page_title: Sydney Basin
section_title: Timeline
hierarchical_section_title: Sydney Basin / Formation / Timeline
caption_attribution_description: Dolerite intrusion or igneous rocks at Prospect Hill, Sydney.
context_page_description: The Sydney Basin is an interim Australian bioregion and is both a structural entity and a depositional area, now preserved on the east coast of New South Wales, Australia and with some of its eastern side now subsided beneath the Tasman Sea. The basin is named for the city of Sydney, on which it is centred.
  Around 5,000 metres thick, the Sydney Basin consists of Permian and Triassic sedimentary rocks, which stretches from Newcastle in the north to Batemans Bay in the south, and west to the Great Dividing Range. The basin is also home to the major centres of Newcastle and Wollongong, and contains economically significant reserves of coal.
  Sydney's famous harbour and the sculptured cliffs of the Blue Mountains are signature formations of relatively hard upper strata of sandstone. The basin contains the UNESCO World Heritage-listed Greater Blue Mountains Area.
context_section_description: Permian: 299–252 million years ago; The settling and evolution of swamp forest, which would shape tremendous coal measures. To note, Australia's coal is younger than the Carboniferous coal of the Northern Hemisphere.
  Early Triassic: 252–247 million years ago; dark, high-carbon Narrabeen shales can be viewed at Long Reef and Narrabeen.
   Mid Triassic: 247–235 million years ago; A monolithic river with its beginnings to the south-west of Broken Hill, in what was Antarctica at that time, had its delta in what was the Sydney Basin. It is around five times bigger than the Amazon river. There is predominance of silica sand with minor lenses of clay. Plant fossils are scarce, but some fish fossils are found in the clay lenses.
  Late Triassic: 235–201 million years ago; As the river slowed with the erosion of the mountain range, finer shales were laid out. This strata is rich in Glossopteris fern fossils.
  End of Triassic: 201 million years ago; Ascension and shifting at the Lapstone fault, with the Blue Mountains rising and the western Sydney plain descending to a flat land and Sydney CBD jousting upward.
  Jurassic: 201–145 million years ago; Erosion, with Ashfield Shales remaining on top. Deep V-shaped valleys in the Hawkesbury sandstone. Fracturing, volcanic intrusions form Prospect Quarry, Mount Tomah, Mount Wilson and Hornsby Quarry.
  Cainozoic (Tertiary and Quaternary): 66 million years to present; Development of the Botany Bay Basin, which is infilled with sand.
  Late Pleistocene: 12 000 years ago; Submerging the Sydney river valleys with the post-glacial sea level rise.
caption: The Prospect dolerite intrusion in Greater Western Sydney
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