New paleomagnetic data have been obtained for the Late Vendian sedimentary rocks of the East Sayan and Southwest Baikal regions in the southwest of the Siberian platform. Two substantially different paleomagnetic components are isolated within the investigated stratigraphic interval in all objects of study. The prefolding age of these components, as well as their difference from all of the known Phanerozoic paleomagnetic directions of the Siberian platform, indicate the almost simultaneous formation of the respective magnetization components during the earliest stages of the existence of these rocks. The angular distance between the paleomagnetic poles calculated for these components is about 45o. The analysis of the World Paleomagnetic Database shows that the presence of the discordant paleomagnetic directions in the Vendian-Early Cambrian rocks is characteristic not only of the Siberian objects but is also manifested in other continents and, hence, can be considered as the phenomenon of the planetary scale. We reckon that this fact can be explained by the anomalous behavior of the magnetic field of the Earth around the Precambrian-Cambrian boundary. In this paper we suggest a model describing the "geometry'' of the Earth magnetic field in the Late Vendian-Early Cambrian, which allows one to explain the observed pattern of the paleomagnetic record.
paleomagnetism, Vendian, Cambrian, Siberian platform, anomalous geomagnetic field behavior.
1. Aleksandrov, Dokl. Akad. Nauk, v. 380, no. 4, 2001.
2. Anisimova, Geol. Geofiz., v. 17, no. 5, 1976.
3. Bazhenov, Earth Planet. Sci. Lett., v. 104, 1991.
4. Brasier, Episodes, v. 17, no. 1--2, 1994.
5. Brown, Earth Planet. Sci. Lett., v. 60, 1982.
6. Dankers, Can. J. Earth Sci., v. 18, 1981.
7. Enkin, A Computer Program Package for the Analysis and Presentation of Paleomagnetic Data, 1994.
8. Enkin, Formation et Deformation de l#39;Asie depuis la Fin de l#39;Ere Primaire, 1990.
9. Gallet, Geophys. J. Int., v. 154, 2003.
10. Gurevich, Paleomagnetism and Problems of Paleogeography, 1981.
11. Gurevich, Paleomagnetism of Late Precambrian Rocks in the USSR Territory, 1983.
12. Harland, Geologic Time Scale 1989, 1990.
13. Khomentovsky, Geology and Geophysics, v. 41, no. 4, 2000.
14. Khomentovsky, Geotectonics, v. 35, no. 3, 2001.
15. Khomentovsky, Dokl. Akad. Nauk, v. 362, no. 6, 1998.
16. Khomentovsky, The Marker Sequences of Late Precambrian and Early Cambrian Rocks in the Siberian Platform, 1972.
17. Kirschvink, Geol. Mag., v. 121, no. 3, 1984.
18. Kirschvink, Science, v. 277, 1997.
19. Komissarova, Paleomagnetism and Geodynamics of the USSR territory, 1991.
20. Komissarova, Paleomagnetism of Late Precambrian rocks in the USSR, 1983.
21. Komissarova, Paleomagnetic Methods In Stratigraphy, 1984.
22. Komissarova, Magnetic Stratigraphy and Paleomagnetism of Sedimentary and Volcanic Rocks in the USSR, 1986.
23. Konstantinov, A Dynamic Physicogeological Model of the Baikal Folded Area from Paleomagnetic Data, 1998.
24. Korolyuk, Dokl. Acad. Nauk SSSR, v. 184, no. 3, 1969.
25. Kochnev, Stratigraphy of Vendian Rocks in the Southwest of the Siberian Platform, 2002.
26. Kravchinsky, Precambrian Res., v. 110, 2001.
27. Kreemer, Geophys. J. Int., v. 154, 2003.
28. Landing, Geology, v. 2, 1994.
29. Letnikova, The Geodynamic Ocean-to-Continent Evolution of the Lithosphere in the Mobile Belt of Central Asia, 2004.
30. Malykh, Geotectonics, v. 31, no. 2, 1997.
31. McElhinny, Paleomagnetism: Continents and Oceans, 2000.
32. Meert, Earth Planet. Sci. Lett., v. 168, 1999.
33. Meert, Geophys. J. Int., v. 146, 2001.
34. Meert, J. Geophys. Res., v. 99, no. B3, 1994.
35. Murthy, Can. J. Earth Sci., v. 29, 1992.
36. Pavlov, Phys. Solid Earth, v. 33, no. 6, 1997.
37. Pavlov, Phys. Earth Planet. Inter., v. 108, 1998.
38. Pavlov, Geophys. J. Int., v. 154, 2003.
39. Pavlov, Phys. Solid Earth, v. 40, no. 2, 2004.
40. Piper, Geol. Foeren. Stockholm Foerh., v. 103, 1981.
41. Pisarevsky, Tectonophysics, v. 375, 2003.
42. Pisarevsky, EOS, v. 84, no. 20, 2003.
43. Pisarevsky, Geophys. J. Int., v. 154, 1997.
44. Pisarevsky, Geophys. J. Int., v. 140, 2000.
45. Pisarevsky, Geophys. J. Int., v. 146, 2001.
46. Popov, J. Geophys. Res., v. 107, no. B11, 2002.
47. Psarchik, Proc. VSEGEI, v. 89, 1963.
48. Rodionov, Paleomagnetic Methods in Stratigraphy, 1984.
49. Rozanov, The Cambrian of Siberia, 1992.
50. Rozanov, Stratigraphy, Geol. Correlation, v. 5, no. 1, 1997.
51. Rozen, Collision Granitoids and the Layering of the Earth Crust, 2001.
52. Sovetov, Geology, Geochemistry, and Geophysics at the Boundary of the XX and XXI Centuries, 2002.
53. Sovetov, Geology, Geochemistry, and Geophysics at the Boundary between the XX and XXI centuries, 2002.
54. Sokolov, The Analogs of Vendian Rocks in Siberia, 1975.
55. Sokolov, Essays on Vendian Rock Accumulation, 1997.
56. Shatsillo, The principles of construction of apparent polar wander parths, 2005.
57. Shatsillo, Paleomagnetism and Magnetism of Rocks, 2001.
58. Shipunov, Phys. Solid Earth, v. 31, no. 4, 1995.
59. Shipunov, Phys. Solid Earth, v. 36, no. 7, 2000.
60. Smethurst, Earth Sci. Rev., v. 43, 1998.
61. Smethurst, Geophys. J. Int., v. 133, 1998.
62. Symons, Can. J. Earth Sci., v. 28, 1991.
63. Tanczyk, Can. J. Earth Sci., v. 24, 1987.
64. Torsvik, Science, v. 279, 1998.
65. Torsvik, Earth Sci. Rev., v. 40, 1996.
66. Torsvik, J. Geol. Soc. London, v. 158, 2001.
67. Tucker, Can. J. Earth Sci., v. 32, 1995.
68. Van Alstine, J. Geophys. Res., v. 84, 1979.
