HR: 1330h
AN: T42B-0297    [PDF]
TI: Age of Initiation of the India-Asia Collision in the eastern Himalayas
AU: Kidd, W
EM: wkidd@atmos.albany.edu
AF: University at Albany, 1400 Washington Avenue, Albany, NY 12222 United States
AU: Rowley, D
EM: rowley@plates.uchicago.edu
AF: University of Chicago, 5734 S.Ellis Avenue, Chicago, Il 60637 United States
AU: Currie, B
AF: University at Albany, 1400 Washington Avenue, Albany, NY 12222 United States
AU: Currie, B
AF: Miami University, 114 Shideler Hall, Oxford, OH 45056 United States
AB: We report on the provenance of the Jidula and Zongpubei Formations, located in the early Tertiary terrigenous sediments of the Tingri region, southern Tibet, which were deposited on the former northern margin of the Indian continent. Petrographical analysis of sandstones reveals that the monocrystalline quartz grains of cratonic origin are dominant in the Paleocene (Danian) Jidula Formation; in contrast there are significant amounts of immature framework grains with a distinct ophiolitic and volcanic arc influence present in the Eocene (Lutetian) Zongpubei Formation. Bulk sample major, trace and rare earth element concentrations in both sandstones and shales complement the petrographical data indicating that the source of the Jidula Formation primarily consisted of quartzose basement rocks, probably of Indian continental origin, while the Zongpubei Formation samples are mainly derived from an arc-trench system indicating the start of obduction of the Asian arc/subduction complex (Gangdese-Xigaze) during the deposition of the Zongpubei sedimentary rocks. The probe compositions of Cr-rich spinels in the Zongpubei sandstones are closely similar to those from fore-arc peridotites, so are most likely derived from the arc and ophiolite rocks along the Yarlung-Zangbo suture to the north. No spinels have been observed in the Jidula sandstones. These early Tertiary detrital clastics in the Tingri region record a marked change in provenance and sediment character starting with the deposition of the Zongpubei Formation. This change indicates that the onset of India-Asia collision and development of the foreland basin on the Indian passive margin started at ~~47 Ma in the eastern part of the Himalayas. This is about 4 Ma younger than the age determined by Garzanti et al.(1987, 1996) in the Zanskar section of the western Himalayas.
DE: 1020 Composition of the crust
DE: 8102 Continental contractional orogenic belts
DE: 8105 Continental margins and sedimentary basins
SC: Tectonophysics [T]
MN: 2003 Fall Meeting