GEOLOGICAL OBSERVATIONS IN FIJI. 43 



GEOLOGICAL HISTORY OF THE SMALLER ISLANDS, 

 ESPECIALLY THE LAU GROUP. 



Introduction. 



During an extended exploration of the Lau Group which lies to the 

 east of the larger island of Fiji, the writer reached the following con- 

 clusions : — 



1) The Lau islands are underlain by volcanics, formed during the 

 second period of andesitic eruptivity, then maturely eroded, and 

 finally submerged. 



2) During long submergence, coralliferous limestones were laid 

 down unconformably on these volcanic rocks. 



3) A later uplift elevated the coralliferous limestones above sea-level. 



4) During a later basaltic period of volcanic eruptivity^ olivine 

 andesites or basalts intruded the elevated limestones. 



5) With succeeding erosion a large amount of the elevated lime- 

 stones disappeared, largely owing to atmospheric solution. 



6) Most of the islands show a recent submergence. 



According as the various islands have passed through all, or only a 

 part, of these stages, the Lau islands may be classified as follows: — 



I. Islands depressed and covered with limestone and later uplifted 

 and intruded or covered by volcanic rocks of the second period. 



A. Islands depressed so deeply that the tops of the andesitic 



hills of the first period were covered by limestone. 



1) Islands with limestone partly or wholly eroded from the 

 summits of the andesite. 



Vanua Mbalavu 

 Susui 



2) Islands with volcanic rocks of first period still covered 

 with limestone. 



Kambara 



B. Islands whose tops were never covered by limestone. 



Kandavu 

 II. Islands depressed and covered with limestone and later up- 

 lifted but not affected by the second period of volcanic 

 eruptivity. 

 A. Islands depressed so deeply that the tops of the andesitic 

 hills were co^'ered with limestone. 



