CONODONTS FROM A NEW REFERENCE SECTION NEAR THE ORIGINAL TYPE REEF TRAIL MEMBER, BELL CANYON FORMATION (LATEST GUADALUPIAN SERIES): BIOSTRATIGRAPHY, CORRELATION, AND SIGNIFICANCE

Previous research has established the Guadalupian-Lopinigian GSSP (Middle-Upper Permian Series boundary) in South China at the transition from Clarkina postbitteri hongshuiensis to Clarkina postbitteri postbitteri. The Reef Trail Member of the Bell Canyon Formation comprises the uppermost Guadalupian in its type region, and understanding its biostratigraphy is imperative for international Middle to Upper Permian correlations. The Reef Trail type section was established at McKittrick Canyon where it 1) had received the most study to that time, 2) represents the slope paleoenvironment for intercalation of fossils representing both the shelf and basin, and 3) lies near the type localities of several biostratigraphically important fusulinid species. Problems with the Reef Trail type section are that 1) it is a composite section, 2) it includes a considerable amount of covered section, and 3) the uppermost beds are not present, but lie on a nearby hill outside the boundaries of Guadalupe Mountains National Park.

Continuing fieldwork has produced three new reference sections critical to better documenting Reef Trail biostratigraphy. An auxiliary section near the original type section has less covered section and only a single, minor offset. In the Patterson Hills (western Guadalupe Mountains National Park), a complete basinal section extends from the underlying Lamar Member through the Reef Trail Member to the overlying Castile Formation. Another basinal section in the Patterson Hills better exposes strata immediately surrounding the Reef Trail-Castile contact. Conodonts from these sections represent the zone of Jinogondolella altudaensis, including J. altudaensis, J. xuanhanensis, J. crofti, J. cf. J. granti, and J. artafrons. Rare specimens represent other conodont genera as well. Morphologically advanced specimens of J. altudaensis characterize the uppermost beds of the Reef Trail Member, just below the Castile Formation in the Patterson Hills. These advanced specimens are transitional to the genus Clarkina. Clarkina postbitteri hongshuiensis, the first representative of the genus, has been recovered from just below the Castile in the Apache Mountains on the opposite side of the Delaware Basin.