Growing topography due to contrasting rock types in a tectonically dead landscape

Peifer, D., Persano, C. , Hurst, M. D. , Bishop, P. and Fabel, D. (2021) Growing topography due to contrasting rock types in a tectonically dead landscape. Earth Surface Dynamics, 9(2), pp. 167-181. (doi: 10.5194/esurf-9-167-2021)

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Many mountain ranges survive in a phase of erosional decay for millions of years (Myr) following the cessation of tectonic activity. Landscape dynamics in these post-orogenic settings have long puzzled geologists due to the expectation that topographic relief should decline with time. Our understanding of how denudation rates, crustal dynamics, bedrock erodibility, climate, and mantle-driven processes interact to dictate the persistence of relief in the absence of ongoing tectonics is incomplete. Here we explore how lateral variations in rock type, ranging from resistant quartzites to less-resistant schists and phyllites and up to the least-resistant gneisses and granitic rocks, have affected rates and patterns of denudation and topographic forms in a humid semitropical, high-relief, post-orogenic landscape in Brazil where active tectonics ended hundreds of Myr ago. We show that denudation rates are negatively correlated to topographic relief, channel steepness and modern precipitation rates. Denudation instead correlates with inferred bedrock strength, with resistant rocks denuding more slowly relative to more erodible rock units, and suggest that the efficiency of fluvial erosion varies primarily due to these bedrock differences. Variations in erodibility continue to drive contrasts in rates of denudation in a tectonically inactive landscape evolving for hundreds of Myr, suggesting that equilibrium is not a natural attractor state and that relief continues to grow through time. Over the long timescales of post-orogenic development, exposure at the surface of rock types with differential erodibility can become a dominant control on landscape dynamics by producing spatial variations in geomorphic processes and rates, promoting the survival of relief, and determining spatial differences in erosional response timescales long after cessation of mountain building.

Item Type:Articles
Additional Information:NERC supported the cosmogenic isotope analysis under the CIAF award number 9177.0417. D.P. had support from CAPES under a Science without Borders fellowship (nº BEX 12000/13-2) and, subsequently, a CAPES-PrInt Postdoctoral fellowship (nº 88887.367976 / 2019-00).
Glasgow Author(s) Enlighten ID:Fabel, Dr Derek and Hurst, Dr Martin and Peifer Bezerra, Daniel and Persano, Dr Cristina and Bishop, Professor Paul
Authors: Peifer, D., Persano, C., Hurst, M. D., Bishop, P., and Fabel, D.
College/School:College of Science and Engineering > School of Geographical and Earth Sciences
College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:Earth Surface Dynamics
Publisher:European Geosciences Union
ISSN (Online):2196-6311
Published Online:09 March 2021
Copyright Holders:Copyright © Author(s) 2020
First Published:First published in Earth Surface Dynamics 9(2):167–181
Publisher Policy:Reproduced under a Creative Commons license

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