|Folded rocks in Anakie Gorge|
The Brisbane Ranges plateau was once, about 500 million years ago, submerged under an inland sea and the layers of sediment deposited on the seabed eventually compacted into slate and sandstone. The area became exposed over the years and under pressure about a million years ago the land east of the Rowsley Fault that extends from about Bacchus Marsh to Geelong began to sink (Port Phillip Sunkland). The result was an impressive escarpment. Rivers like Little River and StonyCreek eroded deep valleys through the escarpment as they moved down to what is now Port Phillip Bay. Today we can clearly see the layers of ancient rock in the Anakie Gorge formed by Stony Creek.