The Quaternary Alluvium comprises channel, floodplain and terrace deposits along Beaver Creek. These deposits are in contact with the Tertiary Verde Formation in the southwestern portion of the watershed. The channel and floodplain deposits consist mainly of poorly sorted sand, gravel, silt, and clay.  The terrace deposits consist mainly of fine layers of sand, silt, clay, and gravel.

Reference:

Owen-Joyce, S.J. and Bell, C.K., 1983 Appraisal of Water Resources in the Upper Verde River Area, Yavapai County, Arizona, Arizona Department of Water Resources Bulletin 2 (Prepared by the U.S. Geological Survey), available online at: http://www.verde.org/usgs/usgsstud.html.