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      Three-dimensional gravity modelling of a Quaternary overdeepening fill in the Bern area of Switzerland discloses two stages of glacial carving

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          Abstract

          The geometry of glacial overdeepenings on the Swiss Plateau close to Bern was inferred through a combination of gravity data with a 3D gravity modelling software. The target overdeepenings have depths between 155 and > 270 m and widths between 860 and 2400 m. The models show incisions characterized by U-shaped cross-sectional geometries and steep to over-steepened lateral flanks. Existing stratigraphic data reveals that the overdeepenings were formed and then filled during at least two glacial stages, which occurred during the Last Glacial Maximum (LGM) within the Marine Isotope Stage (MIS) 2, and possibly MIS 6 or before. The U-shaped cross-sectional geometries point towards glacial erosion as the main driver for the shaping of the overdeepenings. The combination of the geometries with stratigraphic data suggests that the MIS 6 (or older) glaciers deeply carved the bedrock, whereas the LGM ice sheet only widened the existing valleys but did not further deepen them. We relate this pattern to the different ice thicknesses, where a thicker MIS 6 ice was likely more powerful for wearing down the bedrock than a thinner LGM glacier. Gravity data in combination with forward modelling thus offers robust information on the development of a landscape formed through glaciers.

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          THE GRAVITATIONAL ATTRACTION OF A RIGHT RECTANGULAR PRISM

          Dezso Nagy (1966)
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            Erosion by an Alpine glacier.

            Assessing the impact of glaciation on Earth's surface requires understanding glacial erosion processes. Developing erosion theories is challenging because of the complex nature of the erosion processes and the difficulty of examining the ice/bedrock interface of contemporary glaciers. We demonstrate that the glacial erosion rate is proportional to the ice-sliding velocity squared, by quantifying spatial variations in ice-sliding velocity and the erosion rate of a fast-flowing Alpine glacier. The nonlinear behavior implies a high erosion sensitivity to small variations in topographic slope and precipitation. A nonlinear rate law suggests that abrasion may dominate over other erosion processes in fast-flowing glaciers. It may also explain the wide range of observed glacial erosion rates and, in part, the impact of glaciation on mountainous landscapes during the past few million years.
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              Numerical modeling of the development of U-shaped valleys by glacial erosion

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                Author and article information

                Contributors
                dimitri.bandou@geo.unibe.ch
                Journal
                Sci Rep
                Sci Rep
                Scientific Reports
                Nature Publishing Group UK (London )
                2045-2322
                27 January 2022
                27 January 2022
                2022
                : 12
                : 1441
                Affiliations
                [1 ]GRID grid.5734.5, ISNI 0000 0001 0726 5157, Institute of Geological Sciences, , University of Bern, ; Bern, Switzerland
                [2 ]GRID grid.5801.c, ISNI 0000 0001 2156 2780, Department of Earth Sciences, , ETH Zürich, ; Zurich, Switzerland
                [3 ]Landesgeologie swisstopo, Bern, Switzerland
                [4 ]GRID grid.5734.5, ISNI 0000 0001 0726 5157, Institute of Plant Sciences, , University of Bern, ; Bern, Switzerland
                Article
                4830
                10.1038/s41598-022-04830-x
                8795381
                35087080
                1d50bfb2-1029-4b5d-a1d3-54f4256b95f3
                © The Author(s) 2022

                Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

                History
                : 26 August 2021
                : 3 January 2022
                Funding
                Funded by: FundRef http://dx.doi.org/10.13039/501100001711, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung;
                Award ID: 200021_175555
                Categories
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                © The Author(s) 2022

                Uncategorized
                geology,geomorphology,geophysics,sedimentology
                Uncategorized
                geology, geomorphology, geophysics, sedimentology

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