The Sahul Shelf, located between northwestern Australia and the Timor Trough, consists of a central basin surrounded by broad, shallow rises. Superimposed on the regional relief is a system of banks, terraces, and channels. The flat tops of banks and terraces form parts of several regional, subhorizontal surfaces. The steplike topography closely resembles the system of late Cenozoic erosional surfaces on the adjacent land of which it probably is the submerged extension. This requires uplift, weathering, and denudation of the shelf in middle and late Tertiary. Subsequently, the shelf was deformed to form the basin and rises. This deformation caused the original drainage to become antecedent. Lower surfaces were formed during Pleistocene low sea-level stands.