Features and Groivt/t of Lake Goongarrie. M'^ 



Unique Characteristics of West Australian Playa 

 Country as compared with other Areas. 



So far as the writer's reading and observations extend, the 

 features described above are quite unique, and nothing really 

 similar has been found in any other part of the world. Elsewhere 

 the general sequence from the high land to the playa surface across, 

 the various belts, is, according to Hobbs,i (1) the high land, (2) the 

 zone of the dwindling river with its sloping bench of coarse rubble 

 and gravel, (3) the belt of sand dunes which are often separated by 

 narrow flat-bottomed basins carrying detritus, and (4) the central 

 sink, which contains the true lacustrine deposits of clay and 

 separated salts. There is no mention of bedrock floors here. 

 Detrital deposits occur continuously from the foot of the high lands 

 to the central sink. 



At Goongarrie, proceeding from the high lands eastwards in a 

 line just north of the Boddington Island across to the fine silts of 

 the playa on its eastern side, the high lands of hard rocks terminate 

 by fairly steep slopes or cliffs; thence follows a narrow^ piedmont 

 plain made up of coarse detritus, brought down by the transitory 

 streams, and having a gentle eastward fall; but such plain, instead 

 of gradually sloping into flatter country, M'ith a change to finer 

 detritus, either ends abruptly in a Ioav cliff (about four to six 

 feet high) with a rock floor at its foot, or merges gradually into a 

 rock floor. The piedmont plain is thus in the former case trun- 

 cated. The rock floor extends eastwards for about one and three- 

 quarter miles, broken only by quartz reefs and their detritus, by 

 sand ridges, and by films of fine detritus in the rock basins or on 

 the rock floors between the sand ridges. Farther east the fine silts 

 cover tlie rock floor of the lake. In other places there is no pied- 

 mont plain, the high steep cliff being abutted by the rock floor. In 

 others again the gently sloping '' lowlands " take the place of the 

 ** high " lands. The sudden cessation of detritus and the occur- 

 rence of the bare rock floors are most striking, the rock floors 

 possessing the appearance of having been recently swept by a 

 gigantic broom., 



1 Hobbs, W. H. "Earth Features and their Meaninjf," New York, 1912, px>. 216-217, and' 



fig. 2;n. 



