End member models for Andean Plateau uplift

Diverse techniques have been applied over the past decade to quantify the uplift history of the central Andean Plateau (AP). In this study, opposing models for surface uplift are evaluated including: a rapid rise of similar to 2.5 km similar to 10-6 Ma and a slow and steady rise since similar to 40 Ma. These end member models are evaluated by synthesizing observations of the AP lithosphere and the history of deformation, sedimentation, exhumation, magmatism, uplift, and fluvial incision. Structural and geophysical studies estimate variable shortening magnitudes (similar to 530-150 km) involving cover-to-basement rocks, an isostatically-compensated thick crust (similar to 80-65 km), high heat flow, and zones of variable velocity and attenuation in the crust and mantle. These observations have invoked interpretations such as a hot/weak lithosphere, partial melt, crustal flow, and perhaps current, localized delamination, but do not provide strong support for massive delamination required by the rapid uplift model. Deformation and associated exhumation began similar to 60-40 Ma and generally migrated eastward with consistent long-term average shortening rates (similar to 12-8 mm/yr) in Bolivia, favoring the slow uplift model. Volcanic and helium isotope evidence show an AP-wide zone of shallow mantle melting and thin lithosphere that has existed since similar to 25 Ma, which is inconsistent with the rapid rise model that suggests lithospheric thinning occurred 10-6 Ma. Paleoaltimetry data suggest a rapid similar to 2.5 km elevation gain 10 to 6 Ma, but are equally consistent within error with a linear rise since >= 25 Ma. Widespread fluvial incision (2.5-1 km) occurred along the western flank since similar to 11-8 Ma and may be associated with surface uplift as proposed by the rapid rise model. However, the paleoaltimetry and incision data can also be explained by regional climate change associated with plateau uplift. Implications of these results for reconstructions of AP evolution are that: (I) substantial deformation of a weak lithosphere is essential, (2) AP growth has taken significantly longer (>= 40 Myr) and was more uniform along strike (similar to 1500 km) than previously appreciated, and (3) the slow and steady uplift model is most consistent with available constraints. We conclude that the rapid uplift model may be an overestimate and that a more protracted Cenozoic uplift history is tenable. (C) 2009 Elsevier B.V. All rights reserved.