GKOLOGICAL OHSKHVATIONS IN 11,11. 



27 



which jut out to the (.'astwiinl. A t'fw miles oll'-shorc, niiiuy small 

 ishmds further compheate the coastal forms about \'auua Levu. The 

 entire circumference of the main island is marked by pocket harbors 

 and jutting headlands. 



The rocks of the ishind are primarily andesitic ash and agglomerates, 

 though a series of rhyolitic-ash deposits occurs along the northeast- 

 ern coast. The rocks of the eastern side of the island, deposited 

 subaerially, have never been submerged, and are maturely dissected. 



The andesites of the central part of the island are submarine in 

 origin. They once formed a wide, submarine platform of gentle 

 slope, which was later elevated 3000 to 4000 feet and dissected into 

 irregular hills forming a mature to late-mature topography. 



Lambasa District. 



The low, sugar-cane lands, formed by the delta flat of the Lambasa 

 river, lie a little east of the center of the northern coast of Vanua Levu. 

 The accompanying map (Figure 10) shows the topography of the area. 

 Two tidal rivers, the Nghawa and the Lambasa, have deposited the 



Figure 11. View of the Lambasa Delta-plain. 

 Drawn by Wright after a Photograph. 



silts of the delta which is continuous with flood plains far back among 

 the hills. Several residual masses of volcanic rocks stand isolated 

 within these plains, their bases covered with delta sediments (Figure 



11). 



The region drained by the two rivers mentioned was once occupied 

 by several andesitic volcanoes. The ash deposits which covered the 



