70 
Records of Ike Geological Surrey of India. 
[VOL. I. 
by denudation, and it is interesting to observe its very apparent relation to the distribution 
of the rocks. The river Mhye with its tributaries is the first of the streams flowing north¬ 
ward from the south edge of the plateau which has not to encounter the resistance of the 
horizontal Vindhyan strata; beneath the trap it only encounters the decomposable and 
variable rocks of the metamorphic series, and erosion has gone on unchecked. After a 
northernly course of many miles the Mhye bends westwards and southward into the 
gulph of Cambay. 
The greater part of the plateau of Malwa is formed entirely by the great Deccan trap 
formation. In going northward along the table land from Indore through Rut]am, the 
Vindhyans first appear at Mundesor, about 140 miles from the Nerbudda; they gradually 
emerge from beneath the great expanse of trap to the east. In following a parallel course 
a little to the west, along the boundary of the table land, it is seen that the non-appearance 
of the Vifidhyans to the south is not owing to their being concealed by the trap; for all 
along the boundary the crystalline rocks immediately underlie the volcanic rock ; and an 
examination of the Vindhyans themselves shows that their boundary at Mundesor is a feature 
of very ancient date. It runs in a north-west by west line from Mundesor, and the 
Vindhyans rise into small plateaus in that direction, the strata being quite horizontal. Even 
on the high level signs of disturbance are traceable along the line of contact, but it is where 
the strata run out along this strike into the low ground that tho structure is fully seen. 
Here the lower groups of the upper Vindhyans crop out with a rapidly increasing north¬ 
easterly underlie against the crystalline rocks ; the lowest hand being a cong'lomeritic sand¬ 
stone. In the opposite direction the boundary at Mundesor strikes towards II oshungabad 
and Burwai, the lowest point to which the Vindhyans reach in the Nerbudda valley. 
About the point where the Mundesor line of boundary strikes the edge of the plateau, 
the boundary makes a sudden bend of half a right angle, running due north for 40 miles, 
passing about 20 miles west of Necmuch. This is the most westernly position of the 
Vindhyan boundary. With it there commences an immediate change in the character of 
the contact: the margin of disturbed rocks is several miles wide, marked by flat, symmetrical, 
anticlinal flexures, causing ridges along the outcrop of the sandstones with intervening 
valleys on tho contorted shales. 
These features are well seen where the Neemueli and Oodipoor road crosses. The 
actual line of junction is marked by no special feature, the contact taking place on the low 
ground with the Vindhyan shales, which seem to he about equally liable to erosion as the 
gneissose series. It seemed to me that the shales at the contact were those with which 
the limestone is associated and which I have considered to be of the Bundair group. There 
would thus he presumption in favor of a fault. 
Close to Chittorgurh there is another abrupt, bend in the direction of the boundary; 
from north and south it turns to the north-east. Ror some distance at least, in this new 
direction, the character of the junction is the same as that last described ; the IN usserabad 
road north of Cliittor crosses at the same level from the crushed Vindhyan shales, with 
limestone, on to the friable granitic rocks. The strike of the contortions in the shales has 
already become identical with the new direction of the boundary. The actual contact often 
runs in a slight depression of the surface, there being no vein-stone visible or any direct 
evidence for the supposed fault. Where I next examined this boundary near Parsol i, some 
15 miles north-east of Cliittor, although its strike and that of the strata, continue steadily 
to north-east, the conditions of the junction have entirely changed, having again assumed 
the form noticed in the Mundesor reach. Prom the north-west one approaches upon 
granitic and schistose rocks up to the very base of a steep ridge ol' sandstone in which the 
dip is south-easterly. Beyond this ridge there is a steady longitudinal valley upon crushed 
shales, without limestone; then again another ridge of sandstone with the same south¬ 
easterly dip; just insido this ridge the village of Parsol i stands in an irregular open valley 
formed of the shales and limestones, the plateau-hills to the south-east being formed of 
the sandstone overlying the same. This is the moat compact section I observed of the 
three groups of the upper Vindhyans. 
At about 4 miles tonorth-east of Parsoli the regularity of the section terminates in the 
most obscure manner, involving a fresh change in tho direction of the boundary and in the 
strike of the rocks. At Bumunia and Singoli the sandstone ridges come to a sudden 
termination along an east-west line, facing' a low wide-spreading plain. The feature is 
