Cenozoic Evolution of the Eastern Colombian Andes: a New Perspective from Thermokinematic Modeling and Quantitative Detrital Geochronology

Abstract:

The reconstruction of the kinematic evolution of the northern Andes in Eastern Colombia reveals two main stages of orogenic development, each one displaying a different dominant factor controlling mountain building. In a context of oblique arc-continent convergence associated to dextral shearing along the Caribbean-South American plate boundary, the Late Cretaceous to late Miocene growth of the Andes in eastern Colombia was mainly modulated by the location of inherited basement anisotropies that constituted normal faults in the early Mesozoic. Shortening budget reconstructions show that the main exogenous driver for this first stage of Cenozoic deformation is the Oligocene increase in westward drift of the South American Plate. A second stage is characterized by thick-skinned basement uplift occurring at peak rates in the last ~5 Ma. This rapid uplift has led to the main topographic construction and the ensuing orographic precipitation favoring enhanced erosion in the eastern Andean watersheds, which in turn has potentially triggered positive tectonic-climate feedbacks. Thermokinematic modeling of detrital apatite fission track and apatite and zircon (U-Th)/He data suggest that up to 50% of the shortening along the main frontal reverse fault that bounds the Eastern Cordillera to the east occurred in the last ~2 My. This Cenozoic portrait of orogen evolution results from the detailed reconstruction of the upper crustal architecture and deformation kinematics enabled by the integration of (1) surface mapping and subsurface geology based interpretation of industry seismic reflection data, (2) a new detailed biostratrigraphically constrained chronology of foreland basin sediment accumulation, (3) the evolution of sediment source areas based on the quantitative comparison of various sedimentary provenance proxies, mainly detrital zircon U-Pb, and (4) thermokinematic modeling of a multi-method thermochronometric extensive database using our own software development.