Phanerozoic Australia in the Changing Configuration of Proto-Pangea Through Gondwanaland and Pangea to the Present Dispersed Continents

Abstract

The neotectonic supercycle of earth history started 320 million years ago with the initial coalescence of the continents in Pangea. Final coalescence took place 230 Ma ago at the same time as rift valleys induced incipient breakup that became actual from 160 Ma with the start of seafloor spreading in the Atlantic and Indian Oceans. The current phase of seafloor spreading is marked by the growth lines of magnetic anomalies, from which reconstructions of the continents during the past 160 Ma are accurately determinable by eliminating the dated parts of the seafloor. Many small terranes or fragments are not so well constrained. Palaeolatitude is less precisely determined by continental indicators of magnetic inclination. All this physical evidence provides a unique solution for continental reconstruction since 320 Ma. Less definite evidence provided by biota and geological facies has to be accommodated within this physical framework. Before the coalescence of Pangea (> 320 Ma) the constraints are reversed. This paleotectonic phase lacks preserved seafloor spreading so that continental palaeomagnetism, biota and geological facies are the only indicators. The changing configuration of Australia and its neighbours in the eastern Gondwanaland province of Pangea - India, Antarctica, Lord Howe Rise-New Zealand Plateau - is detailed through seven stages from the midJurassic breakup of Pangea