92 
should be held, for there is a good deal of evidence that the sea 
has extended over the greater part of the State not only once, but 
repeatedly since the very ancient rocks forming our goldfields were 
first exposc<I as a land surface. These oldest rocks, taking all the 
Pre-Cambrian ones together, are uncovered at surface at the pre- 
sent day ill the Central and Eastern Goldfields, hut in the greater 
part of the northern half of the State they are overlain by the much 
vounger Nullagine formation, and there a])pears to be at least a 
strong possibility that this reapiiears in the Stirling and Eyre 
Ranges in the South. There is quite a considerable degree of pro- 
babilitv that the whole of the State has been covered by the Nulla- 
gine formation, lying upon a previously planed-down surface of the 
Prc-Cambriaii rocks. Subsequent erosions have removed the Nul- 
lagine rocks over huge areas. After the formation, upheaval, and 
land-erosion of the NTillagine beds there has again been depres- 
sion of large parts of the area of the State below sea level when 
the Carboniferous formation was laid down, which must have ex- 
tended over a very large portion of the State, as we still find large 
areas of it in districts so far apart as the Kimberley, Gascoyne, 
and Collie mineral fields. The elevation to which these beds ex- 
tend suggests that when they were laid down there was much 
probability that a great deal of the rest of the State was also 
submerged. Then still later there must have been submergence 
of large portions of the State when the Meso?:oic '■•x'ks were laid 
down which wc find from Gin Gin northwards to beyond Gerald- 
ton, uj) to considerable elevations, and the limestones of the Eucla 
plateau, found u]) to heights of about 1000 feet above sea level, 
point to a probably rather later period of sul)sidence and marine 
sedimentation over an immense tract of country. When the sea 
came inland to the northern edge of the Eucla limestone area it 
may well have flooded a great part of the liastern goldflelds which 
are now below the 1000 feet level, and a comparatively slight fur- 
ther subsidence would have carried it over practically the whole of 
the Central and Eastern Goldfields if the relative levels of the 
various districts remained the same then as at present. The 
Government Geologist has also described limestones, proliably of 
Tertiary age. occurring at a high level near the head of the Oak- 
over River in the Ifllbara Goldfield, which would indicate a sub- 
sidence in Tertiary times sufficient to bring the sea a long way 
inland at that point. 
It is seen therefore, that there is positive evidence of suc- 
cessive invasions of the sea well into what is now the interior of 
Western .\ustralia. up to the Cretaceous and probably the Eocene, 
or even later periods, and there is no reason to .sup])osc that the 
limits as we now find them of the formations then laid down were 
the extreme limits to which the sea waters extended. It is much 
more likely on the contrary that the sea extended over a great 
