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 5 



NDRANDRAMEA DISTRICT. By refer- f 



ring to the map of this locality it will '| 

 be observed that this region of andesites 



extends northward to the Navuningumu >* 



<u 



Range, and that on the south it would 



be separated from the district of tuffs ~ 



and agglomerates, named the table-land o 



of Na Savu, by a line joining the hills 



of Soloa Levu and Thokasinga. On the | 



east it is bounded by the basaltic area T 



J tJD 



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 ,2 



hills, and sometimes, as in the direction *g 



of Sarawanga, more than half way to the J 



coast. I have endeavoured to show the . 



relation of these acid rocks to the basalts 



and to the sedimentary deposits in the 



geological section. zf 



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- w 



grey hypersthene-andesite with a specific . 



gravity of 2*54, and displaying in a J? 



cryptocrystalline groundmass, where the o 



felsitic texture can be recognised, abund- 1* 



ant phenocrysts of plagioclase and rhom- ^ 



bic pyroxene. As high as 500 feet above 2 

 the sea it is occasionally capped by 

 patches of palagonitised clays and tuffs 

 scantily foraminiferous, and at one place 



