The Cretaceous–Tertiary boundary In the central Alberta Foothills. I: Stratigraphy

Abstract

The Cretaceous–Tertiary boundary in the Rocky Mountain Foothills occurs within a continental sequence carrying economic coal deposits and known as the Coalspur Formation. This formation occurs between the fluvial Brazeau (below) and Paskapoo formations. The exact position of the boundary is located at the base of the lowest coal (Mynheer) within the Coalspur Formation. The initiation of coal deposition in the Coalspur Formation is not a unique event, as it is consistent with the cyclic pattern established within the underlying Brazeau Formation. However, the magnitude and lateral continuity of coal zone development far exceed those found in the underlying formation.The classic shift from a diverse, late Maastrichtian flora (within which angiosperm and especially aquiloid pollen are prominent) to a low-diversity, Early Paleocene flora dominated by gymnosperm pollen and miospores is documented. Deviations from most previously recognized floral events at the Cretaceous–Tertiary boundary include (1) san angiosperm pollen peak immediately above the determined boundary position (formed by two dominant species, Syncolporites minimus and Triporopollenites plektosus) and (2) the extension of the range of species of aquiloid pollen into the Paleocene.