GEOLOGICAL OBSERVATIONS IN FIJI. 137 



that affecting the basalts near Suva, the basalts appear to be the more 

 recent. 



The volcanic rocks which intrude tlie uplifted coastal series of south- 

 western Viti Levu are basalts or basaltic andesites. 



The tentative succession of lavas for Viti Levu is, therefore, as 

 follows : — 



First epoch — andesite, rhyolite, 



Second epoch — hypcrsthene-augite andesite, hornblende andesite, 

 augite andesite, basalt, 



Third epoch — basalt. 



Erosion intervals separate the groups. Between the first and 

 second periods of volcanics occurred the folding movements which 

 disturbed the interior sediments. 



Comyarison of the lavas of Ovalau, Mbengha, and the Yasawa Group with 

 those of Viti Levu. 



A hornblende andesite from Ovalau has been described by Wich- 

 mann (1882, p. 34). The rocks of Mbengha are basalts, but, while 

 one variet}' is characterized by olivine and augite, another approaches 

 a hornblende andesite and contains hornblende and augite. The 

 rocks described from the Yasawa group are basalts and hornblende 

 andesites. The prevailing flows of the islands are basalts. 



It has been stated previously, (Part I, page 19), that the basalts 

 of the Yasawa group were extruded after the uplift of the limestone 

 islands which belong to the same general period as the coastal sedi- 

 ments of Viti Levu. Because of the relation of the basalts to the 

 Yasawa limestones, the main islands of the group are thought to have 

 been built during the last or basaltic period. The andesites of these 

 islands may, therefore, be remnants of flows dating from the earlier 

 andesitic period. The same may be said for the hornblendic rocks of 

 Mbengha and Ovalau. 



Volcanic Succession in Vanua Levu. 



The lavas erupted upon the eroded gabbro, near Mount Avuka, are' 

 similar to the andesites of Viti Levu which were assigned to the first 

 andesitic period. Pitchstones were found associated with these rocks 

 and it was inferred that certain of the rhyolitic deposits were of the 

 same period; but, in general, the erosion of the rhyolites of northeast- 



