320 Professor J. W. Gregory— 
in places compressed; the highest blocks lying in the north-east and 
south-west axis of the land masses, so that the whole structure may 
be termed a geanticline ; the blocks initially consisting of an older mass 
of generally complex structure much denuded and largely planed, 
and concealed, over the greater part of the area, by covering strata 
which had not been disturbed before the ‘ blocking’ took place; the 
whole, since these movements, has been considerably modified by 
erosion somewhat complicated by the effects of later movements of 
uplift and subsidence. 
VI.—Tue Acer or tHE Norseman LimeEsrone, WESTERN AUS!RALIA. 
By Professor J. W. GREGORY, D.Sc., F.R.S. 
| is generally agreed that the main plateau of Western Australia 
has probably stood above sea-level since the earliest geological 
times, and has perhaps been a land area since the Archean. Marine 
deposits lie against its northern, western, and southern borders, but 
none are known upon the plateau itself; but through the depression 
of Lake Cowan Kainozoic marine deposits have extended northward 
into the Dundas Goldfield at Norseman. These marine deposits 
include a deep lead with sponges which were described by Dr. Hinde 
(Bull. Geol. Surv. W.A., No. 36, 1910, pp. 7-24, pls. i-ii1) and 
some patches of limestone which occur on the surface around 
Norseman. They have been described by Mr. A. Gibb Maitland, 
1908 (‘‘ Recent Advances in the Knowledge of the Geology of West 
Australia,’ Rep. Aust. Assoc. Adv. Sci., vol. xi, p. 153, 1906), and 
by Mr. W. D. Campbell (‘‘The Geology and Mineral Resources of 
the Norseman District, Dundas Goldfield,” Geol. Surv. West Aust., 
Bull. 21, p. 22, 1906). 
These Norseman limestones prove that at the date of their 
deposition the southern margin of the great plateau of Western 
Australia stood 1,000 feet below its present level (cf. J. W. Gregory, 
‘The Lake System of Westralia,” Geogr. Journ., vol. xlili, pp. 656-64, 
map, 1914). The date of this submergence is of primary importance 
in the history of the physiography of southern Western Australia. 
The suggestion has been made that the limestone is Pleistocene, 
and I owe to the kindness of Mr. E. 8. Simpson some fossiliferous 
fragments of the Norseman Limestone which I have examined to see 
what light they throw on the age of the rocks. The fossils are, 
however, all in poor preservation. The best preserved of the 
molluses have been kindly examined by Mr. A. E. Kitson, who, in 
spite of his extensive experience with the Victorian Kainozoic, is 
unable to give any very positive determination. He remarks as 
follows :— 
‘‘T have been over the fossils from the Norseman limestone, but 
am sorry to say I cannot recognise any of them specifically. ‘They 
all are too fragmentary even for generic determination. Several 
appear to be fragments of Cardita; others of brachiopods. Two 
small ones look like young gasteropods (WVatica?), but they may be 
adult forms of an identifiable species that I do not know. Two 
appear to be Turritellas. Speaking from memory of TZurritella 
