Title
Late Quaternary incision rates in the Vesubie catchment area (Southern French Alps) from in situ-produced <sup>36</sup>Cl cosmogenic nuclide dating: Tectonic and climatic implications
Date Issued
01 January 2014
Access level
open access
Resource Type
journal article
Author(s)
Saillard M.
Petit C.
Rolland Y.
Braucher R.
Bourlès D.L.
Revel M.
Jourdon A.
Universite de Nice Sophia-Antipolis
Publisher(s)
Blackwell Publishing Ltd
Abstract
We have estimated recent river incision rates using the in situ-produced 36Cl cosmogenic nuclide concentrations. The target site consists of a ~25 m high vertical profile along a polished river cliff located in Jurassic limestones in the Vesubie catchment area, in the southern French Alps. The 36Cl exposure ages of the sampled river polished surface range from 3 to 14 ka, i.e., after the Last Glacial Maximum. Our data suggest as a first approximation a linear age/height relationship and lead to a mean incision rate of 2.2 mm a-1 over the last 14 ka. More precisely, incision rates are characterized by two peaks reaching ~2 and 4-5 mm a-1 at 4-5 ka and 11-12 ka, respectively, separated by a period experiencing a lower incision rate (~1 mm a-1). A chi-plot of the river longitudinal profile suggests that on the long term, the river is close to equilibrium conditions with a concavity index of 0.475. The evolution of the Vesubie River longitudinal profile over a time period of 2 Ma based on the stream power law of river incision was then modeled with varying erodibility coefficients and uplift rates ranging from 0.5 to 2 mm a-1. The best fitting models yield erodibility coefficient values ranging from 2.5 to 9.0 × 10-6 m-0.475 a-1 for the considered uplift rates. For long-term uplift rates lower than 2 mm a-1, an increase of the erodibility coefficient during the last 16 ka, with two peaks at 11-12 and 4-5 ka, is necessary to precisely match the observed incision rates and is interpreted as resulting from recent climatic changes. These variations do not strongly affect the general shape of the river profile and suggest that the measured short-term incision rate is dominated by a climatic signal, which does not preclude the possible role of tectonic uplift. Key Points We obtained fifteen 36Cl exposure ages of a polished river cliff An incision rate of 2.2 mm/a is computed for the last 15 ka Incision rates are related to Holocene climatic changes ©2014. American Geophysical Union. All Rights Reserved.
Start page
1121
End page
1135
Volume
119
Issue
5
Language
English
OCDE Knowledge area
Geología Geoquímica, Geofísica
Scopus EID
2-s2.0-84902449353
Source
Journal of Geophysical Research: Earth Surface
ISSN of the container
21699011
Sources of information: Directorio de Producción Científica Scopus