Investigating the influence of climate on the evolution of fold-and-thrust belts in Chinese Tianshan: A 2D doubly vergent numerical model approach

Abstract

In most analogue and numerical modelling studies for investigating the evolutionary mechanisms of fold-and-thrust belts, the initial models are typically designed as “sandboxes” with one side fixed in the horizontal direction. However, such model setup has neglected the potential effects of drainage divide migration. To address this issue, in this study we developed a 2D doubly vergent numerical model that accounts for drainage divide migration to investigate the structural evolution in Tianshan fold-and-thrust belts since the late Cenozoic, with an emphasis on the influences of climatic forcing on rock deformation. The deformation styles of northern and southern Tianshan fold-and-thrust belts exhibit significant differences, with the northern Tianshan fold-and-thrust belt characterized by deep isoclinal anticlines, whereas the southern Tianshan fold-and-thrust belts are dominated by thrust faults and minor shallow-level tight anticlines. Our modelling results suggest that such differences in deformation style may be attributed to the north–south precipitation gradient across Tianshan mountain. The results also show that unilateral climatic perturbations can lead to migration of the drainage divides towards the side with lower precipitation, thereby impacting the structural evolution on the opposite side of the mountain range. Such impact mainly manifests as an increased tendency to develop more thrust faults in the direction toward which the drainage divide is shifting. This provides a new perspective for reevaluating the patterns of tectonic evolution in the global orogenic belts since the late Cenozoic.