Mineralogic Evidence for an Impact Event at the Cretaceous-Tertiary Boundary

  title={Mineralogic Evidence for an Impact Event at the Cretaceous-Tertiary Boundary},
  author={B. F. Bohor and E. Foord and P. J. Modreski and D. Triplehorn},
  pages={867 - 869}
  • B. F. Bohor, E. Foord, +1 author D. Triplehorn
  • Published 1984
  • Geology, Medicine
  • Science
  • A thin claystone layer found in nonmarine rocks at the palynological Cretaceous-Tertiary boundary in eastern Montana contains an anomalously high value of iridium. The nonclay fraction is mostly quartz with minor feldspar, and some of these grains display planar features. These planar features are related to specific crystallographic directions in the quartz lattice. The shocked quartz grains also exhibit asterism and have lowered refractive indices. All these mineralogical features are… CONTINUE READING
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    Bohor, paper presented at the 20th Annual Meeting of the Clay
    • Minerals Society,
    • 1983
    ] makes a case for concentration of iridium in marine clays at the K-T ues for iridium of 5
    • Geol. Soc. Am. Spec. Pap
    • 1982
    Gratz for their helpful comments; and C. Sanderson for laboratory assistance