Quaternary bedrock erosion and landscape evolution in the Sor Rondane Mountains, East Antarctica: Reevaluating rates and processes

Rates and processes of rock weathering, soil formation, and mountain erosion during the Quaternary were evaluated in an inland Antarctic cold desert. The fieldwork involved investigations of weathering features and soil profiles for different stages after deglaciation. Laboratory analyses addressed chemistry of rock coatings and soils, as well as Be-10 and Al-26 exposure ages of the bedrock. Less resistant gneiss bedrock exposed over 1 Ma shows stone pavements underlain by in situ produced silty soils thinner than 40 cm and rich in sulfates, which reflect the active layer thickness, the absence of cryoturbation, and the predominance of salt weathering. During the same exposure period, more resistant granite bedrock has undergone long-lasting cavernous weathering that produces rootless mushroom-like boulders with a strongly Fe-oxidized coating. The red coating protects the upper surface from weathering while very slow microcracking progresses by the growth of sulfates. Geomorphological evidence and cosmogenic exposure ages combine to provide contrasting average erosion rates. No erosion during the Quaternary is suggested by a striated roche moutonnee exposed more than 2 Ma ago. Differential erosion between granite and gneiss suggests a significant lowering rate of desert pavements in excess of 10 m Ma(-1). The landscape has been (on the whole) stable, but the erosion rate varies spatially according to microclimate, geology, and surface composition. (c) 2006 Elsevier B.V. All rights reserved.