MODUGNO, ANDREW, McLaren/Hart Environmental Engineering Co., Burbank, CA, and VICKI PEDONE, Department of Geological Sciences, California State University, Northridge, CA

ABSTRACT: The Lithostratigraphy of the Middle to Upper Devonian Lost Burro Formation in the Panamint Mountains

Lack of detailed mapping of the structural geology has hindered measurement of a complete section of the Middle to Upper Devonian Lost Burro Formation in the type locality at Lost Burro Gap in the Panamint Mountains. Using physical correlation of carefully defined marker beds, a complete, 804.5-m-thick composite section of the Lost Burro Formation was measured in the type locality. The formation was divided into eight members based on color, mineralogy, and crystal size. The lower 370 m are dominantly dolostone and the upper 434.5 m are dominantly limestone. The transition from dolostone to limestone is gradational and occurs over a 71-m-thick interval. In the type locality, depositional texture largely has been obscured by dolomitization, recrystallization during deep burial in the M sozoic, and tectonic shearing. Within most members, 1 to 5-m-thick cyclic units are defined by minor variations in color and texture, and sometimes by fossil content. The best preserved cycles have fossiliferous packstone at the base, overlain by fossiliferous wackestone, and capped by either bioturbated or laminated mudstone. Poorly preserved cycles grade from light-colored, coarsely crystalline dolostone or limestone at the base to dark-gray, finely crystalline dolostone or limestone at the top. Evidence of prolonged subaerial exposure, such as mudcracks, teepee structures, evaporites, and paleosols, is uncommon. The cyclic units may represent shallowing-upwards sequences that result from 20 to 100-ka (Milankovitchian) sea level fluctuations.

AAPG Search and Discovery Article #90992©1993 AAPG Pacific Section Meeting, Long Beach, California, May 5-7, 1993.