Characterization of the Soapaga Fault deformation in the central part of the Eastern Cordillera, Colombia

Abstract

The eastern border of the Floresta Massif is characterized by the confluence of the Soapaga Fault and the Corrales Fault, two reverse faults that are linked to each other in a simple transfer zone and whose deformation influenced the formation of the Betéitiva Syncline. The Betéitiva Syncline, located on the Soapaga Fault footwall, shows geometric features, such as upright to inverted backlimbs and thickness changes related to the fault's deformation. However, none of the previously proposed kinematic models (fault-propagation, fault-bend, and buckling–folding models) clearly explain the evolution of the Betéitiva Syncline related to the Soapaga Fault or the differentiation between this fault and the Corrales Fault. In this work, we developed a structural analysis to differentiate the Soapaga Fault from the Corrales Fault through a detailed description of the fault zones, geomorphic evidence, geometric relationships, and deformation features related to each fault. Then, we developed a structural analysis of the evolution of the aforementioned structures using five balanced cross-sections that illustrate how they are related to one another. Three kinematic models or structural processes were used to explain the evolution of the study area: the trishear fault-propagation fold model, the fault-propagation fold model, and the gravitational fold and fault model. This work presents the structural, geological, and geomorphic evidence that allowed us to differentiate the Corrales Fault from the Soapaga Fault. Additionally, our results show an increase in the Soapaga Fault displacement (4.7 km–9.5 km), the Corrales Fault displacement (0.6 km–1.3 km), and the total shortening (1.9 km–3.4 km) from north to south. In addition, we propose a structural evolution model that better explains the geometric features of the Betéitiva Syncline regarding the deformation of the Soapaga Fault, which requires 10x less shortening than previous structural models. Finally, we propose that the deformation of the Soapaga Fault is a scale-dependent variable because of the relationship that this fault has with regional structures, such as the Floresta Anticlinorium, but also with local structures, such as the Betéitiva Syncline.