Defining the extent of the Last Glacial Maximum Antarctic Ice Sheet and the timing of its subsequent retreat still remains poorly understood for numerous drainage sectors. New marine geoscientific field data from a formerly unstudied West Antarctic continental shelf sector reveal the last maximum extent of the ice sheet and its initial retreat. It is shown how modern continental shelf regions must have already been evacuated at a remarkably early stage, thereby validating a rather diachronous retreat pattern of the Antarctic Ice Sheet following its last maximum extent.