GEOLOGY, BULL FORK AND PARTS OF ADJACENT 7.5 MIN. QUADRANGLES, PANCAKE RANGE, EAST CENTRAL NEVADA

Windows through Cenozoic cover in the northern Pancake Range expose medial to late Paleozoic rocks and Cretaceous sediments deformed by Early and Late Cretaceous orogeny and Basin and Range extension. Oligocene volcanics erupted over Cretaceous weathering surface and were faulted during Miocene extension. Quaternary illuvial and alluvial sediments floor the valleys.

Late Devonian Devils Gate LS is overlain by either a complete or truncated Pilot SH section spanning the Antler orogeny followed by Joana Limestone, Dale Canyon Formation, Chainman Shale and Diamond Peak clastics. Cretaceous intrusives, syn-orogenic Newark Canyon FM, in channels, and Members of the Sevier age Sheep Pass FM preceded a regionally typical Oligocene volcanic stack of basal rhyodacites, intermediate flow rocks and an upper sequence of silicic ignimbrites. Undifferentiated Needle Range Group rhyodacite may extend its mapped extent further west than currently recognized.

Early Cretaceous compression is manifested by overturned, east-verging folds and a large horse structure. Late Cretaceous shortening preceded Sheep Pass Members A and B, basinal depofacies. Neogene Basin and Range faulting and rafting of the range from the White Pine-Grant Range block are likely synchronous with formation of the Northern Nevada Rift. A super-durable clast conglomerate covers a profound discontinuity between the Moody Mountain area and the rest of the Pancakes, to the east that indicates shuffling of Pancake Range structural domains during this extension and uplift. Overall, it appears that there was little to no tilting of the Pancakes in this area after the Cretaceous.