Abstract Most existing tectonic models suggest Pliocene–Quaternary deformation and uplift of the NE Tibetan Plateau in response to the collision of India with Asia. Within the NE Tibetan Plateau, growth of the terranes was suggested to progress northeastward with the Yumu Shan (mountain) at the northeasternmost corner of the Qilian Shan (mountains) being uplifted only since about 1 Ma ago. Here we present a detailed palaeomagnetic dating and tectonosedimentological measurement of Cenozoic sediments in the eastern Jiuquan Basin related to the deformation and uplift of the North Qilian Shan and Yumu Shan. The results show that the eastern Jiuquan Basin is a Cenozoic foreland basin and received sediments at about 27.8 Ma at the latest. Eight subsequent tectonic events at about 27.8, 24.6, 13.7–13, 9.8–9.6, 5.1–3.6, 2.8–2.6, 0.8 and 0.1 Ma demonstrate the development of the foreland basin in response to Oligocene–Quaternary uplift of the North Qilian Shan and subsequent propagation of thrust–fold system owing to collision of India with Asia. The Yumu Shan is the late phase of deformation front in the thrust–fold system and commenced rapid uplift at about 9.8–9.6 Ma at the latest. A rigid block-floating model is proposed to interpret the mechanism of this deformation and uplift history.

Abstract Vertical-axis rotations of blocks in/around the Tibetan Plateau can be attributed to the India–Asia collision. Study of the vertical-axis rotations of these blocks will increase our understanding of the mechanisms and kinematics of continent–continent collisions. We report here a new palaeomagnetic study of rotations using data from four localities (five magnetostratigraphy sections) in the Jiuquan Basin. Our study indicates that the mean declinations of each section are different from each other, similar to what has been observed in the other localities in the NE Tibetan Plateau. However, using the mean directions of every 100 m of section, we observe that the four localities have similar sequential patterns of rotations during the last 13 Ma: significant continuous counterclockwise before c. 8.0 Ma, insignificant rotations between 8.0–4.0 Ma, and slight clockwise rotation after 4.0 Ma. This indicates that, rather than being a record of spatially varying declinations, it is a temporal variation in the occurrence of regional rotations. Combined with other geological evidence, the rotation patterns may suggest two major tectonic activity phases of the northeastern Tibetan Plateau during the last 13 Ma: an eastward extrusion and strike-slip dominant phase before 8.0 Ma, a significant shortening and a rapid uplift dominant phase after 8.0 Ma. Supplementary material: Magnetostratigraphic results of the Hongshuiba and Wenshushan sections are available at: http://www.geolsoc.org.uk/SUP18540 .

We report paleomagnetic data from the northeastern margin of the Tibetan Plateau to help understand the timing and distribution of deformation (i.e., vertical-axis rotations) during the India-Asia collision. Paleomagnetic results throughout Xining Basin strata, recently dated using magnetostratigraphy to between 52 and 17 Ma, show that some 25° of clockwise rotation with respect to the stable Eurasian continent occurred at ca. 41 Ma. In view of a regional compilation of existing paleomagnetic data from the northeastern Tibetan Plateau, these results suggest that this region experienced clockwise rotations in the regional Paleocene-Miocene basin system, including rotation in the Xining Basin, ca. 41 Ma, thus establishing the existence of widespread deformation at this time. During a mid-Miocene phase, between 17 and 11 Ma, clockwise rotations were restricted to the Miocene-Quaternary basin system, implying that the Laji Shan thrust belt, which separates the two basin systems, was active during this time interval.