39
Pleasant Valley Epoch

Deposition of caleareous and carbonaceous clays and volcanic ashes
characterized this epoch. Near or after its close, basic lava was extruded
subaerially, as shown by its brecciation and total lack of pillow structure.

Epoch of Deformation, Intrusion, and Erosion

Subsequent to the time of deposition of all the preceding formations,
the country was mountain-built, the formations were folded along north-
westerly trending axes, and recrystallized into quartzites, schists, and slates.
Great shear zones and hinge faults were developed, and the Proserpine
sills and dykes of quartz porphyry and felsite were intruded. The intrusion
of the sills and dykes was intermittent and continued throughout the time
of deformation, since some of them are schistose, and some of them are
distinctly granitoid. It was during this time, and as an accompaniment of
the sill and dyke intrusion, that the shear zones of the Cariboo series were
extensively replaced by great lenses and veins of quartz (“‘A”’ veins). Both
the minor intrusives and vein deposits were probably offshoots from, or
genetically related to, major intrusions which erosion did not succeed in
unroofing before the subsequent submergence of the country beneath the
Mississippian sea.

The first series of cross-range faults was formed by the settling down of
the country after its elevation into the anticlinorium. These faults were
then healed with quartz, and mineralized with galena, pyrite, sphalerite,
and highly auriferous arsenopyrite (‘‘B”’ veins).

PALMHOZOIC RECORD

Slide Mountain Epoch

Gradual submergence of the country beneath the Carboniferous sea
which covered a large part of British Columbia caused the partial assort-
ment and burial of the surface debris of the previous epoch of denudation,
and the formation of the Guyet conglomerate. The presence of free gold
in the conglomerate points to the existence of auriferous lodes reaching the
old surface of the Cariboo series; the liberation of the gold during the inter-
vening erosion epoch; its concentration in the surface debris; and its
possible later transportation and deposition as beach placers in the Guyet
conglomerate.

During the Slide Mountain epoch, there ensued the deposition of beds
of grit (top of the Guyet formation), the formation of the crinoidal Green-
berry limestone, and the deposition of alternating thin beds of chert and
clay. The association of basic lava flows of the Waverly formation with
the chert and indurated shale points to contemporaneous vulcanism.
Succeeding these events, there was the deposition of a considerable thickness
of massive limestone (as exposed on Spectacle lake, Swamp river, and Bear
river) which is probably the equivalent of Dawson’s Marble Canyon
limestone, of Pennsylvanian age.

1Geol. Surv., Canada, Ann. Rept., vol. VII, pt. B, p. 39 (1896).