Abstract

Upper Proterozoic to Lower Cambrian metasedimentary rocks in the southern Deep Creek Range are divisible into two stratigraphic sequences that are separated by the Birch Canyon fault. It is unclear whether the Birch Canyon fault repeats two coeval but lithologically distinct sections, or whether it reflects bedding parallel slip along a marble/quartzite contact within an essentially continuous stratigraphic section.

Below the Birch Canyon fault is the Trout Creek sequence, about 3,600 m thick, which has been previously divided into seven units (Misch and Hazzard, 1962). In ascending order these units are composed of (1) schist, (2) marble, (3) quartzite, schist, and metadiamictite, (4) quartzite, (5) metadiamictite, schist, and quartzite, (6) schist and quartzite, and (7) orthoquartzite. Units 3–7 have been previously correlated to lithologically similar strata of the Sheeprock and Brigham Groups in the Sheeprock Mountains (Christie-Blick, 1982).

Above the Birch Canyon fault is an apparently conformable sequence, about 2,200 m thick, of six units that appear to be equivalent to units B–G of the McCoy Creek Group in the Schell Creek Range (Misch and Hazzard, 1962). In ascending order these units are composed of (B) schist, metasiltstone, and marble, (C) quartzite, (D) orthoquartzite, (E) schist and quartzite, (F) orthoquartzite, and (G) schist and metasiltstone. Unit G is conformably overlain by the laterally extensive Prospect Mountain Quartzite.

Correlation of the McCoy units B–F to the Caddy Canyon Quartzite of west-central Utah (Christie-Blick, 1982) is problematic. Deposition of some McCoy Creek units may have been contemporaneous with nondeposition in west-central Utah, or more speculatively, deposition of the McCoy Creek Group may have been isolated from deposition to the east, perhaps due to barriers created by extensional faulting of the incipient passive margin.