17G 
Records of lie Geological Survey of India. 
[VOL. X, 
find that they are brought up by another contortion, as is represented by the dotted lines. A 
short distance further up the bed of the river we come upon vertical beds of red shales (a), 
which, if not related as represented, would be younger than the quartzites (J), a view untenable 
from the relations found to exist between them elsewhere. That the quartzites (6) are bounded 
by an external fault is most probable. Unfortunately, no contact with the metamorphics is 
seen, there being no outcrops in the bed of the river for several miles to the east. Both here 
and all along the boundary of the plateau area from hence southwards to within a short 
distance of the Udet, the disturbance and constantly varying character of the beds could 
scarcely be explained by mere lateral crushing. To tho north it is possible that a ridge 
of fault-rock in the metamorphics at Tarnot may mark tho continuation of the line of 
fracture. Regarding the second fault represented, the shortness of the interval between 
the quartzites (J) and the shales (a) argues, I think, against the possibility of the whole 
of the former being brought up by a contortion, and therefore it seems probable that the 
lower members are cut off by a fault, and that the red shales (a), as represented, have been 
thrust into vertical contact with the quartzites of the central part of the sequence. 
Passing the red shales (a) we como upon a wall-like ridge of pseudomorphic quartz (fault- 
rock) (q) which strikes to about 20° east of north, 20° west of south. Beyond it there arc 
thin-bedded quartzites, shales (c), and a black carbonaceous sandy layer (d) dipping to from 
5° to 10° to west and west-north-west. Overlying these conformably are the saccharine 
and vitreous quartzites, &c., which form the main mass of the plateau. That this run 
of fault-rock marks a lino of disturbance thero can, I think, be little doubt, the more 
particularly as the thin quartzites ( c ) and shaly beds associated with the carbonaceous 
layer appear to represent a portion of the contorted beds (i) of the outer range. Further, 
with reference to both this and the previously mentioned fault, evidences of a pair of diverging 
faults are found for many miles amongst the crushed and disturbed beds in the internal 
valley to the south. They are also indicated by lines of a breccia abounding with brown 
hematite,* and on one of them is situated a Hot spring near Kotagarh. Taken alone, 
this section, due allowance being made for marginal crushing and fractures, would not be 
sufficient to prove original unconformity between the beds c, d, e, and the red shales (a ); but 
it must be remembered that in other localities where the lower beds are seen in a very 
disturbed condition close to the base of horizontal quartzites, similar explanation of the 
relations of the beds by pairs of faults cannot bo given. 
In the Udet River from Boidelpur westwards there is a section of the lower shales. 
The first beds seen are red and grey shales, with one bed of quartzite resting on them 
and dipping at, apparently under, granitic gneiss at an angle of 45°. In the northern 
bank of the river the granite, for about a foot, seems actually to overhang the bed of 
quartzite. This appearance may be due either to original deposition under an over¬ 
hanging ledge or to the effects of a horizontal thrust from the west, probably the latter, 
as the bounding fault can scarcely have died out again before reaching this point. 
Elsewhere I have noted cases of similar beds dipping at the boundary. The river 
between Boidelpur and Tonkulmal exhibits a nearly continuous section of grey, red, and black 
shales, with, in places, much infiltrated iron. Besides the above-mentioned bed, no quartzites 
appear in the bed of the river. The dips are for tho most part low to east, east- 
south-east, south-east. In the hilly country to the south there are quartzites which, at 
the boundary between Koirpodor and Pliulchi, locally dip 80' ) to east and south-east. 
Elsewhere they flatten and become horizontal. It seems scarcely probable that they rest 
conformably on the red and grey shales, hut no actual junctions wore found. 
Finally, it has been established that these shales are older than the quartzites; that they 
are clearly overlapped is apparent from the sections on the west, in which they do not appear. 
* Near Bandi, Kootagarh, and Kudapani respectively. 
