Abstract

Cooling paleoclimates over the period ca. 42 Ma to ca. 33 Ma were the driving force for the gradual disappearance of tropical and subtropical elements and the appearance of cooler elements in the palynofloras of east Texas. As a consequence, ten palynomorph assemblage zones and two biohorizons are recognized in 209 samples from 15 sections of the Crockett, Yegua, Caddell, Manning, and Catahoula formations. From oldest to youngest, the succession of biozones is: middle Eocene Nuxpollenites crockettensis Assemblage Zone, Bombapollis texensis Assemblage Zone, Bursera Assemblage Zone, Friedrichipollis claibornensis Assemblage Zone, and Reticuloidosporites pseudomurus Assemblage Zone; late Eocene Sequoiapollenites Assemblage Zone, Rhizophora FAD, Rhizophora Assemblage Zone, Nudopollis terminalis Assemblage Zone, Nudopollis terminalis LAD, Bombacacidites Assemblage Zone, and Pseudolaesopollis ventosus Assemblage Zone; and the early Oligocene Hypoxylonites Assemblage Zone. The age of the lower Catahoula Formation is early Oligocene based on the occurrence of Kallosphaeridium biornatum from a locality northwest of Huntsville, Texas. A short-term cooling event near the end of the Eocene set the stage for further changes in the early Oligocene. Use of these assemblage zones greatly increases the age resolution available for late middle Eocene to early Oligocene strata of the Gulf Coast.