Tectonically driven drainage reorganization in the Eastern Cordillera, Colombia

High-elevation plateaus that are positioned in between topographic barriers are common orogenic features in
the South American continent, formed under a range of evolving environmental conditions. For example, in
the central Andes (Bolivia-Argentina), the Puna-Altiplano is arid and endorheic with a poorly developed fluvial
system, while in the northern Andes (Colombia) the Chiquinquirà and Tunja highlands are characterized by a
humid equatorial exorheic fluvial system. In addition to a plateau-like low-relief surface at 2500 m, the landscape
of the northern Eastern Cordillera and SantanderMassif (northern Colombia) displays a lower elevation (~1500m)
low-relief landscape (Mesas) comprising river captures, windgaps, and a disconnected alluvial fan that collectively
record a transient state. This configuration has been achieved through a combination of compressive deformation
and sub-crustal processes. The compressive shortening started to occur in the Paleogene and is still active, whereas
regional surface uplift related to slab flattening andmantlewedge hydration startedintheLateMiocene/Pliocene.To
disentangle the crustal vs sub-crustal forcing and to investigate the relative timing of drainage network evolutionwe
combine the analysis of topography, hydrography (river longitudinal profiles, morphometric parameters, drainage
divide stability), knickpoint migration (celerity model), paleo-longitudinal profile modeling, satellite images, and
field observations.
In particular, we show that during the development of the low-relief Mesas landscape the older Chiquinquirà
highland was a closed drainage and that the lower portion of the Suárez River flowed northward into the Bucaramanga
depression forced by the Los Cobardes Anticline topographic barrier. The Suárez River collected waters
from the southern SantanderMassif and the upper reach of the Chicamocha River, which was draining the Tunja
highland. An abandoned windgap deposit on the eastern edge of the Mesa de Barichara suggests that the lower
portion of the Chicamocha Riverwas not yet formed. Subsequent to the Chiquinquirà highland drainage opening,
two main tributaries of the Magdalena River, the Lebrija and Sogamoso, captured the Suárez River in a short temporal
sequence. A knickpoint celerity model allows us to date the Lebrija capture of the Bucaramanga depression
at ~260–270 ka and the subsequent Sogamoso capture at 190–220 ka. Only during this final stage, the lowermost
Chicamocha River section formed and the drainage network developed to its present configuration.
Finally,we suggest that the early Cenozoic rift inversion has controlled the drainage network pattern and the late
Miocene sub-crustal-induced surface uplift has driven the main fluvial network reorganization.