GEOLOGICAL OBSERVATIONS IN FIJI. 75 



At the foot of the chlfs he abundant blocks of the hmestone, fallen 

 from the collapsed caves in the cliffs. As might be expected, the 

 limestones here are greatly recrystallized. No large masses of coral 

 heads in place were seen. 



On the inner side of the rim, along the northwestern horn, sandflats 

 lying 8 or 4 feet above high-tide level finger into the base of the central 

 ridge. About the flats are many pinnacles of limestone. A slight 

 submergence would allow undercutting to progress and the pinnacles 

 would be transformed into islets similar to those dotting the central 

 bay. 



Where evidence could be secured, the cliffs at this side of the rim 

 appear to be largely composed of material like that in the cliffs of the 

 outer rim (coral and shell rubble). But at one place, back of the 

 village of Navindamu, a lense of coral heads in place, 5 or 6 feet thick 

 and 150 to 200 feet long, is clearly discernible. At the base of the 

 deposit, which lies 10 feet above sea level, are 2 to 3 feet of sandy 

 debris containing bits of shell and coral, loosely cemented. This bed 

 is overlain conformably by 4 to 5 feet of coral-head limestone. A 

 paste of the underlying, sandy deposit fills the interspaces between 

 the heads. None of these deposits was cemented, while overlying 

 them were 150 feet of much re-crystallized limestone, so compact 

 that its texture can barely be made out. An occasional fragment of 

 coral or shell is discernible; otherwise original structures have been 

 obliterated. 



The dips of the limestone taken at several points along the inner 

 and outer side of the rim are 8° N., 10° N., 5° E., and 12° N. No 

 evidence of tilting was seen in the island, and it is inferred that these 

 dips represent the original angles of deposition. 



The present reef is fringing for the greater part of the circumference 

 of the island, though shallow lagoons, slightly over a fathom in depth, 

 occur at intervals. The continuous shifting of sands within the inner 

 bay makes it a poor habitat for corals, and few develop there. The 

 sand is also a factor in the under-cutting and slow destruction of the 

 central islets. 



Much of the reasoning with regard to the origin of the islands of 

 Ongea and Vatoa applies to Fulanga. The depths of the central 

 bay indicates submergence. The narrowness of the surrounding 

 fringing reef points to a recent shift of the sea-level. Atmospheric 

 solution has so far dismembered the island that only a part of its rim 

 now remains, together with an occasional bit of its center, over which 

 the water is now, in general, 6 to 10 fathoms deep. 



