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Lithology. The Richfield formation constitutes the main part of
what is popularly known as the Cariboo schists, but strangely enough,
true schists form only a small element in the series. The rocks were origin-
ally mainly quartzose sediments, but are now metamorphosed to massive
quartzite, fine quartz pebble conglomerate, micaceous quartzite, quartz
slate, quartz sericite schist, sericite schist, carbonaceous and clay slate
vate minor intercalations of limestone, calcareous argillite, and silicified
tuff.

Massive, thickly bedded, light grey to greyish-black quartzite con-
stitutes one of the striking members of this formation. It is characterized
by abundant, glassy pebbles of quartz which give the rock a pseudo-
porphyritic appearance, and is splendidly exposed in upper Grouse Creek
canyon, along the old Barkerville-Stanley road in ‘the vicinity of Ella
lake, and in the narrow gorge between Burns and Amador mountains. In
all of these localities it breaks down into talus slopes of large, irregularly
shaped, dark-coloured fragments. An attempt was made to outline this
member on the map so as to elucidate the structure of the Richfield form-
ation, but the attempt failed because of the lack of continuous exposures.
It seems to be confined to one of the lowest exposed parts of the formation,
and is believed to constitute one of the most competent strata controlling
the regional deformation of the area.

Grading into the massive, thickly bedded quartzite is a more thinly
bedded, micaceous variety of pale brown, grey, or white colour and of a
more even-grained fabric. The beds vary in thickness from a fraction of an
inch to a foot, and the bedding planes are characterized by a parallel
arrangement of sericite flakes. Within the confines of each bed there is no
such parallel arrangement, and consequently no cleavage. Minute veinlets
of quartz traverse the beds in all directions, producing a characteristic
network. The prevalence of the faint brown colour seems to be due to the
hematite or limonite cement of the sandstone from which the quartzite
was derived. Excellent exposures of this member occur on mount Agnes
and mount Burdett, as well as in the canyons of Williams and Antler
creeks, above mentioned.

More thinly-bedded varieties of the same rock, representing stages of
transition into a sericite schist, are described as quartz slates and quartz-
sericite schists. They are distinctly quartzose in character as distinguished
from the clay slates and schists of the Pleasant Valley formation. Sericite
increases in amount in the transition until true schists are formed. These
quartz slates, quartz-sericite schists, and sericite schists are dominantly
pale brown in colour and very platy in structure. Commonly they are
strikingly drag-folded. The brown colour is due partly to the presence of
the iron oxides as original cements and partly to the impregnation of the
rocks with siderite and ankerite which were subsequently oxidized. These
more thinly bedded and schistose varieties of the quartzites originated
from argillaceous sandstones or arenaceous shales, and are particularly
well exposed just above the big bend on Grouse creek and in the various
creek canyons in the vicinity of Stanley.

A few thin bands of black, glistening, carbonaceous, and graphitic
slate occur associated with the quartzites. One of the most prominent of

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