Unit Name: Halfway Formation
Unit Type: Lithostratigraphic
Usage: Currently in use
Age Interval: early Ladinian - Carnian (237 - 216.5 ma)
Age Justification: Fish, pelecypod fragments and crinoids comprise the faunal assemblage.
Province/Territory: Alberta; British Columbia
Originator: Hunt and Radcliffe, 1959.
Peace River area, northwestern Alberta and northeastern British Columbia, (Halfway) Southern Production B-14-1 well, in 1-12-84-23W6M, British Columbia, between 1,524 and 1,569 m (5,000 and 5,148 ft).
The Halfway Formation occurs as a wedge-shaped deposit, thinning eastwardly from 416 m (1356 ft) in the Peace and Pine River areas, southern Deep Basin to zero at the erosional subcrop edge in the subsurface of the Peace River area. Laterally it extends east-west for about 240 km (150 mi).
Grey to light grey, fine- to medium-grained, massive quartz sandstones, in part dolomitic and calcareous, with minor amounts of chert, grey to buff, finely crystalline dolomite and dolomitic siltstones. Locally thin shelled pelecypod coquinas occur. Traces of collophane are found throughout. Sedimentary structures include cross-bedded, coarsening-upward sandstones, leached vugs in the more carbonate lithologies and bioturbation in the shalier sections.
The Halfway disconformably overlies the Doig formation, where the contact is marked by a thin bed of dolomite, quartz and chert 'granule' conglomerate. The formation is conformably overlain by Charlie Lake silts, dolomites and anhydrites. In the west that contact is gradational into anhydritic dolomitic silts and sandstones, while in the east the contact is more abrupt, passing into silty anhydrites and dolomites. Lateral equivalents include the Liard Formation of the northern foothills, the Llama Member of the Sulphur Mountain Formation of the southern Rocky Mountains and foothills and the lowermost beds of McLearn and Kindle's "Grey Beds". At it's erosional subcrop limit to the east the Halfway may be overlain by Jurassic or Cretaceous beds. It is part of the Schooler Creek Group.
Armitage, 1962; A.S.P.G., 1964; Hunt and Ratcliffe, 1959; McLearn and Kindle, 1950; Miall, 1976; Mothersill, 1968; Pelletier, 1961, 1963; Torrie, 1973.
Hunt, Albin Digby and Ratcliffe, James Douglas, 1959. Triassic stratigraphy, Peace River area, Alberta and British Columbia, Canada; The American Association of Petroleum Geologists (AAPG), AAPG Bulletin, vol. 43, no. 3 (March), pp. 563-589.
Source: CSPG Lexicon of Canadian Stratigraphy, Volume 4, western Canada, including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba; D.J. Glass (editor)
Contributor: C. Dawes
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 20 Nov 2009