File:The Quarterly journal of the Geological Society of London (12893907944).jpg

Vol. 53-.
SUPERFICIAL DEPOSITS IN CTJTCH.
235
them. It will be seen that, beyond calling some of the rocks ' ? ashy '
and ' trappoid ' and speaking of ' trappean blotches,' the author
speaks of nothing but grits. It is true that in some parts they are so
much and so irregularly discoloured, apparently by infiltration, that
they then bear a superficial resemblance to some rocks of volcanic
origin, but their essentially gritty nature is unaltered.
The best exposure is on the northern slope of the hill, where the
section shown in fig. 3 is seen. Here the bulk of the hill is corn-
Fig. 3. — Infratrappean grits at Bliujia Hill.
A = Jurassic rocks.
B = Infratrappean grits.
C = Trap.
posed of the Jurassic sandstones, which on the western side rise
up and meet the capping of basalt. East of this junction there
comes in rapidly a series of thick beds of very porous character,
all of which are laminated, but not conformably to the base on
which they lie. Their porous character gives them a very ' ashy '
appearance — that is, the appearance of fine debris deposited in the
open air; but they are almost entirely composed of sand-grains
lying in a loose matrix of finer dust, and are so like some of
the samples of subreceht concrete that without labels they can
scarcely be distinguished in hand-specimens. The laminae run up
to and meet the basalt above, and as we pass eastward the deposit
becomes thinner till the basalt and Jurassic sandstones come together
again. The other patches referred to as lying in the open hollows
are generally darker and more compact, but they are still sandy.
The isolation of this and similar deposits at Khirgreea and Rhojla

its occurrence in a shelter-spot on an old Jurassic hill

its porous
character and sandy composition, all point to an seolian origin,
representing as they do the same conditions as those represented by
the subrecent concrete.
The second type of deposit at Sanosra, due south of Bhuj, and
at Artara, between the Jurassic rocks and the trap, is simply a
collection of stones derived from the rocks below, cemented by finer
material, and lying in hollows over which the trap passes

that is
to say, it is the surface-debris of the land on which the lava was
poured out.