Periglacial cirque analogs: Elevation trends of cryoplanation terraces in eastern Beringia

Abstract

Cryoplanation terraces are large erosional landforms common in cold, unglaciated mountainous environments. Terrace sequences are composed of alternating slope segments with gently sloping treads and steep rubble-covered risers, and culminate in extensive summit flats. Many unglaciated upland landscapes in eastern Beringia are dominated by these landforms. Indirect evidence indicates that they evolve through locally intensified weathering and mass-movement processes associated with late-lying snowcover. Geospatial analysis involving nearly 700 cryoplanation terraces in eastern Beringia demonstrates that their elevation rises from 175 to 350 masl on Bering Sea islands to median values >1200m near the Alaska-Canada border. The regional trends of cryoplanation terrace elevation are nearly identical to those of Wisconsinan cirques on several transects across Alaska. The consistency in the elevation trends of glacial cirques and cryoplanation terraces indicates close genetic links between the two classes of feature, involving topographic position, continentality gradients, and the mass balance of localized snow accumulations. Cryoplanation terraces can be considered the periglacial analogs of glacial cirques, and have greater potential as sources of paleoclimatic information than smaller periglacial features more sensitive to short-term climate variations. Process-oriented studies, age determinations, and high-resolution mapping are needed before the paleoenvironmental potential of these landforms can be realized fully.