HR: 0800h
AN: GP11A-0007    [Abstracts]
TI: Apparent Polar Wander Path for Siberian Platform
AU: * Kravchinsky, V A
EM: vkrav@phys.ualberta.ca
AF: Physics Department, University of Alberta, Edmonton, AB T6G2J1 Canada
AU: Kabin, K
EM: kabin@Phys.UAlberta.CA
AF: Physics Department, University of Alberta, Edmonton, AB T6G2J1 Canada
AB: A number of years has passed since the last compilations of paleomagnetic poles for Siberia platform have been published. Although Smethurst et al. (1998) classified the poles accordingly to Van der Voo's criteria of reliability (1993) some of those poles must be still regarded with great caution. Majority of the Siberian poles were published before 1980 and have an unacceptably low code of laboratory testing (McElhinny and Lock, 1996). Many poles do not include any description of geological setting or laboratory procedure. We re-analyze available paleomagnetic poles from the database to compose up-to-date APWP of the Siberian platform for Paleozoic and Mesozoic starting from 500 Ma up to 150 Ma. A number of methods have been used up-to-date for determining the APWPs for different continents. Majority of them are smoothing methods. It actually does not matter too much which of the smoothing methods to use when we have an extensive dataset. The major problem now seems to be a determining the APWP for older geological times where the data are isolated and data should be interpolated. In our approach instead of straightforward interpolation we applied least squares fit based on polynomials. The coefficients of the polynomials were calculated using Singular Value Decomposition (SVD). The APWP computed with a least-squares method in general does not pass exactly through any of the available reference points, but is located close to all of them. This seems to be the most reasonable approach to modeling relatively few inexact data points. First we demonstrate that the proposed SVD method is adequate for the numerous European dataset and compare it with the APWP of Europe constructed by Torsvik et al. (2001). Then we applied the method for the Siberian data and compared a few versions with different polynomials and various number of polynomials. For reproducing Siberian data, we find that 10 polynomials appear to strike the right balance. An example of Siberian APWP demonstrates that there are at least three major turns of the Siberian platform around 200-220, 300-320 and 400-420 Ma. Two famous Siberian trap events of Late Permo - Early Triassic and Late Devonian - Early Carboniferous age and Late Silurian - Early Devonian rifting in Altai-Sayan area occurred just before these directional changes in the APWP.
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