ИСТИНА

Evidence to the joint movement of large cratonic blocks is a solid argument in favour of the existence of an early Proterozoic supercontinent. The basic method of reconstruction of the relative positions of cratons is construction and comparison of the apparent polar wander paths (APWP) for them. Until recently, there have practically been no paleomagnetic data for the Siberian craton. A number of paleomagnetic poles on securely dated rocks with positive reliability tests have been obtained in the last few years. These poles constitute the Siberia APWP in the ungrounded loop form. Mesoproterozoic poles of Western Anabar (Veselovsky et al., 2009) and Olenek Uplift (Wingate et al., 2009) were also used. They illustrate the general trend in the Siberia APWP. A new APWP can be used to reconstruct the position of Siberia and Laurentia relative each other at the end of the Paleoproterozoic. The dataset (Personen et al., 2003) shows that over the time span between 1870 and 1760 Ma the Laurentia APWP is similar to that of Siberia. The Euler pole yielded the best overlap of segments of Siberia and Laurentia APWPs: Lat=75о, Long=110о, angle =165о. When rotated about this pole, the southern edge of the Siberian craton overlaps the Laurentia northern margin. Such a correlation was reported based on geologic data (Rainbird et al., 1998; Condi, 2002; Rosen et al., 2006; Larin, 2011). Joint migration of Siberia and Laurentia as part of the single rigid plate is a strong argument in favour of the existence of the supercontinent Columbia. Baltica formed at around 1.75 Ga at the end of the Early Proterozoic (Lubnina, 2009). It may have been part of the supercontinent Columbia throughout the Mesoproterozoic when its northern edge was joined to the Laurentia north-eastern margin. According to Condie (2002), the main phases of the rifting process which resulted in the breakup of the Paleoproterozoic supercontinent occurred at 1.4 Ga. Geologic data on the southern Siberian craton are indicative of its stable development with a predominance of platform sedimentation regimes and intraplate extension at 1.8-1.0 Ga (Gladkochub et al., 2003, 2008). Proceeding from this, we believe that the southern flank of the Siberian craton was in the interior of the fragment which survived the breakup of the supercontinent up to the formation of the Neoproterozoic supercontinent. The relative positions of Siberia and Laurentia reconstructed based on the individual Paleo- and Mesoproterozoic poles show similar configuration. The breakup followed by the arrangement in the same configuration 300-350 Ma later is unlikely. It is more likely that the stable agglomerate of Siberia and Laurentia existed for 800 Ma. This suggests the possible existence of the transprecambrian agglomerate joining Siberia and Laurentia. Having analyzed the published paleomagnetic data on Siberia, Laurentia and Baltica, the authors (Evans, Mitchell, 2011) came to a similar conclusion, i.e. the agglomerate of these three blocks in the configuration similar to ours existed for a long time (1.9-1.3 Ga) as a core of the transproterozoic supercontinent.