Numerical model of geochronological tracers for deposition and reworking applied to the Mississippi subaqueous delta

Journal of Coastal Research
By: , and 

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Abstract

Measurements of naturally occurring, short-lived radioisotopes from sediment cores on the Mississippi subaqueous delta have been used to infer event bed characteristics such as depositional thicknesses and accumulation rates. Specifically, the presence of Beryllium-7 (7Be) indicates recent riverine-derived terrestrial sediment deposition; while Thorium-234 (234Th) provides evidence of recent suspension in marine waters. Sediment transport models typically represent coastal flood and storm deposition via estimated grain size patterns and deposit thicknesses, however, and do not directly calculate radioisotope activities and profiles, which leads to a disconnect between the numerical model and field observations. Here, observed radioisotopic profiles from the Mississippi subaqueous delta cores were directly related to a numerical model that represented resuspension and deposition using a new approach to account for the behavior of short-lived radioisotopes. Appropriate selection of parameters such as the biodiffusion coefficient, sediment accumulation rate, and radioisotopic source terms enabled a good match between the modeled and observed cores. Comparisons of modelled profiles with geochronological analytical models that estimate accumulation rate and flood layer thickness revealed potential avenues for refining these tools, and highlight the importance of constraining the biodiffusion coefficient.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Numerical model of geochronological tracers for deposition and reworking applied to the Mississippi subaqueous delta
Series title Journal of Coastal Research
DOI 10.2112/SI85-092.1
Volume Special Issue 85
Year Published 2018
Language English
Publisher Coastal Education and Research Foundation
Contributing office(s) St. Petersburg Coastal and Marine Science Center
Description 5 p.
First page 456
Last page 460
Country United States
Other Geospatial Gulf of Mexico, Mississippi River Delta