VOLCANIC ACTIVITY IN SOUTHERN QUEENSLAND. i11 
highest country. In the third block there is little in the 
way of lava flows, and there is no apparent effect upon the 
topography of the-area, but in the fourth block the highest 
eround in the neighbourhood is marked by the interbedded 
rhyolite tuffs, and a very close relationship exists between 
the direction of the ridge and the strike of these tuffs. 
(1.) Eight Mile Block—This is an area of eight square 
miles, and is situated around and about the Eight Mile 
Range and the Rhyolite Range. The former range is 
so-called locally on account of its distance south of 
Warwick, while the latter, which runs N.N.W. from the 
Hight Mile Range, has been named by the authors on 
account of its petrological nature. 
This block is composed of mudstones, sandstones, grits, 
and conglomerates containing fossils belonging to the 
Upper Marine stage, and interbedded with them are 
mudstones containing Glossopteris and Noeggerathiopsis. 
Contformably bedded above the fossiliferous sediments there 
are rhyolites, dacites, andesites, and basalts, and with these 
are rhyolitic and dacitic tufts. 
The rhyolites and dacites much preponderate over the 
andesites and basalts, while the sequence appears to have 
been from earliest to latest—rhyolite, dacite, andesite, and 
basalt. Interbedded with the rhyolite and dacite flows are 
large thicknesses of the tuffs. 
Approximately two-thirds of this block appears to be 
composed either of lava flows or of tuffs, so that we have 
between 5 and 6 square miles covered by their outcrops. 
(7.) Tunnel Block—This is a wedge-shaped block 
about 2 miles long by $ mile wide, and is situated north 
of the railway tunnel about 14 miles north-west of Cherry 
Gully Railway Station. The length, which is a little west 
of a north-south line, corresponds to the strike of the flows 
and tufts. In its petrological character it much resembles 
the material in the Rhyolite Range further to the north, 
and it is composed almost entirely of rhyolite flows, some 
of which are porphyritic and others spherulitic and fluidal. 
Conformably bedded below the lava flows are mudstones 
eontaining Productus brachytherus and shallow water 
sediments closely comparable with those below the volcanic 
material of the Eight Mile Block, so that the age of this 
