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The saline groundwater legacy of a large buried coastal paleo-estuary

Burke J. Minsley·Holly A. Michael·Maxwell A. Lindaman·Lyndsay B. Ball·Stephanie R. James·James R. Rigby·Wade H. Kress·Frank T.C. Tsai·Bennett Eugene Hoogenboom
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Abstract

Elevated groundwater salinity in coastal regions threatens the beneficial use of fresh groundwater. Coastal groundwater management typically focuses on preventing intrusion from modern sources of seawater; however, past geological processes can also leave a legacy of saline groundwater now hidden in the subsurface. Here, multiple extensive airborne electromagnetic surveys provide detailed evidence of residual salinity from a paleo-estuary filling a late Pleistocene incised valley impacting more than 10,000 km 2 that is now hidden beneath coastal Louisiana’s deltaic plain. Our results show that the three-dimensional pattern of saline groundwater beneath Louisiana mimics that of near-surface aquifers surrounding the modern Delaware Bay estuary, fingerprinting the signature of the past drowning of a large, incised valley of the Mississippi River following post-glacial sea-level rise. These findings demonstrate a new framework for understanding legacy sources of saltwater critical for managing stressed water resources along global coastlines.

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Burke J. Minsley, Holly A. Michael, Maxwell A. Lindaman, Lyndsay B. Ball, Stephanie R. James, James R. Rigby, Wade H. Kress, Frank T.C. Tsai, Bennett Eugene Hoogenboom. 2026-07-27. The saline groundwater legacy of a large buried coastal paleo-estuary. https://doi.org/10.1038/s41467-026-76005-5

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