GEOLOGIC STRUCTURE OF THE RIUKIU CURVE. 



43 



corner; in other parts we find a strike E-AV, and a dip toward the 

 south. 



The Palaeozoic rocks of Inomote-jima are mostly pyroxenite-like 

 and are exposed on the south of Takana, and show various distortions 

 caused by andésite stocks. 



Tertiary Rocks of Ishigaki-jima. Among these rocks which occupy 

 very large areas in the Yaeyaina subgroup, we find the following 

 in Ishigaki-jima; namely fine-and coarse-grained brownish sandstones, 

 compact quartzose sandstone, b'mestone and agglomerate tutt', all ex- 

 posed in the form of patches rather near the coast. The strata are elevat- 

 ed hardly more than a hundred feet, except in the case of the tufaceous 

 rocks. The most northern exposure extends from the north-western 

 corner of Ibaruma to the cape called Ishizaki (Fig. 7). A continuation 



N40W 

 SW20 



N50W 

 SWIO 



lii'ownisli tuff with no 

 andésite blocks. 



lomerate tuff with 

 andésite blocks. 



Diluvial corjl reefs. 



Alluvial deposits- 



Fig 7. — Geological Map of the Ibiruma Region. 



