Constraining Erosion Rates and Landscape Evolution With In Situ 10Be and 26Al Cosmogenic Nuclides at Table Mountain, Antarctica

Abstract

This study investigates surface weathering and sediment preservation at Table Mountain, a high-elevation, hyperarid, polar landscape in the Transantarctic Mountains. We report cosmogenic nuclide concentrations (¹⁰Be and ²⁶Al) in quartz from bedrock surfaces, erratic boulder lag, and cobbles embedded within Sirius Group sediments to quantify erosion rates. In situ ¹⁰Be and ²⁶Al depth profiles from a 2.95 m permafrost core in the Sirius Group further constrain surface erosion rates and elucidate landscape stability. Measured ¹⁰Be and ²⁶Al concentrations from two sandstone bedrock surfaces adjacent to Sirius Group sediments give erosion rates of 0.18–0.28 m/Myr. An erratic sandstone boulder within the lag above the Sirius Group yields erosion rates of ∼0.42 ± 0.03 m/Myr, whereas two cobbles embedded within the Sirius Group yield higher rates of 0.81–1.12 m/Myr. Depth profiles of in situ ¹⁰Be and ²⁶Al indicate no vertical mixing of Sirius Group permafrost since deposition. Depth profile models are best explained by erosion rates of 0.53^+0.13/_−0.12 m/Myr, and an exposure age of 0.78^+0.06/_−0.08 Ma. We view the model “age” to represent the ∼0.8-million-year time-scale for surface lowering equivalent to one attenuation length of cosmic ray production to achieve steady-state conditions. Continual exhumation of embedded clasts from within the Sirius Group results in an accumulation of clasts forming the observed erosional lag deposit covering the landscape. Our erosion rates of the Sirius Group surface based on in situ ¹⁰Be and ²⁶Al depth profiles are an order-of-magnitude larger than those based on meteoric ¹⁰Be infiltration and further clarification is required.