ARID PORTIONS OF SOUTH AUSTRALIA. 7 



To quote Jutson (1914:20), the interior of the great plateau is arid 

 and has no permanent rivers. The drainage runs into shallow basins 

 (with no outlet except at times of great flows of water), called "salt" 

 or ''dry" lakes. There is, however, fresh water to be found where the 

 catchment has been suitable, as, for example, the "soaks" like the well- 

 known one at Ooldea, and basins in the rocks, as vividly described by 

 Carnegie (1898:191). But, with the possible exception of the former, 

 these have no significance so far as the vegetation is concerned. As 

 the interior has little rain and no rivers, there is no water table. The 

 picture that the great plateau presents as a whole is therefore a very arid 

 one, both as regards the aerial and the sub aerial plant environment. 



The great plateau is regarded by Jutson (1914:20-21) as being an 

 old, uplifted surface, a vast peneplain, whose surface has been much 

 destroyed, planed down, and often not recognizable. In the southern 

 half of Western Australia the rocks of a very large area are probably 

 pre-Cambrian, while in the southeastern corner they are Mesozoic or 

 early Tertiary (Jutson, I. c), which is the region known as the Nullarbor 

 Plains. Where the great plateau of the western part of the continent 

 joins the big central artesian basin, the rocks are also of the Mesozoic 

 and more recent ages. As a whole, therefore, the great plateau is of 

 very great geological antiquity. 



That portion of the desert-arid region which lies within the Great 

 Plains varies in altitude from somewhat below the level of the sea to 

 1,000 feet or more above it. One of the characteristic physiographical 

 features is the presence of steppes (Spencer and Gillen, 1912:5) or 

 table-lands of Upper Cretaceous and Lower Cretaceous formations 

 (Jack, 1915:13), which connect the Great Plains to the Western 

 Plateau. On the east the plains gradually rise to the highlands of 

 eastern Australia. The sandhills, which are especially to be found to 

 the north and east of Lake Eyre, but occur to the northwest as well, are 

 built of material derived by erosion from the desert sandstone of the 

 steppes, and the "gibber" plains, or stony deserts, also trace their origin 

 to these Cretaceous plateaus and are the residue remaining in place. 



A most striking feature of the Great Plains regions is the presence 

 of several large lakes which in earlier geological times contained fresh 

 water but are now saline wastes, usually carrying water only after 

 heavy rains. Of these. Lake Eyre and Lake Eyre South are the largest, 

 covering an area of 5,000 square miles when filled with water (Howchin 

 and Gregory, 1909: 100). Lake Eyre receives the discharge of several 

 rivers of intermittent flow. At various places in the Lake Eyre basin 

 natural artesian wells are found whose outlets are raised into small hills 

 through the deposition of minerals held in solution. Also, numerous 

 "bores," deep wells, have been sunk for economic purposes. The water 

 that supplies the wells of whatever sort is derived from rains falling 

 in the Eastern Highlands or is chiefly plutonic (Pittman, 1914). 



