Chap. X.] valudayur and abrialoor groups — pondicherry. 151 



PONDICHERRY ArEA. 



Chapter X. — Valudayur and Arrialoor Groups. 



The Pondicherry district is smaller than either of those previously 



Extent of Cretaceous described, but presents some Geological features 



^^ of special importance. It extends between the 



alluvial plain of the Ariancoopum and that of the Mercanum, the 



latter not intersected by any stream of importance, and lying at a low 



level, so that the greater part of it forms a perennial marsh, but in 



other respects it much resembles the alluvial plains already described, 



and is evidently due to the same series of physical causes. 



The area occupied by the sedimentary rocks is not more than 10 



miles in its greatest length, while in the other direction, viz., from the 



sea coast inland, it extends from 8 to 12 miles. The whole of this tract 



was, at a comparatively recent period, occupied 

 Of Cuddalore Group. . . i- ' i 



by a thin capping of the Cuddalore sandstones, 



ridges of which still extend along its East and "West limits, the former 



being known as the Red Hills of Pondicherry, while the latter, which 



has received no special name, may be designated as the Trivicary 



ridge. In the intermediate space, 5 miles in width, the Cretaceous 



Obscurity of Cretace- ^^^ks have been exposed by recent denudation, 



°^^ ^^^ ' and their out-crop being but little elevated above 



the level of the Mercanum alluvium, they are much obscured by 



the covering of older alluvium or regur, which occupies the whole 



denuded area, and renders it difficult to ascertain clearly the relations 



of the underlying rocks. 



The village and fort of Valudayur ( Verdoor), (the latter an important 



French outpost during the war of the Carnatic, 



Position of Valudayur. 



but long since abandoned to the peaceful 

 dominion of the plough, and existing only as a quadrangle of ruined 

 earthwork, surrounded by a dry ditch,) are situated about 10 miles 

 inland from Pondicherry, and near the border of the alluvial plain of 



