PALEOZOIC SUPERCONTINENTAL ASSEMBLY, MANTLE FLUSHING, AND GENESIS OF THE KIAMAN SUPERCHRON

Abstract

Two intrinsically different processes, break-up of supercontinents after mantle insulation (‘hot-spots’) and early formation of supercontinents after mantle cooling (‘cold-spots’), show causal links with periods of low reversal rates (superchron events). The formation of Pangea in the Permo-Carboniferous, coincident with onset of the Kiaman Reverse Superchron (KRS), is conceptually different from traditional mantle plume models commonly invoked for genesis of the Cretaceous Normal Superchron. We propose that prolonged subduction and flushing of cold lithospheric material into the lower mantle preceding Pangea amalgamation resulted in persistent cold anomalies at the core-mantle boundary (CMB); large thermal contrasts at the CMB caused variation in circulation patterns in the outer core, and resulted in a change in the geomagnetic field manifested by onset of the KRS in late Palaeozoic time. The correlations we draw between core and crustal processes in the Palaeozoic are supported by paleomagnetic and tectonic data but still beg the question of the role played by true polar wander (TPW).