Temporal Variation in Climate and Tectonic Coupling in the Central Andes

Abstract

Analog and numerical models predict a coupling between climate and tectonics whereby erosion infl uences the deformation of orogens. A testable prediction from modeling studies is the decrease in width of mountain ranges as a result of increased precipitation. Here we evaluate the effect of climate on a critically tapered orogen, the central Andes, using sequentially restored, balanced cross sections through wet (15°–16°S) and dry (21°S) regions of the orogen. In these regions, tectonics, basin geometry, and style of deformation are similar, allowing us to use variations in propagation (or changes in percent shortening) to evaluate whether alongstrike changes in width and morphology are climate driven in the north. Results indicate similar total percent shortening along the northern (40%) and southern (37%) sections, suggesting that a wetter climate has not limited the width (propagation) in the north. However, comparison of early (45–25 Ma) and recent (ca. 20–0 Ma) shortening indicates that early deformation produced 45% ± 2% shortening of both sections, while recent deformation produced 41% ± 2% (north) versus 32% ± 2% (south) in the actively deforming Subandes. The latter suggests a coupling between climate and tectonics that began between ca. 19 and 8 Ma, and continues to 0 Ma, potentially limiting the width of the northern Subandes by ~40 km.