Spatial Analysis of Cryoplanation Landforms in Beringian Uplands, Alaska, USA

Abstract:

Cryoplanation terraces are large periglacial landforms characteristic of cold, unglaciated mountainous environments. Terrace sequences are composed of alternating slope segments with steep rubble-covered risers and gently sloping treads, culminating in extensive summit flats. Entire Beringian upland landscapes are dominated by these features. Cryoplanation terraces are cut into bedrock and thought to evolve through locally intensified periglacial weathering and mass-movement processes in the vicinity of late-lying snowpatches. Geospatial analysis demonstrates that terrace elevation rises from 100-300 m.a.s.l. on Bering Sea islands to median values greater than 1200 m in the Yukon-Tanana Upland, near the Alaska-Canada border. The regional trends of cryoplanation terrace elevation are similar to those of cirques and reconstructed ELAs across interior and western Alaska, with gradients ranging from 0.74 to 1.2 m km^-1. The similarity of these trends indicates close genetic links between glacial cirques and cryoplanation terraces, involving topographic position, continentality gradients, and the mass balance of localized snow accumulation. Cryoplanation terraces can be considered as 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 their paleoenvironmental potential of these landforms can be fully realized.