geology of the simpson desert

Around 270 million years ago during the Permian, the area now containing the Simpson Desert was heavily glaciated, and after this inundated with sea followed by shallow freshwater lakes. Organic material was laid down in this period and downfaulting created the Pedirka Basin, which is the source of hyrdrocarbons in the area, causing the ongoing exploration for petroleum.

Around 225 million years ago the region experienced downwarping and further inundation from freshwater lakes and rivers, creating the Eromanga Basin. The sediments from this basin overlaid those of the Pedirka basin creating a seal. During the Jurassic, course sands were laid down, these now form the aquifers of the Great Artesian Basin.

During the Cretaceous period the Eromanga Basin sagged and Australia became two islands flooded by the Cretaceous Sea. Marine sediments were laid down, and these formed a capping over the course Jurassic sands, thus, over a period of 150 million years, the Great Artesian Basin was formed.

In the early Tertiary, around 70 million years ago there was further downwarping in the area creating the Lake Eyre Basin, the area covered with shallow lakes and floodplains into which flowed meandering rivers. The deposits from these form a layer of sediment up to 200 meters thick that sits beneath today’s dunefield. Major fluctuations in climate occurred during the Pleistocene around 1.8 million years ago, and the lakes and rivers dried up.

The modern dunefields are infants in geological terms. Stratigraphic sectioning and fossil dating suggests that dunefield building commence within the last 18,000 years, some scientists suggest as recently as 8-10,000 years ago during the early Holocene.