Semester of Graduation
Spring 2024
Degree
Master of Science (MS)
Department
The Department of Geology and Geophysics
Document Type
Thesis
Abstract
Since the end of the Last Glacial Maximum (LGM), the West Antarctic Ice Sheet (WAIS) has been in an overall state of retreat from the Ross Sea continental shelves. Most reconstructions have focused on the contraction of grounded and floating ice from deep-water glacial troughs. There, the former stillstand locations of grounded ice streams are well reconstructed by backstepped grounding zone wedges. These landforms represent sedimentation at the marine terminations of fast-flowing ice streams. Here, we reconstruct the retreat of grounded and floating ice from the shallow crest of Ross Bank, a submarine bank located in central Ross Sea. Given its depth (~150 m) and large area above 300 m water depth (~100 km2) requires that an ice rise existed on Ross Bank as grounded and floating ice retreated in the adjacent deep water troughs. In other words, the Ross Bank was an important pinning point of the Ross Ice Shelf (RIS). Our reconstruction relies on previously collected core from two expeditions, NBP9407 and NBP9601. In the cores, an unconsolidated and fossiliferous sand-rich surface unit is found across the bank crest. The surface layer has a maximum observed thickness of ~3.5 meters. The oldest radiocarbon date of barnacle plate within the winnowed sand suggests that the eastern flank of Ross Bank was free of grounded ice by 5698 ±161 cal years BP. We infer that the unpinning occurred as a single event. It is not clear why the Ross Ice Shelf unpinned from Ross Bank in the mid Holocene. The high abundance of sand is attributed to the strong currents winnowing the underlying clay-rich diamicton. Only three cores penetrate the underlying strata and unpublished diatom assemblage data suggests that they are of Pliocene age. Radiocarbon dates from the adjacent deep-water trough to the east of Ross Bank indicate that a grounded ice stream had retreated and an ice shelf was established over the Glomar Challenger Basin by ~8700 cal year BP. This would indicate that the Ross Bank ice rise existed as a stable buttress for at least 3000 years.
Date
1-24-2024
Recommended Citation
Lindsey, Ben R., "Unpinning of the Ross Ice Shelf from Ross Bank, in Ross Sea of Antarctica" (2024). LSU Master's Theses. 5893.
https://repository.lsu.edu/gradschool_theses/5893
Committee Chair
Bart, Philip J.