Seasonale stable isotope evidence for a strong Asian monsoon throughout the past 10.7 m.y

D. L. Dettman, M. J. Kohn, J. Quade, F. J. Ryerson, T. P. Ojha, S. Hamidullah

Research output: Contribution to journalArticlepeer-review

94 Scopus citations

Abstract

Stable isotope profiles of fossil freshwater bivalve shells and mammal teeth provide a record of the seasonal δ 18 O variation in surface waters of the Himalayan foreland over the past 11 m.y. Between 3.1 and 10.7 Ma the δ 18 O of surface waters approached or exceeded 0‰ standard mean ocean water (SMOW) in the dry season. Since 9.5 Ma the magnitude of seasonal variability in δ 18 O has remained essentially unchanged. Both observations imply that the Tibetan Plateau had attained sufficient elevation and area prior to 10.7 Ma to support a strong Asian monsoon. These data also imply that the δ 18 O of wet-season rainfall was significantly more negative (-9.5‰ SMOW) prior to 7.5 Ma than after (-6.5‰ SMOW). If this change is attributable to a lessening of the amount effect in rainfall, this agrees with floral and soil geochemical data that indicate increasing aridity beginning at 7.5 Ma.

Original languageEnglish (US)
Pages (from-to)31-34
Number of pages4
JournalGeology
Volume29
Issue number1
DOIs
StatePublished - Jan 2001

Keywords

  • Monsoon
  • Paleohydrology
  • Seasonality
  • Stable isotope
  • Tibetan Plateau

ASJC Scopus subject areas

  • Geology

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