The age of the Kara impact structure, Russia

Authors

  • MARIO TRIELOFF,

    Corresponding author
    1. Max-Planck-Institut für Kernphysik, P.O. Box 103980, D-69029 Heidelberg, Germany
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  • ALEXANDER DEUTSCH,

    1. Institut für Planetologie, Universität Münster, Wilhelm-Klemm-Str. 10, D-48149 Münster, Germany
    2. Zentrallabor für Geochronologie, Universität Münster, Corrensstr. 24, D-48149 Münster, Germany
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  • ELMAR K. JESSBERGER

    1. Max-Planck-Institut für Kernphysik, P.O. Box 103980, D-69029 Heidelberg, Germany
    2. Institut für Planetologie, Universität Münster, Wilhelm-Klemm-Str. 10, D-48149 Münster, Germany
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trieloff@kosmo.mpi-hd.mpg.de

Abstract

Abstract— For the ∼65 km sized Kara impact structure close to the polar Ural, we report an age of 70.3 ± 2.2 Ma (2s̀), defined by the mean of 40Ar-39Ar plateau ages for three glassy or crystalline impact melt rocks cleaned from mineral and rock clasts. The fine structure of the age spectra of these samples can quantitatively be simulated by modeling taking into account 39Ar recoil effects, without assuming the presence of excess Ar. The calculations corroborate our age results by showing that 39Ar recoil does not affect the plateau fractions. Previously, Kara has been proposed as a probable K/T impact site or was related to the Campanian-Maastrichtian boundary at 73 Ma. At the 2s̀ level, both suggestions are ruled out by the well-constrained age for the Kara impact structure.

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