Paper No. 378-10
Presentation Time: 9:00 AM-6:30 PM
MODERN AND FOSSIL FORAMINIFERAL ASSEMBLAGES OF ONSHORE AND OFFSHORE SUBENVIRONMENTS FROM BEAR ISLAND AND BOGUE BANKS, NORTH CAROLINA, USA
Foraminifera are important and commonly used paleoenvironmental indicators. However, knowledge gaps exist regarding the use of foraminifera as indicators of discrete coastal siliciclastic subenvironments in barrier island settings. Lithologic characteristics, while used to distinguish broadly-defined coastal environments in the stratigraphic record, cannot easily differentiate specific nearshore subenvironments (e.g., dune, overwash, tidal delta, foreshore, longshore bar, and trough). This study addresses this problem by characterizing modern foraminiferal assemblages and lithologies of 26 subenvironments ranging from dunes to the shoreface and foreshore, to flood- and ebb-tide delta complexes. Hammocks Beach State Park (Bear Island, NC) was chosen for its general lack of human interference on modern sediments. Foraminiferal assemblages and grain size statistics of replicate surface sediments, as well as seismic data of offshore environments, were collected for each subenvironment in order to establish a modern foraminiferal dataset. Preliminary results are as follows: 1) sediments from all twenty-six subenvironments plot within fine to medium sand (73% 2-3ϕ, 26% 1.5-2ϕ, <1% 3-3.5ϕ); 2) the upper foreshore has a higher percentage of fossil foraminifera (likely derived from inner shelf seabed outcrops of Miocene deposits) than the lower foreshore; 3) Abundant modern foraminiferal species include Elphidium excavatum (dominant in all environments), Quinqueloculina lamarckiana (dominant in landward inlet channel, ebb-tide delta, and lower shoreface), Ammonia tepida (dominant in intertidal sandy mud flat), Eponides repandus (higher abundance in main inlet and flood-tide delta channels), Ammonia parkinsoniana (higher abundance in dune, trough, and longshore bar). These modern foraminiferal and sedimentological data are being used a priori to test the ability to differentiate coastal subenvironments in Holocene sediments from cores collected offshore of Bogue Banks.