The East European Craton in the Mesoproterozoic: New Key Paleomagnetic Poles

摘要

At the present time, the "key poles" satisfying several criteria [1] are used in reconstructions of the Pre-cambrian supercontinents: paleomagnetic measurements have to be made on magmatic rocks (mainly,rndykes and sills) of age, obtained by applying the U-Pb method to baddeleite with an accuracy of no less ±20 Ma; the thermoremanent nature of magnetization, whose originality is confirmed by tests of paleo-rnmagnetic reliability (contact and inversion), has to be proved; averaging of secular variations, if the age period of the rocks sampled exceeds 40 000 years; and paleomagnetic poles, obtained for coeval rocks, not subjected to the late secondary alterations have to coincide among themselves in different parts of the same block.