Opaque rings and in one example cuts across several rings. The radial growth is possibly secondary, and may be superimposed over an algal laminate structure. A sample examined in detail contains approximately 60% pellets, 4% silt-size quartz, 3% muscovite (silt-size) and 33% matrix of calcite and fine opaques. Grey to olive siltite is found in all occurrences of Yankee Belle Formation but is more prominent in west- ern exposures and north of Cariboo River. Grey, grey- olive and lesser amounts of white quartzite are found in most exposures except at Summit Creek. It is fine- to medium-grained, micaceous and sorted. It occurs throughout the section but coarsens and increases in per- centage stratigraphically upward everywhere except at Summit Creek. Gradations within the sequence occur as discrete but small clast-size changes between beds, not as internally graded beds. Bedding thickness ranges from 3 to 75 cm and is commonly 10 to 30 cm. The siltstone- quartzite sequences develop a characteristically 0.5 to 1.5 cm spaced cleavage which anastomoses irregularly around lenses of quartzite. Light grey to white fine grained quartzite beds commonly occur near the top of the Yankee Belle Formation below the massive white quartzites of the Yanks Peak Formation. South of Cari- boo River, in western exposures, quartzite does not occur with the basal limestones. In eastern exposures there is more quartzite throughout the section and it is coarser grained. Both Mansy (1970) and Young (1969, in Campbell et al., 1973) described three cycles of sedimentation within the Yankee Belle Formation. The lowest cycle consists of a sequence of shale beds which coarsen upsection to a cap of sandstone, the middle one of repeating limestone and pelite beds and the upper one of upward coarsening shale to sandstone sequences which at the top coarsen into the overlying quartzite of the Yanks Peak Formation. The middle and upper cycles, but not the lower, are found south of Cariboo River and are well developed on Kimball Ridge. North of Cariboo River only the upper cycle of shale-sandstone was observed. A reference section of Yankee Belle Formation (Table 4) is on eastern Kimball Ridge (52°55’N,121°01’’W). Age and correlation. Campbell et al. (1973) mapped the Yankee Belle Formation as Hadrynian, because they cor- related it with the uppermost part of the Hadrynian upper Miette Group of the Rocky Mountains. A summary dia- gram showing recent correlations is displayed by Mansy and Gabrielse (1978, p. 2). No new information was gathered to re-evaluate these correlations. Yanks Peak Formation The Yanks Peak Formation consists of quartzite, siltite, slate, phyllite and minor calcareous sandstone. White coarse grained orthoquartzite is characteristic of the Yanks Peak Formation in the Cariboo Terrane. It may be confused with a similar, but better sorted and massive quartzite, of the Keithley succession of the Barkerville Terrane. The Yanks Peak Formation orthoquartzite, however, has a larger variation in grain size and colour, is slightly richer in muscovite and shows bedding and locally crossbedding. The Yanks Peak Formation mainly underlies the area south of Cunningham Creek Pass and east of the Pleas- ant Valley Thrust. An isolated exposure occurs at Summit Creek northeast of Wells. The type section of the Yanks Peak Formation is defined as the reference section described by Young (in Campbell et al., 1973) from an area at the headwaters of Dome Creek in northern Cari- boo Mountains. The original type section on Yanks Peak was described by Holland (1954), but is no longer repre- sentative of the Yanks Peak Formation as viewed today. It does not contain rocks reliably equivalent to those called Yanks Peak Formation in the Cariboo Terrane and should be abandoned. Young reported the Yanks Peak Formation to have a maximum thickness of 580 m near Betty Wendle Creek. It thins to the north and northeast and at the type section is 403 m thick. In the map area the thickness ranges from | to approximately 300 m or more. On Kimball Ridge the Yankee Belle Formation is capped by 280 m of Yanks Peak Formation quartzite below a zone where structural complications disrupt the sequence. The lower contact of the Yanks Peak Formation is conformable with the Yankee Belle Formation. In most places it is gradational but locally sharp (Fig. 7). Grada- tional relationships are best seen on Roundtop and Kimball mountains. There the Yankee Belle Formation has increasing numbers and thickness of white quartzite beds within a 30 m thick interval approaching its upper contact. The contact is defined at the base of the first thick bed (1.5 m or more) of medium- to coarse-grained white orthoquartzite. Quartzite of the Yanks Peak Formation is generally white and can be light grey to black, brown or pink. In western exposures the colour changes upsection from white to dark grey. The quartzite is mostly medium- to coarse-grained and can be very coarse grained to granule conglomerate. The grains are subrounded and sorted to well sorted. The matrix is mainly quartz with minor sericite and muscovite and locally is calcite. Siltite, slate and phyllite are grey and olive grey and exist as minor thin interbeds to the quartzite locally and generally in the eastern exposures. They are much like rocks of the Yankee Belle and Midas formations. Bedding characteristically is thick and indistinct, although in areas it is well displayed by interbeds of fine grained rock and by compositional variations in the matrix. Grading and crossbedding occur locally. The thickness of the Yanks Peak Formation varies considerably throughout the area, generally thinning to the southwest (Fig. 8). It is more consistent within fault bounded sequences. The formation is greater than 300 m thick and is most diverse and coarsest grained on Kimball Ridge east of the Kimball Fault. West of the fault it is