Stratified rocks
Snowshoe Group
Ramos succession

The Ramos succession is mainly interbedded micaceous
quartzite and phyllite with subordinate siltite, amphibo-
lite, marble and tuff. Very coarse grained, very micaceous
olive quartzite is characteristic of this unit of the Snow-
shoe Group. Tuff and siltite appear high in the section
whereas marble and amphibolite are mainly low. The
Ramos is diverse because the subordinate rock types are
discontinuous and poorly exposed. The succession is
intensely sheared at its contact with the western Crooked
Amphibolite of the Slide Mountain Terrane. The Ramos
may be in whole, or in part, related to the Tregillus.

The Ramos succession underlies the western border
of the map area from Ramos Creek southeast to Keithley
Creek. The most varied assemblage occurs near Cariboo
Mountain. Ramos rocks were previously included in the
Snowshoe Formation by Campbell (1963), Campbell et
al. (1973) and Campbell (1978). There is no designated
type section for this succession, however, exposures in
road cuts along Ramos Creek, on Sovereign and Cari-
boo mountains and in Keithley Creek are representive of
much of the upper part of the unit. The lower sections
are only poorly exposed in the low lying areas near
Fontaine Creek, and Little Swift and Swift rivers. The
total thickness of the unit is unknown, but it exceeds
300 m.

The base of the Ramos succession is not exposed.
Contacts with other units are suspected to be faults except
along Keithley Creek where it may stratigraphically
underlie or interfinger with the Keithley succession.

Interbedded quartzite and phyllite are the most abun-
dant rocks within the Ramos succession (Fig. 36). The
quartzite is olive to grey on fresh surfaces, weathering
grey to olive grey, is poorly sorted, and on average is
medium to coarse grained. Almost everywhere it is mica-
ceous with the notable exception of a sequence on Sover-
eign Mountain. Quartz clasts are glassy clear, grey and
minor blue. In thin section the quartz grains are polycrys-
talline, commonly with 3 or more crystals per grain, but
the coarser the grain, the fewer the crystals. Many grains
have microcrystalline tails or a concentration of small
crystals on their edges. The tails parallel the foliation of
the muscovite matrix. All but the finest recrystallized
quartz has undulatory extinction. Potassium and plagio-
clase feldspar content varies greatly from place to place
but is everywhere less than 10%; averaging approximate-
ly 3%. The potassium feldspar, the predominant feldspar,
is microcline and orthoclase. Beaded perthite comprises
about half of the orthoclase. The plagioclase is oligoclase
or andesine; varying from An); to An3;. The feldspars
are partly altered (1-90%) to sericite, epidote and calcite.
Zircon is the primary accessory mineral. Metamorphic
muscovite, chlorite and biotite occur up to 45% defining
several overlapping metamorphic foliations. Metamor-
phic garnet, ankerite, siderite, calcite, pyrite and tour-
maline occur locally.

Figure 36. Isoclinally folded fine grained micaceous
quartzite of the Ramos succession of the Snowshoe
Group on the logging road northwest of Keithley Creek
(Canadian quarter for scale). (GSC 191029)

The phyllite is olive with lesser amounts of grey. Near
Cariboo Mountain equivalent rocks are olive-grey schist.
The phyllite consists of fine grained quartz, white mica,
chlorite and accessory pyrite, ankerite, siderite and epi-
dote. The quartz is in trains of less than 0.2 mm sutured
crystals that follow the foliation of the rock. Albite is
in some places intergrown with the quartz. The white mica
is commonly crenulated and overgrown by 0.5 mm mus-
covite and chlorite. The schist found along the Swift River
and on Cariboo Mountain is characterized by 0.2 to
0.5 mm muscovite, chlorite and biotite overgrowing the
sericite foliation and which are in turn deformed. Garnet
is a common accessory mineral in the schist.

Contacts between the quartzite and pelite are sharp
and bedding is generally rhythmical. As with the Tregil-
lus, areas of non-micaceous quartzite form thick massive
sequences devoid of pelite. Graded bedding occurs
locally, most commonly as the decrease of the grain size
of all fractions but in some places as a decrease of grain
size in only the coarse outsize fraction; rare occurrences
of channel scour were noted.

Black siltite and very fine grained quartzite inter-
bedded with black phyllite are scattered throughout parts
of the belt of Ramos rocks. They are similar to rocks of
the Harveys Ridge succession.

Amphibolite and associated marble and calcareous
amphibolite are common in the area of Cariboo Moun-
tain and Swift River. The amphibolite is olive, being
spotted with white feldspar or marble to varying degrees.
It is strongly foliated and almost invariably the foliation
is refolded (Fig. 37). It is composed mainly of actinolite
where the amphibolite is devoid of calcite and of tremo-
lite where calcite is present. Epidote, albite, chlorite,
sphene and opaques are the most common minor consti-
tuents. The actinolite and tremolite crystals are less than
2 mm long in most places. Larger ones occur where the
amphibolite is associated with garnet-bearing schist as

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