Neogene uplift of the Chiribiquete tabletop mountains in the Colombian Amazon and its paleobiogeographic implications

The Chiribiquete Mountains (Colombian Amazon) are a tepui-like (tabletop) mountain range. Here, we investigate the timing of surface uplift using regional geological data, analysis of sedimentary deposits within and near the mountains, and topographic analysis. We find that Early Miocene fluvio-lacustrine deposits of Andean provenance occur westwards of the Chiribiquete Mountains, whereas eastwards, fluvial deposits of Amazon Craton provenance occur. Onlap of Early Miocene deposits against the Ordovician basement rocks of the Chiribiquete Mountains, in combination with our provenance data, suggests that a proto-Chiribiquete Mountain chain existed by the Early Miocene. Reactivation of inherited basement faults since the Late Miocene likely led to increased surface uplift. Topographic analysis indicates the Chiribiquete Mountains tilt southwards, similar to, but with a higher tilt angle than neighbouring Early Miocene deposits. Based on the assumption that ~100 m of regional uplift of the Vaupés Arch, the tilting of the foreland deposits, and the local tilting of the Chiribiquete Mountains are coeval, we infer that the majority of surface uplift was achieved since the Late Miocene due to compression associated with Andean Mountain building. Regional uplift and/or Amazon drainage integration have since incised Early Miocene sediments by ~50 m, carving the characteristic terra firme plateaus between rivers. Thus, a low topographic barrier existed during the Early Miocene, which was significantly amplified since the Late Miocene. This implies that the origins of the modern tepui-like biome of the Chiribiquete Mountains date back to the earliest Neogene (or older), forming an exciting basis for further paleobiogeographic studies.