Isometric Panel Diagram—Jurassic System

Abstract Representative surface and subsurface sections were selected from the author’s Jurassic study areas and correlated into a regional isometric panel diagram (Plate I, in pocket). Lateral correlation from one area to another was accomplished by means of committee study groups to arrive at an agreement between authors. The committee was able to summarize the correlations for the Williston basin and southern Alberta basin as shown in Table I. Correlation from the Williston and southern Alberta basins into the foothills belt and northern Alberta basin requires additional subsurface control. Three major stratigraphic divisions of the Jurassic in this area may be conveniently summarized into corresponding Upper, Middle, and Lower Series. The Upper Series includes Kootenay-Nikanassin sands and the underlying “Passage beds” and “Green beds” (Swift) of the uppermost Fernie group. Belemnite horizons are common in the latter two units. The top of the Middle Series is represented by a significant, highly fossiliferous, impure limestone or hard calcareous shale of the “Grey beds.” This is designated as the Gryphaea impressimarginata and Corbula munda beds of Frebold (1957) (Rierdon). The base of the unit in the vicinity of Blairmore, Alberta, contains a bioclastic limestone, the Lille member (Piper), underlying the Rock Creek member. The Lower Series of the Jurassic includes the remaining lowermost Fernie group. The most distinctive lithology is the dark-gray to black phosphatic shale and phosphate nodules, associated in part with chert as in the Nordegg member. The possible equivalent sedimentary interval of this Lower Series in the Williston basin province