Neotectonic movement in the southern margin of the Ordos Block inferred from the Qianhe River terraces near the north of the Qinghai–Tibet Plateau

Abstract

The Qianhe River flows between the Liupanshan Orogen and the Ordos Block, with the river valley controlled by the southern margin fault of the Ordos Block. Five asymmetrical terraces exist on the banks of the Qianhe River, which correspond to the five terraces of the Wei River. Each terrace is composed of alluvial deposits at the bottom beneath loess deposits, which are characterized by alternating loess (L) and paleosol (S) layers, with the basal layers of the loess deposits being S0, S1, S53, S8, and L15 from T1 to T5. The heights of the five terraces T5, T4, T3, T2, and T1 are 220 to 260 m, 130 to 160 m, 60 to 80 m, 20 to 30 m, and 8 to 10 m, respectively, above the present valley, and their ages are 1.2, 0.8, 0.5, 0.13, and 0.01 Ma, respectively. These ages are generally consistent with the several uplift periods of the Qinghai–Tibet Plateau in the medium and late stages. Therefore, neotectonic movement is the controlling factor of river terrace formation in the periphery of the Ordos Block. According to the south‐west movement of the river channel in the lower reaches of the Qianhe River, it can be estimated that the Ordos Block rotated about 20° counterclockwise in the Pleistocene.

New findings regarding the Fen‐Wei Graben on the southeastern margin of the Ordos Block: Evidence from the Cenozoic sedimentary record from the borehole

“…Then, at the end of the early Pleistocene, the lakes in Wei River–Lingbao Basin contracted (Li, Li, et al, 2015), and alluvial materials began to deposit along the river. From that point, the loess also has been accumulated on both sides of the river extensively (Chen, Fan, et al, 2018; Chen, Wang, & Lou, 2018). Additionally, the Linfen Basin also experienced significant atrophy (Chen et al, 2016), and the lake reduced and moved southwestward to the Sushui River sag, in where it still remained today.…”

“…Although numerous studies have been performed by scholars, there are still debates surrounding their evolutionary process and dynamic background for the complexity of their structure and the thick Quaternary sedimentary cover. The Wei River Basin and Linfen Basin have been considered to be connected and to form a unified basin known as the Fen‐Wei Graben (Chen, 1984; Chen, Fan, et al, 2018; Chen, Wang, & Lou, 2018; Cui & Li, 1986; Li, 1956; Liu & Gan, 1981; Sun, 1983; Xue, Li, & Liu, 2002; Zhang & Wang, 1982; Zhang, Guo, Gong, & Hui, 2012 and so on). There are two main views regarding the genesis of the Fen‐Wei Graben, one is related to Qinghai–Tibet tectonism (Bai et al, 2015; Li, Zhang, Guo, Zhang, & Zhang, 2005; Liu & Xue, 2004; Sun, 2005; Sun & Xu, 2007; Xing, Zhao, Tu, & Xing, 2005), and another concerns Pacific Plate tectonism (Huan, Shi, & Yan, 1982; Li, Hu, Zhu, & Lin, 2015; Sun, 1983; Wu et al, 2013; Zhang, 2011; Zhang, Ma, Yang, Shi, & Dong, 2003).…”

Fractal and Multifractal Characteristics of Lineaments in the Qianhe Graben and Its Tectonic Significance Using Remote Sensing Images

“…The NW-SE striking faults here mostly follow the course of the Qianhe River in the Qianhe Graben, from northwest to southeast in the study area. Topographically, the TGF, a normal fault, follows the boundary between the southwestern Ordos Block and Loess Platform (Figure 1) [44,45], and it cuts the Loess Platform deeply in the southeast Qianhe Graben, as characterized by straight lineaments in three-dimensional (3D) images [46]. Moreover, previous studies investigated the Quaternary activity of the QMF, displaying left-lateral slip in kinematics with rates ranging from 0.5 to 1.5 mm/year [46].…”

Climate change and tectonic implications during the Pliocene climate transition interval from lacustrine records in western Wei River Basin, central China

“…On a larger scale, the study area is located at the forefront of the northeastern extension of the Tibet Plateau and has experienced significant tectonic activities since the late Cenozoic (Chen et al, 2018; Li et al, 2018; Liu et al, 2016). The tectonic framework of the area is controlled by the Longxian–Baoji fault zone, which is composed of four NW and NNW left‐lateral normal faults and also belongs to the tail of the Haiyuan–Liupanshan fault zone (F1).…”