USING FORAMINIFERAL ASSEMBLAGES TO IDENTIFY HOLOCENE MARINE SUBENVIRONMENTS OF BOGUE INLET, NORTH CAROLINA

Foraminiferal assemblages are widely used by paleontologists to determine paleoenvironments, but identifying subenvironments such as ebb tide delta, inner shelf, and shoreface using foraminifera is problematic. In 2011, 200 vibracores were collected off of Bogue Banks, NC to find sand sources. Four cores were chosen for study, two from the inlet channel and two from the ebb tide delta. The cores were logged using a method that is dependent on grain size rather than composition. Samples were taken from all units throughout the cores and washed in a sodium hydroxide and sodium hexametaphosphate solution to help disaggregation. Samples were then washed over nested 710 and 63 micron sieves to remove coarse sand, gravel and mud. A sodium polytungstate heavy liquid was used to separate the quartz sand from foraminifera to aid the picking process. At least 100 foraminifera were picked from each sample.

Two inlet channel cores, one dominated by fine to medium sand and the other by coarse sand, contained similar assemblages averaging 66% Rotaliina, 33% Miliolina, and <1% Textulariina (n=4). Two cores from the ebb tide delta were dominated by fine to medium sand and contained variable assemblages averaging 79% Rotaliina, 20% Miliolina, and 1% Textulariina (n=10). Preliminary results indicate that the higher values for rotaliids in ebb tide delta sediments suggest that foraminiferal assemblages may be used to distinguish between inlet channel and ebb tide delta environments.