Preprints
https://doi.org/10.5194/egusphere-2023-2154
https://doi.org/10.5194/egusphere-2023-2154
24 Nov 2023
 | 24 Nov 2023

Late Pleistocene – Holocene denudation, uplift, and morphology evolution of the Armorican Massif (western Europe)

Oswald Malcles, Stéphane Mazzotti, Philippe Vernant, and Vincent Godard

Abstract. Elevated Plio-Pleistocene coastal and marine markers in stable continental regions are commonly explained by a combination of eustatic sea-level variations and regional geodynamics (e.g., mantle dynamics, active faults). In this study, we test the role of erosion rates on the Late Pleistocene uplift and landform evolution of the Armorican Massif, western France. Denudation rates are estimated for 19 drainage basins using terrestrial cosmogenic nuclide (10Be) measurements in quartz. They range between 3 and 34 m.Ma-1, with a factor of two difference between the western highland region and the central lowland region (16 ± 8 m.Ma-1 vs. 9 ± 6 m.Ma-1). Assuming a thin elastic plate model, the lithosphere flexural isostatic response to these denudation rates produces an overall uplift of the Armorican Peninsula from 12 – 15 m.Ma-1 in the central lowland region to 4 – 10 m.Ma-1 in the western peninsula and along the coastline. We show that these erosion-driven uplift rates can explain the uplifted Late Pleistocene marine terraces along the Armorican Peninsula coastline as well as the elevated Quaternary marine deposits in the central lowland region, without necessitating additional geodynamic processes such as regional compression or local active faults. Our results suggest that, in stable continental regions, long-term erosion should be taken into account as a driver of uplift and deformation before trying to derive global or regional geodynamic or tectonic conclusions.

Oswald Malcles, Stéphane Mazzotti, Philippe Vernant, and Vincent Godard

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on egusphere-2023-2154', Timothée Jautzy, 30 Nov 2023
    • AC1: 'Reply on CC1', Oswald Malcles, 01 Dec 2023
  • RC1: 'Comment Review on egusphere-2023-2154', Anne Duperret, 05 Jan 2024
  • RC2: 'Comment on egusphere-2023-2154', Anonymous Referee #2, 16 Jan 2024
  • RC3: 'Comment on egusphere-2023-2154', Andrew Wickert, 01 Feb 2024
Oswald Malcles, Stéphane Mazzotti, Philippe Vernant, and Vincent Godard
Oswald Malcles, Stéphane Mazzotti, Philippe Vernant, and Vincent Godard

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Short summary
The Armorican region (NW France), is marked by several old coastal and marine markers that are today located several tens of meters above the sea level. This fact is commonly explained by sea-level variations and complex tectonic processes (e.g. mantle dynamic). In this study we test the role of the erosion and the associated flexural (lithospheric bending) response. We show that this simple model of flexural adjustment is to be taken into account to explain the regional evolution.