<?xml version='1.0' encoding='utf-8'?>
<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:contributor>G. A. Izett</dc:contributor>
  <dc:contributor>R. A. Haugerud</dc:contributor>
  <dc:contributor>J. F. Sutter</dc:contributor>
  <dc:creator>Michael J. Kunk</dc:creator>
  <dc:date>1989</dc:date>
  <dc:description>&lt;p&gt;&lt;span&gt;The mineralogy of shocked mineral and lithic grains in the Cretaceous-Tertiary (K-T) boundary claystone worldwide is most consistent with a bolide impact on a continent. Both the concentrations and sizes of these shocked grains are greatest in the western interior of North America. These data suggest that the Manson impact structure in north-central Iowa is a viable candidate for the K-T boundary impact event. Argon-40–argon-39 age spectrum dating of shocked microcline from the crystalline central uplift of the Manson impact structure indicates that there was severe argon-40 loss at 65.7 ± 1.0 million years ago, an age that is indistinguishable from that of the K-T boundary, within the limits of analytical precision.&lt;/span&gt;&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1126/science.244.4912.1565</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>American Association for the Advancement of Science</dc:publisher>
  <dc:title>40Ar-39Ar dating of the Manson impact structure: A Cretaceous-Tertiary boundary crater candidate</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>