The older, western, two-thirds of the continent is much thicker (over 200 km thick) than the eastern third (about 38 to 59 km thick). The continental crust is mainly made of Archaean, Proterozoic and some Palaeozoic granites and gneisses. A thin veneer of mainly Phanerozoic sedimentary basins cover much of the Australian landmass (these are up to 7 km thick).