504 THE DISTRIBUTION, ETC., OF ALKALINE ROCKS, 



be realised by a study of their contours and of the surrounding 

 peneplain. In the Dunedin district of New Zealand the same 

 relationships occur. In Antarctica, too, alkaline rocks, trachytes, 

 kenytes, and trachy-dolerites have been noticed in abundance,* 

 and here too in association with extremely old schists, granites 

 and gneisses. 



These facts are significant, as indicating that alkaline rocks 

 are, in the true sense of the word, continental rocks. They are 

 intimately associated with continental areas of great permanence 

 (like Africa), and with broken down faulted relics of continents 

 (like Bohemia, Madagascar, Atlantis and Antarctica). 



The Association of Alkaline Rocks with undisturbed 

 Mesozoic Beds. 



In the subsequent discussion of the various alkaline regions it 

 will be seen that very frequently alkaline intrude horizontally 

 bedded or gently inclined Mesozoic beds, particularly the Triassic 

 and Jurassic. 



The intruded Mesozoic sediments have rarely been folded to 

 any extent but frequently they have been affected by great 

 block-faulting and trough-faulting. In most cases these beds 

 immediately overlie very ancient rocks. They therefore probably 

 represent mere transgressions of the sea which have invaded the 

 worn-down continents in Mesozoic times. 



In Europe, especially in Wiirtemburg and Bavaria, in the 

 areas where alkaline rocks are very plentiful, the surrounding 

 Mesozoic rocks (Triassic) are frequently tilted at high angles, but 

 the tilt is caused by block- and trough-faulting, never by folding. 



In Asia the alkaline rocks occur on the borders of areas over 

 which Mesozoic rocks lie horizontally. In Arabia horizontal 

 Jurassic rocks overlie a Carboniferous transgression under which 

 the Azoic complex is met with. The same holds true for Socotra, 

 Abyssinia, and Somaliland, and for Africa generally. For 

 America numerous instances of the association of alkaline rocks 



* British Museum Report : Scott Expedition. Geology. 



