ABSTRACT

The Upper Cretaceous deltaic and fluvial strata lying between the marine Bearpaw and nonmarine Paskapoo Formations along the eastern side of the Alberta Syncline have been known, for many years, as the Edmonton Formation. Several subdivisions of these strata have been made based on lithologic differences in the exposure along Red Deer River valley. Owing, however, to the interlensed nature of the beds and lack of widespread marker zones, these divisions are useful for local correlation only.

The Whitemud and Battle units within the Edmonton succession have been correlated with the Whitemud and Battle Formations of southeastern Alberta. Together the two units are easily recognized in outcrop and form a marker zone for field mapping; the Battle Formation is readily distinguished also on electric logs of drilled wells and is, therefore, an excellent datum for subsurface correlation. Furthermore, the Kneehills tuff bed within the Battle unit is a time marker. Field work has shown that the lithology of these units is similar throughout the southern Plains of Alberta and, together, they are the only reliable lithologic marker above the marine Bearpaw Formation.

Paleontology, particularly the vertebrate dinosaurian fauna, lends support to a division of the strata above and below the Whitemud and Battle units.

For these reasons the Whitemud and Battle units have been given formational status and the name Horseshoe Canyon Formation is proposed for the nonmarine strata between the Bearpaw and Whitemud Formations. The three formations; Horseshoe Canyon, Whitemud, and Battle are considered to comprise the Edmonton Group.

Owing to the difficulty in defining the rather obscure boundary between Upper Cretaceous strata above the Battle and the overlying Paskapoo Formation it is considered preferable to include those beds, of Lance age, in the Paskapoo Formation. Such a revision results in an upper and a lower boundary for the Edmonton Group that are easily recognized both in outcrop and on mechanical logs of drilled wells.