HR: 0800h
AN: GP11A-0006    [Abstracts]
TI: New Paleomagnetic Results From Late Paleozoic and Mesozoic Rocks of Tibet: Implications for the Paleogeography of the Eastern Qiangtang Terrane
AU: * Lippert, P C
EM: plippert@pmc.ucsc.edu
AF: Dept. of Earth Sciences and the Institute of Geophysics and Planetary Geophysics, University of California, 1156 High Street, Santa Cruz, CA 95064 United States
AU: Zhao, X
EM: xzhao@pmc.ucsc.edu
AF: Dept. of Earth Sciences and the Institute of Geophysics and Planetary Geophysics, University of California, 1156 High Street, Santa Cruz, CA 95064 United States
AB: We present new paleomagnetic, rock magnetic, and geochronologic data from our ongoing study of late Paleozoic and Mesozoic paleomagnetic poles from the Eastern Qiangtang Terrane in Central Tibet. This study consists of four sampling localities of the Eastern Qiangtang Terrane, from south to north: 1) the Kaixingling basalts and andesites, with underlying marls and overlying limestones of late Permian age (11 sites, 81 samples); 2) a basalt flow and overlying quartzose sandstones exposed in the southern TuoTuo He basin, also of suggested late Permian age (4 sites, 41 samples); 3) basalts and andesites from the late Triassic (Norian) Batang Group (7 sites, 55 samples); and a mid-Cretaceous (?) tonolite 15 km south of Wudaoliang (2 sites, 18 samples). These locations have previously been dated by biostratigraphic ages of overlying and underlying strata. Here we present new geochronologic data from the volcanic rocks themselves. High NRM moment values and weak-field susceptibility vs. temperature measurements suggest that magnetite is the dominant magnetic mineral. Resistance to alternating field demagnetization in many samples, in addition to data from magnetic hysteresis measurements, however, indicate a significant amount of hematite exists in these samples as well. All samples were subjected to progressive thermal demagnetization to isolate the characteristic, primary, and secondary magnetizations. Preliminary results show useful paleomagnetic poles may be forthcoming from our collections. Our data may have significant bearing on the geodynamic history of Tibet, including paleogeography of the Eastern Qiangtang Terrane, block rotations, and the nature of the Tertiary low-paleolatitude anomaly in Central Asia.
DE: 1525 Paleomagnetism applied to tectonics: regional, global
DE: 1527 Paleomagnetism applied to geologic processes
DE: 8103 Continental cratons
DE: 8157 Plate motions: past (3040)
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005