The Evolution of the Altiplano-Puna Plateau of the Central Andes

Abstract

▪ Abstract The enigma of continental plateaus formed in the absence of continental collision is embodied by the Altiplano-Puna, which stretches for 1800 km along the Central Andes and attains a width of 350–400 km. The plateau correlates spatially and temporally with Andean arc magmatism, but it was uplifted primarily because of crustal thickening produced by horizontal shortening of a thermally softened lithosphere. Nonetheless, known shortening at the surface accounts for only 70–80% of the observed crustal thickening, suggesting that magmatic addition and other processes such as lithospheric thinning, upper mantle hydration, or tectonic underplating may contribute significantly to thickening. Uplift in the region of the Altiplano began around 25 Ma, coincident with increased convergence rate and inferred shallowing of subduction; uplift in the Puna commenced 5–10 million years later.

Slow Long‐Term Exhumation of the West Central Andean Plate Boundary, Chile

“…Although within the bounds of our study we have little constraint on where such anomalies may be, the reproducibility of ZHe ages across the PC and the agreement between the AHe ages used for modeling and mean iso‐elevation bin AHe ages suggest that the effect of such anomalies is likely inconsequential in the results. Long‐term net eastward migration of the arc has been estimated at ~1 km/Myr since the Jurassic (Andriessen & Reutter, 1994), which includes a period of westward retreat to its present location since around the early Miocene (Allmendinger et al, 1997); however, we see no clear imprint of thermal anomalies in the section of the fore arc sampled.…”

“…Subduction of the Nazca (and previously Farallon) Plate under the South American Plate has resulted in a mountain belt characterized by the largest trench‐to‐peak relief on the planet, frequent seismic activity ( M w  > 8.5), and a long‐standing history of volcanism (e.g., Armijo et al, 2015). Notably, three distinctly oriented sections of the range (Figure 1) may be the result of differential shortening recording periods of Andean deformation and uplift (Allmendinger et al, 1997; Isacks, 1988; Roperch et al, 2006), though this uniquely bent geometry may itself lead to focused deformation in the upper plate, particularly at plate corners (e.g., Bendick & Ehlers, 2014; Jordan et al, 1983). Other tectonic controls have been invoked to explain variation in Andean morphology (i.e., angle of convergence, convergence velocity, age of oceanic crust, and trench orientation), though no clear consensus exists on their relative importance (e.g., Barnes & Ehlers, 2009; Maloney et al, 2013; Oncken et al, 2006).…”

More constraints to determine the seismic structure beneath the Central Andes at 21°S using teleseismic tomography analysis

“…Gansser, 1973;Ramos, 1999) and represents one of the world's best examples of an area that has been formed under the effects of uplift and magmatism arising from the subduction of an oceanic plate (Nazca Plate) under a continental plate (South American Plate) (e.g. Barazangi and Isacks, 1976;Coira et al, 1982;Reutter et al, 1988;Isacks, 1988;Baby et al, 1992, Gubbels et al, 1993Wigger et al, 1994;Allmendinger et al, 1997). The orogen reaches its greatest width between ~14°S and ~24°S where subduction of the Nazca plate occurs at angles near 20-30° at a rate of 65mm/yr (Cahill and Isacks, 1992;Angermann et al, 1999;).…”

Migrating deformation in the Central Andes from enhanced orographic rainfall

“…Th e chronology of tectonic deformation along this transect has been restored based on tectonic and stratigraphic investigations, and low-temperature thermochronometres 3,[7][8][9][10][11]26,32,33 . Although the rate of cumulative shortening across the entire Central Andes has been constant between the Oligocene and the present ( Fig.…”

“…Th e Altiplano plateau has an elevation of ~ 4 km ( Fig. 1b ) and extends ca 2000 km in N-S direction and 400 km across strike, linking the Western and Eastern Cordilleras 7 . Th e Eastern Cordillera can be treated as a bivergent wedge of upper crustal rocks 8,9 ( Fig.…”