Figure 7. Yanks Peak Formation conformably overlying
Yankee Belle Formation on the hill northeast of Little
River. (GSC 191004)

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Figure 8. Palinspastic isopach map of the Yanks Peak
Formation.

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only 60 m thick, more homogeneous and finer grained.
Stratigraphic differences across fault zones with the
magnitude presented here are usually used as indicators
of large displacement along the fault. The geometry of
the Kimball Fault does not justify large dip-slip displace-
ment. This implies rapid thickness and grain size changes
of the Yanks Peak Formation at Kimball Ridge or strike-
slip displacement on the Kimball Fault. The palinspastic
isopach map of Figure 8 assumes dip-slip movement on
the Kimball Fault for purposes of simplification. West-
ward through the Black Stuart Synclinorium the unit is
mainly less than 40 m thick. Its average thickness in-
creases slightly in the westernmost faulted sequence of
the Cariboo Terrane passing through Roundtop Moun-
tain southward to the ridge northeast of Little River.
Holland (1954) and Sutherland Brown (1957,1963) sug-
gested that the formation is as thin as | m in this area,
however, the thinness is attributed to attenuation on fold
limbs and in thrust faults.

For reference, a partial section on Mount Kimball
(52°55’40’’N, 121°3’02’’W) of Yanks Peak Formation
continuous with Yankee Belle Formation, can be used
(Table 5).

Sutherland Brown (1963, p. 32) suggested from con-
siderations of composition, thickness and sorting that the
Yanks Peak Formation was deposited in a shallow marine
basin. Young (in Campbell et al., 1973, p. 47-48) postu-
lated that the quartzites are littoral deposits, separated
by shallow marine fine clastics deposited during periods
of transgression. Mansy (1970, p. 56) from comparisons
of statistical grain size curves derived for the Yanks Peak
Formation quartzite, concluded the Yanks Peak Forma-
tion Quartzites are fluviatile.

This study presents no data different from that pre-
sented by these three workers. Young’s hypothesis comes
from work covering more geographic area than either
Mansy or Sutherland Brown and may therefore be more
realistic. It is accepted here.

From geographic distribution of facies, Young pos-
tulated a south to southwest dispersal trend. The paleo-
geographic distribution, as approximately pictured in
Figure 8, does not dispute Young’s hypothesis. However,
Young (1969, p. 105) argued that the Yanks Peak For-
mation quartzite of Summit Creek is a sandstone tongue
representing ‘‘the westernmost progradation of the Yanks
Peak Formation’’. With a south-southwest dispersal
trend, quartzite of the Yanks Peak Formation farther
south should be thinner and finer grained than at Summit
Creek. The quartzite of the Roundtop Mountain area is
as thick and thicker and as coarse and locally coarser than
at Summit Creek. It is associated with white quartzite of
the upper Yankee Belle Formation which is absent at
Summit Creek. The quartzite of the Roundtop Mountain
area could be a more proximal facies than Summit Creek,
but this contradicts southerly dispersal trends, but not
southwesterly dispersion or complex trends involving
various current patterns. A complex pattern is required