DISCLAIMER: This English version is translated from the original French. In case of any discrepancy, the French version shall prevail.
|Stratotype:||Type section of the Indicator Formation (now Indicator Group) of Chown and Caty (1973) located on the north face of the hill north of Conflans Lake (52º26’N, 70º47’W)|
|Type area:||Conflans Lake area (NTS sheet 23D07)|
|Geological province:||Superior Province|
|Geological subdivision:||Opatica Subprovince|
|Lithology:||Conglomerate and sandstone|
The « Shikapio Formation » was established by Genest (1989) and refers to a lake in the NE Otish Basin (sheet 23D07). The Shikapio Formation corresponds to the last two units described by Chown and Caty (1973) in the type section of the Indicator Formation, later elevated to the rank of group (Indicator Group) by Genest (1989). Correlations between the different nomenclature used in previous work are summarized in the Otish Supergroup record and in the summary table of Genest (1989, p. 21). The Ministère‘s compilation maps (2010a-c) are essentially based on descriptions from Genest (1989) which are summarized in the following section.
The Shikapio Formation consists of conglomerates and sandstones comparable to those of the underlying Matoush Formation. However, the decrease in bed thickness and the presence at the top of a mudstone bed characterized by the presence of desiccation cracks suggest a decrease in sedimentary dynamics. Genest (1989) divided the formation into two separate members, Member A composed of conglomerates, and Member B composed of sandstone. This division is not used here.
Conglomerates have the same lithological and petrographic characteristics as those of the Matoush Formation. Sandstone is feldspathic to quartzitic in composition, medium to coarse grained, well sorted and finely laminated, with large oblique stratifications. They vary in colour between pink, white and beige, reflecting the alternating thin laminations. Summital quartzitic sandstone is charaterized by the presence of red, locally beige mudstone beds with dessication cracks.
The stratotype of the Shikapio Formation is described by Chown and Caty (1973) in the type section of the Indicator Formation (now Indicator Group) on the north side of the hill north of Conflans Lake:
The Ministère’s geological compilation maps distinguish this unit in sheets 22M15 and 22M16 (MNRF, 2010a).
The Shikapio Formation is ubiquitous throughout the Otish Basin. It generally forms a main strip that follows the trace of a regional syncline of general NE-SW orientation (bottom half of sheet 23D and sheet 22M13). It is also observed intermittently in sheets 22M15 and 32P16. The thickness of the formation is highly variable, ranging from 32 to 645 m. For example, the basal conglomerate sequence (Member A of Genest, 1989) is 20 m thick on average in the NE part of the basin (southern half of the sheet 23D), while it reaches 432 m in the Indicateur Lake area (sheet 22M13).
The Shikapio Formation 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 Shikapio Formation is conformably overlying the sandstone sequence of the Matoush Formation. The transition from Matoush Formation sandstone to Shikapio Formation conglomerate is transitional. The Shikapio Formation is overlain by polymictic conglomerate of the Laparre Formation (Péribonca Group). In the northern part of the Otish Basin, it is cut by the Otish Gabbro (Genest, 1989).
Does not apply.
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 thesis, 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). Shikapio Formation. Quebec Stratigraphic Lexicon. http://gq.mines.gouv.qc.ca/lexique-stratigraphique/province-du-superieur/formation-de-shikapio_en [accessed on Day Month Year].
Céline Dupuis, P. Geo., Ph.D. céline.firstname.lastname@example.org (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); André Tremblay (HTML editing).