27 TaBLEe I—Concluded Pine Peace Halfway Sikanni Alaska Liard Lower Rae : F Chief Highway, nar Mackenzie f: River River River Rocky Mts. Plateau Valley 3 5 Limestone ES and dolo- ——____ OF mite Argillites a “ES Conglomerate 5 Mt. Selwyn and sand- 8 formation stone (Mac- 5 dougal)* Macdougal Katherine a Sa ee g Ieee) Quartzites, ° Misinchinka argillites, 2 schists schists, & basic dykes *Formation and group names used by Laudon and Chronic, 1947, 1949. Muncho Lake The younger group of pre-Silurian rocks along the Alaska Highway, mentioned in a preceding paragraph, is less folded than the older group exposed there. It lies unconformably below the Silurian, but unlike the older group shows no discordance with it (Williams, 1944; Laudon and Chronic, 1947). It outcrops along the west side of Muncho Lake and in the valley of Trout River, and consists of about 5,000 feet of coarse, red conglomerate and grey sandstone, with possibly some limestone (Williams, 1944). Laudon and Chronic describe nearly flat-lying unmetamorphosed limestone in the McDonnell Creek section. Williams compares this younger group of unfossiliferous rocks with the Cambrian beds of Gravel (Keele) River and Franklin Mountains on the basis of similar stratigraphic position and similar lithology. Laudon and Chronic (1947, 1949) compare it with the Cambrian, Macdougal group of the Mackenzie Mountains and adopt the name Macdougal for the Alaska Highway beds. ORDOVICIAN Very little is yet known of the Ordovician in northeastern British Columbia. As exploration proceeds, however, more occurrences will doubtless be found. Recently the geologist of an oil company has found limestones and dolomites with Upper Ordovician fossils on Halfway River, west of Mount Wright. SILURIAN Alaska Highway Beds, mostly limestones, of Middle Silurian age outcrop in several places along the Alaska Highway, between Summit Lake and Trout River. They have been described by Williams (1944) and by Laudon and Chronic (1947, 1949).