Past hydro-pedological events and trend reflected in the Mid–Late Holocene alluvial record of the Middle Rhône Valley and tributaries: A new reference for South East France

This paper proposes a new approach to quantitative geomorphology and paleopedology in the mid-Rhône valley (MRV) based on a compilation of geomorphological metadata from 25 tributaries of the Rhône river and subordinate floodbasins, including 51 geomorphological and paleopedological sites. This study compares two types of hydrogeomorphological data formalization: a temporal similarities analysis between paleosols and fluvial aggradation of sub-basins, and a quantitative analysis by summed probability distributions comparing floodplain stability and activity phases in cumulative density functions of categorized ¹⁴C and chronocultural dates. Alluvial chronologies at centennial to millennial time scales, coinciding with a modification in sedimentation rate, or river style, demonstrate temporal and spatial patterning of MRV alluviation, pedogenesis and erosion across the western Prealpine region, with detection of 24 main Holocene alternative periods (activity versus stability). To explore possible large-scale hydroclimatic teleconnections, the Holocene MRV results are aligned, and correlations are made, with those of a range of paleohydrological proxy studies from all Rhône drainage basins, Western Europe and the Mediterranean. The MRV rivers respond to the majority of Holocene rapid climatic changes and from 4000/3000 cal a bp to an accelerated sediment delivery and torrentiality from slopes and headwaters, which results in the development of sedimentary cascades from upstream to downstream in the Rhône valley to the delta (the main drivers are discussed in detail in in a companion paper to follow).