First published: 18 March 2021
Last modified:
DISCLAIMER: This English version is translated from the original French. In case of any discrepancy, the French version shall prevail.
| Author(s): | Sauvé and Bergeron, 1965 |
| Age: | Paleoproterozoic |
| Stratotype: | None |
| Type area: | Baby Lake area (NTS sheet 24K05, UTM NAD83, zone 19 : 455021 m E, 6458656 m N) |
| Geological province: | Churchill Province |
| Geological subdivision: | New Quebec Orogen (Labrador Trough)/Gerido Lithotectonic Zone |
| Lithology: | Sedimentary rocks, iron formation, basalt, tuff |
| Category: | Lithostratigraphic |
| Rank: | Not applicable |
| Status: | Informal |
| Use: | Active |
Background
Sauvé and Bergeron (1965) used the informal name « Upper Phyllites » to designate a unit of mudstone, phyllite and quartzite in minor proportion, forming the upper part of the Baby Formation. Subsequently, different terms have been used to refer to it, namely upper member of the Baby Formation (Clark, 1988; Wares et al., 1988; Wares and Goutier, 1989 and 1990; Goutier and Wares, 1991), Upper Baby unit or Upper Baby (Goulet, 1995; Clark and Wares, 2004), and Upper Baby Formation (Clark and Wares, 2004, Figure 33, page 55; Clark, 2019). In this compilation, the upper member of the Baby Formation is referred to as the Upper Baby member.
Authors who have contributed to the description of the various units of the Upper Baby member include Bergeron (1953, 1955 and 1956), Sauvé (1956 and 1959), Bérard (1959 and 1965), Hashimoto (1964), Fahrig (1965), Clark (1978, 1979, 1980 and 1988), Bélanger (1982) and Goulet (1995). The Upper Baby member may be partly equivalent to the former (now abandoned) Larch River Formation (Clark and Wares, 2004).
Description
The Upper Baby member represents an allochthonous volcano-sedimentary unit located in the lower part of the Koksoak Group (Clark and Wares, 2004). It consists of alternating mudstone, siltstone and sandstone having a rhythmic structure, as well as quartzitic or feldspathic sandstone (turbidites) and, in the upper part, local occurrences of iron-bearing rocks. The composition of the Upper Baby member is generally identical to that of the Lower Baby member. It differs from the latter only in its stratigraphic position relative to iron-bearing rocks of the Middle Baby member and volcanic rocks of the Hellancourt Formation (Sauvé and Bergeron, 1965; Wares and Goutier, 1990). The Upper Baby member comprises six informal units:
- Mudstone, siltstone, fine sandstone, grey or black slate, phyllite and micaceous schist locally interbedded with quartzitic sandstone (pPbb[s]1);
- Quartzitic sandstone interbedded with mudstone, siltstone and conglomerate (pPbb[s]2);
- Basalt and tuff (pPbb[s]3);
- Micaceous schist locally interbedded with quartzite (pPbb[s]5);
- Dolomite (pPbb[s]6);
- Graphitic, locally pyritic black mudstone or slate (pPbb[s]7).
Rocks of the Upper Baby member are metamorphosed to the greenschist facies (Dimroth and Dressler, 1978; Fraser et al., 1978). The sedimentary rocks of the Upper Baby member were deposited in a marine basin east of the Ferriman Group platform sequence, which was progressively deepening from west to east (Clark, 1988; Clark and Wares, 2004).
The Upper Baby member contains polymetallic Cu-Zn-Co-Ag-Au mineralization hosted in rhythmites as well as in Algoma-type iron formations located in flyschoid sediments near the top of the unit (Wares et al., 1988; Barrett et al., 1988; Clark and Wares, 2004; Wares and Goutier, unpublished report). It should be noted that iron formations of the Baby Formation were previously grouped within the Sokoman Formation in the Lake Superior type (Gross, 1995; Clark and Wares, 2004). Cu-Ni ± Co ± PGE mineralization is hosted in glomerophyric gabbro sills of the Gerido Intrusive Suite, emplaced in sulphide-bearing metasedimentary rocks (iron formations) of the Upper Baby member in the northern part of the orogen (Wares and Goutier, 1989 and 1990; Clark and Wares, 2004).
Upper Baby member, Undivided (pPbb[s]): Mudstone, Sandstone, Basalt, Sulphide Facies Iron Formation
This undivided unit consists of a variety of lithologies including mudstone, sandstone, basalt and sulphide facies iron formations (Clark, 1978 and 1980). Iron-bearing rocks include graphitic and sulphidic mudstones, chloritic mudstones, sulphide turbidites, massive and laminated pyrite beds and iron formations (silicate and sulphide facies) (Clark and Wares, 2004).
Upper Baby member 1 (pPbb[s]1): Mudstone, Siltstone, Fine Sandstone, Grey or Black Slate, Phyllite, Micaceous Schist; Locally Interbedded Quartzitic Sandstone
Unit pPbb(s)1 is the largest unit of the Upper Baby member in the northern Labrador Trough. It forms 10 to 60 m-thick layers inserted between or in contact with gabbro sills (Gerido Intrusive Suite). The unit consists of mudstone, siltstone, fine sandstone, grey or black slate, phyllite and micaceous schist. These rocks are usually grey, greenish grey or green in fresh exposure, slightly less dark in altered surface, finely stratified (1-5 cm) and laminated. The different lithologies are generally interbedded and display a rhythmic structure (rhythmites). Interbedded quartzitic sandstone is observed locally (Sauvé, 1956 and 1959; Hashimoto, 1964; Bérard, 1965; Sauvé and Bergeron, 1965; Clark, 1978, 1979, 1980, 1988; Bélanger, 1982; Goulet, 1995). The most common sedimentary structures consist of ripples, small-scale (1 cm) cross bedding and syn-sedimentary folding. In places, normal sorting is observed in sandstone beds. Near the top of the unit, grey or black slate, commonly pyritic, is observed in places (Sauvé 1959; Bérard, 1965; Sauvé and Bergeron, 1965). Moreover, in the Lac Gerido area, the upper part of the Upper Baby member locally contains black shale (Sauvé and Bergeron, 1965).
In the Hérodier Lake and Koksoak River areas, rocks of unit pPbb(s)1 have a coarser grain size towards the top and gradually change to quartzitic sandstone of unit pPbb(s)2 (Clark, 1980).
Upper Baby member 2 (pPbb[s]2): Quartzitic Sandstone, Interbedded Mudstone, Siltstone and Conglomerate
Unit pPbb(s)2 consists of quartzitic sandstone and interbedded mudstone, siltstone and conglomerate (Clark, 1978, 1980). In the Hérodier Lake and Koksoak River areas, it is estimated to be 15 to 30 m thick. Quartzitic sandstone occurs in beds 0.1 to 3 m thick, increasing in thickness towards the top. It is generally grey in altered surface, locally grey to greenish grey or white, and coarse to very coarse grained (1-3 mm). Cross bedding and sorting are observed in places. Mudstone interstratifications are usually 0.3 m to several metres thick. The proportion of mudstone increases towards the top of the unit where the bed thickness locally reaches 12 m. The thickness of grey siltstone beds varies from 0.3 to 1.2 m. Sorting and cross bedding are reported locally. Conglomerate is observed locally in unit pPbb(s)2 as 0.3 to 12 m-thick beds interbedded with quartzitic sandstone. It is generally composed of rounded quartz pebbles (1 to 5 cm in diameter) in a quartzitic sandstone matrix. More rarely, it contains mudstone fragments as angular sheets up to ~1.5 m long (Clark, 1978, p. 18).
Further north, in the Larochelle Lake area (sheet 24K12), unit pPbb(s)2 consists mainly of quartzitic sandstone. The latter usually occurs in beds a few metres to ~75 m thick. It is generally quite pure, but may locally contain significant amounts of chlorite and muscovite (Sauvé, 1959).
Upper Baby member 3 (pPbb[s]3): Basalt, Tuff
Unit pPbb(s)3 consists mainly of basalt flows associated with gabbros and minor layers of mafic tuff (Clark, 1978; Bélanger, 1982). These rocks are green to dark green or grey to greenish grey, fine grained and have a brownish alteration patina. In the area west of Hérodier Lake, basalt flows are massive and estimated to be 30 m thick. They are interstratified with pillow flows (Clark, 1978). Basalt is locally porphyritic and contains centimetric plagioclase phenocrysts (Bélanger, 1982). In places, basalt changes to a medium-grained gabbroic rock. It is, however, difficult to distinguish from microgabbros.
Upper Baby member 5 (pPbb[s]5): Micaceous Schist; Locally Interbedded Quartzite
Unit pPbb(s)5 consists mainly of micaceous schists with some minor quartzite intercalations visible locally (Berard, 1959; Clark, 1978). This unit generally overlies iron-bearing rocks of the Middle Baby member. In the Feuilles Lake area (sheets 24K12 and 24K13), its thickness is estimated at 300 m SE of Raymond Lake (Bérard, 1959). A few occurrences of mica schist have been mapped in the Hérodier Lake area (Clark, 1978). Micaceous schist is generally black and composed of biotite, muscovite and chlorite in variable amounts. Quartzite beds range in thickness from a few metres to ~75 m. Quartzite is generally quite pure and contains minor amounts of biotite. In places, it may contain significant amounts of chlorite and muscovite.
Upper Baby member 6 (pPbb[s]6): Dolomite
Unit pPbb(s)6 is located in the Jogues Lake area. It consists of massive dolomite, buff-coloured in altered patina, cut by numerous quartz veins. According to Hashimoto (1964), dolomite is interbedded with phyllite and slate.
Upper Baby member 7 (pPbb[s]7): Graphitic, Locally Pyritic Black Mudstone or Slate
Unit pPbb(s)7 consists of dark grey to black, graphitic mudstone or slate. In the Hérodier Lake and Koksoak River areas, this unit is overlying iron-bearing rocks of the Middle Baby Member and forms ~5-10 m thick layers within basaltic-gabbroic sequences. Locally, the rock is rusty at the surface due to the presence of pyrite. The latter usually occurs as thin laminae parallel to bedding (Clark, 1978 and 1980).
Thickness and distribution
The Upper Baby member belongs mainly to the Gerido Lithotectonic Zone as defined by Clark and Wares (2004). It extends for over 200 km from Feuilles Lake (sheet 24K13) to Jogues Lake (sheet 24F02). Its thickness is estimated to be between 450 m and 700 m in the area NW of the Koksoak River (Sauvé and Bergeron, 1965; Clark, 1979; Goulet, 1995). In the Holannah and Crochet lakes areas (sheet 24K04), Wares and Goutier (1989) estimated a minimum apparent thickness >500 m. Further east, in the area NW of Thévenet Lake, the minimum apparent thickness of the Upper Baby member is estimated at 800 m. According to Wares and Goutier (1990), this thickness may be less, as the estimate does not take into account the presence of gabbro sills, thrust faults and folding in this area.
Dating
None.
Stratigraphic Relationship(s)
The Upper Baby member is Paleoproterozoic in age. It belongs to the second cycle of Labrador Trough sedimentation dated 1.88 to 1.87 Ga (Clark and Wares, 2004). The Upper Baby member correlates with the Menihek Formation, overlying the Sokoman Formation (1880 ±2 Ma; Chevé and Machado, 1988), and is therefore younger than the Sokoman Formation and older than 1874 ±3 Ma, the estimated age of the upper part of the Hellancourt Formation (Machado et al., 1997). The Upper Baby member conformably overlies iron-bearing rocks of the Middle Baby member (Clark, 1988; Goulet, 1995). According to Clark (1988), the contact between the two members is sharp. In the area south of Feuilles Lake, the Upper Baby member is structurally overlain by volcanic rocks of the Hellancourt Formation (Clark, 1988; Goulet, 1995). The Upper Baby member is equivalent to the Menihek Formation (Ferriman Group) and the Thompson Lake Formation (Doublet Group) (Fournier, 1982; Clark, 1988; Goulet, 1995; Clark and Wares, 2004).
Paleontology
Does not apply.
References
Publications Available Through SIGÉOM Examine
BELANGER, M. 1982. REGION DU LAC FAUJAS, NOUVEAU-QUEBEC. MRN. DP-82-06, 1 plan.
BERARD, J. 1959. PRELIMINARY REPORT ON LEAF LAKE AREA, NEW QUEBEC. MRN. RP 384(A), 8 pages and 1 plan.
BERARD, J. 1959. RAPPORT PRELIMINAIRE SUR LA REGION DU LAC AUX FEUILLES, NOUVEAU-QUEBEC. MRN. RP 384, 10 pages and 1 plan.
BERARD, J. 1965. BERARD LAKE AREA, NEW QUEBEC. MRN. RG 111(A), 148 pages and 2 plans.
BERARD, J. 1965. REGION DU LAC BERARD, NOUVEAU-QUEBEC. MRN. RG 111, 175 pages and 2 plans.
BERGERON, R. 1953. PRELIMINARY REPORT ON GERIDO LAKE AREA, NEW QUEBEC. MRN. RP 291(A), 8 pages and 1 plan.
BERGERON, R. 1953. RAPPORT PRELIMINAIRE SUR LA REGION DU LAC GERIDO, NOUVEAU-QUEBEC. MRN. RP 291, 10 pages and 1 plan.
BERGERON, R. 1955. PRELIMINARY REPORT ON THEVENET LAKE AREA (WEST PART), NEW QUEBEC. MRN. RP 311(A), 6 pages and 1 plan.
BERGERON, R. 1955. RAPPORT PRELIMINAIRE SUR LA REGION DU LAC THEVENET (PARTIE OUEST), NOUVEAU-QUEBEC. MRN. RP 311, 8 pages and 1 plan.
BERGERON, R. 1956. PRELIMINARY REPORT ON HARVENG LAKE AREA, (WEST HALF), NEW QUEBEC. MRN. RP 320(A), 6 pages and1 plan.
BERGERON, R. 1956. RAPPORT PRELIMINAIRE SUR LA REGION DU LAC HARVENG (MOITIE OUEST), NOUVEAU-QUEBEC. MRN. RP 320, 9 pages and 1 plan.
CLARK, T. 1978. REGION DU LAC HERODIER ( NOUVEAU-QUEBEC) – RAPPORT PRELIMINAIRE. MRN. DPV 568, 48 pages and 2 plans.
CLARK, T. 1979. REGION DU LAC NAPIER (NOUVEAU-QUEBEC) – RAPPORT PRELIMINAIRE. MRN. DPV 663, 28 pages and 1 plan.
CLARK, T. 1980. REGION DE LA RIVIERE KOKSOAK (NOUVEAU-QUEBEC) – RAPPORT PRELIMINAIRE. MRN. DPV 781, 24 pages and 1 plan.
CLARK, T. 1987. STRATIGRAPHIE, PETROGRAPHIE ET PETROCHIMIE DE LA FORMATION DE FER DE BABY DANS LA REGION DU LAC HERODIER (FOSSE DU LABRADOR). MRN. ET 87-13, 44 pages.
CLARK, T., 2019. Compilation géologique, lac Harveng. MERN; CG-2019-01, 1 plan.
CLARK, T., WARES, R. 2004. SYNTHESE LITHOTECTONIQUE ET METALLOGENIQUE DE L’OROGENE DU NOUVEAU-QUEBEC (FOSSE DU LABRADOR). MRNFP. MM 2004-01, 182 pages and 1 plan.
FOURNIER, D. 1982. GITES DU CU-ZN ET CU-NI DANS LE PARTIE CENTRALE DE LA FOSSE DU LABRADOR. MRN. DPV 929, 69 pages and 6 plans.
GOULET, N. 1995. ETUDE STRUCTURALE, STRATIGRAPHIQUE ET GEOCHRONOLOGIQUE DE LA PARTIE NORD DE LA FOSSE DU LABRADOR. MRN. MB 95-36, 41 pages and 1 plan.
HASHIMOTO, T. 1964. GEOLOGIE DE LA REGION DU LAC JOGUES, TERRITOIRE DU NOUVEAU-QUEBEC. MRN. RP 524, 13 pages and 1 plan.
SAUVE, P. 1956. PRELIMINARY REPORT ON DE FRENEUSE LAKE AREA (WEST HALF), NEW QUEBEC. MRN. RP 332(A), 7 pages and 1 plan.
SAUVE, P. 1956. RAPPORT PRELIMINAIRE SUR LA REGION DU LAC DE FRENEUSE (MOITIE OUEST), NOUVEAU-QUEBEC. MRN. RP 332, 10 pages and 1 plan.
SAUVE, P. 1959. PRELIMINARY REPORT ON LEAF BAY AREA, NEW QUEBEC. MRN. RP 399(A), 11 pages et 1 plan.
SAUVE, P. 1959. RAPPORT PRELIMINAIRE SUR LA REGION DE LA BAIE AUX FEUILLES, NOUVEAU-QUEBEC. MRN. RP 399, 15 pages and 1 plan.
SAUVE, P., BERGERON, R., 1965. REGION DES LACS GERIDO ET THEVENET, NOUVEAU-QUEBEC. MRN; RG 104, 141 pages, 3 plans.
SAUVE, P., BERGERON, R., 1965. GERIDO LAKE – THEVENET LAKE AREA, NEW QUEBEC. MRN; RG 104(A), 131 pages, 3 plans.
WARES, R., BERGER, J., ST-SEYMOUR, K. 1988. SYNTHESE METALLOGENIQUE DES INDICES DE SULFURES AU NORD DU 57e PARALLELE (ETAPE 1) – FOSSE DU LABRADOR -. I R E M. MB 88-05, 202 pages and 1 plan.
WARES, R., GOUTIER, J. 1989. METALLOGENIE DES INDICES DE SULFURES AU NORD DU 57e PARALLELE (ETAPE II) – FOSSE DU LABRADOR -. MRN. MB 89-38, 122 pages and 1 plan.
WARES, R., GOUTIER, J. 1990. SYNTHESE METALLOGENIQUE DES INDICES DE SULFURES AU NORD DU 57e PARALLELE – FOSSE DU LABRADOR – RAPPORT INTERIMAIRE – ETAPE III. IREM-MERI. MB 90-25, 104 pages and 2 plans.
Other Publications
BARRETT, T.J., WARES, R.P., FOX, J.S. 1988. Two-stage hydrothermal formation of a Lower Proterozoic sediment-hosted massive sulfide deposit, northern Labrador Trough, Quebec. Canadian Mineralogist; volume 26, pages 871-888.
CHEVÉ, S.R., MACHADO, N. 1988. Reinvestigation of the Castignon Lake carbonatite complex, Labrador Trough, New Québec. Joint Annual Meeting of the Geological Association of Canada and the Mineralogical Association of Canada, St. John’s, Newfoundland; Program with Abstracts, volume 13, pages 20.
DIMROTH, E., DRESSLER, B. 1978. Metamorphism of the Labrador Trough. In: Metamorphism in the Canadian Shield. Geological Survey of Canada; Paper 78-10, pages 215-236. https://doi.org/10.4095/104534
FAHRIG, W.F. 1965. Geology, Lac Herodier, Québec. Geological Survey of Canada; Map 1146A. https://doi.org/10.4095/107520
FRASER, J.A., HEYWOOD, W.W., MAZURSKI, M.A. 1978. Carte métamorphique du Bouclier Canadien. Geological Survey of Canada; Map 1475A. https://doi.org/10.4095/133909
GROSS, G.A. 1995. Lake Superior-type iron formation. In Geology of Canadian mineral deposit types (Eckstrand, O.R., Sinclair, W.D. and Thorpe, R.I., editors). Geological Survey of Canada; Geology of Canada, number 8, pages. 54-66.
MACHADO, N., CLARK, T., DAVID, J., GOULET, N. 1997. U-Pb ages for magmatism and deformation in the New Quebec Orogen. Canadian Journal of Earth Sciences; volume 34, pages 716-723. https://doi.org/10.1139/e17-058
Suggested Citation
Ministère de l’Énergie et des Ressources naturelles (MERN). Upper Baby member. Quebec Stratigraphic Lexicon. https://gq.mines.gouv.qc.ca/lexique-stratigraphique/province-de-churchill/membre-de-baby-superieur_en [accessed on Day Month Year].
Contributors
|
First publication |
Charles St-Hilaire, GIT, M.Sc. charles.st-hilaire@mern.gouv.qc.ca; Thomas Clark, P. Geo., Ph.D. (redaction) Mehdi A. Guemache, P. Geo., Ph.D. (coordination); Claude Dion, Eng., M.Sc. (critical review); Simon Auclair, P. Geo., M.Sc. (editing); Céline Dupuis, P. Geo., Ph.D. (English version); André Tremblay (HTML editing). |