April 15, 2026 | 1:30 – 2:30pm
Alexandra Dawson Lawrence
Master’s Thesis Defense
Ocean Engineering
Wednesday, April 15, 2026, 1:30 p.m.
Chase 130
Abstract
Modern hydrographic surveys can reveal paleolandscapes on the continental shelf that have remained preserved since their inundation by post-glacial sea level rise following the Last Glacial Maximum ~20,000 years ago. This study investigates a submerged paleolandscape preserved on the continental shelf east of Frying Pan Shoals in Onslow Bay, North Carolina by utilizing modern high-resolution multibeam bathymetry ranging from 16 cm to 4 m resolution, 4 m resolution acoustic backscatter, surficial bottom samples, and interpreted core and seismic stratigraphy, and ICE-6G_C glacial isostatic adjustment (GIA) models. The high-resolution bathymetry reveals geomorphological features such as a continuous, elongated escarpment, paleochannels, exposed bedrock, fractures, bedding, scours, and modern sand waves. Backscatter characterization and bottom samples indicate the preserved geomorphologic features are associated primarily with coarse shell-rich quartz sand, gravel, and exposed or near-exposed bedrock. Comparison with GIA-modeled shorelines shows that the continuous, elongated escarpment most closely aligns with the 8,500-cal yr BP model, supporting its interpretation as a preserved paleoshoreline that defines the final subaerially exposed surface immediately prior to rapid sea level rise. This study also delineates paleoshorelines at 9,000 cal yr BP and 9,500 cal yr BP, which correspond to geomorphic features in the study area, allowing us to constrain these relict features in time. Collectively, delineation of these features reveals a well-preserved, karst-controlled coastal plain paleolandscape developed in limestone and sandstone bedrock, including preserved shorelines, complex meandering paleochannel networks, and numerous depressions interpreted as former ponds, lakes or bays. This study provides a paleogeomorphologic reconstruction of a relict coastal plain landscape on the North Carolina continental shelf, with broader implications for critical habitat mapping, assessing sand resources, and identifying areas of archaeological importance.
Bio
Alexandra (Alex) Dawson Lawrence is a Physical Scientist and Hydrographic Surveys Project Manager for the NOAA Office of Coast Survey’s Hydrographic Surveys Division. Alex obtained her Bachelor of Science in Geology from the College of Charleston in 2018 and was a proud member of the BEAMS Program (BEnthic Acoustic Mapping and Survey) for three years under the leadership of Dr. Leslie Sautter. Alex prioritizes, plans, and manages Office of Coast Survey-led hydrographic survey projects using in-house and contracted survey platforms. She critically evaluates the nation’s seafloor mapping needs and applies the necessary hydrographic survey specifications, requirements, and resources to update NOAA nautical charting products and ensure safe maritime navigation within the United States Exclusive Economic Zone (EEZ). In 2023, Alex discovered a paleochannel off the coast of Wilmington, North Carolina which was once above sea level during the Last Glacial Maximum. She hypothesizes that the Wilmington paleochannel may be ancient remnants of North Carolina’s Cape Fear river, which has remained perfectly preserved due to the barrier wall nature of Frying Pan Shoals. To learn more about the newly discovered ancient paleochannel, please visit: https://nauticalcharts.noaa.gov/updates/possible-ancient-river-system-discovered-off-wilmington-north-carolina/
Alex began pursuing her Masters in Earth Sciences: Ocean Mapping in August 2024 and looks forward to furthering her career as a woman in STEM. In her free time, Alex is working on co-hosting a podcast that highlights professionals within various careers in ocean science.
Underwater Archaeology and Maritime History jobs 