00 



Sandstones con ta ining 



[NO. 7, NEW SERIES, 



stones and conglomerates, sometimes of a deep red color, at others 

 mottled and banded with various colors, and containing occasion- 

 ally, although rarely, large unrolled fragments of silicified wood 

 precisely similar to those found at Trivicary. 



To the east of the Oosatary tank the sandstones are especially 

 well exposed in the gullies cut by several small streams flowing 

 down to the tank, and may be seen at several places, resting on 

 finely grained soft yellow sandstones which contain in some places 

 a few very imperfect but recognizable cretaceous fossils and are 

 proved to be the upper beds (as here seen) of the cretaceous series. 

 It is therefore beyond the remnant of a doubt that the coarse sand- 

 stones of Pondicherry, are newer than the cretaceous beds.* 



The next step in the investigation is to trace out the identity of 

 these beds, and the coarse grits at Trivicary. In ascertaining this 

 point the greatest care has been exercised, and the two areas were 

 repeatedly and alternately visited in order to compare thoroughly 

 the two series. The results of this investigation are : — 



1st. The sandstones at Trivicary, and those at the Oosatary tank 

 present precisely the same lithologic characters. They are both 

 very coarse ferruginous grits containing minute particles of what 

 appears to be kaolin interspersed with the grains of sand and giving 

 them a white speckled appearance. In both localities, they are 

 very variable in color, but the most characteristic varieties both at 

 Trivicary and the tank are variegated, with irregular bands of lilac, 

 pink, and yellow, frequently very brilliant in color. They are both 

 occasionally somewhat conglomeritic especially towards the bottom, 

 and in their false bedding, their irregular segregation and all litho- 

 logical characteristics, they are quite undistinguishable. 



2nd. The Trivicary grits contain fossil wood in great quantity, 

 while the Oosatary beds contain it only very sparingly, but it is in 

 both places apparently identical, and in both cases perfectly sili- 

 cified and unrolled. Moreover, that the abundance of fossil wood 

 is a very local character, is proved by the fact, that in the evident 

 extension of the Trivicary sandstones to the North, the fossil wood 



* The extension of these sandstones to the south of Cuddalore is seen in many- 

 places resting on the cretaceous rocks very unconformably. At Verdachellum 

 they rest on the lowest beds of the cretaceous series whereas 20 miles to the south 

 of this, they are seen resting on beds about 3,000 feet up in the same series. 



