30

cemented and weathered and there are similar occurrences of cemented
gravels and weathered zones beneath unweathered drift on Slough creek
benches and at other places in the area. There is no evidence of a true
soil or of vegetation of any kind on these surfaces nor in the interglacial ©
gravels, but the evidence does show pretty clearly that during Pleistocene
time there was at least one retreat and readvance of the ice, separated by
a fairly long period. The lack of evidence of vegetation during the inter-
glacial period seems to show that climatic conditions were not as favour-
able as at present. Pleistocene time is generally considered to have
extended over at least a million years, so that during this extensive period
very great erosion and deposition may have taken place. What seems
to have happened, however, in Barkerville area, is that during the great
part of the period the area, except possibly on the uplands, was actually
protected from erosion by the ice-sheet which was nearly stagnant.

Cemented glacials occur at many places in the area both at the surface
and at depths of over 200 feet below the level of the creeks. The cement
consists partly of iron oxide and partly of lime or calcium carbonate.
The occurrence of cemented gravels in Little valley, in Willow River
valley at the mouth of Mosquito creek, and at Slough Creek mine at
various depths below the creek level, may be due to the fact that the
groundwater has a slow circulation even at considerable depths and as a
result deposition from it of iron oxide and lime has taken place in post-
Glacial time. The relief of the surface would give a head for the water
and cause circulation of the ground water. The facts, however, that
cementation is known to take place fairly rapidly in gravels near the surface
in places where there is a marked oscillation of the groundwater-level or
alternate wetting and drying of the material, and that in the deeply drift-
filled valleys the cemented gravels occur at considerable depths where the
groundwater circulation must be very slow or is stagnant, seem to indicate
that cementation of the lower gravels took place during an interglacial
period, when the streams flowed at considerably lower levels.

Fossils in the deposits overlying bedrock are not abundant. A fossil
tooth was found by the present writer in the tailings from the New Waverly
hydraulic pit on Grouse creek. It had evidently come from the glacial
gravels exposed in the pit and has been determined by Mr. Charles
Sternberg, of the Geological Survey, as Elephas primigenius Blumenbach.
A fossil tooth, probably similar in character, was found about 1900 by
James Craig, Quesnel, in the bedrock gravels of the deeply buried channel
at the old Bonanza mine on lower Lightning creek. These fossils indicate
that the deposits in which they occurred are Pleistocene in age.

More detailed descriptions of the Pleistocene deposits and pay-streaks
on some of the creeks in the area and on a few creeks outside the area
are given in Chapter III.

GEOLOGICAL STRUCTURE
REGIONAL

The geological cross-section accompanying Bowman’s report on the
“Geology of the Mining District of Cariboo’? presents the only available

1Geol. Surv., Canada, Ann. Rept., vol. III (pt. I), pt. C, facing p. 26 (1889).