The Northern Tibetan Plateau


Kunlun Shan from the South - J.H. Wittke

 

Looking northward, the southern face of the Kunlun Mountains rises sharply above a barren plain, the Xidatan-Tuosuohu-Maqu Fault defining its southern border (right). Glaciers and snowfields do not extend as far down the southern side of the mountains.


Fenghuo Shan

Tsaidam Basin, Kunlun Shan & Fenghuo Shan

The Tsaidam Basin is visible at the bottom of this Space Shuttle photograph. The Kunlun Mountains cut diagonally across the photograph from the lower left to middle right. The snow-capped peaks in the upper left part of the picture are the Fenghuo Shan. Golmud is at the entrance to the winding valley through the Kunlun Shan in the lower left corner. The Fenghuo Mouintains, comprised of Eocene and Cretaceous redbeds, are upper left half of the image. The ruddy sedimentary rocks of this area have been extensively thrusted and folded, but form more subdued mountains than the crystalline rocks in the Kunlun.

The Jinsha Suture, which is the boundary between the Songban-Ganzi and Qiangtang crustal blocks, is located within the Fenhuo Mountains, but is covered by recent alluvium. Ophiolites associated with this suture crop out about 50 km west of the road. The age of closure is considered to be Late Triassic to Early Jurassic.


Erdaogou

Redbeds near Erdaogou - J.H. Wittke

 

The Late Cretaceous-Eocene redbeds are strongly deformed near the town of Erdaogou (left), just south of Fenghuoshan Pass, which is 4958 m (16,266') high according to the geological map, but 5100 m (16,728') according to the Qinghai "traffic" map purchased in Golmud. Prayer flags are strung around a telephone pole like ropes off a May pole, but unlike at Kunlun Pass, there are no fancy monuments to mark the summit. The redbeds were deposited unconformably on Triassic-Jurassic and Paleozoic rocks of the Qiangtang Terrane, and deformed during the Himalayan orogeny. They are intruded by a 30 Ma trachyte/syenite stock about 15 km northwest of Fenghuoshan Pass, indicating a pre-Oligocene age of deformation. The frontal thrust is located about 15 km south of Erdaogou, and the steep valley through the Fenghou Shan opens out into a wide plain.


Tuotuo River

Tuotuo River - J.H. Wittke

 

The sole claim to fame for the village of Tuotuo River is the "First Bridge over the Yangtze." The Tuotuo River is considered the principal source of the Yangzi River, and at an elevation of about 4530 m (14,860'), the bridge is located closest to the source of the Yangtze. The shallow river fills the broad plain in a series of ever-shifting braids (right). South of Tuotuo River is a sequence of deformed Paleozoic rocks. These are intruded by what appears to be a young volcanic center (twin peaks on horizon at left), although it is not indicated on the map.


Wenchuan Station

Faulting near Wenchuan - J.H. Wittke

 

South of Wenchuan Station, reputedly the highest village in the world, the redbeds are faulted and tilted in a narrow zone of deformation (left).


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