HR: 14:33h
AN: GP13B-04    [Abstracts]
TI: What did the Ural Ocean look like?
AU: * Levashova, N M
EM: palmag@online.ru
AF: Geological Institute, Russian Acad. Sci., Pyzhevsky Lane, 7, Moscow, 109017 Russian Federation
AU: Degtyarev, K E
EM: degtkir@ginras.ru
AF: Geological Institute, Russian Acad. Sci., Pyzhevsky Lane, 7, Moscow, 109017 Russian Federation
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
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: McCausland, P J
EM: pjam@umich.edu
AF: Department of Geological Sciences, Univ. of Michigan, 425 East University, Ann Arbor, MI 48109-1005 United States
AB: The Ural-Mongol belt (UMB), between Siberia, Baltica and Tarim, was the locus of Asia's growth during the Paleozoic, but its evolution remains highly controversial as evidenced by disparate palinspastic models. The Ural mobile belt is the western part of the UMB. It is bounded by Baltica in the west and the Siberian basin and Kazakhstan in the east. All researchers agree that an ocean existed in the Urals during most of Paleozoic time but sharply disagree on original positions and subsequent kinematics of the bordering tectonic units. Several blocks with Precambrian basement are recognized in the western and southern parts of Kazakhstan. In the Late Ordovician, these blocks amalgamated to form a contiguous, albeit not necessarily rigid domain, the Kochetau-North Tien Shan domain (KNTD). A paleomagnetic study of a thick Upper Devonian (Frasnian) basalt-andesite pile in the North Tien Shan revealed a dual-polarity characteristic component (D = 280°, I = 55°, k = 20, a95 = 9°, N = 14 sites). Its primary origin is confirmed by a positive conglomerate test on an intraformational conglomerate. We combine this result with other Paleozoic data from the KNTD and plot paleolatitudinal motion of this unit since the Late Ordovician to the end of the Paleozoic. The observed paleolatitudes of the KTND are found to agree well with the reference values for Baltica for the entire interval; hence joint motion of the KNTD and Baltica as part of a single plate is strongly indicated for most of the Paleozoic. This finding contradicts most published models, which place the KNTD and Baltica on opposite sides of the Ural Ocean. An exception is the model of Sengor and Natal'in [1996] in which coherent paleolatitudinal motion of these two units is anticipated. We suggest another model of the Ural Ocean that relies on smaller number of assumptions and is better supported by geological and paleomagnetic data; during the middle Paleozoic, this ocean existed mainly between the combined KTND-Baltica tectonic unit and Siberia.
DE: 1525 Paleomagnetism applied to tectonics: regional, global
DE: 1527 Paleomagnetism applied to geologic processes
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005