Type Locality:

Globensky's (1986) type-section for the Cairnsdie Formation is at Schink quarry (Salad Hersi and Lavoie, 2000).

Distribution:

Southwestern Quebec. Subsurface data from previous work shows that the formation is about 44 m (145 feet thick) (Clark, 1972, p. 25) (Salad Hersi and Lavoie, 2000).

Locality Data:

Thickness(m): Typical 44.

Lithology:

The Cairnside Formation consists of a lower unit thickly bedded to medium-bedded, coarse-grained, burrowed, white quartz arenite and an upper unit characterized by beds similar to those of the lower unit with thinly bedded to lenticular, medium-grey, coarse-grained dolomitic sandstone. The lower unit of the formation consists of thickly bedded to medium-bedded, coarse-grained, clean, creamy white quartz arenite. It weathers to light pale, yellowish grey to white. Sedimentary structures and biological elements in the unit include tabular crossbedding, planar bedding, unidirectional (current) ripples, vertical (Skolithos sp.) burrows, ?Climatichnites sp. trace fossils, desiccation cracks, scour surfaces, and normal gradation. Trough crossbedding is also present but not common. Some beds show pervasive biogenic reworking of the sediment, producing a densely packed burrow network similar to the Ophimorpha ichnofabric of Bottjer and Droser (1994). In the lower part of the unit in the south, there is a brecciated zone due to soft-sediment deformation. The breccia clasts are lithologically similar to the clean quartz arenite of the Cairnside sandstone. The upper unit of the Cairnside Formation is separated from the lower unit by an erosional surface. The upper unit consists of two interbedded lithofacies, 1) quartz arenite lithofacies (Lf-1), which is similar in every sense (grain size, sedimentary structures, colour, etc.) to that of the lower unit and overwhelmingly dominates the succession; and 2) dolomitic sandstone lithofacies (Lf-2), which occurs as thin to medium beds and lenses interbedded with lithofacies Lf-2. Lithofacies Lf-2 also exists as granule- to cobble-size rip-up clasts incorporated with lithofacies Lf-1. Load structures, including flame (dolomitic sandstone injected into the overlying quartz arenite bed) and ball-and-pillow (discrete, rounded lenses of lithofacies Lf-2 separated by Lf-1) structures, are also locally well developed. Lithofacies Lf-2 is not laterally continuous, and appears to be absent in sections north of Montréal. In this case, the two units of the formation are indistinguishable and the whole formation is represented by lithofacies Lf-1 (Salad Hersi and Lavoie, 2000).

Paleo Environment:

marine, shallow

Relationship:

The Cairnside Formation of southwestern Quebec is equivalent to the Nepean Formation of southeastern Ontario and is considered to be approximately correlative with the Strites Pond Formation (Salad Hersi et al., 2002). It is correlative with the Cairnside Member of Clark (1966, 1972) and Cairnsdie Formation of Globensky (1982). The contact between the Covey Hill and overlying Cairnside formations (Potsdam Group, southwestern Quebec) is exposed at the Ducharme quarry near Covey Hill village. The contact separates the lower arkosic sandstone (Covey Hill Formation) characterized by interbedded lithofacies of thickly bedded, light-grey arkose, and medium grey, intensely trough crossbedded arkose on one side, from the overlying tickly bedded, well burrowed, white, clean quartz arenite (Cairnside Formation on the other side). The upper contact of the Cairnside Formation is placed at the top of the highest white, dolomite-free quartz arenite bed above which the quartz arenite lithofacies (typical for the Cairnside Formation) does not occur or is extremely subordinate relative to the dolomitic sandstone and sandy to pure dolostone of the overlying Theresa Formation (lower Beekmantown Group) (Salad Hersi and Lavoie, 2000).

History:

The Potsdam Group as defined by Clark (1966, 1972) consisted of the Covey Hill and Châteauguay formations with further subdivisons into members. Globensky (1981) also followed Clark's (1966, 1972a) subdivisons, but he later (Globensky, 1982) raised the Cairnside and Theresa members to formation ranks (i.e. Cairnside and Theresa formations, respectively). Based on fossil evidence, Globensky (1982) inferred an Ordovician age for the Thersea Formation and put it into the overlying Ordovician Beekmantown Group, whereas the Cairnside Formation remained in the upper part of the Potsdam Group (Salad Hersi and Lavoie, 2000).

References:

Bottjer, D.J. and Droser, M., 1994. The history of Phanerozoic bioturbation; in, The Paleobiology of the trace fossils, (ed.) S.K. Donovan; John Hopkins University Press, Baltimore, Maryland, p. 155-176.

Clark, T.H., 1966. Châteauguay Area, Québec Department of Natural Resources, Geological Report 122, 63 p.

Clark, T.H., 1972. Montreal Area. Ministère des richesses naturelles du Québec, Geological Report, 152, 244p.

Globensky, Y., 1981. Région de Huntingdon; Gouvernement du Québec, Ministère de l'Energie et des Ressources, Rapport Geologique-198, 53 p.

Globensky, Y., 1982. Région de Vaudreuil; Gouvernement du Québec, Ministère de l'Energie et des Ressources, Rapport Géologique-199, 59 p.

Globensky, Y., 1986. Géologie de la région de Saint-Chrysostome et de Lachine (sud); Gouvernement du Québec, Ministère de l'Energie et des Ressources, MM 84-02, 167 p.

Nowlan, G., 2001. Report on thirteen samples from Cambrian and Ordovician strata of the Beekmantown and Philipsburg groups of southwestern Québec. Geological Survey of Canada, Paleontological report 008-GSN-2001, 11 p.

Salad Hersi, O. and Lavoie, D., 2000. Lithostratigraphic revision of the Upper Cambrian Cairnside Formation, upper Potsdam Group, southwestern Quebec; Geological Survey of Canada, Current Research 2000-D4, 8 p. (online; http://www.nrcan.gc.ca/gsc/bookstore).

Salad Hersi, O., Lavoie, D., Hilowle Mohamed, A, and Nowlan, G.S., 2002. Subaerial unconformity at the Postdam - Beekmantown contact in the Quebec reentrant: regional significance for the Laurentian continental margin history; Bulletin of Canadian Petroleum Geology; v. 50; no. 3; p. 419-440.