Unit Name: Sadlerochit Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: Early Permian - Early Triassic (299 - 245 ma)
Age Justification: Corals, brachiopods, trilobites, pelecypods, and Spirophyton.
Province/Territory: Yukon Territory; Alaska
Originator: Leffingwell, 1919.
Type Locality:
Not designated but appears to have been on the south side of the Sadlerochit Mountains at about 69 deg 35'N, 145 deg 00'W according to Keller et al. (1961).
Distribution:
About 100 m (300 ft) in the type area. It is over 800 m (2,400 ft) on the south side of Joe Creek about 2.4 km (1.5 mi) west of the Yukon-Alaska boundary (68 deg 55'N, 141 deg 03'W). The formation was extended into the British Mountains by Mountjoy (1967b) who tentatively correlated a lower resistant 180+ m (600+ ft) thick unit with the Echooka Member and an upper shaly 131 m (430 ft) thick interval with the Ivishak Member. A 290 m (950 ft) interval of mudstones, dolomites and limestones near the headwaters of the Trail River and dated as Permian by Bamber and Waterhouse was tentatively correlated with the Echooka Member by Miall (1973). The Ivishak Member, except for the Joe Creek area appears to be absent in the Yukon.
Lithology:
Light coloured fine-grained sandstone or dark quartzite. West of the type area it contains shale, siltstone, limestone and chert. Keller et al. (1961) subdivided it into the Echooka Member consisting of sandy conglomerate, siltstone and sandstone of Permian age and the Ivishak Member consisting of shale of Triassic age which is mappable locally in the Romanzof Mountains (Sable, 1959) but not regionally (Brosgi et al., 1962).
Relationship:
The Sadlerochit unconformably overlies the Lisburne Gp in northeast Alaska and the Yukon. It is conformably overlain by the Shublik throughout its distribution except in the eastern areas where the Ivishak appears to be absent suggesting an unconformity. D.K. Norris (1974) indicates that the Shublik Fm overlies the Neruokpek Fm on the Yukon Coastal Plain and not the Sadlerochit Fm.
Other Citations:
Adkison and Brosgé, 1970; Brosgé et al., 1962; Keller et al., 1961; Kupsch, 1973; Lawrence, 1973; Leffingwell, 1919; Miall, 1973; Mountjoy, 1967b; Nassichuk, 1971; Nassichuk and Bamber, 1978; D.K. Norris, 1974; Sable, 1959.
Source: CSPG Lexicon of Canadian Stratigraphy, Volume 2, Yukon Territory and District of Mackenzie; L.V. Hills, E.V. Sangster and L.B. Suneby (editor)
Contributor: L.V. Hills; A.D. Miall
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 20 Aug 2004