PRE-JURASSIC SEDIMENTARIES. 
series, which so far as we know at present, has no counterpart 
in the Himalaya,^ but has, on the other hand, many points of resem- 
blance to the oldest member of the Archaean group in the Peninsula 
and Burma. At the same time the similarity of the Daling series to 
certain facies of the Dharwar system further emphasises the striking 
analogy between the unfossiliferous rocks of Sikkim and the Archaean 
group of the Peninsula. 
In the Chumbi valley, as in Sikkim, the prevailing rock is foliated 
biotite-granite, which forms the ranges on either side of the Ammo 
Chu and runs on eastwards into Bhutan. Near the junction of the 
Ammo and Khongbu rivers, it includes micaceous and quartzose 
schists, possibly in part of sedimentary origin. ^ 
Higher up the valley at about a mile and a half below Gautang a 
band of dark grey limestone crosses the road, striking approximately 
east-west ; but the sedimentary rocks in this part of the valley are of 
no great extent and soon give place again to granite which extends 
to within a short distance of Dothak, where it is found in contact with 
the stratified rocks of the Phari plain. 
CHAPTER III. 
PRE-JURASSIC SEDIMENTARIES. 
A glance at the geological map will show that throughout Sikkim 
the northern boundary of the crystalline zone adheres closely to the 
northern slopes of the highest peaks, thus enclosing the Kinchinjunga 
group, Chomoyumo, Kangchenjhao and Pauhunri, but to the east 
of the last-named, it turns southward and runs below the Khongbu 
valley and the Phari plain into Bhutan. To the north-east of Phari the 
crystallines re-appear, forming the peak of Chomolhari, — which is 
' Since the above was written pyroxenic gneisses exactly resembling those of 
the Central Provinces have been found by my colleague, Mr. L. L. Fermor, near 
the Pindari glacier in Kumaon. 
2 The mica schists of the Chumbi valley are stated by Col. Waddell [" Lhasa 
and its Mysteries "(1905), P- 492], to be merely micaceous varieties of the gneissose 
granite ; much of the schist however is a garnet-sericite rock, such as is usually 
regarded as the result of the metamorphism of an argillaceous rock of sedimentary 
origin. 
( ) 
C 2 
