Microfloral Diagnosis of the Cretaceous-Tertiary Boundary, Central Alberta

Four stratigraphic sections in central Alberta adjacent to the contact between the Edmonton and Paskapoo Formations of Late Cretaceous and Tertiary ages were sampled for palynological study. A total of 36 genera and 58 species of microspores and pollen, and 2 genera and 14 species of megaspores useful for evaluating the osition of the Cretaceous-Tertiary boundary in central Alberta are described and figured. A new approach to classification, based mainly on details of wall stratification, is used in discriminating among eight new species of Azolla.

Three microfloral 'zones' defined mainly by the distribution of vertically restricted species have been established in the studied sections. Many of these species have been described previously from equivalent strata in South Dakota, Montana, and New Mexico. The lower microfloral 'zone' encompasses beds a short distance above and below he 'mauve shale' and Kneehills Member of the Edmonton Formation and contains a microflora of Maestrichtian age. The middle microfloral 'zone' coincides with the uppermost beds of the Edmonton Formation (upper coaly interval), containing predominantly elements of the lower flora together with a few index species of Paleocene age. The upper microfloral zone spans the lower part of Paskapoo Formation and contains numerous index species of Paleocene or younger age. The distribution of index species in the three microfloral 'zones' and the transitional nature of the flora in the middle 'zone' suggest that the Cretaceous-Tertiary boundary probably lies within the uppermost beds of the Edmonton Formation (upper coaly interval).