74 S. Kawasaki 



the stoped Pre-Cambrian sedimentaries. Gold, which is the most 

 important mineral in Korea, is mostly obtained from the quartz veins 

 found in these rocks. 



Chosen System:— The System, also known as the Korean For- 

 mation, is ap})arently a continuous sediments of an enormous thickness. 

 It is divisible into two Series, the lower or the Yotoku Series and 

 the upper or the Grreat Limestone Series, which are conformable with 

 each other. The Yotoku Series consists of the basal quartzite or con- 

 glomerate and shale with intercalations of thin limestone beds, and 

 lies unconformably on the Pre-Cambrian rocks, their dips commonly 

 being different. It is referred to the Mant'o shale of China by the 

 lower Cambrian Trilobite, Bedlichia cliinensis found in the shale of 

 this Series. The Great Limestone Series consists of a thick limestone 

 with intercalated shale, and its lower horizons yield some Middle 

 Cambrian trilobites and brachiopoda, while its upper horizons contain 

 some Ordovician tiilobites, cephalopoda, gasteropoda and brachiopoda. 

 A graptolite was also found in a shale intercalated in the limestone. 



Of the useful minerals found in this System, iron, zinc, lead and 

 silver ores are of importance. 



Heian System :— The system is also of an enormous thickness 

 and divisible into four Series, all conformable with one another. The 

 lowest division, called the Koten Series, rests apparently conformably 

 upon the Great Limestone Series and consists of alternations of sand- 

 stone, shale and limestone. From some limestone beds of the Series 

 were obtained some foraminifera, corals and brachiopoda. One of the 

 foraminifera was identified by Prof. H. Yabe with Schioagerina 

 princeps. The next division is of terrigenous origin, consisting of 

 sandstone and shale, and intercalates promising anthracite seams, and 

 yields many Permo-Carboniferous plants. This division is called the 

 Jido Series. The third one, called the Kobosan Series, is also terrige- 

 nous, and passes below into the Jido Series and above into the next 

 Green Series. It consists of shale and sandstone of variegated colours, 

 and in general intercalates thin anthracite seams. The Series also 

 affords plant fossils, among which many Triassic ones are found. The 

 uppermost Series named the Green Series is a thick complex of 

 alternating layers of sandstone and shale mostly of green colour and 

 calcareous in character. Determinable organic remains have not yet 

 been found' in it. 



