I06 HAYDEN: GEOLOGY OF SPITI. 
time, the series frequently bears a distinct superficial resemblance to 
the Blaini boulder-beds ; in each area there are usually two boulder- 
beds, separated from one another by a band of slate, while near ShiAn 
in the Pin valley the lower bed is underlain by a narrow band of rock 
consisting of small pebbles and angular fragments of white quartz in 
a dark, slaty matrix, and strongly resembling a similar narrow band of 
conglomerate which is found at Simla at the base of the boulder-beds, 
and has been traced from the Elysium spur round the flank of Jakko to 
the Sanjauli bazar. 
So much for mere lithological resemblance : when, however, we turn 
to the actual sequence, we find that there is considerable discordance 
between the two areas. This will be readily seen by a glance at the 
following parallel arrangement of the beds : — 
Simla. 
Carbonaceous slate. 
Dolomite. 
Boulder slate. 
Bleach slate. 
Boulder slate. 
Infra'B\a.\n\ slates, grits and 
quartzites. 
Spiti. 
Conglomerate. 
Slate. 
Conglomerate. 
Dolomite and slate. 
Carbonaceous slate. 
Cambrian slate, grits and quart- 
zites. 
It will thus be seen that the order of the beds above the lithologically 
similar slates, grits and quartzites is in the one area exactly the reverse 
of that in the other. This cannot be explained in the present case by 
subsequent inversion of the strata in the Simla area : it is^ however, 
possible to conceive of conditions under which deposition might take 
place simultaneously in some such reverse order in two areas not far 
removed from one another, but between the two, there would necessarily 
be found a gradation from the one series into the other. The beds 
between Spiti and Simla are so highly altered by dynamo- and con- 
tact-metamorphism that there is little hope of finding confirmation, or 
the reverse, and in view of the discrepancies between the two series, no 
attempt at correlation, on the strength of lithological resemblance of 
isolated members, could be justified. It has, however, been deemed 
advisable to draw attention to such points of similaiity as exist. 
( io6 ) . 
