Climatic significance of glacier retreat and rockglaciers re-assessed in the light of cosmogenic dating and weathering rind thickness in Clarée valley (Briançonnais, French Alps)

Abstract

Recent advances in geochronology provide opportunities to identify the glacial and periglacial sequences in mountain area. In this paper, we focus on the Upper Durance catchment (Southern French Alps), in the Claree valley, where no absolute chronological benchmark was defined. Glacial remnants and periglacial features were investigated, integrated within a chronological scenario thanks to relative (weathering rind thickness) and absolute (CRE technique) dates. We find evidence of the existence of a Late-Glacial valley glacier, that has never been reported before. Then the upper valleys became ice-free during a period corresponding to the Early-Holocene Climate Optimum, whereas two sequences of cirque glaciation are identified during the second half of the Holocene. We also show evidence of three main generations of rockglaciers, which also mainly developed during the second half of the Holocene, probably at the end of the Subboreal period. The location and the altitudes of rockglaciers are strongly dependent on the geomorphic setting (especially the location of the sediment sources), hence complicating their palaeo-climatic interpretations.