Meso-Cenozoic Tectonic Evolution of the Kexueshan Basin, Northwestern Ordos, China: Evidence from Palaeo-Tectonic Stress Fields Analyses

Yongzhi Cheng,Rui Gao,Wenhui Li,Zhanwu Lu,Hao Chen,He Su,Rubing Han

doi:10.3389/feart.2022.845475

Yongzhi Cheng, Rui Gao + Show 5 more

Open Access

https://doi.org/10.3389/feart.2022.845475

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Abstract

The Kexueshan Basin in the western Ordos Block is characteristic of typical regional superimposed folds in the Jurassic strata, documenting the main tectonic shortening since the Mesozoic. Field structural investigation, fault kinematic analysis, together with regional structural analysis, we reconstruct two-phase tectonic stress fields related to crustal shortening. Synthesizing the regional structural analysis and geochronology, two stages of tectonic evolution are proposed in the Kexueshan Basin since the late Mesozoic. In the mid-late Middle Jurassic (J2), controlled by NW-SE compaction, NW-SE structures formed in the Kexueshan Basin on the western margin of the Ordos Block, marked by NE-to NNE-trending folds and thrust faults. Growth strata found in the study area constrain the starting time of the NW-SE structures. This shortening is likely related to a combination of the southward convergence of the Siberian plate and the northwestward subduction of the Pacific plate. In the end Cenozoic (N12-N2), the tectonic stress field was transformed to NE-SW compression, resulting in the development of NW- to NNW-trending fold structures, which were superimposed on early NE-to NNE-trending structures to produce regional superimposed folds. The tectonic shortening coincided with the northeastward growth of the Tibetan Plateau.

Highlights

As an important tectonic boundary in the western part of the North China Craton (NCC), the western marginal structural belt of the Ordos Block (OB) has attracted the attention of many researchers for a long time (Figure 1)
Combining regional structural analysis and deformation-affected stratigraphic characteristics, the two periods of deformation events can be determined to have occurred since the late Mesozoic
This paper proposes a tectonic evolution model of the western margin of the Ordos Block since the late Mesozoic (Figure 12)

Summary

Introduction

As an important tectonic boundary in the western part of the North China Craton (NCC), the western marginal structural belt of the Ordos Block (OB) has attracted the attention of many researchers for a long time (Figure 1). In previous studies, this belt has been named the “Longxi System” and “the spine of the Qilian-Lvliang-Helan mountain-shaped structure” (Li, 1954), the Helan-Liupan fold belt (Ma et al, 1961), and the Ordos platform fold belt (Huang, 1983). Liu et al (1997) proposed an unrestricted lateral extrusion structure model through the north-south structural difference in the western margin, which was reasonably explained from the perspective of structural geology and dynamic mechanism (Liu and Yang, 1996; Liu and Yang., 1996; Liu and Yang, 1997; Liu et al, 2013)

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