Magnetic Fabric Signature within a Thrust Imbricate; an analogue
modelling approach
Abstract
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.