THE EASTERN CORDILLERA IS A COMPLEXLY DEFORMED FOLD-THRUST BELT WHICH WAS UPLIFTED AND EXHUMED FROM THE OLIGOCENE TO PRESENT AGE

Yopal city is located in the Foothills province between the Eastern Cordillera and the Llanos foreland basin in Colombia. The Eastern Cordillera is a complexly deformed fold-thrust belt which was uplifted and exhumed from the Oligocene to Present age. Surface thermochronological studies indicate that exhumation of the Eastern Cordillera began in the Late Miocene (10 Ma) and continues to the present. Previous structural interpretations of the subsurface include a triangle zone, an antiformal stacked duplex, and footwall short-cut faults. However, this still unclear and difficult to determine the geological configuration of the subsurface based on seismic interpretation. The timing of the deformation and movement of each thrust sheet is the objective of this study. A balanced cross section from interpretation of 3D seismic reflection data, 15,298 surface subsurface dips from dip meters, surface outcrop maps, gravity and magnetic profiles, and integration of seven vitrinite reflectance (Ro) and thermal alteration index (TAI) results from samples picked from well at depths between 4 and 5 km were used for thermal inversion modeling in order to understand the burial history of each thrust sheet. Inversion modeling consists of estimating the burial depth using the Ro values measured in the microscope through the Augur chart and level of organic in order to calculate the effective heating time in millions of years for the vitrinite reflectance (time that the rock samples was heated as a result of overburden loading, thrusting or/and basement uplift). From the Effective heating time, the burial temperature were subtracted from Hood chart. Ro values from core samples range from 0.60 to 1.11 and TAI values range from 2.6 to 3.0 and show: 1) maturity in the 5-7 km depth range of the deeper thrust sheets of the Eocene Mirador Formation and Paleocene Barco Formation; and 2) reveal that the maximum paleotemperature reached in the thrust stack was 180°C. A balanced cross sections across show: 1) a 7-8-km-deep detachment level of the Guaicaramo fault in the Cretaceous Fomeque formation; 2) a detachment level in the Paleocene Los Cuervos Formation of the Pauto thrust sheet inside of a triangle zone; and 3) the presence of the Cretaceous Guadalupe and Paleocene Barco Formation’s sandstone in the Florena thrust sheet.