PAUT 4.] 
203 
Foole ; Geology of North Arcot District. 
Avith locally a fine grey shale, in which some fragmentary stem markings were 
noticed. All these have a low dip of 2“ to 3° east.” Above all is a fenmginons 
sandstone, 1 to 1\ feet thick and of rather coarse texture. • . n, 4 
The other three patches which are seen crossing the road consist of a hard 
S...1 Cfrop. .Orth ^vpsriicially ge»»lly J™gino™ s.Bd.t™.,, '^“1” » 
of Trivatur. character to the lowest bed of the above section. A patch 
of similar beds covered by a little yellow sandstone occurs east of the road about 
two and half miles north of Trivatur. Between three and four miles north-east of 
Trivatur and east of Perintur occurs a little hard grey sandstone, about 10 feet 
thick and weathering of a reddish-brown. 
Three miles to the north close to Marianur, a largo amount of debris of a red¬ 
dish ferruginous sandstone covers the ground, and close to the village on the 
south this is seen in situ overlying a coarse brown felspathic sandstone, of which 
but little is seen, though it has been thrown up in considerable quantity from well 
and tank sections. In the village a tolerably hard yellowish-brown sandstone is dug 
out of bowries (large square wells) and has been used to a small extent for building. 
A similar brownish-yeUoAV sandstone is also dug out at Shamanguri, two and half 
miles to the north-west. 
A few more small patches might be referred to, but they offer no special 
characters of interest. 
The numerous patches just referred to are, without exception, of small size, 
the largest not being more than two miles long by one in width at its widest 
part, and the great majority greatly less in dimensions. 
The Lateeitic Foemations. 
Of the numerous spreads of the lateritic rocks which fringe the eastern coast 
of the peninsula between Latitude 13° 50' and 11° 20' north, only a few extend 
inland sufficiently far wesWard to come within the limits of the North Arcot 
district. There is, horvever, abundant evidence that these rocks had formerly a 
much wider westerly extension, and that their present western limits are bound¬ 
aries of denudation and not of deposition. The chief outcrops of them [occur 
along or close to the ea,stern boundary of the district, and are in most cases 
seen to rest upon the Upper Gondwana beds, to which, however, they are markedly 
unconformable, and in many cases they overlap on to the gneiss. All the out¬ 
crops of importance lie to the north of the Palar. 
The most southerly patch of lateritic beds requiring notice lies between the 
north bank of the Palar and the alluvium of the Kortelliar, about twelve miles 
east of Arcot toAvn. It is in reality only the extreme western end of a vey large 
lateritic area which occupies further eastward nearly the whole of the Conjeveram 
taluq. The prevalent rock here seen is of a red sandy variety Avith scattered 
patches of ferruginous gravel. 
To the north of tho Kortelliar the laterite occurs in the form of an enormously 
coarse shingle or generally uncompacted conglomerate, such 
Shingle conglomerate. south of the Chinnamapett rail- 
Avay station. Further north tho surface of the Pyanur area of Rajmahal beds is 
widely covered with an equally coarse shingle associated Avith large quantities 
