400 PROCEEDINGS OF SECTION C. 



associated with sheets of melaphyre, as described by Mr. R. A. F. 

 Murray, Government Geoloj^ist of Victoria.* 



The quartz -felsites of Rock Creek, whether plutonic or volcanic, 

 are certainly older than the diabasic and felsitic tuffs interstratified 

 with the Rhacopteris beds of the Stroud district, in New South 

 Wales, the latter rocks at the time of the meeting of the Associa- 

 tion at Hobart being the oldest known representatives of the 

 volcanic division in New South Wales. The credit of this 

 discovery belongs to Mr. W. Anderson, late of the Geological 

 Survey of New South Wales. With the exception of the above 

 felsites no important additions have of late been made to our 

 knowledge of the volcanic rocks of New South Wales, as far as 

 the author is aware. In Queensland Mr. R. L. Jack, F.G.S., the 

 Government Geologist, has supplied me with information, which 

 enables me to make important additions to my previous summary 

 of the volcanic rocks of that colony. In the valley of the Reid 

 thick beds of brecciated volcanic ash are interstratified with Pre- 

 Devonian greywackes. In the Burdekin formation (Devonian) 

 reddish-purple shales are somewhat extensively developed, and 

 may indicate eontemporaneous volcanic action. In the Gympie 

 series a chloritic rock with amygdaloidal cavities, probably an 

 " amygdaloidal diabase," has been described by Mr. W. H. Rands, 

 This lava, or tuff, was probably of Carboniferous age. In the 

 Star beds (formerly known as the Dotswood beds), probably of 

 Carboniferous age, but grouped under the broad term Permo- 

 Carboniferous, Mr. R. L. Jack has recorded the occurrence of 

 interbedded amygdaloidal porphyrites. In my previous paper due 

 importance was not assigned to the strong evidence of contem- 

 poraneous volcanic action at or near the base of the Ipswich coal 

 measures (Triassic) near Brisbane (v. Plate XV., section 3). Mr. 

 Jack recently conducted me over a few of the best sections 

 of these volcanic rocks near Brisbane, and I quite concur in the 

 vieAvs already expressed by himself and Mr. W. H. Rands, F.G.S., 

 that they are certainly contemporaneous tuffs, probably subaerial. 

 This rock has been well described by Mr. W. H. Rands,f and I 

 cannot do better than quote his description : — " A rock occurs 

 nmning in a north and south direction through Brisbane. It is a 

 good bviilding stone, and has been employed in most of the 

 principal buildings. ... It has hitherto been classed as a 

 porphyry, which has been intruded into the micaceous schists. 

 Were this the true nature of the rock one would expect to find the 

 schists in its vicinity altered, in much the same manner that we 

 find them changed to hard lydianised slates, where they border on 

 the granite. No such change is seen, although the junction of this 

 rock with the schists is visible in several cuttings in and about 



* Geology and Physical Geography of Victoria, pp. 66-69. 



+ Report to accompany Geological Map of the City of Brisbane and its Envinns, by 



William H. Rands, .\ssistant GoTerament Geologist. Government Printer, Brisbane, 1887. 



