Geomorphology, internal structure, and successive development of a glacier foreland in the semiarid Chilean Andes (Cerro Tapado, upper Elqui Valley, 30°08′ S., 69°55′ W.) Sébastien Monnier a, ⁎, Christophe Kinnard a,b , Arzhan Surazakov a , William Bossy c a Centro de Estudios Avanzados en Zonas Áridas (CEAZA), Raúl Bitrán s/n, La Serena, Chile Canada b Present address: Département des Sciences de l'Environnement, Université du Québec à Trois-Rivières, 3351, Boul. des Forges, C.P. 500, Trois-Rivières, Canada c University Paris 1-Panthéon/Sorbonne, Paris, France abstract article info Article history: Received 18 February 2013 Received in revised form 28 October 2013 Accepted 29 October 2013 Available online 7 November 2013 Keywords: Landform assemblage Debris-covered glacier Rock glacier Moraines Ground-penetrating radar Subsurface ice We use geomorphological analysis, sedimentological survey, remote sensing, and ground penetrating radar (GPR) in order to understand the complex landform assemblage found in front of the Cerro Tapado glacier in the upper Elqui River catchment, semiarid Andes of Chile. The geomorphological analysis highlights prominent boundaries dividing the landform assemblage into (from the upper part to the lower part) an upper latero- frontal moraine complex, an upper debris-covered glacier, a lower debris-covered glacier, two rock glaciers, and a lower morainic complex. The sedimentological survey highlights the rather small size of the surface debris (in general b 20 cm) and the predominance of porphyritic rhyolite. Remote sensing data show that, between 1956 and 2010, considerable (N 400 m) receding of the glacier occurred, along with downslope displacements (dm–m·y -1 ) of most of the landform units and a significant evolution of the thermokarst features on the debris-covered glaciers. Considerable surface lowering occurred in the upper part of the assemblage, while local- ized bulging is seen along the morphological boundaries in the lower units. The GPR profiles highlight spectacular internal structure in the upper debris-covered glacier with up to 80 m of buried ice. In the other landform units, the internal structure is less visible and more heterogeneous. The analysis of the radar wave velocity along the GPR profiles reveals the occurrence of air-filled and moist zones in the internal structure. The geomorphological assemblage is fundamentally characterized by its morphological, structural, and dynamical boundaries and defined as a young (probably b 2000 years) polygenetic construction with landform units having added to/overlapped one another. The rock glaciers do not derive from the present debris-covered glacier but preexist to it. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Glacier forelands (sometimes written as ‘forefields’) are strictly defined as the areas in front of retreating glaciers (e.g., Matthews and Whittaker, 1987). Their geomorphological and geological study can be made by referring to the concept of ‘glaciated valley landsystem’ (Evans, 2005, pp. 372–406). The latter concept, in moun- tain environments characterized by former glacier occupation, con- siders assemblages of landforms recording the juxtaposition and migration of different depositional environments (ice-marginal, supraglacial, subglacial, proglacial, periglacial, and paraglacial). From this point of view, many recent works have dealt with the deposition- al landform assemblages resulting from glacier–permafrost interac- tions during late Pleistocene–Holocene glacier advances and essentially during the Little Ice Age (LIA). These works, mainly con- ducted in the European Alps (e.g., Lugon et al., 2004; Haeberli, 2005; Kneisel and Kääb, 2007; Ribolini et al., 2007, 2010; Monnier et al., 2011) and rarely elsewhere (Trombotto and Borzotta, 2009, in the Argentinean Andes; Bodin et al., 2010, in the Chilean Andes), insisted on the complex geomorphological and thermal interactions occurring when glaciers advanced over preexisting permafrost and on the geomorphological response of the concerned areas following the retreat of the glaciers. In such context, rock glaciers – the visible expression of creeping ice–rock mixture in permafrost conditions (Barsch, 1996; Berthling, 2011) – can commonly be assembled with moraines, especially moraines expressing glaciotectonic processes (i.e., composite moraine ridges) and moraines expressing bulldozing processes (i.e. push moraines: Benn and Evans, 1998). The concerned landform assemblages are furthermore likely to host amounts of sub- surface ice, especially buried glacial ice inherited from the last glacier advance, as well as periglacial ice formed after it. They can thus be, especially in dry mountain ranges, of hydrological and societal impor- tance (Azócar and Brenning, 2010; Bodin et al., 2010). In this study, we further explore this issue by studying the landform assemblage constituting the foreland of the Cerro Tapado glacier in the semiarid Andes of Chile. There, the landform assemblage is particularly complex and impossible to decipher Geomorphology 207 (2014) 126–140 ⁎ Corresponding author. Tel.: +56 51 334869; fax: +56 51 334741. E-mail address: sebastien.monnier@ceaza.cl (S. Monnier). 0169-555X/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.geomorph.2013.10.031 Contents lists available at ScienceDirect Geomorphology journal homepage: www.elsevier.com/locate/geomorph