40 PLANT HABITS AND HABITATS IN THE 



A striking and characteristic feature of the Lake Eyre Basin as a 

 whole is the fact that it is an important part of the vast artesian basin 

 of Australia, of which approximately one-fifth lies in South Australia. 

 There are numerous "mound" springs on the border of Lake Eyre 

 and many deep borings have been made, some of which yield great 

 quantities of water. The one at Coward Springs, for example, has a 

 daily flow of 1,000,000 gallons. The water-supply is derived from the 

 western flanks of the mountains of New South Wales and Queensland 

 and the intake is chiefly porous sandstones, probably of different geo- 

 logical ages. These sandstones are covered by great thicknesses of 

 dark-blue shale, sandstones, and impure limestones of Cretaceous age. 

 Thus the subterranean water is far too deep to be of direct benefit to 

 surface plants, if it were always of suitable quality, which is sometimes 

 not the case. 



To the southeast of Lake Eyre is situated a chain of lakes, of which 

 Lake Fromme is the largest. These are described by Howchin as 

 being merely extensive flats which are sheets of water after heavy rains 

 and are saline wastes during dry seasons. They are the centers of a 

 relatively restricted drainage area, and no rivers of importance dis- 

 charge into them. 



Another group of related basins, somewhat larger than those of the 

 Fromme group, lies to the west of Lake Torrens and north of the 

 Gawler Ranges. Of these, the largest is Lake Gairdner. The Trans- 

 Australian Railway skirts the northern portion of these basins. 

 Tarcoola is a few miles west of them and Port Augusta is 50 miles, more 

 or less, to the east. Lake Gairdner and the rest of the basins lie at the 

 northeastern side of scattered remains of mountains of Archaean age, 

 from the waste of which the sand of the region may have been derived. 

 The region is relatively very dry. The 10-inch isohyet which, in 

 passing through the Flinders Mountains, curves rapidly to the north, 

 is here deflected as strongly to the south and includes none of the area. 



The northern section of the Flinders Mountains has on the west the 

 central rift-valley of South Australia, which is made up of Lake 

 Torrens on the north and a descending series of flats and lagoons which 

 connects it on the south with Spencer's Gulf. Thus Lake Torrens, 

 which owes its existence to faulting, is in a manner distinct in origin 

 from the other basins. The bold western side of the Flinders Mountains 

 has already been noted. This is the upthrow side of the north-south 

 fault by which the Great Valley of South Australia was formed. This 

 fault, as Howchin states, increases in importance as it goes south and 

 includes Gulfs Spencer and St. Vincent (see also Taylor, 1918:97). 

 The area of depression, therefore, fairly parallels the western side of the 

 entire central mountain system of South Australia. 



That the earth's crust in this region is not in equilibrium is further 

 evidenced by the occurrence of earthquakes from time to time center- 



