THE REGIONAL TECTONICS OF THE TASMAN OROGENIC SYSTEM, EASTERN AUSTRALIA

From the perspective of Phanerozoic mountain belts the mostly Paleozoic Tasman orogenic system of eastern Australia is unique. For example, it has no through-going miogeocline or foreland fold and thrust belt. Except for a narrow deformed fringe along its western margin the entire system is 'suspect' in the sense that its paleogeography is uncertain through much of Paleozoic time. The tectonic evolution of the Tasman orogenic system is composed of four major phases. The first was a prolonged late Proterozoic-early Paleozoic period of variable tectonic settings characterized by generally deep-marine turbiditic sedimentation and submarine volcanism, and shifting, somewhat local, deformation, metamorphism and plutonism. The second epoch was a major mid-Paleozoic period of deformation, volcanism and plutonism that consolidated a belt of lower Paleozoic interior terranes into Australia. The third epoch was a major accretionary phase in the outer New England belt of terranes that culminated in late Paleozoic time, and continued into the early Mesozoic. The final epoch was extensional, and was due to the break-up of Gondwanaland in late Mesozoic time, continuing to the present. Tectonic evolution during the first three phases was somewhat similar to that of the remainder of the nearly 20,000 km long Pacific margin of Gondwanaland in the Andes and Antarctica, and suggests that 'absolute' motions of Gondwanaland itself prior to break-up may have influenced the tectonics of its Pacific margin. © 1990.