87 
Tertiary Deposits Near Norseman, Western Australia. 
The iloors of the salt lakes of Western Australia are almost perfectly 
smooth and, after heavy rain, may for a short time be covered with water 
which is rarely as much as three feet deep. 
Lake Cowan, and Lake ibindas 5 miles farther east, occupy shallow 
depressions, about 900 feet above sea-level Avhich are elongated in a north- 
south direction approximately parallel to the strike of the Pre-Cambrian 
locks on which they lie. A bore sunk in 189b in the lake-bed Just Avest 
of N(n*s('man traversed 977 feet of lacustrine muds Lefore reaching Pre- 
Cambrian rocks (Campbell, 19(H), p. 15), so that the depth of part of the 
depression occupied by Lake Cowuui Avas once of the order of 400 feet. 
JMost of the auriferous greenstone belts of Western Australia are 
more liilly than the surrounding country, npparcnlly l)ecaase the green- 
stones are more resistant to tiie agents of ari<l erosion than nre the other 
rocks ot tin* Ib'c-Cambrian comph'X, ])ut the Xorseinan greenstone belt Avith 
its long, nnitow, steep, north-trending ridges and v-shaped valleys shoAA^s 
unusually higli relief. A large dyke of norite (Campbell, lOOb, p. 24 and 
%. o) Avith an easterly strike forms a line of hills cutting across the 
Text tig. 2. 
Norseman ;uid the southciii imrt of Lake Cowan from the riilge just east 
of tile town. 
