g8 HAYDEN : GEOLOGY OF SPITI. 
found to be practically continuous with the intrusive masses found 
below Kurig on the lower Pira river. 
In Spiti the granite is found intrusive only in the oldest palaeozoic 
bedsj but at Lio in Kanaur silurian limestones are 
Age of granite. .11 . 1 • 1 i , 1 
penetrated by numerous vems which have altered 
the sedimentary rocks, the chief product of alteration being wollaston- 
ite, which occurs in great quantity about one mile above Lio on the 
right bank of the Spiti river. 
In Rupshu the granite is intruded into the carboniferous and 
permian schists, while in Western Tibet it would appear to occur in the 
triassic limestones ; in the latter case it was only seen from a distance, 
and the correctness of the observation cannot therefore be vouched for. 
So far, therefore, as concerns the area dealt with in the present 
memoir it is only possible to assert that the age of the granite is post- 
carboniferous or possibly post-permian. 
In this connection it is interesting to note that a pebble of biotite 
granite was found in the permian conglomerate 
Pre-permian granite. , r , ■ r 1 ^ . . . , , t> 11 
on the lert bank 01 the Spiti river below uankhar 
which proves that a pre-permian granite must have existed in the area 
from which the materials forming these conglomerates were derived, 
that is to say, to the south and south-west of the Spiti valley. 
Basic rocks. 
Basic rocks, chiefly of doleritic type, occur at several localities in 
Spiti and Kanaur. They are in all cases intrusive, and no signs of 
contemporaneous or interbedded ashes or lavas have been found. 
The localities at which intrusions have been noticed are : Depsa 
E. G., in the valley of the Parahio; Muth in the 
Localities. t-. r • i • <-. , ' , 
Pin valley ; Fo, Lari, and opposite Sumra mthe 
valley of the Spiti river ; on the Shalkar (or Sumra) Pass between 
Sumrd and Shalkar, and at Ka between Shalkar and Lio. 
The Deps5 rock was probably originally an augite-norite, but 
has undergone much alteration. It consists of 
Depsa : augite-norite. , , , 
lath-shaped plagioclase, greatly decomposed 
( 98 ) 
