Influencia de cuerpos discordantes de distinta cohesión en la geometría estructural de fajas plegadas y corridas: aproximación sobre la base de un modelamiento analógico

Abstract

Lithological heterogeneities in a rock series deformed by the development of a fold-and-thrust belt (FTB) affects the pattern of the resulting structures. We present a series of analogue experiments to determine the effect caused on the deformation pattern of a FTB by the presence of cohesive bodies, like plutons or basement blocks that oppose greater resistance than the host rocks to contractional deformation. The influence of these bodies on the deformation pattern of the FTB was studied by incorporating discordant bodies with different cohesions within a stratified granular sequence with negligible cohesion. We describe two sets of experiments in which the inserted body presents low (Co1) and high (Co2) cohesion respectively. The experiments show a tendency of the structural pattern to curve around the inserted body and to migrate towards the deformation front or the foreland, even when the cohesive body is not exposed. In the first case (Co1) the thrusts cut across the cohesive body, while in the second one (Co2) the cohesive body is not faulted, but transferred towards the deformation front along a basal detachment. Comparison of these results with natural examples at different scales shows a high degree of coincidence in the structural patterns recognized in both cases. Two of the main characteristics of these patterns are the tendency of the thrust faults traces to avoid the cohesive body and adopt the geometry of its distal edge. In order to explain curvatures in natural structural patterns in fold-and-thrust belts, we suggest consider the presence of unexposed bodies with higher strength than their environment.

Designing Low-Cost Open-Hardware Electromechanical Scientific Equipment: A Geological Analogue Modeling Sandbox

“…The mobile wall of most of the sandboxes from the literature is driven by a piston placed outside of the sandbox (Fig. 1), as we inferred in view of their drawings [15], [28]- [31], [34], [35], [37]- [39], [45]. Although, it is basically the same mechanical principle, having the mechanic components under the base reduces the size of the ensemble.…”

“…The most detailed information of a scientific sandbox we have found is the work of Acevedo et al [34] which have been further described in the thesis of Villarroel [35]. These contributions unveil the model of the servomotor and the software that controls it; and also include mechanical drawings, the materials and characteristics of the leadscrew and sandbox.…”

“…Although servomotors are more accurate and have better performance than stepper motors, we opted for the latter because servos are substantially more expensive. As an example, the servomotor and drive used in [34], [35] would be more expensive than the total cost of the all the components of the proposed Sandbox.…”