76 
The Queensland Naturalist 
November, 1943 
volcanic rocks included in the Walloon strata very sugges- 
tive of contemporaneous volcanic action. 
The story after the W alloon or Jurassic period is 
very confused in this area. Perhaps some day we will be 
able to puzzle it out. There are no known marine creta- 
ceous strata following the Jurassic here; if they ever ex- 
isted they have been removed. The later deposits of Cain- 
ozoic age, which we usually call the Tertiaries seem to 
occur as freshwater sediments in basins in the mesozoie 
rocks. There had been much denudation and in some 
places much faulting and folding of the mesozoie strata, 
though nothing comparable with what had happened to 
the “ Brisbane Schists’ ’ prior to the laying down of the 
Ipswich coal-measures. 
There were two major faults, West Ipswich and 
D ’Aguilar and some folding with subsequent denudation 
prior to the tertiary deposits which lie unconformablv on 
the mesozoie beds. The tertiaries themselves have since 
been faulted and folded to some extent. 
Just as, owing to lack of fossil evidence we are un- 
certain of the age of the “schists,” so geologists are uncer- 
tain where to place in the time scale the isolated basins 
of tertiary deposits, the fossils found sufficing only to 
refer them to the Cainozoic or Tertiary age. 
Associated with the Tertiary beds in the Brisbane 
region are flows of a peculiar kind of basalt, as at Bald 
Hills, Runcorn, Cooper’s Plains and Bundamba. 
This basalt occurs at low levels, and extends along the 
shores of Moreton Bay from Redland Bay to Lytton and 
occurs again at Humpybong. It lies on the denuded up- 
turned edges of the West Ipswich fault and seems to 
flood round the mesozoie hills at Manly. In two places 
bores have penetrated through 900 feet of it, one at Bun- 
damba and the other at Birkdale on the shore of the Bay. 
This is very puzzling, for there is no possible connec- 
ting valley between these two points where the lava flow- 
ed, now so far below sea level. 
If we now come to consider the other basaltic rocks 
which occur to the south and south-west, Tamborine 
Mountain is perhaps the nearest of them to Brisbane. 
They are of different rock types from the basalt associated 
with the Tertiaries mentioned above and they occur 
largely as cappings of mountains or pleateaus. These 
lavas were poured out in extensive and oft-repeated flows 
