Geological, geophysical, and engineering investigations of the Loveland Basin landslide, Clear Creek County, Colorado, 1963-65

Abstract

The Loveland Basin landslide occurred in a high mountain valley near the Continental Divide about 55 miles west of Denver during construction of the east portal area for the proposed Straight Creek Tunnel. The landslide developed in Precambrian bedrock, consisting of Silver Plume Granite with inclusions of metasedimentary rocks that are chiefly biotite gneiss and schist. Thin deposits of surficial material, consisting of moraine and soil mixed with talus, overlie the bedrock. The entire area is within the Loveland Pass fault zone. Individual faults within this zone are characterized by masses of breccia and gouge, ranging in width from less than 1 foot to 1,000 feet; these masses are separated by masses of less intensely sheared rock. The preexisting structure partly determined the shape of the landslide. The landslide is outlined by distinct scarps. The upper two-thirds of the landslide is downdropped in relation to the surrounding rock. The lower one-third of the landslide has been thrust upward and outward over the surrounding topography. Within the landslide mass, movement is indicated by tension fractures, which are most numerous near the margins of the mass.