|Title:||Structural evolution of the Arunachal Himalaya and implications for asymmetric development of the Himalayan orogen|
|Authors:||A. Yin, C.S. Dubey, T.K. Kelty, G.E. Gehrels, C.Y. Chou, M. Grove, and O. Lovera|
|Publication:||Current Science, v. 90, p. 195‐206.|
|Publish Date:||Jan 2006|
Geologic mapping and stratigraphic correlation of low‐grade Precambrian Lesser Himalayan units using U‐Pb detrital zircon dating reveal the existence of a Main Central Thrust (MCT) window and a prominent ductile thrust zone within the Greater Himalayan Crystallines in the Arunachal Himalaya of NE India. The newly discovered MCT window is cut and offset by several active north‐trending normal faults extending from southeast Tibet, indicating the fault is no longer active. Ion‐microprobe dating of monazite inclusions in garnets from the MCT zone indicates that the fault was active at 10.1 ± 1.4 Ma. Our structural data together with a synthesis of existing geologic maps suggest that the eastern Himalaya is composed of a large thrust duplex with the folded MCT as the roof fault. The total amount of crustal shortening accommodated by the duplex and the MCT south of the South Tibetan Detachment may exceed 500 km, which is probably greater than the amount of crustal shortening across the central Himalaya in Nepal and definitely greater than the amount of shortening across the western Himalaya in Pakistan. The observed systematic variation of crustal shortening suggests that Himalayan crustal thickening and uplift are uneven along strike, which may be in response to the westward decrease in convergence rate between India and Asia during the Cenozoic.