The Australian mainland's continental crust, excluding the thinned margins, has an average thickness of 38km, with a range in thickness from 24 km to 59 km. Australia's geology can be divided into several main sections, showcasing that the continent grew from west to east: the Archaean cratonic shields found mostly in the west, Proterozoic fold belts in the centre and Phanerozoic sedimentary basins, metamorphic and igneous rocks in the east.