Abstract: Eocene Structuring in East-Central Basin-and-Range

Gary W. Newman

Surface and subsurface study of the Eocene Sheep Pass Formation in White Pine and Nye Counties, Nevada, reveals that contemporaneous faulting of considerable magnitude controlled both margins and depositional environments of Lake Sheep Pass. Abrupt changes of facies and thickness, localization of boulder conglomerates, and the emplacement of large slide blocks (up to 150 m thick) are consequences of fault movement contemporaneous with the deposition of the Sheep Pass Formation. Much of the Eocene faulting parallels the present trend of Basin-and-Range faulting and, in one case, a presently active horst block can be shown to be bounded by faults that started moving in Eocene time. It is suggested that the Eocene Basin-and-Range faulting as well as the tectonic controls of akes Flagstaff and North Horn and the Oligocene Basin-and-Range volcanic eruptions are early consequences of the emplacement of an anorthosite-granulite plume under western North America.

AAPG Search and Discovery Article #90964©1978 AAPG Rocky Mountain Section Meeting, Salt Lake City, Utah