The most complete sections studied occur in the vicinity of
the Summite Although both top and bottom of the seetion were observed,
the intervening structure has not been worked out and the thié¢kmess
can only be estimated. Also the boundary between Silurian and Devonian
members of the series has n@t been determined.

As seen on the west side of Muncho [ake, about 50 feet of
limy shale marked with worm burrows forms the. lowest member of the
limestone series and is diroctly overlain by typical coral-reef limestone.
The exact contact between the shale and underlying sandstone was not
seen, but the strike and dip of the two veried, suggesting an unconformity,
&s occurs elsewhere.

The lowest limestone member of the series appears to be
everywhere of coral-rcef origin, and this condition” continues or is
repeated for hundreds of feet upwards, even above “Heavy. sandstone members
of the formation. The corals are typical of mid-Silurian seas. The
middle beds of the series consist of light grey limestone that appears
to be entirely unfossiliferous. The upper beds consist of groy limestone
including coral reefs of Middle Devonian age.

Near the Summit, a composite section may be described as
follows. At MacDonald Creek blue limestone is interbedded with quartzite
beds up to 10 fect thick and overlies brovm weathering, fine-grained
quartzite. A 50-foot coral reef occurs in the lower limestone and
contains highly silicified corals, among which may be recognized
Halysites catenulatus and Eridophyllum rugosum abi . The bedding here

is vertical and the rocks are highly silicified

To the eastward, in the wall of a oirgue, coralline limestone
unconformably overlies folded, brown weathering Precambrian quartzite.
The irregular bevelled contact may be seen clearly in the north wall of
_ the cirque. :

A thick limestone section may be studied in Mount ‘st. Paul and
adjacent mountains to the west. The lower beds are generally folded and
overthrust, but the higher beds have gentle dips. Sandstone beds occur
at different elevations. They vary from a few fect to 70 feet in
thickness and grade into the limestone at top and bottom. In places the
contact is faulted, the sandstone being the more competent bed and
overriding the limestone. Middle Silurian corals occur above and below
the sandstone. ‘The peak of ‘Mount St. Paul seemed unfossiliferous. The.
maximum height of these mountains above Summit Lake is about 2,600 feet,
giving &@ minimum thickness for the formation. Neither top nor bottom
of the section is seen at this Locality, :

ies The top of the limestone See wot exposed in the bed
of a small mountain creek that crosses the Highway from the north near
mile 109, or 6 miles west of the Simmit.

About 200 to 300 feet below the top, the limestone is thin-
bedded and mud-cracked into irregular polygons 9 to 18 inches on the
Sides, The upper limestone is dark: grey and. includes coral reefs from —
which the following fossils were obtained: Favosites ba saltica Goldfuss(?)
and another colonial coral, Conocardium(? ni Fenestelia(?), Bactrites(?),
Atrypa cf. spinosé Hall, poncho reali), Proetus sp«,.and Conolichas(?).
This fauna, dependent as it is upon poorly prese ‘ved fossils, neverthéless
is varied in spéties and has Middle Devoniin characters. In a general
way it suggests Middle Devonian faunas of Mackenzie River.

The limestone is overlain by a thick series of thin=bedded,
black shales, carrying hard limy beds 2 few feet above the contact.
. These shales appear to be conformable upon the limestone, but are