Characterization and quantification of Holocene colluvial and alluvial sediments in the Valdaine Region (southern France). (October 2014)

• Record Type: Journal Article
• Authors: Notebaert, Bastiaan; Berger, Jean-François; Brochier, Jacques Léopold
• Is Part Of: Holocene. Volume 24:Number 10(2014)
• Page Start: 1320
• Page End: 1335
• Publication Date: 2014-10
• Subjects: alluvium -- climate -- colluvium -- France -- geoarchaeology -- geomorphology -- Holocene -- land use -- sediment budget; Geology, Stratigraphic -- Holocene -- Periodicals; Paleoclimatology -- Periodicals; 333.7
• DOI: 10.1177/0959683614540946
• Languages: English
• ISSNs: 0959-6836

Abstract

This study presents a Holocene sediment budget for the Valdaine Region, located at the edge of the southern French Pre-Alps. Holocene colluvial and alluvial deposition are quantified based on existing and new field data. Average sediment thickness values were calculated for different landscape units, and available chronological data were used to make a time-differentiated sediment budget. Total Holocene colluvial deposition in the Valdaine (334 km 2 ) amounts 167 × 10 6 m 3, while alluvial deposition in the Roubion and Jabron catchments (in total 610 km 2, including their catchment upstream the Valdaine) amounts 177 × 10 6 m 3 . Especially, colluvial deposition is high (0.75 × 10 6 g/m 2 ) compared with other catchments. Three major deposition periods (8500–2000bc, 700bc –ad 800 andad 1200–2000) and two periods of relative hillslope stability with local fluvial incision (2000–700bc andad 800–1200) set the framework for a time-differentiated sediment budget. Results show that depositional phases relate to intense land use and hillslope stability and fluvial incision to land abandonment. Catchment averaged colluvial deposition increases from 13 × 10 −6 m 3 /m 2 /yr for 8500–2000bc to 355 × 10 −6 m 3 /m 2 /yr forad 1200–2000, while alluvial deposition increases from 16 to 147 × 10 −6 m 3 /m 2 /yr between the same time periods. A relationship with climatic fluctuations was not found because of the limited temporal resolution of the sediment budget. The derived sediment cascade model shows how alluvial sediments change from fine (silt and clay) to coarse (sand and gravel) afterad 1200. This went along with the establishment of a braided river pattern, indicating that the main source of sediment shifted to the mountainous headwaters. Further research including fingerprinting and modeling would be necessary to further understand the sediment budget and to more accurately quantify the different source areas and the export from the catchment.