494 THE DISTRIBUTION, ETC., OF ALKALINE ROCKS, 



New England district (Carboniferous and Permo-Carboniferous); 

 the rhyolites and breccias of Barraba and Maule's Creek near the 

 Nandewar Mountains (late Carboniferous); the rhyolitic lavas 

 of Pokolbin and the basic lavas of the Kiama-Jamberoo area 

 (Permo-Carboniferous). 



Following close upon the Silurian period of subsidence, and 

 preceding the late Devonian period of continental extension we 

 notice also in early Devonian times an era of intense volcanic 

 action. In this period immense quantities of rhyolite were 

 poured out in Britain; the brecciated conglomerates of the Old 

 Red Sandstone belong to this series. In Australia, in the same 

 period, we had the rhyolitic extrusions of the Snowy River por- 

 phyries, the Yass rhyolites, the Jenolan granites (1), the Bathurst 

 granite (*?), the Tamworth rhyolites and rhyolitic tuffs, and pro- 

 bably some of the granite of the Mooubi Ranges. The biotite 

 granites of Kosciusko probably belong to this period. 



During the late Permian, the Triassic and the Cretaceous, 

 Australia, like many other parts of the world, experienced a rest 

 from volcanic activity. In the late Cretaceous again commenced 

 a period of intense vulcanicity which lasted well into the 

 Tertiary. 



Not only in Australia do we find the Triassic and Cretaceous 

 to have been periods in which shallow epicontinental seas 

 developed and the Eocene a period of incipient volcanic activity, 

 but in the United States, Brazil, Africa (East), and in Central 

 Eurasia analogous conditions prevailed at the same time. In 

 parts of Europe the era of epicontinental seas and the period of 

 epeirogenic movements commenced somewhat earlier. Thus, in 

 Tyrol gigantic igneous intrusions and volcanic extravasations 

 took place in the late Mesozoic, and this era was, from that time 

 until the final uplift of the Alps, the scene of repeated oscillations.* 



Generally speaking the commencement of a period of volcanic 

 disturbance was not coincident all over the earth, but would set 

 in in some regions earlier than in others. Likewise, such a 

 period would end earlier in some regions than in others. Thus t 



* Suess, ' La Face de la Terre,' Tome iii. 



