“…Numerous investigations, including both local studies (McLaughlin, 1924;Walker, 1949;Mortimer and Saric, 1975;McKee and Noble, 1982;Megard, 1984;Tosdal et al, 1984;Swanson et al, 1987;Soler and Bonhomme, 1988;Lavenu et al, 1989;Ellison, 1990;Noble et al, 1990;Wasteneys, 1990;Cheilletz et al, 1992;Soler and Jiménez, 1993) and regional syn theses (Mégard, 1987;Sébrier et al, 1988;Sébrier and Soler, 1991), have identified several widespread orogenic episodes in the Cenozoic stratigraphic record of the Central Andes. In this context, it should be noted that whereas the Cordillera Occidental, and particularly its arid or hyperarid Pacific slopes, is dominated by extensive but abruptly generated erosion sur faces, the Tertiary geomorphologic features of the Cordillera Oriental are more complex.…”