On the north side of the town of Minturn, the Leadville, Gilman, and Dyer Formations crop out. These rocks are most accessible in two places: in readouts along U.S. Highway 24, and in roadcuts along the railroad (Fig. 2). The northeast wall of the Eagle River canyon at this locality consists of a thick section of sandstones, siltstones, shales, and thin limestones of the Minturn Formation.
The Leadville Limestone/Dolomite consists of two members (Nadeau, 1971; Beaty et al., 1988a: this volume), the Red Cliff Member (below) and the castle Butte Member (above). The Red Cliff Member at Stop 1 consists bedded dolostone, principally of fine and medium grain size (Fig. 2). The dolomitization of these beds is regional in extent, and is interpreted by Horton (1985) to be of early diagenetic, sabkha origin. The Castle Butte Member at Stop 1 is limestone (Fig. 2), which has been described by De Voto (1985, p. 6-156) as “mixed-skeletal grainstones to packstones with readily visible echinoderm, brachiopod and solitary tetracoral fossils and abundant micritized foraminifera, green algae, and ostracods.” This is the southern limit of the limestone facies of the Castle Butte Member in this area.