The Formation and Late Quaternary Palaeoenvironmental History of Sediment Mounds in the Amundsen Sea, West Antarctica

• Main Author: HORROCKS, JENNIFER,ROSE
• Format: Thesis
• Language: unknown
• Published: 2018
• Subjects: Amundsen Sea; West Antarctica; contourite; drift; turbidite; Late Quaternary; Antarctic; Pine Island Trough; West Antarctic Ice Sheet; Antarc*; Antarctica; Ice Sheet; Pine Island
• Online Access: http://etheses.dur.ac.uk/12659/; http://etheses.dur.ac.uk/12659/1/Complete_thesis_with_corrections_FINAL.pdf

This thesis presents the first high-resolution palaeoceanographic study of environmental changes in the Amundsen Sea sector of the West Antarctic continental margin during the Late Quaternary. This part of the West Antarctic Ice Sheet (WAIS) is currently experiencing rapid mass loss and longer-term records can provide important context for these changes. Four piston cores, covering the last c. 375 kyrs, have been studied from two of the five large sediment mounds which stand on the continental rise of the eastern Amundsen Sea. Four of the mounds have been previously been identified in the literature as sediment drifts. The cores were analysed for sedimentology (grain size, physical properties, spectrophotometry), mineralogy (clay minerals, sand fraction composition) and geochemistry (XRF, biogenic silica content, TOC, CaCO3). These data were used to infer the supply of terrigenous material from the West Antarctic Ice Sheet, the amount of biological productivity and the nature of the bottom current. Age constraints for the ≤375 kyr records are derived from relative palaeomagnetic intensity, diatom biostratigraphy, AMS 14C dates, tephrochronology and lithostratigraphy. Analysis of the sediments together with new geophysical and bathymetric data suggests the mounds are mixed contourite-turbidite drifts. Turbidity currents were initiated at the margins of, and between, the mouths of Pine Island Trough East and West and Abbot Trough. The turbidity currents eroded channels in the slope, some of which connect to the deeply incised, maximum 20 km wide and 400 km long channels separating the drifts. The fine-grained fraction of the turbidity currents was pirated and deposited on the drift crests by the weak, eastwards-flowing bottom current, which may be Antarctic Bottom Water or Lower Circumpolar Deep Water. The coarse-grained component of the turbidity currents was largely constrained to the channels, with occasional spill-over depositing sand and sandy muds on the drift flanks. The drifts are long (250-433 km), narrow ...