Estudio del campo de velocidades de un pliegue por despegue a partir de un modelo análogo

Abstract

To analyze the development of adetachment fold and obtain the velocity field during the compression, ananalogous model was carried out. This model tries to reproduce in a simplifiedway the conditions under which this type of folding occurs. Paper sheets wereused to simulate a material with fragile behavior, placed on a base composed ofa material with greater cohesion to resemble the nature of evaporate or shalerocks that tend to be more ductile. As the structure is formed, photographs weretaken on both sides to follow the evolution of the fold. These photographs wereprocessed and analyzed with the PIV-MATLAB program to obtain the kinematicvectors that represent the velocity field. Based on our analysis, in the first zone of the structure there is a strongdomain of the horizontal component, where the movement of the particlespredominates in the direction imposed by the motor. Upon reaching the first axialsurface, the movement of the particles begins in the zone dominated by therising of the anticline flank. In this area are the highest values ofhorizontal velocity for the early stages of construction of the fold. The lifting of the limb requiresprogressive movement of rock particles in the vertical direction. As progressis made in the construction of the fold, the velocity field rotates,displacement along the horizontal direction becomes smaller while the amount ofvertical movement increases. In this way the hinge is built and gains height,while the wavelength of the structure remains constant. In moreadvanced stages of the anticlinal evolution towards the interior of the areadelimited by the axial surfaces, the vertical component dominates. This resultsin an upward migration of the particles that allows the conformation of thehinge area of the detachment fold.