부산대학교 도서관

Sediment cores were collected from a mudflow lobe (80 m water depth) offshore of the Mississippi River’s Southwest Pass in 2017 to better understand the sedimentology near the lobe entraining the SS Virginia shipwreck (sunk by a German U-boat in 1942) and surrounding Mississippi River delta front. Core analyses included [sup.210]Pb/[sup.137]Cs geochronology, granulometry, and X-radiography. Sediment accumulation rates (SAR) calculated from excess [sup.210]Pb activity in multicores are 0.22–0.29 cm/y at seabed depths less than 20 cm and 0.29–0.51 cm/y at depths greater than 20 cm. Accumulation rates for [sup.137]Cs have been ~0.15 to ~0.37 cm/y since 1954 and 1963, respectively. Sediment accumulation rates from [sup.210]Pb, [sup.137]Cs geochronology and indicators of relative sedimentation and bioturbation from X-radiographs suggest that rates of sediment accumulation near the Virginia have declined since the mid-20th century. This may be explained by the multi-decade downslope mass transport of the mudflow lobe in which the shipwreck is embedded and decreases in sediment supply delivered offshore from the Mississippi river. Mass transport calculations of the Virginia lobe derived from core properties and published lobe advection rates suggest downslope mass transport is far higher than sediment resupply from the Mississippi river, consistent with recent studies of delta retreat.
Author(s): Nathan Figueredo (corresponding author) [1,*]; Samuel J. Bentley [1]; Jason D. Chaytor [2]; Kehui Xu [3]; Navid Jafari [4]; Ioannis Y. Georgiou [5]; Melanie Damour [6]; Jeffrey Duxbury [1]; [...]