Mount Morrison

Rock, from the geologic map

Fountain Formation. Paleozoic, about 323 to 273 million years old.

Maroon and red, arkosic, thick-bedded, coarse-grained to pebbly, cross-bedded fluvial sandstone and conglomerate containing thin layers of dark-maroon, hard (siliceous), micaceous siltstone and silty, fine-grained sandstone. Coarser beds commonly fill shallow channels. Sandstone locally bleached light tan to white. Clasts are well rounded to subrounded, as long as 25 cm, and composed mostly of Proterozoic rocks. Scott (1972) reported rare lower Paleozoic clasts in lower part of formation in Morrison 7.5-minute quadrangle. Thickness in quadrangle about 600 m; in Eldorado Springs quadrangle a measured section is 305 m thick (Wells, 1967). Mapped only in Denver Basin

This is the map unit under this crag's map point, read from the 1:100,000 sheet (Kellogg and others, 2008, USGS Geologic Investigations Series 3000). The point can be a few hundred metres from the rock, a cliff often stands on the line between two units, and at that scale a line on the map is about 100 m wide on the ground, so the wall itself may be the neighbouring unit. Every crag on this unit: Fountain Formation. Geology data: Macrostrat (CC BY 4.0), serving USGS and Colorado Geological Survey maps.