HR: 10:50h
AN: GP42A-03    [Abstracts]
TI: Active Transtensional Tectonics Due to Differentially Rotating Upper Crustal Blocks East of the Eastern Himalayan syntaxis, Yunnan Province, China.
AU: * StudnikiGizbert, C
EM: chrissg@mit.edu
AF: Earth, Atm., Plan. Sciences, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139 United States
AU: Eich, L
EM: irol@mit.edu
AF: Earth, Atm., Plan. Sciences, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139 United States
AU: King, R
EM: rwk@chandler.mit.edu
AF: Earth, Atm., Plan. Sciences, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139 United States
AU: Burchfiel, B C
EM: bcburch@mit.edu
AF: Earth, Atm., Plan. Sciences, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139 United States
AU: Chen, Z
EM: cdczhiliang@cgs.gov.cn
AF: Chengdu Institute of Geology and Mineral Resources, 101 Renminbeilu, Chengdu, 000 China
AU: Chen, L
EM: chenlzh@public.kn.yn.cn
AF: Yunnan Institute of Geological Sciences, x, Kunming, 000 China
AB: Seismological (Holt et. al. 1996), geodetic (King et. al. 1996, Chen et. al. 2000) and geological (Wang et. al. 1995, Wang and Burchfiel 2002) studies have shown that upper crustal material north and east of the eastern Himalayan syntaxis rotates clockwise about the syntaxis, with the Xianshuihe fault accommodating most of this motion. Within the zone of rotating material, however, deformation is not completely homogenous, and numerous differentially rotating small crustal fragments are recognised. We combine seismic (CSB and Harvard CMT catalogues), geodetic (CSB and MIT-Chengdu networks), remote sensing, compilation of existing regional maps and our own detailed field mapping to characterise the active tectonics of a clockwise rotating crustal block between Zhongdian and Dali. The northeastern boundary is well-defined by the northwest striking left-lateral Zhongdian and Daju faults. The eastern boundary, on the other hand, is made up of a 80 km wide zone characterised by north-south trending extensional basins linked by NNE trending left-lateral faults. Geological mapping suggests that strain is accommodated by three major transtensional fault systems: the Jianchuan-Lijiang, Heqing and Chenghai fault systems. Geodetic data indicates that this zone accommodates 10 +/- 1.4 mm/year of E-W extension, but strain may be (presently) preferentially partitioned along the easternmost (Chenghai) fault. Not all geodetic velocities are consistent with geological observations. In particular, rotation and concomitant transtension are somehow transferred across the Red River-Tongdian faults to Nan Tinghe fault with no apparent accommodating structures. Rotation and extension is surmised to be related to the northward propagation of the syntaxis.
UR: http://web.mit.edu/~chrissg/Public/Dali/tectonics.html
DE: 9320 Asia
DE: 8015 Local crustal structure
DE: 8107 Continental neotectonics
DE: 1208 Crustal movements--intraplate (8110)
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting