『Abstract
Over the past decade, in situ-produced cosmogenic nuclides have
revolutionised the study of landscape evolution. In particular,
numerous studies have demonstrated that, in active tectonic settings,
cosmic ray exposure dating of deformed or displaced geomorphic
features makes it possible to quantify long-term deformation rates.
In western European countries, erosion due to climatically driven
processes and human activities is probably the factor that most
limits the accuracy of exposure ages and landscape modification
rates. In this study, we present the results of a depth-profiling
technique applied to alluvial terraces located along the Rhone〔oの頭に＾〕 and the Moyenne Durance rivers. The expected
decrease with depth of the measured 10Be concentrations
has been modelled using 81χ2 inversion method in order
to constrain the exposure history of the alluvial sediments. The
results suggest that: (1) over the Quaternary, the local surface
erosion rates including both regional uplift and climatically
driven processes acting on landforms are on the order of 30 m/Myr
in southeastern France, and (2) providing a fairly good bracketing
of the exposure age, the modelled abandonment age of alluvial
terraces affected by the Moyenne Durance Fault allows estimating
incision rates, comparing the alluvial terrace elevations with
topographic river profiles, and a minimum vertical slip rate value
of roughly 0.02 mm/yr for the southern segment of the Moyenne
Durance Fault.
Keywords: Be-10: Cosmogenic nuclides; Erosion rates; Active faults;
Southeastern France』
1. Introduction
2. Structural and seismological background: the Provence area
3. Methodology
3.1. Cosmogenic production near the Earth's surface
3.2. χ2 fit modelling of the data
4. Application to natural depth profiles
4.1. Sampling site selection
4.2. Application to a ‘Villafranchian’ Rhone〔oの頭に＾〕
terrace: the Bois Clary alluvial terrace
4.2.1. Structural and geomorphic frameworks
4.2.2. χ2 fit-based inversion modelling for the ‘Villafrachian’
Bois Clary terrace
4.2.3. Significance of the estimated 〜24 m/Myr erosion rate
4.3 Application to Moyenne Durance alluvial terraces
4.3.1. Structural framework
4.3.2. Geomorphic framework
4.3.3. Near-surface geophysical survey of the MDF
4.3.4. Sampling of the alluvial terraces and χ2 modelling
4.3.5. Significance of the estimated parameters
5. Discussion
6. Conclusions
Acknowledgements
References