Formation 5 : Fundamental rock- stratigraphic unit that is mappable and lithologically distinct from adjoining strata and has definable upper and lower contacts
National Park Service, U.S. Department of the Interior, Geologic Resources Division, Natural Resource Program Center, Wolf Trap National Park for the Performing Arts, Geologic Resource Evaluation Report, Natural Resource Report NPS/NRPC/GRD/NRR 2008/041, Technical Geologic Terms, Denver, Colorado, USA 2008. http://www.nature.nps.gov/geology/inventory/public ations/reports/wotr_gre_rpt_view.pdf, (ND/ Lndsld - Amer) {923}