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LATE PLEISTOCENE PALEOENVIRONMENTAL CHANGES IN THE LOWER NEUSE RIVER BASIN, NORTH CAROLINA, AND IMPLICATIONS FOR RELATIVE SEA LEVEL AND COASTAL EVOLUTION

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August 2024

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2025-02-01

Authors

King, Jessica Lynn

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East Carolina University

Abstract

The coastal plain of eastern North Carolina evolved through the changes associated with late Pleistocene rapid relative sea-level oscillations during Marine Isotope Stages 5 to 2. The sea-level highstand deposits of MIS 5 and MIS 3 have been previously studied in eastern North Carolina; however, certain regions have had little to no data collected, which makes determining the areal extent of facies and associated depositional environments challenging. To overcome these limitations and better understand the spatial and temporal variation of sea-level fluctuations, geophysical and geological data from the lower Neuse River Basin have been analyzed. These data reveal the presence of multiple paleoenvironments with distinctive sequences corresponding to MIS 5e, MIS 5a, and MIS 4. The chronological framework, determined using optically stimulated luminescence dating, provides sediment age estimates ranging from 123.5 (± 7.2) ka to > 56.8 (± 4.1) ka. DS-5e is composed of eastward thickening shelly sand lithofacies. This sequence contains two distinct foraminiferal assemblages. Samples dominated by Elphidium excavatum, Ammonia parkinsoniana, and Elphidium mexicanum are overlain by samples also containing Buccella inusitata, Nonionella atlantica, and Rosalina sp. Additionally, pollen samples collected within DS-5e show a trend of cooler conditions in the lowermost sample of the core to likely warmer than modern conditions in the uppermost collected sample. This transition from low to higher diversity foraminifera assemblages, warming climate conditions, and shelly marine deposits is indicative of a transgressive environment, interpreted as a high salinity estuary becoming an inner shelf environment. DS-5a is characterized by burrowed laminated sand, as well as sandy mud and is barren of foraminifera, with the exception of one sample. Lithofacies show an upward-fining succession transitioning from flaser to wavy tidal bedding. One pollen sample from DS-5a suggests conditions ranging from modern to slightly warmer than present. With apparent tidal bedding, the absence of foraminifera, and warm climate conditions DS-5a is potentially indicative of coastal tidal flat deposits. The lithofacies of DS-4 are characterized by medium to fine-grained burrowed laminated sand and sandy mud, with all samples being barren of foraminifera. Regression during MIS 4 likely exposed sediment from a shallow marine shoal in cores south of the river, where aeolian forces likely reworked the sand into dunes. Comparing these facies across the Neuse River Basin with similar studies in the region offers valuable insights into how coastal North Carolina's geomorphology responded to changes in relative sea-level during the late Pleistocene.

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