LITHOFACIES DISTRIBUTION IN RELATION TO THE GEOMORPHIC PROVINCES OF PRYDZ-BAY, EAST ANTARCTICA

Over the past 15 years, Japanese, Australian and Russian expeditions t o Prydz Bay have collected about 30000 km of bathymetric data, 6000 km of sidescan sonar data and more than 250 sediment grab and core sampl es. These data were used in the present study to compile surficial sed iment, bathymetric, and geomorphological maps of the Prydz Bay region. Lithofacies distribution was determined by surficial sediment data an alysis using sample matrix (Q-mode) and cluster analysis techniques ba sed on data from 206 sites. Data included percentage biogenic silica(o pal), calcium carbonate, gravel, mud, and relative abundance of two di atom species (Fragilariopsis curta and F. kerguelensis). Five lithofac ies are identified from the available data: (1) slightly gravelly sand y mud (g)sM lithofacies, (2) siliceous mud and diatom ooze (SMO) litho facies, (3) F. kerguelensis pelagic ooze lithofacies, (4) F. curta gra velly muddy sand gmS lithofacies and (5) calcareous gravel lithofacies . In many areas the lithofacies correlate to geomorphological province s as defined by previous investigators using 3.5 kHz and sidescan sona r data. In some cases, Holocene SMO sediments are seen to drape over i ceberg plough marks, implying that these are relict features. These fi ve lithofacies are likely to dominate most of the East Antarctic shelf region and may be helpful in defining sedimentary successions resulti ng from ice-sheet advance and retreat over glacial-interglacial cycles .