About eight years ago there was discovered in the valley of the Little Colorado River between Hoi brook and Cameron in northern Arizona, evidence of an ancient alluvial terrace. Sand and waterworn pebbles largely derived from the Triassic Shinarump Conglomerate that once covered the area, form the deposit. The terrace which was formed by the gravels is now much dissected and remains only as the isolated flat tops of hills and ridges, the surfaces of which are covered with a desert pavement of waterworn pebbles. There are remnants also of later and lower alluvial deposits containing angular fragments of rock, of which a large proportion is made up of basaltic rocks from the San Francisco Peaks (Fig. 22).