to explain the absence of quartzite between areas where thicknesses can be up to 60 m. A simple southwest dis- persion would require gradual diminishing of quartzite to the southwest. This gradual diminishing is not the picture presented in Figure 8. Table 5. Yanks Peak Formation incomplete stratigraphic section on Mount Kimball (location; 52°55’40’”N, 121°3’02”W). Thickness in metres Unit Lithology Unit Above base 13 Quartzite, white, coarse grained to fine granule conglomerate, coarsens upsection, crossbeds in lower part Um. ek ee. Sed os al vi 45 280 Interbedded micaceous quartzite, grey, and well sorted white quartz- ite, moderately coarse grained .... 2 235 tks PO 1 ok. Quartzite, white, moderately coarse ee ee cas nin us 10 239 Interbedded slate, olive-green- brown, silty, micaceous quartzite, brown weathering grey, moderately fine grained and well sorted quartz- ite, light pink, medium grained; "Oe CRS] CY el ag a 4 Des Quartzite, olive and brown weather- ing grey, micaceous, moderately RCS cts ee oe 4 219 1 oO ide) (oe) Quartzite, white, well sorted, coarse- to granule-grained ....... 28 210 ~N Quartzite, grey, moderately fine grained; slightly sericitic ........ 3 187 (op) Sandstone, brown limonite (CATE Ce eee ee er 02 184 Interbedded quartzites, light green, well sorted, moderately fine and olive grey, micaceous medium ie ih. se ae d= 10 184 Conglomerate, white, granules of rounded to subrounded clear quartz with minor blue quartz .......... 1 174 on b wo Interbedded quartzite, dark brown weathering grey-brown, micaceous, moderate to moderately fine grained, poorly sorted, limonite, slate, olive and minor quartzite, white, medium grained; gradational 1 to 30 cm beds with 3 to 10 cm es CONMION a a8 We Bw ow 90 173 DO Quartzite, grey, micaceous, medium grained: 15 to 50 cm beds ...... 30 83 Quartzite, white, medium grained . 53 53 — Underlying beds: Yankee Belle a Formation Age and correlation. Campbell et al. (1973) considered the Yanks Peak Formation to be of lowermost Cambrian age and correlated it with the McNaughton Formation of the Rocky Mountains directly to the east. No further evidence on the age of the Yanks Peak Formation has been obtained and the conclusion of Campbell et al. is accepted here. Midas Formation The Midas Formation consists of slate, phyllite, siltite and quartzite. It can be differentiated from the Yankee Belle Formation in four ways: 1) the Midas Formation is not known to have limestone members in its basal part as does the Yankee Belle Formation; 2) the pelites of the Midas Formation are generally greyer and more platy where not metamorphosed to phyllite; 3) if present, the crossbedded Vic Sandstone with its lamellae of heavy minerals is dis- tinct from any lithology in the Yankee Belle Formation; and 4) the Yankee Belle Formation coarsens upsection to the Yanks Peak Formation whereas the Midas For- mation fines upwards to the Mural Formation. Where the Yanks Peak Formation quartzite is not present the contact between the Yankee Belle Formation and Midas Formation is difficult to define; however, in almost all cases there is at least a lens of white fine- to medium- grained quartzite at the horizon where the Yanks Peak Formation is expected. In isolated small outcrops distinc- tion between Midas and Yankee Belle formations is uncertain. Midas Formation has not been recognized north of lower Pleasant Valley Creek though it underlies much of the area to the south. The type locality of the Midas For- mation is defined as the reference section described by Campbell et al. (1973) from the Dome Creek area (56°36’N, 121°01’W). The original type section defined by Holland (1954) at Yanks Peak is recommended to be abandoned. It does not contain the same unit of rocks as those called Midas Formation east of the Pleasant Valley Thrust. At the Dome Creek section the unit is 148 m thick and the thickness varies from 91 to 305 m throughout the Cariboo Mountains (Campbell et al., 1973). Thickness of the formation throughout the map area varies from 40 to 250 m. North of Cariboo River, the thickness is determined at two localities. The formation is approximately 40 m thick with the base unexposed at the junction of Pleasant Valley and Antler creeks, and about 45 m thick at Loskey Creek. Thicknesses south of Cariboo River can be determined for three localities. On the hill 5 km southeast of Black Stuart Mountain, it is approximately 50 m thick, bounded on top by archaeo- cyathid-bearing Mural Formation limestone and at the base by a thin quartzite lens assigned to the Yanks Peak Formation. On Anderson Ridge,! poorly exposed Midas Formation may attain 250 m in thickness. On the south slopes of Kimball Ridge a partly covered succession is approximately 130 m thick. "Anderson Ridge is the east-trending ridge south of upper Kimball Creek and southwest of upper Connection Creek. This name was used by Lang (1938). 17