File:The Quarterly journal of the Geological Society of London (12511800315).jpg

1853..
BIGSBY — GEOLOGY OF aUEBEC.
89
argillaceous and quartzose, loses nearly all its fossils, and assumes
a soft shaly structure, with a high dip to the S.E., — the same which
prevails for more than 100 miles in every direction but due north.
Looking up, from below, at the higher parts of this bowl-shaped
chasm on the east side, we see, peeping from beneath rubbish and
among shrubbery, displaced slabs of compact Trenton limestone, fol-
lowed downwards by dark shales, while the lower parts of the preci-
pice and the beach of the River St. Lawrence are wholly occupied by
Utica slate in the full development of its crumbling rusty brown
shales, its Graptolites and Triarthrus Beckii, the Trenton fossils
having disappeared.
Beauport. — Continuing our observations both on the Trenton lime-
stone and its connexion with Utica slate, it is to be noted that at Beau-
port, the village a little westward of Montmorenci, the change is well
displayed.
Two hundred yards north of Col. de Salaberry's house in this
village, we have in a quarry the genuine horizontal Trenton limestone.
At oxAj ffty yards north of the house,' it is interstratified largely
with black shale, and with a slight dip. In the streamlet close to
the house, the rock is the true Utica slate dipping at a high angle
to the S.E. (Capt. Skene, R.E.).
In the quarries about this village the Trenton limestone is full of
shale, often coated with fluor-spar, copper pyrites, and calcedony.
The bituminous druses are numerous, and often of the size of a
walnut. Its fossils are scattered in patches ; sometimes they are
altogether absent, at others in inconceivable quantities. Some of
the shaly layers are wholly composed of Trilobites (especially of the
Asaphus gigas), or oi Rhynchonella hemiplicata.
Fig. 3. — Section at Petite Ruisseau R., showing the relation of the
Utica slate to the Trenton limestone.
Trenton limestone.
Talus, &c.