Australia: The Land Where Time Began

A biography of the Australian continent 

It is obvious that Lake Gairdner is a drowned valley. Situated in the Gawler Ranges, Lake Gairdner is the most beautiful of the Australian salt lakes. It is a spectacular sight, the blazing white of the halite-covered bed contrasting with the red rocky beaches, rocky shores and lunettes and the pale green mulga and myall. It is about 160 km N-S, and 50 km wide, E-W. Its shape is irregular. There are forks that were probably tributary valleys, from a previous, possibly wetter, age. The maximum depth the lake is believed to reach when full is 75 cm. Beneath the halite crust are saline clays and sands studded with gypsum crystals, but the unconsolidated sediment is probably shallow. The only bore sunk in reached bedrock at 19 m.

It was originally a broad, shallow valley with many isolated hills on the valley floor. They are now rocky islands in the halite crust. On the rocky shore of the islands and the lake margin are unusual caverns and hollows that resulted from salt weathering.

Silcrete of Early-Middle Tertiary age is found on some islands in the northern section of the lake. This suggests that the salina is of later Cainozoic origin. Lunettes are found on parts of the northern shore. The lake has filled since European settlement, but it is usually dry. Sometimes a patch of water has been known to form on the bed after rain and can be seen being blown around by the wind. When a strong northerly wind is blowing the lake, or pool, is moved to the southern margin, but if the wind swings around to the south it can move to the northern margin over night.

Sources & Further reading

Mary E White, Running Down, Water in a Changing Land, Kangaroo Press, 2000