458 A CONTRIBUTION TO THE GEOLOGY OF VITI LEVU, FIJI, 



surface of the peneplain is everywhere covered with a later 

 unconformable series of more or less level -bedded volcanic 

 products, save where the latter have been dissected away since 

 the last great uplift. In the neighbourhood of Narokorokoyawa 

 the level of the ancient peneplain is only about 300 feet above 

 the river bottom and about 800 feet above sea-level. Southwards 

 at Navunitorilau it rises to over 1,300 feet, and northwards at 

 Rewasau to about 1,100 feet. It must not be forgotten that 

 these and other differences of level are probably due to the tilting 

 accompanying block-faulting. 



The Waibasaga, flowing from the west to meet the main 

 stream at the town of the same name, plunges over the edge of the 

 volcanic plateau to the level of the granitic peneplain in three 

 magnificent waterfalls, called Wavou, with a total drop of over 

 1,600 feet. 



In the upper part of the Wainimala Valley, that is above 

 Udu, there seems to be some topographic indication of an older 

 valley-level from 50 to 60 feet above the present stream. There 

 are in places, as near Matainasou, very distinct cut terraces 

 which appear to indicate that the stream cut out a moderately 

 U-shrtped valley, and then quite recently suffered uplift which 

 caused increased vertical corrasion in the bottoms of such valleys. 

 This is a point which is worthy of further investigation. 



Summary of Section v i i. — The pi u tonic and slaty 

 rocks described in my former paper are described in much more 

 detail. It is shown that there are four distinct belts, with a 

 general N.N.E.-S.S.W. trend; and that these form part of an 

 extensive old peneplain, now covered unconformably by more 

 recent volcanic accumulations. Many of the slaty rocks, formerly 

 believed to be sedimentary, are now shown to be slaty trachytes. 

 No evidence is forthcoming to definitely prove the relative ages 

 of plutonic and slaty rocks; the balance of the negative evidence 

 available leans towards the granites being the older. Certain 

 physiographic peculiarities of the valley cutting are referred to, 

 but no explanation of the very extraordinary course of the 

 Wainimala between Nasava and Naivucini is attempted. 



