South Canyon Creek Dolomite Member, A Unit of Phosphoria Age in Maroon Formation Near Glenwood Springs, Colorado

Abstract

The South Canyon Creek dolomite member of the Maroon formation crops out at many places from South Canyon Creek, which is 4½ miles west of Glenwood Springs, Colorado, northwestward for 22 miles. The thickness of the member ranges from 1½ feet to 6 1/3 feet. The member commonly consists of a basal unit of medium gray, very fine-grained dolomite; a middle unit of light gray to light buff, dense dolomite; and a top unit, 1 foot or less thick, of thinly laminated fossiliferous limestone having an undulatory or wavy structure, suggesting an algal origin. A preliminary study of the fossils collected from the member has yielded a tentative list of 24 forms, comprising 19 pelecypods, 2 scaphopods, and 3 gastropods. The fauna appears to be a Permian one of Phosphoria age