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 km2 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.
Similar content being viewed by others
Paleo-climatic control on recharge and fresh-salt groundwater distribution in the Red River delta plain, Vietnam
Buried deep freshwater reserves beneath salinity-stressed coastal Bangladesh
Geophysical assessment of seawater intrusion in Apapa-Ajegunle, coastal area of Lagos, Southwestern Nigeria
Acknowledgements
Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. We thank Carol Finn and Dan Doctor for their input on the development of this manuscript, and four anonymous reviewers who helped to improve its quality.
Funding
This study was supported by the USGS Delaware River Basin Next Generation Water Observing System (NGWOS) project for work in the Delaware Bay region, and the USGS Mississippi Alluvial Plain (MAP) regional water availability project data collection and studies of coastal Louisiana.
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Competing interests
The authors declare no competing interests.
Additional information
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary information
Supplementary Information (download PDF )
Transparent Peer Review File (download PDF )
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
Reprints and permissions
About this article
Cite this article
Minsley, B.J., Michael, H.A., Lindaman, M.A. et al. The saline groundwater legacy of a large buried coastal paleo-estuary.
Nat Commun (2026). https://doi.org/10.1038/s41467-026-76005-5
Received:
Accepted:
Published:
DOI: https://doi.org/10.1038/s41467-026-76005-5
Source: Resources - nature.com
