306 GEOLOGY: W. G. FOYE 
even small boats find difficulty in entering the river-mouths through 
the tangle of mangrove bushes. 
The geological history of the island is more complex than has been 
previously stated J From a hasty survey of the interior of the island 
I inferred that an old land of slates and red sandstones was intruded by 
a batholithic mass which solidified as gabbro, diorite and granite. The 
mountain block thus formed was deeply eroded and the igneous rocks 
were exposed. Volcanoes then burst forth and a series of andesitic and 
rhyolitic flows were poured out over the eroded surface. 
The aggrading flows were later deeply eroded and submerged. A 
coraliferous conglomerate was laid down on the submerged surface and, 
during a period of oscillatory movements, several hundred feet of marl 
and clay stones with occasional thin seams of coal were deposited. This 
period was followed by one of more decided submergence, during which 
approximately 150 feet of coraliferous limestones was laid down. The 
entire series will be spoken of, for reasons which will appear in the fol- 
lowing paragraph, as the 'folded sediments.' 
Compressive stresses were then developed in this portion of the earth's 
crust. The limestones and older rocks were uplifted and sharply folded 
along lines running in general N.N.W. byS.S.E. The folding was so 
intense that the limestones were occasionally transformed to marble. 
A period of faulting and volcanism followed during which the island 
assumed somewhat of its present form, and a series of volcanic hills were 
built up near the coast. Erosion and submergence then allowed marls 
and interbedded coraHferous limestones to be laid down uncomformably 
as a thin veneer about the edge of the island. These sediments will be 
spoken of as the 'coastal series.' 
Again the island was differentially upKfted. The wide lagoon extend- 
ing northwest toward the Yasawa islands was initiated by tilting in that 
direction and, at the same time, the coastal plain at the eastern side of 
the island was elevated. During the latter part of the epoch, volcanic 
rocks were injected into the coastal series and the Yasawa islands were 
built up. Recent differential movements have upKfted the southwestern 
shore of Viti Levu and at the same time depressed the Yasawa islands. 
In general the present coral reefs are developing on platforms which 
originated during the deposition of the coastal series. 
2. Vanua Levu. — Vanua Levu, the northern of the two larger islands 
of Fiji, is 104 miles long from east to west and 20 to 25 miles in width. 
The eastern portion of the island is split by a long, narrow bay extend- 
ing inland from northeast to southwest for 50 miles. To the eastern 
peninsula, thus formed, are appended several peninsulas which jut 
