A novel application of triple oxygen isotope ratios of speleothems

Lijuan Sha, Sasadhar Mahata, Pengzhen Duan, Boaz Luz, Pu Zhang, Jonathan Baker, Baoyun Zong, Youfeng Ning, Yassine Ait Brahim, Haiwei Zhang, R. Lawrence Edwards, Hai Cheng

Research output: Contribution to journalArticle

Abstract

We present triple oxygen isotope data from speleothems obtained by an O2-CO2 Pt-catalyzed oxygen-isotope equilibration method. The high precision (9 per meg or better, 1σ SD) of our new speleothem Δ17O (carbonate 17O anomaly) data is sufficient to resolve subtle hydroclimatic signals. In addition, we determined triple oxygen isotope fractionation factors through two sets of modern paired carbonate-dripwater samples collected at a temperature of 17 ± 1 °C, which is prerequisite to the calculation of triple oxygen isotope compositions of parent meteoric waters at cave sites from speleothem proxy data. Based on this calibration, we back calculated triple oxygen isotope compositions of parent waters across well-characterized climate transitions using speleothem proxy data from three regions. Resulting oxygen-isotope data closely track the Global Meteoric Water Line (GMWL), providing a preliminary validation of the method. Our speleothem Δ17O data indicate a 21 per meg difference between Marine Isotope Stage 5d and 5e in samples from Central Asia and a 15 per meg difference between the Middle Holocene and Last Glacial Maximum in samples from the eastern Mediterranean, suggesting a shift in moisture source and/or fractionation history. Unexpectedly, there were no measurable Δ17O differences between glacial and interglacial samples from both the South American (western Amazon) and Asian (southern China) monsoon domains, implying consistent moisture-source conditions across glacial and interglacial cycles, at least in terms of relative humidity. Remarkably, Δ17O values from the western Amazonian samples are significantly higher (∼20 per meg) than those from Asian monsoon regions, suggesting lower relative humidity along moisture trajectories in the western Amazon during the Middle Holocene and Last Glacial period. Similarly, Δ17O values of the eastern Mediterranean samples are significantly higher (19–55 per meg) than those of coeval samples from Central Asia, implying different hydrological environments or moisture sources despite being in the same westerly circulation domain. Speleothem Δ17O data may thus provide new and important constraints for understanding regional and global hydroclimate dynamics.

Original languageEnglish (US)
Pages (from-to)360-378
Number of pages19
JournalGeochimica et Cosmochimica Acta
Volume270
DOIs
StatePublished - Feb 1 2020

Fingerprint

Oxygen Isotopes
oxygen isotope ratio
speleothem
oxygen isotope
Moisture
moisture
Carbonates
Fractionation
meteoric water
Atmospheric humidity
interglacial
relative humidity
monsoon
Water piping systems
fractionation
Caves
Holocene
Water
carbonate
Chemical analysis

Keywords

  • Dripwater
  • Moisture source
  • Paleohydroclimate
  • Relative humidity
  • Speleothems
  • Triple oxygen isotope

Cite this

A novel application of triple oxygen isotope ratios of speleothems. / Sha, Lijuan; Mahata, Sasadhar; Duan, Pengzhen; Luz, Boaz; Zhang, Pu; Baker, Jonathan; Zong, Baoyun; Ning, Youfeng; Brahim, Yassine Ait; Zhang, Haiwei; Edwards, R. Lawrence; Cheng, Hai.

In: Geochimica et Cosmochimica Acta, Vol. 270, 01.02.2020, p. 360-378.

Research output: Contribution to journalArticle

Sha, L, Mahata, S, Duan, P, Luz, B, Zhang, P, Baker, J, Zong, B, Ning, Y, Brahim, YA, Zhang, H, Edwards, RL & Cheng, H 2020, 'A novel application of triple oxygen isotope ratios of speleothems', Geochimica et Cosmochimica Acta, vol. 270, pp. 360-378. https://doi.org/10.1016/j.gca.2019.12.003
Sha, Lijuan ; Mahata, Sasadhar ; Duan, Pengzhen ; Luz, Boaz ; Zhang, Pu ; Baker, Jonathan ; Zong, Baoyun ; Ning, Youfeng ; Brahim, Yassine Ait ; Zhang, Haiwei ; Edwards, R. Lawrence ; Cheng, Hai. / A novel application of triple oxygen isotope ratios of speleothems. In: Geochimica et Cosmochimica Acta. 2020 ; Vol. 270. pp. 360-378.
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AU - Duan, Pengzhen

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AU - Zhang, Pu

AU - Baker, Jonathan

AU - Zong, Baoyun

AU - Ning, Youfeng

AU - Brahim, Yassine Ait

AU - Zhang, Haiwei

AU - Edwards, R. Lawrence

AU - Cheng, Hai

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N2 - We present triple oxygen isotope data from speleothems obtained by an O2-CO2 Pt-catalyzed oxygen-isotope equilibration method. The high precision (9 per meg or better, 1σ SD) of our new speleothem Δ17O (carbonate 17O anomaly) data is sufficient to resolve subtle hydroclimatic signals. In addition, we determined triple oxygen isotope fractionation factors through two sets of modern paired carbonate-dripwater samples collected at a temperature of 17 ± 1 °C, which is prerequisite to the calculation of triple oxygen isotope compositions of parent meteoric waters at cave sites from speleothem proxy data. Based on this calibration, we back calculated triple oxygen isotope compositions of parent waters across well-characterized climate transitions using speleothem proxy data from three regions. Resulting oxygen-isotope data closely track the Global Meteoric Water Line (GMWL), providing a preliminary validation of the method. Our speleothem Δ17O data indicate a 21 per meg difference between Marine Isotope Stage 5d and 5e in samples from Central Asia and a 15 per meg difference between the Middle Holocene and Last Glacial Maximum in samples from the eastern Mediterranean, suggesting a shift in moisture source and/or fractionation history. Unexpectedly, there were no measurable Δ17O differences between glacial and interglacial samples from both the South American (western Amazon) and Asian (southern China) monsoon domains, implying consistent moisture-source conditions across glacial and interglacial cycles, at least in terms of relative humidity. Remarkably, Δ17O values from the western Amazonian samples are significantly higher (∼20 per meg) than those from Asian monsoon regions, suggesting lower relative humidity along moisture trajectories in the western Amazon during the Middle Holocene and Last Glacial period. Similarly, Δ17O values of the eastern Mediterranean samples are significantly higher (19–55 per meg) than those of coeval samples from Central Asia, implying different hydrological environments or moisture sources despite being in the same westerly circulation domain. Speleothem Δ17O data may thus provide new and important constraints for understanding regional and global hydroclimate dynamics.

AB - We present triple oxygen isotope data from speleothems obtained by an O2-CO2 Pt-catalyzed oxygen-isotope equilibration method. The high precision (9 per meg or better, 1σ SD) of our new speleothem Δ17O (carbonate 17O anomaly) data is sufficient to resolve subtle hydroclimatic signals. In addition, we determined triple oxygen isotope fractionation factors through two sets of modern paired carbonate-dripwater samples collected at a temperature of 17 ± 1 °C, which is prerequisite to the calculation of triple oxygen isotope compositions of parent meteoric waters at cave sites from speleothem proxy data. Based on this calibration, we back calculated triple oxygen isotope compositions of parent waters across well-characterized climate transitions using speleothem proxy data from three regions. Resulting oxygen-isotope data closely track the Global Meteoric Water Line (GMWL), providing a preliminary validation of the method. Our speleothem Δ17O data indicate a 21 per meg difference between Marine Isotope Stage 5d and 5e in samples from Central Asia and a 15 per meg difference between the Middle Holocene and Last Glacial Maximum in samples from the eastern Mediterranean, suggesting a shift in moisture source and/or fractionation history. Unexpectedly, there were no measurable Δ17O differences between glacial and interglacial samples from both the South American (western Amazon) and Asian (southern China) monsoon domains, implying consistent moisture-source conditions across glacial and interglacial cycles, at least in terms of relative humidity. Remarkably, Δ17O values from the western Amazonian samples are significantly higher (∼20 per meg) than those from Asian monsoon regions, suggesting lower relative humidity along moisture trajectories in the western Amazon during the Middle Holocene and Last Glacial period. Similarly, Δ17O values of the eastern Mediterranean samples are significantly higher (19–55 per meg) than those of coeval samples from Central Asia, implying different hydrological environments or moisture sources despite being in the same westerly circulation domain. Speleothem Δ17O data may thus provide new and important constraints for understanding regional and global hydroclimate dynamics.

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