74 
The Queensland Naturalist 
November, 1943 
volcanic ash and to form the base of a very exten- 
sive and important geological formation. Yet this is actu- 
ally what we have exposed in some of our city quarries. 
It was a surface on which large coniferous trees grew in 
abundance, the silicified trunks' of which are a notable 
feature in the exposed sections. 
It was an irregular surface, of which the tuff and the 
Ipswich strata first filled the valleys, the later strata ex- 
tending beyond, or overlapping the lower beds like a flood, 
so that we find either the basal beds or higher strata rest- 
ing directly on the schists in an ‘ 4 uncomf ormable 9 ’ junc- 
tion. 
Subsequent changes in elevation and consequent de- 
nudation of the mesozoic strata has exposed again areas 
of schist once covered, exposing hills of schist like islands 
surrounded by the sea of sandstones and shales. Only 
in a few places does the present boundary line appear to 
have been determined by later faulting, though the whole 
area has been much faulted. 
The chief interest for our present purposes is the 
time-gap which the unconf ormable junction represents 
between the deposition of the “schists” and the deposi- 
tion of the mesozoic strata. In that interval the “schists” 
were folded and crumpled, and to a varied degree meta- 
morphosed, then exposed to denudation and on their 
worn-down surface was deposited the later formation. 
Over a very large part of Queensland a long period 
of fresh-water sedimentation now followed, in which the 
Ipswich coal-measures, the Bundamba sandstones and the 
Walloon coal-measures followed in continuous succession. 
The coal-measures were vegetated swamps alternating with 
deposits of sand and mud, probably carried by floods. 
Dinosaur footprints in the roof of a coal seam at Rose- 
wood show that the animal walked about in the soft vege- 
table matter just before it was covered by a deposit of 
silt which made a cast of the prints. In other places 
fossilised tree-stumps growing in situ in the sands show 
that the sands were not deposited in deep water. Rather 
dal these suggest a condition something like our present 
western Queensland where the rivers in flood spread out 
over wide areas of level plain depositing the sediments 
brought from the higher country, only with the difference 
of course, that the climate was much less arid than our 
