Rapid regional surface uplift of the northern Altiplano plateau revealed by multiproxy paleoclimate reconstruction

Abstract

The central Altiplano is inferred to have experienced ∼2.5±1km surface uplift between ∼10 and 6 Ma, while the southern Altiplano experienced a similar magnitude of surface uplift that began earlier, between ∼16 and 9 Ma. To properly constrain the along strike timing of the Altiplano plateau surface uplift, it is necessary to know how and when the northernmost part of the Altiplano plateau evolved. We reconstruct the paleoclimate and infer the corresponding paleoelevation from the Miocene–Pliocene deposits of the Descanso–Yauri basin (14–15°S) in the northernmost part of the Altiplano plateau using 4 different proxies, including carbonate clumped isotope composition (i.e., Δ_(47) values), carbonate δ^(18)O_c, leaf wax δD_(wax) and pollen assemblages from paleosol, lacustrine and palustrine carbonates and organic-rich sediments. The isotopic signatures reflect past climate conditions of mean annual air temperature (Δ_(47)) and meteoric water isotope values (δ^(18)O_c, δD_(wax)). Our results show that the northernmost plateau remained at low elevation (0.9±0.8 to 2.1±0.9km) until late Miocene time (∼9 Ma) characterized by ∼15 °C warmer than modern temperature (mean annual air temperature of 23±4°C, 2σ), low elevation vegetation and precipitation signature with reconstructed □ δ^(18)O_(mw) (VSMOW) of −8.3±2.0‰(2σ) from carbonate (δ^(18)O_c) and −8.6±1.8‰(2σ) from leaf wax (δD_(wax)). Modern elevations of 4 km were not reached until 5.4±1.0Ma, as indicated by a negative shift in δD_(wax) (VSMOW) from −143.4±12.8‰(2σ) to −209.2±21.1‰(2σ) between 9.1±0.7 and 5.4±1.0Ma. The timing of surface uplift of the northernmost Altiplano is consistent with the evidence for late Miocene surface uplift of the central Altiplano (16–19°S) between 10 and 6 Ma, and indicates that regional scale uplift in the northern–central plateau significantly postdates the onset of surface uplift in the southern Altiplano (19–22°S) between ∼16 and 9 Ma. These results are consistent with piecemeal removal of the lower dense lithosphere, combined with possible lower/middle crustal flow from south to north in the plateau acting as the main mechanisms for the formation of the Altiplano plateau.

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