BURIED SOILS AS STRATIGRAPHIC MARKER HORIZONS ON THE CAPE FEAR RIVER FLOODPLAIN, BLADEN COUNTY, NORTH CAROLINA

Over the past 40 years, studies have shown that presettlement soils can be used to determine historical deposition rates in river systems across North America. Previous studies in the Coastal Plain of the Southeastern USA have not been cited, and it is unclear whether they are not present or have not been identified due to several factors. First, poor drainage causes soil-forming conditions, such as bioturbation and redoximorphic features, mask the appearance of buried soils in swampy river floodplains of the Coastal Plain. Second, deposition rates on the Coastal Plain are generally low, relative to the rates of pedogenesis and bioturbation. Third, the long colonial history of the southeast means that the postsettlement stratigraphic record in floodplains is older and more complex than elsewhere in the US, due to lower deposition rates over long periods of time.

The purpose of this study is to show that a presettlement soil is present and can be used as a stratigraphic marker horizon to determine deposition rates on the Cape Fear River Floodplain, Bladen County, North Carolina. Buried soils were identified by careful field description, supported by organic carbon determination. Radiocarbon dates suggest an age of approximately A.D. 1620, with a vertical accretion rate of approximately 2.7mm/yr since its burial. Our initial Cesium-137 results suggest a floodplain deposition rate of approximately 1.7-2.8mm/yr since 1954.