The passive (rifted) continental margin of Wilkes Land, Antarctica, is characterized on seismic reflection records by (i) in the south, a block-faulted sequence of highly stratified continental beds overlain by two distinct unconformities; (ii) a transitional, greatly thinned continental crust overlain by material interpreted to be flood basalt; and (iii) in the north, oceanic crust with a boundary ridge at its edge. The Mohorovic??ic?? discontinuity can be followed across the continent-ocean boundary and shows a progressive thinning of continental crust to a minimum of 2.5 kilometers at its northern edge.