Abstract
Abstract. Assessing the impact of Quaternary glaciation at the Earth's surface implies an understanding of the long-term evolution of alpine landscapes. In particular, it requires simultaneous quantification of the impact of climate variability on past glacier fluctuations and on bedrock erosion. Here we present a new approach for evaluating post-glacial bedrock surface erosion in mountainous environments by combining terrestrial cosmogenic nuclide 10Be (TCN) and optically stimulated luminescence (OSL) surface exposure dating. Using a numerical approach, we show how it is possible to simultaneously invert bedrock OSL signals and 10Be concentrations into quantitative estimates of post-glacial exposure duration and bedrock surface erosion. By exploiting the fact that OSL and TCN data are integrated over different timescales, this approach can be used to estimate how bedrock erosion rates vary spatially and temporally since glacier retreat in an alpine environment.
Highlights
During the last few million years of the Earth’s history, the global climate cooled and evolved towards cyclic glaciations in high-latitude and high-altitude regions (e.g. Miller et al, 1987; Zachos et al, 2001; Lisiecki and Raymo, 2005, 2007)
Three replicates per sample were sliced in a way that a depth and an infrared stimulated luminescence at 50 ◦C (IRSL50) signal can be attributed to each rock slice (Tables A2 and A3)
The IRSL50 signal is bleached near the surface and reaches a plateau at depth
Summary
During the last few million years of the Earth’s history, the global climate cooled and evolved towards cyclic glaciations in high-latitude and high-altitude regions (e.g. Miller et al, 1987; Zachos et al, 2001; Lisiecki and Raymo, 2005, 2007). Molnar and England, 1990; Raymo and Ruddiman, 1992; Champagnac et al, 2007; Herman and Champagnac, 2016) Such erosion rate variations are most expressed in alpine environments, wherein the main erosion agents vary from ice to water and landslides during glacial and interglacial periods, respectively. Quantifying how their respective contributions in sediment production have varied remains challenging because both iceextent fluctuations and associated bedrock surface erosion must be reconstructed simultaneously. Polished bedrock offers the possibility to reconstruct past ice extents and quantify concomitant bedrock surface erosion These landforms are smooth and glossy, resulting from glacial abrasion, quarrying and meltwater erosion during glacial periods Rock alteration can occur in different ways, involving physical (e.g. frost cracking), chemical and biological processes that weaken and modify the rock surface and result in its progres-
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