11 Paleontology (Posters)

SEA LEVEL CHANGE BASED ON FORAMINIFERAL DIVERSITY, CAMPANIAN THROUGH MAASTRICHTIAN DEPOSITIONAL SEQUENCES, CAPE FEAR RIVER, NC

Paper number: 11-8
Program: Technical Sessions
Time: 8:00 AM – 12:00 PM

Authors

Abstract

Foraminifera in depositional sequences represented by the Bladen, Donoho Creek and Peedee Formations were examined from six outcrops along the Cape Fear River. Samples from the base, middle and top of each section were wet-sieved to exclude silt-sized particles and dry sieved into five sand-sized fractions. One hundred plus Foraminifera were picked from the fine and very fine sand-sized fractions and separated by test types. Foraminifera were classified by planispiral, trochospiral, uniserial, biserial, and triserial test types to determine benthic and planktonic abundance. Percentages of each type within the samples were calculated. Foraminifera abundance and diversity were utilized to suggest correlation of sequences.

No Foraminifera were found in outcrops of the Bladen Formation. Disconformably overlying the Bladen and marked by a fossil lag is the Donoho Creek Formation. The lower Donoho Creek Formation shows an increase in the abundance of planispiral Foraminifera and planktic Foraminifera, averaging 51% and 26%, respectively. Both increases document a relative sea level rise between the Bladen and Donoho Creek Formations. The upper Donoho Creek Formation shows an increase to 64% in planispiral Foraminifera over the lower Donoho Creek, with spherical trochospiral tests decreasing to an average of 7%. These results suggest another relative sea level rise. Planispiral Foraminifera comprise approximately 66% of Peedee Formation samples, while trochospiral tests decrease from 22% in the lower to 0% in the upper. Foraminifera are absent at Wanets Landing, with the very fine sand-size fraction populated by euhedral dolomite. Heavy bioturbation may account for the dissolution of calcareous foraminifers.