New Magnetic Constraints on Early‐Middle Miocene Uplift of the Liupan Shan, Northeastern Margin of the Tibetan Plateau

Abstract

New constraints on the uplift history of the Liupan Shan can improve our understanding of the tectonic consequences of the collision of the Indian and Asian plates, including the timing of the uplift of the Tibetan Plateau. Here we present a detailed magnetostratigraphy for the Kaimengou section near the piedmont of the Liupan Shan, which reveals that it spans the interval from 19.8 to 12.8 Myr. Together with the results of measurements of the anisotropy of magnetic susceptibility, rock magnetic measurements show that the anisotropy of magnetic susceptibility is dominated by antiferromagnetic hematite and/or paramagnetic minerals, both of which are mainly controlled by the preferred crystallographic orientation, which can be used to record the tectonic history. During 19.5–14.0 Myr, the maximum principal axis (Kmax) showed a pronounced N‐S orientation and Kmin began to exhibit a girdled distribution in an E‐W direction, indicating a slight to moderate tectonic strain in an E‐W direction. And the strain can be reconfirmed be the shape parameter (T). We attribute the strain to far‐field influence by the collision of the Indian and Asian plates. We also present a tentative conceptual model, which explains how the E‐W compression fits within the general tectonic scenario for the uplift of the Tibetan Plateau.

Slowing Extrusion Tectonics and Accelerated Uplift of Northern Tibet Since the Mid‐Miocene

“…AMS is demonstrated to be efficient in investigating subtle tectonics-related fabrics in weakly deformed or undeformed clay-rich sedimentary sequences undergoing incipient tectonic deformation (Gilder et al, 2001;He et al, 2021;B. Li et al, 2020;Li et al, 2021;Lu et al, 2014;Nie et al, 2020;Parés, 2015;Parés et al, 1999;Soto et al, 2009;Su et al, 2016;Weil & Yonkee, 2012;Wu et al, 2019;. The comparison between AMS and paleostress data validates the reliability of AMS ellipsoids as paleostress indicator in compressional settings (e.g., Soto et al, 2009).…”

“…The AMS fabrics produce kinematic data to be compared to mesostructures such as folds and faults in northern Tibet (Gilder et al., 2001; He et al., 2021; B. Li et al., 2020; Li et al., 2021; Lu et al., 2014; Nie et al., 2020; Su et al., 2016; Wu et al., 2019; Yu, Huang, et al., 2014). These studies have shown that the orientation of the AMS ellipsoid is in most cases related to the local stress field.…”

“…The AMS method is a petrofabric tool to determine preferred orientation of particles under an external force, such as gravity, wind, magnetic field, water flow, and strain, during deposition and diagenesis of rocks (e.g., Dallanave & Kirscher, 2020; S. Li et al., 2020; Parés et al., 1999). AMS is demonstrated to be efficient in investigating subtle tectonics‐related fabrics in weakly deformed or undeformed clay‐rich sedimentary sequences undergoing incipient tectonic deformation (Gilder et al., 2001; He et al., 2021; B. Li et al., 2020; Li et al., 2021; Lu et al., 2014; Nie et al., 2020; Parés, 2015; Parés et al., 1999; Soto et al., 2009; Su et al., 2016; Weil & Yonkee, 2012; Wu et al., 2019; Yu, Huang, et al., 2014). The comparison between AMS and paleostress data validates the reliability of AMS ellipsoids as paleostress indicator in compressional settings (e.g., Soto et al., 2009).…”

Gravity analysis of the offset between crustal structure and topography in the Liupan Shan, northeast Tibetan Plateau

“…Although the precise uplift mechanism is debated, the following coexisting end-member models have been proposed: (1) oblique subduction of surface materials (Tapponnier et al 2001); (2) lower crustal flow (Royden et al 1997); and (3) migration of mantle materials (England and Houseman 1989). These models are supported by evidence from seismological (Shen et al 2017), thermochronological (Wang et al 2011), magnetic (Wu et al 2019), and gravity analyses (Wang et al 2014). Uplift mechanisms can be studied using the gravity admittance method, which can calculate the initial loading ratio to reveal the loading source in the lithosphere (McKenzie 2003).…”