320 T. G. TAYLOR AND D. MAWSON. 
the south the rock becomes darker and harder and has been 
mistaken for a basic breccia. In sections, however, it is 
seen to be composed largely of fragments of trachyte. The 
south-west end has been quarried for light colored rock of 
a tuffaceous character. On the north-west slope more 
vesicular lava (much decomposed) occurs. (See Section IV. 
No. 4.) 
Basalt 
Gr: Southern Ra,  Neck| 
Scoriaceous 
one — 
(VelTeanic pipe) 
2000 ft 
Fig. 5.—Section A B C (see fig. 4) showing small volcanic necks to the 
west of the Gib. 
This cone probably does not represent the remains of the 
crater of the Gib, but is the result of material which has 
welled up from a laccolite some hundreds of feet below. 
The large area of sandstone to the north of this cone has 
been upheaved to a considerable extent as shown by the 
dip of the strata. It is worthy of note that the fragments 
included in the tuff resemble (when sectioned) the rock 
quarried from a small hill about one and half miles away 
on the northern slope of this same elevated sandstone area. 
This would tend to show the existence of amass of eruptive 
material below the sandstone, in form of a laccolite, extend- 
ing from the quarry on the north to the tuff cone on the 
south. 
