Predominance
of limestone.

Cretaceous
sandstone.

Fossiliferous
limestone.

Triassic beds.

Fault.

32 ¢ FINLAY AND OMENICA RIVERS.

The rocks exposed along the pass consist principally of grayish
Paleozoic limestones striking in a north-westerly direction, and dipping
persistently to the south-west. Repetitions of parts of the limestone
series, caused by overthrust faults, occur at several points. No infolds
of Cretaceous or Laramie strata, such as occur in Alberta, exist, and to
this fact is due the greater irregularity of the subordinate ranges.

Immediately east of the main range, exposures of yellowish-weather-
ing calcareous sandstone, probably of Cretaceous age, occur in the banks
of the river. These are replaced, going westward, by grayish limestones
dipping steeply to the west. The junction between the limestone and
sandstone is concealed in the valley, but there is little doubt, from the
relative position of the two formations, that the contact is a faulted one
and that the Paleozoic limestones of the mountains, here as elsewhere
along the eastern boundary of the range, are thrust up over the Meso-
zoic rocks of the foot-hills.

The limestones are fossiliferous, the fauna, so far as ascertained, being
similar to the Banff or Devono-Carboniferous division of the Bow
River section.

West of the fault, the limestones stand at a steep angle, the beds
being fairly regular, but further west they become greatly confused
and show evidence of much disturbance. In the second range, the
limestones are overlain by a band of dark Jonotis-bearing calcareous.
shales and impure limestones of Triassic age. West of the Triassic
band, a second fault brings the Banff limestones again to the surface,
and the same limestones, probably repeated by faults, occur in the next
two ranges. In the first of these, the Banff limestones and overlying
Triassic beds have a regular westerly dip, but in the second, a line of
strong disturbance is reached, and the strata as seen on the mountain
sides are crushed into numerous subordinate folds.

A fault of considerable magnitude crosses the valley west of the two.
ridges referred to above, and brings up limestones which were referred
to the Castle Mountain group. West of this fault, the dips north of the
river for some distance were too confused to follow, but south of the
river, the beds, with the exception of one double fold, dip regularly
westward until near Mount Selwyn. The limestones in this part of
the range are mostly unfossiliferous and of the Castle Mountain type,
but higher beds holding Halysites were found in one place.

Mount Selwyn shows a sharp anticline on its eastern slope. The
centre of the mountain is formed of almost vertical limestone beds, but
going westward these are soon replaced by the quartzites, schists and
crushed conglomerates of the Bow River series. The latter are forced

—s