Australia: The Land Where Time Began

A biography of the Australian continent 

Slackwater deposits in Finke Gorge

These are formed when floodwater with a high sediment load is diverted to an area of quieter flow where the sediment is deposited. In the case of Finke Gorge this occurs in a disused gorge that is believed to have formed at a time when the climate was much wetter than the present, that connects to the main gorge that is currently used by the river when it floods. It was formed about 30 million years ago. The layers of sediment formed as it is deposited in such slow-moving parts of a stream can often be read like tree rings, recording the occurrence of flood events. The Finke Gorge slackwater deposit is the best known formation of its type in Australia. It is believed that the gorge currently used by the flooding Finke River is about 5 million years old.

Dating these deposits has shown that during the past 700 years the highest volume floods have occurred in 1967, 1972, and 1974 (as of 1993). It has been suggested that the fact that the 3 years of highest floods all occur in the 20th century may be indicating that while the Australian climate may be drying, it is also becoming more prone to more frequent and more severe extreme events.

Sources & Further reading

Penny Van Oosterzee, The Centre, the Natural History of Australia's Desert Regions, Reed, 1993