Paleogene Post-Collisional Forearc Evolution of the Northern Andes Revealed by U-Pb-Th Detrital Zircon Geochronology and Lu-Hf Systematics, in the Cauca Basin, Colombia

Long-lived orogenic systems are characterized by major modifications of sedimentary systems, driven by basement unroofing and block displacements, complicating the identification of past sedimentary source areas. For instance, in the Northern Andes, alternating contractional and strike-slip tectonic phases between the Late Cretaceous and the Pliocene have hindered precise paleogeographic interpretations. The Central and Western cordilleras of Colombia, along with the Cauca intermontane basin, preserve a sedimentary record that captures source area modifications related to the Paleogene deformation phases of the Colombian Andes. In this study, we present new sandstone petrography, detrital zircon U-Pb geochronology, and zircon Hf isotopic data from poorly studied Cretaceous to Paleogene sedimentary units in the Cauca Basin and the Western Cordillera of Colombia. Our results indicate Late Cretaceous and Eocene depositional ages for the units in the Cauca Basin. Integrated with previously published datasets, these new results refine the Paleogene paleogeography of the Northern Andes and reveal the intense sedimentary reworking of the Cretaceous sedimentary covers during the unroofing of the Central and Western Cordilleras. • •Paleogene evolution of the Cauca forearc basin in Colombia. • Cretaceous sedimentary covers from the Central and Western cordilleras were recycled into forearc basins during the Paleogene. • Sedimentary patterns indicate discontinuous, along-strike uplift of the Western Cordillera.