Diachroneity of the Clearwater West and Clearwater East impact structures indicated by the (U–Th)/He dating method

M. B. Biren, Matthijs Van Soest, J. A. Wartho, Kip Hodges, J. G. Spray

Research output: Contribution to journalArticle

6 Scopus citations


The (U–Th)/He method has been applied to constrain the formation ages of the Clearwater West and East impact structures of Quebec, Canada. Zircons were separated from impact melt samples derived from a surface exposure at Clearwater West (32 km diameter), and from a drill core at Clearwater East (26 km diameter). The (U–Th)/He results indicate ages of 280±27 Ma (2σ, n=7) for Clearwater West, and 450±56 Ma (2σ, n=8) for Clearwater East. Our (U–Th)/He date for Clearwater West supports the findings of previous Rb–Sr (266±15 Ma; 2σ) and 40Ar/39Ar (280±4 Ma and 283.8±2.2 Ma, 2σ) impact melt studies. Our (U–Th)/He date for Clearwater East also overlaps with previously published 40Ar/39Ar dating results, which yielded U-shaped spectra, with ‘maximum’ and ‘best-estimate’ dates of ∼ 460–470 Ma. Our results support the contention, previously based solely on 40Ar/39Ar data, that the Clearwater West and East impact structures do not comprise an impact doublet that formed coevally from a binary asteroid pair.

Original languageEnglish (US)
Pages (from-to)56-66
Number of pages11
JournalEarth and Planetary Science Letters
StatePublished - Nov 1 2016



  • helium diffusion
  • impact cratering
  • shock metamorphism
  • thermochronology

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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