Short-term sediment dispersal on a large retreating coastal river delta via 234Th and 7Be sediment geochronology: The Mississippi River Delta Front

Andrew Courtois; Samuel J. Bentley; Jillian Maloney; Kehui Xu; Jason Chaytor; Ioannis Y. Georgiou; Michael Miner; Jeffery Obelcz; Navid H. Jafari; Melanie Damour

doi:10.3390/w16030463

Short-term sediment dispersal on a large retreating coastal river delta via ²³⁴Th and ⁷Be sediment geochronology: The Mississippi River Delta Front

Water

By: Andrew Courtois, Samuel J. Bentley, Jillian Maloney, Kehui Xu, Jason Chaytor, Ioannis Y. Georgiou, Michael Miner, Jeffery Obelcz, Navid H. Jafari, and Melanie Damour

https://doi.org/10.3390/w16030463

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Abstract

Many Mississippi River Delta studies have shown recent declines in fluvial sediment load from the river and associated land loss. In contrast, recent sedimentary processes on the subaqueous delta are less documented. To help address this knowledge gap, multicores were collected offshore from the three main river outlets at water depths of 25–280 m in June 2017 just after the peak river discharge period, with locations selected based on 2017 U.S. Geological Survey seabed mapping. The coring locations included the undisturbed upper foreset, mudflow lobes, gullies, and the undisturbed prodelta. Nine multicores were analyzed for Beryllium-7 activity, and four cores were analyzed for excess Thorium-234 activity via gamma spectrometry, granulometry and X-radiography. Our results indicate a general trend of declining ⁷Be and ²³⁴Th activities and inventories with increasing distance from sources and in deeper water. The core X-radiographs are graded from the predominantly physically stratified nearshore to the more bioturbated offshore, consistent with the sedimentation patterns. Sediment focusing assessed via the ⁷Be and ²³⁴Th sediment inventories shows preferential sedimentation in gully and lobe environments, whereas the upper foreset and prodelta focusing factors are relatively depleted. Overall, short-term sediment deposition from the main fluvial source remains active offshore from all three major river outlets, despite the overall declining river load.

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Additional publication details
Publication type	Article
Publication Subtype	Journal Article
Title	Short-term sediment dispersal on a large retreating coastal river delta via 234Th and 7Be sediment geochronology: The Mississippi River Delta Front
Series title	Water
DOI	10.3390/w16030463
Volume	16
Issue	3
Year Published	2024
Language	English
Publisher	MDPI
Contributing office(s)	Woods Hole Coastal and Marine Science Center
Description	463, 18 p.
Country	United States
State	Louisiana
Other Geospatial	Mississippi River Delta Front
Google Analytic Metrics	Metrics page