1 Tectonics, Geophysics, Structural Geology and Bolide Impacts

Monday, 23 May 2005
8:00 AM - 12:00 PM

THE BLACK DRAGON BRECCIA AND THE LONG CANYON MEGABRECCIA, SOUTHEASTERN UTAH: A SHARED PROVENANCE?

Paper number: 1-13
Program: GENERAL SESSIONS
Time: 11:00 AM – 11:15 AM

Authors

  • Joe Fandrich Presenting Author
    Mesa State College, Grand Junction, CO

Abstract

Unsorted chert breccia deposits situated at the base of the Black Dragon Member of the Triassic Moenkopi Formation in the San Rafael Swell, and a megabreccia associated with extraordinary soft-sediment deformation in the upper 80 – 100 feet of the Hoskinnini Member of the Moenkopi Formation in the White Canyon area of southeastern Utah may share a common history. Chert fragments within the Black Dragon Breccia as well as chert fragments present within the Long Canyon Megabraccia appear to have been scoured from Permian Kaibab Limestone, transported eastward and deposited upon the western Pangaea shoreline. Impact related microspherules have been discovered associated with the Black Dragon Breccia. The Black Dragon Breccia and Hoskinnini are rock correlative and lie unconformably upon Permian age rocks.

Field and laboratory observations support the hypothesis that the Black Dragon Breccia and the Long Canyon Megabreccia may represent a bolide impact event horizon resulting from the impact of a comet or asteroid west of Pangaea in the Panthalassa Sea sometime near the PermoTriassic boundary.