Shallow seismic reflection profiling on the continental shelf of northern New South Wales shows a lens of sediments which thickens beneath the mid-shelf, but usually thins beneath the outer shelf and upper slope. The sediments were deposited on a prominent bedrock surface. The bedrock surface sharply increases its gradient, usually beneath the present shelf break, and it is considered to represent the break-up unconformity of the western margin of the Tasman Basin. Within the sediment sequence a prominent unconformity separates a lower sequence of foreset and gently inclined beds from an upper sequence that is generally conformable with the unconformity and the present-day sea floor. Offshore from substantial rivers a deltaic sequence with high-angle foreset bedding was deposited, while elsewhere sub-horizontal, even-bedded sediments were laid down upon a subsiding basement. However, the steep slope of the bedrock surface beneath the present continental slope has prevented any significant outbuilding of the continental shelf.