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HAYDEN: GEOLOGY OF SPITI . 
Chapter vr. 
RUPSHU. 
With the exception of the local peculiarities due to the uncon- 
formities between the cambrian and silurian, and carboniferous and 
permian systems, respectively, and which have already been noticed in 
the previous chapters, the characters of the stratigraphical systems of 
Spiti and Bashahr are so constant that detailed descriptions of a number 
of individual sections would be superfluous. Further to the north, 
hovvrever, in Rupshu, the beds have been so greatly altered both by 
dynamo- and contact-metamorphism, that their relations to the Spiti 
systems can be traced only with great difficulty. 
The valley of the Spiti river is bounded on the north by a chain 
Routes from Spiti snow-clad peaks and ridges, which constitute 
to Rupshu. the eastern extension of the Baralachar Range. 
From Spiti, three routes lead through this range to Rupshu— 
(1) via the Tagling Lk and upper PAri. valley; 
(2) vid the Parang Lk and upper Pdra valley; 
these two routes converge at about 15 miles below the Parang La; 
(3) from lower Spiti, vid Kurig and Kharak in Western Tibet 
(To-Tzo), along the lower Pdra valley, to Chumar and 
Ldm Tso. 
By taking the third route, the present writer was enabled to trace 
out the connection of the beds of the one area with those of the other, 
and it has now become possible to refer the metamorphic rocks of 
Rupshu to their comparatively unaltered representatives in Spiti. 
The high ranges between Spiti and Rupshu are composed chiefly 
, , . of rocks of mesozoic age, amongst which the 
Triassic beds m _ . . 
ranges between Spiti upper triassic coral limestone is a most conspi- 
and Rupshu. cuous and useful horizon. In many cases, 
especially in Rupshu, it has been converted by metamorphism into a 
white dolomite, but still retains its numerous corals. Below this 
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