Dinocyst biostratigraphy of Cenomanian-Coniacian' formations of the western Gulf Coastal Plain, southern United States

Abstract

This palynological investigation of Cenomanian-Coniacian formations of Texas, U.S.A., consists of an examination of 63 outcrop samples from 9 stratigraphic sections exposed in 7 Countries in a north-south trend from about Dallas to Del Rio. The Grayson Formation, the Eagle Ford Formation, the lower Austin Chalk, and their southern equivalents were examined for palynological data. Most of the samples are rich in dinocyst assemblages. Seventy-eight dinocysts species of 47 genera, 3 acritarch species of three genera, and 28 spore-pollen species of 20 genera are recognized and their stratigraphic distribution documented. Systematic descriptions and illustrations of all dinocyst and acritarch taxa are given. Spore-pollen taxa have rare occurrences in all the studied sections and are thus only listed and illustrated.

The stratigraphic distribution of dinocyst taxa indicates that Cyclonephelium eisenackii and Ovoidinium verrucosum terminate at the end of the Cenomanian and Litosphaeridium siphoniphorum at the end of the Turonian. Dinogymnium acuminatum and Chatangiella victoriensis appear in the Coniacian.