Mistassini Group
Stratigraphic label: [ppro]mi
Map symbol: pPmi

First published: 27 March 2018
Last modified:

Translation of original French

Informal subdivision(s)
Numbering does not necessarily reflect the stratigraphic position.
 
None
 
Author: Faribault et al., 1912
Age: Paleoproterozoic
Reference section: None
Type area: The “Papaskwasati Bowl”, located in the northern part of Mistassini Lake, is the preferred location for studying the gradual contact between the four formations of the Mistassini Group (see Caty, 1976, figure 15); NTS sheets 32P02, 32P07 and 32P10
Geological province: Superior Province
Geological subdivision: Opatica Subprovince
Lithology: Sedimentary rocks
Type: Lithostratigraphic
Rank: Group
Status: Formal
Use: Active
Related unit(s)
  • Mistassini Group

Background

Rocks of the Mistassini Group were initially compared to Cambrian rocks on the east side of James Bay (Low, 1886), and then to Upper Huronian limestone (Low, 1906). This unit was initially designated as the Mistassini Limestone and correlated with the Lower Huronian (Faribault et al., 1912). It was later named Mistassini Series (Norman, 1940), then renamed Mistassini Group by Bergeron (1957) to include all sedimentary rock units characterizing the Mistassini and Albanel lake areas, namely the Papaskwasati, Cheno, Albanel and Témiscamie formations.

Description

The Mistassini Group includes the following four formations:

  • the Témiscamie Formation (pPte), consisting of cherty iron formation, clayshale, quartzite, wacke and siltstone;
  • the Albanel Formation (ppal), consisting of dolomite, stromatolitic dolomite, clay dolomite, intraformational breccia, graphitic dolomite and chert;
  • the Cheno Formation (pPcn), consisting of sandstone, conglomerate, sandy dolomite and stromatolitic dolomite;
  • the Papaskwasati Formation (pPpw), consisting of conglomeratic sandstone, conglomerate and sandstone.

Thickness and distribution

The Mistassini Group, also known as the Mistassini Basin, covers an area of 7300 km2. It includes the four sedimentary formations mentioned above, located on the periphery of Mistassini and Albanel lakes and in the Pépeshquasati River area (Caty, 1976). 

Dating

Seven (7) samples of mudslate from the Témiscami Formation, which lies at the top of the Mistassini Group, were analyzed with the Rb-Sr method and helped define an isochrone at 1787 ±55 Ma (Fryer, 1972).

Isotopic System Mineral Crystallization Age (Ma) (+) (-) Reference(s)
Rb-Sr Biotite 1787 55 55 Fryer, 1972

Stratigraphic Relationship(s)

From a chronostratigraphic point of view, the Mistassini Group sedimentary rocks postdate those of the Chibougamau Formation, although the two units never appear in direct contact. On the field, the Mistassini Group sedimentary rocks unconformably overlie a basement made up of Mesoarchean to Neoarchean rocks in contact with the Opatica Subprovince and the Parautochton of the Grenville Province. The basement, which appears heavily altered in the first few metres of contact with sedimentary rocks, corresponds to a paleoregolith (Caty, 1976).

Paleontology

Does not apply.

References

9 mai 2019
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