PAB.T 4.] 
Ball: Mahanadi basin and its vicinity. 
169 
Alluvium. 
Under this heading there is little to be said at present. In the published accounts 
of the coastal districts there will be found some remarks on the subject. In the higher 
parts of the Mahanadi valley up to the Raipur district, so far as they are known, there 
are no deposits of alluvium of sufficient extent to constitute alluvial plains as the term 
is ordinarily understood. Patches of true alluvium of limited extent do occur in the vicinity 
of the river, and in the Raipur district, which I have not examined; there may possibly 
he deposits meriting special notice, but in the rocky districts of Sambalpur and Orissa, 
the alluvium is much mixed with local rock-debris and laterite. In the valley of the Tel, 
where it traverses Patna and Kalaliandi, there is a kunkur-bearing alluvium, sometimes of 
wide extent, and which attains an importance from the fact of its concealing the rocks. On 
the Jaipur-Bustar plateau, in the river valleys between the laterite, the alluvium is some¬ 
times of considerable thickness, if not of wide extent. Thus the Iudravati sometimes 
affords sections of 20 feet of a reddish sandy alluvium with no rock appearing beneath. 
Latekite. 
Regarding the coastal laterite I only add, to what has already been published on the 
subject, that in the cuttings through some ridges of laterite on the Khurda road I recently 
found numerous lenticular masses of dense shaly iron ores which seemed to explain the source 
from whence considerable accumulations of fragments of similar shale, which I had previously 
met with, but had hesitated to identify with laterite, had been derived. 
The occurrence of laterite in the vicinity and on the rocks of the Raigarh and Hingir 
coal-field has already been described by me. At that time I had met with no example of high- 
level laterite in Sambalpur, but during the past season I found several remarkable deposits at 
high elevations both in that district and others further south. Theso all occurring in a 
country into which there is no evidence of the Deccan trap ever having extended seem to be 
worthy of special description and notice. 
The Gandamardan range on the borders of Patna and Borosambar which rises 2,000 feet 
above the general level of the country, both from its altitude and its flat plateau top, presents 
a striking appearance when seen from a few miles distance. At first it seemed probable that 
the structure might be due to flat-capping beds of Yindhyan quartzite, but on examination 
it was fouud that the range consisted of steeply inclined garnetiferous and ferruginous 
gneiss, with a cap of about 100 feet of laterite. The summit is a flat plain with sparse 
vegetation very similar in many respects to the Main-pat in Sirguja. 
On the Karial-Nowagarh plateau which, as is above stated, averages 2,500 feet in 
elevation, I found some scattered thin patches of laterite, possibly the remnants of a once 
continuous bed of which, in parts nnvisited by me, there may still, perhaps, be better pre¬ 
served examples. The massive Chaoria hill on the borders of Ivarial and Kalaliandi is not 
improbably capped with laterite, judging from its flattened appearance as seen from a 
distance. 
In the south-eastern parts of Kalaliandi there are a number of pais from 3,000 to 4,000 
feet high ; of these I was only able to ascend one, Baplaimali, seven miles east of Moulpatna. 
Its elevation above the sea, according to the Altas Sheet, is 3,587 feet, of which the upper 
300 feet is formed of a bed of laterite resting on the up-turned edges of metamorphics. 
From Baplaimali a good view of a number of other pats is obtained (particularly of Sijimali 
4,058 feet). All owe their plateau form to similar laterite caps, which in all probability 
formed, at one time, a continuous bed throughout a wide area. 
