Mississippian orogenic sediments deposited during during the Antler orogeny and exposed in east-central Nevada record the initial breakup of the Cordilleran geosyncline. They also contain one of the thickest, richest,

End_Page 283------------------------------

yet most under-explored source rock-reservoir packages in the western United States. Numerous geologists have studied the Chainman Shale-Diamond Peak Formation, yet the depositional setting of these formations, a factor critical to effective exploration for these attractive targets, is still controversial. In 1974, F. G. Poole suggested that the entire sequence was deposited as turbidites at abyssal depths, calling these rocks "Antler flysch." B. R. Wilson and S. W. Laule thought these same sediments were largely nearshore marine to fluvial molasse sediments. Regional studies in east-central Nevada reveal 2 dramatically different facies within the Mississippian: a turbidite facies consisting of incomplete Bouma sequences, interturbidite shales, and disordered conglomerates; and a fluv al-deltaic facies consisting of well cross-bedded,, nearshore marine sandstones and fluvial conglomerates, nonmarine to shallow-marine shales, and marine limestones. In several areas these 2 facies are separated by only a few miles, yet structural juxtaposition is not likely. Rather, it appears the turbidite facies is older than the shallow-water facies and represents Early Mississippian in-fill of the narrow Antler trough. The fluvial-deltaic facies represents regressive deposition that prograded over the Antler trough in Late Mississippian time. Both facies contain rich source rocks and the more widespread fluvial-deltaic facies contains numerous reservoirs and potential stratigraphic traps.

End_of_Article - Last_Page 284------------