Early Phanerozoic events on and alongside the Australasian‐Antarctic platform

Abstract

The major geological events on and alongside the Australasian‐Antarctic platform during the first half of the Phanerozoic (∼600–300 m.y. ago) are interpreted as repercussions of the first‐order events that took place along the Pacific and Tethyan margins. In turn, the clear signal of platform events provides a means of deciphering the noisy record of events in the mobile belt that accreted along the Pacific margin. Thus, in the Late Vendian and Early Cambrian, widespread eruption of basalt on the Australian platform, the inception or rejuvenation of aulacogens, and deformation in the Petermann, Peak‐Denison, and Adelaide areas and in parts of the Transantarctic Mountains, and the initial deposition of flysch of the Tasmanides, followed by widespread marine transgression of the platform, mark the inception of the Pacific and Tethyan margins of Australia. In the Early Ordovician the initial subsidence of the Canning and Carnarvon/Perth Basins marks the complete outlining of the Tethyan margin, and plutonism and deformation along the Pacific margin of Antarctica and Australia and the isotopic re‐arrangement of East Antarctica mark a rapid outburst of heat. Events following on this initial geotectonic episode, and overprinted by the secondary Gondwanan cycle, have persisted to the present day. The inception of the Pacific and Tethyan margins of Australia in the earliest Phanerozoic, at the same time as the appearance of shelled metazoans, corresponds with a rapid change in palaeolatitude; whether this is cause and effect remains a subject for further study.