114 A.ET. 2. — B. KOTO 



I. The Profile betwesn CHYON-JYU and NAM-UON 



The geology of the envh-ons of Chu'ôn-jiju (PL XXVII. figs 

 2 and 3) is rather compHcated and interesting. 



I shall first of all take up the section between the towns of 

 Chißn-jiju and Nam-uon across what I call the No-nßng^ ridge ^^ 

 on the highway of south-west Korea tln^ough the Man-mal- 

 Ivan'^ pass. It was Mr. Yabe who made the trip here, and I 

 follow him giving brief remarks on the rocks from a suite in his 

 collection. (See the annexed sketch map.) 



I have already spoken of the granite of Nam-uon in my 

 second traverse '\ It is a light-colored, shghtly pinkish (ortho 

 clase) coarse biotite-granite, showing slight indications of schisto- 

 sity and porphyritic structure. It is pierced through by a dyke 

 of wet-gray compact rock which, under the microscope, is seen 

 to consist of microphenocrysts of feldspar and biotite in sericitic 

 groundmass with speckled polarization. The phenocrysts are all 

 decomposed, and what is remarkable is that the feldspar is en- 

 tirely replaced by calcite. Farther north, tlie rock is changed 

 into " Augengneiss " with titanite, the white lenticular feldspar 

 which makes " eyes " being 2 cm in size. It is not known whether 

 or not the granites are parts of tlie same rock. The " Augen- 

 gneiss " is variously traversed by dykes of tourmaline rocks. 

 lm-sil From Im-sil ^^ we entered the Mesozoic terrane, and the first 



rock met wdtli was a conglomerate consisting of gravels of gray 

 schistose rock and quartz, cemented with arkose matter. It is 



1) "Au Orograi)liic Sketch of Korea." This Journal. Vol. XIX. Article I. page 14. 



2) ^ .H ^ 3) See ante, pages 78 and 79. 

 1) ffi n 



