HR: 13:40h
AN: GP13B-01    [Abstracts]
TI: Closure of the Mongol-Okhotsk Ocean as Constrained by Late Permian to Early Cretaceous Paleomagnetic Data from the Suture Zone
AU: * Cogne, J
EM: cogne@ipgp.jussieu.fr
AF: Laboratoire de Paléomagnétisme - I.P.G., 4 Place Jussieu, Paris cedex 05, 75252 France
AU: Kravchinsky, V
EM: vkrav@phys.ualberta.ca
AF: Physics Dept., University of Alberta, Edmonton, T6G2JI Canada
AU: Gilder, S
EM: gilder@ipgp.jussieu.fr
AF: Laboratoire de Paléomagnétisme - I.P.G., 4 Place Jussieu, Paris cedex 05, 75252 France
AU: Hankard, F
EM: hankard@ipgp.jussieu.fr
AF: Laboratoire de Paléomagnétisme - I.P.G., 4 Place Jussieu, Paris cedex 05, 75252 France
AB: The Paleozoic Mongol-Okhotsk Ocean separated the Siberian craton to the north from a landmass composed of Amuria, Tarim, Qaidam, Tibet and the North and South China blocks to the south. Based on a comparison of paleomagnetic data from the NCB with the Eurasian apparent polar wander path, this ocean closed by the beginning of the Cretaceous. We present here a review of recent paleomagnetic studies of Late Permian to Early Cretaceous formations from the Transbaikal area of south Siberia, coming from localities situated on both sides of the Mongol-Okhotsk suture zone. The main conclusions that we draw from these studies are as follows. (1) A Late Permian ~4500 km latitude difference indeed existed between Amuria and the Siberia blocks at 110°E longitude. (2) In Middle-Late Jurassic times, a 1700 to 2700 km paleolatitudinal gap still existed between the two blocks. This contradicts geological interpretations of a Middle Jurassic closure of the ocean at this longitude. (3) Consistency of Early Cretaceous paleolatitudes from both sides of the suture demonstrates the closure of the ocean at that time. Altogether, these suggest a quite fast closure between the Middle Jurassic and the Early Cretaceous, at about 15±11 cm/yr. Finally, all pre-Late Cretaceous paleomagnetic poles appear to be distributed along small-circles centered on site localities. We think this is due to continued deformation acting in the Mongol-Okhotsk suture region related to suturing. Conversely, the post-Early Cretaceous rotations may be related to Tertiary deformation under the effect of the India-Asia collision.
DE: 1525 Paleomagnetism applied to tectonics: regional, global
DE: 8102 Continental contractional orogenic belts and inversion tectonics
DE: 8110 Continental tectonics: general (0905)
DE: 8157 Plate motions: past (3040)
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005