CHAPTER XIII 



DESCRIPTION OF THE GEOLOGICAL AND GENERAL PHYSICAL 

 FEATURES {continued) 



The Valanga Range 



This range, which trends N.W. and S.E. between the Mariko 

 mountain-ridge and the head of the valley of Na Kula, attains a 

 height of i,88o feet at its N.W. and of 1,710 feet at its S.E. 

 end. The average elevation, however, is probably not over 1,300 

 or 1,400 feet. My acquaintance with the range is only partial, 

 but it is sufficient to bring to light some of its leading structural 

 features. Those who follow me will find in these mountains a 

 very interesting region for their geological explorations. 



(i) Traverse of the Valanga Range.— In making the 

 journey from Valanga to Vunimbua, I crossed the range where 

 its elevation was about 1,300 feet. Basic agglomerates, containing 

 sometimes amygdaloidal blocks, are displayed in the low district 

 between Valanga and the foot of the range. In the stream-course 

 at the base of the slope the deeper seated rocks of the range are 

 at once exposed. Large masses, 5 or 6 feet across, of altered grey 

 pyroxene andesites lie in the bed of the stream. Some of them 

 show opaque porphyritic felspar and have the appearance of 

 porphyrites (sp. gr. 2'67). They belong to the type described 

 on page 271 under genus 6 of the augite-andesites. Others are 

 grey propylitic varieties of a basic semi-doleritic andesite pene- 

 trated by cracks containing calcite, and displaying in a ground- 

 mass, exhibiting much viridite and a little pyrites, calcitic pseudo- 

 morphs of the felspar phenocrysts and more or less parallel felspar- 

 lathes, '15 mm. long and somewhat altered. Another of the 

 deeper-seated rocks commonly exposed on the upper west 

 slopes of the range is a dark grey rock showing much porphyritic 



