BY D. MAWSON. 471 



north of New Guinea, through Sumatra, and on to the better 

 known region of the Himalayas and Southern Europe. In the 

 New Hebrides, the folding period was preceded by local shallow 

 marine conditions and subdued volcanic activity. The folding 

 force would appear to have been exerted from the direction of 

 Fiji, against the foreland of New Caledonian crystalline schists 

 and gneisses; a single ridge probably resulted, defining the western 

 line of islands where extensive outcrops of Miocene strata are 

 exposed — in Santo, Malekula and possibly Efate. 



In accordance with Professor Suess's observations, subsidence 

 of the outer wing has, judging by the evidence of the Wai Bubo 

 beds, been overthrust, allowing of the intrusion of andesite 

 lavas followed by extensive late Miocene andesitic eruptions 

 along the plane of weakness. The result of the accumulation of 

 volcanic products from these eruptions along the ridge has been 

 to accentuate its features, so that, at the present day, a drop of 

 almost 22,000 feet is experienced within 50 miles (see Plate xxvi.). 



The next epoch-making feature in the development of the New 

 Hebrides was probably a faulting of the inner wing of the fold 

 along the line of present active volcanoes, letting down the sea 

 floor to the east, thus putting fairly deep water between the New 

 Hebrides and the Fiji land-surface. Along this fracture even 

 larger volcanoes than ever were developed, extruding not ande- 

 site lavas but basalts. These eruptions commenced probably 

 about middle Pliocene and extended down to recent times. 



During all this period of volcanic activity, extensive submarine 

 tuffaceous beds were accumulating above the folded Miocene 

 series; the earlier deposits of the nature of the Wai Bubo mineral 

 tuffs, followed later by varieties of soapstone. No interbedded 

 coral limestone was met amongst these tuffs, though occasional 

 beds proved to be highly calcareous, due to the presence of 

 abundant remains of the smaller foraminifera. 



Capping this series, are the raised coral reefs elevated to 

 heights of over 2000 feet. The oldest of these is referable to a 

 period not earlier than late Pliocene and probably not much 

 later, as it has since been intruded by lavas from centres now 



