90 SMITH: GEOLOGY OF MIKIR HILLS IN ASSAM. 



" overlaid by calcareous shales containing large nodular masses of 

 limestone." This description suggests a similarity to the shale- 

 series below the Nambor falls, rather than to the white shales and 

 sandstone associated with the Nambor coal. But throughout the 

 whole section of the shale-series, as seen on the Haria Jan or the 

 lower Nambor, there is no trace of coal. The age of the Nambor 

 beds must, therefore, remain, for the present, in doubt. 



I have never met with similar white pyritous sandstone in the 

 Mikir Hills, nor have I seen any nummulitic coal. If the Nambor 

 coal be cretaceous, it is strange that no trace of cretaceous beds 

 should occur in the lower Nambor or the Haria Jan. 



Correlation of the Mikir Rocks. 



The oldest rocks of definite sedimentary origin in the Mikir 

 hills appear to be the Longloi coal-bearing shales, which underlie 

 the nummulitic band, and are presumably of cretaceous age. They 

 have no very close resemblance to the Shillong cretaceous beds, 

 which Medlicott describes 1 as sandy throughout, but showing at 

 Maobelarkar a small section of carbonaceous shales and coal. The 

 nearest cretaceous rocks are those of the Kopili river, described 

 by LaTouche. 2 They apparently consist chiefly of some hundreds 

 of feet of fine grained sandstone, but contain some coal and car- 

 bonaceous shale. The cretaceous beds in any case die out north- 

 wards in the Mikir Hills, and the Longloi shales and coal apparently 

 represent their last occurrence in this direction. 



There can be no doubt as to the eocene age of the nummulitic 

 band, and it is possible that the overlying shales may be eocene also, 

 corresponding to the coal-bearing ( Ghazij shales' of middle eocene 

 age in Baluchistan. But the total disappearance of nummulites im- 

 mediately above the limestone, and their absence in the shales, even 

 though marine shell-beds are present in the latter, are strong evi- 

 dence that the shales are of post-eocene age. 



' Mem. Geol. Sur., lnd., Vol. VII, Art. 3, PP. 18—33. 

 2 Rec. Geol. Sur. Ind., Vol. XVI, Pt. 4, pp. 199-201. 



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