EROSION RATES AND TOPOGRAPHY ELUCIDATE SPATIAL VARIATION IN TECTONICS ALONG THE NORTHERN ANDES OF COLOMBIA (Invited Presentation)

Understanding interactions between topography, climate, and erosion in modern mountains is fundamental to decipher the deep-time evolution of landscapes, climate, and biodiversity of the Earth. The obliquely convergent Northern Andes (0.5–3.5°N) are an ideal setting to understand how along-strike differences in rock uplift rate affect erosion rates and the evolution of topography through a combination of topographic analysis, cosmogenic nuclide data and previously published thermochronology data. Cosmogenic nuclide-derived erosion rates are ~3–5 times higher along the southern and northern section of the Eastern Cordillera compared to central part. The pattern and magnitudes of erosion rate data matches published thermochonrologic exhumation rates, and is consistent with structural data. Zones of dominant thrusting experience higher erosion rates compared to zones with dominantly strike-slip deformation. The agreement between cosmogenic nuclide-derived erosion rates and exhumation rates from thermochronology suggests that exhumation has been relatively steady over the past ~3 Ma. Along-strike differences in erosion and exhumation rate coincide with variations in channel steepness, local relief, and maximum elevation, which we interpret as the result of variations in rock uplift along orogen-bounding thrust faults. Nonetheless, we attribute the more subtle magnitude of along-strike change in river steepness and maximum elevation to the increase in erosional efficiency with increasing erosion rate. The Andes of Colombia provide a clear example of how along-strike differences in the rates of rock uplift can lead to gradients in topography and erosion rate.