STRAT1GRAPHICAL FEATURES. 5 I 



could make out three main divisions within the system, namely: 

 In descending order ; 

 Silurians. — 



/ 3. Series of quartz shales and slates. 



!2. Shales and silky phyllites with great thickness 

 of quartzites. 

 1. Quartzite, generally purple, with great thickness 

 ^ of conglomerate. 



Vaikritas and older gneiss • • 



The lowest division of the haimantas is seen in perfect sections 



in the narrow gorge of the Dhauli Ganga above 

 Niti (near the Kharbasiya encamping ground), 

 at Milam, in the sections of Lissar and Byans, in the Nilang sections 

 north of Gangotri, and also in the Upper Pin river valley of Spiti. 



In the Dhauli Ganga valley the lower haimantas consist chiefly of 

 purple quartzites in which thick deposits of a coarse conglomerate 

 and breccia are frequent ; the latter are mostly made up of rolled and 

 sub-angular fragments of rocks belonging to the crystalline area, and 

 amongst them large boulders of quartzites and gneissose rocks seem 

 to predominate. The matrix in which these boulders are firmly em- 

 bedded is nearly always a hard, flinty quartz rock, sometimes parti- 

 ally schistose. It is by far one of the most characteristic and easily 

 recognized horizons of the Central Himalayas, and is invariably met 

 with in all haimanta sections which I have seen. 



In the Niti sections, and in fact also in most of the others, the 

 matrix is frequently a deep purple quartz rock, in which the lighter 

 coloured boulders of white and grey quartzites and metamorphic 

 rock stand out conspicuously. Identically the same rock may be seen 

 in the Spiti valley, and in very great thickness also in the Ja"dh Ganga 

 area. In all the eastern sections, from Milam to the Kali river, this 

 purple conglomerate forms an easily recognized horizon amidst the 

 lower beds of the haimanta system. 



The boundary between this system and the crystalline rocks does 

 Boundary with the not seem ver y sharply defined in the eastern 

 vaikntas. sections ; at Milam, for instance, there is seem- 



E 2 ( 51 ) 



