New paleomagnetic constraints on central Asian kinematics: Displacement along the Altyn Tagh fault and rotation of the Qaidam Basin

Abstract

In order to better understand the tectonic evolution of central Asia under the influence of the India‐Asia collision, we carried out a paleomagnetic study of 1500 cores from 106 sites along the Altyn Tagh fault, in the Qaidam and Tarim basins, and on the Tibetan plateau. Samples were mainly collected from Jurassic to Neogene siltstones and sandstones. In most cases stepwise thermal demagnetization unblocks low and high temperature components carried by magnetite and hematite. Low temperature components are north and down directed and lie close to the recent geomagnetic field. High temperature components from 10 of 13 age/locality groups pass fold and/or reversal tests and likely represent primary remanent magnetizations. The ten overall mean directions display a complex pattern of vertical‐axis block rotations that are compatible with a tectonic model of clockwise rotation of the Qaidam Basin and concomitant left‐lateral slip on the Altyn Tagh fault. Two of the ten localities are rotated significantly counterclockwise; they lie adjacent to the Altyn Tagh fault zone, consistent with the idea that left‐lateral strike‐slip motion occurred along it. The age of counterclockwise rotation near the eastern extremity of the fault was dated as younger than 19 Ma. Three widely spread areas within the Qaidam Basin exhibit similar and significant clockwise rotations, on the order of 20°, with respect to the North China Block, Tarim and Eurasia. The mean of the three values is thought to represent the total rotation of Qaidam. Because the youngest rocks displaying clockwise rotations are Oligocene, the main phase of Qaidam Basin rotation, and hence shear on the Altyn Tagh fault, took place after or near the end of the Oligocene (∼24 Ma). Upper Neogene strata located on the Qaidam Basin are not significantly rotated, thus tectonic deformation acting since the Upper Neogene (∼5 Ma) is not resolvable by paleomagnetic methods. Given a 20° ± 5° clockwise rotation of the Qaidam Basin with respect to the Tarim Basin, the maximum left‐lateral displacement on the Altyn Tagh fault since 24 Ma is 500 ± 130 km.

Initial rupture and displacement on the Altyn Tagh fault, northern Tibetan Plateau: Constraints based on residual Mesozoic to Cenozoic strata in the western Qaidam Basin

“…By matching the Tertiary rocks along the northern and the central segments of the Altyn Tagh fault, Wang (1997) ascertained 69-90 km of displacement. Chen et al (2002) suggested an offset of 500 ± 130 km between 24 Ma and present based on paleomagnetic data from the Qaidam Basin. Notably, 400 ± 60 km has also been suggested based on the reconstruction of a Jurassic facies boundary across the Altyn Tagh fault (Ritts and Biffi, 2000).…”

The Permian Extinction and the Tethys: An Exercise in Global Geology

“…15B) have been available from all parts of the Altaid collage and from the Kuen-Lun system at large (including the Qilian Shan, Qinghai Nan Shan, and the Anyemaqen Shan) ever since Suess (1901), Kober (1921), Argand (1924), Lee (1928), and Stille (1929) drew attention to its widespread occurrence and especially after interest in it was revived in the framework of plate tectonics by the landmark paper of Molnar and Tapponnier (1975). We here cite only a few of the more comprehensive, exemplary, and the most recent studies documenting it: Şengör (1984; 1987), Hendrix et al (1992), Lu et al (1994), Allen et al (1995), Cunningham et al (1996), Allen and Vincent (1997), Burov and Molnar (1998), Delville et al (2001), Greene et al (2001), Ritts and Biffi (2001), Sobel et al (2001), Sjostrom et al (2001), Vincent and Allen (2001), Chen et al (2002), Wartes et al (2002), and Xiao et al (2004).…”

Paleomagnetic versus GPS determined tectonic rotation around eastern Himalayan syntaxis in East Asia

“…Several left-lateral boundary faults, such as, the Altyn Tagh Fault, the Kunlun Fault and the Haiyuan Fault, have possibly played an important role in the rotational deformation of this block. A left-lateral slip movement along the Altyn Tagh Fault during the Oligocene (Chen et al, 2002a) may possibly be a cause of this tectonic rotation. Alternatively, lower crustal flow might have instigated CW rotation in the northeastern part of the Tibetan Plateau (as described in the surface rotation model by Royden et al (1997)).…”