Multi-method geochronological approach to reconstruct post-1800 floodplain sedimentation in the Upper Rhine Plain, France
Résumé
The precise dating of sedimentary archives covering the last 200 years in floodplains massively
impacted by human activities is a major challenge. 25 A combination of geochronological approaches is
necessary to accurately date post-1800 sedimentary deposits. Here, we use a combination of a wide
range of methods to unravel floodplain sedimentary dynamics, through the example of the Upper
Rhine which is a highly regulated river. This comprises short--lived radionuclides (137Cs, 210Pbxs) and
Infrared Stimulated Luminescence (IRSL) single-grain dating. Luminescence profiling methods (IRSL
30 screening, portable luminescence reader) were also used to further characterise sedimentation
dynamics. These were combined with a hydrogeomorphological approach based on historical
planimetric and hydrological data, the knowledge of engineering works as well as the morphosedimentary
adjustments they induced. Our study demonstrates the value of historic maps as well as
historical hydrological data, which provide precise time markers for dating the sedimentary archive
35 under study. We illustrate different assumptions, validity domains and limitations inherent to each
method, especially the complexity of 137Cs to date floodplain sediments and the potential of
luminescence methods for dating and estimating sedimentation continuity. We finally show the
advantage of combining geochronological approaches in the construction of robust age models for
young floodplain sedimentary archives in highly anthropized fluvial environments.
Mots clés
Upper Rhine floodplain geochronology IRSL single-grain 137 Cs 210 Pb xs IRSL screening portable luminescence reader planimetric stratigraphic and hydrological
Upper Rhine floodplain
geochronology
IRSL single-grain
137 Cs
210 Pb xs
IRSL screening
portable luminescence reader
planimetric
stratigraphic and hydrological