Transpression and the build-up of the cordillera: the example of the Bucaramanga fault (Eastern Cordillera, Colombia).

Widespread wrench tectonics has been described along the Northern Andes. The Bucaramanga fault, described as sinistral strike-slip, bounds the high Santander Massif. We combine structural and thermochronologic data at the central-southern portion of the fault, in order to investigate the vertical displacement.

Structural survey data shows: 1) old phases of activity preserved in the host rocks along the fault trace, with superimposition of different slickenlines generations; and 2) both strike- and dip-slip kinematics indicators. New and previous thermochronologic data show that differential exhumation of the fault walls has been ongoing from 50 Ma. The hangingwall, the Santander Massif, records: 1) in the central portion, decreasing exhumation rates from the early Miocene to the middle–late Miocene; and 2) in the southern portion, constant rates through the Late Oligocene to the Pliocene. Combining such observations, the thermochronologic offset resulting from the relative motion of the two fault walls is comparable with the observed elevation drop across the fault, suggesting that the present topography of the Santander Massif is related to the vertical movement along the Bucaramanga fault. We infer that the fault has a significant Neogene reverse component, consistent with present-day horizontal GPS vector data, long-term exhumation rates and the structural assemblage.