Paleomagnetism of Eocene and Miocene sediments from the Qaidam basin: Implication for no integral rotation since the Eocene and a rigid Qaidam block

Abstract

The Qaidam basin is the largest topographic depression inside the Tibetan Plateau and it is a key factor to understanding the Cenozoic evolution of the northern Tibetan Plateau. Paleomagnetic data was obtained from the middle to late Eocene Xiaganchaigou Formation and the early to middle Miocene Xiayoushashan Formation from seven localities. The paleomagnetic results indicate that the Qaidam basin has not undergone obvious basin-scale vertical axis rotation with respect to the Eurasia Plate since the Eocene. Local clockwise rotation took place only at a few special locations along the northern margin of the Qaidam basin. The uniform paleomagnetic results at different localities support that the Qaidam basin is a relatively rigid block. Regional paleomagnetic and geodetic observations also suggest that crust south of the Kunlun fault moves eastward faster than crust north of the Kunlun fault.

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

“…4; see also fig. 3 in Dupont-Nivet et al, 2004) and suggest northward transport along the Altyn Tagh fault of this section, the western segment of the Eastern Kunlun Range (Qimen Tagh Range), and the Qaidam Basin (Dupont-Nivet et al, 2004;Yu et al, 2014). The absence of a large vertical axis of rotation in the area adjacent to the Altyn Tagh fault indicates that the left-lateral shear strain between the Tarim Basin and the northern Tibetan Plateau is concentrated on the relative weak Altyn Tagh fault (Dupont-Nivet et al, 2002J.M.…”

“…In addition, matching geochemical fingerprints (e.g., carbon isotopic composition) between the Jurassic oil-bearing sandstone of the Tula Basin and the Jurassic crude oil of Qaidam Basin suggest that these two regions must have been parts of the same prototype basin (Guo et al, 1998). Recent studies confirm that the relatively rigid Qaidam Basin was transported northeastward along the Altyn Tagh fault during the Cenozoic, and it has not undergone obvious basin-scale vertical-axis rotation with respect to the Eurasian plate since early Eocene time (E. Yu et al, 2014). Considering the large-scale, left-lateral, strike-slip displacement of the Altyn Tagh fault during Cenozoic time, we suggest that the Tula and Anxi sections were once part of the Qaidam Basin but detached from the Qaidam during its northeastward migration driven by faulting on the Altyn Tagh fault.…”

An Analysis of Distributed Strike‐Slip Shear Deformation of the Qaidam Basin, Northern Tibetan Plateau

“…A delay in initiation of deformation may explain the somewhat smaller rotation angle of the Nanyishan anticline compared with that of the Dafengshan anticline (Liu et al, ). Although the above best‐fit rotation angles, representing the lower limits of the real rotation angles of the anticlines, are not high enough to be detected by paleomagnetism (Dupont‐Nivet et al, ; Li et al, ; Yu, Fu, et al, ), block rotation accounts for more of the strike‐slip component than does oblique convergence.…”

Expansion of the Tibetan Plateau during the Neogene

“…Second, the accumulation of coarse, clastic detritus shed from rapidly eroded mountain ranges6812 suggests the development of topographic relief. Third, vertical-axis rotation of these sedimentary deposits calculated from the paleomagnetic declination with respect to the APWP of Eurasia713 suggest a clockwise rotation in Paleogene time.…”