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 1, 8 80 feet at its N.W. and of 1,710 feet at its S.E. 

 2nd. The average elevation, however, is probably not over 1,300 

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

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

 'eatures. Those who follow me will find in these mountains a 

 /ery interesting region for their geological explorations. 



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



ourney from Valanga to Vunimbua, I crossed the range where 



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



iometimes amygdaloidal blocks, are displayed in the low district 



)etween 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 



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



■ )yroxene andesites lie in the bed of the stream. Some of them 



; how opaque porphyritic felspar and have the appearance of 



])orphyrites (sp. gr. 2*67). They belong to the type described 



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



} rey propylitic varieties of a basic semi-doleritic andesite pene- 



1 rated by cracks containing calcite, and displaying in a ground- 



1 lass, exhibiting much viridite and a little pyrites, calcitic pseudo- 



1 lorphs of the felspar phenocrysts and more or less parallel felspar- 



;1 ithes, '15 mm. long and somewhat altered. Another of the 



< eeper-seated rocks commonly exposed on the upper west 



J opes of the range is a dark grey rock showing much porphyritic 



