2

for a width of 15 miles and a length of more than 50 miles. Only 50 miles
of the anticline has been mapped so the total length is not known. Intrud-
ing the Cariboo series are a few dykes and sills of quartz porphyry and
allied acidic rock types. They are called the Proserpine intrusives and are
believed to be pre-Mississippian and possibly Precambrian in age. Uncon-
formably overlying the northeastern limb of the anticline is the Slide
Mountain series of Upper Paleozoic age, consisting from bottom to top
of conglomerate, crinoidal limestone, banded chert, argillite, and basaltic
lavas. The upper part of the series is cut by many gabbroic dykes. The
series dips northeast. Overlying the southwestern limb of the anticline,
also unconformably, are Jurassic argillites and basalts called the Quesnel
River group. The sediments of the group dip southwest.

CABIBOO SERIES

The Cariboo series is of special interest for in it are all the known lode
gold deposits of the district. In Barkerville map-area the series has been
divided into three formations.1

Pleasant Valley formation
Barkerville formation
Richfield formation

The Richfield formation, the lowest exposed formation of the Cariboo
series, consists mainly of quartzite, but includes as well limestone, black
argillite, and other rock types gradational between the three named. The
members of the formation do not extend far as distinct lithological units,
but change gradually along the strike and dip from quartzite to argillite
or to limestone and from argillite to limestone. In the vicinity of Barker-
ville, however, the lower half of the formation is mainly quartzite. Above
this are several members of black argillite separated by quartzite mem-
bers, several of which contain thin beds of limestone. The uppermost
part of the formation consists of limy quartzite becoming more limy
towards the top. The Barkerville formation overlies the Richfield forma-
tion conformably and consists mainly of bluish grey limestone, commonly
in beds 20 feet or more thick, black argillite, commonly limy, and quartzite.
The Pleasant Valley formation overlies the Barkerville formation and con-
sists mainly of black argillite.

The rocks of the series have yielded in a varying degree to shearing
stresses, so that although the general nature of the original rock is rarely
in doubt the bedding in some places has been obscured, and the strength
of the rocks has been changed. Some quartzite members several hundred
feet thick show signs of shearing only along bedding planes. Other quartz-
ite beds have been changed to sericite schists and quartz-sericite schists.
Thick beds of argillite are in general only slightly sheared, but locally
argillite has been changed to graphitic schist. Limestone has become
marble. Beds of schistose rocks containing many scattered crystals of
ankerite, and locally quite fissile, are common, and have been formed

—— rn
1 Johnston, W. A., and Uglow, W. L.: “ Placer and Vein Gold Deposits of the Barkerville District,
B.C.”’; Geol. Surv., Canada, Mem. 147 (1926).