RECONSTRUCTION OF RECENT PALEOENVIRONMENTS OF PAMLICO SOUND, NORTH CAROLINA, USING FORAMINIFERA, STABLE ISOTOPES d13C AND d15N, AND SEDIMENTATION RATES

Pamlico Sound is a large estuarine embayment on the U.S. Atlantic Coast, separated from the ocean by a series of barrier islands (the Outer Banks). Currently, three inlets, two rivers, and outflow from the Albemarle Sound (located to the north) directly affect environmental conditions of the sound. This project documents the foraminiferal assemblages of the entire Sound. Previous work by Grossman and Benson (1967) mapped the surficial benthic foraminifera only in southern Pamlico Sound.

Three major foraminiferal assemblages characterize the Sound; (1) coarsely agglutinated foraminifera, (2) finely agglutinated foraminifera, and (3) calcareous foraminifera. These taxonomically distinct assemblages represent estuarine, marsh, and estuarine (but adjacent to inlet) environments, respectively. Each assemblage can be further divided into two or three groups representing subenvironments.

The modern distribution of foraminifera can be used to interpret paleoenvironmental conditions indicated by foraminiferal assemblages found downcore, as can geochemical data. Seventeen push cores (up to 50 cm deep) have been collected throughout the embayment. Stable isotopes (d¹³C and d¹⁵N) and C/N ratios obtained from these cores indicate sources of organic matter and biogeochemical processes. The age of paleoenvironmental changes and sedimentation rates were determined using radionuclides (Pb-210 and Cs-137).

Two time slices have been examined downcore, (1) at the depth representing 120yrs or slightly older and (2) at the depth representing the early 1960’s, as determined by the absence of excess Pb-210 activity and the Cs-137 peak activity peak from atmospheric nuclear testing, respectively. The combined results of the foraminiferal assemblages and carbon and nitrogen data serve as an indication of environmental change within the greater estuarine system of Pamlico Sound over the last 120 years.