The onset of orogenic shortening in the northern Andes Mountains coincided with latest Cretaceous accretion of the Caribbean oceanic plateau. We present isotopic data (εHf in zircon and εNd) coupled with arc position to test whether accretion led to abrupt crustal thickening in the northern Andes of Ecuador and Colombia. A rapid isotopic excursion toward more evolved crustal compositions was synchronous with ca. 75–70 Ma collision in Ecuador and preceded a similar deviation in Colombia at ca. 70–55 Ma. The rapid but diachronous shift to more evolved isotopic signatures is attributed to progressive northward accretion of the oceanic plateau and associated thickening of continental crust. We emphasize the effects of accretion on the magmatic evolution of Cordilleran-type margins, initially provoking shortening and crustal thickening, and ultimately providing a substrate for subsequent arcs.
Item S1 (the U-Pb procedure, age εHf diagrams with samples binned by tectonic domain, map of geochronologic ages in Ecuador, and weighted mean U-Pb dates on igneous samples), Item S2 (coordinates of samples and data generated in this study), and Item S3 (compiled datasets [εHf , εNd, arc location]).<br>
Item S1 (the U-Pb procedure, age εHf diagrams with samples binned by tectonic domain, map of geochronologic ages in Ecuador, and weighted mean U-Pb dates on igneous samples), Item S2 (coordinates of samples and data generated in this study), and Item S3 (compiled datasets [εHf , εNd, arc location]).<br>
Subduction initiation at the Soloman back-arc basin: Contributions from both island arc rheological strength and oceanic plateau collision