IV 



MBUA AND NDAMA PLAINS 55 



The Dividing Ridge between the Mbua and Lekutu 

 PLAINS. — A level rolling " talasinga " district intervenes between 

 Mbua Bay and the dividing ridge. The upper part of this ridge, 

 which attains a height of about 500 feet above the sea, is composed 

 of a hard grey sandstone-like tuff, effervescing feebly with an acid, 

 which on examination proves to be formed in great part of frag- 

 ments, -07-I mm. in size, of a dark basic glass occasionally 

 vacuolar. The rest of the deposit consists of similar-sized frag- 

 ments of plagioclase and other minerals, and includes also a few 

 tests of foraminifera of the " Globigerina " type. 



The mass of the ridge, however, is composed of coarse tuffs and 

 agglomerates of a different kind which have been covered over by the 

 foraminiferous deposit just described. Thus there are exposed on the 

 lower slopes, tuffs and agglomerates of a basic pitchstone formed of 

 a brown glass containing a few felspar and pyroxene microliths. 

 In the tuff the fragments are three to six mm. in size and show 

 evidence of crushing in situ, the interstices being filled with 

 debris of the same material more or less palagonitised, 1 but there 

 is no carbonate of lime. Large masses of an agglomerate made 

 up of blocks of an acid andesite occur higher up the slopes. The 

 component rock belongs to an unusual type of hypersthene-andesite, 

 specially noticed on page 297. 



The interesting feature in this ridge lies in the testimony it 

 affords that the extensive Mbua and Ndama basaltic plains, on 

 which I was unable to discover any submarine deposits, were at one 

 time submerged. 



The Mbua and Ndama Plains.— These rolling plains are a 

 striking feature in the western end of Vanua Levu. They have an 

 arid barren look, are clothed with a scanty and peculiar vegetation, 

 possess a dry crumbling soil often deeply stained by iron oxide, are 

 traversed by rivers without tributaries descending from the wooded 

 uplands of the interior, and in fact have well earned the name given 

 to them by the natives of " talasinga " or sun-burnt land. Both 

 Seemann and Home have remarked on the South Australian aspect 

 of these regions, which are characteristic of the lee and drier sides 

 of the larger islands of the group. Covered for the most part with 

 grass, ferns and reeds, these low-lying districts are dotted here and 

 there with Casuarinas, Pandanus trees and Cycads, whilst such 

 other trees and shrubs as Acacia Richii and Dodonsea viscosa, add 

 to the variety and peculiarity of the vegetation. The origin of 

 these "talasinga" districts is discussed in the last chapter. 

 1 See remarks on "crush-tuffs" on p. 334. 



