HR: 0800h
AN: GP11A-0001    [Abstracts]
TI: Has escape tectonics acted north of Tibet? Paleomagnetic and geological constraints in post-Permian times
AU: * Bazhenov, M L
EM: palmag@online.ru
AF: Geological Institute, Russian Acad. Sci., Pyzhevsky Lane, 7, Moscow, 109017 Russian Federation
AU: Mikolaichuk, A V
EM: mikolaichuk@mail.ru
AF: Geological Institute, National Acad. Sci., Erkendyk av., 30, Bishkek, 720049 Kyrgyzstan
AU: Van der Voo, R
EM: voo@umich.edu
AF: Department of Geological Sciences, Univ. of Michigan, 425 East University, Ann Arbor, MI 48109-1005 United States
AB: Controversial views have often been expressed as to where and how the convergence of the Indian and Eurasian plates has been accommodated. Analysis of paleomagnetic data from Central Asia for the last 270 Ma (Late Permian to Present) shows concordance between Late Permian to Triassic measured and expected inclinations north of the Tibetan plateau and the Kunlun Range, whereas in the very same region most measured inclinations are too shallow in Cretaceous and especially Tertiary sedimentary rocks. The collective paleomagnetic and geological data point to a non-tectonic origin of these too-shallow inclinations and indicate that total post-Paleozoic shortening north of Tibet falls within the error limits of available paleomagnetic data and unlikely exceeds 500 kilometers. Rotated Cretaceous and Cenozoic paleomagnetic declinations close to the Pamirs are connected with the northward indentation of the Pamir wedge, while no systematic large rotations are found in the Tien Shan east of the Talas-Fergana Fault and north of the Tarim Basin. Thus neither statistically significant northward motion nor large rotations occurred north of Tibet during the Cenozoic. We conclude that large-scale lateral extrusion cannot have played a major role in the structural evolution of Central Asia north of Tibet. In turn, this means that the total India-Eurasia convergence of about 2500 km for the last 50 Ma was mainly accommodated south of Tarim.
DE: 1525 Paleomagnetism applied to tectonics: regional, global
DE: 1527 Paleomagnetism applied to geologic processes
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005