80 SUB -HIMALAYAN ROCKS OF N. W. INDIA. [CHAP. Ill 



depends upon this section at Subathu, doubt in the same degree must 

 rest upon the proposition I am now attempting 

 to establish. My impression, however, is that the 

 slate rocks here in contact with the nummulitic strata belong to the 

 Infra-Blini series. As long as this hesitation remains, sufficient weight 

 must be given to the general argument for the pre-nummulitic denuda- 

 tion of the Krol group, based upon the evidence of the outlying bands 

 in the valleys to the north-east of Subathu. That argument seems to 

 me sufficiently strong to stand by itself. 



The conditions described for the small isolated or semi-isolated bands 



of nummulitic strata are applicable on a grand 



The whole area but an L ± 



outlier - scale to the whole area of the Subathu group ; it 



is itself, to some extent, contained in a great trough of depression or of 

 folding ; it is now almost insulated from all connection with succeeding 

 deposits, upon a ledge of the older rocks ; — along the whole of its south- 

 west boundary there is scarcely a section in which the older rock does not 

 appear beneath the nummulitic beds, thus forming the contact rock with 

 the middle Sub-Himalayan group. This state is most evident in the 

 north-western portion of the area : from the Sutlej to beyond the Ghumber 

 there is a well defined ridge of limestone, underlaid by black shale, enclos- 

 ing the nummulitic rocks on the west. It is not only along the boundary 

 of the group that the underlying rocks appear : in more than one place 

 of the eastern part of the region, in the deeply cut valleys, the black shales 

 weather out from below the brown nummulitic clays ; the best example 

 I know of is in the valley of the Guggur, north of Morni. In these posi- 

 tions it is often difficult to distinguish between the two rocks ; the best 

 general test is the thin, sharp bedding, and frequent fine lamination of 

 the Infra-Krol strata, as contrasted with the thick amorphous beds of the 

 nummulitic clays. The nonappearance of the Krol beds themselves, in 

 situations such as this, gives conclusive proof, if any were still needed, of 

 the extensive removal of that group prior to the nummulitic period. 



