10 Trace and Indirect Evidence of Terrestrial Bolide Impacts

Monday, 7 May 2007
2:00 PM - 4:10 PM

IN SITU MICROSPHERULES PRESENT WITHIN A MICROBRECCIA NEAR THE BASE OF THE BLACK DRAGON MEMBER OF THE TRIASSIC MOENKOPI FORMATION, SAN RAFAEL SWELL, UTAH

Paper number: 10-4
Program: SYMPOSIA SESSIONS
Time: 2:45 PM – 3:05 PM

Authors

Abstract

Metallic microspherules ranging in size from 5 micrometers to 20 micrometers are present in situ in a microbreccia near the base of the Black Dragon member of the Moenkopi formation. These particles are spherical and consist primarily of iron with trace amounts of titanium, manganese, calcium, aluminum and silicon. Many of these microspherules exhibit precursor magnetite (?) crystallization.

A scanning electron microscope with energy dispersive spectrometry was employed to determine the qualitative chemistry and morphology of these particles. A Leica DMLP light microscope with a CLEMEX software program was used to map and photomicrograph these particles in situ.

These microspherules appear similar to those reportedly discovered at the 1908 Tunguska event site in Russia. It is therefore suggested that these particles may be products resulting from aerial vaporization of a bolide near the Permotriassic boundary.