Abstract:

This study explores the role of crustal shortening as a mechanism for Late Cenozoic surface uplift in the northern Bolivian Andes between c. 16°S and c. 19°S, based on new geological cross-sections across the Corque–Corocoro basin in the Altiplano (c. 60 km thick crust today), and published radiometric ages of volcanic rocks, in the context of a simple 2D crustal balancing model. Deformation since c. 10 Ma (mainly between 10 and 6 Ma) involved 28 ± 7 km of shortening across the Corque–Corocoro basin, with a wider zone of lower crustal strain, and a total of c. 70 km of underthrusting in the Subandes. The uplift model is supported by dynamical analyses and is identical within 2σ error to published palaeo-elevation proxies, with 2.5 ± 0.5 km of surface uplift in the Corque–Corocoro basin since c. 10 Ma (1.8 ± 0.5 km between 10 and 6 Ma), and 1.6 ± 0.5 km outside the basin. In this way, the Late Cenozoic palaeo-elevation record in the northern Bolivian Andes can be explained within error entirely in terms of the Late Cenozoic crustal thickening expected for the observed history of crustal shortening.

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