Abstract:
Raised beaches on the coast of McMurdo Sound have developed since the last glacial maximum approximately 20,000 year ago when the ice sheets were at their greatest extent. The weight of the overlying ice depressed the land which has slowly rebounded after the ice melted, forming a series of beach ridges. The beach ridges and associated rock platforms were dated using three different methods and
... the relative heights above sea level today were obtained. This data will allow modelling of the volume and extent of the ice during the last glacial maximum. Radiocarbon dating of shells and fossil penguin remains found in situ, optically stimulated luminescence dating of sediments and cosmogenic isotope dating of surface exposed rocks, including glacial and ice rafted erratics and rock platforms associated with the raised beaches, was conducted at Marble Point, Kolich Point, Spike Cape, Dunlop Island, Cape Bernacchi, Cape Roberts, Cape Geology, Cape Ross, Cape Bird and Cape Hallett. Modern beach formation processes were observed and were linked to features in the raised beaches to give an accurate position of where sea level was on the raised beaches. Detailed descriptions were made from sections, using evidence at the surface as well as digging holes in strategic locations. Information from the holes included the structure of the beach ridge, pebble counts to work out maximum energy and development of the beach from imbrication. A chronology of ice retreat was determined using surface exposure dating techniques from a series of samples taken at different heights above sea level. Some samples were taken from above the marine limit to help with timing of ice retreat from along the coastal area. Sample sites are tied in with current sea level estimates to provide a height of uplift. Observations of glacial moraines were done by mapping the extent of the various rock types that make up the moraines by a combination of noting where volcanic erratics were found, with line counts and area counts. Surface exposure dating was carried out using cosmogenic isotopes from large erratics droupped out of the glaciers as they retreated. 
