Stable Oxygen Isotope Analyses Research Articles

Stable oxygen and hydrogen isotope analyses of bowhead whale baleen as biochemical recorders of migration and arctic environmental change

An analysis of the stable isotopes of oxygen (δ18O) and hydrogen (δD) was used to examine the linkage between sea ice concentration and the migration of western arctic bowhead whales (Balaena mysticetus; WABW). We compared δ18O and δD variability along the length of WABW baleen with isotopic values of zooplankton prey from different WABW habitat, with published δ13C and δ15N data, and with historical sea ice records. Zooplankton signatures varied widely (δ18O = −13‰–56‰; δD = −220‰ to −75‰), with regional separation between winter (Bering Sea) and summer (eastern Beaufort Sea) habitats of WABW observable in δD. The δ18O and δD of WABW varied significantly along the length of baleen (δ18O = 8–18‰; δD = −180 to −80‰), confirming seasonal migration and reflecting distinct regional dietary variation in isotopes. WABW migration appears to have varied concomitant with temporal sea ice concentration (SIC) changes; in years with high SIC, the difference in δD of WABW baleen between seasonal habitats was significantly greater than low SIC periods. This work shows that SIC is not only a determinant of habitat accessibility for WABW, but baleen may also be a record of historical SIC and Arctic climate.

Isotopic Evidence for Marine Consumption and Mobility in the Atacama Desert (Quillagua, Northern Chile)

AbstractArchaeological research in the Atacama Desert has recovered evidence of considerable cultural variability. This variability seems to have increased during the Late Intermediate Period (AD 950–1400). The oasis of Quillagua, located at the margins of the Loa River in northern Chile, between the Andes and the coast (70 km from the Pacific Ocean), has shown important evidence regarding this cultural diversity. The variety in the archaeological evidence found at Quillagua has been interpreted as the result of two different cultural influences at the oasis: the Pica‐Tarapacá who occupied the coastal and inland regions to the north of Quillagua and the Atacama who occupied the oasis and fertile areas southeast of Quillagua. Here, we present the results of stable carbon, nitrogen and oxygen isotope analyses of 23 individuals recovered from the Cementerio Oriente in Quillagua, in order to test whether the observed cultural variability is also reflected in diet and mobility patterns. Results from carbon and nitrogen isotope measurements indicate the importance of marine protein, as well as a contribution of maize in the diet of some individuals. Four individuals show low δ18O values, suggesting a possible highland or non‐local origin, whereas values for the remaining individuals are consistent with lowland populations. Together, the results support the idea that the Quillagua oasis represented an important site of interaction between the Tarapacá and Atacama cultures, with close contacts with the coast but also with the presence of individuals from the highlands. Copyright © 2015 John Wiley & Sons, Ltd.

Tracing formation and durability of calcite in a Punic–Roman cistern mortar (Pantelleria Island, Italy)

Ancient hydraulic lime mortar preserves chemical and isotopic signatures that provide important information about historical processing and its durability. The distribution and isotopic composition of calcite in a mortar of a well-preserved Punic–Roman cistern at Pantelleria Island (Italy) was used to trace the formation conditions, durability, and individual processing periods of the cistern mortar. The analyses of stable carbon and oxygen isotopes of calcite revealed four individual horizons, D, E, B-1 and B-2, of mortar from the top to the bottom of the cistern floor. Volcanic and ceramic aggregates were used for the production of the mortar of horizons E/D and B-1/B-2, respectively. All horizons comprise hydraulic lime mortar characterized by a mean cementation index of 1.5 ± 1, and a constant binder to aggregate ratio of 0.31 ± 0.01. This suggests standardized and highly effective processing of the cistern.The high durability of calcite formed during carbonation of slaked lime within the matrix of the ancient mortar, and thus the excellent resistance of the hydraulic lime mortar against water, was documented by (i) a distinct positive correlation of δ18Ocalcite and δ13Ccalcite; typical for carbonation through a mortar horizon, (ii) a characteristic evolution of δ18Ocalcite and δ13Ccalcite through each of the four mortar horizons; lighter follow heavier isotopic values from upper to lower part of the cistern floor, and (iii) δ18Ocalcite varying from −10 to −5 ‰ Vienna Pee Dee belemnite (VPDB). The range of δ18Ocalcite values rule out recrystallization and/or neoformation of calcite through chemical attack of water stored in cistern.The combined studies of the chemical composition of the binder and the isotopic composition of the calcite in an ancient mortar provide powerful tools for elucidating the ancient techniques and processing periods. This approach helps to evaluate the durability of primary calcite and demonstrates the importance of calcite as a proxy for chemical attack and quality of the ancient inorganic binder.

Estimation of Geographical Origin of Sake by Oxygen Stable Isotope Analysis

Estimation of Geographical Origin of Sake by Oxygen Stable Isotope Analysis

Geological setting and paleoecology of the Upper Cretaceous Bench 19 Marine Vertebrate Bonebed at Bentiaba, Angola

AbstractThe Bench 19 Bonebed at Bentiaba, Angola, is a unique concentration of marine vertebrates preserving six species of mosasaurs in sediments best correlated by magnetostratigraphy to chron C32n.1n between 71.4 and 71.64 Ma. The bonebed formed at a paleolatitude near 24°S, with an Atlantic width at that latitude approximating 2700 km, roughly half that of the current width. The locality lies on an uncharacteristically narrow continental shelf near transform faults that controlled the coastal outline of Africa in the formation of the South Atlantic Ocean. Biostratigraphic change through the Bentiaba section indicates that the accumulation occurred in an ecological time dimension within the 240 ky bin delimited by chron 32n.1n. The fauna occurs in a 10 m sand unit in the Mocuio Formation with bones and partial skeletons concentrated in, but not limited to, the basal 1–2 m. The sediment entombing the fossils is an immature feldspathic sand shown by detrital zircon ages to be derived from nearby granitic shield rocks. Specimens do not appear to have a strong preferred orientation and they are not concentrated in a strand line. Stable oxygen isotope analysis of associated bivalve shells indicates a water temperature of 18.5°C. The bonebed is clearly mixed with scattered dinosaur and pterosaur elements in a marine assemblage. Gut contents, scavenging marks and associated shed shark teeth in the Bench 19 Fauna indicate biological association and attrition due to feeding activities. The ecological diversity of mosasaur species is shown by tooth and body-size disparity and by δ13C analysis of tooth enamel, which indicate a variety of foraging areas and dietary niches. The Bench 19 Fauna was formed in arid latitudes along a coastal desert similar to that of modern Namibia on a narrow, tectonically controlled continental shelf, in shallow waters below wave base. The area was used as a foraging ground for diverse species, including molluscivorusGlobidens phosphaticus, small species expected near the coast, abundantPrognathodon kianda, which fed on other mosasaurs at Bench 19, and species that may have been transient and opportunistic feeders in the area.

Isotopic evidence for divergent diets and mobility patterns in the Atacama Desert, northern Chile, during the Late Intermediate Period (AD 900-1450).

The decline of the Tiwanaku state saw the emergence of two new cultures-Pica-Tarapacá and Atacama-during the Late Intermediate Period in northern Chile. Archeological evidence suggests that both groups practised maize agriculture and pastoralism, but that their interaction zones differed significantly. Marine resources are common at Pica-Tarapacá sites, even those far from coast, while Atacama sites in the desert oases and precordilleran area seem to have directed their networks towards the highlands. Here we apply stable carbon, nitrogen, and oxygen isotope analysis on human bone and enamel to test dietary patterns and residential mobility at two sites, Pica 8 and Quitor 6, representing the Pica-Tarapacá and Atacama cultures, respectively. Our results show that diet at the two sites indeed differed: significant but variable consumption of marine resources and maize is indicated at Pica 8, despite being an inland site, while diet at Quitor 6 was based mainly on terrestrial resources. The use of seabird guano and llama dung as fertilizers and extreme aridity may have contributed to the high nitrogen isotope values observed in Pica 8 humans. The δ(18) O values in Pica 8 individuals are generally lower than for Quitor in spite of its greater distance from the Andes. All three isotopes suggest the presence of at least five nonlocals in the 30 measured at Pica 8. This evidence for human mobility is consistent with the high levels of trade and interaction observed in the archeological record, and begins to quantify the degree of movement of specific individuals.

A potential global boundary stratotype section and point (GSSP) for the Tarentian Stage, Upper Pleistocene, from the Taranto area (Italy): Results and future perspectives

We present new data collected at the Fronte composite section near Taranto, where the Upper Pleistocene marine sedimentary succession is continuously exposed. Above a fossiliferous calcarenite yielding the “Senegalese” fauna, and abundant Cladocora, the 230Th/U age of which is consistent with Marine Isotope Stage (MIS) 5, a 6.25 m thick pelitic unit is characterized by lithologically homogeneous marine sediments in which stable oxygen isotope, micropaleontological and palynological analyses suggest a long and undisturbed sedimentary interval across the Marine Isotope Stage (MIS) 5.5 peak (plateau). High sedimentation rates and a successful paleomagnetic pilot study indicate the probability of locating brief chronostratigraphic events useful for correlation with both continental and marine successions elsewhere. These results show the composite section to be a very promising candidate in the search for the Upper Pleistocene global boundary stratotype section and point (GSSP).

Biscayne aquifer drinking water (USGS45): a new isotopic reference material for δ2H and δ18O measurements of water.

As a result of the scarcity of isotopic reference waters for daily use, a new secondary isotopic reference material for international distribution has been prepared from drinking water collected from the Biscayne aquifer in Ft. Lauderdale, Florida. This isotopic reference water was filtered, homogenized, loaded into glass ampoules, sealed with a torch, autoclaved to eliminate biological activity, and measured by dual-inlet isotope-ratio mass spectrometry. This reference material is available by the case of 144 glass ampoules containing either 4 mL or 5 mL of water in each ampoule. The δ(2)H and δ(18)O values of this reference material are -10.3 ± 0.4‰ and -2.238 ± 0.011‰, respectively, relative to VSMOW, on scales normalized such that the δ(2)H and δ(18)O values of SLAP reference water are, respectively, -428 and -55.5‰. Each uncertainty is an estimated expanded uncertainty (U = 2uc ) about the reference value that provides an interval that has about a 95% probability of encompassing the true value. This isotopic reference material, designated as USGS45, is intended as one of two isotopic reference waters for daily normalization of stable hydrogen and oxygen isotopic analysis of water with an isotope-ratio mass spectrometer or a laser absorption spectrometer. Published in 2014. This article is a U.S. Government work and is in the public domain in the USA.

Eocene oil shales from Jordan - their petrography, carbon and oxygen stable isotopes

ABSTRACT Sediment petrographic studies combined with carbon and oxygen stable-isotope analyses are considered to be powerful tools in deciphering the depositional and diagenetic history of carbonate rocks. These studies have been found valuable for understanding the environmental controls and global changes of climate and oceanography. Two cores of Eocene bituminous marls (OS-22 and OS-23) from central Jordan with thicknesses of 222.4 m and 256.3 m, respectively, were logged. A total of 103 thin sections were analyzed for sediment petrographic investigations. Another 295 bulk rock samples from Core OS-23 were selected for stable-isotope analysis (δ13C, δ18O). The two cores show similar lithologic variations that correspond to third-order sea-level changes. The sediment petrographic study reveals the presence of six major microfacies that range from mudstones to grainstones. The distribution of these six types of microfacies in the two cores indicates an overall shallow-marine environment in an interior carbonate-platform setting. Within this environment, conditions fluctuated between open and restricted marine. The stratigraphic variability of the carbon-isotope data of Core OS-23 reflects a highly dynamic depositional system that exhibits a variable rate of organic matter accumulation in the sediments, which can be directly linked to the interaction between primary organic-matter burial and oxidative weathering of reworked organic matter. Within the overall diagenetically controlled δ18Ocarb profile an excursion is observed for a specifically enriched organic matter interval. This excursion is believed to coincide with the Middle Eocene Climatic Optimum (MECO), suggesting that next to seawater, porewaters were influenced by this event and making it the first record of this event in the region.

POROSITY PRESERVATION DUE TO AUTHIGENIC CHLORITE COATINGS IN DEEPLY BURIED UPPER TRIASSIC XUJIAHE FORMATION SANDSTONES, SICHUAN BASIN, WESTERN CHINA

Non‐marine sandstones in the Upper Triassic Xujiahe Formation form an important reservoir unit in the Sichuan Basin, western China. Widespread authigenic chlorite cement is present in the second and fourth members of the formation, referred to as the Xu II and IV members. This study, based on data from 12 wells from three gasfields, focusses on chlorite development and evolution and attempts to evaluate its influence on reservoir quality. Data included results of X‐ray diffraction (XRD) and electron microprobe analyses (EMPA), scanning electron microscopy (SEM), and stable carbon and oxygen isotope analyses. The results showed that chlorite coatings preserve primary pore spaces in the sandstones by inhibiting the nucleation of quartz cements on grain surfaces. Iron for chlorite growth came from the dissolution of Fe‐rich magmatic rocks derived from the palaeo‐Longmenshan fold‐belt, from dissolved and colloidal iron which had been precipitated in the Xujiahe Formation in a fluvio‐deltaic environment, and from compacting mudstones in other pars of the formation.The chlorite initially precipitated from pore waters during eodiagenesis (< 70 °C; < 2 km burial depth). During mesodiagenesis (>70 °C, > 2 km), the chlorite was modified due to exposure to Mg‐rich fluids derived from the underlying carbonate‐dominated Leikoupo Formation. Thus the Mg content of chlorite in the Xu II member increases with depth. However this phenomenon was not observed in the Xu IV member.The effects of authigenic chlorite on the sandstones' petrophysical properties were evaluated from correlations between chlorite content and porosity. Optimum thicknesses for chlorite coatings range from 5 to 10 microns. Thicker or thinner coatings appear to be less capable of preserving primary porosity and permeability.

Assessing life history from commingled assemblages: the biogeochemistry of inter-tooth variability in Bronze Age Arabia

Stable isotopes represent a remarkable means of assessing the life histories of individuals in the archaeological record, primarily by taking advantage of multiple skeletal tissues that form and remodel throughout life. However, this methodological tool also has the potential to provide crucial information on the life histories of individuals represented only by commingled, fragmentary, and otherwise isolated human skeletal remains, particularly when more traditional methods of evaluation are not possible. In this study, a sequential analysis of radiogenic strontium (87Sr/86Sr) and stable oxygen (δ18O) isotopes of associated molars from the in situ mandibular or maxillary fragments of 19 commingled individuals from multiple Bronze Age tombs in the United Arab Emirates was undertaken in order to examine temporal changes in mobility at the level of the individual. The majority of individuals display little difference in inter-tooth isotope ratios, suggesting a general lack of residential mobility between early childhood and late adolescence, an unexpected result given abundant evidence (artifactual and written) for a population actively engaged in both regional and interregional trade in the third millennium BC. However, two individuals from the Emirate of Fujairah demonstrate disparate inter-tooth 87Sr/86Sr values – likely indicative of some migration event – which calls into question the supposed cultural isolation of the region during the second millennium BC.

USGS48 Puerto Rico precipitation – a new isotopic reference material for δ2H and δ18O measurements of water

A new secondary isotopic reference material has been prepared from Puerto Rico precipitation, which was filtered, homogenised, loaded into glass ampoules, sealed with a torch, autoclaved to eliminate biological activity, and calibrated by dual-inlet isotope-ratio mass spectrometry. This isotopic reference material, designated as USGS48, is intended to be one of two isotopic reference waters for daily normalisation of stable hydrogen (δ2H) and stable oxygen (δ18O) isotopic analysis of water with a mass spectrometer or a laser absorption spectrometer. The δ2H and δ18O values of this reference water are−2.0±0.4 and−2.224±0.012 ‰, respectively, relative to Vienna Standard Mean Ocean Water on scales normalised such that the δ2H and δ18O values of Standard Light Antarctic Precipitation reference water are−428 and−55.5 ‰, respectively. Each uncertainty is an estimated expanded uncertainty (U=2uc) about the reference value that provides an interval that has about a 95 % probability of encompassing the true value. This isotopic reference water is available by the case of 144 glass ampoules containing 5 mL of water in each ampoule.

Benthic foraminiferal δ 13C minimum events in the southeastern Okhotsk Sea over the last 180 ka

A total of six δ 13C minimum events, i.e., VI, V, IV, III, II, and I, were observed via a stable carbon and oxygen isotope analysis of infaunal benthic foraminifera Uvigerina spp. in gravity core OS03-1 in the southeastern Okhotsk Sea over the last 180 ka. These events occurred at 112–109, 102–90, 85–76, 57–54, 44–40, and 17–10 ka BP. The largest negative excursions reached 2.5 ‰ in event V and were greater than 1 ‰ in the other events. We proposed that all δ 13C minimum events were caused by the increase in sea surface water productivity, the weakened formation of Okhotsk Sea intermediate water, and the enhancement of the oxygen minimum zone. The negative excursions were unaffected by methane hydrate destabilization and subsequent methane release based on the results obtained by using archaeal lipid markers.

The Volterran Urns: Etruscan Painting and Travertine Supply

The artistic evolution of the Volterran cinerary urns is a good representation of Etruscan painting from the fourth to the first century bc. The interest generated by this type of object directed our research towards the study of the Volterran artefacts, including the analysis of the pigments as well as that of the rocks used for the coffers. The entire colour range shown by the painted urns has been sampled and investigated through Raman microscopy and scanning electron microscopy. Rock samples were taken both from the urns and from outcrops in ancient carbonate rock quarries near Volterra, from where they may potentially have been sourced. A set of 30 samples was collected and submitted to stable carbon and oxygen isotope analyses. The results obtained showed that the pigments used for the decoration of the Volterran urns were basically constituted by red ochre, Egyptian blue, carbon black and gypsum. The identification of lead‐based pigments and barium sulphates further informed us about old restorations undergone by several urns. As far as the provenance issue is concerned, the isotopic data indicate that the rocks used for the four urns were favourably comparable to those outcropping at Pignano, while two other urns were more similar to those sampled along the Elsa River at Colle Val d'Elsa.

INSIGHTS INTO THE DISTRIBUTION OF SHALLOW-MARINE TO ESTUARINE EARLY MIOCENE OYSTERS FROM SOUTHWESTERN PATAGONIA: SEDIMENTOLOGIC AND STABLE ISOTOPE CONSTRAINTS

Fil: Cuitino, Jose Ignacio. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias Geologicas; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Geociencias Basicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Basicas, Aplicadas y Ambientales de Buenos Aires; Argentina

Insights into the habitat of Middle Permian pareiasaurs (Parareptilia) from preliminary isotopic analyses

Pareiasaurs were an abundant group of large herbivores during Middle and Late Permian times. The habitat of pareiasaurs has proven enigmatic, and ecological interpretations from anatomical and taphonomic data have included aquatic, semi-aquatic to fully terrestrial lifestyles. Insight into the ecology of extinct taxa can also be gained from stable isotope analyses, and interpretations benefit from studies of multiple, coeval groups. Here, we report the first stable carbon and oxygen isotope analyses from the enamel, dentine and bone of pareiasaurs and contemporaneous therapsids (dinocephalians and therocephalians), in specimens recovered from the Permian Tapinocephalus to lower Pristerognathus Assemblage Zones of South Africa. Previous ecological inferences for dinocephalians (riparian to terrestrial) and therocephalians (terrestrial) are less ambiguous than reconstructions for pareiasaurs and provide an independent reference for interpreting stable isotope measurements. Oxygen isotopes of enamel carbonate were indistinguishable between pareiasaurs and therocephalians, which had higher values than dinocephalians. The data suggest that dinocephalians and pareiasaurs (megaherbivores) inhabited different ecological niches and that pareiasaurs may have shared a terrestrial habitat with therocephalians (carnivores). Our results agree with earlier suggestions of a terrestrial lifestyle among pareiasaurs and provide evidence of niche partitioning among large coeval Capitanian herbivores of South Africa.

Systematics and phylogeny of middle Miocene Cervidae (Mammalia) from Mae Moh Basin (Thailand) and a paleoenvironmental estimate using enamel isotopy of sympatric herbivore species

ABSTRACT The primitive deer (subfamily Lagomerycinae) Lagomeryx and Stephanocemas are characterized primarily by their palmate antlers. Two lagomerycines, Lagomeryx manai, sp. nov., and Stephanocemas rucha, are described for the first time from Q and K coal layers of the late middle Miocene (13.4–13.2 Ma) Mae Moh Basin in northern Thailand. A species-level phylogeny of the Ligeromeryx-Lagomeryx clade, based on cranial appendages, reconstructs Lagomeryx manai, n. sp., as a derived species of Lagomeryx, sister group of Lagomeryx complicidens. This study suggests that the large species of Lagomeryx are restricted geographically to Asia and dispersed to Southeast Asia at the latest during late middle Miocene, where they are represented by Lagomeryx manai, n. sp. The paleoenvironmental studies of five Mae Moh mammalian taxa, a cervid (Lagomeryx manai, n. sp.), an indeterminate bovid, a suid (Conohyus thailandicus), a rhinoceros (Gaindatherium sp.), and a proboscidean (Stegolophodon sp.), investigated with stable carbon and oxygen isotope analyses of tooth enamel, indicate that the Mae Moh mammals inhabited a wide range of habitats from woodlands to grasslands in a C3-plant-dominated environment. The new species of Lagomeryx seems to have been living in an open environment, contrary to its European relatives. The serial isotopic samples also support that Mae Moh herbivores probably lived in a low-seasonal climate during the late middle Miocene of northern Thailand. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP

Paleoecology of the K-Pg mass extinction survivor Guembelitria (Cushman): isotopic evidence from pristine foraminifera from Brazos River, Texas (Maastrichtian)

The late Maastrichtian sediments of the Mullinax-1 and Mullinax-3 boreholes from Brazos River, Texas, offer pristine material. These cores are prime candidates for providing an extraordinary window into the ecology of Guembelitria, a key genus in the K/Pg mass extinction event, as well as information on the habitats of other neritic species. Stable oxygen and carbon isotope analyses were performed on six planktic species (Guembelitria cretacea, Globigerinelloides asper, Heterohelix globulosa, Paraspiroplecta navarroensis, Pseudoguembelina costulata, Rugoglobigerina rugosa) and three benthic genera (Gavelinella, Cibicides, and Lenticulina). Our records support the contention that Guembelitria was fully planktic, as indicated by its δ18O values, which overlap the other planktic species, despite its possible origin from a tychopelagic benthic ancestor. However, Guembelitria is distinctly ranked very low in δ13C values, which overlap the benthic records. The anomalously low δ13C values of Guembelitria may represent an isotopic disequilibrium due to fast shell growth, like in its modern analogue Gallitellia vivans. Another explanation may be that these values are attributable to a neustonic life mode in the uppermost part of the oceans, where photosynthesis is inhibited by high UV and the near absence of nutrients. Because these waters are not photosynthetically depleted, calcification using carbon directly from these waters should yield δ13C values consistent with those found in Guembelitria. The ecological strategy that Guembelitria species used to deal with the nutrient-poor surface-water environments was an opportunistic blooming during stressful times of Maastrichtian global warming events and later during the K-Pg catastrophe.

Lake Louise Water (USGS47): A new isotopic reference water for stable hydrogen and oxygen isotope measurements

Because of the paucity of isotopic reference waters for daily use, a new secondary isotopic reference material has been prepared from Lake Louise water from Alberta, Canada, for international distribution. This water was filtered, homogenized, loaded into glass ampoules, sealed with a torch, autoclaved to eliminate biological activity, and measured by dual-inlet isotope-ratio mass spectrometry. This isotopic reference water is available by the case of 144 glass ampoules containing 5 mL of water in each ampoule. The δ(2)H and δ(18)O values of this reference water are -150.2 ± 0.5‰ and -19.80 ± 0.02‰, respectively, relative to VSMOW, on scales normalized such that the δ(2)H and δ(18)O values of SLAP reference water are, respectively, -428 and -55.5‰. Each uncertainty is an estimated expanded uncertainty (U = 2uc) about the reference value that provides an interval that has about a 95% probability of encompassing the true value. This isotopic reference material, designated as USGS47, is intended as one of two isotopic reference waters for daily normalization of stable hydrogen and stable oxygen isotopic analysis of water with a mass spectrometer or a laser absorption spectrometer. Published in 2013. This article is a U.S. Government work and is in the public domain in the USA.

USGS46 Greenland Ice Core Water – A New Isotopic Reference Material for δ2H and δ18O Measurements of Water

Ice core from Greenland was melted, filtered, homogenised, loaded into glass ampoules, sealed, autoclaved to eliminate biological activity, and calibrated by dual‐inlet isotope‐ratio mass spectrometry. This isotopic reference material (RM), USGS46, is intended as one of two secondary isotopic reference waters for daily normalisation of stable hydrogen (δ2H) and stable oxygen (δ18O) isotopic analysis of water with a mass spectrometer or a laser absorption spectrometer. The measured δ2H and δ18O values of this reference water were −235.8 ± 0.7‰ and −29.80 ± 0.03‰, respectively, relative to VSMOW on scales normalised such that the δ2H and δ18O values of SLAP reference water are, respectively, −428 and −55.5‰. Each uncertainty is an estimated expanded uncertainty (U = 2uc) about the reference value that provides an interval that has about a 95‐percent probability of encompassing the true value. This reference water is available in cases containing 144 glass ampoules that are filled with either 4 ml or 5 ml of water per ampoule.