Evidence for an unconformity at the Scollard–Battle contact, Upper Cretaceous strata, Alberta

Abstract

The Scollard Formation is the uppermost division of the Edmonton Group in the Red Deer River valley of central Alberta. It dates from the close of Cretaceous and the beginning of Tertiary time. It rests on a very distinctive clay sequence consisting in descending order of the Battle and Whitemud formations, which overlie in turn the Horseshoe Canyon Formation, the lowest division of the Edmonton Group. Near the top of the Battle Formation is a distinctive and widespread bed of volcanic origin (Kneehills Tuff). The contact of the Battle clay above this bed with the Scollard Formation varies in level within single exposures. A widespread coal seam (Ardley or No. 14) divides the Scollard Formation into lower and upper members. The thickness of the lower member decreases markedly from south to north, as does the level of the highest recognized dinosaur remains. There is a marked contrast between the dinosaur fauna of the lower Scollard Member and that of the Horseshoe Canyon Formation. A similar break has been observed in the floral succession. These physical and biological discordances at the Scollard–Battle contact are taken to indicate an interval of non-deposition, with or without erosion. Evidence for an analogous break occurs in southwestern and southeastern Alberta and in southern Saskatchewan.