Unit Name: Broadview Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Undefined
Usage: Currently in use
Age Interval: Cambrian - Devonian (542 - 359.2 ma)
Age Justification: The age of the Lardeau Group is constrained to be younger than late Early Cambrian (Waucoban) archaeocyathids in the underlying Badshot Formation (Fyles, 1964; Fyles and Eastwood, 1962; Wheeler, 1963a; Read and Wheeler, 1976; Fritz et al., 1991), but older than Mississippian (Viséan-Serpukhovian) conodonts in the overlying Milford Group of the Kootenay arc (Orchard, 1985). In the northern Selkirk Mountains, the age of the Lardeau Group is further constrained by cross-cutting granodiorite gneiss bodies in the Clachnacudainn complex and at the mouth of Downie Creek. At Downie Creek, a granodiorite gneiss that intrudes micaceous quartzite of the Akolkolex Formation yielded a U-Pb zircon age of 354 ± 1 Ma (Logan and Friedman, 1997). A similar granodiorite gneiss body in the eastern part of the Clachnacudainn complex, east of Revelstoke, also yielded an Early Mississippian age indicated by microfossils in the overlying Milford Group. Attempts to directly date the Lardeau stratipraphy have historically been unsuccessful (Logan and Colpron, 2006).
Province/Territory: British Columbia
Originator: Fyles and Eastwood, 1962.
Distribution:
The Kootenay terrane in the southeastern Canadian Cordillera (Logan and Colpron, 2006).
Lithology:
Much of the Broadview Formation is composed of blocky grey grit, dark-grey and green micaceous grit, and phyllite. Thick sequences of interbedded blocky and micaceous grits with more or less well-defined bedding planes are common. Blocky beds generally weather light grey and contain readily visible dark-grey to black rounded quartz grains. The quartz grains are not sorted; coarse grains locally as much as 1 centimetre across are scattered through a matrix of much smaller grains with wide ranges of sizes. Grits composed mainly of quartz are blocky; micaceous and carbonaceous varieties are phyllitic. In green grits visible quartz grains are whitish (Fyles and Eastwood, 1962).
Relationship:
Is the uppermost part of the Lardeau Group. From bottom to top this Group includes the Index, Akolkolex, Triune, Ajax, Sharon Creek, Jowett and Broadview Formations. The Broadview Formation overlies the Jowett Formation, but where the Jowett Formation is missing it overlies the Sharon Creek Formation. The Broadview Formation is thought to underlie the Milford Group with unconformity (Logan and Colpron, 2006).
History:
Walker and Bancroft (1929, p. 11) introduced the term Lardeau series to describe a "heterogeneous assemblage of metamorphosed sediments" in the northern Kootenay arc that overlies the Lower Cambrain (Waucoban) Badshot Formation and is unconformably overlain by the Mississippian Milford Group. Fyles and Eastwood (1962) formally defined the Lardeau Group based on their mapping of the Ferguson area in the northern Kootenay arc (Logan and Colpron, 2006).
References:
Fritz, W.H., Cecile, M.P., Norford, B.S., Morrow, D. and Geoldsetzer, H.H.J., 1991. Cambrian to Middle Devonian assemblages (Chapter 7). in, Gabrielse, H. and Yorath, C.J., eds., Geology of the Cordilleran Orogen in Canada: Geological Survey of Canada, Geology of Canada, no. 4, also Geological Society of America, The Geology of North America, v. G-2, p. 151-218.
Fyles, J.T., 1964. Geology of the Duncan Lake area, Lardeau District, British Columbia. British Columbia Min. Energy, Mines and Res., Bull. 49.
Fyles, James T. and Eastwood, G.E.P., 1962. Geology of the Ferguson area, Lardeau District, British Columbia; British Columbia Department of Mines and Petroleum Resources, Bulletin No. 45, 92 p. + XIV plates.
Logan, J.M. and Colpron, M., 2006. Stratigraphy, geochemistry, syngenetic sulphide occurrences and tectonic setting of the lower Paleozoic Lardeau Group, northern Selkirk Mountains, British Columbia. in, M. Colpron and Nelson, J.L., eds., Paleozoic Evolution and Metallogeny of Pericratonic Terranes at the Ancient Pacific Margin of North America, Canadian and Alaskan Cordillera: Geological Association of Canada, Special Paper 45, p. 361-382.
Logan, J.M. and Friedman, R.M., 1997. U-Pb agesfrom the Selkirk allochthon, Seymour Arm map-area, southeast British Columbia (82M/8 and 9), in Lefebure, D.V., McMillan, W.J. and McArthur, J.G., eds., Geological Fieldwork 1996: B.C. Ministry of Employment and Investment, Energy and Minerals Division, Geological Survey Branch, Paper 1997-1, p. 17-23.
Orchard, M.J., 1985. Carboniferous, Permian and Triassic conodonts from the central Kootenay arc, British Columbia: constraints on the age of the Milford, Kaslo and Slocan groups: Geological Survey of Canada, Paper 85-1A, p. 287-300.
Read, P.B. and Wheeler, J.O., 1976. Geology of Lardeau W/2 (82K W/2): Geological Survey of Canada, Open File Map 432, 1:125,000.
Walker, J.F. and Bancroft, M.F., 1929. Lardeau map-area, British Columbia; Geological Survey of Canada, Memoir 161.
Wheeler, J.O., 1963a. Rogers Pass map-area, British Columbia and Alberta, (82N W½) (Report and Map 43-1962); Geological Survey of Canada, Paper 62-32, 32 p. + Preliminary Map 43-1962, Geology, Rogers Pass (Golden, West Half), British Columbia-Alberta, NTS 82 N (West Half), Scale: One Inch to Four Miles = 1:253 440.
Source: LEXICON_BC
Contributor: Michael Pashulka
Entry Reviewed: No
Name Set: Lithostratigraphic Lexicon
LastChange: 29 Jun 2009