Paleosurfaces, paleoelevation, and the mechanisms for the late Miocene topographic development of the Altiplano plateau

We construct a topographic datum across the central Andes between 18°S and 22°S using extensive, well-preserved paleosurfaces that span the entire range. This datum, combined with estimates of topographic change from paleoaltimetry in the Altiplano and geomorphic relief generation estimates from the plateau flanks allow us to reconstruct the paleo-topography of the range at ~ 10 Ma. Using the 10 Ma topography we explore which geophysical processes can create the observed topographic change over the < 4 Ma period between 10 and 6 Ma. Our results indicate that loss of a dense lithospheric root, and possibly contemporaneous crustal flow, are the most likely processes that produced the observed plateau-wide topographic change. Raising the plateau purely by late Miocene crustal thickening would require shortening rates four times greater than those reported for the Cenozoic.