Back Ridge, Patterson Hills, Guadalupe Mountains National Park: a biostratigraphic correlation and reference section for the Capitanian Stage GSSP

Three of the middle Permian GSSPs (Global Stratotype Sections and Points) that have been ratified by the International Commission on Stratigraphy are located within Guadalupe Mountains National Park (GMNP) in west Texas. These are the Guadalupian Series (Middle Permian) and its component Roadian, Wordian, and Capitanian Stages. The Capitanian GSSP is currently located in the Pinery Member of the Bell Canyon Formation on Nipple Hill, southeast of El Capitan. While it meets many of the criteria for an ideal GSSP, it is located nearly at the top of Nipple Hill, leaving barely a meter of section to assist with correlations. Back Ridge, located in the Patterson Hills, southwest of El Capitan, is comprised of the Cherry Canyon Formation and the Bell Canyon Formation, with the Pinery Member of the Bell Canyon Formation comprising the middle of the ridge stratigraphically. The base of the Capitanian Stage is defined by the First Appearance Datum (FAD) of Jinogondolella postserrata after its ancestral species, Jinogondolella aserrata. The transitional morphotype of J. aserrata to J. postserrata spans three beds (approximately 0.6 meters) on Back Ridge. The FAD of J. postserrata immediately follows this transition. The carbonate petrology is described here from slabs to accompany the chronomorphocline description. The results of this research project located the FAD of J. postserrata on Back Ridge in the Pinery Limestone Member. The more extensive section on Back Ridge will be the primary reference section for the Capitanian GSSP on Nipple Hill.