GEOLOGIC STFJUCTURE OF THE RIUKIU CURVE. 



53 



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S:3raiyi.iii:i, ,f ,,,1| 



Pig. 9.__Vie\v of Nosoko volcano seen from Nosoko-zaki on the west. 



sist of pyroxeiie-aiidesite. Stocks of the same rock are found on the 

 north of Xosoko, in the south- western part of C and the north-west of 

 Kabira, and extend from NE to SW. I found two dykes of pyroxene- 

 andesite on the nortli of Miyara and another on the south of Omoto- 

 dake. Dykes and stocks of the same rock are also found in the south- 

 western and north-eastern corners of Kobatna-jima and in the nortli- 

 eastern corner of Iriomote-jinia. Propylite sheet is exposed on the 

 coast, north (^f Yasura in Ishigaki-jima. 



The andésites of tlie Yaeyama subgroup pierce through the 

 Palaeozoic sediments Ijut not throu2;h the Tertiary. Thouo^h some 

 places in Ishigaki-jima show the Tertiary rocks in contact with the 

 andésite, vet there is no contact chan^'e nor tectonic disturbance in the 

 former. The ao-o-lomerate-tutf (^f andésite alternates with thin non- 

 tufaceous sediments. This shows that the deposition of the Tertiary 

 rocks of Ishigaki-jima took place either contemporary Avith, or else 

 immediately before or after the andésite eruption. The regular bedding 

 of the Tertiary, as well as that of the PaUcozoic sediments of Ishigaki- 

 jima is characteristic, showing a single folding pressure after the 

 eruption of the volcanic rocks, in contrast with the Tertiary of Ishi- 

 gaki-jima, that of I ricmiote-jima has a very great thickness, contains 

 several coal-seams, and is generally inclined to KW in the western, 

 but not in the eastern part. Although this Tertiary is doubtless a 



