November, 1943 
The Queensland Naturalist 
75 
present West. 
In Western Queensland, and also in the Maryborough 
district, the freshwater deposits were succeeded by marine 
strata, the sea apparently invading in cretaceous times 
areas previously freshwater. 
The area now occupied by, or underlain by Mesozoic 
freshwater beds is very large, extending from the south- 
ern border to the Gulf of Carpentaria, and up the western 
side of Cape York Peninsula, and from Brisbane to the 
western border. Along the Eastern coast it extends from 
Brisbane to beyond Bundaberg on the eastern side of the 
belt of palaeozoic rocks which further north come right to 
the coast. This gives the suspicion that the sandstones 
may continue beyond Sandy Cape under the sea to the 
east of the palaeozic rocks and be continuous with the 
sandstones of Cape York Peninsula, as is the case on the 
western side. 
Even without this possible very large extension of 
area under the sea, the present exposed area of mesozoic 
rocks is very large and of considerable thickness, — a few 
thousand feet. 
This is an immense volume of material, derived in 
mesozoic times from the denudation of the exposed areas 
of older rocks, on the west probably from the vast areas 
of ancient rocks further west, but in the east no doubt 
trom the palaeozoic rocks forming the backbone of 
eastern Queensland. 
To come back to the south-east corner of Queensland 
where we are holding our excursion, the change from the 
Ipswich and Bundamba to the Walloon coal-measures 
seems to have been accompanied by a change of conditions 
for the strata become more calcareous or saline, and the 
coal seams are of a different character. There is also a 
slight change in the flora to the Jurassic rather! than 
Triassic types though many are common in both forma- 
tions. 
The change in rock type and perhaps also in the flora 
may be due to a change in climate or to a change in (the 
material from which the rocks were derived. Personally, 
I fancy the latter is the likely explanation, and that there 
were probably volcanic eruptions on the land, the denu- 
dation of which altered the character of the resulting vege- 
tation and sediments. There are some sections showing 
