500 THE DISTRIBUTION, ETC., OF ALKALINE ROCKS, 



continued uninterruptedly until the close of the Cretaceous. We 

 can explain away the difficulty either by regarding the Australian 

 Triassic basins as epicontinental seas, or by falling back on Teni- 

 son- Wood's hypothesis that our Triassic sediments are products 

 of subaerial degradation (windblown, &c), both of which suppo- 

 sitions are probably well-founded for certain areas. 



Again, the Eocene was in our continent, generally speaking, a 

 period of uplift which continued through the Miocene and 

 Pliocene. Australia dates from the Eocene. Likewise North 

 America, South America, Africa and Asia assumed at that time 

 a configuration resembling that which they retain at present. 

 The Andes, the Himalayas and Hindoo-Koosh Mountains and the 

 Alps commenced to form in that period. 



The Eocene, it appears, was an era of compression, folding, 

 faulting and mountain-building in many regions, and of contrac- 

 tion, faulting and senkungsfeld-formation in other parts of the 

 world. In very many regions most intense volcanic activity 

 prevailed. There were compensating movements of elevation 

 and subsidence, continued oscillations, and instability everywhere. 

 Volcanic extravasation was especially great along the borders of 

 those Mesozoic basins which were then undergoing regional uplift 

 (or relative uplift). 



If we now consider for a moment the character of the lavas poured 

 out at this time, we find as a most noticeable feature that they 

 were frequently of an alkaline nature, belonging to what the 

 Rosenbusch school of penologists call a foyaitic magma; we see 

 also that such lavas were poured out largely along Eocene fracture 

 lines adjoining Mesozoic basins of sedimentation. 



In Australia these features are exemplified, as will be explained 

 later, by the alkaline lavas of East Moreton, Mt. Flinders, 

 the Nandewars, the Warrumbungles, Mittagong, Dubbo, the 

 Canoblas, and Mount Macedon. 



In the Abyssinian region, which resembles the Australian to 

 a remarkable extent, we find the same features.* 



* Min. Mag. Feb. 1903, Vol. xiii. No, 61; and Min. Mag. Vol. xii. No. 57. 



