Evidence from seismic reflection profiles across the southeast Australian continental margin indicates that in some areas eustatism has not influenced the shelf‐break zone. Where this is the case, insufficient sediment has accumulated along the rifted continental margin since the opening of the Tasman Sea to compensate for subsidence and to raise the sea floor to within reach of wave‐base erosive influences during low sea levels. In some instances there is no evidence of outbuilding, and the sediments are draped over basement structures; thus the change of slope at the shelf break is the surface expression of basement relief and changes in the depth of the shelf break are related to changes in depth of basement. Erosion during times of low sea level has played no part in the development of the shelf break and therefore it is not necessary to invoke neotectonism to explain variations in its depth.