98 AIÎT. 2. — B. KOTÔ: 



moiintain-foot I unexpectedly met with a biotite-hornblende-ande- 

 site^^ of a tracliytic appearance and structure with a glassy 

 hyalopihtic groundmass. At the mouth of a gorge in the moun- 

 tain with a chyu-mak on a meandering streamlet, one again finds 

 the green quartz-hornblende-porpliyrite of the Upper Ivy öng- sang 

 formation. The ascent over the same rock to the Ka-na-chhi 

 (375 m) is rather steep, but the descent to Seup-kol is gradual 

 on white spotted porphyrite intercalated with breccia, producing 

 contact-metamorphism on the flinty tuffite of the " black sliale 

 series." 



From Seup-hol our route -took a northwest by west course 

 through a gorge in the banded flinty rock (the strike N. 20 E., 

 the dip 50° N.W.) The wind-gap traverses the highest part of 

 the coastal ridge in its deepest core which is penetrated by a 

 biotite-granite at its base. At the west outlet {Sal-sid-mak, 110 

 m) of the gorge, an erosion and gravel terrace two-kilometers 

 in extent was seen flanking the west foot of the mountains. This 

 type of land feature rarely occurs in Korea, and indicates that 

 the east coast is gradually emerging from the sea. The topo- 

 graphy opens to the west, but the rock- character (the strike N. 

 20^ E., the dip 5 — 10' N.W.) remains the same as far as Kfjong- 

 jiju, well exposed along the Söng-chhyön'^ river (PI. XXIII. j^^. 1). 



1) This young efifiisive is at one extreme of a series leading tbroiigh various mo<lifàcations 

 of felsophyres and masanites to granite. These occur close together in South Korea, probably 

 representing the i^roducts of one magma, differing only in structure conditioned by the 

 «lepth at which they had consolidated. The green diopside — and hornblende- porphyrites, some- 

 times qnartz-bearing, occurring so characteristically in the uppermost Kyöng-sang formation, 

 seem to be the basic faciès of the same magma. A field is open here for the petrologist to 

 trac« out the details and relationship of the members of this interesting and geologically im- 

 ixjrtant series of rocks. 



2) a ;ii 



