FORAMINIFERAL ASSEMBLAGE CHARACTERISTICS IN HOLOCENE SHOREFACE AND SHELF FACIES OF BOGUE BANKS, NC

Foraminifera are often used to interpret paleoenvironments based upon changes in down-core assemblages. However, it is not known whether foraminiferal assemblages from several discrete coastal subenvironments, characterized by similar lithologies, differ. This study uses Holocene foraminiferal data to analyze differences in foraminiferal assemblages from shoreface and shelf cores. A set of 200 vibracores were collected in 2011 offshore of Bogue Banks and in Bogue Inlet, North Carolina in an effort to assess offshore sand resources. Four cores were selected based on their location and presence of Holocene sands. Three cores were selected from the inner shelf and one from the shoreface. Cores were logged graphically, using a method independent from composition, and sampled from all units (varying from siliciclastic, through mixed, to bioclastic) in the cores. Samples were soaked in a sodium hydroxide and sodium hexametaphosphate solution to help separate organic materials from fine sediments and then washed over nested 710 and 63 micron sieves to remove coarse sand, gravel and mud. Samples were then floated in sodium polytungstate to concentrate foraminifera. About 100 foraminifera were picked from each sample.

The shoreface core (Y126) was characterized by fine to medium sand; foraminiferal assemblages (5 samples) averaged 75% Rotaliina, 23% Miliolina, and 2% Textulariina. One shelf core (Y88), dominated by fine to medium sand, averaged 81% Rotaliina, 15% Miliolina, and 4% Textulariina (2 samples). Two shelf cores (Y86 and Y154), dominated by coarse sand, averaged 61% Rotaliina, 36% Miliolina and 2% Textulariina (3 samples). Preliminary results indicate that foraminiferal assemblages of inner shelf sediments vary with lithology and shoreface assemblages (in fine to medium sand) differ from those of both coarse and fine to medium sand inner shelf assemblages.