LATE CRETACEOUS (SANTONIAN) VEGETATION FROM THE GULF COAST

An analysis of pollen, leaves, and charcolized wood from the Late Cretaceous (Santonian) Eutaw Formation and basal Mooreville Chalk Formation of central Alabama and eastern Mississippi reveals that each plant part possesses a unique taphonomic bias. Previous reconstructions of Late Cretaceous vegetation from the southeastern United States have indicated a dominance of angiosperms in both leaf and pollen data. By contrast data from charcolized wood (n=112) indicates that conifers comprised 95% of tree-sized vegetation. A smaller sample of siliconized wood (n=12) from the same horizon indicates that conifers composed 92% of the tree-sized flora. This distribution indicates that the dominance of conifers in the charcoal sample is not due to greater flotation times of conifer charcoal in the nearshore marine site of deposition.

The dominance of conifers in the northern Gulf of Mexico differs considerably from geographically close contemporaneous sites. This difference may be due to the influence of a disturbance regime of paleo-hurricanes and fire that favored conifers growing on barrier islands and proximal coastal areas. Previous studies have indicated that paleo-storm-tracks intersected the area of study.

Araucarians comprise the majority of barrier-island trees in central and western Alabama, with podocarps forming the majority in a coastal setting in eastern Mississippi. Large angiosperm fruit and seed size may indicate closed-canopy forests in some areas. Pines seem to have been present at more inland locations and/or only in the western portion of the area studied.