74 PROCEEDINGS OF THE ROYAL SOCIETY OF QUEENSLAND. 
A dioritic mass occurs in the form of an inlier jutting up through 
the surrounding rhyolite in por. 757, parish of Hampden; relics of its 
former rhyolite cap form a scree on the lower flanks of its N.E. side. 
Other inliers of this nature, in each case surrounded by rhyolite, occurs 
at Dalrymple’s Lookout (this should not be confused with Mt. Dalrymple 
which is many miles from this point) and at portion 648 and section 60, 
both in the parish of Hampden. 
Quartz diorites occur at Dalrymple’s Lookout, portion 11, Green- 
mount, also at portion 661, parish Abingdon, and the E. side of Antoney’s 
Crossing, S.W. 'of portion 534, parish Abingdon. These also occur at 
Homebush Lookout, portion 441, parish Eton, Burgess’ Quarry, portion 
1464, parish Abingdon, White’s Ridge, portion 1088, parish Abingdon, 
and (probably) Hogan’s Ridge, portion 1302, parish Abingdon; also 
the Quarry at Newbury Junction. 
Basic Tuffs. 
An area from portion 1547, parish Mia Mia, past portion 989, parish 
Hamilton (in the river bed near H. Rowe’s), at McGregor Creek Bridge, 
Toby Creek Bridge, The Dingle (E. of Marian), Reeves Creek Bridge, 
portion 1274 parish Hampden and the mouth of Two-Mile Creek — all 
show a friable, basic igneous tuff which is easily eroded or weathered 
and abounds in brecciate ejecta. These always occur with dioritic 
material and frequently intrusions of felspar porphyry type are 
associated with them. ‘The exact relationship however could not be 
explained on the data available. 
This felspar porphyry which has a characteristic appearance also 
occurs on a 'ridge just N.W. of Marian and on Hardwick’s Ridge, E. 
of portion 1475, Parish Abingdon. 
Rhyolites. 
These rocks are best and most extensively developed in a belt up 
do 3 miles wide on the north-western side of a line from Mt. de Moleyns 
through Milton’s Knob, Banaghan’s Hill, The Leap and along Reliance 
Creek until they give place to the diorites referred to above which extend 
from here to the coast. S. of the river rhyolite caps the Green Knoll 
Quarry — of the same general type as that which is to be seen at The 
Leap. It also occurs in portion 641 Greenmount, E. of the Yellow 
waterhole, and N.E. bf portion 1235 Homebush and a similar type at 
the Grass-tree Gold Mine N.E. of Sarina. 
The cutting at The Leap and the quarry at Green Knoll especially 
seem to indicate the following succession — (a) the intrusion into the 
Bowen Series of the diorite, followed by ( b ) the overflowing of these 
rocks by several sheets of rhyolite (not necessarily contemporaneous). 
Good examples of these rhyolite flows may be seen in the cuttings 
between The Leap Railway Station and The Leap; while the general 
sequence is best seen at Green Knoll Quarry. This rhyolite is frequently 
friable in nature. 
