PART 2.] 
Medliuott: Coal in the Caro Hills. 
61 
The chances of this prospect are briefly as follows : It is demonstrable in the Khasia hills 
and here, that the portions of the cretaceous rocks found on the gneiss or within its southern 
limit are only the marginal deposits of a formation expanding greatly in thickness to the 
south. Even within that marginal area, coal seems to have been formed only in local depres¬ 
sions of the old land-surface. The important question then occurs—how was it in the main 
depression of deposition ? For the Khasia portion it can positively be said that the con¬ 
ditions for the accumulation of vegetable remains did not exist to the deep of the formation. 
The whole expanded series is fully exposed in a nearly vertical position at the base of the 
range; and marine fossils occur throughout. Even the horizon of the coal near the base of 
the series can sometimes be determined here by the presence of plant-markings and fragments 
of the resinous substance so common in this cretaceous coal, but here mixed with marine shells. 
The change to the westwards has not been traced out continuously along the strike ; but at the 
Sumesari it is already very marked: there is a strong seam of coal, well up from the 
bottom beds ; it is brought up twice by contortion of the strata, showing its extension to, 
some distance from the rise ; and no marine fossils have been detected in the associated beds. 
This, it will be recollected, is close on the same meridian as the Daranggiri field, only to the 
south of the main range. To the west of the Sumesari a very great change takes place 
in the mechanical circumstances of the strata: instead of being thrown on eud at their 
junction with the gneiss, as is the case everywhere to the east, the boundary here is, what is 
called, overlapping—the strata being banked against the flanks of the mountain, each suc¬ 
ceeding layer overlaps and conceals the one below it. There has been here too some eleva¬ 
tion, compression, and waving of the strata ; but, on the whole, the formation is only exposed 
to the depth to which the local streams have cut through the superposed strata. All this 
is admirably exposed in the ravines below Turn; each layer being for the short space of its 
overlap the local bottom layer of the formation. In some of them sticks and strings of 
coal occur, as under Machakholgiri; hut it seems likely that none of these streams touch the 
true horizon of the coal deposit; so that this may be in full force to the deep of the basin. 
In none of the beds of this region have any marine fossils been detected ; and there is very 
abundantly here a white fine clay-rock* that hardly appears in the Khasia sections. On the 
whole, I think the question of coal or no coal in this position ought to be set at rest by a 
trial boring. I have recommended Dipkai, about two miles to north-east of Putimari Haut, 
as a suitable spot. 
Geolog v.— I would add a few remarks of a more general nature to bring my recent 
observations into connexion with what I have previously said on the geology of this 
region (see Mem. Geol. Sur., India, Vol. vii, p, 151). The difference of the structural fea¬ 
tures of the sections in the Khasia and the Garo divisions of this continued mountain-mass is 
greater than was then surmised. In the Shillong region, the elevation of the plateau took 
the form of an equable rise of the whole area—the gentle slope of the cretaceous strata 
from the edge of the scarp, passing into perfect horizontality as they extend northwards, 
is perfectly unbroken. In the features then observed along the outer base of the range, 
there was nothing to suggest its being otherwise in the Garo region; a gradual dimi¬ 
nution of the elevatory and contorting action being the only change apparent. It would 
seem, however, that, besides a general decrease in vertical effect, the elevating action here 
was almost confined to the axis of the range, corresponding with the line of the scarp to the 
* This rock may yet be found valuable as a pottery-clay. It contains 52’8 per cent, decomposable by sulphuric 
acid, and free from alkali iron and lime, -with a residue of 47’2 per cent, of pure fine silica. 
