Geology of the Ruby Site Area, Wyoming 48 CA 302

Quaternary sediments in the Ruby site area are of post-altithermal age. Two past alternating cycles of deposition and erosion are evident. The oldest depositional unit contains an archaeological site which yielded a radiocarbon date of A.D. 280 ± 135 years. This older formation was deposited in post-Kaycee-pre-Lightning time. A stratigraphic unit of this age has not been previously reported in the Powder River Basin and is herein named the South Butte formation. The youngest depositional unit in the area is the Lightning formation. Erosion and downcutting began about 1900 and has continued to the present.