Unit Name: Wharton Group
Unit Type: Lithostratigraphic
Rank: Group
Status: Formal
Usage: Currently in use
Age Interval: Late Paleoproterozoic (1800 - 1600 ma)
Age Justification: Geochronology. The Wharton Group is given an age range of 1750-1765 Ma (U-Pb zircon magmatic age) by Peterson and van Breeman (1999) (Peterson, 2006). LeCheminant et al. (1987b) have reported a U-Pb radiometric age of 1760 Ma for the volcanic flows. A U-Pb radiometric age of 1748 Ma has been obtained for one of the rapikivi granite plutons (C. Roddick, unpublished data), and other plutons have ages up to 1.76 Ga (LeCheminant et al., 1987a) (Gall et al., 1992).
Province/Territory: Northwest Territories; Nunavut
Originator: Gall et al., 1992.
Distribution:
The Wharton Group extends southwest from the west end of Baker Lake to Kasba Lake (NTS 65D), the Nunavut-Northwest Territories (Peterson, 2006). It is up to 200 m thick (Gall et al., 1992).
Locality Data:
Thickness(m): Maximum 200.
Lithology:
The Wharton Group consists of intercalated grey, maroon and red rhyolite to dacite flows, pyroclastic rocks, and subordinate sedimentary rocks. Granite and granodiorite, which locally display rapikivi textures and contain fluorite, intrude the Baker Lake Group (Gall et al., 1992).
Relationship:
The Dubawnt Supergroup (Gall et al., 1992), from oldest to youngest, includes the Baker Lake Group, Wharton Group, and Barrensland Group (Rainbird and Hadlari, 2000). The Wharton Group includes, from oldest to youngest, the Amarook Formation, Pitz Formation, and Nueltin suite. An intrusive contact separates the Pitz Formation from the Nueltin granite suite (Peterson, 2006). The Wharton Group is separated from the underlying Baker Lake Group and from Early Proterozoic and Archean basement rocks by an angular unconformity. It is unconformably overlain by the Barrensland Group. The granites typically have phenocryst assemblages identical to local extrusive rocks, and LeCheminant et al. (1979) and Booth (1983) have demonstated that the Pamiutuq Granite is coeval and cogenetic with the Pitz Formation volcanic rocks in the Pamiutuq Lake area. Thus, the anorogenic granites are considered to be shallow intrusive equivalents of the Pitz Formation (Gall et al., 1992).
History:
Gall et al. (1992) proposed that this sequence of volcanic and sedimentary rocks and granitic intrusions be assigned to the Wharton Group, named after a lake permitting access to the largest exposed area of volcanic rocks (Gall et al., 1992).
References:
Booth, G.W., 1983. The petrology and geochemistry of the Pamiutuq Lake Batholith, Northwest Territories; M.Sc. thesis, University of Toronto, Toronto, 168 p.
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.
LeCheminant, A.N., Lambert, M.B., Miller, A.R., and Booth, G.W., 1979. Geological studies: Tebesjuak Lake map-area, District of Keewatin; Geological Survey of Canada, Current Research, Paper 79-1A, pp. 179-186.
LeCheminant, A.N., Miller, A.R., and LeCheminant, G.M., 1987a. Early Proterozoic alkaline igneous rocks, District of Keewatin, Canada: petrogenesis and mineralization; in, Geochemistry and mineralization of Proterozoic volcanic suites, ED. T.C. Pharaoh, R.D. Beckinsale and D. Richard; Geological Society of London, Special Publication 33, p. 219-240.
LeCheminant, A.N., Roddick, J.C., and Henderson, J.R., 1987b. Geochronology of Archean and Early Proterozoic magmatism in the Baker Lake - Wager Bay Region, N.W.T.; Geological Association of Canada and Mineralogical Association of Canada, Program with Abstracts, v. 12, p. 66.
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 Hadlari, T., 2000. Revised stratigraphy and sedimentology of the Paeloproterozoic Dubawnt Supergroup at the northern margin of Baker Lake Basin, Nunavut. Geological Survey of Canada, Current Research 2000-C8, 9pp.
Source: Murray Frarey's Precambrian Lexicon
Contributor: Michael Pashulka
Entry Reviewed: No
Name Set: Lithostratigraphic Lexicon
LastChange: 24 Nov 2010