Magnetic Fabric Signature Within a Thrust Imbricate; an Analog Modeling Approach

Abstract

AbstractIn this study, we report results from three analog models with a similar initial setup and different amounts of bulk shortening, to simulate the development of a thrust imbricate in fold‐and‐thrust belts at different stages. Samples are taken at the back‐ and forethrusts, in the complex forekink zones, and at random distances to thrusts for analysis using anisotropy of magnetic susceptibility as strain indicator. This analysis shows that three distinct types of magnetic fabric can be identified throughout the models: (a) a compactional oblate fabric that changes as a function of distance toward a localized deformation zone (e.g., thrust or kinkzone), (b) a thrust‐induced fabric with magnetic foliation parallel to the thrust surface depicting its geometry, and (c) a complex forekink zone fabric with broad girdle distributions of principal axes and magnetic lineation perpendicular to the shortening direction. The latter indicates an interplay between folding and thrusting of the shortened sand layers. Additionally, a decrease in the degree of anisotropy with appearance of a quantitatively more prolate fabric can be observed toward the thrusts and kinkzones. Moreover, a thrust‐induced fabric is inherited by the variation of strain, depicted by changes in magnetic fabrics. In conclusion, our analysis of model results shows that strain changes as a function of distance toward localized deformation zones with characteristic magnetic fabrics that develop as deformation continues.