Quaternary International 101–102 (2003) 191–201 The effects of late Alpine tectonics in the morphology of the Argentera Massif (Western Alps, Italy–France) Giovanni Musumeci*, Adriano Ribolini, Matteo Spagnolo Dipartimento di Scienze della Terra, Universit " a di Pisa, via S. Maria 53, 56126 Pisa, Italy Abstract Several swath profiles, drainage morphometric parameters, slope and drainage density maps were obtained by DTM analysis of the Argentera Massif (Western Alps). The spatial distribution of the analysed parameters indicates that the central-southern sector is characterized by orographic and drainage characteristics very different from the rest of the Massif. Two main systems of NW- and WNW-trending faults, the Orgials Fault and Valletta Fault, bound this area. Both faults belong to large-scale fault zones: the dextral strike-slip Bersezio Fault and the south-facing Colle del Sabbione thrust. The orientations and kinematics of both faults indicate a late Alpine (Pliocene to recent) SW-verging thrusting coupled with a dextral strike-slip movement. The central-southern sector of the Massif corresponds to the hanging wall of a SW-verging late Alpine thrust zone, and underwent the highest post Pliocene tectonic uplift in the Argentera Massif. The uplift occurred in a transpressive setting with an N–S shortening direction, which is consistent with the post-Pliocene tectonics in the southern portion of the Western Alps. r 2002 Elsevier Science Ltd and INQUA. All rights reserved. 1. Introduction The Cenozoic uplift and exhumation of the Argentera Massif is due to both active tectonics and isostatic release, which characterized the late Alpine (Pliocene to recent) evolution of the Western Alps chain (Debelmas, 1986). The exhumation history of the Argentera Massif, reconstructed for the last 8 Ma on the basis of apatite and zircon fission tracks, is characterized by mean denudation rates of 0.25 mm yr 1 in the late Miocene– Pliocene (8–3 Ma) and 0.8–1 mm yr 1 for the Pliocene– present (3–0 Ma) (Bigot-Cormier et al., 2000; Bogdanoff et al., 2000). In the Argentera Massif, the denudation processes mostly correspond to the glacier and fluvial erosion (Federici et al., 2001a; Julian, 1980), which, since the late Miocene, have affected the Variscan basement (Iawors- ky and Curti, 1960). However, even though these processes involved the whole Massif, there is a big difference in the landscape between the Italian and the French sides, northeast and southwest of the main watershed, respectively. Deeply incised steep slopes on the Italian side strongly contrast with the smoother landscape of the French side. These regional morpho- logic differences (Ribolini, 2000) and the fission track thermochronology (Bigot-Cormier et al., 2000) indicate a spatial variation in the late Alpine exhumation processes throughout the Massif. It is likely that this is related to differential vertical motions of the crystalline blocks within the Massif. The aim of this work is to investigate, through integrated geomorphic and structural analysis, the relationships between topography and active tectonics in the Argentera Massif. A long wavelength geomorphic analysis was carried out using a 50 m digital elevation model (DEM). Five serial swath profiles, nearly perpendicular to the Alpine structures, were traced in order to analyse: (i) the maximum, minimum and mean elevation; (ii) the local relief; and (iii) the depth of landscape incision. The drainage network, automatically extracted by the DEM, was processed to obtain a drainage density map and several geomorphic related parameters. In key areas, a structural analysis was performed in order to investigate the main tectonic structures responsible for the recent vertical movements. A model which explains the Pliocene to the recent morphotectonic evolution of the Argentera Massif is presented. *Corresponding author. Tel.: +39-50-847227; fax: +39-50-500932. E-mail addresses: gm@dst.unipi.it (G. Musumeci), ribolini@dst.u- nipi.it (A. Ribolini), spagnolo@dst.unipi.it (M. Spagnolo). 1040-6182/02/$ - see front matter r 2002 Elsevier Science Ltd and INQUA. All rights reserved. PII:S1040-6182(02)00101-5