ARID PORTIONS OF SOUTH AUSTRALIA. 39 



water only at times of flood. In the south arm, however, the lake 

 usually contains salt water. Important streams enter Lake Eyre on 

 the east, west, and north, of which the Barcoo, or Cooper's Creek, is the 

 most important. On the western side is Neales River, near which 

 Oodnadatta is situated, and which is in part a broad and poorly defined 

 drainage channel, which carries water but rarely. 



Howchin remarks that the opinion formerly held, that the sea had 

 but lately retired from this vast country, is not correct. Rather at 

 a remote time, the Cretaceous, the sea extended from the north as a 

 great gulf, or sea, and covered most of central Australia. Probably 

 there never was a continuous connection, north to south, between 

 what is now Spencer Gulf and the Gulf of Carpentaria. The lowest 

 portion of the land connection between the two is at present given 

 as being 175 feet above the sea. The depression in the southern 

 portion of the Great Basin is thought to have been brought about 

 through a secondary subsidence affecting this portion only. The 

 desert sandstone, as remarked above, was laid down in Upper 

 Cretaceous time, during a period of elevation when the basin was a 

 fresh-water lake. At this time the rainfall was probably better than 

 now and the climate cooler. 



The surface features of the Lake Eyre Basin, and these are repre- 

 sentative of the entire region, are of three kinds, according to Howchin 

 and Gregory. These are tablelands, which, as seen in the vicinity of 

 Oodnadatta, are generally of relatively small extent: (1) "buttes" in 

 fact, (2) stony deserts which are constituted by the "gibber" plains, and 

 (3) the sandhills. At Oodnadatta, also, the surface (except the tops of 

 the buttes) is covered by small stones of various sizes and shapes. The 

 ''gibbers" are usually flattened, polished, and of a reddish-brown color. 

 From the fact that the stone? fit together closely, they are probably 

 important in consei'ving whatever water may fall by cutting down 

 evaporation from the surface of the soil. Just about Lake Eyre, on all 

 sides, sandhills are plentiful; in general, these constitute an important 

 feature of the surface topography in the northern part of South 

 Australia. The sandhills occur as ridges, usually not of great height, 

 and run in a generally northeast and southwest direction. They are 

 frequently separated by "clay-pans," a quarter of a mile or more in 

 diameter, which hold water for a period after rains. Like the "gib- 

 bers," the sand is derived from the eroded desert sandstone. As 

 Howchin points out, owing to there being no opportunity for carry- 

 ing away the sand, as by water-currents of whatever kind, it remains 

 in the basin, di if ting here and there through the action of winds, and 

 "with the ever-accumulating products of waste, the highest hills are 

 gradually covered by drift and the country is ultimately buried under 

 its own ruins" (Howchin and Gregory, 1909:103). 



