India Collision into Asia
||In the Cenozoic, the landmasses of India and Asia converged. Keeping in mind that continental crust lighter and more buoyant than oceanic crust, India resisted the subduction process. Plate movement slowed its ongoing speed to its approximate rate of movement today, 6 centimeters per year. As India collided into Tibet, a fault transpired which pushed subducting crust further down and northward beneath Tibet. Part of the continent split off, thrust up, and eroded to form the Himalayan Mountains. The Tibetan Plateau is a result of the thickened crust arising from the Indo-Asian collision and the successive collision of India into Asia. Crust under the Tibetan Plateau is thus young and soft compared to that north of it. In fact, its thickness is approximately 60 km thick.
Altyn Tagh Fault
Arizona State University. (Click image for larger view).
||The Qaidam Basin, a low-lying region formed from the Indo-Asian collision, resides in west-central China, north of the Tibetan Plateau. Although it is most known for petroleum and salt mining, it is underlain with old, Precambrian rock, which was pushed northward upon the collision (Zhu and Helmberger, 1998). |
Space Image of Western Qaidam Basin
Geomorphology from Space. (Click image for larger view).
||Compared to the Altyn Tagh Fault to the northeast and the Kunlun Fault to the south, the Qaidam basin exhibits little deformation since the Paleozoic (Zhu and Helmberger, 1998). Stable, hard, resistant crust is what prevents altering stress and acts an unfailing block to vertical axis rotations. |
USGS. (Click image for larger view).
||The Qaidam Basin contains deposits of Tertiary, red sedimentary rocks. Specifically, hematite-rich sandstones. This mineral is the essential element for paleomagnetic observations in this region.|