Degree

Master of Science (MS)

Department

Geology and Geophysics

Document Type

Dissertation

Abstract

Multi-cores and piston cores were collected seaward of the Mississippi River Delta’s Southwest Pass at ~80 m water depth in 2017 to better understand sedimentary characteristics and processes on the Mississippi River Delta Front (MRDF) in the vicinity of the SS Virginia shipwreck, and to support marine archeological research. Core analyses were performed to inform our understanding of the dynamics of sediment motion in the study area through radionuclide activity (210Pb and 137Cs), volume frequency of grain size, bulk density, and fabric (X-Radiography). Sediment accumulation rates (SAR), calculated from multi-core 210Pb activity are 0.22 - 0.29 and 0.29 – 0.51 cm/year below 20 cm. 137Cs is not uniformly present in the seabed shallower than 20 cm. With this knowledge, accumulation rates based on 137Cs were 0.13 – 0.37 cm/yr since 1954 and 0.15 – 0.37 since 1963. In most cores, SARs reveals overall increasing activity with increasing depth suggesting sediment accumulation rates at the SS Virginia are declining or even erosional. Sediments in cores are primarily bioturbated near surface with sparse faint bedding present at depth and are primarily clay and fine silt. X-radiographic images show burrows in multi-cores surrounding shipwreck revealing abundant life present and a source for observed bioturbation. Bulk density is relatively consistent through cores. Bathymetric data reveals potential east – west scouring of sediments across the mudflow lobe due to wave and currents in the area having the capacity to produce resuspension likely causing bypass or erosion. Flow speeds of the Virginia lobe suggests downslope mudflow movements of mass transport occur at rates far higher than the rate of resupply from the Mississippi River.

Date

6-9-2023

Committee Chair

Samuel Bentley

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