BY H. C. RICHARDS. 147 



log. As described earlier, at Upper Cliristmas Creek, a 

 large included mass of eoal-bearing shale was found 

 included in the agglomerate. The cliffs of compact pyro- 

 clastie material which occur frequently on the valley sides 

 all through the southern area are very characteristic, and 

 when examined are seen to have an imperfect columnar 

 structure and to be weathered out into caves. These caves 

 are often several feet in diameter, and on the weathered 

 surface, the angular and subangular included fragments 

 of rhyolite &c., generally a few inches in diameter, stand 

 out as a result of their superior weathering properties. 



(iv.) Trachytic Rocks. 



These are found occurring in much the same way as 

 the rhyolitie rocks, but they have a much more limited 

 occurrence. The most extensive development is along the 

 Main Range from Wilson's Peak to near Mount Castle, 

 and they seem to have resulted from a fissure eruption. 

 Along a line from Mount Greville to Redbank Plains they 

 occur at Blount Greville, Blount Edwards, Mount French, 

 Mount Flinders, and at Redbank Plains. Isolated peaks 

 occur in the Esk and Glass House Mountains districts, 

 and there are also areas of trachytic rocks at Woodhill and 

 Cainbable Creek. All these occurrences have probably 

 resulted from central eruptions. 



The trachytic rocks have been dealt with at length by 

 Dr. Jensen in several papers, but he has given them a more 

 widespread distribution than they really have. He states^^ 

 that he has " good reason to believe that the whole of 

 the Little Liverpool Range from Wilson's Peak to the 

 Rosewood District is mainly trachytic"; also, that "the 

 culminating peaks of the range like Spicer's Peak, Mount 

 Mitchell, i\lount Cordeaux, Mount Huntley, Mount Roberts, 

 &c., are apparently of trachytic composition." Jensen also 

 states^^ that " At Spring Bluff, betw^een Helidon and 

 Toowoomba, trachytes underlie basalts, but not having 

 examined sections, I cannot say whether they are very 

 alkaline or not." 



'•"■ Jensen, Proc. Linn. Soc, N.S.W., xxxiv., p. 73. 

 =" Jensen, Proc. Linn. Soc, N.S.W.. xxxiii., p. 576. 



