4-6 GEOLOGICAL NOTES ON ASSAM. 



the line of flexure at the south limit of the area^ by rocks which con- 

 formably overlie it, presents no difiiculty, only g-iving us a larger measure 

 of the action and re-action by which this feature was determined. If 

 the suppositions I have made in this paragraph are correct, the bend 

 northwards of the nummulitic outcrop must commence close to Moralli 

 Poonjee, the extreme south-eastern point of Mr. Oldham's map, and 

 where there is a note to the effect that " limestone is said to extend from 

 this to the Assam Valley .'' I can only repeat that it and I did not meet 

 on the road, nor yet in the Assam Valley. 



The double condition to which I have attributed the limitation of 

 the region of disturbance is not so apparent in 

 North Cachar as in the Cossyah District. The 

 contorted and altered rocks forming the basis of the region I speak of 

 as table-land have not been observed within many miles of the southern 

 edge of this area ; still their last appearance in the Chongun is higher 

 than the contact at the Kopili falls, ten miles further north. The corre- 

 lative features of a rapid thickening of the younger deposits beyond 

 the table-land area can also be only conjecturally indicated at present. 

 If all the rocks of the Burrail range, and of the deeply excavated valleys 

 between it and the table-land, are of the same horizon as those forming 

 the table-land, the question at issue can scarcely be raised. Three thou- 

 sand feet, which is the most we are entitled to assume for the undis- 

 turbed rocks atGoomaigoojoo, would never satisfy the demands of the 

 Burrail section. There can be no question that the actual strata 

 of the table-land gradually assume the high easterly and southerly 

 underlie; the massive sandstones are so seen in the gorge of the 

 Diung to the south of Goomaigoojoo. The rocks out of which 

 the longitudinal valleys have been excavated are, however, principally 

 thin-bedded, sub-slaty shales : in the stream below Asaloo they are 

 seen in considerable tliickness without any sandstone. Similar 

 beds, but very subordinate to the sandstones; occur in the Goo- 



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