PALEO-INLET DYNAMICS RECORDED BY FORAMINIFERA: OLD CURRITUCK INLET, VA/NC

Old Currituck Inlet is one of several inlets to breach the northern-most segment of the Outer Banks and then close. Old Currituck Inlet, however, is important historically because it served as the original state boundary between Virginia and North Carolina. As such, its existence and position are well-documented in historical records. A geomorphic indication of its location exists as a well-developed relict flood tidal delta protruding into Knotts Island Bay, VA/NC.

We collected six vibracores from the abandoned flood tidal delta and examined their stratigraphy and microfossil assemblages. The benthic foraminifera contained within these cores record a history of pre-inlet, active inlet and post-inlet dynamics, including the breaching, migration and shoaling of Old Currituck Inlet.

These cores record four periods in the history of Knotts Island Bay, each separated by distinct changes in inlet dynamics. Initially, we observe a quiescent freshwater estuary, containing few foraminifera with the exception of Elphidium that appears only in occasional thin sand layers. Secondly, we interpret a period of active subtidal flood tidal delta development in assemblages dominated by Elphidium, but also containing other calcareous genera (e.g., Hanzawaia, Planulina and Quinqueloculina) that typically inhabit regions of normal ocean salinity. Thirdly, a periodically active, intertidal zone associated with inlet shoaling is indicated. Foraminifera are absent in most of these samples that are composed of thick, bioturbated layers of coarse quartz sand separated by thin marsh deposits. Finally, we observe a low-salinity estuary and marsh, containing only agglutinated species (e.g., Jadammina macrescens, Trochammina inflata and Milliammina fusca) that occur today in marshes.

We conclude that this pattern of changing foraminiferal assemblages relates the dynamic history of this former inlet, and further, that foraminiferal assemblages collected elsewhere along a barrier island system would indicate the presence or absence of a former tidal inlet.