On Two Types of Supercontinental Cyclicity

摘要

Analysis of tectonic events during the last 3 Ga of the Earth’s evolution, when 400 Ma global supercontinent cyclicities dominated, identified two types of supercontinental cycles. These types differ by the degree of breakup of a supercontinent that starts a cycle. Supercontinental cycles of the first type are char-acterized by a scattered and relatively even global distribution of the supercontinent split into numerous con-tinents and oceans. Supercontinental cycles of the second type are characterized by uneven “incomplete” supercontinental breakups, which are localized alternately in either the Northern or the Southern Hemi-sphere, whereas a significant part remains after the breakup. These supercontinental cycle types followed each other composing pairs of megacycles that were 800 Ma long until ca. 700 Ma. Every megacycle consisted of two supercontinental cycles of different types; however, after the breakup of Rodinia, virtually only the sec-ond type of supercontinental cycle has been observed. The different degrees of the breakup of superconti-nents, which are reflected in the two supercontinental-cycle types, may be caused by uneven heating of the mantle produced by supercontinents owing to the thermal blanket effect.