Resumen
- The Cretaceous tectonic evolution of the western margin of South America involves a shift from an extensional convergent margin toward a more compressional setting that marks the beginning of the Andean Orogeny. In the Colombian Andes, this changing scenario is recorded in the Cretaceous sedimentary and magmatic rocks of the Central Cordillera. A review of field relationships, together with analysis of integrated provenance constraints, including sandstone petrography and detrital zircon geochronology from various localities, suggests that during the Early Cretaceous until the Aptian–Albian, siliciclastic basin fills were characterized by transgressive fining–upward trends, with prominent first–cycle quartzose provenances that indicate strong chemical weathering in the source areas. Jurassic, Triassic, and older detrital zircon U–Pb ages suggest that the igneous and metamorphic rocks forming the basement of the Central Cordillera were the main sources. Furthermore, the presence of Early Cretaceous detrital ages between 120 and 100 Ma, together with interlayered volcanic rocks at the top of the sequence characterized by mixed arc–like, MORB, and E–MORB geochemical signatures, can be related to the evolution of an extensional arc with associated back–arc basin formation. Plutonic rocks with ca. 98 Ma crystallization ages show Nd, Sr, Hf, and O isotope evidence for the existence of thinned continental crust that may account for the dominant mantle signature. By ca. 93 Ma, the Early Cretaceous sedimentary sequences were deformed and intruded by plutonic rocks, which conversely show isotopic fingerprints characteristic of crustal