Notes on changing paleoenvironments across the Cretaceous-Tertiary boundary (Scollard Formation) in Red Deer River valley of southern Alberta

The Scollard Formation of southern Alberta comprises alluvial plain deposits that straddle the Cretaceous-Tertiary boundary. Paleochannels in the Scollard Formation display an apparent shift from low sinuosity (straight) to higher sinuosity (meandering) channel forms across the boundary, coincident with the onset of deposition of peats and organic-rich muds. A superb example of this transition is preserved at Knudsen's Coulee and is herein documented. Although a tectonic influence cannot be ruled out, we propose that the principal cause of the transition is climatic, the result of an increase in wetness, locally rising water tables, and possible changes in discharge characteristics and in-channel sediment load. On the basis of parsimony and the absence of evidence to the contrary, we reject the suggestion that the Cannonball transgression directly influenced changes in the depositional style of the Scollard Formation.