Sunday, July 31, 2016

Progressive Westward Expansion of North American Continental Ice Sheets During The Quaternery and Implications for the Timing of Initial Human Overland Migration Into the Americas

Chief Mountain (Ninaistakis), viewed from never glaciated Del Bonita, Alberta.
 
















Western limit (Taber, Alberta) of pre-OIS 2 glaciation along the Oldman River.

 























Figure illustrating southern limit of glaciations (Illinoian and Wisconsinan).
Note that Del Bonita, Alberta lies at the southern boundary of
maximum glaciation.
 


























Progressive Westward Expansion of North American Continental Ice Sheets During The Quaternery and Implications for the Timing of Initial Human Overland Migration Into the Americas
Jackson Jr, Lionel E.,
2014 Annual Meeting,
The Geological Society of America
19-22 October, 2014
Paper No. 137-3
(Link)

Abstract:

There is extensive and robust stratigraphic and geomorphic evidence of progressive enlargement of North American (NA) continental ice sheets in a westerly direction during successive glaciations of the Quaternary Period. This culminated in a one-time coalescence of the Laurentide Ice sheet and valley glaciers from the Rocky and Mackenzie mountains and outlet glaciers from the Cordilleran Ice Sheet during marine isotope stage (MIS) 2. This singular coast-to-coast ice (CCI) event ended the pattern of broad ice-free corridors between Cordilleran and continental glaciers that was the norm during all previous Quaternary glacial maxima in North America. Recent discoveries of human settlements above the Arctic Circle in eastern Siberia during MIS 3 (~30 C14 ky BP) and an accumulation of archaeological sites in NA south of the limit of glaciation dating to MIS 3 (specifically <30 C14 ky BP to ~22 C14 ky BP) or contemporaneous with the CCI event during MIS 2 (specifically ~22 C14 ky BP to ~14 C14 ky BP) suggest that the limiting event for initial overland human migration into the Americas was the closing of the ice-free corridor rather than its opening as has been the orthodoxy.

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