HR: 15:25h
AN: GP13B-07    [Abstracts]
TI: Late Paleozoic Paleomagnetism of Southeast Kazakhstan: Age and Mode of Rotations
AU: * Van der Voo, R
EM: voo@umich.edu
AF: University of Michigan, Department of Geological Sciences, Ann Arbor, MI 48109-1005 United States
AU: Skrinnik, L S
EM: palmag@online.ru
AF: Institute of Geological Sciences, Kabanbay Batyr 69a, Almaty, 480010 Kazakhstan
AU: Bazhenov, M L
EM: palmag@online.ru
AF: Academy of Sciences of Russia, Geological Institute, Pyzhevsky Lane 7, Moscow, 109017 Russian Federation
AU: Levashova, N M
EM: palmag@online.ru
AF: Academy of Sciences of Russia, Geological Institute, Pyzhevsky Lane 7, Moscow, 109017 Russian Federation
AU: Kara, T V
EM: palmag@online.ru
AF: Academy of Sciences of Russia, Geological Institute, Pyzhevsky Lane 7, Moscow, 109017 Russian Federation
AB: In this presentation we introduce new paleomagnetic data from the Ili River Valley area in southeastern Kazakhstan (between the North Tien Shan and the Junggar-Alatau Range) for Carboniferous to Upper Permian volcanics and sediments. The area is part of the Ural-Mongol belt, and formed the focus where the Siberian, Baltica and Tarim cratons converged during late Paleozoic and early Mesozoic time. Thermal demagnetization reveals that most Upper Permian rocks retain a pretilting and probably primary component, which is reversed at three localities and normal at the fourth one. In contrast, most Carboniferous rocks are dominated by postfolding reversed overprints of most likely mid-Permian age, with presumably primary components being isolated only from a few sites at two localities. Mean inclinations of both primary and secondary components generally agree with coeval reference directions for Baltica and Siberia, as well as other Permian results from Kazakhstan, the North Tien Shan and Tarim, suggesting that these areas were already in close proximity during Permian time. However, declinations values in southern Kazakhstan, the North Tien Shan and Tarim are deflected westward, indicating counterclockwise rotations up to about 90 degrees. While the declination patterns are compatible with significant oroclinal bending in post-Permian time, they could also be attributed to another process, such as large-scale wrenching of latest Permian - early Mesozoic age due to orogenic transpression resulting from the Siberia-Tarim-Baltica convergence. Younger (e.g., Cenozoic) strike-slip-related rotations in Tarim and the Tien Shan are generally minor, suggesting the bulk of the rotations is Permo-triassic in age.
DE: 1525 Paleomagnetism applied to tectonics: regional, global
DE: 1527 Paleomagnetism applied to geologic processes
DE: 8102 Continental contractional orogenic belts and inversion tectonics
DE: 8111 Continental tectonics: strike-slip and transform
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005