62 GEOLOGY AND MINERAL RESOURCES OF SIKHIM. 



north-western; and on the north side, as near Ralong, the dip is 

 mainly northern. The southern boundary between the DaHngs and 

 the gneissose rocks which passes a little north of Darjeeling was 

 shown by Mr. Mallet to be faulted. The eastern boundary passes 

 by Gantok, and the western by Pemiongchi. As in the_ case of the 

 Damuda-Tertiary and the Dallng-Damuda boundaries in the Sub- 

 Himalayas, both of these boundaries may represent " lines of original 

 contact, possibly modified by subsequent faulting."* _ The Baling 

 rocks would in this case have to be supposed as deposited in a lake 

 of which steep gneiss escarpments formed the sides: the lower 

 gorge of the Tista below its junction with the Rungeet which, 

 except close to its debouchure, is composed of Baling rocks, forming 

 the outlet of such a lake. The Balings, it should be noted in this 

 connection, unquestionably bear the impress of lacustrine, rather 

 shallow water deposits, false bedding being noticeable at places. 

 In fact, they recall to one's mind the micaceous clays and sandstones 

 of Tertiary age in the outermost fringe of the Sub-Himalayas. By 

 subsequent tangential pressure which caused their^ disturbance, the 

 Balings would be tilted up against the original gneiss escarpments in 

 such a manner as to present an appearance of conformable underlie 

 and of faulting. The greater metamorphism of the Balings at the 

 boundary between them and the gneissose rocks (a fact which has been 

 noted before) may be accounted for by the greater pressure to which 

 they would be subjected there owing to the resistance offered by the 

 older gneissose rocks. 



The Balings have suffered considerable disturbance. The slates 

 and phyllites frequently exhibit crumbling and contortion; and the 

 dips are, as a rule, rather high, being seldom below 45°. 



The following sequence of strata in ascending order is met with 

 near Chakang: — 



(a) Massive, coarse quartzites or quartzite sandstones with a 



lenticular band of carbonaceous shales. 



(b) Bark slaty shales which are cupriferous at places. 



(c) Phyllites passing into micaceous schists at places. 



(iii) Economic Geology. 

 1. — Copper. 



General remarks. — Copper ores are very widespread in Sikhim, 

 and constitute the main source of its prospective mineral wealth. 



•"Memoirs, Geological Survey of India," Vol. Ill, pt. 2, p. 102: "''"ol. XI, pt. 1, p. 48; 

 'Eecords, Geological Survey of iLdia," Vol. XXIII, pt. 4, p. 244. 



