Abstract
Cenozoic growth of the Andes has been strongly influenced by subduction
dynamics, reactivation of inherited crustal heterogeneities, and the
superposed effects of climate. Subduction of the submarine Carnegie
Ridge has fundamentally impacted late Cenozoic magmatism and tectonic
activity in the northern Andes. Time-temperature inverse modeling of new
thermochronological data from the Western Cordillera of Ecuador reveals
two phases of cooling separated by isothermal conditions. The first
cooling phase immediately postdates early and middle Miocene magmatism
in the Western Cordillera and is attributed to post-magmatic thermal
relaxation. The second cooling phase started after 6 Ma, which we infer
to record the onset of exhumation in the Western Cordillera, coeval with
the last cooling phase in the Eastern Cordillera. Based on these
findings we posit that the onset of subduction of the Carnegie Ridge at
~6-5 Ma increased plate coupling at the subduction
interface and promoted shortening and regional rock uplift in the
northern Andes. Overall, our results highlight the essential role of
bathymetric anomalies in driving regional upper-plate deformation at
non-collisional convergent plate margins.