SOUTH VICTORIA LAND ROCKS OF ATLANTIC TYPE 305 



has summed up the characteristics of the Atlantic and Pacific provinces re- 

 spectively. 



Iddings in 1892 noticed the remarkable geographical distribution of rocks of the 

 Atlantic and Pacific type, but considei-ed the distinction of alkali and sub-alkali 

 groups too indefinite to be made a basis of classification. In 1896 Harker emphasized 

 the vast importance of these two great world provinces of eruptive rocks, their 

 distribution corresponding to the Atlantic and Pacific types of coast-line, as defined 

 by Suess. 



Becke in 1903 adopted a similar grouping. In Harker's map, showing the limits 

 of the upper part of the Pacific petrographical region for the Tertiary and Recent 

 igneous rocks, he draws the line of demarcation just to the north of Australia, 

 leaving Australia in the Atlantic province, and New Guinea in the Pacific ; thence 

 carries it midway obliquely through the southern island of New Zealand, so as to 

 include the alkaline rocks of Dunedin in the Atlantic province. He makes the 

 following statement in regard to Antarctica : — 



"Farther south characteristic alkali rocks appear in South Victoria Land, and 

 the scanty data make it probable that the greater part of the countries within the 

 Antarctic Circle should be attached to the Atlantic region. It is likely, however, 

 that a tract about South Georgia, to the south of South America, should be separated 

 and included with the Pacific." 



Reiter * on tectonic considerations proposes to include " the Antarctic coasts and 

 islands from the Balleny Islands to the South Orkneys with the Pacific type, 

 relegating the remainder to the Atlantic." 



Dr. G. T. Prior f states, " these volcanic rocks of South Victoria Land belong 

 undoubtedly to the Atlantic group, although they occur along the coast which has 

 been described as distinctly of the Pacific type." To which he adds this footnote: — 



"While these pages were in the jiress Band ii., Teil 1, 'Deutsche Sudpolar 

 Expedition, 1901-3,' was published; in No. 2, ' Geologische Beschriebung des Gauss- 

 berg,' by E. Philippi, the author brings forward arguments in fiivour of the view 

 that the coast of South Victoria Land is really of Atlantic type." 



Atlantic. Pacific. 



Microperthitic and crvtoperthitic intergrowths Zonary banding of felspais frequent. 



frequent. 

 Felspathoid minerals often found (leucite, nephe- Felspathoid minerals not found. 



line, sodalite, primary analcinie ; also melilite). 

 Quartz confined to the more acid rocks. Quartz not only in acid rocks, but also in many 



intermediate ones. 

 Pyroxenes and amphiboles often include soda- Pyroxenes represented by augite, diopside, and the 



bearing kinds. rhombic group ; amphiboles by common horn- 



blende. 

 Mica and garnets of common occurrence. Micas not common except in the more acid rock. 



* Die Sudpolarfrage und ihre Bedeutung fiir die genetische Gliederung der Erdoberflache (1886). 



t National Antarctic Expedition, 1901-4, Geology, p. 140 



