THE EFFECTS OF HURRICANES ON THE SEDIMENTOLOGIC AND FORAMINFERAL CHARACTERISTICS OF BARRIER ISLAND SUBENVIRONMENTS: BEAR ISLAND, NORTH CAROLINA

Using an actualistic approach, the characteristics of lithofacies and foraminiferal biofacies help to define depositional environments that are recognizable in the stratigraphic record. For example, foraminifera derived from Oligo-Miocene strata exposed on the modern continental shelf off South Carolina have been used to recognize tropical storm deposits in subenvironments of the modern barrier island coast. However, little is known of the stratigraphic record formed by closely spaced storms in sand-dominated barrier island subenvironments and the “recovery” of foraminiferal assemblages during the longer inter-storm periods.

Bear Island, part of eastern North Carolina’s Hammocks Beach State Park, is an undeveloped and “pristine” barrier island system. A suite of sediment samples was collected from 26 subenvironments on and around (i.e., in an inlet and offshore) Bear Island in spring, summer, and fall of 2016. The island had not been impacted by hurricanes for several years prior to collection. Four (composite) major depositional environments were defined by their foraminiferal assemblages: a) shoreface; b) ebb-tide delta; c) flood-tide delta and inlet channel; d) foreshore, dune, overwash, spit, longshore bar and trough. In September 2018, Hurricane Florence made landfall, approximately 50 km south of Bear Island with sustained winds of 50 to 90 mph and a storm surge of approximately 2 m along the shoreline. Significant erosion occurred on the ocean shoreline of Bear Island, with more than 40 m of shoreline recession in many places. Eighteen stations from the 2016 study were resampled for foraminifera and sediments within two months. In September 2019, Hurricane Dorian made landfall approximately 160 km north of Bear Island with sustained winds near 90 mph. Bear Island was affected by storm-driven waves but to a lesser degree than in 2018. The 18 stations were sampled once more within two months.

This study investigates the change in foraminiferal assemblages and sedimentological characteristics within the four major subenvironments around Bear Island, following Hurricanes Florence and Dorian. The investigation advances our understanding of the immediate and longer-term impacts of intense storms on barrier island coastal systems and the ability to recognize these events in the stratigraphic record.