Abstract
The Yariguíes Anticlinorium, a regional structure located at the western flank of the Eastern Cordillera of Colombia, includes the thickest record of continental sedimentary rocks accumulated near to the Jurassic-Cretaceous boundary. The sedimentary rocks are lithoarenites and feldspathic arenites, grouped in the Girón Formation, and deposited in a Late Jurassic extensional basin interpreted in this work as a rift basin. We analysed the sedimentologic and compositional characteristics of two sections that accumulated in a complex rift system. We identified important thickness variations, from 3,350 m in the type section to at least 525 m in a reference section in the Zapatoca area, as well as petrographic and lithofacies changes. This led us to confirm that the Girón Formation encompasses all the continental facies, whose source rock correspond mainly to the exhumed blocks of the Santander Massif during the Late Jurassic. The synrift successions were segmented by transverse structures and regional longitudinal faults of the rift-shoulder, as the Suárez Fault. The tectonic frame of the study area shows the relevance of the W-E compressional regimes, explaining the local kinematics as a heritage of the former configuration and tectonic inversion of the basins. However, clockwise rotation of the stress field was detected from the stress tensor analysis. The latest orientation of the stress tensors and shear joints are related to the effect of the transpressional Bucaramanga and Lebrija faults along the study area.
Highlights
The Jurassic stratigraphy has been a long-debated subject in the Colombian geological literature
The geology of the northern part of the Yariguíes Anticlinorium is presented in figure 2 (YR in Fig. 1) as bordered by the Suárez Fault to the east, and the thrust fault system led by the San Vicente Fault to the west (Fig. 3)
It is important to note the effect of the Suárez Fault and other longitudinal faults within the Yariguíes Anticlinorium configuring the structural style of the area (Figs. 2 and 3)
Summary
The Jurassic stratigraphy has been a long-debated subject in the Colombian geological literature. One clear example of these issues is the unique nature of the type section of one of the most well-known Upper Jurassic sedimentary units: the Girón Formation This type section is different in fundamental stratigraphic aspects (e.g., thickness, architecture and facies successions) from all the other similar aged successions, precluding valid regional correlations. Units with similar characteristics to those of the Girón Formation are reported in Mexico for the Middle Jurassic (e.g., Todos Santos Formation, Huizachal Formation) They are interpreted as the infilling of extensional basins (Michalzik, 1991; GodínezUrban et al, 2011) located adjacent to the limit between Laurentia and Gondwana during Pangea’s rupture, in the Middle-Late Jurassic (Martini and Ortega-Gutiérrez, 2016; Nova et al, 2019). Other studies try to conciliate all the geological data into different plausible tectonic models but lack a detailed scenario of each of the involved units (e.g., Martini and Ortega-Gutiérrez, 2016; Bayona et al, 2020)
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