Episodic orogenic front migration in the northern Andes: Constraints from low‐temperature thermochronology in the Eastern Cordillera, Colombia

Abstract

New thermochronometric data from the Eastern Cordillera of the Colombian Andes reveal diachronous exhumation associated with Cenozoic contractional deformation in this sector of the northern Andes. We present a comprehensive account of exhumation patterns along a 150‐km‐long, across‐strike transect between ∼4° and 6°N by integrating 29 new apatite fission track (AFT) ages and 17 new zircon fission track (ZFT) ages with sparse published thermochronological data from this area. Our data reveal episodic eastward migration of the orogenic front at an average rate of 2.5–2.7 mm/a during the Late Cretaceous‐Cenozoic. We identify three major stages of orogen propagation: (1) slow propagation (0.5–3.1 mm/a) until early Eocene; (2) rapid orogenic advance (4.0–18.0 mm/a) during middle‐late Eocene, which accounts for ∼86% of the orogen's present width; and (3) slow orogen propagation (1.2–2.1 mm/a) from Oligocene to Holocene times. Our data demonstrate that in the course of changes in plate kinematics, the presence of inherited crustal anisotropies, such as the former rift‐bounding faults of the Eastern Cordillera, favor a nonsystematic progression of foreland basin deformation through time by preferentially concentrating accommodation of slip and thrust loading along these zones of weakness.