Book contents
- Frontmatter
- Contents
- Colophon
- Preface
- Acknowledgements
- Maps
- Units of measurement and abbreviations
- 1 Geology: An Australian perspective
- 2 The Earth: A geology primer
- 3 Telling geological time: The great canvas
- 4 The cratons: Building the core of Precambrian rocks
- 5 Mountain building: Paleozoic orogenic rock systems
- 6 Warm times: Tropical corals and arid lands
- 7 Icehouse: Carboniferous and Permian glaciation
- 8 Mesozoic warming: The great inland plains and seas
- 9 The birth of modern Australia: Flowering plants, mammals and deserts
- 10 Fossils: The Australian record of past life in context
- 11 The land stirs: Volcanoes and the eastern highlands
- 12 The outline and submerged terrace: Building the continental shelf and coastlines
- 13 The coral reefs: Unique parts of the continental shelf
- 14 Patterns of change: Cycles in Australia's journey
- Epilogue
- Sources and references
- Index
- References
6 - Warm times: Tropical corals and arid lands
- Frontmatter
- Contents
- Colophon
- Preface
- Acknowledgements
- Maps
- Units of measurement and abbreviations
- 1 Geology: An Australian perspective
- 2 The Earth: A geology primer
- 3 Telling geological time: The great canvas
- 4 The cratons: Building the core of Precambrian rocks
- 5 Mountain building: Paleozoic orogenic rock systems
- 6 Warm times: Tropical corals and arid lands
- 7 Icehouse: Carboniferous and Permian glaciation
- 8 Mesozoic warming: The great inland plains and seas
- 9 The birth of modern Australia: Flowering plants, mammals and deserts
- 10 Fossils: The Australian record of past life in context
- 11 The land stirs: Volcanoes and the eastern highlands
- 12 The outline and submerged terrace: Building the continental shelf and coastlines
- 13 The coral reefs: Unique parts of the continental shelf
- 14 Patterns of change: Cycles in Australia's journey
- Epilogue
- Sources and references
- Index
- References
Summary
After the enormous time span of the Precambrian, lasting 4 billion years (4 Ga), complex life suddenly burst forth in an astonishing array within just a few million years. Eastern Australia came under the sway of a nearby convergent plate boundary which strongly influenced its character. It was episodically the site of widespread igneous activity and prominent mountains generating voluminous erosion products. The sedimentary rocks which resulted are now an important part of the continental fabric. The span of this chapter covers 182 Ma, comprising 56 million years in the Cambrian (541–485 Ma), 42 million years in the Ordovician (485–443 Ma), 24 million years in the Silurian (443–419 Ma) and 60 million years in the Devonian (419–359 Ma).
PART OF GONDWANA
During the Paleozoic, between 541 and 252 Ma, there was no Australia as it is known today. The present Australia was just a segment of eastern Gondwana embedded in continental crust of much larger extent within a single tectonic plate. Australia was continuous with Antarctica to the south and India to the west. Continental crust now embedded in Asia adjoined present Australia to the northwest. For most of the Cambrian the eastern Gondwanan margin that included Australia faced deep ocean built by seafloor spreading following the breakup of the supercontinent Rodinia, in the late Proterozoic (see Chapter 4). Contemporary research indicates that Tasmania was a separate microcontinent located in the ocean beyond Australia and independent in its history. In proto-Australia's northern part, stretching eastwards from the Kimberley region, within-plate, hotspot-related volcanism generated extensive basaltic fields.
However, in the late Cambrian, at about 500 Ma, the plate geometry changed. From that time onwards through the Paleozoic the ocean-facing part of eastern Gondwana, including the Australian segment, lay close to a convergent plate boundary, with the Paleo-Pacific Ocean floor being consumed by subduction (see Figure 5.1). As a consequence, eastern Australia was transformed into an active continental margin characterised by magmatism, the accumulation of very large-scale sedimentary systems and mountain building. Changing stress regimes along the margin reflected contrasting episodes of plate boundary advance characterised by crustal compression, widespread thickening and mountain building, and by plate boundary retreat characterised by crustal extension, widespread thinning and sedimentary basin formation (see Chapter 5).
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- The Geology of Australia , pp. 131 - 146Publisher: Cambridge University PressPrint publication year: 2016