Unit Name: Todhunter Member
Unit Type: Lithostratigraphic
Rank: Member
Status: Formal
Usage: Currently in use
Age Interval: Chesterian (333 - 318.1 ma)
Age Justification: The total fauna of the Todhunter includes Spirifer increbescens, Spirifer sp., Composita sp., Archimedes sp. and ?Caninia sp. (see Norris, D.K., 1965, p. 21). The member is of Mississippian (Chesteran) age. It has similar lithology and stratigraphic position to the lower Amsden Formation of south-central Montana.
Province/Territory: Alberta; British Columbia

Originator: Norris, D.K., 1957.

Type Locality:
North side of Beehive Pass, British Columbia, in the Highrock Range, Beehive Mountain map-area; NTS 82J/2E.

In the eastern ranges of the Rocky Mountains, between the Bow and Crowsnest River drainages the Todhunter ranges in thickness from zero to 35 m (115 ft). It is 27 m (89 ft) at the type section in Beehive Pass The unit is best developed in the Highrock Range in the vicinity of Beehive Pass, Alberta and British Columbia. Equivalent strata have not been demonstrated in the Highwood and Livingstone Ranges, Alberta.

Locality Data:
Thickness(m): Minimum 0, Maximum 35, Typical 27.

The Todhunter comprises brightly colored, interbedded siltstones, dolomites and sandstone in gradational contact with light grey and buff weathering dolomites associated with red and green shales of the Etherington Formation.

The Todhunter is lithologically gradational with the Etherington Formation beneath it. Its contact with the overlying Misty Formation is disconformable.

The Todhunter Member, as originally defined was included as the basal unit of the Rocky Mountain Supergroup. Scott (1964a) adopted this usage. However, because of the regional persistence of the overlying sandstones of the Misty Formation, and the genetic association of the Todhunter with underlying beds Norris (1965b) redefined the Todhunter as the upper member of the Etherington Formation in the Highrock Range.

Other Citations:
Norris, 1957, 1965; Stott, 1964.

Norris, D.K., 1957. The Rocky Mountain succession at Beehive Pass, Alberta; J. Alberta Soc. Petrol. Geol., vol. 5, p. 248-254.
Norris, D.K., 1965b. The stratigraphy of the Rocky Mountain Group in the southeastern Cordillera of Canada; Geological Survey of Canada, Bulletin 125.
Scott, D.L., 1964a. Stratigraphy of the lower Rocky Mountain Supergroup in the southern Canadian Rocky Mountains; University of British Columbia, Vancouver, BC, Ph.D. thesis, 271 p.

Source: CSPG Lexicon of Canadian Stratigraphy, Volume 4, western Canada, including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba; D.J. Glass (editor)
Contributor: D.K. Norris
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 11 Mar 2009