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176
PROCEEDINGS OF THE GEOLOGICAL SOCIETY. .DeC. 13,
conglomerate is here intercalated in the talc schists and dips with
them. A little above or N. of Petit Coeur a momitain rill descending
from N.E. to S.W., waters the highly inclined faces of these talc
schists, or rather occupies a deep gorge in them, to the east of which
these same beds are seen to graduate up into and to be surmounted
by others which contain belemnites and plants, the whole in perfectly
conformable apposition and at angles from 70° to 75°, as expressed
N.W.
Fig. 2.
Petit-coeur.
S.E.
Talc schist.
1. Talc schist with sandstone.
2. Black slates (Belemnites).
3. Talc schists with anthracite.
12 3 4 5 Jurassic rocks.
4. Grits, sandstone, &c.
5. Jurassic schists, &c.
tt Coarse detritus and blocks.
in the woodcut (fig. 2). The upper portion of the inferior or cry-
stalline strata is a light-coloured talc schist used in the mountains
for the covering of cottages. It is called *' ardoise blanche" by the
quarrymen, and forms the floor of the quarry (1). Immediately
upon this, and perfectly parallel to it, lies another stratum (2) of fissile
calcareous flagstone of dark indigo colour, called " ardoise noire," in
which the belemnites occur. I could detect no slaty cleavage in these
beds, whilst both the shining or talcose, and the dull black or calca-
reous flagstones strike N.N.E. and dip together 70° to 75° E.S.E.
They are further connected by certain bands of hard sandstone oc-
casionally coarse and gritty, with which the dark flags alternate to-
wards their base. In the lower quarry (there being several openings
in the line of strike in order to procure the black calcareous flagstone),
these belemnitic beds are seen to be surmounted by another band of
talc schist (3), as conformable to the belemnite flags or slates (2) as
the latter are to the inferior talc schist (I). The uppermost of the
three beds is that in which a certain portion of anthracite has been
detected, the exploration of which has led to the discovery of numerous
plants. These plants chiefly lie in the floor of the anthracitic schist,
and therefore within a few feet of the belemnite flags (2), and they
are strikingly distinguished by the brilliant white relief of the frame-
work of the vegetables due to the dissemination of the talc upon the
dark ground of the schist or flagstone. Much pyrites in single cry-
stals and bunches occurs throughout the rock.
This carbonaceous schist with plants, several yards thick, is sur-
mounted by strong beds of dark grey hard grit that weathers to a
rusty colour, and which alternates several times with dark-coloured
schists. And here it is to be observed, that the sandstone (4) above
the coal plants is not to be distinguished from the band beneath the
belemnite flagstone; or in other words, hoth the belemnite and the
plant beds form parts of the same geological mass, the upper and