There are volcanic rocks from low hills in the shale landscapes.
The Basin's sedimentary rocks have been subject to uplift with gentle folding and minor faulting during the formation of the Great Dividing Range.
The ripple marks from the ancient river that brought the grains of sand are distinctive and easily seen, telling geologists that the sand comes from rocks formed between 500 and 700 million years ago far to the south.
This means that the highest part of the visible lines almost always faces approximately south.
The south and southwest of Sydney is drained by the Georges River, flowing north from its source near Appin, towards Liverpool and then turning east towards Botany Bay.
The other major tributary of Botany Bay is the Cooks River, running through the inner-south western suburbs of Canterbury and Tempe.
Parramatta River drains a large area of Sydney's western suburbs.