136 FOYE. 



association, though it is known to be close. The granites and diorites 

 of central Viti Levu, collected by the writer, grade into one another. 

 The texture of the gabbro from the same district allies this rock 

 with the more acid types and it was thought probable that they were 

 all of the same generation. 



As the contacts of the plutonic rocks with the sediments which 

 they intruded were not found, no more explicit statement can be made 

 concerning the relations of these rocks. 



Volcanic Succession in Viti Levu. 



The earliest known lavas in Viti Levu are andesites and rhyolites. 

 No period of erosion is known to separate the flows of these two rock 

 types and they w^re both extruded in a period preceding the deposi- 

 tion of the folded sediments of the central part of the island. ^Yhich 

 of the two types was extruded first has yet to be determined. 



After the uplift and folding of the sediments of central Viti I>evu, 

 a second period of volcanic activity' occurred. This has been referred 

 to as the second andesitic period but in reality basaltic extrusions also 

 occurred in this period. The criteria for rocks of this period are: — 

 1) they have low dips; 2) they overlie the folded sediments of the 

 interior; and 3) pebbles from them occur in the basal conglomerate 

 of the coastal-plains series. 



There must have been a considerable period of time between the 

 uplift and folding of the sediments of the interior and the deposition 

 of the coastal-plains series. It is not strange, therefore, to find 

 boulders of olivine basalt in the basal conglomerate underlying the 

 marls near Suva and andesitic pebbles in the analogous basal conglom- 

 erate in the Singatoka district. 



A study of the distribution of the volcanic rocks in Viti Levu, as 

 given by Cochrane (1911), shows that the coastal hills of the western 

 part of the island, which are assigned to the second andesitic period, 

 are composed of augitc andesites and hypersthene-augite andesites. 

 The head waters of the Waimanu and Waindina rivers, northwest of 

 Suva, drain a country underlain by hornblende andesites, though near 

 the coast in the vicinity of Suva, basalts are found. 



It is probable that in the period designated as the second andesitic 

 period, a considerable variety of lavas were extruded. The problem 

 of their relative ages has yet to be solved, though from the amount 

 of dissection suffered by the augite andesites and hornblende andesites 

 of western Viti Levu and the Waimanu district, as compared with 



