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Magnetic Fabric Signature within a Thrust Imbricate; an analogue modelling approach
  • Thorben Schöfisch,
  • Hemin A. Koyi,
  • Bjarne Almqvist
Thorben Schöfisch
Uppsala University

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Hemin A. Koyi
Uppsala University
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Bjarne Almqvist
Uppsala Universitet
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In this study, we report results from three analogue models with similar initial setup and different amounts of bulk shortening, to simulate a development of a pop-up structure in fold-and-thrust belts at different stages. Samples are taken in different places of the deformed models for analysis using anisotropy of magnetic susceptibility. Shortening of the models resulted in the formation of a pop-up structure, which is bounded by backthrust(s) and complex forekink zone(s). Several forethrusts at different degrees of maturity developed in front of the pop-up structure. Three distinct types of magnetic fabric can be identified throughout the models: (i) a compactional oblate fabric that changes as function of distance towards a localized deformation zone (e.g., thrust or kinkzone), (ii) a thrust-induced fabric with magnetic foliation parallel to the thrust surface, and (iii) a complex forekink zone fabric with broad girdle distributions of principal axes and magnetic lineation perpendicular to shortening direction. The latter indicate interplay between folding and thrusting of the shortened sand layers. Additionally, a decrease in degree of anisotropy with appearance of a quantitatively more prolate fabric can be observed towards the thrusts and kinkzones. Additionally at thrusts, a variation in strain is reflected by the magnetic fabric and can be inherited in a thrust-induced fabric. In conclusion, strain is changing as function of distance towards localized deformation zones with characteristic fabric, and differences in magnetic fabric are distinct between data away and within deformation zones as deformation zones mature.