202 >'v-3'-"-^1 FOOTE: SOUTH MAHRATTA COUNTRY. 



are mere subaerial (pluvial) re-aggregations of debris of rocks of the first 

 class. The age of the rocks of the second class can only be determined 

 as subsequent to the time when the country had acquired very nearly 

 its present features, as already pointed out when describing the Deccan 

 trap in the ghat region (p. 1 74) : the examination of the several iron- 

 clay formations there recurring only yielded evidence of negative cha- 

 racter, and therefore insufficient to determine positively their origin. 

 No doubt remains, however, that they are not in their original condition^ 

 but have been greatly altered by subsequent agencies of a subaerial nature, 

 and it only remains to be asked whether the rocks in question represent 

 altered lava flowSj or altered sedimentary associated rocks, or both 

 in parts. 



The correct reply to this question appears to be that they represent 

 both kinds of rocks, but that the iron-clays formed by alteration 

 of lava beds predominate vastly. Only one case was met with showing 

 strong evidence of the original sedimentary origin of an iron- clay : this 

 will be mentioned further on. 



Numerous sections occur in which the passage by subaerial de- 

 composition of the trappean rocks into argillo-ferruginous rocks may be 

 seen. Some of the best are on the great military roads crossing the 

 mountains by the Amboli and Phonda Ghats, where the decomposing 

 rocks have been cut into to some depth. It will be there seen that the 

 basaltic rocks graduate into a moderately hard yellowish brown or brown 

 earthy mass which encloses many nuclei of the original rocks in various 

 stages of decomposition. The upper parts of the decomposed mass 

 from which the nuclei have disappeared have undergone a process of 

 concretional solidification from the infiltration of surface waters holding 

 iron in solution, and are assuming the ordinary lateritoid appearance and 

 reddish color. This decomposition appears to be mainly due to the action 

 of water detained in the horizontal joints of the ro(?k, for in those flows in 

 which columnar cleavage has been developed, and in which but few 



( 202 ) 



