Eocene and oligocene benthic foraminifera in the eastern Gulf Coast

Small benthic foraminifera from four localities were examined for the degree, and timing of faunal changes associated with the Eocene/Oligocene boundary in the eastern Gulf Coast region. A preliminary study of the development of the stratigraphic package straddling the boundary was constructed. In addition, preliminary tests of abundance variation in the fossil record to paleoecolgic analysis were conducted.

Four sections were examined. These sections represent a range of paleoecologic settings ranging from clastic shelf to carbonate bank. Analysis of the degree and timing of faunal change across the Eocene/Oligocene boundary in the eastern Gulf Coast indicate a low and inconsistent amount of change. The degree of faunal change observed is lower than previously reported with few common species becoming extinct at or here the boundary in the entire study area. The greatest change occurs in the clastic shelf and carbonate bank settings. However, a single causal mechanism can not be invoked to explain the observed faunal changes. Preliminary study of the development of the stratigraphic package in the study area indicates that the Eocene/Oligocene boundary is complete and the location of the major fades transition is a result of the interaction of sea level and the suppression of carbonate deposition by distal elastics. Analysis of abundance variation in the fossil record provides a potential tool for applying modem ecologic modeIs to the past. Preliminary tests of fossil abundance variation were conducted to examine this possibility. The results indicate that the nature of the benthic foraminiferal record is such that meaningful patterns maybe recognized. In spite of the loss of large amounts of information to taphonomic processes.