The glaciation of the Cypress Hills of Alberta and Saskatchewan and its regional implications

Abstract

Understanding the deglaciation sequence of the Cypress Hills and the surrounding area permits a deeper understanding of the style and chronology of deglaciation in southeast Alberta and southwest Saskatchewan. This paper revises previously published chronologies. Five deglaciation events, the Underdahl Advance, Middle Creek Advance, Altawan Advance, Pakowki Advance, and the Etzikom Advance, have been recognized in the study area. Of these, the Middle Creek and Altawan Advances are newly recognized. The Late Wisconsinan ice (Underdahl Advance) was the most extensive ice to affect the Cypress Hills area; it terminated in Montana. Erratics distributed on the flanks of the Cypress Hills, beyond this ice limit, are interpreted to reflect ice rafting across ice contact proglacial lakes. The erratics are not remnants of older more extensive ice advances as previously thought. The revised deglaciation sequence also indicates that the Late Wisconsinan ice west of the Cypress Hills was more active and was perhaps subject to repeated intervals of surging while the East Ice Lobe, north and east of the Cypress Hills was much more stable. It is possible that the West Lobe was not coupled to the ice north and east of the Cypress Hills and that the West Ice Lobe flowed from an ice divide in the central part of the Northwest Territories. The East Lobe flowed from a Laurentide ice divide from the vicinity of Hudson Bay. The extensive coverage by Late Wisconsinan ice may indicate that this western ice divide had not formed during previous glaciations and that ice flow patterns of earlier glaciations differed significantly. Extensive Late Wisconsinan ice coverage of Alberta means that the ice-free corridor was restricted in extent.