LATEST GUADALUPIAN MICROFAUNAS (CONODONTS, FORAMINIFERS) FROM WEST TEXAS

Latest Guadalupian microfaunas in West Texas are represented by the composite Jinogondolella altudaensis conodont zone. This zone is restricted to the Reef Trail Member (“post-Lamar”) of the Bell Canyon Formation in the Guadalupe Mountains, the uppermost part of the Altuda Formation in the Glass and Del Norte Mountains, and is reported here from the Lamar Limestone Member of the Bell Canyon Formation in the Apache Mountains. Material from the top of the Altuda Formation in the Del Norte Mountains shows a transitional evolutionary series and the probable first occurrence of the ensuing conodont cline, initiated by Clarkina postbitteri, which is the likely definer of the Upper Permian in China. Also, Jinogondolella granti, the last member of the genus in the Chinese sections, has been reported from the Reef Trail Member. Both of these reports have been questioned. New material from the Lamar Limestone in the Apache Mountains display a well-defined growth sequence of Jinogondolella granti and sparse material of primitive Clarkina postbitteri, which confirms both of their occurrences in West Texas. These two forms characterize the last Guadalupian fauna and the first Upper Permian fauna in China, respectively, and demonstrate that a complete succession of the Guadalupian is displayed in West Texas. Small foraminifer species of the genera Pseudoammodiscus, Orthovertella, Nodosaria, Ichthyolaria, Geinitzina, and Abadehella present in the same beds in the Apache Mountains as the conodonts corroborate a latest Guadalupian age for the fauna. Ostracods and the radiolarian species Follicucullus cf. F. ventricosus also occur with this assemblage.