Log for Joint SEPM-Colorado Scientific Society field trip, September 20-21, 1986: Late Paleozoic sedimentation and Laramide tectonics of the Sangre de Cristo Range, from Westcliffe to Crestone, Colorado

This trip will cross the northern Sangre de Cristo Range, from Westcliffe to Crestone, Colorado, by way of the Hermit Pass Road and the Rito Alto pack trail (Fig. 1 below; road and trail shown on Fig. 2). The traverse is designed to give the geologist a sample of the structure and stratigraphy of this part of the range. Emphasis will be on the relationship between the horst of the Sangre de Cristo Range and adjacent down-dropped valleys, on the Laramide thrusted structure of the range, and on the stratigraphy and depositional environments of Pennsylvanian and Permian sedimentary rocks in the range.

The northern Sangre de Cristo Range is composed mostly of Early and Middle Proterozoic crystalline rocks and Paleozoic clastic sedimentary rocks (see geologic map, Fig. 2). Proterozoic rocks, mostly gneiss and quartz monzonite, are overlain on the west side of the range by about 100 m of early Paleozoic quartzite, dolomite, limestone, and shale. Early Paleozoic rocks are in turn unconformably overlain by Pennsylvanian and Permian clastic rocks. Southeast of the range, in Huerfano Park, Paleozoic rocks are overlain by Jurassic and Cretaceous rocks of the Raton basin.