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COAL.
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the groups successively in ascending order, the lowest is the
Talchir Group.—The
rocks composing this group consist of sandstones, fine shaly silts, and
boulder beds, all of which are commonly of greenish or buff colours.
The maximum thickness is 800 to 1,000 feet, but in many of the fields
it does not amount to more than about one-fourth of that amount. These
rocks are found at the base of all the coal fields, and also in many
outlying tracts where they are not in contact with newer deposits. Of
especial and general interest to geologists is one variety of boulder
bed, as it affords evidence of the existence of floating ice at the
time of its deposit in latitudes running as low as 160 30' N.
It
is of importance, however, to reiterate the fact, that in these rocks
we find the first traces of life in India, the vast thicknesses of rock
deposited in previous periods being, so far as we know, azoic. These
first forms consist chiefly of equisetaceous plants and ferns—all of
them, I believe, such as might have existed in a moderate temperate
climate.
The
area through which, often at widely separated intervals, exposures of
these beds are scattered, may be roughly indicated by saying that it
occupies the higher central parts of the Peninsula, being bounded by
the 770 and 88° of east longitude, and the 16° 30' and 25° parallels of north latitude.
The
Talchir beds are of no economic importance, save that they contain
several varieties of easily worked, durable, and sometimes ornamental
building stones. Limestones are rarely found ; generally they occur
merely as concretionary masses in other rocks. From their scattered
distribution and limited extent they can scarcely be expected ever to
prove of much value.
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