Denudation rates across the Pamir based on <sup>10</sup>Be concentrations in fluvial sediments: dominance of topographic over climatic factors

A clear understanding of erosion processes is fundamental in order to comprehend the evolution of actively deforming mountain ranges. However, the relative contributions of tectonic and climatic factors and their feedbacks remain highly debated. In order to contribute to the debate, we quantify basi...

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Main Authors: M. C. Fuchs, R. Gloaguen, S. Merchel, E. Pohl, V. A. Sulaymonova, C. Andermann, G. Rugel
Format: Article
Language:English
Published: Copernicus Publications 2015-08-01
Series:Earth Surface Dynamics
Online Access:http://www.earth-surf-dynam.net/3/423/2015/esurf-3-423-2015.pdf
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spelling doaj-19a18be885bb4844a0a3cd1ad1eed2f82020-11-24T23:51:57ZengCopernicus PublicationsEarth Surface Dynamics2196-63112196-632X2015-08-013342343910.5194/esurf-3-423-2015Denudation rates across the Pamir based on <sup>10</sup>Be concentrations in fluvial sediments: dominance of topographic over climatic factorsM. C. Fuchs0R. Gloaguen1S. Merchel2E. Pohl3V. A. Sulaymonova4C. Andermann5G. Rugel6Remote Sensing Group, Institute of Geology, TU Bergakademie Freiberg, Bernhard-von-Cotta-Strasse 2, 09599 Freiberg, GermanyRemote Sensing Group, Institute of Geology, TU Bergakademie Freiberg, Bernhard-von-Cotta-Strasse 2, 09599 Freiberg, GermanyHelmholtz-Zentrum Dresden-Rossendorf, Helmholtz Institute Freiberg for Resource Technology, Bautzner Landstrasse 400, 01328 Dresden, GermanyRemote Sensing Group, Institute of Geology, TU Bergakademie Freiberg, Bernhard-von-Cotta-Strasse 2, 09599 Freiberg, GermanyRemote Sensing Group, Institute of Geology, TU Bergakademie Freiberg, Bernhard-von-Cotta-Strasse 2, 09599 Freiberg, GermanySection 5.1 Geomorphology, German Research Centre for Geoscience GFZ, Telegraphenberg, 14473 Potsdam, GermanyHelmholtz-Zentrum Dresden-Rossendorf, Helmholtz Institute Freiberg for Resource Technology, Bautzner Landstrasse 400, 01328 Dresden, GermanyA clear understanding of erosion processes is fundamental in order to comprehend the evolution of actively deforming mountain ranges. However, the relative contributions of tectonic and climatic factors and their feedbacks remain highly debated. In order to contribute to the debate, we quantify basin-wide denudation rates from cosmogenic <sup>10</sup>Be concentrations in modern river sediments in the Pamir. This mountain range is a unique natural laboratory because the ongoing India–Eurasia collision sustains high deformation rates and, on account of its position at the transition between Westerlies and monsoon, a strong regional climatic variability arises. Sample acquisition and preparation for accelerator mass spectrometry measurements were challenging due to difficult field accessibility, low quartz and high feldspar concentrations and crystal coating. Six samples along the main draining river, the Panj, and five samples within the major, east–west elongated tributary basins allow us to quantify basin-wide denudation rates for the first time in this orogen. An average denudation rate of ~ 0.64 mm yr<sup>−1</sup> reveals a rapid evolution of the entire Pamir. Denudation rates of tributary sub-basins highlight the strong contrast between the Pamir Plateau (0.05 to 0.16 mm yr<sup>−1</sup>) and its margins (0.54 to 1.45 mm yr<sup>−1</sup>). The intensity of denudation is primarily correlated with geometric properties of the surface, such as slope steepness (0.75 quartiles; <i>R</i><sup>2</sup> of 0.81), and to a lesser extent to climatic factors such as precipitation. We thus argue that either tectonic uplift or base-level lowering are the main contributors to denudation processes. Multiple linear regression analysis (best <i>R</i><sup>2</sup> of 0.93) suggests that precipitation may act as a limiting factor to denudation. The highest denudation rates coincide with areas of the northwestern Pamir margin that receive precipitation predominantly from the Westerlies during winter. There, the concentrated discharge during spring and early summer may sustain the pronounced denudation and allow the rapid sediment transport out of the basins. Low slope angles and dry conditions hamper the sediment flux on the plateau and, consequently, denudation. The magnitude of denudation in the Pamir is similar to rates determined in the southern Himalaya despite very different climatic and tectonic conditions. The discrepancy between rates of basin-wide denudation and the fluvial incision that is up to 10 times higher evidences a transient landscape in the Pamir. This underpins the hypothesis that river captures may have caused the strong base-level lowering that drives the enhanced incision of the Panj and its main tributaries.http://www.earth-surf-dynam.net/3/423/2015/esurf-3-423-2015.pdf
collection DOAJ
language English
format Article
sources DOAJ
author M. C. Fuchs
R. Gloaguen
S. Merchel
E. Pohl
V. A. Sulaymonova
C. Andermann
G. Rugel
spellingShingle M. C. Fuchs
R. Gloaguen
S. Merchel
E. Pohl
V. A. Sulaymonova
C. Andermann
G. Rugel
Denudation rates across the Pamir based on <sup>10</sup>Be concentrations in fluvial sediments: dominance of topographic over climatic factors
Earth Surface Dynamics
author_facet M. C. Fuchs
R. Gloaguen
S. Merchel
E. Pohl
V. A. Sulaymonova
C. Andermann
G. Rugel
author_sort M. C. Fuchs
title Denudation rates across the Pamir based on <sup>10</sup>Be concentrations in fluvial sediments: dominance of topographic over climatic factors
title_short Denudation rates across the Pamir based on <sup>10</sup>Be concentrations in fluvial sediments: dominance of topographic over climatic factors
title_full Denudation rates across the Pamir based on <sup>10</sup>Be concentrations in fluvial sediments: dominance of topographic over climatic factors
title_fullStr Denudation rates across the Pamir based on <sup>10</sup>Be concentrations in fluvial sediments: dominance of topographic over climatic factors
title_full_unstemmed Denudation rates across the Pamir based on <sup>10</sup>Be concentrations in fluvial sediments: dominance of topographic over climatic factors
title_sort denudation rates across the pamir based on <sup>10</sup>be concentrations in fluvial sediments: dominance of topographic over climatic factors
publisher Copernicus Publications
series Earth Surface Dynamics
issn 2196-6311
2196-632X
publishDate 2015-08-01
description A clear understanding of erosion processes is fundamental in order to comprehend the evolution of actively deforming mountain ranges. However, the relative contributions of tectonic and climatic factors and their feedbacks remain highly debated. In order to contribute to the debate, we quantify basin-wide denudation rates from cosmogenic <sup>10</sup>Be concentrations in modern river sediments in the Pamir. This mountain range is a unique natural laboratory because the ongoing India–Eurasia collision sustains high deformation rates and, on account of its position at the transition between Westerlies and monsoon, a strong regional climatic variability arises. Sample acquisition and preparation for accelerator mass spectrometry measurements were challenging due to difficult field accessibility, low quartz and high feldspar concentrations and crystal coating. Six samples along the main draining river, the Panj, and five samples within the major, east–west elongated tributary basins allow us to quantify basin-wide denudation rates for the first time in this orogen. An average denudation rate of ~ 0.64 mm yr<sup>−1</sup> reveals a rapid evolution of the entire Pamir. Denudation rates of tributary sub-basins highlight the strong contrast between the Pamir Plateau (0.05 to 0.16 mm yr<sup>−1</sup>) and its margins (0.54 to 1.45 mm yr<sup>−1</sup>). The intensity of denudation is primarily correlated with geometric properties of the surface, such as slope steepness (0.75 quartiles; <i>R</i><sup>2</sup> of 0.81), and to a lesser extent to climatic factors such as precipitation. We thus argue that either tectonic uplift or base-level lowering are the main contributors to denudation processes. Multiple linear regression analysis (best <i>R</i><sup>2</sup> of 0.93) suggests that precipitation may act as a limiting factor to denudation. The highest denudation rates coincide with areas of the northwestern Pamir margin that receive precipitation predominantly from the Westerlies during winter. There, the concentrated discharge during spring and early summer may sustain the pronounced denudation and allow the rapid sediment transport out of the basins. Low slope angles and dry conditions hamper the sediment flux on the plateau and, consequently, denudation. The magnitude of denudation in the Pamir is similar to rates determined in the southern Himalaya despite very different climatic and tectonic conditions. The discrepancy between rates of basin-wide denudation and the fluvial incision that is up to 10 times higher evidences a transient landscape in the Pamir. This underpins the hypothesis that river captures may have caused the strong base-level lowering that drives the enhanced incision of the Panj and its main tributaries.
url http://www.earth-surf-dynam.net/3/423/2015/esurf-3-423-2015.pdf
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