Chap. III.] post-cretaceous rocks. — (cuddalore sandstones). 35 



with mottled grits^ containing' numerous cavities filled with clay and 

 occasionally beds of clay. Resting upon these, occurs very generally a 

 highly ferruginous conglomeratic deposit of indurated clay, well known as 

 laterite."^ This laterite is in many places apparently inseparable from 

 the soft mottled grits, and seems to pass downward into them by imper- 

 ceptible gradations. 



The association, however, in some places of this laterite with other and 

 older rocks which will be presently described, together Avith its very pe- 

 culiar composition, structure, and appearance, renders it desirable that it 

 should be considered separately from the Cuddalore sandstones. We shall 

 therefore adopt a lithological distinction and divide the Cuddalore sand- 

 stone series into two groups. 



h. Lateritic deposits. 



a. The grits. 



As Mr. H. F. Blanford has already fully described the second 

 group, or " the grits,^^ our remarks on that group will be very brief. 



a. The grits. — These are well exposed at Tiruvakary, where they con- 

 tain many stems of large exosrenous trees. The e'rits 

 At Tiruvakary. o & to 



there are light coloured, and show much false-bedding, 

 a character which is particularly clear, because many of the laminae are of 

 bright, pink yeUow and purplish colors, which contrast strongly with the 

 general more or less white tint of the rock. The grits are more than 

 usually consolidated at this place ; not sufficiently, however, to make a good 

 building-stone. Soft mottled grits are also extremely well shown at vari- 

 ous points along the scai-p on the north side of the 

 Trivandipuram 



Cuddalore plateau, especially at Trivandipuram, on 

 the banks of the Guddalam river, a few miles west of Cuddalore. f 



* A deposit of identical character extends interruptedly from the neighbourhood of 

 Madras northwards to beyond NeUore. 



t The section of the Cuddalore series at Trivandipuram, on the bank of the Guddalam 

 river, near Cuddalore, was vividly recalled to my mind by the very similar show of colours 



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