STRATIGRAPHY. 



y 



there is no remnant of them to be found along the whole length of 

 the boundary between Marai and Chopan. 



In the western exposures the section is very incomplete, the 

 c . " . . . L greater part of the series having: been removed 



Subdivision into stages. • . & 



by denudation previous to the deposition of 

 the lower Vindhyan strata ; in the eastern exposures, where the sec- 

 tion is more complete, the series is divided into three principal 

 stages :— 



(3) Lower, sandstones and conglomerates. 

 (2) Middle, shales. 

 (1) Upper, sandstones or quartzites. 

 The divisions between these stages are not well marked, and 

 rocks of both types are found in every stage, though the prevailing 

 facies is, as indicated by the nomenclature, that of fine-grained beds 

 in the middle and coarser ones above and below. Conglomerates 

 are confined to the base of the series. 



The lower stage varies in thickness from 15 or 20 feet to 500 feet, 

 the variations being in part due to the horizon- 

 tal replacement of the sandstones near its 

 upper limit by shales, but principally to inequalities of the surface 

 on which it was deposited. Near the base of the series, but not 

 as a rule forming the lowest bed, a conglomerate is a frequent mem- 

 ber of the series, and is usually thickest on those sections where 

 the lowest stage attains its greatest thickness. 



Conglomerates, in the true sense of the word, are, however, of 

 somewhat rare occurrence in the series, and usually of small thick- 

 ness. Pebbles, on the contrary, are very abundant in the sand- 

 stones of the lower stage, usually tolerably well or perfectly rounded, 

 of small size, as a rule not exceeding two inches but occasionally 

 ranging to six inches in diameter. These pebbles are found scattered 

 through a sandy matrix in varying proportions, usually they are 

 separated from each other by several inches or feet of matrix, but may 

 occur in increasing proportion, till the rock finally passes into a 

 true conglomerate. 



( 9 ) 



