BY H. I. JENSEN. 73 



basalts liave been blocked on the east by the trachytic range. 

 That the focus of the volcanic activity is near the core of the 

 range is seen by beds of breccia containing blocks up to 24 

 inches in diameter, occurring half-way up. The forest on the 

 breccia-formation consists of Casuarina, Blood wood(^. corymbosa), 

 Blue Gum (E. tereticomis), Stringy bark (i?. acme^iiozV/es'), Tallow- 

 wood {E. microcorys), Moreton Bay Box (Tristania conjerta), 

 Apple [Angophora subvehitina), Jronbark [E. melanophloia), and 

 Grass-tree {X author rhcea)* 



The culminating peaks of the range, like Spicer's Peak, Mt. 

 Mitchell, Mt. Cordeaux, Mt. Huntley, Mt. Roberts, &c., are 

 apparently of trachytic composition; and almost all the eastern 

 fall of the range is essentially trachyte, but the western fall and 

 the top of the range (excluding the peaks) have considerable 

 patches of bftsalt. I have good reason to believe that the whole 

 of the Little Liverpool Range, from Wilson's Peak to the Rose- 

 wood District, is mainly trachytic; and that this range is built 

 up along a great fault running N.N.W.-S.S.E., following a line 

 which, in Triassic and Cretaceous times, played a similar part to 

 that probable fault running from Dubbo to Narrabri in New South 

 Wales. During Triassic times sedimentation took place mainly 

 to the east of this line; during Cretaceous time subsidence took 

 place to the west of it, with the result that sedimentation 

 took place mainly over this part of the country. In Post- 

 Cretaceous times a great horizontal uplift took place, or 

 perhaps, as Suess would have it, a negative movement of 

 the sea ; this was followed by faulting, which led to the 

 formation of a trough in which che Ipswich Formation is pre- 

 served. This trough would be encompassed between two 

 faults, A and D, the one, D, separating the subsided area from 

 the Brisbane schists, and A, separating the area from the stable 

 or elevated Darling Downs. (Figs. 2 and 3.) Had the downthrow 

 of the Ipswich Measures been earlier, we should have expected 

 more Cretaceous sediments deposited over the Ipswich Measures. 



* I am indebted to Mr. McGrath for the identification of many of the 



forest-trees. 



