THE DARLING PENEPLAIN OF WESTERN AUSTRALIA. 395 
have been given for believing that the duration of the great 
laterite cycle was almost inconceivably protracted. The 
beginning of this period must therefore have been much 
earlier in Tertiary time, and the date of the Mount Dale 
peneplanation may have been quite early in that era. 
Summary. 
The author agrees with Jutson in describing the uplands 
of South-Western Hastern Australia as an uplifted peneplain 
but goes further, and claims that not one but several 
periods of uplift, with intervening periods of crustal stability, 
can be recognized. For the oldest peneplain, represented 
by a few scattered residuals only, the name *‘ Mount Dale 
Level ’”’ is suggested. 
The name ‘Darling Peneplain”’’ should be confined to the 
laterite covered surface so widely developed in Western 
Australia, and reasons are advanced for believing that 
an enormously protracted period of crustal stability is 
demanded for the production of this peneplain. 
A subsequent small elevation caused the development of 
an extensive series of mature valleys, for whose base level 
the name.*’ Meckering Level” is suggested. It is probable 
that, during this cycle of erosion, mature valleys were 
carved on the eastern as well as the western side of the 
land surface, and that these valleys subsequently decided 
the development of the great salt lakes of the goldfields 
areas. Probably the marine beds of Norseman were 
developed during this period, and possibly also some of the 
deep leads. | 
A sharp uplift of the highlands, with an isostatic depress- 
ion of the coastal area, brought about the existing con- 
ditions of topography. Dissection of the uplifted Darling 
Peneplain, now at an average altitude of about 1,000 feet 
above sea-level, caused dismemberment of the mature 
valleys of the Meckering level. 
