South River Volcanics 18. Andesite lava flow of South River Volcanics (unit Tsrm) within South River caldera (source of Wason Park Tuff). Andesite flow baked and oxidized the underlying volcaniclastic sedimentary rocks. View north, along west side of Red Mountain (northeastern Palomino Mountain quad). Bristol Head is in center distance across lower Clear Creek graben. Photograph by P.W. Lipman.