BY E. O. MARKS, B.A., B.E. 141 



mentions their having been obtained beneath basalt — 

 a record to which the writer's attention was kindly drawn 

 by Mr. E. C. Andrews. 



In describing the " porphyritic " rocks, Sir A. C. 

 Gregory considered them to be older than the basaltic, 

 which have cut through and overlie them. He also con- 

 sidered them to be later than the " carbonaceous series,'* 

 which had not then been classed as of Trias-Jura age, but 

 included with them the Brisbane rock. 



In 1887 and 1889, Mr. W. H. Rands, working in 

 Brisbane and in the Logan and Albert districts, determined 

 the Brisbane '' porphyry " to be a trachytic tuff, lying at 

 the base in this locality at any rate, of the Trias-Jura 

 system. He encountered at Walton (now Woodhill), 

 a trachyte which he considered to be contemporaneous 

 with the coal measures in which it occurs. The basalt of 

 Tambourine Mt. and the Macpherson Range, found both 

 on the Trias-Jura beds, and on the underlying schists. 

 Mr. Rands considered to be later than the coal measures 

 and Woodhill trachyte, but older than the desert sandstone 

 (Upper Cretaceous), to which age he ascribed a sandstone 

 resting on the basalt and containing pebbles thereof, at the 

 head of Nerang River. 



Dr. Jack, in his Geology of Queensland, pointed out 

 that it is a mistake to suppose that the volcanic rocks 

 consist of only one continuous series, but expressed the 

 opinion that the basalt of Tambourine is not necessaiily 

 of later age than the Woodhill trachyte, since it lies on 

 strata considerably lower in the Trias-Jura system than 

 the horizon at Woodhill. Dr. Jack considered that the 

 basalt of the Toowoomba Range is contemporaneous, 

 though locally uncomformable with the Trias- Jura rocks, 

 beneath the upper portion of which he supposed them to 

 dip to the west, thus accounting for the absence of an 

 escarpment in that direction to correspond with that forming 

 the Main R^nge. The basalt at Ipswich he also thought 

 to be contemporjaneous with the coal me^asures there, but 

 this has since been shown of more recent origin. The 

 basalt of Clifton and elsewhere appearing to occupy local 

 hollows in the stratified rocks, he himself considered to be 

 later age than the Trias-Jura. 



