The topographic signature of Quaternary tectonic uplift in the Ardennes massif (Western Europe)

N Sougnez,V Vanacker

doi:10.5194/hess-15-1095-2011

Abstract

Abstract. Geomorphic processes that produce and transport sediment, and incise river valleys are complex; and often difficult to quantify over longer timescales of 103 to 105 y. Morphometric indices that describe the topography of hill slopes, valleys and river channels have commonly been used to compare morphological characteristics between catchments and to relate them to hydrological and erosion processes. This study aims to analyze the link between tectonic uplift rates and landscape morphology based on slope and channel morphometric indexes. To achieve this objective, we selected 10 catchments of about 150 to 250 km2 across the Ardennes Massif (a Palaeozoic massif of NW Europe, principally located in Belgium) that cover various tectonic domains with uplift rates ranging from about 0.06 to 0.20 mm yr−1 since mid-Pleistocene times. The morphometric analysis indicates that the slope and channel morphology of third-order catchments is not yet in topographic steady-state, and exhibits clear convexities in slope and river profiles. Our analysis indicates that the fluvial system is the main driver of topographic evolution and that the spatial pattern of uplift rates is reflected in the distribution of channel steepness and convexity. The spatial variation that we observe in slope and channel morphology between the 10 third-order catchments suggests that the response of the fluvial system was strongly diachronic, and that a transient signal of adjustment is migrating from the Meuse valley towards the Ardennian headwaters.

Highlights

There is great interest across a broad spectrum of geoscience disciplines in unravelling the role of tectonic activity in driving erosion processes and landscape evolution (Burbank et al, 1996; Maddy, 1997)
We observe that the elevation of the shoulder of the river channel convexity is related to the mean uplift: catchments that are located in regions with higher uplift rates generally have knick zones at higher altitude (Fig. 3a)
This suggests that the response of the fluvial system was strongly diachronic, and that a transient signal of adjustment is migrating from the Meuse valley towards the Ardennian headwaters

Summary

Introduction

There is great interest across a broad spectrum of geoscience disciplines in unravelling the role of tectonic activity in driving erosion processes and landscape evolution (Burbank et al, 1996; Maddy, 1997). A whole range of catchment and river parameters exists, and Douvinet et al (2005) highlighted 57 reference indexes Those indices have been related to physical processes and landscape controls, such as streampower models (Whipple and Tucker, 2002; Snyder et al, 2003; Whipple, 2004), stream sediment grain size variation (Surian, 2002; Rice and Church, 1998; Inoue, 1992; Petit et al, 2005), sea level and climate change (Bonnet and Crave, 2003; Roe et al, 2002; Whipple and al., 1999), and recent tectonic activity (Demoulin, 1998; Kirby and Whipple, 2001; Snyder et al, 2000). Most geomorphologic studies involving tectonic activity were concentrated in regions of high uplift rates and/or high denudation rates, such as the Himalayas (Burbank et al, 2003; Wobus et al, 2003; Lague and Davy, 2003), the Andes (Tibaldy and Leon, 2000; Kamp et al, 2005; Vanacker et al, 2007), and the Alps

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Conclusion