Virginia Institute of Marine Science
Journal of Marine Science
Geochronologies derived from sediment cores in coastal locations are often used to infer event bed characteristics such as deposit thicknesses and accumulation rates. Such studies commonly use naturally occurring, short-lived radioisotopes, such as Beryllium-7 (Be-7) and Thorium-234 (Th-234), to study depositional and post-depositional processes. These radioisotope activities, however, are not generally represented in sediment transport models that characterize coastal flood and storm deposition with grain size patterns and deposit thicknesses. We modified the Community Sediment Transport Modeling System (CSTMS) to account for reactive tracers and used this capability to represent the behavior of these short-lived radioisotopes on the sediment bed. This paper describes the model and presents results from a set of idealized, one-dimensional (vertical) test cases. The model configuration represented fluvial deposition followed by periods of episodic storm resuspension. Sensitivity tests explored the influence on seabed radioisotope profiles by the intensities of bioturbation and wave resuspension and the thickness of fluvial deposits. The intensity of biodiffusion affected the persistence of fluvial event beds as evidenced by Be-7. Both resuspension and biodiffusion increased the modeled seabed inventory of Th-234. A thick fluvial deposit increased the seabed inventory of Be-7 and Th-234 but mixing over time greatly reduced the difference in inventory of Th-234 in fluvial deposits of different thicknesses.
Waipaoa River Shelf; Continental-Shelf; System Roms; Time-Series; New-Zealand; Deposition; Event; Bioturbation; Preservation; Mississippi
Birchler,, Justin J.; Harris, Courtney K.; Sherwood, Christopher R; and Kniskern, Tara A., "Sediment Transport Model Including Short-Lived Radioisotopes: Model Description and Idealized Test Cases" (2018). VIMS Articles. 1214.