Abstract Nazca–South American plate interaction provides a classic example of a subduction-type convergent margin (e.g. Dewey & Bird 1970 ), in which the continental lithosphere overrides the oceanic plate. Evidence of subduction processes having taken place along the western margin of South America since at least Triassic times has been thoroughly described in the literature (e.g. Mpodozis & Ramos 1989 ) and elsewhere in this book. Although subduction has been an essentially continuous process along the Andes, its impact on the geological evolution of the continent varies with time and along-strike (e.g. Jordan et al. 1983 b , 2001 ). Plate kinematics, the subduction of passive and/or active ridges, fracture zones, plate age at the trench, and climate change have all been invoked as controlling factors for continental plate geological evolution and segmentation (e.g. Jarrard 1986 ; Gutscher et al. 2000 b ; Yañez et al. 2001; Lamb & Davis 2003 ; Yáñez & Cembrano 2004 ; Sobolev & Babeyko 2005 ). Figure 9.1 shows the tectonic and morphologic elements that shape the geological evolution of the Andean margin. The tectonic segmentation shown on this figure provides a useful reference for the geological evolution of the Andes. The Andean mountain chain trends NNE–SSW between latitudes 18°S and 48°S with slight local variations in strike but with significant latitudinal changes in morphotectonic configuration ( Fig. 9.1 ). Between 18°S and 28°S, the Andes consist, from west to east, of the Coastal Cordillera, Central Depression, Precordillera and Western (Main) Cordillera with the Altiplano and Puna to