Alluvial stratigraphy of the Loire and Arroux rivers (Burgundy, France) [Stratigraphie des alluvions de la Loire et de l 'Arroux, Bourgogne, France

Abstract

Interpretation of satellite imagery, field mapping, stratigraphie and sedimentologic investigations, and a series of radiocarbon and optically- stimulated luminescence dates (OSL) define a record of Late Pleistocene and Holocene landscape change along 100 km of the Loire and Arroux Rivers in southern Burgundy, France. Seven informally designated allostratigraphic units have been differentiated, each representing time periods when rivers were adjusted to prevailing hydrological regimes. Surface morphology of Late- and Post-glacial deposits are well-preserved, showing a distinct trend from braided to meandering channel plan-forms, coupled with overall decreases in channel amplitude and sinuosity through time. Two distinct Late-Pleistocene braided stream channel deposits were emplaced ca. 86-40 ka and 23-1 1 ka, followed by a post-glacial transition to a meandering regime between 11 ka and 7,3 ka. Mid-Late Holocene units show evidence of increasing amounts of overbank deposition, with a peak in fluvial activity ca 3 ka. The youngest meanderbelt terminated around 1.53 ka, coincident with channel straightening, in-filling of abandoned channels, and development of the present gravelly meandering pattern.