Reconstructing paleoelevation in eroded oregons

Andreas Mulch, Christian Teyssier, Michael A. Cosca, Olivier Vanderhaeghe, Torsten W. Vennemann

Research output: Contribution to journalArticlepeer-review

98 Scopus citations

Abstract

Hydrogen isotope and 40Ar/39Ar geochronological data are presented from muscovite within a crustal-scale extensional detachment of the Shuswap Metamorphic Complex, North American Cordillera. The hydrogen isotope compositions (δDms) of precisely dated muscovite attain values as low as -156‰ in the detachment mylonite, whereas footwall quartzite has a δDms value of -81‰. The very low δDms values in the detachment are best explained by infiltration of meteoric water, with maximum δD values of -135‰ ± 3‰, during extensional unroofing of the orogen at 49.0-47.9 Ma. On the basis of the empirically determined relationship between elevation and isotopic composition of precipitation, the reconstructed early Eocene paleoelevations of the orogen are 4060 ± 250 m to 4320 ± 250 m, at least 1000 m higher than the highest present-day peaks. We propose that the isotopic composition of surface-derived waters in extensional detachments represents a newly recognized method to estimate maximum paleoelevations attained immediately preceding extensional orogenic collapse.

Original languageEnglish (US)
Pages (from-to)525-528
Number of pages4
JournalGeology
Volume32
Issue number6
DOIs
StatePublished - Jun 2004

Keywords

  • Detachment
  • Eocene
  • Hydrogen
  • Isotope
  • Paleoelevation

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