Abstract:
Beaches in McMurdo Sound have developed since the last glaciation when ice sheets were at their maximum. The weight of the overlying ice, depressed the land, which has slowly rebounded forming a series of beaches. To obtain a height above sea level today, it is necessary to know where sea level was on the raised beach ridges. The process of modern beach formation was investigated to help determine
... ancient sea levels around Antarctica in order to determine the extent and thickness of the last glaciation ice cap over Antarctica. Nine sites were investigated including Marble Point, Kolich Point, Spike Cape, Dunlop Island, Cape Bernacchi, Cape Royds, Cape Hallett, Cape Bird and Cape Barne. Surveys of the beaches were carried out by creating profiles of the beach shore, from the waters edge (or shore attached ice) up to the marine limit, with locations chosen to represent the widest possible range of energy environments on beaches in McMurdo Sound. Where possible profiles were surveyed to benchmarks which were linked to sea level via the tide gauge at Cape Roberts. These were a starting point to run a GPS base station to give approximate locations for each surface exposure sample site, site of each hole dug and other significant points. To resolve the surveys for mean sea level, lag times from Cape Roberts to various locations along the coast were calculated from tidal measurements taken at Cape Bernacchi and Cape Bird. The tidal curve constructed from these data was compared with the observed tidal data for Cape Roberts. Offshore surveys were also undertaken at Marble Point, Cape Royds and Cape Bird. In addition to surveying profiles, pits were excavated so that the stratigraphy and sedimentology of the beaches could be examined. Pits were located on survey profiles so they could be related to each other. Pits were described, measured and samples were removed for size analysis. The beach processes were observed in action including the effects of waves and ice when the sea ice has broken up and out. Optically stimulated luminescence samples were collected at Cape Bernacchi, Marble Point, Kolich Point, Spike Cape and Cape Barne. These require sandy material that has been sunlight, then been buried, such as in beach ridges in order to date sediment exposure. 
