Dubawnt Supergroup

Unit Name: Dubawnt Supergroup
Unit Type: Lithostratigraphic
Rank: Group
Status: Formal
Usage: Currently in use
Age Interval: Orosirian - Ectasian (2050 - 1200 ma)
Age Justification: Stratigraphic and intrusive relationships: the South Channel Formation, the lowest unit in the Supergroup rest unconformably on Hudson intrusions dated at ca. 1.84 Ga, and the Supergoup is intruded by Mackenzie Dykes that have been dated at 1.276 Ga (Peterson, 2006). The Dubawnt Supergroup detrital zircon age data set shows concentrations ca. 2.75–2.6 Ga, 2.1–1.9 Ga, and 1.85–1.75 Ga, concordant with the known ages of major juvenile crust–forming events leading up to fi nal amalgamation of Late Archean and late Paleoproterozoic supercontinents (Rainbird and Davis, 2007). Age data from the lowermost Baker Lake Group of the Dubawnt Supergroup suggest that the Baker Sequence (Baker Lake Group) was deposited over an interval of approximately 55 Ma (1840-1785 Ma), within error of the predicted periodicity of a second-order sequence (Rainbird et al., 2006).
Province/Territory: Northwest Territories; Nunavut

Originator: Gall et al., 1992

Lithology:

The Dubawnt Supergroup has been divided into three groups, in stratigraphic order, the Baker Lake Group, comprising subaerial and subaqueous siliciclastic rocks; the Wharton Group, comprising up to 200 m of intercalated grey, maroon and red rhyoloitic to dacitic flows, pyroclastic rocks and subordinate sedimentary rocks; and the Barrensland Group, that consists of the basal siliciclastic Thelon Formation, the mafic volcanic rocks of the Kuungmi Formation, and the uppermost siliceous stromatolitic dolostone of the Lookout Point Formation (Gall et al., 1992).

Age Determinations:

Method - U/Pb; Material - Zircon; Technique - SHRIMP; Age - 1754; Err_Minus - 2; Err_Plus - 2..

Method - U/Pb; Material - Zircon; Technique - SHRIMP; Age - 1833; Err_Minus - 3; Err_Plus - 3..

Method - U/Pb; Material - Zircon; Technique - SHRIMP; Age - 1758; Err_Minus - 3; Err_Plus - 3..

Method - U/Pb; Material - Zircon; Technique - SHRIMP; Age - 1757; Err_Minus - 3.4; Err_Plus - 3.4..

Method - U/Pb; Material - Zircon; Technique - SHRIMP; Age - 1753; Err_Minus - 1.7; Err_Plus - 1.7..

Method - Ar/Ar; Material - Phlogopite; Technique - Ar Furnace-Step; Age - 1837; Err_Minus - 8; Err_Plus - 8..

Method - Ar/Ar; Material - Phlogopite; Technique - Ar Furnace-Step; Age - 1811; Err_Minus - 12; Err_Plus - 12..

Method - U/Pb; Material - Xenotime; Technique - SHRIMP; Age - 1838; Err_Minus - 27; Err_Plus - 27..

Method - U/Pb; Material - Calcite; Technique - TIMS; Age - 1785; Err_Minus - 3; Err_Plus - 3..

Relationship:

The Dubawnt Supergroup rests unconformably on Archean and Early Proterozoic rocks that were deformed in the Hudsonian Orogeny (Gall et al., 1992).

References:

Gall, Q., Peterson, T.D. and Donaldson, J.A., 1992. Early Proterozoic stratigraphy of the Thelon and Baker lake basins, District of Keewatin: a proposed revision; in Current Research, Part C, Geological Survey of Canada Paper 92-1C, pages 129- 137.

Peterson, T.D., 2006. Geology of the Dubawnt Lake area, Nunavut-Northwest Territories; Geological Survey of Canada, Bulletin 580; 56 p.

Rainbird, R.H. and Davis, W.J., 2007. U-Pb detrital zircon geochronology and provenance of the late Paleoproterozoic Dubawnt Supergroup: Linking sedimentation with tectonic reworking of the western Churchill Province, Canada; GSA Bulletin, v. 119; no. 3/4, p. 314-328.

Rainbird, R.H., Davis, W.J., Peterson, T.D., Stern, R.A., Smith, S.R., Parrish, R.R., and Hadlari, T., 2006, Ar-Ar and U-Pb geochronology of a late Paleoproterozoic rift basin: Support for a genetic link with Hudsonian orogenesis, western Churchill Province, Nunavut, Canada: The Journal of Geology, v. 114, p. 1–17, doi: 10.1086/498097.

Source: Murray Frarey's Precambrian Lexicon
Contributor: P.H. Davenport
Entry Reviewed: No
Name Set: Lithostratigraphic Lexicon
LastChange: 22 Nov 2011