Thermal and Kinematic Evolution of the Eastern Cordillera Fold and Thrust Belt, Colombia

Abstract

We modeled the kinematic evolution of two regional-scale transects through the Eastern Cordillera fold and thrust belt of Colombia and then calculated the conductive thermal state of key steps of the kinematic history using Thrustpack 4.0. The models were constrained by well, seismic, apatite fission-track, and thermal-maturity data. The main compressional structures in the Cordillera are controlled by Jurassic–Early Cretaceous normal faults of the Bogot, Cocuy, and the paleo-Magdalena basins. The location of these Mesozoic extensional features strongly influenced thermal evolution. Although shortening and basin inversion started in the early Tertiary, the bulk of the deformation occurred during the Miocene to Holocene Andean orogeny. Rocks in different structural positions in the thrust belt have distinct thermal and maturation histories that determine the timing of hydrocarbon source rock maturation and the quality of sandstone reservoirs. The internal part of the Cordillera had high heat flow, with peak sedimentary burial and peak maturation during the Oligocene flexural phase. Local structures formed during this time and were followed by major uplift and denudation during the Andean orogeny. Hydrothermal circulation of basinal fluids, which was probably expulsed at the onset of structural inversion, led to extensive cementation of Albian reservoirs. In contrast, the Llanos foreland is characterized by continued flexural subsidence and syntectonic sedimentation up to the present time. Thermal maturation results from the combination of syntectonic sedimentation and tectonic burial. Quartz cementation appears to be linked to the appearance of abundant silica in the system from pressure solution during Andean shortening. The thermal regime of the western flank of the Cordillera is cooler than the interior of the range, whereas the structural history is more complex. Along our transect, an active kitchen is located in the west-vergent thrust belt of the Eastern Cordillera. In the Magdalena Valley, there are local kitchens only where a thick stratigraphic section is preserved. The main limitations of our thermal models are (1) the lack of constraints on the thickness and timing of deposition of the Eocene–Oligocene flexural deposits, which are sparsely preserved in the Eastern Cordillera; (2) the paucity of good-quality thermochronologic data to constrain the timing of erosion and rates of fault motion; and (3) the difficulty in modeling the effects of fluid circulation over this large and structurally complex region.