CENOZOIC VERTICAL-AXIS ROTATION OF THE ALTYN TAGH FAULT SYSTEM

Abstract

Paleomagnetic declination data were collected from Cenozoic strata of the southern rim of the Tarim basin to address whether the Altyn Tagh fault has undergone significant rotation during the Indian-Asian collision. Results from the eastern and central Altyn Tagh fault zone suggest that it has undergone no significant rotation since the Oligocene. This implies that the boundary between the Tarim and Tibet has remained relatively stationary during most of the Cenozoic. In contrast, declination data from the western Kunlun Shan on the eastern limb of the Pamir orocline, where the Karakax segment of the Altyn Tagh fault system terminates, suggest that the range has undergone clockwise rotations of between 19.3° ± 8.6° and 27.8° ± 5.8°. Such rotation is in mirror image with the documented counterclockwise rotation of 20° 50° in the western Pamir orocline and implies relatively small displacements on the Karakorum fault. Our results also suggest that the Karakax fault may have formed as an accommodation zone between the western Kunlun Shan and the Karakorum Mountains.