The tectonics of the western Ordos Plateau, Ningxia, China: Slip rates on the Luoshan and East Helanshan Faults

Abstract

Analysis of the locus, style, and rate of faulting is fundamental to understanding the kinematics of continental deformation. The Ordos Plateau lies to the northeast of Tibet, within the India‐Eurasia collision zone. Previous studies have suggested that it behaves rigidly and rotates anticlockwise within a large‐scale zone of ENE‐WSW left‐lateral shearing. For this rotation to be accommodated, the eastern and western margins of the Ordos Plateau should be undergoing right‐lateral shearing and yet the dominant faulting style appears to be extensional. We focus specifically on the kinematics of the faults bounding the western margin of the Ordos Plateau and make new slip rate estimates for two of the major faults in the region: the right‐lateral strike‐slip Luoshan Fault and the normal‐slip East Helanshan Fault. We use a combination of infrared stimulated luminescence dating of offset landforms with high‐resolution imagery and topography from the Pleiades satellites to determine an average right‐lateral slip rate of 4.3 ± 0.4 mm/a (1σ uncertainty) on the Luoshan Fault. Similarly, we use 10Be exposure dating to determine a vertical throw rate on the East Helanshan Fault of <0.6 ± 0.1 mm/a, corresponding to an extension rate of <0.7 ± 0.1 mm/a (1σ uncertainty). Both of these results agree well with slip rates determined from the latest campaign GPS data. We therefore conclude that right‐lateral shearing is the dominant motion occurring in the western Ordos region, supporting a kinematic model of large‐scale anticlockwise rotation of the whole Ordos Plateau.

Tectonic Deformation of the Northeastern Tibetan Plateau and Its Surroundings Revealed With GPS Block Modeling

“…(2018), where most of the left‐lateral slip of the Haiyuan fault is accommodated by contraction across the Liupanshan Mountains, and the remaining part is transferred through the South Liupanshan fault to the subparallel Qishan‐Mazhao fault. In sum, we speculate that the observed kinematic deformation pattern around the Ordos block is a result of a combination of the sinistral shear to the south and north of the Ordos block and the push on its southwest margin from the Tibetan Plateau (Middleton et al., 2016; Xu & Ma, 1992; Zhang et al., 1998).…”

Tectonic evolution of the Qingshuihe Basin since the Late Miocene: Relationship with north‐eastward expansion of the Tibetan Plateau

“…However, the timing of thrust initiation and onset of the strike‐slip of the Tianjingshan Fault are still unclear. The Niushoushan–Luoshan Fault, which lies to the east of the Yantongshan–Yaoshan Fault—the foremost boundary of the north‐eastern Tibetan Plateau—is a dextral strike‐slip that consists of numerous secondary faults (Lei et al, 2016; Middleton et al, 2016; Shi et al, 2015). Recent studies showed a Late Quaternary right‐lateral slip rate of 0.4 mm/a (Lei et al, 2016), and an average right‐lateral slip rate of 4.3 ± 0.4 mm/a on the Luoshan Fault (Middleton et al, 2016).…”

“Frame Wobbling” Causing Crustal Deformation Around the Ordos Block

“…In this model, the Ordos block does not undergo anticlockwise rotation. Geological investigations have indicated the presence of dextral shear along the Yinchuan and Shanxi grabens on the western and eastern margins of the block (Middleton et al., 2016; Xu et al., 1994; B. Zhang et al., 1986), while the Weihe and Hetao grabens show no evidence of lateral motion of any kind (Lin et al., 2015; Ran et al., 2003).…”