NOTES ON THE GEOLOGICAL AGE OF VOLCANIC 

 ACTIVITY IN SOUTH-EAST QUEENSLAND. 



By E. O. MARKS, B.A., BE. 



Read before the Royal Society of Queensland, 24tth Junej 1911. 



The follo^\dng notes have been compiled in the desire 

 of interesting members of this Society in a question on 

 which, in the past as well as in the present, very divergent 

 views have been held — namely, the question of the 

 geological ages of volcanic activity in this corner of 

 Queensland. 



A problem of this nature is always, to a geologist, 

 one of exceptional interest ; in this case, affecting as it 

 does extensive areas of coal measures, it is one which in 

 the future will possibly possess considerable economic 

 importance in addition to its scientific interest. 



A by no means small attraction is added by the fact 

 that to the varied volcanic rocks are due, entirely or in 

 part, so many of the physical features characterising the 

 landscapes with which we are familiar, such, for instance, 

 .as the Glass House Mountains, the rugged scenery of Mt. 

 Barney and its neighbours, or of Cunningham's Gap, the 

 broad rich valleys of the Darling Downs and the beauties of 

 the Tooivoomba Range, or the richly beautiful scrubclad 

 valleys, gorges and lofty plateaux which render the head- 

 waters of the Logan, Albert, Coomera and Xerang rivers, 

 a region destined to become the pleasure resort of our 

 metropolis. 



Volcanic rocks attain a very considerable develop- 

 ment in the south-eastern corner of this State, and consist 

 of widely varying types. The petrological characteristics 

 of many of the rocks have received a good deal of attention, 

 chiefly from Dr. H. J. Jensen, and further study in this 

 direction is much to be desired. It is not intended here, 



