CORRELATION WITH SIMLA SERIES. 
103 
Chapter IX. 
CORRELATION WITH THE SIMLA SERIES. 
The correlation of the metamorphosed sedimentary beds of the 
lower Himalayas with beds of known age in the higher parts of that 
range has ever been one of the most ditricult problems with whicii 
the Himalayan geologist is called upon to deal. The apparent 
absence of fossils in the pre-tertiary rocks of the lower ranges and 
the discontinuity in the beds caused by the numerous intrusions of 
great masses of granite, leave us dependent entirely on lithological 
characters as a means, of correlating the rocks of different areas, and 
in the face of such extreme variations in character of the palaeozoic 
systems as are displayed in the sections of comparatively adjacent 
areas, such as Spiti and Kanaur, this method of correlation can be 
employed only with the greatest discretion. 
In the present chapter it is proposed to deal with those aspects 
of the question on which the recent survey of Spiti may have thrown 
a little more light, that is to say, the correlation of the various beds 
found at Simla, and in the Sutlej valley with their possible representa- 
tives among the higher ranges to the north. 
It is only within comparatively recent years that the real difficul- 
ties of this problem seem to have been realised, the earliest observers 
having been content to apportion, somewhat dogmatically, the vari- 
ous Simla beds among the fossiliferous rocks of Spiti. Subsequently, 
however, the question was studied more deeply by General McMahon 
and Mr. Oldham, who made detailed surveys of Simla and neigh- 
bouring areas and also visited both Spiti and Kashmir. The observa- 
tions are embodied in numerous papers published in the " Records " 
of this Department, and a summary of Mr. Oldham's conclusions will 
be found in the " Manual of the Geology of India." ^ Of the area in 
which these rocks and their representatives have been studied by 
Mr. Oldham, only two small portions have been visited by the present 
' Manual, 2iid Edn., pp. 132—138. 
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