Unit Name: Franklin Mountain Formation
Unit Type: Lithostratigraphic
Usage: Currently in use
Age Interval: Late Cambrian - Early Ordovician (499 - 471.8 ma)
Age Justification: Mainly stromatolites, locally brachiopods, echinoderm ossicles, gastropods, straight cephalopods, trilobites and graptolites.
Province/Territory: Northwest Territories; Yukon Territory
Originator: M.Y. Williams, 1922 and 1923. Redescribed by Norford and Macqueen 1975.
A composite of scattered laterally discontinuous exposures on the northeast spur of Mount Kindle (63 deg 21'N, 123 deg 12'W). Base not exposed.
Crops out over most of the Parry Peninsula (Yorath et al., 1969) and over a wide arcuate band between the Smith Arm - Hare Indian River area and the upper Horton River (Cook and Aitken, 1971). Outcrop is common in the northeastern Cordillera, including the Franklin Mountains and frontal Mackenzies northwest to the Knorr Ranges (Norford and Macqueen, 1975; Norris, 1975). Known in the subsurface over most of the Northern Interior Plains (Gilbert, 1973; Kunst, 1974; MacKenzie, 1974; Macqueen and MacKenzie, 1973; Meijer-Drees, 1975; Tassonyi, 1969; G.K. Williams, 1974). Recognized in the subsurface of the Northern Yukon (Eagle Plain - Anderson Plain) by D.C. Pugh (pers. comm.). At the type section, the formation is a minimum of 280 m (917 ft) and estimated to be 310 m (1,017 ft) thick by Norford and Macqueen (1975). At Tenlen Lake A-73 well, the thickness is given as 823 m (2,727 ft) by MacKenzie (1974), and Gilbert (1973) gives a thickness range of 172 to 671 m (565 to 2,200 ft) in the Northern Interior Plains. Norford and Macqueen (1975) report 730+ m (2,400+ ft) of the upper "cherty" unit at Mobil's Colville E-15 well. D.C. Pugh (pers. comm.) measured as much as 1,222 m (4,010 ft) and estimates 1,676 m (5,500 ft) in the Eagle Plain. D.C. Pugh also measured a 779 m (2,556 ft) thick section at Snow Creek near the Alaska Border.
First described by M.Y. Williams (1922) as greater than 152 m (500 ft) of unfossiliferous pea green shales and red sandy shales. Redescribed by Williams (1923) at the type section as grey, buff-weathering calcareous shale with red interbeds grading upwards into buff limestones. Norford and Macqueen (1975) recognized three mappable rock units, which can commonly be distinguished in the subsurface. These are: 1) a basal "cyclic" unit consisting of several types of dolomite, weathering pale yellowish-orange, arranged in a repetitive order and containing red and green mudstone at the base, not exposed at the type section; 2) a middle "rhythmic" unit consist-ing of alternations of two types of dolomite, one fine- to medium-crystalline brownish-grey to light commonly oolitic, brown, and the other very finely crystalline greyish-orange to brownish-grey silty dolomite commonly with flat pebble conglomerate at the top; and 3) an upper unit of finely to coarsely crystalline thick-bedded dolomite containing white chert, drusy quartz, silicified oolites and stromatolites. The upper unit is interpreted to disconformably overlie the "rhythmic" unit (Norford and Macqueen, 1975). Two other local units are reported, the "basal Franklin Mountain red beds along the Mackenzie Arch" (Aitken, Macqueen ad Usher, 1973a) and a "porous dolomite" above the "cherty" unit in the subsurface (MacKenzie, 1974).
At the type section apparently is conformable and gradational from the Saline River Fm and unconformably overlain by the Mount Kindle Fm. Along with the Bear Rock Fm it underlies the Gilmore Lake Member (Langton Bay Fm) in the Anderson Plain Area. In the Mackenzie Arch and Bulmer Lake High it unconformably overlies Proterozoic strata (Aitken, Macqueen and Usher, 1973a; Meijer-Drees, 1975). Erosion below the Mount Kindle Fm is generally minimal, decreasingly important in the subsurface and increasing from west to east of the Northern Interior Plains where it eventually completely removes the Franklin Mountain Fm (G.K. Williams, 1974). Equivalent to parts of the Road River Fm in the Richardson, southwestern Mackenzie and Selwyn mountains. In the southern Mackenzie Mountains, it is equivalent to the Rabbitkettle and Broken Skull formations of Gabrielse et al. (1973 ) and others. Equivalent to part of Unit 5 of Norris et al. (1963). Was assumed to be Silurian in age and included in the Ronning Gp by Hume (1954), however, Macqueen (1970) and Norford and Macqueen (1975) recognized development of both the Franklin Mountain and Mount Kindle formations in the type area of the Ronning Gp, thus invalidating the latter. The base of the Franklin Mountain Fm correlates with the upper dark grey limestone of the Dodo Fm of older literature. In the subsurface west of Lac La Martre in the southwestern part of the Great Slave Plain, the term La Martre Falls Fm is applied to erosional remnants of the Mount Cap Fm, Saline River Fm and the Franklin Mountain Fm equivalents (Meijer-Drees, 1975).
Aitken and Cook, 1974a, 1974b; Aitken, Macqueen and Usher, 1973a; Balkwill 1971; Balkwill and Yorath, 1970a, 1970b; Bell, 1959; Cecile, 1978; Cook and Aitken, 1969, 1971; Douglas and D.K. Norris, 1963; Gabrielse et al., 1973; Gilbert, 1973; Hume, 1954; Kunst, 1974; MacKenzie, 1974; Macqueen, 1970; Macqueen and MacKenzie, 1973; Meijer-Drees, 1975; Norford and Macqueen, 1975; D.K. Norris, 1975; D.K. Norris et al., 1963; Tassonyi, 1969; G.K. Williams, 1974; M.Y. Williams, 1922, 1923; Yorath et al., 1969; Ziegler, 1969.
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: M.P. Cecile; L.V. Hills
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 28 Jun 2004