Underlying Paleochannels Facilitate Barrier Progradation: Bogue Banks, North Carolina

Areas of the Outer Banks that were progradational during the Holocene spatially correlate with underlying channel forms. This is especially evident along Bogue Banks, North Carolina. Here, two different types of barrier island geomorphology are observed. Pine Knoll shores and Emerald Isle are the widest sections of the barrier, ranging from around 0.9-1.3 km in width. In both areas ridge and swale topography is observed which indicates progradation. Indian Beach, which lies between these areas of progradation does not exhibit ridge and swale topography and is the thinnest section of the island at around 0.2-0.4 km in width. Ground penetrating radar data were collected along transects of the barrier in these three locations. Both Pine Knoll shores and Emerald Isle exhibit seaward-dipping reflectors, which indicate seaward accretion of the barrier. Indian Beach shows reflectors that accrete vertically, indicating this section of the island to be aggradational. Seismic data taken in the sound behind Bogue Banks and offshore of Pine Knoll shores corroborates the presence and spatial correlation of paleochannels to the progradational areas. Sediment from these paleochannels was likely reworked as sea level rose throughout the mid Holocene, allowing for the creation of a progradational sequence due to the abundant sediment source that the channel provided. This could be a possible explanation for the progradational sequences in Pine Knoll shores and Emerald Isle, versus the aggradational area that is evident in Indian Beach where underlying paleochannels are not found. Currently, many areas of the Outer Banks that show a Holocene episode of progradation are erosional hotspots. Future efforts will examine the cause of this transition.