Analogue Modelling for Geology

Hello, we are Florian Lecareux, Nicolas Maitre, Raphaël Masset, and Fabio Peluso. We are students at UniLaSalle Beauvais, France, majoring in geology. As part of the geology technician and engineer cycles in the 3rd year, we chose a thesis on the realization of geological models for educational purposes. But how to make a simple representation of small-scale tectonic phenomena? To realize this, the phenomenon itself must be studied, its lithology and its deformations. A deformation is firstly all displacement of matter resulting from forces affecting surfaces called stresses. Depending on the type of material affected the reaction will differ. With the increase of the stress the deformation is first elastic then plastic and finally brittle. It is this brittle deformation, especially that caused by extensive stress, which lead this thesis. When brittle deformation appears, other deformation phenomena may occur such as fault striae, tension gash, or drag fold. All these deformations are a clue to the geodynamic context which create these stresses. Knowledge of the direction and magnitude of these stresses is essential to start modeling. Subsequently, the knowledge of the formation time, the mass and the dimensions of the deformed body make it possible to apply a downscaling to size the model. The downscaling allows to create a similarity between the reality and the model so that all the conditions are united to reproduce the desired phenomenon. For a deformation conforming to the tectonic phenomena and especially observable on a macroscopic scale, the reduction factor must be skillfully modified according to the analogue materials used. An experiment on different analogous materials is then made to compare the deformations and approach the reality. Knowledge of the mechanical properties of materials is necessary. These experiments make it possible to determine the behaviors of the materials in face of these scales reductions. If their behavior is similar to reality the conditioning in the model should result in conform deformations. In this project CATIA was used to design models destined to contain analogue material, in order to reproduce at a reduced scale the mentioned geological structures. One of the models is designed in a compact way in order to ease it’s use in teaching, while the other one has a more classical but efficient sandbox fashion. Thank you.