By: J. J. Anderson
The Circleville Mountain quadrangle lies in the southeastern Tushar Mountains in the southern High Plateaus subprovince of the Colorado Plateau physiographic province. This subprovince is structurally transitional between the block-faulted Basin and Range Province to the west and the more stable Colorado Plateaus to the east.
The Marysvale volcanic field, one of the largest eruptive piles in the western United States, straddles the High Plateaus and extends into the Basin and Range. The Circleville Mountain quadrangle in the southern part of the field contains part of one of its most voluminous and extensive accumulations. This accumulation, the Mount Dutton Formation, consists of rock erupted from a series ofclustered stratovolcanos distributed in a crudely defined east-trending zone across the southern Tushar Mountains. The eastern end of this zone occurs about 10 miles east of the mapped area, in the southwestern Sevier Plateau; the western end of the zone is found in the northern Black Mountains, about 25 miles to the west. Because of repetition by numerous high-angle dip-slip faults, and because of the resistant nature of the rocks, a significant part of this volcanic vent complex is well exposed in the quadrangle. The Osiris Tuff, a regional ash-flow tuff interbedded high in the Mount Dutton section, and minor accumulations of local volcanic rocks postdating the Mount Dutton Formation also occur in the quadrangle.
Pages: 6 p.
Plates: 2 pl.
Location: Beaver County, Garfield County, Iron County, and Piute County
Media Type: Paper Map