Description
Approximately 10,000 feet of Devonian through Permian strata are exposed beneath Tertiary volcanic rocks in the Pancake Range. An incomplete section of Devonian Guilmette Formation exposes 1,420 feet of limestone. The Mississippian Chainman Shale, 1,230 feet of black shale, is overlain by the Scotty Wash Quartzite. Though the Scotty Wash is incomplete, 2,186 feet of basal shale and quartzite are exposed, as are 891 feet of the top of the formation. The overlying Diamond Peak Formation, comprising 993 feet of black shale, quartzite, and chert-clast conglomerate, is the youngest Mississippian clastic unit exposed. The Ely Limestone is divided into four members. Member A is 305 feet of argillaceous limestone containing Rhipidomella nevadensis, a Chester guide fossil. Member B contains 475 feet of Morrow limestone. Limestones of Member C are 1,738 feet thick; 886 feet of these strata are Morrow, and 852 feet are Derry rocks that lie above the Chaetetes-Profusulinella faunizone. Member D is Derry to Desmoines (?), and comprises a maximum of 866 feet of conglomeratic limestone. Member D either lenses out, or is truncated by a regional unconformity, or both. The Permian Rib Hill Sandstone contains 822 feet of siltstone and sandstone; the top of the formation has been eroded. Tertiary ignimbrites and basalts unconformably overlie folded Paleozoic strata. The upper Paleozoic section is involved in an eastward-overturned, south-plunging syncline striking N 30° W. Western truncation of the fold indicates possible northern extension of a major range-front fault. Stratigraphic and structural information from the Pancake Range, when integrated with regional data, show that orogeny was continuous in the Cordilleran geosyncline since the Antler orogeny began. Orogenic movement began in central Nevada in the Upper Devonian, gradually moved eastward through eastern Nevada and western Utah in the Permian through Jurassic, then into central Utah in the Cretaceous. Thus, orogeny began in the eugeosyncline and passed through the miogeosyncline toward the shelf in a wave-like progression.
