450 THE GEOLOGY OF THE NEW HEBRIDES, 



The complete reversion of dip in the thick series of Miocene 

 rocks exposed on the Wai Bubo argues extensive folding, followed 

 by faulting probably overthrust in a westerly direction. 



A few hundred yards inland from Tasiriki is a well exposed 



fault trending in a N.W. direction. This fault is much newer 



than those previously mentioned, as it cuts across the raised coral 



limestone. 



Local Features. 



Tangoa, like the other small islands so numerous along the east 

 and south-east coasts of Santo, is built up completely of coral 

 reef debris. On the mainland, opposite, a broad flat averaging 

 one mile in width, composed mainly of river debris, leads to the 

 foot of the coral terraces 800 ft. to 900 ft. in height. 



Pebbles collected in the Atsone River, some distance from the 

 mouth, proved to be of no special interest, with perhaps one 

 exception — that of a sedimentary rock composed largely of 

 volcanic ash, and containing ver}^ abundant organic remains, 

 notably Halimeda opuntia. 



Araki is an exact counterpart of the hill Tumebu (Plate xxi.) 

 on the mainland adjacent. On the east side at an elevation of 

 about 200 ft., just below the second terrace, there is a fair-sized 

 cave running into the coral limestone for a distance of 100 yards. 

 In it we collected a few specimens of stalactites, the first we had 

 met with in the New Hebrides. A considerable quantity of bat 

 guano, estimated at 14 tons, covers the floor at its inner end for 

 a depth of one foot, six inches. 



Tasiriki Tasmalum Track. — From Tasmalum the track crosses 

 a low raised reef limestone plateau not exceeding 100 ft. in 

 height descending later on into the bed of the Navaka. About 

 \ mile walk over the pebbles and sand banks brings one to the 

 opposite side, where the track leaves the river and commences a 

 long ascent. At this spot a good outcrop of fossiliferous soap- 

 stone-like foundation-beds dipping 8^ S., 83^ E. appears, capped a 

 short distance above by raised reef limestone. The ascent con- 

 tinues until within \\ miles of the ford on the Wai Bubo; at 

 this point it has reached an elevation of close on 1000 ft. 



