166 CRETACEOUS ROCKS OF S. INDIA, [PaRT II. § 2. 



red, brown, and purple. This is doubtless in part due to infiltrations 

 from the surface, the red soil and laterite (which in this part of the 

 country is for the most part only a local form of the red soil,) being 

 the original source of the iron, but much of the iron must have been 

 introduced contemporaneously with the formation of the beds, as they 

 have occasionally highly ferruginous bands intercalated with them, and 

 in general the whole mass is evenly tinted with the peroxide of iron to an 

 extent that can scarcely be due to superficial infiltration. There is also 

 a considerable quantity of carbonate of lime, distributed through the 

 beds, in the form of irregular pipe-like concretions, which penetrate the 

 coarser beds in every direction. These may be due to the segregation of 

 the calcareous matter originally disseminated through the rocks, or they 

 may have been derived from calcareous accumulations, (broken shells, 

 &c.,) which ha,ve covered the surface at some period subsequent to 

 the denudation of the country. 



Unfortunately no sections are exposed of sufficient depth to enable 

 us to ascertain whether such infiltrations are merely superficial ; but the 

 fact that these tubular concretions are chiefly confined to the coarse 

 grits at the base of the group, leads me to infer that the former is the 

 more probable explanation of the phenomenon. 



The Cuddalore sandstones are generally unfossiliferous. Indeed, the 



^.,. ., , , ,, T only exception to this rule is that already noticed 

 Silicified wood the only J r j 



organic remains. ^jy Captain Nowbold, Mr. Kaye, and others, viz., 



the occurrence of large trunks of silicified wood at the base of the 

 group at Trivicary and other places near Pondicherry, and of fragmen- 

 tary plant remains, too poorly preserved however to be determinable, 

 not far from Trivicary. 



In general the bedding is not very clear, but, when visible, it is 

 either horizontal, or dips very gently to the East, 



■'^'^'^'•^'"^* (i. e. seaward) at an angle not exceeding 2°. In 



Trichinopoly it must rest very nearly horizontally on the Cretaceous 



