An enigmatic limestone breccia in the Guilmette Formation of southeastern Nevada will be investigated. The Guilmette Formation spans the Late Devonian Frasnian-Famennian stage boundary. The breccia is exposed in seven ranges over at least 5000 square miles and has known thicknesses ranging from 25 to 435 feet; it encompasses a volume of 100 cubic miles or more. The breccia appears to be a single sedimentary carbonate bed not tectonically, diagenetically, or solution-derived. It has a sharp, scoured base, and contains haphazardly oriented, lithologically heterogeneous clasts that fine-upward. Some clasts reach 50 feet or more in longest dimension. The breccia occurs in a shallow-water marine setting, based on characteristics of overlying and underlying beds. It suggests catastrophic origin, perhaps related to an extraterrestrial object impacting Earth. The breccia and its significance will be investigated through: stratigraphic analysis of overlying and underlying beds to refine its paleogeographic setting; characterization of its internal properties to determine provenance, transporting and depositing mechanisms, and to test the single-event hypothesis; narrowing its age designation through closer biostratigraphic zonation; searching for links to possible extraterrestrial genesis, e.g., shocked quartz, geochemical anomalies, etc.
