between Professor and Castle Valleys is a land surface covered by well rounded pebble- to cobble-sized gravels, chiefly composed of igneous and metamorphic clasts. They are not terrace gravels related to the Colorado River located 320 meters (1,000 feet) below. Rather they have weathered from the Cutler Formation, having been deposited in braided stream channels approximately 300 million years ago.
Strike valley within the Early Permian-age Cutler Formation with Adobe Mesa on left. While not obvious here, this land surface is littered with well rounded stream cobbles. (Click on image to enlarge.)
Well rounded cobble-sized igneous and metamorphic clasts that have weathered from the Cutler Formation, with their provenance being the Precambrian basement rocks in the ancestral Uncompahgre Mountains that existed further east during Permian time.