Fvoli': Geology of North Arcol District. 
198 
PART 4'.] 
referred to) extends northward info the Vellore hills, and forms a considerable 
part of the main ridge of the hill group. 
Beds of magnetic iron occur here and there in the south-west corner of tlie 
district, e. g., to the soTith of Gudyatam (Goriattuin), 
Magnetite beds. ^ south of the great tank, and again two and a 
half miles west of Vellore railway station. These beds are small, but interesting, 
as there can be no doubt that they are representatives of some of the numerous hods 
occurring south of the Javadi hills in Salem district. Others of these richly 
ferruginous beds are in all probability represented by various quartzose gneiss 
beds, very strongly iron-stained, which occur in this quarter. The quartz of these 
beds'is stained of purplish or reddish color, and frequently shows a brown fen-ugi- 
nous incrustation in the cavities between the lamina?, as also numerous little 
cavities in the lamination which appear once to have been filled by some mineral 
or other now wanting. These beds have a striking rosomblance to the poorly 
ferruginous parts of many of the typical magnetic iron beds of the Salem region. 
Good examples of these iron-stained beds are to he seen in the Vellore hills and 
in the large detached hill three miles south of Vellore. 
Probable representatives of the magnetic iron beds are also the numerous 
Qiiartzo-femiginous quartzo-ferruginous beds noted by Mr. G. M. Oldham in 
beds. the Arcot and Wandiwash taluqs. His notes unfortu¬ 
nately do not mention the form in which the iron occurs. The geographical 
situation points, however, strongly to these being continuations of the numerous 
mao’uetic iron beds occurring to the east and north of the Kabroj en mountains 
in South Arcot, beds which themselves are unquestionably north-easterly exten¬ 
sions of some of the great magnetite beds of Salem district. Associated with 
these quartzo-ferruginous beds in the south-eastern part of the district are also 
numerous bed.s of hornblendic fen-uginous gneiss. 
These occur chiefly in the tract of country between Arcot and Wandiwash. 
Hornldeudic fernigin- To the eastward of this hornblendic band ]ie.s a broad 
OUS beds. Zone of highly granitoid quartzo-felspathie gneiss which 
extends to the boundary of the Chingleput (Madras) district; the great Wandi¬ 
wash hill belongs to this band. ^ 
In the more granitoid region north of the Pahlr hornblendic forms are much 
less common than the quartzo-felspathie forms of gneiss. 
Ferruginous beds were noted by Mr. C. H3. Oldham, chiefly near the Poiney 
river, e. (g, north of Chellempollian; south-west of Bomupilli, eight or ten miles to 
the north-north-westward; and lastly, to the north of Maimandalum, on the 
w'estern side of the Poiney river. . i i, nr m n 
Talcose beds occur only in a few places. Three were noted by Mr. Oldham, 
all of small importance. They occur at Damavajiak 
Talcose beds. (Uamarpauk), north of Arni, a little to the west of the 
road to Arcot, at a place on the left bank of the Poiney river, eight miles nortli- 
north-west of Ranipet cantonment, and lastly, a little to the south-east of Murtapilli 
and twenty miles north of the last named locality. An extremely quartzose band 
of gneiss is seen to the north-west of Sholinghur and north of Kandareddi 
(Rundaddy). 
