PLANKTONIC FORAMINIFERAL BIOSTRATIGRAPHY OF UPPER CRETACEOUS STRATA, DIXON CORE, NORTH CAROLINA

Between 2001 and 2006, a Federal, State, and university cooperative drilled six cores in the North Carolina Coastal Plain to study the stratigraphy and hydrogeology of post-Jurassic strata. To date, foraminifers have not been analyzed from any of these cores. Foraminifers were examined from 58 samples taken from 630 feet of Santonian through Maastrichtian strata of the Tar Heel, Bladen, Donoho Creek, and Peedee Formations in the Dixon Core. More than 190 foraminiferal species were recognized from 8300 picked specimens. Fifty-six planktonic species were recognized of which Globigerinelloides prairiehillensis and Rugoglobigerina rugosa compose the majority of specimens. The planktonic foraminiferal zones recognized, from oldest to youngest, include the Globotruncana elevata, G. ventricosa, Radotruncana calcarata, Globotruncanella havanensis, Globotruncana aegyptiaca, and Gansserina gansseri zones. The Maastrichtian Racemiguembelina fructicosa-Contusotruncana contusa and Abathomphalus mayaroensis zones are not recognized in the Dixon core. Only a few specimens of two planktonic species, Globotruncana canaliculata and Guembelitria cretacea, are observed in the last 41 feet of Maastrichtian strata of the Pee Dee Formation. In addition, the planktonic-benthic ratio reaches a maximum within the Tarheel Formation just prior the Santonian-Campanian boundary and in the late Campanian Donoho Creek Formation and falls quickly to zero just after each maximum indicating dramatic lowering of sea level at those times. However, in the late Maastrichtian, benthic foraminifers still abound although in slightly decreasing numbers up to the K-P boundary.