32 Hydrogeology

Added due to amount of discipline abstracts submitted.

Tuesday, 10 March 2026
1:30 PM - 5:30 PM
RCC, 106

Geophysical Evidence for Structural Influences on Saltwater Intrusion in Coastal Barrier Island Aquifers: Evidence from St. Catherines Island, Georgia

Paper number: 32-14
Program: Technical Sessions
Time: 5:00 PM – 5:15 PM

Authors

Abstract

Saltwater intrusion events affect the surficial aquifer system of St. Catherines Island, Georgia; however, limited subsurface and stratigraphic data have hindered understanding of the shallow groundwater processes that influence intrusion in this barrier island setting. To address this knowledge gap, we conducted electrical resistivity tomography (ERT) and ground-penetrating radar (GPR) surveys to noninvasively characterize the island’s shallow subsurface (approximately 20–40 m depth) near locations with known saltwater intrusion. Geophysical results, constrained by sediment cores, reveal laterally and vertically heterogeneous subsurface conditions, including structural features that may influence groundwater flow and salinity distribution. At one site with pronounced saltwater intrusion, ERT and GPR data indicate the presence of fractures and fault-like features that could facilitate vertical and lateral saltwater migration. At a second site, a shallow sag structure is identified within the subsurface stratigraphy and coincides with observed intrusion, suggesting localized structural control on groundwater pathways. Our results demonstrate that subtle structural heterogeneities within shallow coastal sediments can exert a strong influence on saltwater intrusion dynamics. We propose that such features may be more widespread along the Georgia coast than currently recognized and may need to be considered in models of barrier island hydrostratigraphy, groundwater vulnerability, and coastal aquifer management.

Geological Society of America Abstracts with Programs. Vol. 58, No. 1

doi: 10.1130/abs/2026SE-411747

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