THE GLACIATION OF THE CYPRESS HILLS OF ALBERTA AND SASKATCHEWAN AND ITS REGIONAL IMPLICATIONS

Understanding the deglaciation sequence of the Cypress Hills and the s urrounding area permits a deeper understanding of the style and chrono logy of deglaciation in southeast Alberta and southwest Saskatchewan. This paper revises previously published chronologies. Five deglaciatio n events, the Underdahl Advance, Middle Creek Advance, Altawan Advance , Pakowki Advance, and the Etzikom Advance, have been recognized in th e study area. Of these, the Middle Creek and Altawan Advances are newl y recognized. The Late Wisconsinan ice (Underdahl Advance) was the mos t extensive ice to affect the Cypress Hills area; it terminated in Mon tana. Erratics distributed on the flanks of the Cypress Hills, beyond this ice limit, are interpreted to reflect ice rafting across ice cont act proglacial lakes. The erratics are not remnants of older more exte nsive ice advances as previously thought. The revised deglaciation seq uence 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 Hill s was much more stable. It is possible that the West Lobe was not coup led to the ice north and east of the Cypress Hills and that the West I ce Lobe flowed from an ice divide in the central part of the Northwest Territories. The East Lobe flowed from a Laurentide ice divide from t he vicinity of Hudson Bay. The extensive coverage by Late Wisconsinan ice may indicate that this western ice divide had not formed during pr evious glaciations and that ice flow patterns of earlier glaciations d iffered significantly. Extensive Late Wisconsinan ice coverage of Albe rta means that the ice-free corridor was restricted in extent. Copyrig ht (C) 1996 INQUA/Elsevier Science Ltd