GEOLOGIC STRUCTURE OF THE RIUKIU CURVE. 



33 



the limestone, und runs from XE to SW. Minna-jima lying near 

 Sesoko-jima is a very flat island, composed wholly of coral reefs. 



le-jima has a remarkable feature in a huge p;)inted rock called 

 Gusuku which rises out of the surrounding hills in the eastern part of 

 the island (Fig. 2). There is another point called Buppiji, but it is 



Gusuku 



M 



Buppiji 



Fig. 2.— View of le-jima seen from Tokuji. 



only a little higher than the vast surrounding plateau, which is entire- 

 ly made up of raised coral reefs. The rocks of these two prominences 

 are compact quartzite and limestone, the same as those in the other 

 islands of the Riukiu Curve. I collected a specimen of diabase ex- 

 posed after the erosion of a reef. Blocks of Paltcozoic sandstone and 

 pyroxenite are found enclosed within the raised reefs. Though the 

 latter are horizontal, the Palaeozoic is always inclined with the strike 

 XE and the dip NW, characteristic of the Riukiu Curve. 



The above-mentioned small islands of the Okinawa group are nil 

 situated on the western side of Okinawa-jima. Those on the east of this 

 island are arranged in a X — S line and are six in number; namely Ike, 

 Miyagusuku, Hama (Fig. 3), Hianja (Fig. 4), Tsuken and Kudaka. 



Fig. 3. View of Hiauia-jiuia seen from Yonagusukii-jima and Hianja-jima. 



Fig. 4. — View of Hianja-jima seen from the western side of Yonagusuku-jima. 

 (Tertiary rocks on the western [i.e. left] side). 



