Large-scale geomorphological mapping of cryoplanation terraces in Alaska and British Columbia

Authors: Clayton Queen*, Michigan State University Department of Geography, Environment, and Spatial Sciences, Kelsey Nyland, Michigan State University Department of Geography, Environment, and Spatial Sciences, Frederick Nelson, Michigan State University Department of Geography, Environment, and Spatial Sciences; Northern Michigan University Earth, Environment, and Geographical Sciences
Topics: Cryosphere
Keywords: Periglacial, Geomorphology, Alaska
Session Type: Illustrated Paper
Day: 4/12/2018
Start / End Time: 10:00 AM / 11:40 AM
Room: Canal St. Corridor, Sheraton, 3rd Floor
Presentation File: No File Uploaded

Cryoplanation terraces (CTs) are large periglacial features forming series of nearly planar treads and steep scarps. These landforms constitute entire slope sequences in many upland periglacial environments. The oft-cited hypothesis for the formation of CTs is parallel retreat of scarps in response to weathering and transport processes associated with late-lying snow patches. CTs are best developed in Beringia, the land area bounded by the Lena River and the Mackenzie River, and encompassing the former Bering Land Bridge. Owing to geographic patterns of moisture availability, Beringia remained largely unglaciated during much of the Quaternary. Terraces in this upland periglacial landscape are dominant landforms and have been noted in the literature for more than a century. To date, however, little process-based or quantitative study has been directed towards understanding the genesis of CTs, and these features remain contentious in the literature. Some researchers have provided evidence that the terraces are formed through climatically driven processes, while others argue that they are inherited features from past climatic conditions. This research focuses on three study sites forming a transect across central Alaska. At each study site, large-scale geomorphological maps incorporating surficial geomorphic features and morphometry were combined into a GIS-database. Periglacial features at sites in Alaska were compared with observations from an active high-elevation site near Atlin, British Columbia. Data indicate that prominent sedimentological and geomorphic patterns develop during terrace formation. These observations provide new insight into the long-proposed “nivation model" of CT development.

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