Stratigraphy and Correlation of Jurassic in Canadian Rocky Mountains and Alberta Foothills: ABSTRACT

Abstract

The Jurassic of the Canadian Rocky Mountains and foothills comprising the Fernie group and the lower part of the Kootenay and Nikanassin formations is subdivided on a paleontological basis into a number of units which correspond to zones and stages of the Northwest European standard section. The following stages are shown to be present by their index fossils--part of the Sinemurian, the Toarcian, the middle Bajocian, the lower Callovian, at least part of the Oxfordian and Kimmeridgian, and the upper Portlandian. A most significant feature of the Fernie group is its incompleteness, only 11 or 12 of the 59 Northwest European ammonite zones being proved to be present. Ammonite zones belonging to the Hettangian, parts of the Sinemurian, and the Pliensbachian are definitely ab ent. Stratal equivalents of the lower and upper Bajocian, Bathonian, upper Callovian and parts of the Oxfordian, Kimmeridgian, and Portlandian are not indicated by index megafossils and may be entirely absent or represented by sediments without megafauna. A variety of different facies is developed which can only be correlated by index fossils common to different facies districts. Some of the most prominent facies units are the Nordegg member, the Paper or Poker Chip shale of the lower Fernie, the middle Bajocian Rock Creek member, the Callovian Corbula munda beds and Gryphaea bed which are equivalent to the Grey beds, the Oxfordian Green beds, and the Passage beds which are mainly of Kimmeridgian age. Correlations of the Rocky Mountains and foothills Jurassic with the Jurassic deposits in British Columbia, Yukon, Prince Patrick Island, and Manitoba are established. Absence of index megafossils in the Jurassic of the Alberta, Saskatchewan, and Manitoba plains renders correlation of these areas with the Fernie group difficult. A tentative attempt has been made to correlate these areas on the basis of existing literature and through the co-operative efforts of the Jurassic symposium committee. Interpretation of the data obtained from field studies has made possible a synthesis of the present Canadian Rocky Mountains and foothills region during Jurassic time, a region which is considered as a non-geosynclinal border zone between the Cordilleran geosyncline in the west and the land Laur ntia in the east.