72 presidbnt's address — section c. 



tuffaceous beds in the Desert Sandstone of Queensland, 

 which is considered to be of Upper Cretaceous age, there is 

 no evidence, as far as the author is aware, of contemporaneous 

 volcanic action in Australia in Mesozoic rocks of Jurassic or 

 of Cretaceous age. 



During these long periods of time the western portions of 

 New South Wales and Queensland were slowly subsiding 

 under the waters of the Cretaceous ocean, which may have 

 extended from the Gulf of Carpentaria on the north south- 

 wards at least as far as Nevertire, in New South Wales. 



In some parts of Queensland the subsidence may have been 

 as much as 3000 feet, and in New South Wales upwards of 

 1000 feet. At the close of the Mesozoic era subsidence 

 ceased, and a re-elevation of the Western Districts com- 

 menced. 



In Tertiary time there was a great renewal of volcanic 

 activity in Queensland, New South Whales, and Victoria. 



In New South Wales eruptions commenced in Eocene 

 times. In the tin-bearing districts of New England, as at 

 Tingha and Vegetable Creek, a number of small volcanoes 

 broke out on north-west and south-east lines, and built up 

 composite cones of lava and tuff to a height of from 100 to 

 about 500 feet, and remains of the Eocene flora of that epoch 

 became buried under the contemporaneous volcanic rocks. 

 While eruptions were taking place in New South Wales 

 during early Tertiary time, on a rising land surface, Victoria 

 was undergoing subsidence, the land being depressed during 

 the Oligocene or Miocene periods 700 feet below its present 

 level. 



In Victoria a few thin volcanic rocks are interstratified with 

 the Miocene sedimentary beds, but as far as at present known 

 there are no equivalents of the Eocene volcanic rocks of New 

 South Wales developed in Victoria. The greatest volcanic 

 activity, however, in the latter country took place during the 

 close of the Miocene period. 



No well-marked points of eruption, however, of these lavas, 

 which are basalts, and termed "Older Volcanic" by the 

 Victorian geologists, have yet been discovered. This absence 

 of relics of the Miocene volcanoes of Victoria is probably 

 due to the great amount of denudation to which the Miocene 

 basalts were subjected, as in the Victorian basalt flows, termed 

 "Newer Volcanic," which commenced in the Pliocene and 

 extended down to probably recent geological time, there are 

 numerous and well preserved volcanic cones and craters. 



