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

In 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. Plain Language Summary: Deformation within fold‐and‐thrust belts occurs as thrusting (displacement along fracture zones), folding (bending of rock units), and internal deformation. The internal deformation, like compaction and grain realignment, is hard to analyze by the naked eye. Fortunately, the magnetic properties of grains can be measured and provide information on grain realignment within an imbricate structure. In this study, we combine analog modeling with magnetic analysis to track the internal deformation of imbricates in detail. We modeled thrust imbricates and analyzed the magnetic fabric within the models. Our observations show a gradual change in magnetic fabric within an imbricate toward thrusts and kinkzones, which bound the imbricate, showing increasing deformation. At the thrusts, the magnetic fabric becomes parallel to the thrust surface and depicts the geometry of the thrust, whereas in the kinkzone a complex interplay between folding and thrusting is revealed. Our results can be compared to natural examples, as observations from models and published natural analogies are comparable. Our study provides insights into the strain distribution and gradients within thrust imbricates. Key Points: Anisotropy of magnetic susceptibility as strain indicator within three analog models simulating thrust imbricate developmentCharacteristic sets of magnetic fabric are developed for each structure in the models, revealing deformation in detailGradients in changes in magnetic fabric are recognized as function of distance toward a thrust or kinkzone [ABSTRACT FROM AUTHOR]