Erosion rate maps of the Northern Andes highlight spatio-temporal patterns of uplift and quantify sediment export

Abstract

Erosion rates are commonly used to study tectonic uplift and sediment export from mountain ranges. However, the scarcity of erosion rate data often hinders detailed tectonic interpretations. Here, we present 25 new erosion rates from the Northern Andes of Colombia, determined from cosmogenic 10Be measurements, to study spatial and temporal patterns of uplift along the Central and Eastern Cordillera. These rates, along with published data and precipitation-corrected normalized channel steepness measurements, were used to create high-resolution erosion rate maps. The results show that the southern Central Cordillera has relatively uniform erosion rates, averaging around 0.3 mm/a, while the northern Central Cordillera exhibits rapidly eroding canyons dissecting slowly eroding low-relief surfaces. We interpret that long-term, steep slab subduction has led to an erosional steady-state in the southern Cordillera Central, while Late Miocene slab flattening caused an acceleration in uplift in the northern Cordillera Central which the landscape has not yet adjusted to. The Eastern Cordillera also displays pronounced erosional disequilibrium, with a slowly eroding central plateau rimmed by faster eroding western and eastern flanks. Our maps suggest recent topographic growth of the Eastern Cordillera, with deformation focused along the eastern flank, which is also supported by balanced cross-sections and thermochronologic data. Spatial gradients in predicted erosion rates along the eastern flank of the Eastern Cordillera suggest transient basin-ward migration of thrusts. By using our erosion maps to estimate sediment fluxes, we find that the Eastern Cordillera exports nearly four times more sediment than the Central Cordillera. Our analysis shows that accounting for spatial variations in erosion parameters and climate gradients reveals important variations in tectonic forcing that would otherwise be obscured in traditional river profile analyses. Moreover, given relationships between tectonic, and topographic evolution, we propose that the dynamic landscape evolution of the Northern Andes, as revealed by our erosion maps, is primarily linked to spatial and temporal variations in slab dip, with potentially additional influences from inherited Mesozoic rift structures.