10 6 GEOLOGY OF THE SON VALLEY, ETC. 



Vindhyans extend down into the low ground, and the older beds are 

 covered by recent deposits. 



We may now return to a consideration of the low hills by Salkhan 

 and Markundi. They are twice referred to in 

 Hills near Salkhan, Mf Mallet » s me moir, once in the memoir itself 

 (page 45), where the Salkhan hill is referred to as an inlier of the 

 transitions. In the note appended to the memoir, and embodying the 

 results of a later examination, this hill is referred (page 127) to the 

 basement beds of the lower Vindhyans. Mr. Vredenburg, who visited 

 these hills in the course of his survey of the lower stages in this 

 neighbourhood, took the same view, basing his conclusion mainly on the 

 presence of a glauconitic sandstone very similar to one found at 

 some places among the basement beds. 



Closely connected with the question of age of these sandstones is 



that of the limestone at Markundi, which was regarded by Mr. Mallet 



as the equivalent of his No. 7, by Mr. Medlicott and by Mr.Vredenburg 



as No. 2, or as the limestone of the basal stage. Mr. Mallet's ascription 



of this limestone to his No. 7 is with difficulty reconcilable with his 



reference of the Salkhan sandstones to his No. 1 ; on the other hand, 



the relation of the Markundi limestone to the nodular shales west 



of the Ghaghar is inconsistent with its reference to the basal stage, 



and it must be Mr. Mallet's No. 7 or some other limestone in the 



basal stage. This being so, it is difficult to account for the absence 



of the porcellanites anywhere round the Salkhan hills if these are 



formed of the basement beds, but all difficulty disappears if we 



regard them and the Markundi hills as formed by hard sandstone 



bands in the Kheinjua stage. The general dip along the axis of the 



open anticlinal, by which the boundary of the upper Vindhyans is 



thrown to the south, is very small, the Kheinjua outcrop should, 



consequently, have a great breadth in an east and west direction here ; 



and if we had the lowest beds of the series brought up to the surface, 



there would be no room for their exposure, nor would it be easy to 



account for the absence of outcrops of the porcellanites without 



( 166 ) 



