ANTARCTIC ADVENTURE AND RESEARCH 



Atlantic type — microperthitic intergrowths in fel- 

 spar, felspathoid minerals, quartz only in acid 

 rocks, soda-bearing amphiboles, etc., mica and 

 garnets common. 



Pacific type — zoned felspars, no felspathoids, quartz 

 in intermediate rocks also, diopside and common 

 hornblende abundant, mica not common except in 

 the more acid rocks. 



Quartz dolerites, as already stated, occur in the form 

 of huge sills, which have penetrated both the granites 

 and the Beacon Sandstone series throughout South Vic- 

 toria Land. The rock in its amount of potash closely 

 approaches to essexite. The commonest pyroxene is 

 hypersthene but enstatite is also present. Interstitial 

 patches of granophyre are common, and the whole 

 facies of the rock resembles that forming the sills of 

 Tasmania. The Tasmanian occurrences have intruded 

 Trias- Jura rocks and are themselves intruded by ter- 

 tiary basalts. The Antarctic quartz-dolerites may 

 therefore also be classed provisionally as Cretaceous in 

 age. Somew^hat similar rocks in South Africa are per- 

 haps a little older. The famous Palisades near New 

 York are stated by Dr. Prior to be of a very similar 

 character. (See Figure ii.) 



Kenytes and Basalts. — These volcanic rocks belong 

 to a series of Tertiary eruptions, and are found very 

 abundantly along the west coast of the Ross Sea, espe- 

 cially on Ross Island, which is almost exclusively vol- 

 canic in composition. There is a series of trachytes on 

 this island consisting often of sanidine and aegyrine. 



1 02 



