STRATIGRAPHY OF THE BELL CANYON FORMATION IN THE NORTHWESTERN PART OF THE APACHE MOUNTAINS, SOUTHEASTERN CULBERSON COUNTY, WEST TEXAS

Middle Permian marine (Bell Canyon Formation) strata along the southwestern margin of the Delaware Basin in southeastern Culberson County, West Texas provide excellent exposures of slope and basinal strata, useful fossils for age dating, and a variety of interpretations of possible depositional environments. A surficial geologic map of about a seven square kilometer area of the northwestern Apache Mountains, located to the west of and bounded on the southeast by Texas FM 2185 about 60 kilometers northeast of Van Horn, West Texas demonstrates the presence of several significant and extensive debris flows and a complex structural setting for Late Guadalupian/Lopingian age strata in the area. The stratigraphic succession ranges from the Bell Canyon Formation (about 200 meters) into the Rustler Formation. The mapped limestone units of the Bell Canyon Formation can be tentatively correlated to parts of its well known limestone members (Hegler, Pinery, Rader, McCombs, Lamar, and Reef Trail) as originally described in the Guadalupe Mountains by using microfossil data from radiolarians, conodonts, fusulinaceans and other foraminifers. The upper boundary of the Guadalupian Series can be traced across the area in a transitional interval of a few meters just below typical strata of the Castile Formation. This interval is identified by the presence of the conodont subspecies Clarkina postbitteri hongshuiensis, the biostratigraphic marker for the uppermost conodont zone of the Guadalupian Series in China. Several major subaqueous gravity flows present in the map area aided in the mapping of the various units of the Bell Canyon Formation. Microfossils present, especially the conodonts, aided in providing a framework for a proposed correlation of the Bell Canyon with its various members in the Guadalupe Mountains. Analysis of one of the major, thick subaqueous gravity flows within the Bell Canyon Formation in the mapped area provides information about its clast lithofacies, biofacies, lateral extent, timing of emplacement and allochthonous debris origin.