2-10 Integrating Borehole Water Quality and Airborne Geophysics with Machine Learning to Map Modern and Paleo-Saltwater in the Lower Mississippi-Gulf Region

Session: Coastal Hydrogeology in an Age of Rising Seas

Presenting Author:

Authors:

Abstract:

The Cenozoic sediments of the Lower Mississippi-Gulf (LMG) region host the Mississippi embayment aquifer system (MEAS), the coastal lowlands aquifer system (CLAS), and the Mississippi River Valley alluvial aquifer (MRVA). These aquifer systems provide vital groundwater resources to the region, supporting several billion gallons per day of fresh groundwater for agriculture, industry and public supply from depths up to 1 km. However, many salinization issues have been reported for different aquifers, including modern seawater intrusion in the coastal zone of the northern Gulf of Mexico and paleo-saltwater intrusion in the Tertiary aquifers, where the Mississippi Embayment was once a paleo coastal line. This study presents an integrated framework to delineate modern and paleo-saltwater distributions for the LMG region. We first apply horizon restoration and indicator kriging techniques to ~157,000 driller’s logs and 8,400 electrical logs to construct a 3-D hydrostratigraphic model of 14 hydrogeologic units. Moreover, we utilize USGS airborne electromagnetic (AEM) surveys in 2020 and 2022 to develop a regional-scale 3-D electrical resistivity model. By intersecting the two models, low resistivity values in aquifers likely indicate saline groundwater. A deep learning artificial neural network (DLANN) model is then trained and validated using borehole chloride data and corresponding AEM resistivity values. Finally, the DLANN model is used to delineate saltwater plumes for different aquifers. Results reveal significant paleo-saltwater in the Middle Claiborne aquifer (Eocene), the Chicot aquifer (Pleistocene) and the MRVA (Quaternary). Moreover, pronounced modern seawater intrusion is observed in the Holocene-age Mississippi River Deltaic Plain and Chenier Plain adjacent to the Gulf.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9583

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