6

Table of Formations

Recent and Pleistocene............. Marine or estuarine clays, gravels, and sands, boulder clay,
and glacial drift

Dykes
Early Cretaceous or Late Jurassic. . = :
Coast Range intrusives

Augite porphyrite and related intrusives

ANAT Oh ooosasovaco0essae SOR ae ee Nass formation: argillites, quartzites, tuffs
Bear River formation: agglomerates, tuffs, lava flows, argil-
lites, limestones, thickness, 5,000 feet
a ee Me fee ee ee ni NPS ee eee. Fee
Jurassic and (or) Triassic........... Bitter Creek formation: argillites, quartzites, limestones,

tuffs, lava flows, thickness, 3,000 feet

BITTER CREEK FORMATION

The name Bitter Creek was proposed by McConnell for a series of
argillites in Bear River valley, and was derived from Bitter creek one of
the main tributaries of Bear river.1 The rocks of the formation are chiefly
black argillites. In most places the beds are thick and blocky, but in some
places, particularly at the headwaters of Kate Ryan creek and in the vicin-
ity of Bromley glacier, the beds are thin and consist of black argillite and
light-coloured quartzite in layers an inch or two thick. Light grey lime-
stone is present in several places, but usually as thin, discontinuous beds,
although lenses of limestone 100 feet thick are known. Tufts, breccias, and,
probably, lava flows occur at several places. The rock has been severely
sheared locally, as on Kate Ryan creek and along Bitter creek, so that it
has been changed to micaceous schist.

The upper 500 feet of the formation is calcareous and contains several
beds of limestone. The upper part also holds numerous interbeds of tuff-
aceous rocks. Tuffs also occur lower in the formation, but probably above
the middle. Banded argillite-quartzite rocks occur from the middle of the
formation downward. Most of the lower part of the formation consists of
argillite and of banded argillite and quartzite. The coarser sediments con-
tain pebbles of tuff, cherty argillite, and crystalline igneous rock.

The base of the formation is not exposed in the area and consequently
the total thickness is not known.. Because of numerous small folds the
thickness of the exposed part can not be measured accurately. On Kate
Ryan creek the formation is probably at least 3,000 feet thick and may be
considerably more.

The formation is exposed on Marmot river in two northwesterly-strik-
ing bands separated by a band of voleanic rock. The southwesterly band
is in contact with the Coast Range batholith and as the contact is not
exactly parallel to the strike of the argillite the band in some places has
been completely cut away. A small body of argillite at the contact in the
vicinity of Bayview mining property on mount Dolly is probably part of

1McConnell, R. G.: Geol. Surv., Canada, Sum. Rept. 1910, p. 63 (1911).