“…The basal section of the Ogallala Formation contains large clasts of basalt, brown siltstone, chalcedony, chert, petrified wood, silcrete, quartzarenite (referred to as Potter Member quartzite), purple quartzite, and other quartzites [36]. The Rocky Mountains in New Mexico are the source of many of the gravels; however, erosion of the upper section of the Ogallala Formation has exposed locally formed silcrete and chalcedony layers deposited as angular clasts alongside the other gravels within the research area [36,37].…”