BIOSTRATIGRAPHY AND PALEOENVIRONMENT OF THE LATE PALEOCENE FORAMINIFERA OF THE “TOULMIN BED”, OF THE SALT MOUNTAIN LIMESTONE, CLARKE COUNTY, ALABAMA

The “Toulmin bed” of the Salt Mountain Limestone of Alabama is the basal bed of the unit and is the origin of the foraminifera fauna described by Toulmin in 1941. The “Toulmin bed” is a marine sand and was originally reported as a 0.1 m thick bed immediately beneath the massive limestones of the Salt Mountain. The bed is no longer exposed at Salt Mountain but a re-study of the foraminifera was made possible by the processing of a bulk archival sample housed in the Biostratigtraphy Laboratory at Ball State University. The “Toulmin bed” contains abundant planktonic, benthic, and macro foraminifera, bryozoan, and coralline algae .

The planktonic assemblage includes Morozovella angulata, Acarinina intermedia, and Planorotalites pseudomenardii. These indicate a Paleocene (Thanetian) age and with the absence of Acarinina soldadoensis can be correlated with biozone P4b. The diverse benthic foraminifera identified in this bed includein this bed are Guttulina problema, Anomalinoides acuta, Lenticulina degolyeri, Bulimina sp., Lagena acuticosta, Discorbis washburni, Gyroidinoides madrugaensis,Darbyella sp., Cibicides praecursorius, Cancris auriculu, Ceratobulimina perplexa., Pulsiphonina prima, and Osangularia expansa among others. Macroforaminifera include Discocyclina weaveri and Athecocyclina stephensoni. This assemblage of foraminifera is associated with the Anomalinoides-Pulsiphonina assemblage suggesting middle neritic depths (30 m-60 m).

The Salt Mountain Limestone represents a late Paleocene foralgal reef developed at lowstand. The “Toulmin bed” underlies the reef succession. The middle neritic setting suggested by the benthic foraminiferal assemblage and the abundance of bryozoan and coralline algae support the interpretation of the “Toulmin bed” as a pre-reef sedimentary unit.