A NEW RECORD OF LATE PALEOCENE RANIKOTHALIA CANTENULA FROM THE SALT MOUNTAIN LIMESTONE, CLARKE COUNTY, ALABAMA

Ranikothalia cantenula is an important macroforaminiferan biostratigraphic marker in the Caribbean region. It is a major component of the “catenula fauna” of middle to late Paleocene age throughout the region. It has been documented in sections from Cuba, Hispaniola, Puerto Rico, and Jamaica as well as locations in Central America. Ranikothalia catenula occurs in rocks as old as planktonic foraminiferal biozone P3b in Jamaica and ranges through biozone P5 in Cuba. It has not been identified in early Eocene age rocks. While widespread in Paleocene rocks in the Caribbean, it has not been reported from the North American mainland. Macroforaminiferal faunas of Paleocene age are known from localities in Florida and the eastern Gulf Coastal Plain but these sections do not contain Ranikothalia catenula.

Detailed studies of thin sections of the Salt Mountain Limestone of Clarke County, Alabama have identified specimens of Ranikothalia catenula for the first time. The Salt Mountain Limestone is a lowstand foralgal reef with abundant macroforaminifera and coralline algae. Distinct zonations of frondose and crustose coralline algae occur within the Salt Mountain Limestone representing “catch-up and “keep-up” carbonate platform development respectively. Specimens of Ranikothalia catenula identified in this study are associated exclusively with the crustose coralline algae zonations within the Salt Mountain.

The macroforaminifera previously recorded from the Salt Mountain Limestone include Discocyclina blanpiedi and Athecocyclina stephensoni. These taxa had long been associated with the “catenula fauna” in Cuba and Jamaica so the occurrence of Ranikothalia catenula in the Salt Mountain is not unexpected. This occurrence does represent the first occurrence of Ranikothalia catenula in a location originating on the North American Plate. Further work on the Salt Mountain Limestone and other Paleocene carbonate units in the Gulf coastal Plain may provide some insight into the distribution of the Caribbean macroforaminiferal fauna