Shaded relief map illustrating the high topography of the Southern Central Andes and sampling locations used in the study
Shaded relief map illustrating the high topography of the Southern Central Andes between 29° and 35°S latitude, showing the location of the study area. Sampling locations are shown with red stars. Credit: Lossada et al. [2020], Figure 1b
Source: Tectonics

Fundamental questions regarding the mechanisms behind mountain growth remain unanswered in many parts of the world. Characteristics such as the direction in which mountain-growth progressed and the timing of rapid exhumation (movement of rocks toward the surface) are major clues to identifying these mechanisms, but defining these fundamental characteristics has proven to be a challenge in the central Andes.

Within the Andes, temporal changes in the dip angle of the slab subducting beneath the mountain belt has long been invoked to explain changes in the position of volcanic chains, in the geochemistry of volcanic rocks, and in crustal deformation patterns with accompanying growth of topography.

New detrital thermochronology data presented in Lossada et al. [2020] from the central segment of the Andes has a prominent ~16 million-year age population, demonstrating rapid rock exhumation at that time. This age is approximately 5 to 6 million years older than the timing of flattening of the slab subducting beneath the region, ruling out this candidate as a trigger for mountain growth. Likewise, this timing demonstrates an eastward progression of deformation in the region.

Together, this work calls in to question previously proposed chronologies of Andean deformation for this segment of the mountain chain, and suggests that flat-slab subduction plays a smaller role in mountain-belt development than previously thought.

Citation: Lossada, A. C., Hoke, G. D., Giambiagi, L. B., Fitzgerald, P. G., Mescua, J. F., Suriano, J., & Aguilar, A. [2020]. Detrital thermochronology reveals major middle Miocene exhumation of the eastern flank of the Andes that predates the Pampean flat slab (33°–33.5°S). Tectonics, 39, e2019TC005764.

—Taylor Schildgen, Editor in Chief, Tectonics

Text © 2020. The authors. CC BY-NC-ND 3.0
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