JOURNAL OF THE COLLEGE OF SCIENCE, IMPERIAL UNIVERSITY, 



TOKYO, JAPAN. 



VOL. XVI, ARTICLE 2. 



Geologic Structure of the Riukiu (Loochoo) 



Curve, and its Relation to the Northern 



Part of Formosa. 



By 

 S. YOSHIWARA, 



Science College, Imperial University, Tokyo. 



With 5 Plates. 



CONTENTS. 



PAGE. 



PART I. INTRODUCTION 2 



PART II. LITERATURE 4 



PART III. GEOLOGY OF THE ISLANDS IN THE RIUKIU CURVE 11 



1. — The Öshima Group 11 



Oshima and its Dependent Ideti^ 12 



'Tokiino-ahima 21 



Okinoerabu-jini(( 23 



Yoro)i-ji)na 24 



Kikaifia-gliima 24 



2.— The Tokara Group 25 



3.— The Osumi Group 25 



4. — The Okinawa Group 26 



Okinaiva-jimt and itn De2}endent Islets 26 



The Kerama Snhf/roii]) 3i 



'flie Iheya Snhfjroiq) 35 



Kei-jima, Koisa-jinia and KisH-jima 35 



Kume-jiina, Aßiini-jima and Tori-sliiina 35 



5. — The Saki-shiuia Group 36 



The Miijako Suhproup 36 



The Yaetiama Subgroup 37 



The Palœozok of Ishijiaki-jima 38 



The Palœozoic of Taketomi-jima, Kohaina-jiiiui, Kaijama-jima and Iriomote-jinia 42 



Tlie Tertiary of Isliigaki-jima 43 



T)ie Tertiary of Kobama-jima 46 



The Tertiär II of Iriomote-jima 47 



T]i£ Tertiary of Yonagiini-jima 51 



Igneous Rocks in the Ynexjama Sulitjroup 52 



