Quaternary evolution of a large alluvial fan in a periglacial setting (Crau Plain, SE France) constrained by terrestrial cosmogenic nuclide (10Be)

Abstract

Located in the foreland of the Western Alps, the Crau Plain was the outlet of the Durance River in the Pleistocene. In order to constrain its geodynamic evolution in terms of chronology and denudation rates, the two main Quaternary deposits of this plain have been studied based on cosmogenic nuclide 10 Be concentration measurements along depth profiles. The abandonment of the Miramas and Luquier alluvial surfaces occurred at the beginning of glacial periods, Würm (isotopic stage 4) and Riss (isotopic stage 6), respectively. Discrepancy in denudation rates under similar geomorphological and lithological conditions suggests different denudation processes during glacial and interglacial periods. The denudation rate has been estimated at about 25 mm ka − 1 for the interglacial period and about 60 mm ka − 1 for the glacial period. The abandonment of the Crau Plain as the outlet of the Durance River occurred sometime between 75 and 35 ka.

The Roussillon Basin (S. France): A case-study to distinguish local and regional events between 6 and 3 Ma

“…A sea-level, high-latitude (SLHL) spallation production of 4.03±0.18 at g -1 yr -1 was used and scaled for latitude (Stone, 2000) and elevation. This production rate, recently used by Molliex et al, (2013) in the same area is based from weighted mean of the most recently calibrated production rates in the Northern Hemisphere (Northeastern North America (Balco et al, 2009), Northern Norway (Fenton et al, 2011), Southern Norway and Greenland (Briner et al, 2012). The production rate is calculated for each cells of the present-day DEM constituting the catchment and the mean catchment production rate value is calculated by averaging the values of quartz-producing rocks areas following the method described by Delunel et al, (2010) and using the script of Balco (2001) for the calculation of the shielding factor.…”

A morphological study of Durance River terraces from Tallard to Avignon, South-East France

“…This was never glaciated, although periglacial activity produced huge colluvial aprons [25]. This is further subdivided at Mallemort (41 km) because the lower river was diverted through gaps to the Crau Plains for most of the Pleistocene [25,[31][32][33][34]. b Mirabeau to the Sisteron Defile (91-158 km) is the subnival zone.…”

“…The latter have a surface area of 520 km 2 and an unknown area beneath the Rhône delta. The Eyguières Gap was used in the Pliocene and Early Pleistocene and the Lamanon Gap in the last two glaciations [25,32,33].…”

“…Below 41 km, the latter map only shows Coulon low terraces and some proto-Rhône older residuals. However, if the diversion through the Crau ended at about 70 ka, there must have been rejuvenation by the Durance in the lower valley, [32].…”

“…Pleistocene and earlier deposits form the surface of the Crau [14,18,25,31,32,34,45,[62][63][64][65]. In the late Pliocene, an east-west trough, south of the Eyguières Gap, was the site of oldest deposits (Arles terrace).…”