Tectonic geomorphology of the Serranía de San Lucas (Central Cordillera): Regional implications for active tectonics and drainage rearrangement in the Northern Andes

Abstract

We explore the structural and geomorphological evidence for recent tectonic activity in the Serranía de San Lucas (San Lucas Range, SLR), the northern segment of the Central Cordillera in the Colombian Northern Andes. A morphostructural and geomorphological analysis was carried out in this isolated range using several topographic metrics like the local relief, slope variability, hypsometric integral, swath profiles, normalised concavity steepness (ksn), drainage basin shape index (Bs), asymmetry factor (AF), mountain front sinuosity (Smf) and the ratio of valley floor width to valley floor height (Vf).After remote sensing and geological analysis of the structural pattern, we propose that the SLR represents a horse-tail termination of the Palestina Fault that seems to have reactivated in the Miocene / Pliocene in a transpressive stress state, during the Andean Orogeny. Based on this structural model and the geomorphic indices, we divided the SLR into two regional domains: the Simití domain in the east and the Palestina domain in the west. The Simití domain is dominated by NE-SW striking structures with a right-lateral kinematic, whereas the Palestina domain is controlled by the N–S right-lateral Palestina Fault, which is the predominant structure in the SLR. We demonstrate that recent tectonic activity and higher uplift rates have been preferably constrained to the Simití domain, to the north of the Simití – San Blas faults, along the NE-SW striking faults. In this area, low Smf and Vf values suggest an active mountain front bounded by the reverse Morales Fault and Quaternary uplift rates between 0.05 and 0.5mm/yr. On the other hand, the Quaternary tectonic activity in the Palestina domain was concentrated in the northern portion, where climate has also played a significant role in controlling denudation rates and landscape evolution.The variable uplift pattern between both domains has induced along-strike changes in divide mobility and timing of drainage reorganisation within the SLR. Discrete capture events forced a west-southwest migration of the eastern side towards the western side of the SLR. The concentrated highest tectonic activity in the Simití domain progressively modified the topographic conditions and triggered the divide migration event.Our findings provide new and valuable information on the active tectonics and Neogene to Quaternary landscape evolution in this poorly studied area in the Northern Andes.