This volume targets two areas of the American Southwest: the GuadalupeMountains andDelaware basin, Texas, and the southern Inyo Mountains, California. In Texas, detailed lithostratigraphy of a complete section of the latest Guadalupian Reef Trail Member of the Bell Canyon Formation is presented for a better framework to study late Guadalupian events. Geochemical tephrochronologic frameworks are developed for the Rader Limestone Member of the Bell Canyon Formation and the Manzanita Limestone Member of the Cherry Canyon Formation to demonstrate the utility of geochemically identifying bentonites to show their correlation and to trace units from basin to shelf. In California, the general overall depositional regime of the Darwin basin of Mississippian to Early Permian rocks is presented along with focused studies of a short-lived Permian carbonate complex and of a latest Pennsylvanian-Permian major channel deposit.