Wikipedia and the Geology of Victoria

You have to be wary of Wikipedia, and there are two claims regarding the geology of Victoria made on Wikipedia that I find puzzling.

The first and foremost is on the formation of the Great Dividing Range, of which the Australian Alps constitute the southern tip.

The Great Dividing Range was formed during the Carboniferous period—over 300 million years ago—when Australia collided with what is now parts of South America and New Zealand. The range has experienced significant erosion since

This is far too quick and far too simplistic. Although it is the case that mountain building associated with the collision of small tectonic plates did occur “over 300 million years ago” one should not be left with the impression that this accounts for the highest part of the Great Dividing Range, namely the Australian Alps, or even the Range itself.

My understanding is that the formation of the Australian Alps is associated with the thinning of the crust at boundaries of separation as Gondwana began the process of breaking up, leading to the formation of a high plateau, some 2000 metres lower than Tibet, as rising magma from deep below lifted the thinner crust along what is now eastern Australia. As Zealandia, since subducted, separated from eastern Australia faulting led to the formation of a rift valley along eastern Australia and subsequent erosion has carved valleys and gorges in the Australian Alps giving the Australian Alps its current geography, with its mountain range like landscape. This erosion has not lowered the height of the Australian Alps.

So in this way the Australian Alps are less mountains and more a plateau.

There is a nifty little primer on this and a cool video. The jumper alone makes this dude a legend.

The second concerns the presence of Neoproterozoic, or Precambrian, rocks in Victoria. According to Wikipedia

The northwest of the state is mostly Cainozoic rocks while the southeast is primarily made up of Palaeozoic rocks. There have been no discoveries of Precambrian rocks in Victoria.

The Geology Society of Victoria writes

The oldest rocks of mainland southeastern Australia are Late Proterozoic or Cambrian volcanics, volcaniclastics and turbidites

However, according to the weekend geologist website Neoproterozoic rocks can be found at Kitty Miller Bay at Philipp Island.

As can be seen I’m no expert, an enthusiastic fellow geological traveller, with a fondness especially for the Australian Alps, hungry for more knowledge and understanding. There is a good recent ABC report on the environmental challenges posed by increasing tourism, and much else besides, in the Australian Alps. It is sad to see such a pristine and beautiful part of the world affected like so.

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