Balanced cross‐section restoration in a complicated folded hinterland structure: Shilbilisaj profile, Talas ridge, Caledonian Tien Shan

Abstract

AbstractConventional cross‐section balancing techniques based on layer length measuring can be applied only for foreland structures. To analyse complicated hinterland structure with numerous small‐scale folds, this balancing technique requires the reliable and detailed tracing of the morphology of any layer throughout the cross‐section, which is unattainable. We present a special kinematic method of balancing cross sections based “on the geometry of the folded domain” which enables the structural restoration of hinterland regions. We apply the method to restore the detailed structural section along the Shilbilisaj River, having a length of 26 km. We divided this section into 40–60 so‐called “domains” each including 2–7 folds. Our method uses the fold's morphology to determine the strain ellipsoid, which describes the deformation of each domain and is used to restore its pre‐folded state. By combining the pre‐folded states of the domains, we reconstruct the entire profile, and calculate shortening values as K = L0/L1 (initial to final length). The overall shortening value for the profile is 4.49, incrementally varying along the section from 3.79 to 5.53. The comparable results of two independently performed reconstructions emphasize the reliability of the applied balancing method.