Archaeological constraints on some geological interpretations of a Late Wisconsinan site at Varsity Estates, Calgary, Alberta

Abstract

Late glacial history in western Alberta has been a subject of debate as this area lies in the zone of assumed contact of the Cordilleran glaciers and Laurentide ice shield. The geographic limits and timing of the coalescence of the two ice masses, however, are not clear except for the west-central part of the province with the documented merger in the Athabasca valley. Recently, arguments for a complete Late Wisconsinan coalescence in the prairies all along the Rocky Mountain foothills have been presented based on 14C dates >21 ka and cosmogenic 36Cl dates <17 ka from the areas 300 km north and 100 km south of Calgary, respectively, and undated streamlined landforms in the foothills. This scenario is in direct conflict with the archaeological and geological evidence from the key area in the upper Bow Valley, showing eloquently an asynchroneity in the last glacial dynamics in this portion of the province. The recorded early occupation horizon from the Varsity Estates site, NW Calgary , with palaeolithic stone tools sealed in situ on top of the Cordilleran Bow Valley till buried by the Laurentide Glacial Lake Calgary clays in corroboration with braided fluvial channel deposits in between the two major units attest clearly to a subaerial setting prior to the maximum continental ice advance. The interpretation on the alleged glacial contact ignores these facts and does not consider the undated time span of up to 4000 years (ca. 21–17 ka) allowing sufficient time for an early Late Wisconsinan peopling of unglaciated parts of western Alberta even if the area may have been subsequently covered by ice.