VI YANAWAI COAST 95 



followed during the emergence of this part of the island. The 

 absence or rarity of dykes is remarkable ; but most of the hills 

 would represent volcanic " necks " whether of massive rock, 

 tuff, or agglomerate. 



The District Between the Kumbulau Peninsula and 

 THE Yanawai River. — Between Nandi Inlet and the village of 

 Rewa the sea-border is low and often swampy, whilst occasional 

 spurs descend from the inland range into the swamps without 

 reaching the coast. Pebbles of "soapstone " (foraminiferous mud- 

 rock) occur in streams and are no doubt derived from the incrusting 

 deposits of the neighbouring hill slopes. In one stream-bed in the 

 swamps is exposed in situ a remarkable chocolate-coloured rock 

 that looks like a greasy pitchstone or a palagonite-rock. It is 

 however of detrital origin, and is composed in mass of minute 

 fragments of a basic, sometimes vacuolar, glass in great part 

 converted into palagonite ; whilst there are a number of broken 

 crystals of olivine and plagioclase. Through the palagonitic 

 alteration the fragmental character is somewhat obscured, zeolites 

 being extensively developed in the interstices. A little lime occurs 

 and there is a suspicion of foraminifera. The deposit belongs to 

 the group of palagonite marls described on page 335. The deeper 

 rocks of the district are represented in a spur by an altered augite- 

 andesite, originally hemicrystalline and containing much granular 

 epidote. 



Proceeding northward from the village of Rewa, one crosses 

 another spur descending from the inland range. It is formed in 

 mass of a dark doleritic olivine-basalt (spec. grav. 2-91) charac- 

 terised by the length of the felspar-lathes ("28 mm), possessing a 

 little interstitial glass, and referred to genus 25 of the olivine class. 

 It probably represents an ancient flow. Its surface is incrusted, as 

 high as the road ascends, nearly 200 feet above the sea, by fine and 

 coarse palagonite-tuffs ; whilst the pebbles of foraminiferous mud- 

 rock in the stream indicate the existence of incrusting marine 

 deposits further up the slopes. The road then leads down into a 

 low-lying undulating district that forms the sea border as far as the 

 mouth of the Yanawai, and reaches about two miles inland without 

 exceeding an elevation of 100 feet, although low hills occur here 

 and there. This region is fronted by mangrove swamps and is 

 traversed by the Matasawalevu and Ndranimako streams. It is a 

 district of basic tuffs and foraminiferous clays, which, as shown 

 below, extend up the slopes of the basaltic Wainunu table-land that 

 lies behind. The soil in all the low country between Rewa and the 



