Lower Permian stratigraphy of east-central Nevada and adjacent Utah

Abstract

The Permian section near Ely, Nevada, consists of, in ascending order: Riepe Spring Limestone, a bluff-forming limestone with abundant corals, and Reipetown Sandstone, a buff to red very coarse-grained siltstone with minor carbonates, both formations of Steele (1960); Arcturus Formation, divisible into a Lower Member composed of alternating medium-bedded limestone and buff siltstone, and an Upper Member composed of alternating thin-bedded limestone and buff to red siltstone and gypsum; and Kaibab Limestone, a massive bioclastic limestone. The Wolfcamp-Leonard boundary occurs within the Arcturus Formation. West of Ely the Riepe Spring Limestone and Reipetown Sandstone thin and change into thin-bedded cherty limestone. These beds, plus the basal part of the Arcturus Formation, form the Carbon Ridge Formation at Dry Mountain at Eureka. At Dry Mountain, minor clastic chert occurs in the Arcturus Formation, and beyond to the west clastic chert replaces most of the limestone to form the conglomeratic Garden Valley Formation. The cherty limestone at the base of the Garden Valley is apparently equivalent to the upper part of the Carbon Ridge Formation at Carbon Ridge. Eastward in Utah the Riepe Spring Limestone is recognizable in the Confusion Range, but is almost unrecognizable in the Needle Range. The dolomite content in the Reipetown Sandstone usually increases to 25 percent of the formation in the Confusion and Needle ranges. The Arcturus Formation thins and undergoes moderate lithologic changes. It is equivalent to the rocks above a horizon 300 feet below Bed A of the Arcturus Formation as mapped in the Confusion Range by Hose and Repenning (1959, 1963).