HR: 0800h
AN: GP11A-0002    [Abstracts]
TI: Carboniferous Paleomagnetic Study of Zhemanty, Kendyktas block, Kazakhstan
AU: * McCausland, P J
EM: pmccausl@uwo.ca
AF: Geological Sciences, Univ. of Michigan, 425 East University, Ann Arbor, MI 48109-1063 United States
AU: Bazhenov, M L
EM: palmag@online.ru
AF: Geological Institute, Russian Acad. Sci, Pyzhevsky Lane, 7, Moscow, 109017 Russian Federation
AU: Van der Voo, R
EM: voo@umich.edu
AF: Geological Sciences, Univ. of Michigan, 425 East University, Ann Arbor, MI 48109-1063 United States
AU: Degtyrev, K E
GP11A-0002 AF: Geological Institute, Russian Acad. Sci, Pyzhevsky Lane, 7, Moscow, 109017 Russian Federation
AU: Levashova, N M
GP11A-0002 AF: Geological Institute, Russian Acad. Sci, Pyzhevsky Lane, 7, Moscow, 109017 Russian Federation
AB: Paleomagnetic studies in Central Asia over the last decade have begun to reveal the happy occurrence of ancient remanence beyond the presence of a pervasive Permian overprint. The timing and kinematics of the Paleozoic assembly of Eurasia nevertheless remain poorly understood, especially concerning the formation of the huge arcuate magmatic/structural belts of Central Asia. In this contribution we report preliminary paleomagnetic results from the Lower to Mid Cretaceous Zhemanty volcano-sedimentary succession of the Kendyktas block in southern Kazakhstan. Thermal demagnetization of andesitic flows and grey siltstones exhibit a stable high temperature component (HTC) in the flows which in tilt-corrected coordinates is of dual-polarity (west-northwest and up). A conglomerate test is positive, indicating that the HTC is likely primary. Zhemanty also retains in the flows an intermediate temperature component that matches the entire characteristic remanence found in the siltstones, together giving an in situ direction that is southwest and up. Both the HTC (Early Carboniferous) and ITC-siltstone (Permian overprint?) directions from Zhemanty indicate minimal CW rotation of the Kedyktas block with respect to the expected directions for Baltica at those times. Other paleomagnetic results of Ordovician to Permian age in the Kedyktas block also indicate nil to moderate CW rotations with respect to coeval Baltica reference poles. Adjacent structural regions to the Kendyktas block (the Chu-Ili Range to the north; the North Tien Shan to the south) show significant CCW rotations for Upper Paleozoic units. Taken together these results imply the presence of a complex rotational pattern amongst the components of the Central Asian collage that modifies or precludes the possibility of a simple orocline model for the origin of the arcuate magmatic/structural belts of Central Asia.
DE: 8110 Continental tectonics: general (0905)
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005