GEOLOUICAL Ob.SEHVATIOXS IN I I.I I. 31 



Mbutiia Bay District, 



The Mbutlia Bay District constitutes the extreme eastern side of 

 Vanua Levu. The (Hstrict may he divided into two parts. Between 

 Mbutha Bay and tlie hinji;, narrow depression foriniiifj; Natewa Bay, 

 a continuous range of uniform structure antl ^■egetation stretches in 

 a northeast-southwest direction for 50 miles or more. This range 

 has been called, by Guppy, the Natewa peninsula. The island of 

 Kioa, lying a few miles to the east of the mainland and forming part 

 of the enclosing land about Mbutha Bay, has a similar structure, and 

 with a promontory on the southwest, forms a spur of the Natewa 

 Peninsula. 



The land at the southeastern end of Vanua Levu, Guppy has called 

 the Waikava Peninsula. The eastern half of this peninsula consti- 

 tutes the second part of the Mbutha Bay District. 



The first-mentioned sub-division of the district, including Natewa 

 Peninsula, is underlain by non-fossiliferous ash-beds, agglomerates, 

 and lava flows of sub-aerial origin. On them, erosion has developed 

 a sub-mature topography. The divide between Mbutha Bay and 

 Natewa Bay is very close to Natewa Bay, so that its northwestern 

 slopes are much steeper than its southeastern slopes. To the east of 

 the divide, along the axis of the range, a number of high-standing 

 basins, a mile to a mile and a half in width, are enclosed on nearly all 

 sides by precipitous walls. The rocks about the basins show qua- 

 quaversal dips and the small streams draining the basins issue through 

 narrow openings in the enclosing walls. The basins are, therefore, 

 considered to be old craters. 



The river at the head of Mbutha Bay has cut its valley across 

 a series of ash-beds. Its lower course is embayed by a recent 

 submergence, further evidences of which are seen about the shores 

 of Mbutha Bay. Delta-filled valleys abound. The shore-lines of 

 Rambi and Kioa demonstrate the embayment. The accompanying 

 sketch map (Figure 13) shows the coastal outline of the bay. 



The killing of coral patches by an advancing delta was observed 

 about the shores. Near the head of the bay, (see sketch map), the 

 coral patches are dead and submerged about one fathom. As the 

 open waters to the north are approached the coral thrives more and 

 more, attaining vigorous growth where the currents sweep in between 

 Rambi and Kioa. 



Just east of the small promontory jutting out from the Waikava 



