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History of Murray River


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Lake Bungunia

Between 2.5 and 0.5 million years ago the Murray River terminated in a vast freshwater lake called Lake Bungunia. Lake Bungunia was formed by earth movement that blocked the Murray River near Swan Reach during this period of time. At its maximum extent Lake Bungunia covered 33,000 square kilometres (13,000 sq mi), extending to near the Menindee Lakes in the north and to near Boundary Bend on the Murray in south. The draining of Lake Bungunia approximately 0.5 million years ago must have been a dramatic event.

Deep clays deposited by the lake are evident in cliffs around Chowilla in South Australia. Considerably higher rainfall would have been required to keep such a lake full; the draining of Lake Bungunia appears to mark the end of a wet phase in the history of the Murray-Darling Basin and the onset of widespread arid conditions similar to today. A species of Neoceratodus lungfish existed in Lake Bungunia (McKay & Eastburn, 1990); today Neoceratodus lungfish are only found in several Queensland rivers.

Cadell Fault and formation of the Barmah Red Gum Forests

The famous Barmah Red Gum Forests owe their existence to the Cadell Fault. About 25,000 BP, displacement occurred along the Cadell fault, raising the eastern edge of the fault (which runs north-south) 8�12 metres above the floodplain. This created a complex series of events. A section of the original Murray River channel immediately behind the fault was abandoned, and exists today as an empty channel known as Green Gully. The Goulburn River was dammed by the southern end of the fault to create a natural lake.

The Murray River flowed to the north around the Cadell Fault, creating the channel of the Edward River which exists today and through which much of the Murray River's waters still flow. Then the natural dam on the Goulburn River failed, the lake drained, and the Murray River avulsed to the south and started to flow through the smaller
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