184 Reviews — Geological Observations in Fiji. 



study of the strike of the strata indicates that the periclinal structure 

 of the district is modified by the interference of two anticlines and 

 a syncline having aN.N.W.-S.S.E. strike and parallel to the East 

 London ridge. These folds, though of very slight amplitude, never- 

 theless produce a marked effect on the strike of the Cretaceous rocks 

 and are possibly due to slight posthumous movements of the Charnian 

 fold-series. Hence it is possible that Palaeozoic rocks may underlie 

 the district at no great depth. 



V. — Geological Observations in Fiji. By "W. G. Fote. Proc. 



Amer. Acad. Arts and Sci., vol. liv, pp. 1-145, with 1 plate and 



40 figs., 1918. 

 ROFESSOR POYE spent seven or eight months of 1915-16 in 

 a geological expedition to the islands of the Piji group, chiefly 

 for the purpose of studying coral-reefs at firsthand, and this long 

 paper gives an account of his observations and the conclusions drawn 

 from them. The first part, entitled "Geological History of Piji", 

 describes the physiography and stratigraphy of the islands, and 

 discusses the living and raised reefs in considerable detail. The 

 larger islands possess a plutonic core and two series of sedimentary 

 rocks, the older, probably Miocene, being folded along trend-lines 

 parallel to those described by Suess in other parts of Oceania, the 

 3 r ounger unfolded and apparently post-Tertiary. Pour separate 

 volcanic phases are recognized with a regular gradation in acidity, 

 namely, (1) rhyolite, (2) andesite, (3) andesite, (4) basalt. The 

 elevated limestones rest unconformably on eroded volcanic rocks, and 

 there is abundant evidence of great instability of relative level 

 throughout the group, partly due to uplift and subsidence and 

 partly to return of water after the Glacial period. Hence the 

 conditions are very favourable to the formation of reefs according to 

 Darwin's theory. The reduction of masses of elevated limestone to 

 sea-level has in some cases been accomplished by atmospheric 

 solution, and slight submergence initiates the growth of reefs and 

 atolls on these platforms. The present coral-reefs have been 

 developed on surfaces formed by integration of a number of pro- 

 cesses : (a) atmospheric erosion, (b) wave-cutting, (c) sedimentation, 

 and (d) volcanic aggradation. On the other hand, it is demonstrated 

 that the older limestones developed on a subsiding basement of 

 eroded volanic rocks, but no evidence could be found in Piji for the 

 existence of Pleistocene benches; the platforms are much more 

 modern in their development. 



The second part of the paper gives a petrographic description of 

 the rocks collected, including plutonic, hypabyssal, volcanic, pyro- 

 clastic, and sedimentary types. The igneous rocks are exclusively 

 Pacific in their character, the most acid rock observed, with 70 per 

 cent of Si02, called tonalite by the author, being composed of quartz, 

 plagioclase, biotite, and hornblende. This appears to grade into 

 diorite and gabbro, while the volcanic rocks are characterized by 

 hornblende, augite, and hypersthene. It is suggested that the horn- 

 blende-hypersthene rocks have been formed by submarine eruption, 



