By: L. F. Hintze and F. D. Davis
Long Ridge rises about 700 feet above the floor of the Sevier Desert some 30 miles west of Delta, Utah. The Sevier Desert is a broad basin and range valley in which Quaternary surficial deposits conceal relationships of Tertiary and older rocks beneath. Interest in and ideas on the origin of the Sevier Desert basin have increased because of recent availability of regional geophysical data. Oligocene bedrock exposed on Long Ridge constrains subsurface interpretations of geophysical data by showing that the west edge of the Sevier Desert is not underlain by late Cenozoic valley fill; instead Long Ridge is probably underlain by more than 1,000 feet of Oligocene conglomerate and tuff that rests directly on lower Paleozoic, probably entirely Cambrian, strata, as indicated by bedrock exposed in adjacent areas.
No previous geologic map of this quadrangle has been published except for reconnaissance mapping done in connection with regional map compilation. Field work was facilitated by availability of excellent 1:25,000 color aerial photographs taken for the U.S. Department of Defense mobile missile site evaluation project.
Pages: 10 p.
Plates: 2 pl.
Location: Millard County
Media Type: Paper Map