ИСТИНА

The existence of a long interval of reverse geomagnetic polarity (the Haidar zone) near the Cambrian- Ordovician boundary was first proposed by A.N. Khramov and V.P. Rodionov (1976). According to these authors, this interval occupied a significant part of the late Cambrian and lasted almost until the end of the Tremadocian time. Subsequently, partly due to detalization of the magnetostratigraphic studies, partly due to specification of the stratigraphic boundary positions, it was shown that considered time interval includes in nearly equal proportion both normal and reverse polarity zones and, there can't be considered as indication on any geomagnetic polarity bias. On the other hand, on the basis of detailed magnetostratigraphic studies of one of the best Siberian key sections of the Ordovician, located along the Moyero River (Northern Siberian Platform), the existence of a long reverse polarity interval in Arenig, Llanvirn and most of Llandeilo (Floian, Dapingian, Darriwillian) was shown (Pavlov and Gallet, 2006). The duration of this interval is estimated at about 15-20 million years. Therefore, Pavlov and Galle (2006) proposed to consider this interval as a geomagnetic polarity superchron and gave it the name “Moyero superchron”. Being generally consistent with the magnetostratigraphic record from the East European Platform (Torsvik and Trench, 1993, etc.), the above conclusion somewhat contradicted the observations of one or two intervals of normal polarity in some Scandinavian sections, determined, however, only by one or two samples each. Further investigation of other Siberian thick sections (Kulumbe, Rozhkova–Pavlov et al., (1998, 2004)) It revealed clear evidence confirming the existence of the Moyero superchron, and it seemed that the issue was closed. However, new data recently published by Hounslow et al., 2021 may indicate that the upper limit of the Moyero superchron should be drawn much lower than suggested by Pavlov and Gallet (2006). In our report we consider these data and show our new results which confirm and, even, lift a little to younger times, the upper boundary of the Moyero superchron, suggested earlier. This work was supported by RSF grant 20-17-00198.