1. Map showing relative erodibility of geologic materials in the Parker quadrangle, Arapahoe and Douglas Counties, Colorado [cartographic material] Yale Public content 1972. 2013-02-21T16:45:34Z. 2013-03-18T22:37:25Z. Maberry, John O., 1935-. U.S. Geological Survey. English. Public. Colorado, Arapahoe County, and Douglas County.