Cenozoic deformation of the Weihe Graben in central China: Insights from Analogue modeling

Abstract

The Weihe Graben is located in the composite area of the Tethys-Himalayan tectonic and circum-pacific tectonic domains and is an essential structural feature related to Cenozoic intracontinental deformation. However, two different hypotheses, sinistral strike-slip, and extensional mechanism, are proposed for the origin of this graben. In this study, we designed crust-scale analog models based on fault kinematics to better understand the deformation and dynamic mechanisms of the Weihe Graben. Fault kinematics shows early sinistral strike-slip and NW-SE extensional deformation and late NE-SW, S-N, and NW-SE extensional deformation. Our experimental results reveal that Model C1 (sinistral strike-slip + NW-SE extension) is the most similar to the geological structure of the Weihe Graben in the Paleogene. Furthermore, the NE-SW extension results in two larger subsidence areas in the northeast and southwest of the basin, similar to the formation of the two depressions during the Miocene. The S-N extension causes the basin to expand southward and northward, consistent with the sedimentary characteristics of Weihe Graben in the Pliocene. The NW-SE extension leads to relatively strong fault activity in the northwest and southeast of the basin, resembling the active fault characteristics since the Quaternary. Therefore, we propose that the Weihe Graben formed by a strike-slip and extensional combined mechanism in the Eocene-Oligocene, influenced by the far-field effects of the Indian-Asian collision and crust-mantle processes triggered by the stagnant paleo-Pacific plate. Subsequently, during the Neogene-Quaternary, the graben’s development shifted towards an extensional regime under the influence of the eastward extrusion of the Tibetan Plateau.