By: D. M. Miller, T. E. Jordan, and R. W. Allmendinger
The Crater Island 7.5-minute quadrangle lies in northwestern Utah and includes part of the northern Silver Island Mountains and the adjacent Pilot Valley Playa. A thick sequence of miogeoclinal Paleozoic rocks, ranging from Cambrian to Permian in age, underlies the Silver Island Mountains in the quadrangle. This sequence was faulted and then intruded by several Jurassic granitoid plutons and numerous dikes. During the Cenozoic, the mountain range was blocked out by north-striking basin-and-range faults that separate it from adjacent basins containing thick Cenozoic deposits. During Pleistocene time, Lake Bonneville inundated much of the area covered by the quadrangle; shorelines cut into bedrock and alluvial fans indicate that the lake reached about 1589 meters in elevation at its maximum depth. Mining operations in several locations have explored skarn mineralization associated with the Jurassic granitoids.
This report on the Crater Island quadrangle and its companion report on the adjacent Lucin 4 SW quadrangle represent continuations of geologic-map studies in the northwestern Utah area.
Pages: 16 p.
Plates: 2 pl.
Location: Box Elder County
Media Type: Paper Map