The overall relative relief of the continent at the beginning of the Cenozoic was very much as it is today except that the area of the present Mount Lofty/Flinders Ranges was probably low-lying. The climate, however, was much wetter. Australia lay in latitudes of 25 degrees to 60 degrees S, separated from Antarctica by a rift valley with lakes and marginal seas; it is unlikely that there was any significant ice cap.

Bass Strait was mainly land, with floodplains, lakes and peaty swamps. This map shows river systems in existence in the western half of the continent. Today, the old valleys are represented by chains of salt lakes.

In the eastern part of the continent, rivers spread thin sheets of sand over wide areas centred on the Gulf of Carpentaria, Lake Eyre and the Murray Basin. Much of the Coral Sea, including the site of the Great Barrier Reef, was land, and the only places where seas encroached beyond the present coastline were in the Carnarvon Basin and locally near Perth.

Basaltic eruptions continued in the Eastern Highlands and in places the basalt flows buried gold-bearing stream channels. Locally, trees growing close to lakes that formed when lava flows dammed valleys, were silicified and preserved during subsequent eruptions. Growth rings in these fossil trees indicate a seasonal climate.