After the subsidence came another period of uplift, possibly still in progress.
Back of the islands are the quiet waters of lagoons, and at the mouths of rivers are several shallow bays indenting the mainland; these bays were formed by only a slight subsidence of the land and the rivers are filling them with deposits of silt.
This cutting off was caused largely by subsidence, though partly by marine action.
Away from land and more probably were caused by subsidence; the old river-channels known to exist below sea-level, as well as the former land connexion with New Guinea, seem to point to the conditions assumed in Darwin's well-known subsidence theory, and any facts that appear to be inconsistent with the theory of a steady and prolonged subsidence are explainable by the assumption of a slight upheaval.
The Cretaceous period was initiated by the subsidence of a large area to the south of the Gulf of Carpentaria, whereby a Lower Cretaceous sea spread southward, across western Queensland, western New South Wales and the north-eastern districts of South Australia.