Upper Jurassic stratigraphy of some adjacent parts of Texas, Louisiana, and Arkansas

The Smackover and Buckner Formations and the Cotton Valley Group, which is composed in ascending order of the Bossier and Schuler Formations, are of definite' Late Jurassic age. The Norphlet Formation, although considered to be of Late Jurassic age, is unfossiliferous and its age is unproven. The Haynesville Formation, which is composed of part of the Cotton Valley Group and the Buckner Formation, is' not used here.