Climatic and tectonic controls on the development of the River Ognon terrace system (eastern France)

The River Ognon in eastern France is the principal drainage of the southwestern Vosges Mountains. Its lowermost valley reach is oriented parallel to the northwestern front of the Alpine collision zone and is characterized by a well-developed terrace system. Geomorphological, sedimentological, and geochronological analyses were performed on this terrace system and associated deposits. The results allow for reconstructing the Pleistocene evolution of the river valley and for concluding on the processes that led to the formation of the terrace system. The lithological characterization of the terrace deposits by means of heavy mineral analyses indicates pronounced modifications of the river's drainage area. Optically stimulated luminescence dating suggests that the last significant catchment modification and associated sediment accumulation correlates with the last glacial advance in the Vosges Mountains. Despite the apparently strong impact of climatic processes on the evolution of the River Ognon, our investigation also indicates a mild tectonic influence on presently observed terrace distribution.