- © The Society of Canadian Petroleum Geologists
The Montney Formation is a Lower Triassic, siliciclastic-dominant unit in the subsurface of west-central Alberta and northeast British Columbia (Fig. 1⇓). Throughout its area of occurrence it is underlain unconformably by either Permian or Carboniferous strata and overlain abruptly, and probably unconformably, by the Middle Triassic Doig Formation. Towards its eastern outcrop limit Jurassic strata truncate successively older Montney beds.
Although strata equivalent to the Montney in outcrop have been subdivided into a number of named members (see Davies et al., 1997, for a brief review), generally it has proven difficult to correlate the outcropping units into the subsurface. Only Barss et al.(1964) suggested such a correlation when they correlated the uppermost beds of the Montney Formation, which in the western parts of the basin have a distinct log signature, with Manko’s (1960) Black Shale member of the Sulphur Mountain Formation. However, as will be discussed later, this correlation is incorrect. Internal subdivision of the subsurface Montney Formation has only been attempted with any degree of consistency by Davies et al.(1997).
The objective of this paper is to review the lithostratigraphic divisions of previous authors and offer an alternative and regionally consistent subdivision into informal members. The lithostratigraphic scheme presented herein resulted from the author compiling a series of regional cross-sections through the Montney Formation, but due to the size of such cross-sections they cannot be published in the journal format.
Montney strata were formally defined in the subsurface of western Canada by Armitage (1962), in the Texaco NFA Buick Creek 6-26-87-21W6 well of northeast British Columbia, between log depths 5625 ft and 6500 ft (1714.5 and 1981.2 m respectively). In the type section, the Montney rests unconformably on Permian strata and is …