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Oxygen Isotopes (oxygen + isotope)

Distribution by Scientific Domains

Chemistry	32%
Humanities and Social Sciences	25%
Earth and Environmental Science	21%
Life Sciences	10%

Terms modified by Oxygen Isotopes

oxygen isotope analysis

oxygen isotope composition

oxygen isotope enrichment

oxygen isotope ratio

oxygen isotope signal

oxygen isotope stage

oxygen isotope value

Selected Abstracts

THE USE OF OXYGEN ISOTOPES IN SHEEP MOLARS TO INVESTIGATE PAST HERDING PRACTICES AT THE NEOLITHIC SETTLEMENT OF ÇATALHÖYÜK, CENTRAL ANATOLIA

ARCHAEOMETRY, Issue 3 2010
E. HENTON
This paper presents a pilot study designed to test the use of oxygen isotopes for investigating aspects of early herding practices in the Neolithic of western Asia, using the site of Çatalhöyük in central Anatolia as a case study. Time-sequenced ,18O values in dental enamel of archaeological sheep are assessed for post-depositional diagenetic effects and compared with seasonal ,18O meteoric water values in the region today. The evidence is used to indicate the environmental conditions in which individual sheep spent their first year, enabling management of breeding and birthing seasons, and movement to seasonal pastures, to be investigated. [source]

Amino-acid geochronology and the British Pleistocene: secure stratigraphical framework or a case of circular reasoning?

JOURNAL OF QUATERNARY SCIENCE, Issue 7 2002
Danny McCarroll
Abstract Aminostratigraphy is central to the recently revised correlation of Quaternary deposits in the British Isles, providing a link between terrestrial deposits and marine Oxygen Isotope Stages. The central tenet of British aminostratigraphy, however, that shells from the same interglacial yield very similar ratios, so that the characteristic ratios from different interglacials are distinct, remains uncertain. The data available suggest that amino-acid ratios from different interglacials do not fall into discrete groups, but overlap considerably. It is therefore not valid to assign individual shells to Oxygen Isotope Stages simply on the basis of their amino-acid ratios, which means that filtering data to remove high or low values, on the assumption that they represent reworked shells, is unacceptable. The range of ,characteristic ratios' assigned to British warm stages may have been underestimated and the degree of separation between them overestimated. Amino-acid ratios should be treated as sample data that are naturally variable. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Oxygen isotope and palaeotemperature records from six Greenland ice-core stations: Camp Century, Dye-3, GRIP, GISP2, Renland and NorthGRIP

JOURNAL OF QUATERNARY SCIENCE, Issue 4 2001
Sigfus J. Johnsen
Abstract Oxygen isotope variations spanning the last glacial cycle and the Holocene derived from ice-core records for six sites in Greenland (Camp Century, Dye-3, GRIP, GISP2, Renland and NorthGRIP) show strong similarities. This suggests that the dominant influence on oxygen isotope variations reflected in the ice-sheet records was regional climatic change. Differences in detail between the records probably reflect the effects of basal deformation in the ice as well as geographical gradients in atmospheric isotope ratios. Palaeotemperature estimates have been obtained from the records using three approaches: (i) inferences based on the measured relationship between mean annual ,18O of snow and of mean annual surface temperature over Greenland; (ii) modelled inversion of the borehole temperature profile constrained either by the dated isotopic profile, or (iii) by using Monte Carlo simulation techniques. The third of these approaches was adopted to reconstruct Holocene temperature variations for the Dye 3 and GRIP temperature profiles, which yields remarkably compatible results. A new record of Holocene isotope variations obtained from the NorthGRIP ice-core matches the GRIP short-term isotope record, and also shows similar long-term trends to the Dye-3 and GRIP inverted temperature data. The NorthGRIP isotope record reflects: (i) a generally stronger isotopic signal than is found in the GRIP record; (ii) several short-lived temperature fluctuations during the first 1500 yr of the Holocene; (iii) a marked cold event at ca. 8.2 ka (the ,8.2 ka event'); (iv) optimum temperatures for the Holocene between ca. 8.6 and 4.3 ka, a signal that is 0.6, stronger than for the GRIP profile; (v) a clear signal for the Little Ice Age; and (vi) a clear signal of climate warming during the last century. These data suggest that the NorthGRIP stable isotope record responded in a sensitive manner to temperature fluctuations during the Holocene. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Oxygen isotope and 26Al- 26Mg systematics of aluminum-rich chondrules from unequilibrated enstatite chondrites

METEORITICS & PLANETARY SCIENCE, Issue 1 2006
Yunbin Guan
Among eleven aluminum-rich chondrules and two plagioclase fragments measured for 26Al- 26Mg systematics, only one aluminum-rich chondrule contains excess 26Mg from the in situ decay of 26Al; the inferred initial ratio (26Al/27Al)o = (6.8 ± 2.4) × 10,6 is consistent with ratios observed in chondrules from carbonaceous chondrites and unequilibrated ordinary chondrites. The oxygen isotopic compositions of five aluminum-rich chondrules and one plagioclase fragment define a line of slope ,0.6 ± 0.1 on a three-oxygen-isotope diagram, overlapping the field defined by ferromagnesian chondrules in enstatite chondrites but extending to more 16O-rich compositions with a range in ,18O of about ,12,. Based on their oxygen isotopic compositions, aluminum-rich chondrules in unequilibrated enstatite chondrites are probably genetically related to ferromagnesian chondrules and are not simple mixtures of materials from ferromagnesian chondrules and calcium-aluminum-rich inclusions (CAIs). Relative to their counterparts from unequilibrated ordinary chondrites, aluminum-rich chondrules from unequilibrated enstatite chondrites show a narrower oxygen isotopic range and much less resolvable excess 26Mg from the in situ decay of 26Al, probably resulting from higher degrees of equilibration and isotopic exchange during post-crystallization metamorphism. However, the presence of 26Al-bearing chondrules within the primitive ordinary, carbonaceous, and now enstatite chondrites suggests that 26Al was at least approximately homogeneously distributed across the chondrite-forming region. [source]

Oxygen isotopes in nitrate: new reference materials for 18O:17O:16O measurements and observations on nitrate-water equilibration,,

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 16 2003
J. K. Böhlke
Despite a rapidly growing literature on analytical methods and field applications of O isotope-ratio measurements of NO3, in environmental studies, there is evidence that the reported data may not be comparable because reference materials with widely varying ,18O values have not been readily available. To address this problem, we prepared large quantities of two nitrate salts with contrasting O isotopic compositions for distribution as reference materials for O isotope-ratio measurements: USGS34 (KNO3) with low ,18O and USGS35 (NaNO3) with high ,18O and ,mass-independent' ,17O. The procedure used to produce USGS34 involved equilibration of HNO3 with 18O-depleted meteoric water. Nitric acid equilibration is proposed as a simple method for producing laboratory NO3, reference materials with a range of ,18O values and normal (mass-dependent) 18O:17O:16O variation. Preliminary data indicate that the equilibrium O isotope-fractionation factor (,) between [NO3,] and H2O decreases with increasing temperature from 1.0215 at 22°C to 1.0131 at 100°C. USGS35 was purified from the nitrate ore deposits of the Atacama Desert in Chile and has a high 17O:18O ratio owing to its atmospheric origin. These new reference materials, combined with previously distributed NO3, isotopic reference materials IAEA-N3 (=IAEA-NO-3) and USGS32, can be used to calibrate local laboratory reference materials for determining offset values, scale factors, and mass-independent effects on N and O isotope-ratio measurements in a wide variety of environmental NO3, samples. Preliminary analyses yield the following results (normalized with respect to VSMOW and SLAP, with reproducibilities of ±0.2,0.3,, 1,): IAEA-N3 has ,18O,=,+25.6, and ,17O,=,+13.2,; USGS32 has ,18O,=,+25.7,; USGS34 has ,18O,=,,27.9, and ,17O,=,,14.8,; and USGS35 has ,18O,=,+57.5, and ,17O,=,+51.5,. Published in 2003 by John Wiley & Sons, Ltd. [source]

Stable isotope records of plant cover change and monsoon variation in the past 2200 years: evidence from laminated stalagmites in Beijing, China

BOREAS, Issue 2 2003
JU ZHI HOU
Two stalagmites collected from the Shihua cave in the southwestern suburb of Beijing were dated by annual layer counting. The results are consistent with thermal ionization mass spectrometry 230Th dating. Stable carbon isotope variation of stalagmites is dominated by plant cover change, which largely reflects climate change and monsoon variation. Oxygen isotopes are mainly affected by precipitation, which is related to summer and winter monsoon intensity. The combination of carbon and oxygen isotopes can therefore be a proxy of plant cover change and monsoon variation. Our stable isotope results show that lower carbon isotope values of the stalagmites between 200 BC and AD 1000 probably imply dense plant cover and an episode dominated by humid summer monsoon. From ,1000 to AD 1450, the dominant monsoon alternated between the winter monsoon and the summer monsoon. Since ,AD 1450, a significant jump in carbon isotope ratios and increasing oxygen isotope ratios has been demonstrated, indicating less plant cover and the probable dominance of dry winter monsoon. The results are consistent with historical documents of the region. [source]

Water Sources of Dominant Species in Three Alpine Ecosystems on the Tibetan Plateau, China

JOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 3 2008
De-Yu Duan
Abstract Plant water sources were estimated by two or three compartment linear mixing models using hydrogen and oxygen isotope (,D and ,18O) values of different components such as plant xylem water, precipitation and river water as well as soil water on the Tibetan Plateau in the summer of 2005. Four dominant species (Quercus aquifolioides, Pinus tabulaeformis, Salix rehderiana and Nitraria tangutorum) in three typical ecosystems (forest, shrub and desert) were investigated in this study. Stable isotope ratios of the summer precipitations and the soil water presented variations in spatial and temporal scales. ,18O values of N. tangutorum xylem water were constant in the whole growth season and very similar to those of deep soil water. Water sources for all of the plants came from both precipitations and soil water. Plants switched rapidly among different water sources when environmental water conditions changed. Rainwater had different contributions to the plants, which was influenced by amounts of precipitation. The percentage of plant xylem water derived from rainwater rose with an increase in precipitation. Water sources for broad-leaved and coniferous species were different although they grew in the same environmental conditions. For example, the broad-leaved species Q. aquifolioides used mainly the water from deep soil, while 92.5% of xylem water of the coniferous species P. tabulaeformis was derived from rainwater during the growth season. The study will be helpful for us to fully understand responses of species on the Tibetan Plateau to changes in precipitation patterns, and to assess accurately changes of vegetation distribution in the future. [source]

Assessing the sources and magnitude of diurnal nitrate variability in the San Joaquin River (California) with an in situ optical nitrate sensor and dual nitrate isotopes

FRESHWATER BIOLOGY, Issue 2 2009
BRIAN A. PELLERIN
Summary 1.,We investigated diurnal nitrate (NO3,) concentration variability in the San Joaquin River using an in situ optical NO3, sensor and discrete sampling during a 5-day summer period characterized by high algal productivity. Dual NO3, isotopes (,15NNO3 and ,18ONO3) and dissolved oxygen isotopes (,18ODO) were measured over 2 days to assess NO3, sources and biogeochemical controls over diurnal time-scales. 2.,Concerted temporal patterns of dissolved oxygen (DO) concentrations and ,18ODO were consistent with photosynthesis, respiration and atmospheric O2 exchange, providing evidence of diurnal biological processes independent of river discharge. 3.,Surface water NO3, concentrations varied by up to 22% over a single diurnal cycle and up to 31% over the 5-day study, but did not reveal concerted diurnal patterns at a frequency comparable to DO concentrations. The decoupling of ,15NNO3 and ,18ONO3 isotopes suggests that algal assimilation and denitrification are not major processes controlling diurnal NO3, variability in the San Joaquin River during the study. The lack of a clear explanation for NO3, variability likely reflects a combination of riverine biological processes and time-varying physical transport of NO3, from upstream agricultural drains to the mainstem San Joaquin River. 4.,The application of an in situ optical NO3, sensor along with discrete samples provides a view into the fine temporal structure of hydrochemical data and may allow for greater accuracy in pollution assessment. [source]

Carbon and oxygen isotopes: a tool for Jurassic and early Cretaceous pelagic correlation (southern Spain)

GEOLOGICAL JOURNAL, Issue 4 2002
J. Rey
Abstract The isotopic evolution of ,13C and ,18O is reported for the Jurassic and early Cretaceous in two pelagic sections of the External Zones in the Betic Cordilleras (SE Spain). Stable isotope curves from pelagic trough and swell sections display similar patterns. Variations in ,18O and ,13C values from strata at equivalent age probably reflect both early diagenetic cementation and later temperature-related burial diagenesis. Comparison of global isotope curves with those presented in this work allows the differentiation of global from local events. Thus, the anoxic event during the early Toarcian (falciferum Zone) is characterized by elevated ,13C and depressed ,18O values. The isotopic record also allows the detection of the middle Oxfordian transgression. There are other peaks for the late Toarcian, early Bajocian, Callovian and early Berriasian that can also be used as tools for correlation purposes. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Further Characterisation of the 91500 Zircon Crystal

GEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 1 2004
Michael Wiedenbeck
zircon 91500; matériau de référence; intercomparaison entre techniques; valeurs de travail This paper reports the results from a second characterisation of the 91500 zircon, including data from electron probe microanalysis, laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS), secondary ion mass spectrometry (SIMS) and laser fluorination analyses. The focus of this initiative was to establish the suitability of this large single zircon crystal for calibrating in situ analyses of the rare earth elements and oxygen isotopes, as well as to provide working values for key geochemical systems. In addition to extensive testing of the chemical and structural homogeneity of this sample, the occurrence of banding in 91500 in both backscattered electron and cathodoluminescence images is described in detail. Blind intercomparison data reported by both LA-ICP-MS and SIMS laboratories indicate that only small systematic differences exist between the data sets provided by these two techniques. Furthermore, the use of NIST SRM 610 glass as the calibrant for SIMS analyses was found to introduce little or no systematic error into the results for zircon. Based on both laser fluorination and SIMS data, zircon 91500 seems to be very well suited for calibrating in situ oxygen isotopic analyses. Cet article présente les résultats d'une nouvelle caractérisation du zircon 91500, dont des données de microanalyse par sonde électronique, d'analyse par ablation laser en couplage à un ICP-MS, d'analyse par sonde ionique (SIMS) et d'analyse par fluorination laser. Le but de cette étude etait de démontrer que ce large monocristal de zircon pouvait être utilisé pour la calibration d'analyses in situ de Terres Rares et des isotopes de I'Oxygène, et en même temps de fournir des valeurs "de travail" pour un certain nombre de systémes géochimiques cruciaux. En complément des tests systématiques d'homogénéité de I'échantillon, tant chimiquement que structurellement, /'ex/sfence, dans le zircon 91500, de zonages visibles en électrons retro diffusés et en cathodoluminescence, est décrite en détail, line comparaison en aveugle des résultats obtenus par LA-ICP-MS et par SIMS, dans des laboratoires différents, montre que les différences systématiques entre les ensembles de données obtenues par ces deux techniques sont très faibles. De plus, I'utilisation du verre NIST SRM 610 comme calibrant lors de I'analyse par SIMS n'introduit qu'une erreur systématique très faible si ce n'est inexistante sur les résultats du zircon. Sur la base des analyses par fluorination laser et par SIMS, le zircon 91500 semble être parfaitement adapte a son utilisation pour la calibration d'analyses isotopiques in situ d'oxygène. [source]

The River Arno catchment, northern Tuscany: chemistry of waters and sediments from the River Elsa and River Era sub-basins, and sulphur and oxygen isotopes of aqueous sulphate

HYDROLOGICAL PROCESSES, Issue 1 2007
Gianni Cortecci
Abstract Within the hydrologic balance of the River Arno catchment (northern Tuscany), the Rivers Elsa and Era are important tributaries entering the main river from the left bank in the lower part of the watershed. Waters and bed sediments were sampled in June 2000 during low discharges in the Rivers Elsa and Era, as well as in major tributary streams. Water samples were analysed for major chemistry and sulphur isotope composition of sulphate, and sediment samples were analysed for major composition and selected trace elements of environmental concern (Zn, Cu, Pb, Cr and Ni). The main results for the waters are: (1) Na and Cl in solution show consistent downstream positive trends in the main rivers, thus supporting progressive contributions of anthropogenic salts; the highest concentration values are observed in tributaries; (2) as shown by sulphur isotopes, sulphate in solution is mainly controlled by dissolution of evaporites (Elsa basin) or oxidation of reduced organic/biogenic sulphur (Era basin), with anthropogenic contributions in most streams not higher than 10% in both the basins. A ,34S signature in the range ,2 to +3, is estimated for pollutant sulphate in the basins studied. The main results for the sediments are: (1) major chemistry is essentially controlled by the lithotypes drained by the waters; (2) pollution by heavy metals does not reach high levels; (3) compared with local fine-grained rocks, copper is more frequently anomalous, whereas lead and zinc show only occasional anomalies; (4) local high concentrations of chromium and nickel can be attributed to upstream occurrences of ophiolites. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Vicariance or dispersal: the use of natural historical data to test competing hypotheses of disjunction on the Tyrrhenian coast

JOURNAL OF BIOGEOGRAPHY, Issue 1 2001
George F. Estabrook
Aim To illustrate the use of natural historical data to evaluate vicariance and dispersal as hypotheses competing to explain disjunct populations. Location Nine disjunct areas on the margin of the Tyrrhenian basin of the Mediterranean Sea. Methods First describe how each hypothesized mechanism might explain the observed morphological variation in the model species complex, Genista ephedroides (Fabaceae); then confront the hypotheses with natural historical data including geology, oxygen isotopes, palynology, macro-, micro- and nano-fossils, and sea level changes, and with the ecological tolerances of the model species complex. Results Dispersal seems the more credible explanation. Main conclusion Patterns of morphological (or other) variation among related disjunct taxa can fit both vicariance and dispersal hypotheses. However they can possibly be distinguished by considering natural historical data. [source]

Estimating the timing of growth rings in Atlantic cod otoliths using stable oxygen isotopes

JOURNAL OF FISH BIOLOGY, Issue 3 2006
H. Høie
A technique involving micro-scale sampling of otolith carbonate and analyses of stable oxygen isotope composition was used to relate the zone appearance of the otolith to the seasonal temperature cycle. Otolith opacity could then be related to the timing of zone formation. Otoliths from two groups of Atlantic cod Gadus morhua held under known temperature conditions over a period of 4 and 6 years were examined. The otolith translucency followed the same pattern as the estimated temperature (from otolith ,18O values) in the yearly increments three and four, meaning that the translucent zones were deposited at the seasonal highest temperature in late summer and early autumn. The relative light intensities of otolith yearly increments five and six of older fish (deposited in the same years), however, were not significantly correlated to the estimated temperatures since increased otolith translucency also occurred at low temperatures. This might have been caused by stress in connection with gonad development or starvation during the spawning period. The results showed that this method of coupling otolith opacity and stable oxygen isotope composition can be used to estimate the timing of zone formations in otoliths. [source]

Oxygen isotope analysis of phosphate: improved precision using TC/EA CF-IRMS,

JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2009
D. F. LaPorte
Abstract Oxygen isotope values of biogenic apatite have long demonstrated considerable promise for paleothermometry potential because of the abundance of material in the fossil record and greater resistance of apatite to diagenesis compared to carbonate. Unfortunately, this promise has not been fully realized because of relatively poor precision of isotopic measurements, and exceedingly small size of some substrates for analysis. Building on previous work, we demonstrate that it is possible to improve precision of ,18OPO4 measurements using a ,reverse-plumbed' thermal conversion elemental analyzer (TC/EA) coupled to a continuous flow isotope ratio mass spectrometer (CF-IRMS) via a helium stream [Correction made here after initial online publication]. This modification to the flow of helium through the TC/EA, and careful location of the packing of glassy carbon fragments relative to the hot spot in the reactor, leads to narrower, more symmetrically distributed CO elution peaks with diminished tailing. In addition, we describe our apatite purification chemistry that uses nitric acid and cation exchange resin. Purification chemistry is optimized for processing small samples, minimizing isotopic fractionation of PO4,3 and permitting Ca, Sr and Nd to be eluted and purified further for the measurement of ,44Ca and 87Sr/86Sr in modern biogenic apatite and 143Nd/144Nd in fossil apatite. Our methodology yields an external precision of ± 0.15, (1,) for ,18OPO4. The uncertainty is related to the preparation of the Ag3PO4 salt, conversion to CO gas in a reversed-plumbed TC/EA, analysis of oxygen isotopes using a CF-IRMS, and uncertainty in constructing calibration lines that convert raw ,18O data to the VSMOW scale. Matrix matching of samples and standards for the purpose of calibration to the VSMOW scale was determined to be unnecessary. Our method requires only slightly modified equipment that is widely available. This fact, and the demonstrated improvement in precision, should help to make apatite paleothermometry far more accessible to paleoclimate researchers. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Geochemical constraints of the eclogite and granulite facies metamorphism as recognized in the Raobazhai complex from North Dabie Shan, China

JOURNAL OF METAMORPHIC GEOLOGY, Issue 1 2001
Y. L. Xiao
Abstract A combined study of major and trace elements, fluid inclusions and oxygen isotopes has been carried out on garnet pyroxenite from the Raobazhai complex in the North Dabie Terrane (NDT). Well-preserved compositional zoning with Na decreasing and Ca and Mg increasing from the core to rim of pyroxene in the garnet pyroxenite indicates eclogite facies metamorphism at the peak metamorphic stage and subsequent granulite facies metamorphism during uplift. A P,T path with substantial heating (from c. 750 to 900 °C) after the maximum pressure reveals a different uplift history compared with most other eclogites in the South Dabie Terrane (SDT). Fluid inclusion data can be correlated with the metamorphic grade: the fluid regime during the peak metamorphism (eclogite facies) was dominated by N2 -bearing NaCl-rich solutions, whereas it changed into CO2 -dominated fluids during the granulite facies retrograde metamorphism. At a late retrograde metamorphic stage, probably after amphibolite facies metamorphism, some external low-salinity fluids were involved. In situ UV-laser oxygen isotope analysis was undertaken on a 7 mm garnet, and impure pyroxene, amphibole and plagioclase. The nearly homogeneous oxygen isotopic composition (,18OVSMOW = c. 6.7,) in the garnet porphyroblast indicates closed fluid system conditions during garnet growth. However, isotopic fractionations between retrograde phases (amphibole and plagioclase) and garnet show an oxygen isotopic disequilibrium, indicating retrograde fluid,rock interactions. Unusual MORB-like rare earth element (REE) patterns for whole rock of the garnet pyroxenite contrast with most ultra-high-pressure (UHP) eclogites in the Dabie-Sulu area. However, the age-corrected initial ,Nd(t) is ,,2.9, which indicates that the protolith of the garnet pyroxenite was derived from an enriched mantle rather than from a MORB source. Combined with the present data of oxygen isotopic compositions and the characteristic N2 content in the fluid inclusions, we suggest that the protolith of the garnet pyroxenite from Raobazhai formed in an enriched mantle fragment, which has been exposed to the surface prior to the Triassic metamorphism. [source]

Refractory calcium-aluminum-rich inclusions and aluminum-diopside-rich chondrules in the metal-rich chondrites Hammadah al Hamra 237 and Queen Alexandra Range 94411

METEORITICS & PLANETARY SCIENCE, Issue 9 2001
Alexander N. KROT
Forty CAIs and CAI fragments and seven Al-diopside-rich chondrules were identified in HH 237 and QUE 94411/94627. The CAIs, ,50,400 ,m in apparent diameter, include (a) 22 (56%) pyroxene-spinel ± melilite (+forsterite rim), (b) 11 (28%) forsterite-bearing, pyroxene-spinel ± melilite ± anorthite (+forsterite rim) (c) 2 (5%) grossite-rich (+spinel-melilite-pyroxene rim), (d) 2 (5%) hibonite-melilite (+spinel-pyroxene ± forsterite rim), (e) 1 (2%) hibonite-bearing, spinel-perovskite (+melilite-pyroxene rim), (f) 1 (2%) spinel-melilite-pyroxene-anorthite, and (g) 1 (2%) amoeboid olivine aggregate. Each type of CAI is known to exist in other chondrite groups, but the high abundance of pyroxene-spinel ± melilite CAIs with igneous textures and surrounded by a forsterite rim are unique features of HH 237 and QUE 94411/94627. Additionally, oxygen isotopes consistently show relatively heavy compositions with ,17O ranging from ,6%0 to ,10%0 (1, = 1.3%0) for all analyzed CAI minerals (grossite, hibonite, melilite, pyroxene, spinel). This suggests that the CAIs formed in a reservoir isotopically distinct from the reservoir(s) where "normal", 16O-rich (,17O < ,20%0) CAIs in most other chondritic meteorites formed. The Al-diopside-rich chondrules, which have previously been observed in CH chondrites and the unique carbonaceous chondrite Adelaide, contain Al-diopside grains enclosing oriented inclusions of forsterite, and interstitial anorthitic mesostasis and Al-rich, Ca-poor pyroxene, occasionally enclosing spinel and forsterite. These chondrules are mineralogically similar to the Al-rich barred-olivine chondrules in HH 237 and QUE 94411/94627, but have lower Cr concentrations than the latter, indicating that they may have formed during the same chondrule-forming event, but at slightly different ambient nebular temperatures. Aluminum-diopside grains from two Al-diopside-rich chondrules have O-isotopic compositions (,17O , ,7 ± 1.1 %0) similar to CAI minerals, suggesting that they formed from an isotopically similar reservoir. The oxygen-isotopic composition of one Ca, Al-poor cryptocrystalline chondrule in QUE 94411/94627 was analyzed and found to have ,17O , ,3 ± 1.4%0. The characteristics of the CAIs in HH 237 and QUE 94411/94627 are inconsistent with an impact origin of these metal-rich meteorites. Instead they suggest that the components in CB chondrites are pristine products of large-scale, high-temperature processes in the solar nebula and should be considered bona fide chondrites. [source]

Palaeoclimate reconstruction on Big Lyakhovsky Island, north Siberia,hydrogen and oxygen isotopes in ice wedges

PERMAFROST AND PERIGLACIAL PROCESSES, Issue 2 2002
Hanno Meyer
Abstract Late Quaternary permafrost deposits on Big Lyakhovsky Island (New Siberian Islands, Russian Arctic) were studied with the aim of reconstructing the palaeoclimatic and palaeoenvironmental conditions of northern Siberia. Hydrogen and oxygen stable isotope analyses are presented for six different generations of ice wedges as well as for recent ice wedges and precipitation. An age of about 200 ka BP was determined for an autochtonous peat layer in ice-rich deposits by U/Th method, containing the oldest ice wedges ever analysed for hydrogen and oxygen isotopes. The palaeoclimatic reconstruction revealed a period of severe winter temperatures at that time. After a gap in the sedimentation history of several tens of thousands of years, ice-wedge growth was re-initiated around 50 ka BP by a short period of extremely cold winters and rapid sedimentation leading to ice-wedge burial and characteristic ice-soil wedges (,polosatics'). This corresponds to the initial stage for the Late Weichselian Ice Complex, a peculiar cryolithogenic periglacial formation typical of the lowlands of northern Siberia. The Ice Complex ice wedges reflect cold winters and similar climatic conditions as around 200 ka BP. With a sharp rise in ,18O of 6, and ,D of 40,, the warming trend between Pleistocene and Holocene ice wedges is documented. Stable isotope data of recent ice wedges show that Big Lyakhovsky Island has never been as warm in winter as today. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Tracing the geographical origin of beefs being circulated in Korean markets based on stable isotopes

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 1 2010
Yeon-Sik Bong
We have examined the carbon, nitrogen and oxygen isotopic compositions of American, Mexican, Australian, New Zealand and Korean beefs, which are currently being circulated in Korean markets, to check whether stable isotope ratios can identify their country of origin. Each beef exhibited statistically distinct isotopic compositions, especially in oxygen and carbon, because of the different isotopic compositions of their water and cattle feeds. Nevertheless, their isotopic compositions still showed some overlap, especially among USA, Australian, and Korean beefs, which sometimes resulted in significant misidentification when a single isotope was considered. However, the discrimination was generally successful when both the carbon and the oxygen isotopes were used. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Hydrogen and oxygen isotopes of water from inclusions in minerals: design of a new crushing system and on-line continuous-flow isotope ratio mass spectrometric analysis

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2009
Yuri V. Dublyansky
An analytical line for stable isotope analyses of water recovered from fluid inclusions in minerals was built and successfully tested. The line is based on the principle of continuous-flow analysis of water via high-temperature reduction on glassy carbon. It includes a custom-designed set of high-efficiency crushers and a cryo-focusing cell. This paper provides details of the line design and discusses strategies for line conditioning and mitigation of memory effects. The line allows measurements of hydrogen and oxygen isotopes during a single acquisition. The precision of the analyses depends on the amount of water released from the inclusions. The best results are obtained for samples containing at least 0.1,0.2,µL (0.06,0.11,µmol) H2O. For such samples precision is better than 1.5, for ,D and 0.5, for ,18O (1,). Smaller amounts of water can be measured but at lower precision. Analyses of modern calcite formed under stable conditions in a deep cave allowed assessment of the accuracy of the analyses. The ,D values measured in fluid inclusions of this working standard match the ,D value of the parent water, and the oxygen isotope values agree within ca. 0.5,. This indicates that fluid inclusions trapped in calcite at near-ambient temperatures (e.g. speleothems and low-temperatures phreatic calcite) faithfully preserve the original isotopic composition of the parent waters. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Continuous shipboard sampling system for determination of triple oxygen isotopes and O2/Ar ratio by dual-inlet mass spectrometry

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 23 2006
V. V. S. S. Sarma
A continuous shipboard sampling system was developed for the determination of the isotopic composition of the triple oxygen isotopes and oxygen to argon (O2/Ar) ratios in dissolved air. In this system, dissolved air is separated by a hollow fiber membrane degassing module. This system collects dissolved air quantitatively and rapidly. The sample flow rate through the membrane is critical for the fractionation of the oxygen isotopes and the O2/Ar ratio and should be <2 mL/min. Fractionation of oxygen between the liquid and gas phase of the air-saturated water was found to be similar to that of earlier reports. The advantages of this method over existing techniques include rapid collection of samples (30 min/sample), high efficiency in extraction of gases from the liquid phase, and the lack of a sample preparation step (e.g. degassing). Copyright © 2006 John Wiley & Sons, Ltd. [source]

Treatment methods for the determination of ,2H and ,18O of hair keratin by continuous-flow isotope-ratio mass spectrometry

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2005
Gabriel J. Bowen
The structural proteins that comprise ,90% of animal hair have the potential to record environmentally and physiologically determined variation in ,2H and ,18O values of body water. Broad, systematic, geospatial variation in stable hydrogen and oxygen isotopes of environmental water and the capacity for rapid, precise measurement via methods such as high-temperature conversion elemental analyzer/isotope ratio mass spectrometry (TC/EA-IRMS) make these isotope systems particularly well suited for applications requiring the geolocation of hair samples. In order for such applications to be successful, however, methods must exist for the accurate determination of hair ,2H and ,18O values reflecting the primary products of biosynthesis. Here, we present the results of experiments designed to examine two potential inaccuracies affecting ,2H and ,18O measurements of hair: the contribution of non-biologic hydrogen and oxygen to samples in the form of sorbed molecular water, and the exchange of hydroxyl-bound hydrogen between hair keratin and ambient water vapor. We show that rapid sorption of molecular water from the atmosphere can have a substantial effect on measured ,2H and ,18O values of hair (comprising ,7.7% of the measured isotopic signal for H and up to ,10.6% for O), but that this contribution can be effectively removed through vacuum-drying of samples for 6 days. Hydrogen exchange between hair keratin and ambient vapor is also rapid (reaching equilibrium within 3,4 days), with 9,16% of the total hydrogen available for exchange at room temperature. Based on the results of these experiments, we outline a recommended sample treatment procedure for routine measurement of ,2H and ,18O in mammal hair. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Investigating cultural heterogeneity in San Pedro de Atacama, northern Chile, through biogeochemistry and bioarchaeology

AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 4 2009
Kelly J. Knudson
Abstract Individuals living in the San Pedro de Atacama oases and the neighboring upper Loa River Valley of northern Chile experienced the collapse of an influential foreign polity, environmental decline, and the appearance of a culturally distinct group during the Late Intermediate Period (ca. AD 1,100,1,400). We investigate cultural heterogeneity at the Loa site of Caspana through analyses of strontium and oxygen isotopes, cranial modification styles, and mortuary behavior, integrating biological aspects of identity, particularly geographic origins, with cultural aspects of identity manifested in body modification and mortuary behavior. We test the hypothesis that the Caspana population (n = 66) represents a migrant group, as supported by archeological and ethnographic evidence, rather than a culturally distinct local group. For Caspana archeological human tooth enamel, mean 87Sr/86Sr = 0.70771 ± 0.00038 (1,, n = 30) and mean ,18Oc(V-PDB) = ,3.9 ± 0.6, (1,, n = 16); these isotopic data suggest that only one individual lived outside the region. Material culture suggests that the individuals buried at Caspana shared some cultural affinity with the San Pedro oases while maintaining distinct cultural traditions. Finally, cranial modification data show high frequencies of head shaping [92.4% (n = 61/65)] and an overwhelming preference for annular modification [75.4% (n = 46/61)], contrasting sharply with practices in the San Pedro area. Based on multiple lines of evidence, we argue that, rather than representing a group of altiplano migrants, the Caspana population existed in the region for some time. However, cranial modification styles and mortuary behavior that are markedly distinct from patterns in surrounding areas raise the possibility of cultural heterogeneity and cultural fissioning. Am J Phys Anthropol, 2009. © 2008 Wiley-Liss, Inc. [source]