PALEO-INLET DYNAMICS OF OLD CURRITUCK INLET, VIRGINIA/NORTH CAROLINA

Old Currituck Inlet marked the original state boundary between Virginia and North Carolina along the Outer Banks. Already open in 1585 at the time of the first coastal surveys, Old Currituck Inlet breached Currituck Spit in the northern Outer Banks ~80km north of Oregon Inlet and closed in 1731. In addition to well-documented historical records and maps, geomorphic features including a relict flood tidal delta and relict beach ridges mark the position of the former inlet, and benthic foraminiferal assemblages present in the flood tidal delta sediments verify the position of this former inlet. Building on this previous research, we interpret paleo-inlet dynamics through comparison of the flood tidal delta stratigraphy with foraminiferal assemblage variability.

Six vibracores collected from the relict flood tidal delta of Old Currituck Inlet were opened, described, and sampled at ~25cm intervals for micropaleontological analysis. Benthic foraminiferal assemblage groups reveal four environments of deposition from bottom to top: estuary, flood tidal delta, medium salinity marsh, and low salinity marsh. The boundaries associated with these successive environments are related to Old Currituck Inlet's paleo-inlet activity, but these environmental divisions are not necessarily coincidental with sedimentary boundaries. Four sedimentary boundaries characterize the flood tidal delta deposits: quiescent estuary, active flood tidal delta, abandoned flood tidal delta/washover flat/tidal flat, and marsh. The contact between the estuarine muds and the flood tidal delta sand lags behind the change between estuarine and flood tidal delta foraminiferal assemblages in the southernmost cores and therefore records not only Old Currituck Inlet's initial breach of the spit, but also its southern migration. The remaining sedimentary boundaries show similar relationships to the corresponding environmental boundaries and allow for interpretations of the inlet migration rate and rate of eventual inlet shoaling.

The paleo-inlet dynamics of Old Currituck Inlet (opening, migration and shoaling) are recorded in its flood tidal delta sediments. The combination of micropaleontologic and sedimentologic analyses allows for interpretations of paleo-inlet dynamics not available through a single discipline.