DISCLAIMER: This English version is translated from the original French. In case of any discrepancy, the French version shall prevail.
|Author(s):||Chown and Caty, 1973|
|Stratotype:||Two type sections of the Péribonca Formation (now Péribonca Group) were described by Chown and Caty (1973). The first, oriented approximately N-S, corresponds to the course of a small creek valley on the north side of the main range of the Otish Mountains (Member A; base of the section located at 52º23’N, 70º27’W). The second, oriented E-W, begins on the east bank of a small lake and ascends the western slope of the main range of the Otish Mountains (Member B; section base at 52º17’N, 70º42’W).|
|Type area:||Chance Lake area for the lower part of the unit and Frappe-à-Bord Lake for the upper part (NTS sheet 23D07; Chown and Caty, 1973)|
|Geological province:||Superior Province|
|Geological subdivision:||Opatica Subprovince|
|Lithology:||Detrital sedimentary rocks|
The Péribonca Group corresponds to the Péribonca Formation of Chown and Caty (1973) to which Genest (1989) added three units at the base which he associated with the Laparre Formation. Correlations between the different nomenclature used in previous work are presented in the Otish Supergroup record, and in the summary table and synthetic lithostratigraphic column of Genest (1989, pp. 21 and 53). The Ministère compilation maps (MRNF, 2010a-c) are essentially based on the descriptions of Genest (1989) summarized in the following section. The name comes from the Péribonca River, which originates in the Otish Mountains area (sheets 23D07 and 23D08).
The Péribonca Group groups oxidized units of the Otish Basin. Genest (1989) divided it into three formations based on their petrographic characteristics: the Laparre, Gaschet, and Marie-Victorin formations. This group differs from the underlying Indicator Group in several ways:
- presence of polymictic conglomerate units;
- presence of dolomitic cement;
- relative abundance of manganese and iron;
- development of albite and oligoclase in detrital fraction;
- presence of perlitic ferruginous chert clasts;
- presence of volcanic fragments;
- carbonate sedimentation (dolomite and magnesite);
- evidence of halite;
- local presence of gypsiferous cement.
Chown and Caty (1973) had divided the Péribonca Formation (now Péribonca Group) into two separate members: Member A being the upper part of the Laparre Formation and the lower part of the Gaschet Formation, while overlying Member B encompasses the upper part of the Gaschet Formation and the Marie-Victorin Formation. The trace of the Member A stratotype follows a small N-S creek valley on the north side of the Otish Mountains main range. The Member B stratotype begins east of a small lake and continues on the western slope of the Otish Mountains main range. Type sections of Chown and Caty (1973), as well as correlations with present subdivisions, are presented below:
|Actual Unit||Unit of Chown and Caty (1973)|
|Marie-Victorin Formation||Member B||105||Erosional top of section.|
|75-105||Well-bedded, interbedded grey and dark red arkose, minor polymictic pebble conglomerate, abundantly trough crossbedded, prominent reduction spots.|
|37-69||Coarse angular buff arkose interbedded with dark red argillaceous arkose. Reduction spots.|
|0-21||Interbedded well-sorted pink and grey subarkose and arkose, some carbonate cement, some quartz cement, with dark red coarse subangular arkose, minor argillaceous matrix (8-17 m covered).|
|0||Transition from lower member of formation.|
|Member A||198||Top of exposed section, less than 6 m to base of Member B.|
|192-198||Pink well-laminated arkose.|
|182-192||White crystalline dolomite, wavy stromatolitic bedding lower 3 m, chert nodules and numerous sandy layers in upper 6 m.|
|Laparre Formation (upper part)||175-182||Pink finely laminated and cross-laminated well-sorted arkose, carbonate cement.|
|168||Section offset by fault, section continued 1.6 km to the east.|
|132-145||White to dark red, well-sorted, subarkose, quartz cement, minor carbonate cement. Massive beds.|
|0-132||Pink and grey, well-sorted, subarkose and arkose, carbonate cement, rare beds with quartz cement, well laminated and cross-laminated. Minor polymictic conglomerate beds at 91 m. Covered interval, approximately 15 m from to first outcrop of Indicator Formation.|
Thickness and distribution
The Péribonca Group occupies the centre of the Otish Basin. It forms a strip that extends 140 km in a general NE-SW direction, following the trace of a regional synform, for a width varying from <10 km in the NE part to 30 km in the widest part. Its minimum thickness is estimated at 1200 m as the top is in erosional contact with overlying quaternary deposits (Genest, 1989). Paleoproterozoic units of the Otish Basin generally have low dips. The distribution of the different sedimentary units is largely controlled by the underlying Archean basement paleotopography, fault zones and topography of the area.
The Péribonca Group is cut by gabbro dykes and sills associated with the Otish Gabbro dated to 2169 Ma (Hamilton and Buchan, 2016; Miligragovic et al., 2016), giving it a minimum sedimentation age.
The Péribonca Group mostly conformably overlies quartz sandstone and red mudstone of the Shikapio Formation (Indicator Group). At only one location, it was observed unconformably (angular discordance) lying directly on Archean bedrock (Genest, 1989). It is cut by gabbro dykes and sills associated with the Otish Gabbro, mainly in the northern part of the Laparre Formation.
Does not apply.
Publications Available Through SIGÉOM Examine
MRNF. 2010a. CARTE(S) GÉOLOGIQUE(S) DU SIGEOM – feuillet 22M. CG SIGEOM22M, 16 plans.
MRNF. 2010b. CARTE(S) GÉOLOGIQUE(S) DU SIGEOM – feuillet 23D. CG SIGEOM23D, 16 plans.
MRNF. 2010c. CARTE(S) GÉOLOGIQUE(S) DU SIGEOM – feuillet 32P. CG SIGEOM32P, 16 plans.
Chown, E.H., Caty, J.L. 1973. Stratigraphy, petrography and paleocurrent analysis of the Aphebian clastic formations of the Mistassini-Otish Basin. In Huronian stratigraphy and sedimentation. Edited by G.M. Young. Geological Association of Canada; Special Paper 12, pages 49-71.
Genest, S. 1989. Histoire géologique du Bassin d’Otish, protérozoïque inférieur (Québec). Université de Montréal, doctoral thesist, 334 pages.
Hamilton, M.A., Buchan, K.L. 2016. A 2169 Ma U–Pb baddeleyite age for the Otish Gabbro, Quebec: implications for correlation of Proterozoic magmatic events and sedimentary sequences in the eastern Superior Province. Canadian Journal of Earth Sciences; 53, pages 119-128. https://doi.org/10.1139/cjes-2015-0131
Miligragovic, D., Beaudoin, G., Hamilton, M.A., King, J.J. 2016. The Paleoproterozoic Otish Gabbro suite and coeval dyke swarms of the Superior Province: Probing the ca. 2.17Ga mantle. Precambrian Research; 278, pages 126-144. https://doi.org/10.1016/j.precamres.2016.03.012
Ministère de l’Énergie et des Ressources naturelles (MERN). Péribonca Group. Quebec Stratigraphic Lexicon. https://gq.mines.gouv.qc.ca/lexique-stratigraphique/province-du-superieur/groupe-de-peribonca_en [accessed on Day Month Year].
Céline Dupuis, P. Geo., Ph.D. céline.email@example.com (redaction)
Mehdi A. Guemache, P. Geo., Ph.D. (coordination); Claude Dion, Eng., M.Sc. (critical review and editing); Céline Dupuis, P. Geo., Ph.D. (English version); Yan Carette (HTML editing).