110 PROCEEDINGS OF THE ROYAL SOCIETY OF QUEENSLAND. 
ditferent fault blocks may not represent identical horizons, 
the total thickness of Permo-Carboniferous volcanics which 
have been extruded in the area may far exceed this amount. 
The interest in this series was in part petrological, for 
many very beautiful examples of spheroidal and fluidal 
structures have been observed, but this intrinsic interest 
was surpassed when sufficient evidence had been accumu- 
lated to definitely indicate that the series was Permo- 
Carboniferous in age, and interbedded with fossiliferous 
Upper Marine strata. 
The only other area where volcanics of this age are at 
all extensively developed in Australia, so far as the authors 
are aware, is in the Southern Coalfield area of New South 
Wales, and there the rocks are in marked contrast 
chemically with those under discussion. In the Drake area 
two series of lavas and tuffs have been described, both of 
which resemble in some respects those of the Silverwood- 
Lucky Valley area, but they are regarded by Andrews’ as 
of Lower Marine, Permo-Carboniferous age. 
(II.) THE SILVERWOOD-LUCKY VALLEY AREA. 
Faulted down into the Silverwood Series of Andesitic 
Tuffs and Radiolarian Cherts of Devonian age, there 
are four blocks of different sizes, composed of Permo- 
Carboniferous material. Three of these are largely made 
up of volcanic rocks, while the fourth contains much 
tuffaceous matter, but little in the way of lava flows. 
These blocks have been termed by the authors— 
(1.) Eight Mile Block, 
(ii.) Tunnel Block. 
(ili.) Stanthorpe Road Block, 
(iv.) Condamine Block. 
The first two have had a pronounced effect upon the 
topography, as there is a marked parallelism between the 
strike of the rhyolite and dacite flows and the backbone of 
the ridges. Apart from the areas of hornfels around the 
margins of the intruding granite of late Permian times, 
these areas of Permo-Carboniferous lava flows mark the 
Neen ee ee TEE 
1 Report on Drake . . . N.S.W. Geol. Sur. Min. Res., No. 12., p. O, 
