Organic-walled microplankton biostratigraphy and paleoecology of the Maastrichtian Prairie Bluff Chalk formation of central and western Alabama

Marine organic-walled microplankton biostratigraphy of the Maastrichian Prairie Bluff Chalk is documented. A total of 69 dinoflagellate species were identified in the Prairie Bluff Chalk. Samples were studied from three sites in central and western Alabama (Tombigbee River, Millers Ferry, and Braggs). Also included were several samples of the overlying Clayton Formation, and the underlying Ripley Formation.

The species and their stratigraphic ranges were compared with other coeval sections in the U. S. and Europe. Dinoflagellate Zones Va and Vb of Wilson (1974) are recognized in the Prairie Bluff Chalk. This suggests the age of the Prairie Bluff Chalk is restricted to late Maastrichtian. The Prairie Bluff Chalk correlates to the upper Providence Formation of Georgia (Firth 1984); the lower Providence being early Maastrichtian. The basal Clayton Formation may be latest Maastrichtian in age