308 
GEOLOGY: W. G. FOYE 
and are found at an elevation of 75 to 100 feet. So recently have these 
reefs been uplifted that the lagoon flat and outer barrier reef are still 
preserved intact. 
I visited only the eastern and central portions of Vanua Levu. The 
modern fringing reefs are here developing either along the shore-line 
of recently submerged volcanic rocks or on coastal flats formed of the 
fine ash swept from the elevated hills of submarine tuffs. The most 
recent movements have been differential and while uplift has taken 
place at the southeastern side of the island, subsidence has occurred to 
the east and north. The modern barrier reefs occur where subsidence 
has taken place either due to tilting or faulting during uplift. 
3. The Lau Islands.— The Lau Islands lie east of the larger islands 
of Fiji and are scattered over 300 miles of the ocean floor from the 16th 
to the 20th parallel of south latitude and from the 178th to the 179th 
meridian of west longitude. There are from 40 to 50 islands ranging 
in size from a half a mile to 20 miles in length. The islands may be 
grouped empirically in three classes. 
1. Islands composed of volcanic rocks and limestone. 
2. Islands composed of limestone alone. 
3. Islands composed of volcanic rocks alone. 
The volcanic islands usually have a number of separate peaks rising 
to altitudes of 600 to 900 feet, whereas the islands composed of lime- 
stone rise to nearly a constant level about their edges but are often de- 
pressed toward their center. 
The limestone is always coraliferous and is raised to a maximum ele- 
vation of 1030 feet in the island of Vatu Vara. In every case studied 
the limestone rests unconformably on a basement of eroded volcanic 
rocks, indicating subsidence. Certain of the elevated limestones have 
the atoll or barrier reef form and the inference is drawn, as no uncon- 
formities are found within the limestone, that the elevated atolls were 
formed during the subsidence of the underlying volcanic surface. 
The corals included in the elevated limestones are Pleistocene or 
Recent in age according to the determination of Dr. T. W. Vaughan. 
Many of the elevated limestone islands have been greatly reduced 
in size by atmospheric solution. Occasionally, as in the cases of Ful- 
anga and Ongea, sea-level fiats have developed. In most of the islands 
the flats have been submerged and the residual masses of limestone 
dotting the flats have formed undercut islets scattered over a lagoon 
10 to 15 fathoms in depth. I believe the submergence is due to actual 
subsidence since it is more recent than the return of the waters to the 
ocean after the Glacial epoch, and since Pleistocene wave erosion would 
