Mathematics – Logic
Scientific paper
Jul 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994pasp..106..689v&link_type=abstract
Astronomical Society of the Pacific, Publications (ISSN 0004-6280), vol. 106, no. 701, p. 689-695
Mathematics
Logic
10
Asteroids, Catastrophe Theory, Comets, Cretaceous-Tertiary Boundary, Extinction, Planetary Craters, Abundance, Ejecta, Fossils, Geochronology, Iridium Isotopes, Supernovae
Scientific paper
The boundary between the Cretaceous and Tertiary epochs has now been firmly linked to a large impact structure centered on Chicxulub in Yucatan. This crater has an age of 65.0 +/- 0.1 million years. Macrofossils such as ammonites, and footprints of dinosaurs, are found up to centimeters below (but not above] the Creataceous-Tertiary (K/T) boundary. t is not yet certain whether the Chicxulub crater was produced by a comet or by an asteroid. However, data on the crater diameter and K/T iridium abundance slightly favor a cometary origin. The cause(s) of the other major extinctions in the geological record, such as those between the Permian and Triassic (P/TR) and between the Triassic and Jurassic (TR/J) remain in doubt. Explosions of nearby supernovae occur too rarely to account for the frequency of major extinctions in the approximately 600 million year geological record of the Phanerozoic.
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