PART 4 .] 
Ball: Mahanadi basin and its vicinity. 
179 
On the south-east boundary only did Mr. Medlicott meet with a “ distinct case of simple 
unaltered superposition.” Close to the east of Arang, the shaly, flaggy, dark, silicious 
limestone shows with a steady inclination of 3° to 4° westward, and on the rising ground to 
eastwards, the strong-bedded sandstones pass up from beneath the limestone and shales to 
form a low range of hills. These hills present a gentle slope to the west, and are scarped 
along the eastern face, in which the junction can be admirably seen of the massive sandstone 
resting on coarse granitoid gneiss and largely made up of its debris. This debris is not “ coarse 
and water-worn, but gravelly and still undccomposed.” Further south in the Pairi River 
section, I met with the continuation of this margiual bed of sandstones, but I saw no clear 
indication there that they passed under the limestones. Indeed, from the absence of any 
distinct dip of the sandstones and the lower level at which the limestones occur, it seemed 
to me possible that these sandstones might be the marginal remnant of an overlapping bed; 
but there was, it must be admitted, an interval quite sufficient between the localities where 
these rocks were respectively exhibited to permit of the sandstones dipping below. Mr. 
Medlicott has generalised his observations in reference to this and other sections in the 
following words: “ The topmost strata are almost confined to the low grounds where they 
show the minimum of disturbance, while the bottom hands rise along the boundary and are 
often much modified by contortion and compression. One has to seek far and wide for proof 
of the two being really continuous.” 
The sections on the western boundary present a general resemblance to those of the 
northern, but the thickness of shales exposed there is greater, and the general character is 
of course much modified by the presence of overlying basalt. At Warraband, on the Raipur 
and Nagpur road, the Vindhyans are separated from the crystalline rocks by a bifurcating 
ridge of quartz, the branches of which strike to north 10° east and north 30° east; the latter 
possibly marks the position of a fault. East of it are rocks identified by Mr. Blanford 
{MS.) with the Yindhyan sandstones of the Godavari area—“They are hard purplish 
grits and appear to dip to the eastward at an angle of 10°, but this is far from clear. 
They continue for a mile or more, apparently with the same inclination, but they are by 
no means well exposed, and a little beyond (east of) Warraband all the rocks become 
concealed by soil.” “Limestones are exposed in the Mula River, about six miles beyond 
(east of) Warraband. They are unmistakably identical with the Pem limestones, and they 
dip at a low angle to east-north-east. A mile further the red Pem shales are seen nearly 
horizontal, and they continue as far as Nandgaon.” 
With regard to the general section of lower Yindhyans in Chhattisgarh, Mr. Blanford has 
written : “ Apparently the section of the lower Vindhyans of Chhattisgarh closely resembles 
that in the Pem Gunga valley. Massive sandstone at the base, then limestone, above shale, 
upon this apparently rest alternations of thinly-bedded sandstone and limestone. It should, 
however, be remembered that the rocks are only seen in the Chhattisgarh plains at distant 
intervals, and that but a very imperfect notion of the section can be obtained without far 
more careful examination than it has hitherto been possible to give to the ground. Still 
the general section east of Raipur so exactly represent that to the west that the main 
sequence, agreeing as it does with that in the Pem Gunga valley, may fairly be considered 
as correctly ascertained.” 
Could it be shown that these quartzite sandstones are in the Chhattisgarh area 
representative of the great thickness of beds in Karial and Nowagarh, then the latter would 
have in all probability to be regarded as younger than the limestones ; but I have already 
shown that these indubitably rest upon shales—possibly unconformably—whose lithological 
resemblance more particularly to the Talchir-like shales described by Mr. Medlicott is still 
stronger than is that to be found between the quartzite sandstones of the two areas. 
