The oxygen isotope stratigraphic record of the Late Pleistocene

Oxygen isotope measurements have been made in foraminifera from over 60 deep-sea sediment cores. Taken together with the oxygen isotope measurements published by Emiliani from Caribbean and Equatorial Atlantic cores, this comprises a unique body of stratigraphic data covering most of the important areas of calcareous sediment over the whole world ocean. The oxygen isotopic composition of foraminifera from cores of Late Pleistocene sediment varies in a similar manner in nearly all areas; the variations reflect changes in the oxygen isotopic composition of the ocean. The oceans are mixed in about 1 ka so that ocean isotopic changes, resulting from fluctuations in the quantity of ice stored on the continents, must have occurred almost synchronously in all regions. Thus the oxygen isotope record provides an excellent means of stratigraphic correlation. Cores accumulated at rates of over about 5 cm/ka provide records of oxygen isotopic composition change that are almost unaffected by post-depositional mixing of the sediment. Thus they preserve a detailed record of the advance and retreat of the ice masses in the northern hemisphere, and provide a unique source of information for the study of ice-sheet dynamics.

Download Full-text

Oxygen isotopic composition of fissure-grown quartz, adularia, and calcite from Broadlands geothermal field, New Zealand, with an appendix on quartz-K-feldspar-calcite-muscovite oxygen isotope geothermometers

American Journal of Science ◽

10.2475/ajs.275.7.785 ◽

1975 ◽

Vol 275 (7) ◽

pp. 785-800 ◽

Cited By ~ 34

Author(s):

P. Blattner

Keyword(s):

New Zealand ◽

Isotopic Composition ◽

Oxygen Isotope ◽

Geothermal Field ◽

Oxygen Isotopic Composition ◽

Oxygen Isotopic

Download Full-text

Revealing the climate of snowball Earth from Δ17O systematics of hydrothermal rocks

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1422887112 ◽

2015 ◽

Vol 112 (17) ◽

pp. 5337-5341 ◽

Cited By ~ 34

Author(s):

Daniel Herwartz ◽

Andreas Pack ◽

Dmitri Krylov ◽

Yilin Xiao ◽

Karlis Muehlenbachs ◽

...

Keyword(s):

Isotopic Composition ◽

Oxygen Isotope ◽

Water Samples ◽

Isotope Composition ◽

Oxygen Isotopic Composition ◽

Snowball Earth ◽

Climate Conditions ◽

Oxygen Isotopic ◽

Mass Dependent ◽

Insight Into

The oxygen isotopic composition of hydrothermally altered rocks partly originates from the interacting fluid. We use the triple oxygen isotope composition (17O/16O, 18O/16O) of Proterozoic rocks to reconstruct the 18O/16O ratio of ancient meteoric waters. Some of these waters have originated from snowball Earth glaciers and thus give insight into the climate and hydrology of these critical intervals in Earth history. For a Paleoproterozoic [∼2.3–2.4 gigayears ago (Ga)] snowball Earth, δ18O = −43 ± 3‰ is estimated for pristine meteoric waters that precipitated at low paleo-latitudes (≤35°N). Today, such low 18O/16O values are only observed in central Antarctica, where long distillation trajectories in combination with low condensation temperatures promote extreme 18O depletion. For a Neoproterozoic (∼0.6–0.7 Ga) snowball Earth, higher meltwater δ18O estimates of −21 ± 3‰ imply less extreme climate conditions at similar paleo-latitudes (≤35°N). Both estimates are single snapshots of ancient water samples and may not represent peak snowball Earth conditions. We demonstrate how 17O/16O measurements provide information beyond traditional 18O/16O measurements, even though all fractionation processes are purely mass dependent.

Download Full-text

Climate, water and CO2: a geological perspective

Mineralogical Magazine ◽

10.1180/minmag.2008.072.1.293 ◽

2008 ◽

Vol 72 (1) ◽

pp. 293-294

Author(s):

J. Veizer

Keyword(s):

Stable Isotope ◽

Isotopic Composition ◽

Oxygen Isotope ◽

Isotope Geochemistry ◽

Oxygen Isotopic Composition ◽

Stable Isotope Geochemistry ◽

Temperature Signal ◽

Oxygen Isotopic ◽

Time Periods

The development of a palaeothermometer for ancient oceans has been a prime goal of stable isotope geochemistry since its inception in the middle of the last century. Following the calibration of the calcite oxygen isotope palaeothermometer by Epstein et al. (1953), and expanding on the seminal papers by Cesare Emiliani, the technique blossomed into a widely applied tool of palaeoceanography. These studies resulted in major advances in our understanding of Quaternary, and to some extent Tertiary oceans, but for older time periods the effort is mired by controversy and is at a standstill. In part this is due to the dearth of well-characterized carrier phases for the temperature signal, such as foraminifera shells, in the pre-Tertiary strata, but an intractable disagreement among practitioners as to the oxygen isotopic composition of ancient seawater is probably a more important stumbling block.

Download Full-text

Changes of Ionic and Oxygen Isotopic Composition of the Snowpack at the Glacier Austre Okstindbreen, Norway, 1995

Hydrology Research ◽

10.2166/nh.1998.0001 ◽

1998 ◽

Vol 29 (1) ◽

pp. 1-20 ◽

Cited By ~ 20

Author(s):

Peter Raben ◽

Wilfred H. Theakstone

Keyword(s):

Isotopic Composition ◽

Sea Level ◽

Oxygen Isotopes ◽

Oxygen Isotopic Composition ◽

Isotopic Ratios ◽

Vertical Variations ◽

Oxygen Isotopic ◽

The Difference ◽

Liquid Precipitation ◽

Different Altitudes

Marked vertical variations of ions and oxygen isotopes were present in the snowpack at the glacier Austre Okstindbreen during the pre-melting phase in 1995 at sites between 825 m and 1,470 m above sea level. As the first meltwater percolated from the top of the pack, ions were moved to a greater depth, but the isotopic composition remained relatively unchanged. Ions continued to move downwards through the pack during the melting phase, even when there was little surface melting and no addition of liquid precipitation. The at-a-depth correlation between ionic concentrations and isotopic ratios, strong in the pre-melting phase, weakened during melting. In August, concentrations of Na+ and Mg2+ ions in the residual pack were low and vertical variations were slight; 18O enrichment had occurred. The difference of the time at which melting of the snowpack starts at different altitudes influences the input of ions and isotopes to the underlying glacier.

Download Full-text

δ2Hn-alkane and δ18Osugar biomarker proxies from leaves and topsoils of the Bale Mountains, Ethiopia, and implications for paleoclimate reconstructions

Biogeochemistry ◽

10.1007/s10533-021-00773-z ◽

2021 ◽

Author(s):

Bruk Lemma ◽

Lucas Bittner ◽

Bruno Glaser ◽

Seifu Kebede ◽

Sileshi Nemomissa ◽

...

Keyword(s):

Isotopic Composition ◽

Leaf Growth ◽

Thermal Conversion ◽

Oxygen Isotopic Composition ◽

Leaf Water ◽

Isotope Ratio Mass Spectrometer ◽

Oxygen Isotopic ◽

Calibration Study ◽

Microclimatic Conditions ◽

Paleoclimate Reconstructions

AbstractThe hydrogen isotopic composition of leaf wax–derived n-alkane (δ2Hn-alkane) and oxygen isotopic composition of hemicellulose–derived sugar (δ18Osugar) biomarkers are valuable proxies for paleoclimate reconstructions. Here, we present a calibration study along the Bale Mountains in Ethiopia to evaluate how accurately and precisely the isotopic composition of precipitation is imprinted in these biomarkers. n-Alkanes and sugars were extracted from the leaf and topsoil samples and compound–specific δ2Hn-alkane and δ18Osugar values were measured using a gas chromatograph–thermal conversion–isotope ratio mass spectrometer (GC–TC–IRMS). The weighted mean δ2Hn-alkane and δ18Osugar values range from − 186 to − 89‰ and from + 27 to + 46‰, respectively. Degradation and root inputs did not appear to alter the isotopic composition of the biomarkers in the soil samples analyzed. Yet, the δ2Hn-alkane values show a statistically significant species dependence and δ18Osugar yielded the same species–dependent trends. The reconstructed leaf water of Erica arborea and Erica trimera is 2H– and 18O–enriched by + 55 ± 5 and + 9 ± 1‰, respectively, compared to precipitation. By contrast, Festuca abyssinica reveals the most negative δ2Hn-alkane and least positive δ18Osugar values. This can be attributed to “signal–dampening” caused by basal grass leaf growth. The intermediate values for Alchemilla haumannii and Helichrysum splendidum can be likely explained with plant physiological differences or microclimatic conditions affecting relative humidity (RH) and thus RH–dependent leaf water isotope enrichment. While the actual RH values range from 69 to 82% (x̄ = 80 ± 3.4%), the reconstructed RH values based on a recently suggested coupled δ2Hn-alkane –δ18Osugar (paleo–) hygrometer approach yielded a mean of 78 ± 21%. Our findings corroborate (i) that vegetation changes, particularly in terms of grass versus non–grassy vegetation, need to be considered in paleoclimate studies based on δ2Hn-alkane and δ18Osugar records and (ii) that the coupled δ2Hn-alkane –δ18Osugar (paleo–) hygrometer approach holds great potential for deriving additional paleoclimatic information compared to single isotope approaches.

Download Full-text