The K-T boundary and contiguous strata in western Canada: interactions between paleoenvironments and palynological assemblages

Abstract

A detailed palynological study of samples from 12 localities in western Canada indicates that, through the K-T boundary interval, a series of changes occurred within plant communities and that these changes are overprinted by variations related to latitudinal and climatic differences. Distinctive palynofloras are present below the boundary, in the boundary claystone and above the boundary. Time must be represented in the change from one palynoflora to another, and therefore between their host sediments, as each palynoflora represents a reproductively mature plant community. Boundary claystone floras are closely linked to those of the latest Maastrichtian and so predate the extinction event. Following the extinctions, opportunistic floras characterized by one or two dominant species were established. The dominant opportunistic taxa vary geographically and generally reflect abundances established in latest Maastrichtian floras. There is strong evidence to suggest that the K-T event coincides with a period of increased wetness over most of western North America, which locally results in organic-rich sediments underlying the boundary claystone. This suggests that changes noted at and contiguous to the boundary were not solely owing to a single catastrophic event but, at least in part, resulted from a longer term alteration in the complex series of factors controlling plant community development.