470 A CONTRIBUTION TO THE GEOLOGY OP VITI LEVU, FIJI, 



main water-partings of the island, namely, at NavunitorilaUy 

 between the heads of the Wainikoroiluva and Wainimala Rivers, 

 Their existence as a basement has been proved over an area of 

 at least 35 miles by 30 miles. It is inferred that their surface 

 was, prior to Tertiary time, reduced to the condition of a^ 

 peneplain. 



The most recent rocks (excluding the present-day river-alluvials 

 and the coral-reefs) appear to be a series of andesitic volcanics 

 varying from pyroxene andesite to hornblende andesites. It is 

 likely that, of the two, those of hornblendic facies are the older. 

 These andesitic rocks form lofty mountain masses, and yield 

 magnificent scenic effects. They have, in part at all events, been 

 extruded along major fault-planes, which have had a dominant 

 influence on the structural features, and even on the very exist- 

 ence of the island of Viti Levu and of the Fiji Group as a whole. 



Faulting . — One very important line of faulting is shown to 

 exist, in a general N.N.W.-S.S.E. direction, along the course of 

 the Medrausucu Range; a parallel line is inferred, with great 

 probability, to exist along part of the courses of the Wainikoro- 

 iluva and Navua Valleys. The country between these two faults 

 is of the nature of a " horst." 



A second axis of faulting about at right angles to the first is 

 suggested, but the evidence for its existence, resting as it does 

 solely on topographical evidence, is not so convincing as that for 

 the other axis. 



Uplift s. — The basal beds of the newer series reach an altitude 

 of 1350 feet above sea-level near Nadrau; the granitic rocks 

 attain about the same level at Navunitorilau. The topmost beds 

 of the level-bedded soapstones reach well over 4000 feet, and 

 probably the rocks (limburgites and tuffs) forming the highest 

 summit in the island (Toma na Ivi, 4555 feet) are members of 

 the same series. The soapstones are certainly marine beds, and 

 we thus have evidence of a positive movement of the land, during 

 Cainozoic time, amounting to well over 4000 feet. Further 

 investigation is necessary to completely trace the stages of this 



