394 W. G. WOOLNOUGH. 
tion. The evidence with regard to the Cretaceous rocks 
at Gingin is almost, if not quite as conclusive, except that 
the topmost member of the Cretaceous series, being a 
porous sandstone, is not a suitable rock to produce laterite. 
It is, however, so strongly ferruginous as to suggest that 
it was a superficial formation when laterization was in > 
progress. Its position with regard to the laterite to the 
Darling Range is not identical with that on the Jurassic 
formation (fifty miles further north). It is certain, however, 
that it has been displaced to some extent by the formation 
of the main Darling fault. There is no doubt, then, that 
the peneplanation is post-Jurassic, and there is extremely 
strong presumption that it is post-Cretaceous. 
With regard to its upper limit of age, the author is much 
more doubtful, and is inclined to place it much furtber 
back than does Jutson. The latter argues from the im- 
maturity of development of existing valleys in the Darling 
Range, but, as the author has shown, these valleys do not 
date from the termination of what may be termed the 
‘great laterite cycle,’’ but from the close of the ‘“‘Mecker- 
ing Level’’ cycle. Assuming the latter to have been con- 
temporaneous with the formation of the Norseman Beds, 
it is to the Meckering Level cycle that Jutson’s reasoning 
applies with full force. This being so, the age of the Darling 
Peneplain must be notably older, since a considerable period 
must have been necessary, not only to excavate the valleys 
of the Meckering Level, but to bring them into such marked 
adjustment with geological structure as seems to be the 
case. The author would therefore place the date of the 
close of the main peneplanation at least at the lower limit 
(older Pliocene) assigned by Jutson, with a strong prob- 
ability that it may even be somewhat older still. Reasons 
‘ The author feels strongly, that in view of the uncertainty which 
exists with respect to the correlation of the Australian Tertiaries, the use 
of such terms as Miocene, Pliocene, etc., is of doubtful advantage, and 
would prefer the use of a term such as Norseman or Eucla to indicate the 
ages of the formations developed respectively at these two places. 
