UPPER CRETACEOUS BENTHIC FORAMINIFERA FROM THE DIXON CORE, SOUTHEASTERN, NC

Fifty-eight samples of upper Santonian to upper Maastrichtian sediments from the Cape Fear, Middendorf, Black Creek, and the Peedee formations were washed, wet sieved and picked for benthic and planktonic foraminifera. Three hundred fifty to 450 foraminifers were picked from at least 35 samples. A preservation index based on frequency of foraminifers and ratio of whole to broken specimens indicates that sixteen samples were barren or contain very poorly preserved foraminifers, of which 50% were from Santonian strata. Low frequency and poor preservation also seems to correlate with late highstand systems tracts or nearshore-fluvial sediments typical of the Cape Fear and Middendorf formations. Generally, preservation was better for planktonic species than benthic, perhaps indicating more intense predation of benthic species. Benthic taxa include 123 species, five of which constitute 40.1% of all picked specimens: Cibicides harperi (9.0%), C. coonensis (8.7%), C. beaumontianus (5.6%), Gyroidinoides imitata (8.9%), and Planulina correcta (8.0%). Species abundance data was analyzed using Q-mode cluster and principal components analyses (PCA) with SPSS software. Cluster analysis shows three distinct clusters, Cluster I in the early Campanian (CC18-CC19), Cluster II straddling the Campanian-Maastrichtian boundary (CC22c-CC24), and Cluster III late Maastrichtian (CC25b-CC26a). Cluster I includes abundant Gyroidinoides and Bolivinids indicating deep upper slope environments. Cluster II contains abundant coiling species (Cibicides, Planulina) with few Gyroidinoides, and higher renewal rates suggesting a middle to outer shelf environment. Cluster III represents middle to outer shelf assemblages again dominated by Gyroidinoides. Samples in Cluster III show upsection increases in abundance and size of G. imitata and increasing P/B ratios suggesting transgression up to the K/P boundary unconformity. Principal components analysis indicates 65% of the total variance within the data can be explained by the first six components. Examination and use of benthic foraminifera as paleoenvironmental indicators correlates well with the proposed sequence stratigraphy .