Effects of sidewall friction on the structural style and deformation evolution of fold-and-thrust belts: Analog modeling results

Abstract

The influence of sidewall friction on the deformation styles of fold-and-thrust belts has long been a popular topic in earth science; however, systematic analog modeling studies are limited. Therefore, this study conducted seven groups of sandbox experiments to investigate the effects of sidewall friction on deformation under different plate motion modes, such as backstop movement, basal plate movement, and sidewall movement, and configurations in which sand near the sidewalls was removed using a vacuum cleaner. The results reveal the following: (1) Even when the sidewall friction coefficient is constant, different plate motion modes result in distinct structural deformation styles. (2) The formation of arcuate fold-and-thrust belts in nature is a common phenomenon by sidewall friction. (3) The substantial difference in deformation patterns between the central and boundary regions of the tectonic zone is due to sidewall friction. Forethrusts, backthrusts, and symmetric pop-up structures often form in the central region of the deformation zone. In contrast, in the boundary region near the sidewall, the main structural styles are forethrust and backthrust faults, resulting in a relatively simple deformation pattern. (4) The deformation patterns of the Himalayan frontal thrust, the Indo-Burma accretionary wedge, and the internal structural variations of the Salt Range of Pakistan may be related to sidewall friction on both sides of the overriding plates.