<?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. B. Dalrymple</dc:contributor>
  <dc:contributor>L.E. Marin</dc:contributor>
  <dc:contributor>G. Ryder</dc:contributor>
  <dc:contributor>B.C. Schuraytz</dc:contributor>
  <dc:contributor>J. Urrutia-Fucugauchi</dc:contributor>
  <dc:creator>Virgil L. Sharpton</dc:creator>
  <dc:date>1992</dc:date>
  <dc:description>&lt;p&gt;&lt;span&gt;The 200-km-diameter Chicxulub structure&lt;/span&gt;&lt;sup&gt;1–3&lt;/sup&gt;&lt;span&gt;&amp;nbsp;in northern Yucatan, Mexico has emerged as the prime candidate for the Cretaceous/Tertiary (K/T) boundary impact crater&lt;/span&gt;&lt;sup&gt;3–6&lt;/sup&gt;&lt;span&gt;. Concentric geophysical anomalies associated with enigmatic occurrences of Upper Cretaceous breccias and andesitic rocks led Penfield and Camargo&lt;/span&gt;&lt;sup&gt;1&lt;/sup&gt;&lt;span&gt;&amp;nbsp;to suspect that this structure was a buried impact basin. More recently, the discovery of shocked quartz grains in a Chicxulub breccia&lt;/span&gt;&lt;sup&gt;3&lt;/sup&gt;&lt;span&gt;, and chemical similarities between Chicxulub rocks and K/T tektite-like glasses&lt;/span&gt;&lt;sup&gt;3–6&lt;/sup&gt;&lt;span&gt;&amp;nbsp;have been advanced as evidence that the Chicxulub structure is a K/T impact site. Here we present evidence from core samples that Chicxulub is indeed a K/T source crater, and can apparently account for all the evidence of impact distributed globally at the K/T boundary without the need for simultaneous multiple impacts or comet showers. Shocked breccia clasts found in the cores are similar to shocked lithic fragments found worldwide in the K/T boundary ejecta layer&lt;/span&gt;&lt;sup&gt;7,8&lt;/sup&gt;&lt;span&gt;. The Chicxulub melt rocks that we studied contain anomalously high levels of iridium (up to 13.5 parts per 10&lt;/span&gt;&lt;sup&gt;9&lt;/sup&gt;&lt;span&gt;), also consistent with the iridium-enriched K/T boundary layer&lt;/span&gt;&lt;sup&gt;9&lt;/sup&gt;&lt;span&gt;. Our best estimate of the crystallization age of these melt rocks, as determined by&amp;nbsp;&lt;/span&gt;&lt;sup&gt;40&lt;/sup&gt;&lt;span&gt;Ar/&amp;lt;&lt;/span&gt;&lt;sup&gt;39&lt;/sup&gt;&lt;span&gt;Ar analyses, is 65.2 ±0.4 (1σ) Myr, in good agreement with the mean plateau age of 64.98 ± 0.05 Myr recently reported&lt;/span&gt;&lt;sup&gt;10&lt;/sup&gt;&lt;span&gt;. Furthermore, these melt rocks acquired a remanent magnetization indicating that they cooled during an episode of reversed geomagnetic polarity. The only such episode consistent with&lt;/span&gt;&lt;sup&gt;40&lt;/sup&gt;&lt;span&gt;Ar/&amp;lt;&lt;/span&gt;&lt;sup&gt;39&lt;/sup&gt;&lt;span&gt;Ar constraints is chron 29R, which includes the K/T boundary.&lt;/span&gt;&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1038/359819a0</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>Springer Nature</dc:publisher>
  <dc:title>New links between the Chicxulub impact structure and the Cretaceous/Tertiary boundary</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>