Geologic Map of The Saint John Quadrangle, Tooele County, Utah

By: Stefan M. Kirby

This map represents the geology of the Saint John quadrangle at 1:24,000 scale. The Saint John quadrangle, in southeastern Tooele County, Utah, covers a part of the floor of Rush Valley. Unconsolidated surficial deposits of Holocene to Pleistocene age cover nearly the entire quadrangle. These deposits include various alluvial fan and channel sediments, and lacustrine units deposited during both the transgression and regression of Lake Bonneville. Normal faults cut unconsolidated deposits in the western half and northeast corner of the quadrangle. In the northeast corner of the quadrangle, conjugate normal faults form a prominent horst and a series of west-facing scarps in late Pleistocene mixed alluvial and lacustrine deposits. Bedrock includes Pennsylvanian-age Oquirrh Group sedimentary rocks exposed in the southwest corner of the quadrangle, which consists of interbedded marine limestone and sandstone. Consolidated Tertiary fine-grained lacustrine basin fill of the Salt Lake Formation is exposed just north of the community of Saint John.

This CD contains geographic information system (GIS) files in ESRI file geodatabase and shapefile formats. Two plates, a geologic map at 1:24,000 scale and an explanation plate, and an 8-page booklet are also included in PDF format. The latest version of Adobe Reader is required to view the PDF files.