Late Quaternary paleoenvironments of the Morley Flats and Kananaskis Valley of southwestern Alberta

Abstract

A 3.1 m section of limnic sediment and peat from a bog on the Morley Flats and a 2.8 m section of limnic sediment from Wedge Lake in the Kananaskis Valley have yielded the first comprehensive late Quaternary biostratigraphic record from south-western Alberta. Both sections were analyzed for subfossil pollen, molluscs, and several sedimentary indices. Two distinct pollen zones were recognised. The basal zone, characterized by high relative abundancy of Artemisia–Salix–Juniperus, suggests that the Morley Flats were dominated by a sparse vegetation composed of aggressive pioneer species following deglaciation until prior to approximately 10 000 BP. Similarly, the mollusc fauna from this zone is dominated by northern ranging species. The second zone is typified by a predominance of Pinus and Picea. This reflects the expansion of coniferous forest into the region. Both the relative abundance of southern ranging mollusc species and the total carbonate concentration in the sediment increase in this zone. The vegetation of the region has remained generally stable since at least 9395 BP. However, increases in the abundance of Pinus relative to Picea and Abies in the mid-Holocene suggest that this period experienced an increase in fire frequency, possibly generated by climatic amelioration.