Glacial Erosion Rates Determined at Vorab Glacier: Implications for the Evolution of Limestone Plateaus
Abstract
Understanding how fast glaciers erode their bedrock substrate is one of the key elements in reconstructing how the action of glaciers gives mountain ranges their shape. By combining cosmogenic nuclide concentrations determined in glacially abraded bedrock with a numerical model, we quantify glacial erosion rates over the last 15 ka. We measured cosmogenic Cl-36 in fourteen samples from the limestone forefield of the Vorab glacier (Eastern Alps, Switzerland). Determined glacial erosion rates range from 0.01 mm a(-1) to 0.16 mm a(-1). These glacial abrasion rates differ quite markedly from rates measured on crystalline bedrock (>1 mm a(-1)), but are similarly low to the rates determined on the only examined limestone plateau so far, the Tsanfleuron glacier forefield. Our data, congruent with field observations, suggest that the Vorab glacier planed off crystalline rock (Permian Verrucano) overlying the Glarus thrust. Upon reaching the underlying strongly karstified limestone the glacier virtually stopped eroding its bed. We attribute this to immediate drainage of meltwater into the karst passages below the glacier, which inhibits sliding. The determined glacial erosion rates underscore the relationship between geology and the resulting landscape that evolves, whether high elevation plateaus in limestone terrains or steep-walled valleys in granitic/gneissic areas. Show more
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https://doi.org/10.3929/ethz-b-000508919Publication status
publishedExternal links
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GeosciencesVolume
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MDPISubject
Glacial erosion rates; Cosmogenic Cl-36; Swiss Alps; Limestone plateau; BündnerbergjochOrganisational unit
03754 - Willett, Sean / Willett, Sean
08619 - Labor für Ionenstrahlphysik (LIP) / Laboratory of Ion Beam Physics (LIP)
Funding
175794 - Deciphering the timing and dynamics of glacier advances in the Alps during the Last Glacial Maximum with cosmogenic nuclide dating: a north-south perspective (SNF)
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