BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 VOL. 27, PP. 325-344 JUNE 3, 1916 



PETROGKAPHY OF THE PACIFIC ISLANDS 1 



BY REGINALD A. DALY 



(Presented before the Society December 28, 1915) 



CONTENTS 



Page 



Proposal of a comprehensive exploration 325 



"Continental" rocks 326 



Volcanic islands 326 



Andesites and their genetic associates 327 



Alkaline rocks 328 



Quartz-bearing igneous rocks 331 



Miscellaneous types 331 



Conclusions 331 



Table I. — Islands of Oceanica showing outcrop of "continental" rock 332 



Table II. — Pacific islands described as volcanic, with list of igneous rock 



types 333 



Leading references 341 



Table III. — Number of islands from which rock species is reported 343 



Proposal of a comprehensive Exploration 



Polynesia, Melanesia, and Micronesia, together with the isolated, open- 

 ocean islands of the Pacific basin, include nearly 3,000 named islands. 

 Not counting New Guinea, New Zealand, and their immediate satellites, 

 the total area of these islands is about 73,000 square (statute) miles, or 

 189,000 square kilometers. Nearly one-half of the total is covered by a 

 dozen islands, among which are Hawaii, Yiti Levu, Vanua Levu, New 

 Pomerania, New Mecklenburg, and New Caledonia. The other islands 

 average only about 12 square miles in area. That part of the ocean basin 

 in which the islands are situated measures 35,000,000 square miles (90,- 

 000,000 square kilometers). Hence the complete mapping and investi- 

 gation of a total land area less than that of the State of Nebraska would 

 bring in practically all the information that can ever be obtained con- 

 cerning the bedrock geology of one-sixth of the earth's surface. It is 

 highly desirable that a single association shall soon undertake a compre- 

 hensive study of these thalassic islands. If their geology, botany, zoology, 



1 Manuscript received by the Secretary of the Society January 2, 1916. 



(325) 



