Use Of Oxygen Isotopes Research Articles

An integrated carbon and oxygen isotope approach to reconstructing past environmental variability in the northeast Atlantic Ocean

The combined influence of temperature and the isotopic composition of the seawater (δ18Ow) often precludes the use of oxygen isotope (δ18O) records, derived from marine carbonates, to reconstruct absolute seawater temperatures, without the application of an independent δ18Ow proxy. Here we investigate the application of carbon isotope records (δ13Cshell), derived from the long-lived marine bivalve Glycymeris glycymeris, as a proxy for δ18Ow variability. Our analyses indicate G. glycymeris δ13Cshell data derived from growth increments >20 years of age contain strong ontogenetic trends (−0.013‰ yr−1, R = 0.98, P < 0.001, N = 51). These analyses demonstrate that, coupled with the ontogenetic trends, 54% of the variability in G. glycymeris δ13Cshell records can be explained by a combination of the marine Suess effect and physical (salinity and riverine input) and biological processes (primary production). The application of these δ13Cshell data in conjunction with co-registered δ18Oshell and growth increment width series, each of which have been shown to be sensitive to seawater temperature and primary productivity respectively, can therefore provide new insights into past environmental variability and help constrain uncertainties on reconstructions of past seawater temperature variability.

Use of oxygen isotopes to differentiate between nitrous oxide produced by fungi or bacteria during denitrification.

Fungal denitrifiers can contribute substantially to N2 O emissions from arable soil and show a distinct site preference for N2 O (SP(N2 O)). This study sought to identify another process-specific isotopic tool to improve precise identification of N2 O of fungal origin by mass spectrometric analysis of the N2 O produced. Three pure bacterial and three fungal species were incubated under denitrifying conditions in treatments with natural abundance and stable isotope labelling to analyse the N2 O produced. Combining different applications of isotope ratio mass spectrometry enabled us to estimate the oxygen (O) exchange accelerated by denitrifying enzymes and the ongoing microbial pathway in parallel. This experimental set-up allowed the determination of δ18 O(N2 O) values and isotopic fractionation of O, as well as SP(N2 O) values, as a perspective to differentiate between microbial denitrifiers. Oxygen exchange during N2 O production was lower for bacteria than for fungi, differed between species, and depended also on incubation time. Apparent O isotopic fractionation during denitrification was in a similar range for bacteria and fungi, but application of the fractionation model indicated that different enzymes in bacteria and fungi were responsible for O exchange. This difference was associated with different isotopic fractionation for bacteria and fungi. δ18 O(N2 O) values depend on isotopic fractionation and isotopic fractionation may differ between processes and organism groups. By comparing SP(N2 O) values, O exchange and the isotopic signature of precursors, we propose here a novel tool for differentiating between different sources of N2 O.

Modeling the oxygen isotope composition of the Antarctic ice sheet and its significance to Pliocene sea level

Abstract Recent estimates of global mean sea level based on the oxygen isotope composition of mid-Pliocene benthic foraminifera vary from 9 to 21 m above present, which has differing implications for the past stability of the Antarctic ice sheet during an interval with atmospheric CO2 comparable to present. Here we simulate the oxygen isotope composition of the Antarctic ice sheet for a range of configurations using isotope-enabled climate and ice sheet models. We identify which ice sheet configurations are consistent with the oxygen isotope record and suggest a maximum contribution from Antarctica to the mid-Pliocene sea-level highstand of ∼13 m. We also highlight that the relationship between the oxygen isotope record and sea level is not constant when ice is lost from deep marine basins, which has important implications for the use of oxygen isotopes as a sea-level proxy.

Local water source variation and experimental Chicha de Maíz brewing: Implications for interpreting human hydroxyapatite δ18O values in the Andes

Oxygen isotope data (expressed as δ18O values) recovered from human skeletal remains have been the central focus of a number of archeological analyses tracking human migration. However, in the Andes the use of oxygen isotopes to investigate residential mobility is subject to two issues addressed in this study: 1) local variation in water sources and 2) pre-consumption processing of water. To explore these factors we sampled a wide variety of water sources in the Moche watershed of north coastal Peru and experimentally and ethnographically produced chicha de maíz, a traditional brewed beverage. Our data indicate an unexpected spatial pattern in Moche valley water source δ18O values, and identify springs as an important influence on river water. Using chicha de maíz as an example of pre-consumption processing of water, we find that brewed beverages may impact human δ18O values. Together these data indicate that in the Andes the consumption of chicha de maíz has the potential to swamp spatial variation in water source δ18O values. Therefore, we cannot assume that the identification of different δ18O values in the remains of Andean groups necessarily indicates the presence of migrants.

Control of ambient pH on growth and stable isotopes in phytoplanktonic calcifying algae

The present work examines the relationship between pH-induced changes in growth and stable isotopic composition of coccolith calcite in two coccolithophore species with a geological perspective. These species (Gephyrocapsa oceanica and Coccolithus pelagicus) with differing physiologies and vital effects possess a growth optimum corresponding to average pH of surface seawater in the geological period during their first known occurrence. The “ancestral” C. pelagicus has much wider pH tolerance in terms of growth rates than the more recently evolved G. oceanica. Diminished growth rates are explained by the challenge of proton translocation into the extracellular environment at low pH and enhanced aqueous CO2 limitation at high pH. Reducing the cell dynamics in this way leads to a lower degree of oxygen isotopic disequilibrium in G. oceanica. In contrast, the slower growing species C. pelagicus, which typically precipitates near-equilibrium calcite, does not show any modulation of oxygen isotope signals with changing pH. Overall, carbon and oxygen isotope compositions are best explained by the degree of utilization of the internal dissolved inorganic carbon (DIC) pool and the dynamics of isotopic reequilibration inside the cell. Thus, the “carbonate ion effect” may not apply to coccolithophores. This difference with foraminifera can be traced to different modes of DIC incorporation into these two distinct biomineralizing organisms. From a geological perspective, these findings have implications for refining the use of oxygen isotopes to infer more reliable sea surface temperatures (SSTs) from fossil carbonates and contribute to a better understanding of how climate-relevant parameters are recorded in the sedimentary archive.

Oxygen isotopes in Molluscan shell: Applications in environmental archaeology

Oxygen isotope geochemistry of Molluscan shell is an essential part of environmental archaeology and over the last decade has contributed significantly to the understanding of the past inhabitants of our planet. From the analysis of collected (and disposed of) shells we can gain information on environmental data from the species assemblages and also from the shell chemistry. In particular, intra-seasonal information can be gained from shells by analysing the isotope composition of the shell from successive growth increments. Here, we describe some of the recent developments in the use of oxygen isotopes in environmental archaeology. In particular, we consider preservation and sampling and describe how δ18O can provide us with information on seasonal climate, season of collection as well as changes in global climate.

The combined use of oxygen isotopes and microwear in sheep teeth to elucidate seasonal management of domestic herds: the case study of Çatalhöyük, central Anatolia

This paper presents and tests a model designed to investigate how off-site herd management developed in settled pre-historic societies. The model is constructed from data collected from traditionally raised local sheep, acting as an interpretive link to published data. The modern comparator was small, but plausible results allow modelling of the archaeological data to be explored. Birth seasonality and herding location are identified through modelled patterns in oxygen isotope data in tooth enamel, and diet just before death by microwear in the same tooth. In combination, these allow aspects of seasonal management of breeding, fallow and slaughter herd sections to be interpreted. Novel practices are discussed in comparison local wild sheep ethology. The case study is Neolithic Çatalhöyük (7400–6200 cal BC) in central Anatolia. Its location provided the opportunity for different parts of the landscape to be used for herding, although choice might have been socially constrained. Data are taken from 72 specimens; the results suggest settlement-wide preference for a suite of practices that kept herds within a day of the settlement and that maintained breeding cycle synchrony with optimal resource availability. Chronological analysis suggests birth season manipulation was tried but rejected, whilst hay or cereal fodder was introduced and became increasingly important. It is argued that herding was probably on dedicated pasture on the arable fringes rather than in closer integration on ‘garden plots’, as there is no evidence of field-edge weed diets and little evidence of adjusting the birth season to accommodate the crop cycle.

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

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 δ18O values in dental enamel of archaeological sheep are assessed for post‐depositional diagenetic effects and compared with seasonal δ18O 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.

Primitive oxygen-isotope ratio recorded in magmatic zircon from the Mid-Atlantic Ridge

The oxygen-isotope composition of the Earth’s upper mantle is an important reference for understanding mantle and crust geochemical cycles. Olivine is the most commonly used mineral for determining the influence of crustal processes on the oxygen-isotope ratio (δ18O) of primitive rocks, however it is an uncommon mineral in continental crust and readily alters at or near Earth’s surface. Here we report the first measurements of oxygen-isotope ratios in zircon from oceanic crust exposed at a mid-ocean ridge. Measurements of δ18O and trace elements were made by ion microprobe on zircon in polished rock chips of gabbro and veins in serpentinized peridotite drilled from the Mid-Atlantic Ridge. The zircon grains contain both oscillatory and sector growth zoning, features characteristic of magmatic zircon. Values of δ18O (zircon) = 5.3 ± 0.8‰ (2 st. dev., n = 68) for the population are consistent with the interpretation that these grains are igneous in origin and formed in high-temperature isotopic equilibrium with mantle oxygen. The δ18O values demonstrate that zircon in oceanic crust preserves primitive δ18O in spite of sub-solidus alteration of the whole rock. The fact that the primitive δ18O (zircon) values fall in a narrow range (5.3 ± 0.8‰) strengthens the use of oxygen isotopes in zircon as a tracer to identify processes of exchange in a wide range of modern and ancient crustal environments, including subducted oceanic crust (eclogite), and also in the oldest known pieces of Earth, >3900 million-year-old detrital zircon grains from Western Australia.

Oxygen Isotopes in the Early Solar System -- A Historical Perspective

The first suggestion for the use of oxygen isotopes in cosmochemistry was that of H. C. Urey and colleagues in 1934, but appropriate instrumentation had not yet been developed. The modern era of oxygen isotope cosmochemistry began with the study of Apollo lunar samples in 1969 and of Allende refractory inclusions in 1973. The large (>5%) variations in 17O/16O and 18O/16O ratios, and small variations in 17O/18O were first interpreted as nucleosynthetic effects, but are now recognized to be the result of chemical processes early in Solar System history. Thus oxygen isotopes provide natural tracers for processes of formation of solid bodies in the inner Solar System. In particular, oxygen isotopes are very useful in recognizing genetic associations among meteorite groups. They also have been valuable in the study of parent body processes, such as metamorphism and aqueous alteration. There is conjecture that the ultimate cause of the oxygen isotope effects may be isotope-selective photodissociation of CO, which will be tested by isotopic measurement of solar oxygen and nitrogen collected in the NASA Genesis mission.

Measurement of infiltration rates in urban sewer systems by use of oxygen isotopes

The paper presents the principle of a method to measure infiltration rates in sewer systems based on the use of oxygen isotopes and its application in Lyon (France). In the urban area of Lyon, significant differences in delta 18O that can reach 3 per thousand are observed between the oxygen isotopic compositions of groundwater originating from Rhone, Saone and from their associated alluvial aquifers. Drinking water supplying Lyon results mainly from pumping in the Rhone alluvial aquifer. Therefore, in some areas, the difference of isotopic composition between wastewater resulting from the consumption of drinking water and local groundwater can be used to measure infiltration in sewer systems. The application in the catchment of Ecully shows that the infiltration flow rate presents strong fluctuations at an hourly scale: it varies between 15 and 40 m3/h. This variability could be explained by non-constant discharges of pumping and by variations of the water level in the sewer.

Use of oxygen isotope to study the transport mechanism during high temperature oxide scale growth

Use of oxygen isotope to study the transport mechanism during high temperature oxide scale growth

Use of oxygen isotope to study the transport mechanism during high temperature oxide scale growth

The examination of high temperature (HT) oxide scale growth mechanisms was performed using secondary ion mass spectrometry (SIMS) and secondary neutral mass spectrometry (SNMS), in conjunction with 16O2/18O2 HT oxidation experiments. Cr2O3, NiO, ZrO2 and Al2O3 were studied because they constitute excellent representative thermally grown oxide scales: they grow by cationic diffusion (Cr2O3, NiO), anionic diffusion (ZrO2) or mixed anionic-cationic diffusion (Al2O3). The oxidation tests were performed first in 16O2 and subsequently in 18O2 at several temperatures (600–1000°C for NiO, 600°C for ZrO2, 1000°C for Cr2O3 and 1100°C for Al2O3). The oxygen isotope distribution observed by SIMS and SNMS profiles are discussed and related with the HT oxidation mechanisms proposed in the literature.

57Fe Mössbauer spectroscopy studies of meteorites: implications for weathering rates, meteorite flux, and early solar system processes

Ordinary chondrite finds, terrestrial age dated using 14C analyses, from different meteorite accumulation sites, have been examined by Mossbauer spectroscopy to quantitatively determine terrestrial oxidation. We observe differences in weathering rates between sites, and also between different chondrite groups. A comparison of weathering over time, and its effect in ‘eroding’ meteorites, together with the number and mass distribution of meteorites in each region, enables us to derive estimates of the number of meteorite falls over a given mass per year. Studies of how the oxygen isotopic composition of samples varies with weathering indicate that incipient alteration may occur without a pronounced isotopic effect, possibly due to weathering of silicates to topotactically oriented smectite confined spaces where the water volume is limited. This finding has profound implications for the use of oxygen isotopes as a tool in understanding water–rock interaction. It also may reconcile previously contradictory data regarding the nebular or asteroidal location of pre-terrestrial aqueous alteration. Finally, Mossbauer spectroscopy is also found to be a useful tool in determining mineral abundance in carbonaceous chondrites, where a fine-grained matrix makes traditional approaches inapplicable. Again, the results have implications for the modification of chondritic materials in the early solar system.

Holocene Climate Inferred from Oxygen Isotope Ratios in Lake Sediments, Central Brooks Range, Alaska

Analyses of sediment cores from two lakes in the central Brooks Range provide temperature and moisture balance information for the past ∼8500 cal yr at century-scale resolution. Two methods of oxygen isotope analysis are used to reconstruct past changes in the effective moisture (precipitation minus evaporation) and temperature. Effective moisture is inferred from oxygen isotope ratios in sediment cellulose from Meli Lake (area ∼0.13 km2, depth 19.4 m). The lake has a low watershed-to-lake-area ratio (7) and significant evaporation relative to input. Summer temperature shifts are based on oxygen isotope analyses of endogenic calcite from Tangled Up Lake (area ∼0.25 km2, depth 3.5 m). This basin has a larger watershed-to-lake-area ratio (91) and less evaporation relative to input. Sediment oxygen isotope analyses from the two sites indicate generally more arid conditions than present prior to ∼6000 cal yr B.P. Subsequently, the region became increasingly wet. Temperature variability is recorded minimally at centennial scale resolution with values that are generally cool for the past ∼6700 cal yr. The timing and direction of climate variability indicated by the oxygen isotope time series from Meli and Tangled Up lakes are consistent with previously established late Holocene glacier advances at ∼5000 cal yr B.P. in the central Brooks Range, and high lake-levels at Birch Lake since ∼5500 cal yr B.P. This unique use of oxygen isotopes reveals both moisture balance and temperature histories at previously undetected high-resolution temporal scales for northern Alaska during the middle to late Holocene.

Oxygen isotopic composition of fossil equid tooth and bone phosphate: an archive of difficult interpretation

Variation in the concentration of the stable isotopes of hydrogen, oxygen and carbon have been tested in continental records as tools for quantitative or semi-quantitative paleoclimatological studies. Among the different methods, the potential use of oxygen isotopes in mammal bone and tooth phosphate has recently been recognized. Measurements carried out on fossil mammal bones of Holocene age and their paleoclimatological interpretation corresponded well with paleontological and paleobotanical records. In the case of considerably older fossils, diagenetic processes may change the primary oxygen isotopic composition of phosphate. Fossil horse bones and teeth (principally of the species Equus stenonis) were studied to ascertain how far back in time fossil mammal remains may be considered reliable material for paleoclimatological studies. The samples come from 13 different locations in southeastern Spain, their age ranging from Maspinian (late Pleistocene) to Middle Villafranchian (Pliocene). Apart from the variations of the δ 18O(PO 4 3−) values which may be related to climatic changes, it is apparent that the isotopic composition of bones and teeth from the same deposit are frequently rather different from one another. The isotopic differences range from a few tenths of one % to several %. This suggests a strong influence of taphonomy over the measured isotopic values of fossils in each deposit. Time can be considered neither the only variable nor the most important one responsible for the change of the primary isotopic composition of fossils. Under these conditions it is rather difficult to establish lower or upper limits for the age of fossils to be studied for reliable paleoclimatological information since the limits are directly related to taphonomic history. This, in turn, is related to local environmental conditions and not only to the age of fossils.

Oxygen isotopes in living mammal's bone phosphate: Further results

The potential use of oxygen isotopes in mammal bone phosphate to study paleoclimates has been recognized since a few years. It has been proven that the δ 18O(PO 4 3−) of some mammal species is related to the mean δ 18O of local meteoric water, each species showing a specific linear relationship. We report here some measurements of the oxygen isotopic composition of bone phosphate from living specimens of deer, mice, cattle and sheep coming from different areas with different mean annual values of local meteoric water. The oxygen isotopic composition of body water (blood water) of some of these specimens has also been measured. Linear relationships between the δ 18O of bone phosphate, the δ 18O of blood water and the mean δ 18O of local meteoric water have been found, as in the case of the previously studied specimens of humans, pigs and rats. The slopes of the calculated equations for the bone phosphate-meteoric water relationships are the following: 0.79 (wood mice), 1.01 (cattle), 1.13 (deer) and 1.48 (sheep). The calculated phosphate-water fractionation factors are quite homogeneous, ranging from 1.0172 to 1.0175. These values are very close to those which may be calculated for isotopic equilibrium conditions between bone phosphate and body water. Fossil bones from the studied species may now be used for paleoclimatological and paleohydrological studies.

Thermal History of Sandstones and Shales: Oxygen Isotope and K/Ar Evidence: ABSTRACT

The combined use of oxygen isotope and K/Ar dating can yield information about the diagenetic history of clay minerals in shales and sandstones. In the Tertiary shale sequences of the United States Gulf Coast, in which the dominant detrital clay mineral is mixed-layer illite/smectite, the progressive conversion of expandable clay layers to illite layers can be monitored by the isotope systematics. Oxygen isotopes of fine-grained clay and quartz approach equilibrium with one another, raising the (as yet unrealized) possibility of an O-isotope geothermometer. Fine-grained quartz becomes isotopically zoned as detrital grains are overgrown by diagenetic quartz that forms, accompanying the smectite-to-illite transformation. The K/Ar clock of the diagenetically formed illite la ers is set to zero age at the time of diagenesis (although that of existing illite layers within the crystals remains unaffected), and it is therefore possible to estimate the mean time of diagenesis in such shale sequences. Illite is a common cement in sandstones. The time of cementation by illite can be estimated from K/Ar systematics in cases, such as that of the Permian Rotliegendes of the North Sea, where the clay-sized fraction of the original detritus was relatively free of illite or other K-bearing phases. Conditions of cementation can be inferred from oxygen isotope measurements, augmented by knowledge of the geologic/tectonic history of the sandstone. In the case of the Rotliegendes, the timing and conditions of illite cementation were relatively uniform within fault blocks but varied from block to block. Oxygen isotope measurements indicate that meteoric water components were important in illite formation at times when nearby sections of the Rotliegendes were exposed to the surface by uplift an erosion. End_of_Article - Last_Page 304------------

Environmental isotope investigations of New Zealand geothermal systems—A review

Environmental isotope investigations of geothermal systems at the New Zealand Institute of Nuclear Sciences have concentrated in recent years on combining several isotopes with chemical analyses. Geothermal hydrology has been studied by the use of hydrogen and oxygen isotopes with chloride and other water analyses. Rocks and minerals in well cores have added information to the geology and chemistry through the use of oxygen isotope techniques. Oxygen, hydrogen, carbon and sulphur isotope geothermometry have been combined in an attempt to derive temperature profiles with depth. 222Rn measurements in soil indicate leakage through faults, while 222Rn measurement of well discharges show evidence of underground processes. Future work will include noble gas isotope measurements. Measurements of 1H and 14C are reported in an associated paper on tracing of underground water movements.

The Radiation-Induced Exchange Reaction of Oxygen Atoms in Carbon Dioxide

Abstract Oxygen exchange of carbon dioxide induced by β-ray irradiation has been investigated by use of oxygen isotope O*. From the decrease of O* amount, the apparent and total values of the exchange reaction, Gcorr(-CO2*) and Gtotalexc, have been calculated to be 1.72 and 51, respectively. The latter value 51 would be equivalent to the forward reaction, but has been shown to be larger than the corresponding value (8.5) in Harteck’s experiment.