Holocene Stratigraphy and Paleoenvironmental Change of Pamlico Sound, North Carolina, USA

ECU Author/Contributor (non-ECU co-authors, if there are any, appear on document)

Nicholas Zaremba (Creator)

Institution

East Carolina University (ECU )

Web Site: http://www.ecu.edu/lib/

Abstract: Understanding how coastal systems respond to changes in climate is becoming more important due to the current increased rate of sea-level rise and possible increased hurricane intensity in the future. While coastal ecosystems represent only 10% of Earth's surface, more than 20% of the world's population resides within 100 km of the coastline and within 100 m of sea level, which highlights the need to understand the past effects of sea-level rise and climate change on barrier island systems. In North Carolina, USA the barrier island system in the northern portion of the state (the Outer Banks) extends for ca. 270 km of the state's coast and provides a dynamic boundary between the ocean and two large estuarine water bodies, Albemarle and Pamlico Sound. This study expands upon previous work which identified two periods of increased marine influence within Pamlico Sound interpreted to be the result of extensive barrier island segmentation synchronous with periods of rapid climate change (RCC) during the late Holocene. Approximately 470 km of high resolution geophysical data, 850 bulk sediment magnetic susceptibility sediment samples and ca. 600 sediment analyses were constrained by 108 radiocarbon age estimates derived from 52 vibracores to better understand the Holocene stratigraphy of Pamlico Sound and how the periods of RCC affected the stratigraphic architecture of the Sound. According to previous work, estuarine waters prevailed within the paleovalleys of Pamlico Sound as early as ca. 7500 cal BP and Pleistocene interfluves provided protection for the paleovalleys from the Atlantic Ocean until ca. 5500 cal BP, when the interfluves were flooded by rising sea-level, this interpretation is based on a conservative sea-level rise. However, the data provided in this study indicates that there is no evidence of a change in depositional environment at ca. 5500 cal BP. If the 5500 cal BP flooding of the Pleistocene interfluves is accurate, then Holocene barrier islands must have been present to explain the presence of estuarine deposits within the paleovalleys. At ca. 4000 cal BP, an increase in marine influence and sand content is detected in multiple cores within the northern basin and is interpreted to be the result of increased segmentation of barrier islands. This deposit is mainly recorded within the paleovalleys of Pamlico Sound\; and is only preserved on a few interfluves as a result of base level being too low. Reformation of the barrier islands occurred sometime from 3500 to 2500 cal BP\; suggested by muddy deposits with low brackish estuarine foraminiferal assemblages. At ca. 1200 cal BP, a sudden increase in marine influence is detected throughout southeastern Pamlico Sound\; a sandy deposit is interpreted to be the result of extensive segmentation of the barrier islands during the Medieval Climate Anomaly (MCA). Geophysical data suggests the segmentation of the barriers was large in magnitude to allow for deposition of large lobate shoals (the MCA shoals). Further refinement of a local sea-level curve is required to understand the mechanisms responsible for the 4000 cal BP marine influenced deposit. The error range of the North Carolina sea-level curve loosely constrain the initial flooding of the Pleistocene interfluves anytime from 5500 to 4000 cal BP rather than before 7000 cal BP as previously postulated. Therefore, it is difficult to hypothesize about the mechanism responsible for the 4000 cal BP sandy deposit without a more refined local sea level curve. However, data from this study combined with other research suggest that the 1200 cal BP deposit was likely caused by an increase in hurricane activity or intensity during the MCA. Furthermore this study has provided an estimate on the volume (1.1x10? km³) of silt and clay deposited within the northern basin of Pamlico Sound since ca. 4000 cal BP\; this has aided in creating a carbon sequestration budget for the system.

Additional Information

Publication

Thesis

Language: English

Date: 2023

Subjects

Geology;Sedimentary geology;Holocene stratigraphy;Little Ice Age;Medieval climate anomaly;Outer Banks (N.C.);Rapid climate change

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