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



soft soapstone, a junction at this point is, geologically speaking, 

 imminent. 



The gorge by which the Wainivalau issues from the mountains 

 is very remarkable, the cliffs rising perpendicularly on both sides 

 almost from the water's edge, for hundreds of feet. Nowhere 

 east of the Medrausucu Range have I found granite or slaty rock 

 in situ, but immediately the gorge is entered highly jointed rocks 

 are encountered, and just to the west of the range granite occurs, 

 ill situ, at a level higher than that of the 'plateau immediately to 

 the eastivardj and much higher than the beds of the streams which 

 have dissected that plateau. From this point westwards, the 

 surface of the granitic and slaty rocks is more or less uniform 

 right away to the valley of the Sigatoka. I hold that the 

 existence of a heavy fault along the line of the Medrausucu 

 Range is thus rendered extremely probable, if not absolutely 

 proved; and that the volcanic products of the range have been 

 extruded along this fault-plane. We thus add geological evidence 

 to the topographical evidence for an important fault here. 



West of the range is an extensive and well-watered plain, of 

 whose existence few people seem to be aware. For long distances 

 the country is practically level, and no outcrops of rock are met 

 with. Account being taken of the fact that the Wainivalau has 

 had to cut a gorge through the Medrausucu Range, I think 

 it very probable that part, at all events, of this plain has been 

 the site of a lake. No definite evidence can, however, be 

 brought forward. Observation and native information show 

 that, even now, the area is subject to frequent inundation, so 

 that it temporarily takes on a lacustrine habit. 



At its western edge this plain rises towards the water- 

 parting between the Wainivalau and Wainimala Rivers, and we 

 pass off soft soil on to solid, much-jointed granite. The stream 

 has entrenched itself deeply in the surface of this rock. The 

 granite is overlain by the lavas and agglomerates of the Uvuuvu- 

 nidavui Range, which is andesitic in character. The plain is 

 bounded on the south by a ridge of no great elevation,' separating 

 it from the Waidina Valley. The granites must have a very 



