Optically stimulated luminescence (OSL) dating of the sedimentation history of the Yzeron Basin (Chaudanne sub-catchment), Rh?ne valley, France

摘要

Optically stimulated luminescence (OSL) dating is used to determine the (robust) chronology of the phases of sediment deposition and incision in a headwater sub-basin of the Yzeron Basin, France. Different statistical approaches to extract the mean equivalent dose from dose distributions are compared to estimate the effect of differential bleaching of the OSL signal prior to deposition. Two approaches result in OSL ages that are internally consistent and in excellent agreement with radiocarbon dating, indicating that all investigated sediments are younger than AD 1500. From this data a complex deposition and incision history is constructed for the last 500 years. It is concluded that sediment deposition was mainly forced by sediment supply from ploughing areas. Two short-lived phases of incision during the first half of the 19th century were probably caused by a decrease of sediment supply due to a decline in the frequency of heavy precipitation events. The channel incised during this period was later partly filled with sediment. The decline of agricultural land use from about 1915 onwards decreased sediment supply, while the increase of urbanisation from about 1950 amplified the flow energy of flooding by pluvial waters and overflows from storm basins, causing the presently ongoing incision in the area that began about AD 1975.