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 massivelyimpacted by human activities is a major challenge. 25 A combination of geochronological approaches isnecessary to accurately date post-1800 sedimentary deposits. Here, we use a combination of a widerange of methods to unravel floodplain sedimentary dynamics, through the example of the UpperRhine which is a highly regulated river. This comprises short--lived radionuclides (137Cs, 210Pbxs) andInfrared Stimulated Luminescence (IRSL) single-grain dating. Luminescence profiling methods (IRSL30 screening, portable luminescence reader) were also used to further characterise sedimentationdynamics. These were combined with a hydrogeomorphological approach based on historicalplanimetric and hydrological data, the knowledge of engineering works as well as the morphosedimentaryadjustments they induced. Our study demonstrates the value of historic maps as well ashistorical hydrological data, which provide precise time markers for dating the sedimentary archive35 under study. We illustrate different assumptions, validity domains and limitations inherent to eachmethod, especially the complexity of 137Cs to date floodplain sediments and the potential ofluminescence methods for dating and estimating sedimentation continuity. We finally show theadvantage of combining geochronological approaches in the construction of robust age models foryoung 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