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Miocene Nullabor Limestone


The Nullabor cliffs form the 800 km long southern boundary of the Nullabor Plain a 250 000 km2 Miocene seabed uplifted 3 Ma. The 60-120 m high cliffs commence at Head of (the Great Australian) Bight in South Australia and extend west as the Bunda Cliffs for 210 km. They then move inland as the Hampton Bluffs for 300 km fronted by an emerged seafloor called the Roe Plain, before reaching the coast again at Twilight Cove. From here they extend southwest for 160 km as the Baxter Cliffs, before heading inland again as the Wylie Scarp for 120 km, at total cliffline of 790 km, possibly the longest in the world. The lower white Wilson Bluff limestone is Oligo-Miocene and chalky in texture, while the upper red Nullabor limestone is mid-Miocene and is harder, crystalline and contains flints. The flints were collected by the local aborigines and traded throughout central Australia. Much of the cliffline and backing coast is part of the Nullabor National Park in South Australia and Nuytsland Nature Reserve in Western Australia. Extensive caves underlie the porous plain and no surface water exists along this entire section. It is essentially uninhabited, apart from occasional roadhouse on the Eyre Highway, which parallel part of the coast a few kilometers inland. The highway is named after John Eyre the first European to traverse this entire coast, with extreme difficulty, in 1840-41.

The figure above shows Pleistocene dune calcarenite (left) onlapping over Miocene Nullabor Limestone, at Merdayerrah Sandpatch in far western South Australia. Coastal dunes have built sand ramps up and over the vertical cliffs at past sea level high stands to deposit clifftop dunes. The calcareous rich sands have subsequently been lithified in the semi-arid climate to form dune or aeolian calcarenite, as shown in picture. Since the Holocene sea level still stand the exposed softer limestone cliff in foreground has eroded back 200 m more than the calcarenite. This photo was taken October 2010 by Andrew D. Short, Coastal Studies Unit, School of Geosciences, University of Sydney, Sydney NSW 2006, Australia, This e-mail address is being protected from spambots. You need JavaScript enabled to view it

 

 

 

 


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