174 ART. 2. — B. KOTÔ: 



No. 2. — The complex of bîacl- and sometimes reddish-brown 

 marly shale and greenish flinty tuffite is, like the preceding, of 

 pyroclastic origin, and both are conformable in stratigraphy. 

 Search was made in vain for fossils in the black marly shale. 

 If there be any, they would be of great service in determining 

 the age of the Upper Kyöng-sang beds. 



A characteristic of this horizon is the appearance of banded, 

 green and yellow, indurated tuffite. It is a compact, flinty, 

 hornstone-like rock the origin of which is not wholly clear to 

 me. Seen under the microscope it consists of coaly particles 

 •and biotite in the quartz-feldspar ground, the yellow bands being 

 extremel}' rich in epidote granules. Its flinty texture may be in 

 part due to the contact-metamorphic influence of the overlying 

 green porpliyrite. No. 1. But the constant occurrence of this 

 greenish, flinty, indurated tuffite in tlie definite horizon needs 

 some other explanation which I am not able to offer in the 

 present state of my knowledge of the complicated geology of the 

 region. Perhaps induration and silicification of tuffite under sea- 

 water in connection with submarine eraption of porpliyrite had 

 much to do in bringing about the hornstone-like texture of the 

 rock. In short, the rock has undergone a diagenetic process. 



It is also one of the characteristics of this complex that 

 auriferous quartz veins are of frequent occurrence in it, and I 

 give to this gold the name of the 'black shale gold ' in con- 

 trast to the 'marl gold' already referred to. 



No. 1 , the green eruptive, is the uppermost member of the 

 whole Kyöng-sang formation. The mode of its occurrence is so 

 peculiar and characteristic as not easily to be explained. Por- 

 pliyrites occur in an extensive sheet underlaid by thick beds of 

 fusion-breccia of the same. They often cover the laccofithic and 



