JOURNEYS THROUGH KOREA. 173 



of wet-gray marl and gray, compact, calciferoiis sandstone, turn- 

 ing red on weathering. As it is more closely related in its 

 rock nature and stratigraphy to the preceding than to the one 

 next succeeding, I am rather disposed to include it in the Lower 

 Kyöng-sang formation, and to consider it as a part of the Nak- 

 tong series. 



No. 3. — The ' Red Formation ', is composed of variously- 

 coloured beds of marls which through weathering become choco- 

 late-brown, purple, red, carmine-red, and orpiment-yellow, thus 

 giving an unearthly aspect to the landscape. At its base the 

 rock is sometimes conglomeratic consisting of granitic gravels and 

 porphyrite blocks cemented with a sandy matrix. The con- 

 glomeratic bed marks the beginning of the " red formation ", and 

 sometimes shows a slight discordancy with the underlying clastic 

 complex, No. 4 (pp. 28 (footnote), 87). The orighially reddish or 

 greenish marls, which are sometimes sandy, are of tufaceous origin 

 consisting of detritus of porphyrite, splinters of quartz, hornblende 

 and plagioclase, cemented by calcareous and ferruginous matters' 

 (p. 87). They invariably effervesce with acid, and they differ from 

 the reddish-brown, slaty s dial s te in of Japan, which they 

 greatly resemble and for which they are mistaken. 



The red colour of the marl is, as I have already stated, 

 in part due to simple weathering, but that of the fresh marl 

 remains yet to be explained. According to Dr. Hornung (p. 31), 

 saline brine from the evaporation of sea- water brings about the 

 halurgometamorphosis in rocks by inducing the oxidation 

 and precipitation of red, anhydrous oxide of iron from eruptive 

 rocks rich in iron. The red colour in the present case may be due 

 to this cause. The richness of soil in soda, and the presence of 

 the so-called marl gold may be attributable to the same cause. 



