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.