Thermochronologic and geomorphometric constraints on the Cenozoic landscape evolution of the Northern Andes: Northwestern Central Cordillera, Colombia

Abstract

New geochronologic, thermochronologic, and geomorphometric landscape analyses were performed to discriminate the relationships between tectonics and geomorphology in the northwestern portion of the Central Cordillera, Northern Andes (Colombia). This segment of the Andean belt includes two contrasting geomorphic domains, namely the Antioqueño Plateau (AP) and the Cauca River Canyon (CRC). At present, these domains are connected fluvially by the San Andrés River Catchment (SARC) and disrupted structurally by the Espíritu Santo Fault (ESF). Zircon U/Pb ages indicate Triassic metamorphism and Late Cretaceous magmatism, suggesting the absence of major Cenozoic thermal events related to magmato-metamorphism that could affect low-temperature thermochronology datasets. New (U-Th)/He data were collected along vertical profiles and modeled numerically using HeFTy® and Age2Edot® software. The modeling results suggest a continuum rapid cooling event during the Paleocene- Eocene associated with erosional exhumation. Erosion rates derived from relationships between zircon (U-Th)/He ages and elevation, are approximately 0.2–0.6km/Ma and therefore slightly lower than estimates derived from inverse thermal modeling (ca. 0.6–0.9km/Ma), Differences between observed and estimated exhumation rates could be due to differential surface uplift and reactivation of the ESF. Such reactivation produced systematically younger (U-Th)/He ages near faulted, popped-up blocks, suggesting active deformation since the Oligocene–Early Miocene. Geomorphometric parameterization, applied to both the AP and the CRC, suggests a complex mixture of processes such as differential surface uplift, landscape rejuvenation, relief inversion, preservation of relict landscapes, and reorganization of the fluvial system. Our investigation documents: i) a phase of rapid exhumation during the Late Paleocene-Eocene that favored posterior development of low relief surfaces; ii) post-Eocene ESF reactivation, differential uplift, and relict landscape preservation on the AP; and iii) post-Oligocene landscape rejuvenation and fluvial capture of the SARC by upward progression of the erosional wave-front through the CRC.