40Ar/39Ar age of the Lake Saint Martin impact structure (Canada) - Unchaining the Late Triassic terrestrial impact craters

Martin Schmieder, F. Jourdan, Eric Tohver, E.A. Cloutis

    Research output: Contribution to journalArticle

    18 Citations (Scopus)

    Abstract

    © 2014 Elsevier B.V. New 40Ar/39Ar dating of impact-melted K-feldspars and impact melt rock from the ~40 km Lake Saint Martin impact structure in Manitoba, Canada, yielded three plateau ages and one mini-plateau age in agreement with inverse isochron ages for the K-feldspar melt aliquots and a minimum age for a whole-rock impact melt sample. A combination of two plateau ages and one isochron age, with a weighted mean of 227.8±0.9 Ma [±1.1 Ma; including all sources of uncertainty] (2σ MSWD = 0.52; P=0.59), is considered to represent the best-estimate age for the impact. The concordant 40Ar/39Ar ages for the melted K-feldspars, derived from impact melt rocks in the eastern crater moat domain and the partially melted Proterozoic central uplift granite, suggest that the new dates accurately reflect the Lake Saint Martin impact event in the Carnian stage of the Late Triassic. With a relative error of ±0.4% on the 40Ar/39Ar age, the Lake Saint Martin impact structure counts among the most precisely dated impact structures on Earth. The new isotopic age for Lake Saint Martin significantly improves upon earlier Rb/Sr and (U-Th)/He results for this impact structure and contradicts the hypothesis that planet Earth experienced the formation of a giant 'impact crater chain' during a major Late Triassic multiple impact event.
    Original languageEnglish
    Pages (from-to)37-48
    Number of pages12
    JournalEarth and Planetary Science Letters
    Volume406
    Early online date27 Sep 2014
    DOIs
    Publication statusPublished - 15 Nov 2014

    Fingerprint Dive into the research topics of '40Ar/39Ar age of the Lake Saint Martin impact structure (Canada) - Unchaining the Late Triassic terrestrial impact craters'. Together they form a unique fingerprint.

    Cite this