Stable isotope variations (δ18O and δD) in modern waters across the Andean Plateau

John Bershaw, Joel E Saylor, Carmala N. Garzione, Andrew Leier, Kurt E. Sundell

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Environmental parameters that influence the isotopic composition of meteoric water (δ18O and δD) are well characterized up the windward side of mountains, where orographic precipitation results in a predictable relationship between the isotopic composition of precipitation and elevation. The topographic and climatic evolution of the Andean Plateau and surrounding regions has been studied extensively by exploiting this relationship through the use of paleowater proxies. However, interpretation on the plateau itself is challenged by a poor understanding of processes that fractionate isotopes during vapor transport and rainout, and by the relative contribution of unique moisture sources. Here, we present an extensive dataset of modern surface water samples for the northern Andean Plateau and surrounding regions to elucidate patterns and causes of isotope fractionation in this continental environment. These data show a progressive increase in δ18O of stream water west of the Eastern Cordillera (∼1‰/70 km), almost identical to the rate observed across the Tibetan Plateau, attributed to a larger fraction of recycled water in precipitation and/or increased evaporative enrichment downwind. This may lead to underestimates of paleoelevation, particularly for sites deep into the rainshadow of the Eastern Cordilleran crest. That said, elevation is a primary control on the isotopic composition of surface waters across the entire Andean Plateau and its flanks when considering the most negative δ18O values, highlighting the need for sufficiently large datasets to distinguish minimally evaporated samples. There is a general increase in δ18O on the plateau from north to south, concomitant with an increase in aridity and decrease in convective moistening (amount effect). Lastly, stable isotope and seasonal precipitation patterns suggest easterlies provide the vast majority of moisture that falls as precipitation across the Andean Plateau and Western Cordillera, from Peru to northern Bolivia (−13° to −20° latitude), with Pacific-derived moisture contributing a minor amount at low elevations near the coast.

Original languageEnglish (US)
Pages (from-to)310-324
Number of pages15
JournalGeochimica et Cosmochimica Acta
Volume194
DOIs
StatePublished - Dec 1 2016
Externally publishedYes

Fingerprint

Isotopes
stable isotope
Moisture
plateau
Surface waters
Water
Chemical analysis
Fractionation
isotopic composition
water
moisture
Coastal zones
Wetting
cordillera
Vapors
isotope
surface water
aridity
meteoric water
fractionation

Keywords

  • Altiplano
  • Andes
  • Climate
  • Meteoric water
  • Paleoaltimetry
  • South America
  • Stable isotope geochemistry

ASJC Scopus subject areas

  • Geochemistry and Petrology

Cite this

Stable isotope variations (δ18O and δD) in modern waters across the Andean Plateau. / Bershaw, John; Saylor, Joel E; Garzione, Carmala N.; Leier, Andrew; Sundell, Kurt E.

In: Geochimica et Cosmochimica Acta, Vol. 194, 01.12.2016, p. 310-324.

Research output: Contribution to journalArticle

Bershaw, John ; Saylor, Joel E ; Garzione, Carmala N. ; Leier, Andrew ; Sundell, Kurt E. / Stable isotope variations (δ18O and δD) in modern waters across the Andean Plateau. In: Geochimica et Cosmochimica Acta. 2016 ; Vol. 194. pp. 310-324.
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