Description: Thanks to improved multibeam swath bathymetry, targeted coring of glacial landforms is now possible. In turn, it is possible to improve our understanding of sedimentary facies that developed in glacimarine settings during the post-Last Glacial Maximum (LGM) deglaciation. We explore foraminiferal records from 18 sediment cores from the western Ross Sea largely from sites near paleo-grounding lines. Based on general foraminiferal indices and radiocarbon dates, we identify environments and geomorphic settings from which high quality in situ foraminiferal data can be obtained, which is imperative for paleoenvironmental reconstructions and geochemistry on glaciated continental margins worldwide. We investigated post-LGM foraminiferal assemblages from distinct glacimarine environments, including those from proximal and more distal locations with respect to paleo-grounding lines as well as an unusual assemblage influenced by the drainage of subglacial meltwater into the ocean. Despite clear differences in post-LGM foraminiferal records between the western and the eastern Ross Sea, it appears that the high bathymetric gradient of grounding zone wedges is a key factor promoting rich benthic foraminiferal communities in habitats proximal to grounding lines. Additionally, rapid deposition of meltwater plume sediments inhibited - and in some cases, significantly altered - foraminifera abundance and diversity. This knowledge will enable better site selection in future studies on the Antarctic continental shelf and potentially other glaciated margins.

Description: Calmette Bay within Marguerite Bay along the western side of the Antarctic Peninsula contains one of the most continuous flights of raised beaches described to date in Antarctica. Raised beaches extend to 40.8 m above sea level (masl) and are thought to reflect glacial isostatic adjustment due to the retreat of the Antarctic Peninsula Ice Sheet. Using optically stimulated luminescence (OSL), we dated quartz extracts from cobble surfaces buried in raised beaches at Calmette Bay. The beaches are separated into upper and lower beaches based on OSL ages, geomorphology, and sedimentary fabric. The two sets of beaches are separated by a prominent scarp. One of our OSL ages from the upper beaches dates to 9.3 thousand years ago (ka; as of 1950) consistent with previous extrapolation of sea-level data and the time of ice retreat from inner Marguerite Bay. However, four of the seven ages from the upper beaches date to the timing of glaciation. We interpret these ages to represent reworking of beaches deposited prior to the Last Glacial Maximum (LGM) by advancing and retreating LGM ice. Ages from the lower beaches record relative sea-level fall due to Holocene glacial-isostatic adjustment. We suggest a Holocene marine limit of 21.7 masl with an age of 5.5-7.3 ka based on OSL ages from Calmette Bay and other sea-level constraints in the area. A marine limit at 21.7 masl implies half as much relative sea-level change in Marguerite Bay during the Holocene as suggested by previous sea-level reconstructions. No evidence for a relative sea-level signature of neoglacial events, such as a decrease followed by an increase in RSL fall due to ice advance and retreat associated with the Little Ice Age, is found within Marguerite Bay indicating either: (1) no significant neoglacial advances occurred within Marguerite Bay; (2) rheological heterogeneity allows part of the Antarctic Peninsula (i.e. the South Shetland Islands) to respond to rapid ice mass changes while other regions are incapable of responding to short-lived ice advances; or (3) the magnitude of neoglacial events within Marguerite Bay is too small to resolve through relative sea-level reconstructions. Although the application of reconstructing sea-level histories using OSL-dated raised beach deposits provides a better understanding of the timing and nature of relative sea-level change in Marguerite Bay, we highlight possible problems associated with using raised beaches as sea-level indices due to post-depositional reworking by storm waves.