When the Tibetan Plateau (the highest topography on Earth) originated and how it evolved have been widely debated. Has all of Tibet been high for many millions of years, or has it been built gradually over time, from the south to the north? It is currently bordered on the north by the Altyn Tagh fault, one of Earth's longest strike-slip faults. As a result of the left-lateral slip on this fault, Tibet seems to be extruding eastward. Understanding the origin of the fault and the history of its motion are fundamental to deciphering the origin and evolution of the plateau, as well as its effects on the Asian monsoon, the dynamics of the Himalayan orogeny, and the tectonic evolution of Asia.
Yin et al. examined rocks deposited along or adjacent to the fault, including those in a large nearby basin that were deposited during the past 65 million years. The nature of the deposits over time, and correlation along the fault with time allow the movement history to be inferred. Their data imply that uplift in at least this part of northern Tibet began about 50 million years ago, shortly after India collided with Asia. They conclude that the fault has been active since then, has accommodated nearly 800 km of slip, and has moved at about 9 mm per year, which remains its present rate of activity. -- BH
Geol. Soc. Am. Bull. 114, 1257 (2002).
