Characteristic periglacial topography: Multi‐scale hypsometric analysis of cryoplanated uplands in eastern Beringia

Abstract

General geomorphometry is concerned with the geometric form of the continuous land surface and can be useful for identifying topographic “signatures.” Hypsometry has found numerous applications in several subfields of geomorphology, but has not been used extensively in published periglacial work. Hypsometric analysis was applied in this study to several unglaciated and glaciated locales in Alaska's Yukon‐Tanana Upland and Indian River Upland physiographic sections, extensive areas of eastern Beringia in which cryoplanation landforms are ubiquitous. Never‐glaciated terrain in this region has a hypsometric signature distinctly different from that of glaciated areas within sample areas ranging in size from 0.25 to 100 km2. Cryoplanated terrain exhibits a distinctive convex‐upward hypsometric signature, a reflection of a greater proportion of the reference solid (land mass) remaining intact than in typical mature fluvial or glaciated terrain. Because the elevational position of cryoplanation terraces is slightly below and parallel with snowline position it is, in effect, climatically determined from above, and localized planar surfaces develop near that level. Comparison with terrain in the southwestern USA demonstrates that substantial differences also exist between the hypsometry of upland periglacial terrain in eastern Beringia and that of inselbergs and pediments in warm‐desert geomorphic landscapes, casting doubt on a suggestion that cryoplanation terraces and cryopediments in high‐latitude mountains could be inherited from past intervals of subtropical desert conditions We conclude that characteristic periglacial erosional topography exists in unglaciated areas of Beringia and can be detected and described quantitatively through objective methods.