Ibrahim, Rami (2015-11). The Effect of Particle Sorting on 230Th Sediment Inventories in the Eastern Equatorial Pacific Ocean. Master's Thesis.
The 230Th Method of determining mass accumulation rates (MARs) assumes little to no fractionation during lateral syndepositional processes occurring at the seafloor. We examine 230Th inventories in paired jumbo piston core sediments from paired winnowed and focused sites to radiocarbon-dated multicore sediments at the Carnegie Ridge in the Panama Basin. Radiocarbon-derived coarse content MARs, likely representative of vertical rain of particles poorly transported by sea bottom currents, are spatially and temporally similar, whereas measured xs230Th-derived MARs are lower than age-model-derived MARs at both sites. 230Th-normalization suggests focusing factors ranging from 2 at "thin" site 11JC, and 5 at "thick" site 17JC, with little temporal differences between MIS 1 and MIS 2. 230Th-normalized coarse content shows no temporal or spatial patterns, whereas age-model-derived coarse content yields the expected temporal similarities between both sites. The latter method also suggests higher productivity (higher deposition rates) during MIS 2 compared to those measured during MIS 1. 230Th-normalized measurements of one component of the fine-grained fraction, dust fraction as estimated with the 232Th concentrations, provides evidence for the utility of 230Th constant-flux proxy in highly focused regions in the ocean.