Biostrat igraphy and Paleoecologic Tolerances of Oligocene through Paleocene Foraminiferal Assemblages of the Gulf Coast Basin

Operationally oriented biostratigraphic and paleoecologic models are developed for Paleocene, Eocene, and Oligocene foraminifera of the Gulf Coast Basin. This paper is a companion to Breard et al. (1993), which describes models of significant paleoecologic and biostratigraphic foraminifera of the Miocene through Pleistocene of this region. Key benthic paleoenvironmental markers (Figs. 1 and 2) for particular depth zones of the Paleogene are graphically presented with updated biostratigraphic charts (Figs. 3 and 4). Estimates of environment ranges for optimal stratigraphic utility are listed for all marker species on the biostratigraphic charts. It is important to note that species depth ranges on the two biostratigraphic charts are for their zones of optimum stratigraphic utility. It is possible to find shallower species reworked or ranging into deeper-than-normal zones, where they have little or no correlative value. It is also possible to find deeper water species ranging into shallower zones. This is especially true in the lower bathyal to abyssal zones of the Eocene and Paleocene, where species considered characteristic of these zones range above those environments (van Morkhoven et al., 1986). Because relatively few wells have penetrated such deep environments in the Eocene and Paleocene, we have relied on the literature for Paleogene deep-wate