Dinoflagellate paleoecology and biostratigraphy of the Middle Eocene Tallahatta and Lisbon Formations from the Baldwin County, Alabama, Core

Abstract

This study documents the occurrence of dinoflagellate cysts from the Middle Eocene Tallahatta and Lisbon Formations in the Baldwin County, Alabama, Core. This is part of a larger project being conducted by the ARCO Depositional Sequence Analysis Group to gather paleontological, sedimentological, paleomagnetic, geophysical, and geochemical data from the Alabama Coastal Plain for the purpose of calibrating the Tertiary time scale with the sequence stratigraphy of the Gulf region.

A total of 101 taxa were identified, including 55 genera, 91 species, and 10 subspecies.

Statistical analyses were run on the data collected to identify paleoecologic patterns and to relate these patterns, if possible, to sedimentary sequences. Diversity curves generated from the data show that there is usually a rise in diversity at sequence boundaries and at introsequence surfaces. Q-mode cluster analysis and detrended correspondence analysis indicate that samples tend to cluster within sequences. R-mode cluster analysis was performed and live informal cyst associations are discussed.

Comparison of this studies assemblage with ranges published by Goodman and Stover (1975, 1983), and Edwards (1982) confirm the Middle Eocene age assigned to these units.