A third superchron during the Early Paleozoic

摘要

Research on geomagnetic reversal chronology has established the existence of two superchrons, one during the Cretaceous and the other (Kiaman) during the Late Paleozoic.Over the past few years, we have performed several magnetostratigraphic studies on Early Paleozoic (Cambrian and Ordovician) sedimentary sequences from Siberia. Our results show high magnetic reversal frequencies during the Middle Cambrian. In contrast, several records show the occurrence of a -20 Myr long reversed polarity interval in the Lower and Middle Ordovician, suggesting the presence of a third superchron. We propose to give the name of “Moyero” to this new superchron; this name is attributed to the Siberian section which first yielded a complete record of this reversed polarity interval.