VII 



NDRANDRAMEA DISTRICT 



107 



pyroxene have disappeared, the sand 

 being largely made up of magnetic-iron 

 grains mixed with fragments of plagio- 

 clase. 



The Extent of the Area of 

 Acid Andesite Rocks in the 

 NDRANDRAMEA DISTRICT. — By refer- 

 ring to the map of this locality it will 

 be observed that this region of andesites 

 extends northward to the Navuningumu 

 Range, and that on the south it would 

 be separated from the district of tuffs 

 and agglomerates, named the table-land 

 of Na Savu, by a line joining the hills 

 of Soloa Levu and Thokasinga. On the 

 east it is bounded by the basaltic area 

 of the Wainunu table-land. On the west 

 it extends at the surface, with an occa- 

 sional overlying patch of submarine 

 tuffs and clays, for a distance of at least 

 two or three miles from the base of the 

 hills, and sometimes, as in the direction 

 of Sarawanga, more than half way to the 

 coast. I have endeavoured to show the 

 relation of these acid rocks to the basalts 

 and to the sedimentary deposits in the 

 geological section. 



When taking the track from Sara- 

 wanga to Nambuna by way of Ndran- 

 dramea one soon enters the region of 

 these acid andesites. The prevailing 

 rock exposed on the surface, where it 

 is usually much decomposed, is a bluish- 

 grey hypersthene-andesite with a specific 

 gravity of 2-54, and displaying in a 

 cryptocrystalline groundmass, where the 

 felsitic texture can be recognised, abund- 

 ant phenocrysts of plagioclase and rhom- 

 bic pyroxene. As high as 500 feet above 

 the sea it is occasionally capped by 

 patches of palagonitised clays and tuffs 

 scantily foraminiferous, and at one place 



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