Paleomagnetism indicates no Neogene rotation of the Qaidam Basin in northern Tibet during Indo-Asian collision

Paleomagnetic data were obtained from Tertiary red sedimen-tary rocks at two locations separated by several hundred kilome-ters within the Qaidam Basin. In the east-central part of the basin, 30 sites from the lower Pliocene Youshashan Formation yielded characteristic remanent magnetization (ChRM) directions with in-termediate unblocking temperatures (100–600 8C); ChRM with high unblocking temperatures (to 680 8C) was isolated from 14 sites. In the same area, ChRM directions were obtained from six sites within the Oligocene Lower Gancaigou Formation. Charac-teristic magnetization was also determined from 16 sites within the Lower Gancaigou Formation exposed in the E Bo Liang range of the north-central Qaidam Basin. When compared with equivalent-age expected directions for Eurasia, the mean paleomagnetic di-rections indicate no Neogene vertical-axis rotation of the Qaidam Basin or the Altyn Tagh fault. The Qaidam Basin may act as an indentor translating without rotation toward the North China block and driving clockwise vertical-axis rotations by differential shortening within the Nan Shan fold-and-thrust belt.