which vary by geologic provenance results indicate that 34 of the 35 individuals have 87 sr 86 sr enamel and bone values higher than ancon s biologically available strontium isotope range nitrogen and carbon isotope data from a subset of the ancon skeletons suggest that the higher than expected 87 sr 86 sr values among the ancon sample likely reflects a diet rich in marine resources rather than migratory activity and highlight the need to use multiple lines of evidence to track residence change at sites where individuals relied on resources other than locally grown terrestrial foods the one remaining individual a young female of elite status has an enamel strontium isotope signature much lower than the available data for local fauna and soil indicating that she was not raised locally her enamel 87 sr 86 sr ratio fits well within the range of strontium isotope values established for the inland wari site of conchopata tung t a knudson k j social identities and geographical origins of wari trophy heads from conchopata peru current anthropology in press and suggests that highland wari immigrants may have been present at ancon during the middle horizon

diatom inferred ecological responses of an oceanic lake system to volcanism and anthropogenic perturbations since 1290 ce abstract the impacts of natural and human induced processes on lake ecosystems in remote oceanic islands remain to be fully elucidated these lakes are excellent candidates to analyze the importance of anthropogenic vs natural forces driving lacustrine long term ecological evolution from previous pristine pre colonized conditions disentangling the effects of both is particularly relevant in highly active volcanic areas where catastrophic eruptions can act as an atypical natural driver altering the lake s long term ecological trajectories in this paper we study past ecological changes occurring in lake azul sao miguel island a crater lake from the remote azorean archipelago to address which were the main causes of its long term trophic history we analyzed diatom assemblages sedimentology and bulk organic matter of sediments deposited since ca 1290 ce when a huge local eruption occurred this episode drove the evolution of lake azul through six distinct phases commencing with a restart of ecological succession after tephra deposition disrupted biogeochemical cycling the alteration was so profound that the lake underwent a state of oligotrophic conditions for approx 650 yr nutrients were sourced by fish induced internal recycling and the overflow of the near lake verde during this period rather than by allochthonous nutrient inputs modulated by climate variability and or vegetation cover changes in the watershed after the official portuguese colonization it was only after recent artificial fertilization when the system overcame the volcanic induced long term resilience this over fertilization and a reduction in water turnover exacerbated the recent symptoms of eutrophication after 1990 ce contrary to other studies lake azul constitutes an uncommon case of long term resilience to trophic change induced by a cataclysmic volcanic eruption it brings new insights into the fate of lake ecosystems which might be affected by similar events in the future

strontium and carbon isotope tracers and the origins of soil carbonate in south australia and victoria abstract calcium carbonate occurs in soils in association with a variety of rock types in coastal and inland south australia and victoria the 87 sr 86 sr ratios of the coastal soil carbonates fall between 0 7094 and 0 7098 showing that the ocean is the principal source of calcium to nearly all soils near the coast and that contributions from bedrock are generally small an exception is the soil formed on the young volcano at mt gambier in which the average ratio for carbonate is about 0 7070 compared to 0 7041 for the volcanic ash the basaltic ash of the volcano is readily weathered and rich in calcium roughly 40 of strontium and 10 to 20 of the calcium in the soil carbonate derives from the ash and the balance from marine sources the 87 sr 86 sr ratios from soil carbonate gradually increase inland reaching values of 0 7152 these higher ratios reflect at least in part the increasing 87 sr 86 sr ratio of inland dust in contrast the ocean does not contribute significantly to the carbon pool of the soils we studied the 13 c pdb values of soil carbonates on kangaroo island and the higher rainfall areas of eastern victoria fall between 11 0 and 8 7 indicating that the carbonate formed in equilibrium with the c3 dominated vegetation typical of the region in the warmer inland areas to the north such as the eyre peninsula the 13 c value of soil carbonate averages 5 3 reflecting the higher proportion of c4 plants in the local biomass mixing with marine sources of carbonate cannot account for the observed carbon isotopic patterns the flux of carbon into soils from the ocean therefore must be small compared to that derived from plant respiration and decay

the mineral chemistry and origin of inclusion matrix and meteorite matrix in the allende cv3 chondrite the two textural varieties of olivine rich allende inclusions rimmed and unrimmed olivine aggregates consist primarily of a porous fine grained mafic constituent inclusion matrix that differs from the opaque meteorite matrix of cv3 chondrites by being relatively depleted in sulfides metal grains and perhaps carbonaceous material olivine is the most abundant mineral in allende inclusion matrix clinopyroxene nepheline sodalite and ti al pyroxene occur in lesser amounts olivine in unrimmed olivine aggregates type 1a inclusions is ferrous and has a narrow compositional range fo50 65 olivine in rimmed olivine aggregates type 1b inclusions is on average more magnesian with a wider compositional range fo53 96 olivine grains in the granular rims of type 1b inclusions are zoned with magnesian cores fo 80 and ferrous rinds fo 70 ferrous olivines fo 65 in both varieties of inclusions commonly contain significant amounts of al2o3 as much as 0 7 wt cao as much as 0 4 wt and tio2 as much as 0 2 wt refractory elements that probably occur in submicroscopic inclusions of ca al ti rich glass rather than in the olivine crystal structure defocussed beam analyses of allende matrix materials demonstrate that 1 inclusion matrix in type 1a inclusions is more enriched in olivine and feo than inclusion matrix in the cores of type 1b inclusions 2 opaque matrix materials are depleted in feldspathoids and enriched in sulfides and metal grains relative to inclusion matrix 3 the bulk compositions of type 1a and type 1b inclusions overlap and 4 excluding sulfides and metal the bulk compositions of allende matrix materials cluster in a complementary pattern around the bulk composition of c1 chondrites inclusion matrix and meteorite matrix in allende and other cv3 chondrites are probably relatively primitive nebular material but a careful evaluation of the equilibrium condensation model suggests that these matrix materials do not consist of crystalline phases that formed under equilibrium conditions in a relatively cool gas of solar composition allende inclusion matrix is interpreted as an aggregate of condensates that formed under relatively oxidizing non equilibrium conditions from supercooled supersaturated vapors produced during the vaporization of interstellar dust by aerodynamic drag heating in the solar nebula cv3 meteorite matrix contains in addition a proportion of interstellar material that was heated but not vaporized in the nebula granular olivine in rimmed olivine aggregates may have formed during the recrystallization and incipient melting of aggregates of inclusion matrix in the nebula the mineral chemistry of matrix olivine in allende seems to have been established by three different processes non equilibrium vapor solid condensation recrystallization and partial melting in the nebula and femg equilibration without textural homogenization in the meteorite parent body

processes affecting groundwater quality in arid zones the case of the bou areg coastal aquifer north morocco abstract the coastal aquifer of bou areg morocco has been studied to identify the main processes causing groundwater salinization using a multi tracer general chemistry and isotopes 2h 18o 13c 15nno3 18ono3 geochemical approach groundwater is characterized by the widespread occurrence of brackish waters tds no 3 reaching a maximum of 208 mg l 1 and cl lagoon samples represent a mixture of fresh water and sea water showing a na cl ratio in agreement with that of sea water and an excess of ca the high ca values represent the main peculiarity of the groundwater lagoon water system two types of groundwater could be identified i freshwater separated from the whole system and located at the limit of the irrigated area characterized by low tds depleted isotopic composition and relatively high quality and ii water mainly recharged by mountain runoff interacting with local recharge and acquiring salinity from different sources thus creating a complex system of dilute waters hydrochemical results confirm that the high salinity of the aquifer is caused by the coexistence of dissolution of evaporate rocks and carbonates from miocene strata water rock interaction and human impacts due to agricultural return flows the latter represents the main contribution to groundwater salinization especially in the central part of the aquifer as well as one of the main causes of the general increase in no 3 concentrations only locally in the southern part of the aquifer close to the city of kariat arkmane the high salinization observed may be attributed to the presence of lagoon water intrusion the isotopic composition of dissolved no 3 indicates manure and septic effluents especially in urban areas and in the central part of the plain and synthetic fertilizers in the agricultural zone as the main drivers for human induced pollution the study shows that agricultural return flow has significantly modified the chemistry of the system and it is a prime example of the human induced changes over coastal environments saline water intrusion from the lagoon in the shallow aquifer is negligible while discharge of polluted groundwater into the lagoon has been found to partially alter its quality

spatial variation of biologically available strontium isotopes 87sr 86sr in an archipelagic setting a case study from the caribbean this paper presents the results of strontium sr isotope analysis of modern and archaeological animal remains and modern plant samples from the caribbean region the goal is to assess if patterns of human mobility can be determined from the archaeological record in an archipelagic setting the range of variability and spatial distribution of biologically available strontium isotope signatures is reported and data evaluated to determine if sufficient heterogeneity exists to permit the identification of mobility despite the presence of potentially large contributions of marine strontium in island and coastal ecosystems the is landscape is divided into several sub regions based on the age and lithology of underlying geology and the variability of

climatic and lacustrine morphometric controls of diatom paleoproductivity in a tropical andean lake abstract the coupling of lake dynamics with catchment biogeochemistry is considered the key element controlling primary production in mountain lakes at time scales of a few decades to millennia yet little is known on the impacts of the morphometry of lakes throughout their ontogeny as lake chungara central andean altiplano northern chile experienced long term lake level fluctuations that strongly modified its area volume ratio it is an ideal system for exploring the relative roles that long term climatic shifts and lake morphometry play on biosiliceous lacustrine productivity in this paper we review previous data on the percent contents of total organic carbon total inorganic carbon total nitrogen total biogenic silica isotopic composition of organic matter carbonates and diatom frustules as well as data on the abundance of the chlorophycean botryococcus braunii in this lake for the period 12 400 1300 cal yr bp we also include new data on organic carbon and biogenic silica mass accumulation rates and the diatom assemblage composition of an offshore core dated using 14 c and u th biosiliceous productivity in lake chungara was influenced by shifts in allochthonous nutrient inputs related to variability in precipitation humid phases dated at approx 12 400 to 10 000 and 9600 to 7400 cal yr bp coincide with periods of elevated productivity whereas decreases in productivity were recorded during arid phases dated at approx 10 000 to 9600 and 7400 to 3550 cal yr bp andean mid holocene aridity period however morphometry related in lake controls led to a lack of a linear response of productivity to precipitation variability during the late glacial to early holocene lowstands facilitated complete water column mixing prompting episodic massive blooms of a large centric diatom cyclostephanos cf andinus thus moderate productivity could be maintained regardless of aridity by this phenomenon of morphometric eutrophy during the early history of the lake the subsequent net increase in lake level introduced modifications in the area of the epilimnion sediments versus the total volume of the epilimnion preventing complete overturn surpassing a certain depth threshold at approx 8300 cal yr bp caused cessation of the morphometric eutrophy conditions associated with cyclostephanos cf andinus superblooms after 7300 cal yr bp the lake experienced a decrease in biosiliceous productivity and a change of state that involved a stronger dependence on precipitation variability with a lesser contribution of diatoms to the total primary productivity our results show that the interpretation of lacustrine paleoproductivity records as paleoclimatic archives needs to take into account the effects of changes in the epilimnion sediment area to epilimnion volume ratio in association with lake ontogeny

high flying diatoms widespread dispersal of microorganisms in an explosive volcanic eruption explosive eruptions create a transient bridge between the solid earth and atmosphere frequently injecting volcanic aerosols to stratospheric levels although known to disrupt terrestrial and aquatic ecosystems at the surface the role of explosive volcanism in airborne transport of microscopic organisms has never been characterized this study documents abundant freshwater diatoms microskeletons of siliceous algae in widespread tephra from the 25 4 ka oruanui eruption of taupo volcano new zealand by matching the tephra hosted species assemblages to those in coerupted clasts of lacustrine sediment we demonstrate that 0 6 km 3 of diatom remains were incorporated during magma water interaction with a lake system overlying the vents and were dispersed along with fi ne ash particles hundreds of kilometers downwind one of the dominant species cyclostephanos novaezeelandiae is endemic to new zealand s north island and serves as a unique identifi er of the eruptive source region our results suggest that dispersal of microorganisms may be an overlooked feature of a number of ancient and modern eruptions and indicate a novel pathway of microbe transport in airborne volcanic plumes we conclude that the biogenic signatures contained within distal tephras have potential application in the characterization of eruption dynamics location and environmental settings of volcanic source areas

three dimensional modeling of lacustrine diatom habitat areas improving paleolimnological interpretation of planktic benthic ratios three dimensional modeling of lake morphometry enables the calculation of lake volume planar surface area and basin surface area which are critical components of a conceptual model of how planktic and benthic habitat areas change with changing lake level we have applied three dimensional modeling to foy lake montana and compared model results of changing ratios of planktic and benthic habitat areas at all possible lake levels to sediment cores recovered from the lake the model allows us to produce semiquantitative depth reconstructions and greatly improves lake level reconstruction of this morphometrically complex basin the conceptual model also was modified to examine the influence of resuspension versus gravity redistribution of diatomaceous material on the sedimentary record comparison of the model results with both long and short sedimentary records from foy lake montana suggests that planktic benthic ratios may be a better predictor of mean lake depth than maximum lake depth the model developed here is simple enough to be easily implemented has few requirements can be adapted to suit any lake basin and can be augmented to examine a variety of different lake processes that affect habitat availability

an evaluation of the diatom response to late quaternary environmental change in two lakes in the konya basin turkey by comparison with stable isotope data abstract in palaeolimnological studies of closed basin lakes diatoms provide an excellent source of palaeoclimate data owing to their sensitivity to salinity and lake level change one of the best ways of assessing the relationships between diatom species response salinity and lake level change is comparison with other proxy indicators such as stable isotopes the sensitivity of different lake systems to climate change changes in the ratio of precipitation to evapotranspiration depends to a large extent on the character of the basin hydrology here we compare evidence for late quaternary palaeohydrological change in two lakes which have contrasting groundwater hydrology located in close proximity to each other in the konya basin southern central turkey and whose sediment core chronologies show considerable overlap suleymanhaci golu has alternated between being hydrologically closed and open during its history and the diatom record shows clear evidence for changes in palaeoconductivity and lake level which correspond well to inferred changes in evaporative concentration during the late pleistocene and part of the holocene in contrast the diatom record of the karstic spring fed pool pinarbasi indicates that it remained fresh throughout the late pleistocene it is subject to major aquifer flow and behaves effectively as an open system in this case the complacency of the diatom record is important in allowing inferences on temperature effects to be drawn from relatively subtle shifts in stable isotope values

isotope domain mapping of 87sr 86sr biosphere variation on the isle of skye scotland abstract the potential of 87 sr 86 sr isotope composition for tracking and determining the origin of material whether it is humans animals water or wine can be fully realized only if high quality reference datasets are available against which to compare the unknowns this is currently not the case despite the rapid increase in 87 sr 86 sr based provenance studies of biosphere materials there are no well documented maps available most researchers resort to generating reference maps from a variety of geological datasets plus the analysis of sparse environmental9 samples a major reason for this lack of reference material is the investment needed to undertake systematic sampling and analysis over large areas a further problem is associated with the choice of proxy material as organisms differ in their habitat and exploitation of resources in this paper various approaches to isotope biosphere sampling are considered some of the problems are assessed the precision required for the study of human populations is discussed and a first attempt is made to condense all of the available information into an isotope package9 map the work is based on a study undertaken on the isle of skye in the inner hebrides and reduces the complexity of geological and isotope data into five main 87 sr 86 sr packages package 1 northern area 0 705 0 7092 package 2 ne coast 0 7082 0 7102 package 3 granitic rocks 0 716 0 720 package 4 metamorphic rocks 0 7092 0 7188 package 5 seawater 0 7092 0 005 2 the approach of trying to constrain the isotope composition of certain areas and or lithologies offers the possibility of extrapolating to other similar areas without having to sample at the original density

the influence of basin morphometry on the regional coherence of patterns of diatom inferred salinity in lakes of the northern great plains usa sedimentary diatom profiles from saline lakes are frequently used to reconstruct lakewater salinity as an indicator of drought however diatom inferred salinity di salinity reconstructions from geographically proximal sites in the great plains usa have yielded disparate results this study explores how physical changes in lake habitat resulting from drought may affect climate inferences from salinity reconstructions differences in relationships among drought lake level change and diatom community structure over the last century were examined for three saline lakes in the northern great plains with dissimilar di salinity records at each site models were developed relating available planktic benthic p b habitat area to lake level change and models were compared with instrumental drought records and fossil diatoms to understand how drought conditions were recorded in sedimentary diatom assemblages the degree to which di salinity tracked drought variation was affected by site specific physical characteristics that influenced the relationship between lake level change and p b habitat zonation within each lake moon lake showed the strongest correlation between drought and disalinity although this relationship was weaker during wetter conditions as highstands resulted in a larger influx of benthic diatoms at coldwater lake a dual basin system p b varied depending on lake level which apparently reduced the correlation between di salinity and drought at lake cochrane the simplest and freshest of the three basins the p b of fossil diatoms was a better proxy for drought than di salinity the integration of additional ecological characteristics into interpretations of paleoclimate records particularly for biologically based proxies may improve reconstructions of regional patterns of climate variation

primitive ultrafine matrix in ordinary chondrites abstract ultrafine matrix material has been concentrated by sieving and filtering disaggregated samples of six ordinary chondrites of different classes this component s holy smoke hs is enriched in both volatile e g na k zn sb and pb as well as refractory elements e g w and ree however the element ratios vary greatly among the different chondrites sem studies show that hs contains fragile crystals differing in composition and apparently in gross disequilibrium not only among themselves but also with the major mineral phases and consequently thermodynamic equilibration did not occur thus hs must have originated from impacting bodies and or was inherent in the primitive regolith subsequent impact brecciation and reheating appears to have altered to varying degrees the original composition of this ultrafine matrix material recent cosmic dust studies may indicate that hs still exists in the solar system survival of such delicate material must be considered in all theories for the origin of chondrites

strontium isotopes in trees as an indicator for calcium availability summary the increasing acidification and impoverishment of soil poses a great environmental problem today and in the future and is exemplified by the decreased availability of calcium in the soil pool unfortunately budgeting the inputs and outputs of calcium in the soil vegetation ecosystem is a very laborious task some of the fluxes are internal in the ecosystem and cannot be measured explicitely like weathering of primary minerals however since strontium and calcium exhibit similar geochemical behaviour it is possible to make an estimation of the calcium content in different media in the soil vegetation eco system using natural strontium isotopes preliminary analyses of water precipitation throughfall runoff soil water soil mineral matter and biological material trees mussel shells show that the use of the strontium isotope ratio 87 sr 86 sr is a powerful tool in estimating and understanding environmental changes

vegetation and landscape dynamics under natural and anthropogenic forcing on the azores islands a 700 year pollen record from the sao miguel island abstract the azores archipelago has provided significant clues to the ecological biogeographic and evolutionary knowledge of oceanic islands palaeoecological records are comparatively scarce but they can provide relevant information on these subjects we report the palynological reconstruction of the vegetation and landscape dynamics of the sao miguel island before and after human settlement using the sediments of lake azul the landscape was dominated by dense laurisilvas of juniperus brevifolia and morella faya from ca 1280 ce to the official european establishment 1449 ce after this date the original forests were replaced by a complex of erica azorica myrsine africana forests shrublands and grassy meadows which remained until ca 1800 ce extractive forestry cereal cultivation rye maize wheat and animal husbandry progressed until another extensive deforestation ca 1774 ce followed by the large scale introduction 1845 ce of the exotic forest species cryptomeria japonica and pinus pinaster which shaped the present day landscape fire was a significant driver in these vegetation changes the lake levels experienced a progressive rise during the time interval studied reaching a maximum by ca 1778 1852 ce followed by a hydrological decline likely due to a combination of climatic and anthropogenic drivers our pollen record suggests that sao miguel were already settled by humans by ca 1287 ce approximately one century and a half prior to the official historically documented occupation of the archipelago the results of this study are compared with the few palynological records available from other azores islands pico and flores

gypsum speleothems in lava tubes from lanzarote canary islands ion sources and pathways abstract lava tubes from lanzarote island in the canary archipelago commonly show white speleothems that stand out from the black basaltic rock mineralogical analyses of the speleothems from el covon and chifletera lava tubes show that gypsum is the dominant mineral with minor amounts of halite speleothems composed of microcrystalline gypsum up to 150 m long are coatings globules or extensive white powder accumulations covering the tube floor those composed of macrocrystalline gypsum with millimetric size tabular and lenticular crystals are crusts and stalactites uranium series dating of speleothems show ages ranging from 6217 1644 yr to 40 039 4748 yr 34s and the 18o of gypsum speleothems 34s is 20 97 v cdt and 18o is 9 78 v smow is similar to that of sulphate dissolved in seawater 87sr 86sr from speleothems 0 708665 0 708976 suggests that the main source of ca is seawater but additional ca contributions from aeolian dust have reduced the sr isotope values these data support the idea that gypsum precipitates in the lava tube by evaporation of marine spray or solutions derived from marine spray two probable vias for ions input into the lava tube are considered 1 sea spray circulating through the lava tube 2 low frequency rain infiltration leaching the marine spray salts precipitated at the surface the constant supply of ions from sea spray air currents in the cave and the fast but partial evaporation due to the high relative humidity in the lava tube favours accumulation of major amounts of gypsum and subordinately halite scarcity of precipitation in the western canary islands prevents dissolution of gypsum speleothems

strontium isotope investigation of ungulate movement patterns on the pleistocene paleo agulhas plain of the greater cape floristic region south africa abstract middle stone age sites located within the greater cape floristic region on the south african southern coast have material culture with early evidence for key modern human behaviors such as projectile weaponry large animal hunting and symbolic behavior in order to interpret how and why these changes evolved it is necessary to understand their ecological context as it has direct relevance to foraging behavior during periods of lowered sea level a largely flat and vast expanse of land existed south of the modern coastline but it is now submerged by higher sea levels this exposed area the paleo agulhas plain likely created an ecological context unlike anything in the region today as evidenced by fossil assemblages dominated by migratory ungulates one hypothesis is that the paleo agulhas plain supported a migration ecosystem of large grazers driven by summer rainfall producing palatable forage during summer in the east and winter rainfall producing palatable forage during winter in the west alternatively ungulates may have been moving from the coastal plain in the south to the interior north of the cape fold mountains as observed for elephants in historic times in this study we assess ungulate movement patterns with inter and intra tooth enamel samples for strontium isotopes in fossil fauna from pinnacle point sites pp13b and pp30 to accomplish our goals we created a bioavailable 87sr 86sr isoscape for the region by collecting plants at 171 sampling sites and developing a geospatial model the strontium isotope results indicate that ungulates spent most of their time on the paleo agulhas plain and avoided dissected plain foothill and mountain habitats located more than about 15 km north of the modern coastline the results clearly exclude a north south coastal interior movement or migration pattern and cannot falsify the east west movements hypothesized in the south coast migration ecosystem hypothesis

magma evolution of the sete cidades volcano sao miguel azores the sete cidades volcano sao miguel azores is situated at the eastern end of the ultraslow spreading terceira rift axis the volcano comprises several dominantly basaltic pre caldera eruptions a trachytic caldera forming stage and a post caldera stage consisting of alternating trachytic and basaltic eruptions the post caldera flank lavas are more primitive 5 wt mgo than the pre caldera lavas implying extended fractional crystallization and longer crustal residence times for the pre caldera shield building lavas thermobarometric estimates show that the ascending alkali basaltic magmas stagnated and crystallized at the crust mantle boundary similar to 15 km depth whereas the more evolved magmas mainly fractionated in the upper crust similar to 3 km depth the caldera forming eruption was triggered by a basaltic injection into a shallow trachytic magma chamber lavas from all stages follow a single continuous liquid line of descent from alkali basalt to trachyte although slight differences in incompatible element e g ba nb la nb and sr isotope ratios imply some heterogeneity of the mantle source major and trace element data suggest similar partial melting processes throughout the evolution of the volcano slight geochemical differences between post and pre caldera stage lavas from the sete cidades volcanic system indicate a variation in the mantle source composition with time the oxygen fugacity increased from the pre caldera to the post caldera stage lavas probably as a result of the assimilation of crustal rocks this is supported by the presence of crustal xenoliths in the lavas of the flank vents the lavas from the sete cidades volcano generally have low sr isotope ratios however rocks from one post caldera vent on the western flank indicate mixing with magmas resembling the lavas from the neighbouring agua de pau volcano having higher sr isotope ratios the different magma sources at sete cidades and the adjacent agua de pau volcano imply that despite their close proximity there is only limited interaction between them

geochemical fluxes related to alteration of a subaerially exposed seamount nintoku seamount odp leg 197 site 1205 hole 1205a was drilled on nintoku seamount which lies in the midportion of the emperor seamount chain this seamount was emergent 56 myr ago but was submerged by 54 ma so the lavas have endured weathering in both subaerial and submarine environments we have studied the petrology mineralogy and geochemistry of intercalated altered basalts breccias and soil samples recovered at hole 1205a to quantify the chemical exchanges between the seamount and seawater and or meteoric fluids the secondary mineralogy is relatively uniform throughout the section and comprises smectite fe oxyhydroxides iddingsite and ca carbonates soils are composed of variably altered basaltic clasts in a matrix of kaolinite smectite and vermiculite with minor goethite hematite and magnetite throughout the basement section altered basalts breccias and soils are depleted in si mg ca na sr rb and ba and enriched in fe fe3 fet up to 1 18o up to 20 and 87sr 86sr ratios are strongly elevated relative to primary igneous values differences in the 87sr 86sr ratios define an upper alteration zone with 87sr 86sr close to 56 ma seawater 0 7077 from a lower alteration zone where 87sr 86sr are less elevated 0 704 the lower alteration zone likely reflects interaction with a subaerial oxidizing fluid at low temperature this zone probably retained most of the original subaerial weathering signature the upper alteration zone was altered through circulation of large quantities of cold oxidizing seawater that partially overprinted the subaerial weathering chemical characteristics altered samples were compared to estimated protolith compositions to calculate chemical gains and losses global chemical fluxes are calculated for the entire basement section using different lithological proportions models and different rates of oceanic island emplacement although the global construction rate of ocean islands is small compared to igneous accretion at mid ocean ridges the magnitude of the chemical changes indicates that ocean islands and seamounts may be a significant contributor to the chemical budget of the oceans

the sensitivity of a tanzanian crater lake to catastrophic tephra input and four millennia of climate change diatom genera in many large east african lakes change little throughout the holocene period suggesting relatively stable ecological conditions and some resilience to environmental change ecosystem stability is less common in smaller more sensitive lakes such as those within volcanic craters where external impacts can cause abrupt and rapid fluctuations a 4100 year diatom and cyanobacteria pigment record from lake massoko a volcanic crater lake in southern tanzania is used to illustrate important switches in resource ratios following tephra deposition 1190 years ago it is hypothesized that the tephra reduced the rate of p diffusion from the sediments and increased the si p ratio in the lake a period of acute change in planktonic diatom communities resulted from the tephra impact and lasted c 110 years the magnitude of the change shown by the diatoms and their slow recovery from the tephra may be due in part to a coincident fall in lake level caused by a reduction in regional rainfall the statistical significance of the tephra impact relative to that of catchment and climate change has been tested using variance partitioning and rate of change analysis multiproxy indicators show an important period of positive water balance 1700 ago and a relatively dry episode persisting between 1000 and 400 years ago the lake ecosystem is shown to be highly sensitive to both climate change and tephra deposition

the matrices of unequilibrated ordinary chondrites implications for the origin and history of chondrites abstract the matrices of sixteen unequilibrated ordinary chondrites all witnessed falls were studied microscopically in transmitted and reflected light and analyzed by electron microprobe selected specimens were also studied by scanning electron microscopy these studies indicate that the fine grained opaque silicate matrix of type 3 unequilibrated chondrites is compositionally mineralogically and texturally distinct from the chondrules and chondrule fragments and may be the low temperature condensate proposed by larimer and anders 1967 1970 examination of the matrices of unequilibrated chondrites also shows that each meteorite has been metamorphosed with the alteration ranging in intensity from quite mild where the matrix has been only slightly altered to a more severe metamorphism that has completely recrystallized the opaque matrix most of the metamorphic changes in the matrix occurred without significant effects on the compositions or textures of the chondrules the metamorphic alteration probably resulted from a combination of processes including thermal metamorphism and the passage of shock waves the present appearance of each unequilibrated chondrite is a result of the particular temperature and pressure conditions under which it and its components formed plus the subsequent metamorphic alteration it experienced

spatial variations in biosphere 87sr 86sr in britain abstract strontium isotopes are a powerful tool for investigating the geographical origins of people and animals but assignment of provenance requires reference maps and databases this paper presents a map of strontium isotope variations across britain for use in archaeological and other studies and is produced by direct measurement of strontium isotope compositions of biosphere components predominantly plants the map characterizes the biosphere signature of specific lithologies a technique that is applicable worldwide marine derived strontium from both rainwater and coastal sea splash and spray is an important contribution to the british biosphere particularly on the western seaboard which is subject to high rainfall and prevailing westerly winds supplementary material methods full data table and full size version of figure 1b are available at http www geolsoc org uk sup18388

nature and origin of matrix in the unique type 3 chondrite kakangari the mineralogy and textural characteristics of fine grained matrix 1 m in the unique type 3 chondrite kakangari have been investigated by high resolution and analytical electron microscopy the matrix contains a diverse primary mineralogy dominated by enstatite and olivine with lesser amounts of albite anorthite cr spinel troilite and fe ni metal texturally the matrix is characterized by irregular clusters or aggregates of crystals which constitute distinct structural units within the matrix 2 8 m in diameter and frequently have distinct mineralogies enstatite in these clusters is an intergrowth of monoclinic and orthorhombic polymorphs with a microstructure indicative of an origin by high temperature inversion from protopyroxene during rapid cooling corroded inclusions of olivine frequently occur within enstatite suggesting that enstatite formed by reaction of olivine with a silica polymorph at high temperature the matrix mineralogy of kakangari formed by high temperature annealing and reaction of fine grained dust which probably consisted of amorphous or partially crystalline presolar or solar nebula condensates the constituents of kakangari matrix cannot therefore be considered as pristine unprocessed solar system material annealing probably occurred in a thermal event similar to that which formed the chondrules but the microstructures and textures of the matrix components suggest that melting did not occur chondrules in kakangari were probably formed from identical precursors to the matrix but reached temperatures sufficiently high to produce melting despite this high temperature processing the mineralogical clusters in the matrix preserve mineralogical and hence chemical heterogeneities in the precursor materials similar to those observed in interplanetary dust particles

diatom inferred aquatic impacts of the mid holocene eruption of mount mazama oregon high resolution diatom stratigraphies from mid holocene sediments taken from fringe and central locations in moss lake a small lake in the foothills of the cascade range washington have been analyzed to investigate the impacts and duration of tephra deposition on the aquatic ecosystem up to 50 mm of tephra was deposited from the climactic eruption of mount mazama 7958 7795 cal yr bp with coincident changes in the aquatic ecosystem the diatom response from both cores indicates a change in habitat type following blanket tephra deposition with a decline in tychoplanktonic fragilaria brevistriata and staurosira venter and epiphytic diatom taxa indicating a reduction in aquatic macrophyte abundance additionally the central core shows an increase in tychoplanktonic aulacoseira taxa interpreted as a response to increased silica availability following tephra deposition partial redundancy analysis however provides only limited evidence of direct effects from the tephra deposition and only from the central core but significant effects from underlying environmental changes associated with climatic and lake development processes the analyses highlight the importance of duplicate analyses fringe and central cores and vigorous statistical analyses for the robust evaluation of aquatic ecosystem change

isotopic evidence for eolian recycling of pedogenic carbonate and variations in carbonate dust sources throughout the southwest united states using isotopic ratios of sr c and o we trace calcium carbonate through surface systems across a wide region of semi arid terrain in arizona southwestern usa in order to evaluate the contribution of cations from silicate weathering to soil carbonate we present 87sr 86sr ratios of soil carbonate parent rock dry river course silts floodplain playa dust and rain samples as well as 18o and 13c values of selected samples results show that both parent rock and dust are important sources of cations for soil carbonate in this inland setting where bedrock is dominated by silicate lithologies dust in southeast arizona has higher 87sr 86sr ratios 0 7100 0 7123 than phanerozoic sea water 0 7070 0 7096 these high ratios derive ultimately from silicate rocks our 18o and 13c data show clearly that the dominant source of carbonate dust is eroded older soil carbonate not bedrock limestone because dust contributes significantly to newly forming soil carbonate some products of silicate weathering may reside in soil carbonate two or more times before being removed from the region and this recycling retards the rate at which the products of silicate weathering enter the sedimentary system comparison of the 87sr 86sr ratios of carbonate dust from southeast arizona with those from surrounding regions shows that dust 87sr 86sr ratios and by inference carbonate dust sources vary on a scale of 200 300 km in the southwest united states

the importance of sea spray to the cation budget of a coastal hawaiian soil a strontium isotope approach soil nutrients such as ca mg and k are traditionally thought to be derived primarily from rock weathering here we show that sea spray is a significant source of nutrient elements to modern and buried soils developed on 30 000 year old pahala ash deposits 50 m from the coast at south point hawaii the soil profiles evolved in a semi arid climate and have always been above sea level and the water table rhizoliths fossilized root traces and horizontal laminated carbonate sheets found in buried soils are composed of high mg calcite up to 14 mol mgco3 differences in strontium isotopic composition between marine aerosols 87sr 86sr 0 7092 and tephra parent material 0 7035 allow quantification of cation sources to the labile soil reservoir and to pedogenic carbonate mixing equations indicate that 50 80 of labile soil sr and approximately half of carbonate sr was derived from marine sources using the sr isotopic signatures and sr ca ratios of seawater and tephra as end members we determined that up to 2 3 of the ca in the labile reservoir and up to 1 3 of ca in the carbonates has a marine origin carbonate 87sr 86sr ratios are fairly constant with depth but labile 87sr 86sr ratios indicate decreasing sea spray aerosol influence with depth this trend could be due either to sequestering of aerosol derived sr in the upper part of the profile or to lower aerosol input in the past due to lower sea level the unusual occurrence of high mg pedogenic calcite probably results from high labile mg ca ratios during earlier stages of weathering coupled with rapid calcite precipitation during soil pore water evaporation

migration and viking dublin paleomobility and paleodiet through isotopic analyses abstract during the early medieval period in ireland dublin was established as the largest viking settlement on the island in the ninth century ad a previous biodistance study has suggested that the population of the town consisted of a polyethnic amalgam of immigrant and indigenous in this study we use biogeochemistry to investigate paleomobility and paleodiet in archeological human remains from the ninth to eleventh century levels at the sites at fishamble street ii national museum of ireland excavation number e172 fishamble street iii e190 and john s lane e173 as well as twelfth century remains from wood quay e132 through radiogenic strontium isotope stable oxygen carbon and nitrogen isotope and elemental concentration analyses we investigate the origins of the individuals who lived and died in early and late viking dublin mean archaeological human enamel and bone isotope values from dublin are 87 sr 86 sr 0 70975 0 00139 2 n 22 13 c carbonate v pdb 14 8 0 8 1 n 12 and 18 o carbonate v pdb 7 2 1 0 1 n 12 archaeological human bone samples exhibit mean 13 c collagen v pdb 20 8 0 5 1 n 12 and mean 15 n collagen air 10 0 1 7 1 n 12 comparing these data with archaeological faunal data from dublin and published data from northern europe we argue that there are no clear immigrants from other parts of the north atlantic although there is one clear outlier in both origins and diet overall the relative homogeneity in both paleomobility and paleodiet may support models of acculturation in viking dublin rather than a high number of first generation immigrants or continued migration from scandinavia

fayalite silica association in unequilibrated ordinary chondrites evidence for aqueous alteration on a parent body we report ten occurrences of high fayalite fa56 99 mol four with fa 82 mol olivine in association with silica in type 3 ordinary chondrites pyroxene with high fs contents is much less common fs contents do not exceed 66 mol and most maxima are 50 mol in those cases where the amount of fayalite is minor relative to that of silica the fayalite forms a layer on the silica and shows textural evidence of formation by reaction of silica with oxidized fe the latter seems to have resulted from reaction of metallic fe ni with an oxidant most likely h2o vapor the fayalite is generally in contact with pyroxene and in one case olivine having much lower fe fe mg ratios indicating that lattice diffusion has been minimal formation of fayalite from sio2 explains the low mg content of this olivine the mg was sequestered inside the lattices of mafic minerals and was thus inaccessible in contrast the moderately high mn contents of the fayalite indicate that an appreciable fraction of the mn in the precursor assemblage was accessible it was probably sited in the matrix in the form of tiny poorly crystallized oxide grains produced by nebular condensation at temperatures too low to permit diffusion into forsterite or enstatite the reaction of sio2 with feo produced by oxidation during metamorphism of fe ni can also account for fayalitic olivine associated with sio2 microspherules in the fine grained matrices of type 3 ordinary chondrites and because matrix is sio2 normative for other occurrences of fayalite in matrix the presence of mn in the fayalitic rims on the olivine of carbonaceous chondrites does not require a nebular origin

the first large scale bioavailable sr isotope map of china and its implication for provenance studies abstract strontium isotope ratio 87sr 86sr has been widely used to trace human migrations across geologically distinct landscapes in archaeological and forensic sciences 87sr 86sr based provenance studies require a detailed strontium reference map to make valid interpretations of mobility patterns for a given region in this study we first review the previous development for 87sr 86sr isoscapes relevant to research on migration and then present the first map of bioavailable 87sr 86sr ratios for china based on 1935 measurements on biosphere samples collated from published research and supplemented by our targeted collection strategy the results show that 87sr 86sr ratios in china span a large range and exhibit regional patterns largely dependent on the divergent geological conditions of each of china s tectonic blocks we further combine river water 87sr 86sr ratios with lithology integrated elemental data and chemical weathering rates to determine which dominant weathering patterns e g silicate carbonate or evaporite have the most significant influence on 87sr 86sr ratios the low ranges of 87sr 86sr ratios 0 7125 appear in the cathaysia block as well as some orogenic belts and the southeastern margin of the tibetan plateau likely due to the influence of the metamorphic rocks and granitoid sources additionally topography differential weathering among lithologies and eolian deposits e g loess are also significant factors that influence 87sr 86sr ratios in china our study reveals that the large variation of 87sr 86sr ratios across china is predominately driven by geological conditions revealing that future sr isotope provenance studies can shed on ancient and historical migrations in china

migration and mobility at the late lapita site of reber rakival sac watom island using isotope and trace element analysis a new insight into lapita interaction in the bismarck archipelago abstract this paper uses strontium isotope 87 sr 86 sr oxygen isotope 18 o and ba sr trace element data in archaeological tooth enamel samples to investigate migration and mobility at the late lapita site of sac watom island in the bismarck archipelago previous archaeological models have identified lapita mobility at a community level using obsidian distribution patterns and changes in ceramic design whereas isotope and trace element data can potentially reconstruct prehistoric mobility on an individual level human and pig teeth were sampled from sac and a selection of human teeth were included from the late post lapita site of lifafaesing tanga islands as a geographic geological comparison the results indicate that there is a large amount of isotopic variation in the bismarck archipelago which is useful for identifying non local individuals and possibly determining their origins one human individual and several pigs were suggested as coming from elsewhere in the region three potentially separate locations were identified for the non local pigs it is argued using the data from sac that late lapita communities in the bismarck archipelago were more mobile than previously assumed the potential for identifying individual migrants in a lapita context are discussed in terms of assessing the more subtle aspects of lapita society in the southwest pacific islands

the geographic distribution of sr isotopes from surface waters and soil extracts over the island of bornholm denmark a base for provenance studies in archaeology and agriculture abstract in this paper we report the sr isotope signatures and sr al and na concentrations of 30 surface waters lakes ponds and rivers creeks and 19 soil sample extracts from the island of bornholm denmark and present a categorized 87 sr 86 sr value distribution map that may serve as a base for provenance studies including archaeological migration and authenticity proof for particular food products the sr isotopic compositions of surface waters range from 87 sr 86 sr 0 7097 0 7281 average 0 7175 0 0049 1 whereas 0 1 m hno 3 0 05 m hno 3 and 0 01 m cacl 2 soil extracts range from 87 sr 86 sr 0 7095 0 7197 and define somewhat lower but statistically indistinguishable averages of 0 7125 0 003 1s these compositions are lower than the values expected from the precambrian granitoid basement 87 sr 86 sr 0 758 0 944 and from the overlying mainly clastic paleozoic sediments combined sr isotope composition vs sr na and al concentration relationships of soil extracts imply that lowering of the isotopic composition of leachable sr on bornholm results as a consequence of significant admixture to this fraction of sr deposited as marine salts aerosols and that rainwater only has a minor influence on the sr budget of the surface waters positively correlated al na and 1 sr vs 87 sr 86 sr relationships in soil extracts and surface waters indicate that the surface run off on bornholm is characterized by two predominant sources namely marine aerosols sea salts with high sr and low 87 sr 86 sr values and a source with lower sr delivering radiogenic sr to the surface waters which we equate with sr leached from the products of mineral weathering soils a feasibility study for using sr isotopic compositions of surface waters and soil extracts as a proxy for bioavailable sr signatures was performed with a few samples collected in the vicinity of the eleventh century ad ndr grodbygard cemetery site in sw bornholm from where sr isotope compositions of modern fauna samples and tooth enamel of humans buried in the cemetery have been reported waters and soil extracts studied herein from around this site range from 87 sr 86 sr 0 7104 0 7166 and correspond to sr compositions extracted from snail shells in this area which span a range of 87 sr 86 sr 0 7095 0 7160 some human tooth enamel is characterized by more radiogenic values 87 sr 86 sr up to 0 718 which points to a possible provenance of these humans from the granite gneiss terrain in the north of the island and or to immigration of these humans in their childhood from other places for example from mainland sweden to bornholm if the total compositional range of 87 sr 86 sr 0 709 0 718 n 44 recorded in human enamel from the ndr grodbygard site is considered representative for the variation of bioavailable sr on bornholm then our soil leachate and surface water data entirely covers this range we therefore propose that the combination of sr isotope analyses of surface waters and soil leachates are an easy fast and relatively cost efficient way to characterize a local bioavailable 87 sr 86 sr signature and consequently propose that the overall average of 87 sr 86 sr 0 7153 0 0048 1 n 50 can be taken as a band for bioavailable sr fractions suitable to discriminate between local and non local signatures in provenance studies in the field of archaeology and for food and plant authenticity control in agricultural applications

the last 5000 years of activity at sete cidades volcano sao miguel island azores implications for hazard assessment abstract sete cidades is a central volcano with a summit caldera at the western end of sao miguel island azores its stratigraphy comprises two main geological groups the inferior group the units of which date from more than 200 000 years ago through to 36 000 years before present consisting of thick lava flows and subaerial volcaniclastic deposits that built the base of the central volcano and the superior group which comprises all the activity from the last 36 000 years including pumice and scoria fallout and pdc deposits with minor lava flows the volcanostratigraphy is divided into six main formations risco ajuda bretanha lombas santa barbara and lagoas each defined by different activity phases in the volcano s evolution the present caldera developed in three phases associated with massive paroxysmal eruptions which occurred approximately 36 000 29 000 and 16 000 years before present since the last caldera forming event eruptive activity has been predominantly explosive and a variety of deposits have been produced by different eruptive styles associated with three specific settings 1 pumice fall deposits pyroclastic density currents and hydromagmatic events from eruptions inside the caldera 2 lava domes cinder cones and basaltic lava flows from eruptions on the volcano flanks 3 tuff ring and tuff deposits from surtseyan eruptions offshore the more recent history of the volcano is marked by a change in the intracaldera activity from dominantly magmatic behaviour to a hydromagmatic character which happened about 5000 years ago since then at least 15 basaltic subaerial and submarine eruptions have occurred on the volcano flanks and 17 trachytic s l explosive eruptions have occurred within the caldera the most recent of which took place about 700 years ago this eruptive frequency makes sete cidades probably the most active volcanic centre in the azores in this paper we present the stratigraphy and a description of the deposits which originate from the last 5000 years in order to delineate sete cidades recent eruptive history for the purpose of estimating the hazard associated with this volcano an event tree has been designed to systematize possible future eruptive scenarios and to aid the assessment of relative probabilities of occurrence of different potential eruptive styles the probabilities for all nodes on the event tree together with their associated uncertainties were obtained by expert elicitation providing results that accord with the geologic record these probability estimates indicate that 1 basaltic strombolian and submarine eruptions are the most likely to occur 2 trachytic activity from the central volcano magmatic system is more probable in the intracaldera environment than on the flanks and 3 explosive activity is more likely than effusive for the trachytic system worst case scenario and maximum expected events are identified according to the eruptive scenarios and their probabilities of occurrence

calcium in regolith carbonates of central and southern australia its source and implications for the global carbon cycle abstract the widespread regolith carbonates of the australian continent are a potential sink for co 2 we have used sr isotopes to investigate the source of the ca in regolith carbonates that cover approximately 1 6 10 6 km 2 of inland australia 87 sr 86 sr ratios for nearly all the carbonates were in the range 0 7094 to 0 7211 the results show that only about 10 of the ca in regolith carbonates is derived from weathered bedrock with the remaining component being derived from an external marine source the exceptions are the most northerly samples with a range of 0 7270 to 0 7374 in which bedrock content may be as high as 30 the likely ca source areas are sedimentary carbonates located on the continental shelf and calcareous aeolianites that surround much of the southern and western australian coastline winds passing over these carbonates continually rework and transport the material over the australian continent where it has settled and formed the regolith carbonates we see today the impact of this process is that despite the immense area covered australian regolith carbonates do not capture any additional co 2 instead the carbonate is simply being remobilised from one pool marine to another terrestrial

quantitative strontium isotope models for weathering pedogenesis and biogeochemical cycling abstract isotopes of strontium sr are a useful tracer for weathering atmospheric fluxes cation biocycling and pedogenesis we present basic models for application of strontium isotopes to the soil vegetation atmosphere system the mathematical formulations fall into the general categories of 1 steady state models in which isotopic ratios remain constant over the time scale of interest and 2 time dependent models in which isotope ratios change through time in the steady state models fluxes of sr and other elements to the system are constant steady state models can be used to infer short term weathering rates from river and stream isotope compositions to determine fluxes to a single or multiple layer soil exchange solution system and to quantify nutrient fluxes to vegetation time dependent models involve a change in isotopic ratio from some initial value to a new value over the time period of interest in some cases the change may represent a shift from one steady state situation to a new one after a shift in one or more of the fluxes feeding the system examples of applications of time dependent models include identifying the dominant cation sources to an evolving soil exchange solution system and calculating weathering rates by measuring the isotopic compositions of primary soil minerals we use time dependent models to explain differences in the isotopic ratios of labile and carbonate sr from arid sites in hawaii with a basalt parent material isotopic signature and new mexico with an atmospheric isotopic signature these models suggest that the difference is due to a combination of low atmospheric strontium fluxes and high weathering rates in the hawaiian profile compared to the new mexico calcrete profile

environmental history of a closed basin lake in the us great plains diatom response to variations in groundwater flow regimes over the last 8500 cal yr bp sediment records from closed basin lakes in the northern great plains ngp of north america have contributed significantly to our understanding of regional paleoclimatology a high resolution near decadal fossil diatom record from kettle lake nd usa that spans the last 8500 cal yr bp is interpreted in concert with percent abundance of aragonite in the sediment as an independent proxy of groundwater flow to the lake and thus lake water level kettle lake has been relatively fresh for the majority of the holocene likely because of the coarse substrata and a strong connection to the underlying aquifer interpretation of diatom assemblages in four groups indicative of low to high groundwater flow based on the percent of aragonite in sediments allow interpretations of arid periods and probable meromictic lake conditions that could not be detected based on diatom based salinity reconstructions alone at the centennial millennial scale the diatom record suggests humid wet periods from 8351 to 8088 4364 to 1406 and 872 to 620 cal yr bp with more arid periods intervening during the last 4500 years decadal centennial scale periods of drought have taken place despite the generally wetter climate these droughts appear to have had similar impacts on the kettle lake hydrology as the dust bowl era droughts but were longer in duration

lacustrine responses to tephra deposition examples from mexico one of the major problems with palaeoclimate investigations in volcanic regions is that tephra inputs to lakes can cause changes in proxies analogous to those of climate forcing we review the range of impacts thought to be associated with tephra deposition distinguishing between direct effects on lake ecosystems and indirect changes to catchment nutrient cycles to achieve better understanding of these complex responses we have used high resolution diatom analysis from around 17 tephra layers in three mexican lakes a positive response to the tephra inputs has been identified for over half of these layers the most common response was for diatom concentrations to increase after tephra deposition also in plankton dominated systems fragilaria spp replaced stephanodiscus spp and aulacoseira spp an increase in the supply of silica to the lakes through their catchments is probably the cause of the diatom changes in the lakes studied direct effects of the tephra inputs to these lakes can be excluded as they would not generate changes of sufficient longevity the impact of these tephras which lasted for several decades was insufficient to perturb the underlying long term climate forcing of these lake systems c 2004 elsevier ltd all rights reserved

comparing historic records of storm frequency and the north atlantic oscillation nao chronology for the azores region the storminess of the azores region was investigated using newspaper records from ad 1836 onwards the information obtained was rank ordered for intensity and the time series of storm frequency ana

using isotopes to determine the contribution of volcanic ash to sr and ca in stream waters and plants in a granite watershed mt tsukuba central japan strontium sr isotope ratios of soils stream water plants and atmospheric precipitation were used to trace calcium ca and to determine the influence of volcanic ash in soils on ca cycling in forest ecosystems in a small forested watershed on mt tsukuba central japan the 87sr 86sr ratios of soils on steep slopes and the valley floor ranged from 0 7110 to 0 7139 which indicates that the major source of sr was the granite substrate 87sr 86sr ratio 0 7120 0 7131 soils on a ridge had lower 87sr 86sr ratios 0 7068 0 7072 indicating that they were mainly composed of volcanic ash materials released around 30 000 years ago from mt akagi 0 7069 the 87sr 86sr ratio decreased and the concentrations of sr and ca increased in stream water with increased elevation from the valley bottom to the ridge indicating that volcanic ash was the dominant source of both cations in the upstream area the contributions of volcanic ash derived sr to upstream and downstream water were 50 and 0 1 respectively the 87sr 86sr ratios of plants were between those of the soils in which the plants were growing and those of atmospheric precipitation 0 7100 more than 74 of the sr in plants on the ridge but 17 in plants in the valley bottom was volcanic ash derived the origin of sr and thus ca in stream waters and plants varied depending on the volcanic ash content in soils which was significantly influenced by the site elevation

vegetation changes and human settlement of easter island during the last millennia a multiproxy study of the lake raraku sediments earlier palynological studies of lake sediments from easter island suggest that the island underwent a recent and abrupt replacement of palm dominated forests by grasslands interpreted as a deforestation by indigenous people however the available evidence is inconclusive due to the existence of extended hiatuses and ambiguous chronological frameworks in most of the sedimentary sequences studied this has given rise to an ongoing debate about the timing and causes of the assumed ecological degradation and cultural breakdown our multiproxy study of a core recovered from lake raraku highlights the vegetation dynamics and environmental shifts in the catchment and its surroundings during the late holocene the sequence contains shorter hiatuses than in previously recovered cores and provides a more continuous history of environmental changes the results show a long gradual and stepped landscape shift from palm dominated forests to grasslands this change started c 450 bc and lasted about two thousand years the presence of verbena litoralis a common weed which is associated with human activities in the pollen record the significant correlation between shifts in charcoal influx and the dominant pollen types suggest human disturbance of the vegetation therefore human settlement on the island occurred c 450 bc some 1500 years earlier than is assumed climate variability also exerted a major influence on environmental changes two sedimentary gaps in the record are interpreted as periods of droughts that could have prevented peat growth and favoured its erosion during the medieval climate anomaly and the little ice age respectively at c ad 1200 the water table rose and the former raraku mire turned into a shallow lake suggesting higher precipitation evaporation rates coeval with a cooler and wetter pan pacific ad 1300 event pollen and diatom records show large vegetation changes due to human activities c ad 1200 other recent vegetation changes also due to human activities entail the introduction of taxa e g psidium guajava eucalyptus sp and the disappearance of indigenous plants such as sophora toromiro during the two last centuries although the evidence is not conclusive the american origin of v litoralis re opens the debate about the possible role of amerindians in the human colonisation of easter island

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

pedogenesis soil mass balance phosphorus dynamics and vegetation communities across a holocene soil chronosequence in a super humid climate south westland new zealand abstract this study quantifies progressive pedogenesis under a super humid climate on the west coast of south island new zealand it focuses on soil morphology pedogenic oxides soil mass balance phosphorus transformation and linking pedogenesis trajectories to vegetation communities the study comprises a set of dune ridges of a coastal sand dune complex covered by unmodified conifer podocarp angiosperm forest the surface ages of the chronosequence range from 370 y to 6500 y rapid podzolisation is characteristic for the study area within 1000 y soils reach the spodosol stage with typical eluvial illuvial horizons and mobilisation of fe and al this period is also characterised by the most rapid losses of total phosphorus at a rate of 110 g m 2 ky 1 a relative loss of 41 beyond 3000 y changes in soil chemistry and losses for all nutrients markedly slow soil mass balance shows that the 6500 y soil has lost 75 total p 62 k 52 ca and 54 na soil p fractions substantially change across the gradient high leaching losses of apatite and non occluded p in the first hundreds of years coincide with accumulation of organic and occluded inorganic forms in the topsoil and subsoil which mitigate total p loss beyond 1000 y of pedogenesis all p fractions decline at similar rates to low more persistent levels with apatite non occluded p being the dominant p form after 6500 y of pedogenesis this incipient steady state is assumed to be sustained by the advection of parent material derived p through surface lowering and reduced biological cycling vegetation communities change from more diverse communities on young and less impoverished soils in the first 1000 y to less diverse and less variable communities beyond 1000 y of ecosystem development the soil evolution correlated vegetation changes documented in this study are consistent with general schemes of vegetation succession for the west coast of south island

matrices of type 3 ordinary chondrites primitive nebular records petrologic studies were made on the fine grained matrices of type 3 ordinary chondrites of the lowest petrologic subtype the matrix minerals in order of abundance are olivine fo99 to fo9 enstatite or bronzite augite or subcalcic augite albite fe ni metal troilite magnetite spinel mgal2o4 chromite and calcite fe and mg rich fluffy particles and albite like particles are also major constituents the chemical compositions of olivine and pyroxenes vary within and among the chondrites and are in gross disequilibrium showing that the matrix materials were hardly heated after their formation textural relationships indicate that magnesian olivine was formed after ca pyroxene followed by intermediate to iron rich olivine intermediate olivine was formed from enstatite and metallic iron under relatively oxidizing conditions the observations indicate that matrices of chondrites are neither the fragments of chondrules nor the precursors of chondrules they were mostly the products of condensation and reaction among solids and or between solids and the ambient gas mostly at low temperatures and thus they contain records of primitive processes in the nebula in order to explain the presence of olivines more iron rich than fo50 the presence of free sio2 or a high activity of sio2 in the gas is necessary which was not shown in previous thermochemical calculations mineral assemblages of matrix minerals of chondrites of different chemical groups differ systematically according to oxidation state of the parental meteorites indicating that they were formed at different oxygen fugacities the rims of chondrules and surrounding matrix materials must have accreted onto chondrules during turbulent movements of the nebula

ca sr and sr isotope systematics of a himalayan glacial chronosequence carbonate versus silicate weathering rates as a function of landscape surface age we explored changes in the relative importance of carbonate vs silicate weathering as a function of landscape surface age by examining the ca sr and sr isotope systematics of a glacial soil chronosequence located in the raikhot watershed within the himalaya of northern pakistan bedrock in the raikhot watershed primarily consists of silicate rock ca sr 0 20 mol nmol 87 sr 86 sr 0 77 to 1 2 with minor amounts of disseminated calcite ca sr 0 98 to 5 3 mol nmol 87 sr 86 sr 0 79 to 0 93 and metasedimentary carbonate ca sr 1 0 to 2 8 mol nmol 87 sr 86 sr 0 72 to 0 82 analysis of the exchangeable carbonate and silicate fractions of seven soil profiles ranging in age from 0 5 to 55 kyr revealed that carbonate dissolution provides more than 90 of the weathering derived ca and sr for at least 55 kyr after the exposure of rock surfaces even though carbonate represents only 1 0 wt of fresh glacial till the accumulation of carbonate bearing dust deposited on the surfaces of older landforms partly sustains the longevity of the carbonate weathering flux as the average landscape surface age in the raikhot watershed increases the ca sr and 87 sr 86 sr ratios released by carbonate weathering decrease from 3 6 to 0 20 mol nmol and 0 84 to 0 72 respectively the transition from high to low ca sr ratios during weathering appears to reflect the greater solubility of high ca sr ratio carbonate relative to low ca sr ratio carbonate these findings suggest that carbonate weathering controls the dissolved flux of sr emanating from stable himalayan landforms comprising mixed silicate and carbonate rock for tens of thousands of years after the mechanical exposure of rock surfaces to the weathering environment copyright 2002 elsevier science ltd

sources of strontium and calcium in desert soil and calcrete the carbon cycle significance of soil carbonate fluxes is subject to large uncertainties because it is not clear precisely how much calcium is derived from atmospheric sources compared with that from the chemical weathering of silicate minerals in the petrocalcic horizon calcrete of a pleistocene soil from the usda scs desert project area near las cruces nm approximately 1 5 g ca cm 3 has been added with an associated expansion of the profile of200 strontium isotope values for the labile cations and carbonate from the a b and k soil horizons have 87 sr 86 sr values that range from 0 7087 to 0 7093 similar to the values for easily soluble local dust and rain the parent material non calcareous camp rice alluvial sediment has a 87 sr 86 sr ratio of0 7165 mixing calculations indicate a minimum atmospheric contribution to soil carbonate calcium of 94 the more likely scenarios indicate at least 98 of the ca originated from atmospheric input the variations in 87 sr 86 sr ratios of soil silicate 0 7131 to 0 7173 are consistent with weathering of volcanogenic sediments and neoformation of clay minerals in the petrocalcic horizon moreover the sr isotope data suggest that 50 70 of silicate in the uppermost 25 cm of the profile could be atmosphere derived the isotopic composition of labile strontium in the a horizon and the mass distribution of silicon and calcium indicate that the uppermost portion of the profile is the present zone for the release of cations due to silicate weathering steady state models of the whole profile yield a sr weathering flux ranging from200 to 400 m gc m 2 ma 1 the results indicate that both the present day and long term contribution of calcium from silicate weathering is less than 2 of that supplied from the atmosphere and confirm that desert soil formation is not a significant sink for atmospheric carbon 1999 elsevier science b v all rights reserved

fayalitic olivine in matrix of the krymka ll3 1 chondrite vapor solid growth in the solar nebula fayalitic olivine fa54 94 is a ubiquitous component in the matrix of krymka ll3 1 as well as in other highly unequilibrated chondrites ordinary and carbonaceous in krymka the fayalitic olivine has an unusual anisotropic platy morphology that occurs in at least five types of textural settings that can be characterized as 1 isolated platelets 2 clusters of platelets 3 euhedral to subhedral crystals 4 overgrowths of platelets on forsteritic olivine and 5 fluffy porous aggregates from transmission electron microscope tem investigation the direction of elongation of the platy olivine overgrowths on forsteritic olivine substrates is along the c axis and in most cases it corresponds with the c axis of the substrate olivine which suggests that the fayalitic olivine grew in this unusual morphology and is not a replacement product of preexisting material the fayalitic olivine in the matrix of krymka is compositionally similar to olivine with platy morphology in the matrix of some cv3 chondrites and both have similar fe mn ratios but important morphological differences indicate that their relationship needs to be explored further textural and compositional data indicate that the fayalitic olivine in the matrix of krymka as well as in some other unequilibrated ordinary chondrites formed prior to final lithification of the meteorite and probably prior to parent body accretion we find that formation of the fayalitic olivine by vapor solid growth provides the best explanation for our observations and data and is the only feasible mechanism for the formation of fayalitic olivine in the matrix of krymka we propose that the fayalitic olivine formed by vaporization and recondensation of olivine rich dust during a period of enhanced dust gas ratio in the nebula

on the reasons for the formation and variability of the azores current abstract recent studies have shown that the formation of the well defined zonally oriented azores current may be the result of water mass transformation associated with the mediterranean outflow in the gulf of cadiz as the denser mediterranean water descends down the continental slope it entrains overlying north atlantic central water it is believed that the azores current then forms as part of the horizontal recirculating gyre generated through the plume mechanism in this study the authors further explore this hypothesis by performing a series of numerical experiments these experiments are based on a high resolution general circulation model that includes the mediterranean sea and that realistically simulates the water mass exchange through the strait of gibraltar and the transport and variability of the azores current the authors show that the divergence of the relative vorticity flux and the planetary vorticity flux associated with planetary waves are the main factors determining the variab

oxygen isotopic analysis of archaeological shells to detect seasonal use of wetlands on the southern pacific coast of mexico abstract oxygen isotopic ratios in modern and archaeological marsh clam shells polymesoda radiata from the acapetahua estuary in southwestern mexico record large scale salinity fluctuations caused by alternating wet and dry seasons thus prehistoric patterns of rainfall can be reconstructed and the season of molluscan death can be estimated changes in the oxygen isotopic patterns preserved in marsh clam shells from late archaic period c 3000 1800 bc archaeological deposits indicate that the season of shellfish harvesting changed dynamically through time in this region based on this study and other lines of archaeological evidence we argue that hunter gatherers during the early stages of the late archaic period visited locations in the littoral zone throughout the year with a focus during dry season months through the late archaic period a general trend occurred toward wet season use of these locations this culminated at the end of the late archaic period with the exclusive use of the littoral zone during wet season months these data indicate a fundamental shift in the way these estuarine locations were being used we argue that people living in this region altered their overall subsistence strategy during the late archaic period due to scheduling conflicts that occurred with the adoption of maize agriculture

variability in early vadose carbonate diagenesis in sandstones abstract early carbonate diagenesis in calcareous and siliciclastic sandstones in the vadose environment is reviewed and shown to be more extensive than generally recognized and more importantly highly variable in character both spatially and temporally spatial variability is classed into three hierarchical scales macro regional meso sediment body and micro individual and groups of pores dependent and independent variables relating to the diagenesis are shown to vary according to scale at the macro scale the independent variables are tectonic activity climate sea level and lithofacies at the meso scale they include location of the sediment body relative to the watertable and sea level and exposure to sea spray plant cover water balance relationships texture and allochem content micro scale independent variables are the chemistry amounts and mobility of the pore waters and individual particle microstructures and mineralogies dependent variables at one scale are shown to exist as independent variables at the next more detailed scale the infinitely complex combinations of variables operating over different time scales explain the observed and characteristic variability in diagenetic processes and products within the vadose zone

sources of sr and implications for weathering of limestone under tallgrass prairie northeastern kansas abstract grasslands of north central kansas are underlain by carbonate aquifers and shale aquitards chemical weathering rates in carbonates are poorly known and because large areas are underlain by these rocks solute fluxes are important to estimating global weathering rates grasslands exist where the amount of precipitation is extremely variable both within and between years so studies in grasslands must account for changes in weathering that accompany changes in precipitation this study 1 identifies phases that dominate chemical fluxes at konza prairie biological station kpbs and long term ecological research site and 2 addresses the impact of variable precipitation on mineral weathering the study site is a remnant tallgrass prairie in the central usa representing baseline weathering in a mid temperate climate grassland groundwater chemistry and hydrology in the 1 2 km 2 watershed used for this study suggest close connections between groundwater and surface water water levels fluctuate seasonally high water levels coincide with periods of precipitation plus low evapotranspiration rather than during precipitation peaks during the growing season precipitation is concentrated before recharging aquifers suggesting an as yet unquantified residence time in the thin soils groundwater and surface water are oversaturated with respect to calcite within limitations of available data water is more dilute in more permeable aquifers and water from one aquifer morrill is indistinguishable from surface water cations other than ca co vary with each other especially sr and mg potassium and si co vary in all aquifers and surface water and increases in concentrations of these elements are the best indicators of silicate weathering at this study site silicate weathering indices correlate inversely to aquifer hydraulic conductivity 87 sr 86 sr in water ranges from 0 70838 to 0 70901 and it decreases with increasing sr concentration and with increasing silicate weathering index carbonate extracted from aquifer materials shales soil and tufa has sr ranging from about 240 soil to 880 ppm paleozoic limestone 87 sr 86 sr ranges from 0 70834 0 00006 limestone to 0 70904 0 00019 soil in all cases 87 sr 86 sr of aquifer limestone is lower than 87 sr 86 sr of groundwater indicating a phase in addition to aquifer carbonate is contributing solutes to water aquifer recharge controls weathering during periods of reduced recharge increased residence time increases the total amount of all phases dissolved mixing analysis using 87 sr 86 sr shows that two end members are sufficient to explain sources of dissolved sr it is proposed that the less radiogenic end member is a solution derived from dissolving aquifer material longer residence time increases its contribution the more radiogenic end member solution probably results from reaction with soil carbonate or eolian dust this solution dominates solute flux in all but the least permeable aquifer and demonstrates the importance that land surface and soil zone reactions have on groundwater chemistry in a carbonate terrain

determining the local 87sr 86sr range for archaeological skeletons a case study from neolithic europe measurement of strontium isotopes in archaeological skeletons is an effective technique for characterizing prehistoric mobility however interpretation of the results can be highly sensitive to small changes in the determined local 87sr 86sr signature at an archaeological site because the local range is often defined as within 2 s d from the mean 87sr 86sr value in archaeological human bones the susceptibility of bones to diagenesis may lead to significant overestimates in the number of non locals at a particular site tooth enamel on the other hand is highly resistant to postmortem biochemical alteration and it is found that 87sr 86sr in archaeological enamel samples from animals of neolithic germany provide a useful alternative estimate for the local range

changing sources of base cations during ecosystem development hawaiian islands 87 sr 86 sr evidence from a soil chronosequence in the hawaiian islands demonstrates that the atmosphere supplies 85 of putatively rock derived sr in older sites initially bedrock is the dominant source for sr and other lithophile elements such as ca but high rates of weathering and leaching of the substrate by 20 ka lead to a shift to atmospheric sources the loss of weathering inputs coincides with other physio chemical changes in the soil and results in a steep decline of base cations in the soil pool while these patterns imply the potential for limitation of biological productivity by low base cation supply the atmosphere provides a supply of base cations in excess of nutritional needs even after nearly all rock derived base cations have been leached from the soil this raises the possibility that p limitation in terrestrial ecosystems may develop at least as much because of low rates of atmospheric deposition of p relative to ca k and other rock derived elements as because of its chemical interaction in soil

deciphering the nebular and asteroidal record of silicates and organic material in the matrix of the reduced cv3 chondrite vigarano we have conducted scanning electron microscope sem and transmission electron microscope tem studies of a variety of occurrences of matrix in the reduced cv3 chondrite breccia vigarano matrix which occurs as clastic interchondrule material and finer grained rims is dominated by morphologically variable olivines that host submicron hercynitic spinel and carbonaceous inclusions clastic matrix and fine grained rims show significant differences in their olivine morphologies abundance and composition of olivine inclusions and characteristics of the carbonaceous matter we suggest that these differences are the result of different degrees of alteration of clastic matrix and rims and are not due to variability in their precursor materials textural and compositional characteristics of olivine in the matrix are consistent with formation by growth possibly from an amorphous precursor material during asteroidal metamorphism in the presence of limited quantities of aqueous fluids spinel inclusions in olivine may be nebular condensates that acted as seeds for nucleation of olivine or may have formed during metamorphism and were subsequently overgrown by olivine carbonaceous material occurs as nanometer sized inclusions within olivine in both fine grained rims and clastic matrix but is most abundant as 100 200 nm grains interstitial to matrix olivines most carbonaceous material is amorphous but poorly graphitized carbon pgc also occurs as a minor component in both olivine inclusions and interstitial c the widespread occurrence of fine grained amorphous carbon grains in the interstitial regions between olivine grains may preserve the distribution and grain size of nebular organic material no clear textural relationships exist between carbonaceous grains and the other mineralogical components of vigarano matrix that could help constrain the origin of the organic grains i e evidence for fischer tropsch type reactions finally there are considerable differences between matrix olivines in vigarano in comparison with those in oxidized cv3 chondrites in particular the mineralogy and morphology of the matrix olivines and the nature composition and distribution of inclusions in the olivine grains are distinct based on these differences we conclude that matrix in the oxidized cv3 chondrites could not have formed by thermal processing of vigarano like material

volcanic lakes of the azores archipelago portugal geological setting and geochemical characterization abstract a representative set of 30 lakes from the azores archipelago portugal has been studied to obtain data on their volcanic setting and water geochemistry the majority of the studied lakes are located inside volcanic craters and subsidence calderas while the remaining lakes are located in topographic depressions not associated with volcanic centres in depressions of tectonic origin and inside lava caves in general the azorean volcanic lakes are small with surface areas between 8 94 10 4 km 2 and 4 35 km 2 and volumes between 2 4 10 3 and 4 78 10 7 m 3 median 3 99 10 4 m 3 presenting maximum depths between 0 8 and 33 m mostly of the na cl to na hco 3 type the lake waters are generally low temperature 11 9 24 6 c very dilute tds range between 11 0 and 356 2 mg l median 36 8 mg l and a clear exception is furna do enxofre lake graciosa island that shows a mg trend two types of lake waters can be recognized 1 one is characterized by na cl ratio close to the seawater value and have evolved and evolve by marine contribution and 2 na hco 3 type waters that in addition to sea salt input have been influenced by other processes e g water rock interaction hydrothermal seepage into the lake bottom evident from higher total co 2 content 365 1 mg l and sio 2 content 74 9 mg l as well demonstrated by in the furna do enxofre lake nevertheless volcanic contribution cannot be excluded for some lakes as furna do enxofre vertical profiles made at the deepest lakes of sao miguel reveal that major ion content varies little with depth largely independent of the occurrence of thermally driven density stratification in summer for some lakes however dissolved co 2 increases with depth and is kept in the hypolimnion in summer whereas the hco 3 content is stable suggesting that co 2 release exceeds acidity neutralization by water rock interaction during winter without stratification the dissolved co 2 increase is less sharp for the majority of the lakes with the exception of furnas and furna do enxofre lakes the co 2 enrichment observed for certain lakes e g furna do enxofre and furnas implies a volcanic input moreover as these lakes themselves are located near hydrothermal surface manifestations they therefore offer good targets of volcano monitoring in the azores

the impact of biotic abiotic interfaces in mineral nutrient cycling a study of soils of the santa cruz chronosequence california abstract biotic abiotic interactions between soil mineral nutrients and annual grassland vegetation are characterized for five soils in a marine terrace chronosequence near santa cruz california a mediterranean climate with wet winters and dry summers controls the annual cycle of plant growth and litter decomposition resulting in net above ground productivities of 280 600 g m 2 yr 1 the biotic abiotic a b interface separates seasonally reversible nutrient gradients reflecting biological cycling in the shallower soils from downward chemical weathering gradients in the deeper soils the a b interface is pedologically defined by argillic clay horizons centered at soil depths of about one meter which intensify with soil age below these horizons elevated solute na ca mg ca and sr ca ratios reflect plagioclase and smectite weathering along pore water flow paths above the a b interface lower cation ratios denote temporal variability due to seasonal plant nutrient uptake and litter leaching potassium and ca exhibit no seasonal variability beneath the a b interface indicating closed nutrient cycling within the root zone whereas mg variability below the a b interface denotes downward leakage resulting from higher inputs of marine aerosols and lower plant nutrient requirements the fraction of a mineral nutrient annually cycled through the plants compared to that lost from pore water discharge is defined their respective fluxes fj plants qj plants qj plants qj discharge with average values for k and ca fk plants 0 99 fca plants 0 93 much higher than for mg and na fmg plants 0 64 fna plants 0 28 the discrimination against rb and sr by plants is described by fractionation factors ksr ca 0 86 krb k 0 83 which are used in rayleigh fractionation mixing calculations to fit seasonal patterns in solute k and ca cycling krb k and k 24 mg 22 mg values derived from isotope data in the literature fall within fractionation envelopes bounded by inputs from rainfall and mineral weathering ksr ca and k 44 ca 40 ca fractionation factors fall outside these envelopes indicating that ca nutrient cycling is closed to these external inputs small net positive k and ca fluxes 6 14 mol m 2 yr 1 based on annual mass balances indicate that the soils are accumulating mineral nutrients probably as a result of long term environmental disequilibrium

mechanisms of magnesium isotope fractionation in volcanic soil weathering sequences guadeloupe magnesium mg stable isotopes are increasingly used as a weathering proxy in soils and rivers but the impact of the mineralogy of secondary phases on isotopefractionation remains obscure a better understanding of the behaviour of mg isotopes during weathering processes is a mandatory step toward deployment of this new tracer for understanding chemical fluxes exported from the critical zone here we investigate isotopic variations in 26mg in bulk soils and clay fractions relative to their parent andesite in three soilweatheringsequences from guadeloupe formed under contrasting climatic conditions soils formed in drier conditions low precipitation contain smectite whereas soils formed under wet conditions high rainfall are characterized by halloysite and fe oxides or kaolinite all clay fractions have mg isotopic compositions 26mg 0 41 to 0 10 similar to or heavier than their parent andesite 26mg 0 47 supporting the preferential incorporation of heavy mg isotopes in secondary mg bearing clay minerals with the first direct measurements on clay fractions soils with lighter mg isotope compositions have greater quantities of exchangeable mg the data support a contribution from sea spray to the exchangeable mg pool correlated to the soilweathering degree this study highlights for the first time that the soil 26mg not only depend on 26mg of the parent rock and on any fractionation that might occur but also on the mg retention on the exchange complex which could in turn be controlled by external inputs such as sea spray

origin of iron rich olivine in the matrices of type 3 ordinary chondrites an experimental study in order to understand the origin of iron rich olivine in the matrices of type 3 ordinary chondrites the reaction of metallic iron and enstatite with and without forsterite and sio2 has been experimentally reproduced at temperatures between 1150 and 800 c and po2 between 10 11 and 10 16 atm between the iqf and mw buffers the olivine produced ranges from fo58 to fo34 and this composition does not change significantly with temperature and time of the runs the magnesian olivine which forms does become more magnesian with increasing forsterite enstatite ratio of the starting materials iron rich olivine fo 35 cannot be formed by the reaction of enstatite and metallic iron with or without forsterite as starting materials but it can be formed in the presence of free silica the composition of olivine becomes more iron rich with increasing silica enstatite ratio the compositional range of olivine formed from each mixture is 25 30 mole fo regardless of the temperature composition mineral assemblage and run duration from these experimental results two possibilities suggested for the origin of the iron rich olivine in the matrices of type 3 ordinary chondrites 1 free silica must have been present if the iron rich olivine was formed by solid state reactions under oxidizing condition in the solar nebula 2 reaction of silicon rich gas with metallic iron took place under oxidizing condition in the solar nebula though it is difficult to define which alternative was dominant the formation of free silica or silicon rich gas may be a result of fractional condensation this is possible if there is a reaction relation between forsterite and gas to produce enstatite the suggested fractional condensation is supported by the fact that the compositions of the fine grained matrices of type 3 ordinary chondrites are more silica rich than the bulk compositions of the chondrites though it is not known whether such conditions were established all over the nebula or locally in the nebula both fractionation and more oxidizing conditions than the average solar nebula are required for the formation of matrix olivine