Figure 37. Superimposed folds in amphibolite within
the Ramos succession of the Snowshoe Group in a log-
ging clear cut south of Little Swift River near its junc-
tion with Swift River. (GSC 191030)

near Swift River. The oriented amphibole and the lamel-
lae of mineral segregations define the rock foliation.
Chlorite occurs as sheaths and mats rather than as
oriented crystals.

Contacts of the amphibolite with bounding quartzite
and schist are sharp. Locally the amphibolite contains
thin interbeds of light grey medium grained quartzite and
schist. Minimum thicknesses of the amphibolite are in the
order of 1 to 10 m; variations and total extent of the
amphibolite horizons are unknown.

Several impure marble units occur south of the
Fontaine Creek area. The marbles are dark grey, weather
buff and light grey, and are composed of calcite with
impurities of micas and quartz. They are interlayered with
grey and silvery schist or phyllite and are in sharp con-
tact with olive micaceous quartzite and phyllite. Individ-
ually they are discontinuous and less than 50 m thick.

Chlorite phyllite along Ramos Creek, and in scattered
exposures south to Swift River is interpreted as metamor-
phosed tuff. In the section along Ramos Creek the tuff
occurs near the top and consists of 1 to 2 m thick beds
in black and olive phyllite and fine grained quartzite.
Along Keithley Creek tuff is interlayered with dark grey
and olive phyllite near the upper contact of the Ramos
with the Harveys Ridge succession.

Other minor rock types included in the Ramos suc-
cession are rhyolitic tuff near Sovereign Mountain, and
micaceous quartzite with coarse grained détrital musco-
vite found near Eskeridge and Weaver creeks.

Because the quartzite-pelite sequences of the Ramos
succession have similar sedimentary characteristics to
those of the Tregillus rocks they are thought to have been
deposited in a similar environment under similar condi-
tions and possibly from the same source terrain. Differ-
ent from the Tregillus, however, is the occurrence of
amphibolite, marble, black siltite and tuff. The tuff of

52

the Ramos indicates volcanic activity, which is absent
from the Tregillus except possibly where it is in contact
with the Kee Khan marble. The association of marble with
some of the amphibolite suggests that the amphibolite
may be derived from impure carbonate. Quartzite-pebble
conglomerate in the Ramos near the settlement of
Keithley Creek is similar to that of the Tregillus.

The age of the Ramos succession is assumed to be
Hadrynian, coeval with the similar Tregillus succession
(whose age also is unknown) which may be its lateral
equivalent. As such, it may also correlate with the
Horsethief Creek Group of the Selkirk Mountains.

Tregillus clastics

The Tregillus clastics are a sequence of micaceous quartz-
ite, phyllite, schist and orthoquartzite with a quartzite
clast conglomerate near its top. The conglomerate and
contact relations with the overlying Kee Khan marble are
the only distinguishing features. The interbedded quartz-
ite and pelite are much like those of the Ramos, Eagles-
nest and Tom successions.

Tregillus clastics underlie an area in the northwest
corner of the Wells map area (Map 1635A, in pocket);
mainly north of Highway 26 and west of Willow River.
They were previously mapped as Kaza Group (Snowshoe
Formation; Campbell et al., 1973) and are continuous
with some of the rocks mapped as undifferentiated Cari-
boo Group in Prince George map area (Tipper, 1961).
They may be wholly or partly equivalent to the Ramos
succession. Metamorphism in the unit varies laterally near
the garnet isograd. Retrogressive metamorphism is com-
mon throughout the sequence. The minimum thickness
is approximately 400 m.

The base of the Tregillus rocks is not exposed. The
sharp, conformable upper contact with the Kee Khan
marble is placed at the first calcareous rocks above the
quartzite conglomerate.

The Tregillus consists of interbedded quartzite, peli-
tic rock and minor conglomerate. The quartzite weathers
grey and brown, and is grey and light grey on fresh sur-
faces. It is mostly medium- to coarse-grained and poorly
sorted with variable amounts of matrix mica. Quartzite
with little to no matrix mica is lighter grey than other
varieties. Quartz clasts are mostly glassy clear and a few
are blue. Potassium and plagioclase feldspar are present
locally up to 10%. Accessory minerals include zircon and
rare rutile. Metamorphic muscovite, chlorite and biotite
occur up to 30%, with the muscovite defining the rock
foliation which is generally overgrown by biotite and
chlorite. Metamorphic garnet and tourmaline occur
locally. The pelite interbedded with the quartzite varies
from dark grey to grey and olive grey. It consists mainly
of fine white micas and quartz. Metamorphic biotite and
garnet are common near Tregillus and Aura Fina creeks.

Bedding is even and rhythmical with quartzite beds
averaging 40 cm in thickness and pelite beds generally
thinner. Contacts between quartzite and pelite are sharp.