Unit Name: Bobcaygeon Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Undefined
Usage: Currently in use
Age Interval: Blackriveran - Trentonian (460.9 - 449 ma)
Age Justification: Stratigraphic relations. The age was determined by relating the Bobcaygeon Formation to the Kirkfield, Rockland and Chaumont (Leray) biostratigraphic units (Liberty, 1969).
Province/Territory: Ontario

Originator: Liberty, 1969.

Type Locality:
Type sections include: lower member C1, Cobocong east quarry (Canada Lime Co.; Lot 37, Somerville tp., Victoria co., south of the village of Coboconk and east of No. 35 highway); C2 Silver Lake section (Lot 1, cons. II and III, Galway tp., Peterborough co., 9½ mi. north of Bobcaygeon, and three-quarters mi. east of Bobcaygeon-Kinmount Highway); Middle member, Little Bob quarry (Lot 13, con. XIX, Harvery tp., Peterborough co., immediately south of the town of Bobcaygeon, south side of Little Bob River and a quarter mi. east of No. 6 highway); upper member, Kirkfield quarry (Lots 31-32, con. IX, Eldon tp., Victoria co., 2 mi. northeast of village of Kirkfield) (Liberty, 1969).

The Bobcaygeon Formation has been mapped from east of Pigeon Lake to Christian Island in Georgian Bay (Liberty, 1969).

Locality Data:
Thickness(m): Minimum 9, Maximum 91.

The Bobcaygeon Formation is divided into three members (units C, D, and E). The lower member (C) consists of grey and brownish grey, fine- and medium-grained limestone, and some grey crystalline crinoidal limestone (C1), but encloses thin beds of grey, finely clastic limestone (calcarenite) (C2) in its uppermost few feet. The middle member (D) consists of grey and brown, very fine grained to sublithogenic, sparsely fossiliferous limestone, with some fine-grained limestone in the upper part. The upper member (E) alternates between sulithographic and medium calcarenitic limestone, but also includes some brown lithographic limestone and bluish fine-grained limestone in minor thicknesses (Liberty, 1969).

The Bobcaygeon Formation is part of the Simcoe Group. It lies above the lithographic sediments of the Gull River Formation and below the interbedded limestone and shale of the Verulam Formation (Liberty, 1969). The Formation consists of the Leray, Rockland, and Hull time-rock units. It includes the Rockland and Hull of Kay (1937), and the Coboconk and Kirkfield of Sanford (1961). It includes the Upper Black River and Lower Trenton of Hewitt (1960) (Hewitt, 1971).

Hewitt, D.F., 1960a. The limestone industries of Ontario, Ontario Ministry of Northern Development and Mines Industrial Mineral Circular no. 5, 177 p.
Hewitt, D.F., revised by Hewitt, D.F. and Vos, M.A., 1971. The limestone industries of Ontario, Ontario Division of Mines, Industrial Mineral Report 39, 1972.
Kay, G.M., 1937. Stratigraphy of the Trenton group; Geological Society of America Bulletin (GSA); vol. 48; no. 2 (February 1937); p. 233-302.
Liberty, B.A., 1969. Palaeozoic Geology of the Lake Simcoe Area, Ontario: Geological Survey of Canada, Memoir 355, 201p.
Sanford, B.V. 1961. Subsurface Stratigraphy of Ordovician Rocks in Southwestern Ontario 30, 31, 40, 41 (parts of), Geological Survey of Canada, Paper 60-26.

Source: GSC file of geological names; T.E. Bolton and J. Dougherty (compiler)
Contributor: Michael Pashulka
Entry Reviewed: No
Name Set: Lithostratigraphic Lexicon
LastChange: 24 Jul 2018