GEOLOGICAL OBSERVATIONS IN FIJI. 9 



subsidence, on every side, and was led to abandon Darwin's theory 

 as untenable. He concluded that the coral reefs developed on plat- 

 forms eroded on uplifted limestone by the action of the sea. 



E. C. Andrews (1900) examined the limestones in the field. The 

 island of Mango, one of the Lau group, was studied specially and it 

 was concluded that the volcanic rocks of the island were erupted 

 later than the upraised limestones. The limestones of Vanua ^Ibalavu 

 were described under two classes: as compact, bedded limestones, and 

 as limestones of reef-rubble origin. 



In 1903, W. G. Woolnough (1903, p. 457 and 1907, pp. 431 to 473) 

 made a rapid trip across Viti Levu and was the first to describe 

 granites from specimens collected "in situ." 



During the years 1896 to 1899, Guppy (1903) made a very detailed 

 study of the island of Vanua Levu. His chief conclusion was that 

 " Vanua Levu is a composite island built up f luring a long period of 

 emergence, that began probably in the later Tertiary period, by the 

 union of a number of large and small islands of volcanic formation 

 representing the products of submarine eruptions." 



More recently (1914-15), Davis (1915, p. 251) visited the group 

 and described the island of Vanua Mbalavu as an ideal example of a 

 barrier reef formed, according to Darwin's theory, during the sub- 

 sidence of a central, eroded, volcanic mass. 



ABSTRACT. 



1. The larger islands of Viti Levu and Vanua Levu have central 

 cores of deeply eroded plutonic rocks and are thought to be remnants 

 of an older continental mass. 



2. There have been four periods of vulcanism in Fiji. An early 

 period of rhyolitic eruptivity was followed, without a perceptible 

 erosion interval, by a first period of andesitic eruptivity. After ero- 

 sion and subsidence, a succeeding uplift was accompanied by a second 

 period of andesitic eruptivity. Erosion and renewed subsidence 

 were followed by another period of uplift initiating a series of basaltic 

 eruptions. 



3. There are two series of sedimentary rocks in Viti Levu. The 

 folded series of the interior resemble the folded series of the New 

 Hebrides, which Mawson believes to be Miocene. The coastal-plain 

 series have low dips and, by fossil evidence, are apparently post- 

 Tertiary in date. 



