478 THE CONTINENTAL ORIGIN OF FIJI, 



of the age of tlie volcanic rock in this area. This Nasoqo section 

 is one of great interest.* 



On the western slopes of Tama ni Ivi, the highest mountain in 

 Viti Levu (4555 feet, Admiralt}^ chart), a t3^i3e of volcanic rock 

 is met with different from anything observed up to this point. 

 The rock in question is rather light bluish-grey in colour, but is 

 shown by the microscope to be comparatively basic in character. 

 It may be termed an andesitic olivine dolerite. The olivine, 

 though not very abundant, is quite an important constituent. 



Tama ui Ivi consists ver}' largely of tuffs associated with flows 

 of lavas of the type just described. The mountain, therefore, 

 probably represents an old volcanic centre, but differs from those 

 to the south, of which Korobasabasaga (p. 472) may be taken as 

 a type, in having an inconspicuous summit, and not being composed 

 to any very noticeable extent of agglomerate. At Nadarivatu, 

 distant about five miles in a direct line from the north coast of 

 the island, still more basic rock occurs. It is dark in colour, and 

 contains large idiomorphic crystals of augite, and comparatively 

 numerous, though not large, olivines. It is a t3^pical andesitic 

 olivine dolerite. This rock forms a very extensi^■e sheet, reaching 

 for miles awa}^ to the west, and forming a very marked and 

 precipitous scarp about 2000 feet in height. What its geological 

 relations are I was unable to determine. From the foot of this 

 scarp the land forms a comparatively even low-lying plain to the 

 sea. This plain is dotted with conical hills whose form is 

 exceedingly suggestive of partially ruined tuff-cones. Where 

 sections are obtainable, tuffs are exposed whose dips run at com- 

 paratively high angles (up to as much as 34°), and are ver}' 

 variable in direction. These facts seem in favour of the theor}^ 

 that the small coastal hills are largely craters. In one case there 

 is apparently evidence of an extinct hot spring or solfatara. 



* Note. — The natives informed me that " laselase " occurs somewhere in 

 the neighbourhood. This term is appHed to almost any rather soft white 

 rock, and may indicate that raised reefs occur there. I was unable to 

 investigate this further. 



