HR: 13:55h
AN: T23F-02    [Abstracts]
TI: Structure Of The Elevated Precambrian Terranes Rising Above The Brahmaputra Plains In Northeastern India.
AU: * Gaur, V K
EM: gaur@cmmacs.ernet.in
AF: Indian Institute of Astrophysics, II Block, Koramangala, Bangalore, 560034, India
AU: * Gaur, V K
EM: gaur@cmmacs.ernet.in
AF: CSIR Center for Mathematical Modelling and Computer Simulations, NAL Belur Campus, Bangalore, 560037, India
AU: Hazarika, N K
EM: navahazarika@yahoo.com
AF: Dept. of Physics, Tezpur University, Napam, Tezpur, 784028, India
AU: Mitra, S
EM: mitra@gg.iitkgp.ernet.in
AF: Dept. of Geology and Geophysics, Indian Institute of Technology, Kharagpur, WB 721302, India
AU: Priestley, K
EM: keith@madingley.org
AF: Bullard Laboratories, Madingley Rise, Dept. of Earth Sciences, Cambridge, CB30EZ, United Kingdom
AB: We present new evidence for a thinner crust beneath most of the Shillong plateau as well as its northeast extension in Mikir Hills of northeastern India.Both these Precambrian terranes rise above the Brahmaputra plains whose crust is thicker in comparison by atleast 4~km. Although Bouger gravity over the Mikir Hills still remains to be determined, its near zero value over the ~1 km high plateau and the near normal upper mantle beneath the region, require that these elevated terranes must have been uplifted between reversed faults and continue to be supported by them under compression. The southern edge of the Shillong plateau is indeed marked by the prominent Dauki fault which swerves northeastward at the south eastern margin of the plateau to merge with the Naga thrusts that bound the Mikir Hills on the east. A similar fault bounding the plateau on the north as hypothesized by Bilham et al (2000) -the Oldham fault- is therfore required to swerve northeastward near the northeastern margin of the plateau to demarcate the Mikir Hills from the thicker crust Brahmaputra plains to its north and west. This could be explained by a strike slip offset of the Oldham fault caused by the as yet obsure but active tectonics of the NNW trending Kopili lineament that ensues from the inflexion in the Dauki-Naga thrust fault system.
DE: 7203 Body waves
DE: 7205 Continental crust (1219)
DE: 7218 Lithosphere (1236)
DE: 8110 Continental tectonics: general (0905)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting