Effects of inherited structures on inversion tectonics; examples from the Asturian Basin (NW Iberian Peninsula) interpreted in a computer assisted virtual environment (CAVE)

Two outcrops in the Asturian Basin (northwest Iberian Peninsula) composed of Lower-Middle Jurassic alternations of limestones and marls, including black shales proven to be hydrocarbon source rocks, were analyzed from a structural point of view. In both outcrops, an inversion tectonic event of Cenozoic age caused contractional folds and faults, as well as a change in the structural style up section, superimposed on previous Mesozoic extensional structures. However, the mode and kinematic evolution of the inversion tectonics were very different; folding predominated in one of the outcrops, whereas faulting is the most important phenomenon in the other one. The characteristics of the two coastal outcrops (irregular surface, inaccessible portions, accessibility restricted to low tide periods, good quality of rock exposure and scale) led us to build virtual outcrop models using photogrammetry (structure from motion) and interpret them in a computer-assisted virtual environment (CAVE). The analysis of both field data and the virtual outcrop model-derived results (three-dimensional models and cross sections) allowed us to conclude that mechanical stratigraphy and the type, characteristics, and distribution of previous structures were the key factors that controlled the inversion tectonic mode. Awareness of their influence should help when trying to understand inversion structures in similar geological settings.