BY D. MAWSON. 473 



Extensive trough-faulting crossing the original fold almost 

 perpendicularly* and resulting in the development of an island 

 chain, most probably, therefore, did not follow directly on the 

 formation of the primary fold, but succeeded it after the lapse of 

 a longer or shorter period,! giving time for the migration of 

 representatives of the Papuan fauna as advocated by Mr. C. 

 Hedley. 



Comparing New Hebridean tectonic geology, as developed in 

 this paper, with that of Sumatra, a continuation of the same fold 

 chain, the perfect similarity will be at once apparent. As no 

 beds older than the Miocene^ were met with in the Group, the 

 nature of such developed at a depth is entirely problematical; 

 since, however, later geological features in these two regions 

 have so much in common, it is probable that the similarity 

 extends back to the older formations, and we should then expect 

 to find below the New Hebrides Miocene an extensive develop- 

 ment of serpentine and diabase. The probability of such being 

 the case is greatly strengthened by the fact that in New Cale- 

 donia, not far distant, and in New Zealand, to the south, a 

 continuation of the same fold-chain, the serpentine horizon is 

 strongly developed. 



CONCLUSIONS. 



The discovery that the New Hebrides Islands are a fold-chain 

 of Alpine age throws great light upon our knowledge of South 

 Pacific geology, and at once suggests the application of similar 

 principles with regard to other island groups. 



Accordingly, after a careful study of the Admiralty charts and 

 an elementary knowledge of the geology of the islands, it will be 



* Lines of weakness crossing the fold would, in all probability, be pro- 

 duced contemporaneously with its formation in accordance with the blatter 

 type of faulting; actual trough subsidences though would be precipitated by 

 the later extravasations of lava. 



t So far as our observations went, such was found to be the case, e.g. , the 

 Tasiriki fault crossing the recent'raised coral, and the Havannah Harbour 

 fault crossing the soapstone. 



J It is none the less probable that limited outcrops do occur, as from the 

 advanced metamorphic state of the pebbles of uralite porphyry from Malekula 

 they must date back to times preceding the folding. 



