OBRUTCHOV ON THE NAN-SHAN. 6 1 



valley of the Sou-lai-khe [Su-lei-ho].* In the continuation of the Alexander mountains 

 to the west-northwest, or a little to the south of this line, rises the Ta-sioue-shan [Ta-sue- 

 shan, Great Snowy Range]. 



The Richthofen range is 50 to 60 versts across and may be divided into several groups 

 of folds, of which the first without doubt exceeds 20,000 feet, 6,000 meters. At the northern 

 base, near Tsin-fo-sy, southeast of Sou-tcheou [Sii-chou], there is a mass of granite, but 

 although the granite rises rapidly it does not extend far into the mountains. It is followed 

 by a band of upper Carboniferous with beds of coal, inclined to the southwest; then by 

 lower Carboniferous with Productus striatus; by a red and green Devonian sandstone; 

 and finally by quartzites and limestones which are probably Silurian. Before the first 

 summits of the range are attained the beds are already inclined towards the north, and all 

 the ridges of the Richthofen range may be considered as closely appressed folds of anal- 

 ogous Paleozoic terranes, which are tilted to verticality or overturned toward the south. 

 There seem also to be overthrusts. Possibly some of the coal-measures belong to the 

 Angara series. At the southernmost divide called the Tsin-pin-ta-pan (14,000 feet, 4,220 

 meters) and even above this pass strata of the Gobi series lie in discordance against the 

 southern base of the Richthofen mountains ; they everywhere dip very steeply toward the 

 valley of Khoun-tschoui, which forms the limit of the slope of the To-lai-shan. * * * 



Still further to the west-northwest on the middle course of the Sou-lai-khe [Su-leii-ho] 

 there occur in the Paleozoic series of the Richthofen mountains red and green sandstones, 

 in the midst of which are interbedded layers which contain Devonian fossils (Rhynchonella 

 alinensis according to Tschernyschew) . Obrutchov mentions in another locality Spirifer 

 elegans and Spirifer anosoffi. [Central Asia, n, pp. 9 and 10.] 



We may here interpolate an extract from Obrutchov's own account :f 



On the southern slope [of the Richthofen range] we see a thick series of supra- 

 Carboniferous deposits forming one of the southern ridges, the divide of the range. They 

 strike north-northwest diagonally to the range, and dip steeply on both sides. Below the 

 peak Yang-k'ou-er appear more ancient formations: gray sandstone and shales slightly 

 metamorphosed, which I consider ancient Paleozoic. They do not resemble closely the 

 ordinary metamorphic sandstone and schists of the Nan-shan and other parts of central 

 Asia. They may be Silurian, or perhaps still older. Fossils have not been found. This 

 series is much contorted in various directions, east-northeast, east-west, and west-north- 

 west. Apparently it formed the range when the supra-Carboniferous sandstones were 

 deposited at its southern base ; now it forms the southern slope of the main ridge. The 

 remaining part of the Richthofen range represents an enormous anticline, which is over- 

 turned southward, and on the limbs is composed of a great thickness, 2,800 to 3,500 feet, 

 850 to 1,050 meters, of conglomerates, mostly of red color; in the southern limb they stand 

 almost perpendicular and in the northern they dip inward. Near the axis of the fold the 

 conglomerates are replaced by red and green sandstones and shales with thin layers of 

 conglomerate. These strata apparently form secondary steep folds. The strike is west- 

 northwest, parallel to the modern Richthofen range, as might be expected, since the range 

 has been formed in its present position by the dislocation of this series. The thickness of 

 the conglomerate of the southern limb forms the crest of the mountain chain, with its 



*The French spelling kh is a transcription of the Russian xe, pronounced as xo, and rendered in 

 English ho, the Chinese for river. 



t Central Asia, North China, and the Nan-shan, vol. n, p. 145. 



