Fig. 4. Chronostatigraphic section of North Louisiana. (From Shreveport Geological Society, 1987.) Note: The Schuler Formation of the Cotton Valley Group has only recently been assigned to the Lower Cretaceous; most authors prior to the 1980s assigned it to the Upper Jurassic. Also note that outcropping beds of the Eocene Claiborne Group (including the Cook Mountain Formation) that lie immediately above the Wilcox Group are not shown.