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Sydney Basin

February 28, 2023

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.

Sydney Basin
New South Wales
Map of the Sydney Basin
The interim Australian bioregions,
with the Sydney Basin in red
Coordinates33°56′53″S 150°45′36″E / 33.94806°S 150.76000°E / -33.94806; 150.76000Coordinates: 33°56′53″S 150°45′36″E / 33.94806°S 150.76000°E / -33.94806; 150.76000
Population5,000,000[1]
 • Density78/km2 (202/sq mi)
Area64,000 km2 (24,710.5 sq mi)[2]
Mean max temp Mean min temp Annual rainfall[1]
 ? ? 650−1,300 mm
598.8 in

Around 5,000 metres (16,000 ft) 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.[3]

Geography

According to NSW Primary Industries, the basin extends through approximately 350 kilometres (220 mi) of coastline from Newcastle in the north to Durras Lake (near Batemans Bay) in the south. From Durras Lake the western boundary continues in a line through Lithgow to around Ulan (near Mudgee). To the north the boundary extends 120 kilometres (75 mi) along the Liverpool Range to a point 80 kilometres (50 mi) north of Muswellbrook, and then runs 200 kilometres (120 mi) back to the coast at Newcastle. To the east the basin continues to the edge of the continental shelf.[4]

The total area of the basin is approximately 44,000 square kilometres (17,000 sq mi) onshore plus 5,000 square kilometres (1,900 sq mi) offshore.[5] The centre of the basin is located around 30 kilometres (19 mi) west of the Sydney central business district at Fairfield, though only the youngest Triassic (middle Triassic) rocks are exposed in the Sydney area.[6]

The Australian Government Department of Agriculture, Water and the Environment classifies the basin as an interim Australian bioregion consisting of 3,629,597 hectares (8,968,930 acres).[7] Meanwhile, according to Geoscience Australia the basin covers 64,000 square kilometres (25,000 sq mi), of which 36,000 square kilometres (14,000 sq mi) is onshore and 28,000 square kilometres (11,000 sq mi) is offshore with water depths of up to 4,500 metres (14,800 ft).[2] Another Australian Government agency classifies that the basin covers approximately 25,000 square kilometres (9,700 sq mi).[1]

History and formation

 
The majority of Sydney Basin is raised sandstone plateau, with the exclusion being the Hunter Valley and the low-lying Cumberland Plain.

Minor igneous activity took place in the basin during the Early Jurassic (i.e. 210 million years ago), Late Mesozoic (i.e. 100-90 million years ago) and Cenozoic eras (i.e. 65 million years ago). The Early Jurassic activity resulted in the formation of the Prospect dolerite intrusion in Prospect Hill.[8] Although Jurassic sedimentation is not observed in the Sydney Basin, there are Jurassic volcanic breccia pipes (diatremes).[9]

The Sydney Basin is part of a major basin system that extends over 1,500 kilometres (930 mi) from the Bowen Basin in Queensland through to the Gunnedah Basin in NSW. Onshore, the basin contains 4,500 metres (14,800 ft) of Permo-Triassic clastic sediments, while the offshore basin contains 6,000 metres (20,000 ft) of sediments. The basin overlies the Lachlan Fold Belt and Late Carboniferous volcanoclastic sediments. The basin formed during extension in the Early Permian, with half-graben infilled with the Dalwood and Talaterang Groups. Foreland loading followed with the compression of the Currarong Orogen in the Early Permian.[10]

Late Permian uplift associated with the New England foreland loading phase resulted in the formation of depocentres with the northeast Sydney Basin with best preserved marine fossils. These depocentres filled with pyroclastic and alluvial-paludual sediments of the Newcastle Coal Measures. In the Triassic, uplift of the offshore basin resulted in reworking of Permian sediments in fluvial environments. The basin underwent a final phase of deformation (thrusting) in the Middle Triassic where it was uplifted to become dry land, with an erosion occurring from this time to the present.

Extension and breakup in the Tasman Sea beginning in the Late Cretaceous resulted in the current structural boundaries of the basin's eastern margin. In the south and west the Basin finishes in cliff lines formed on sandstones and conglomerates of the primary Permian sediments, with waterfalls being widespread on all escarpments.[2]

Timeline

 
The Prospect dolerite intrusion in Greater Western Sydney
  • 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. The Australian continent was part of the Gondwana supercontinent and the Sydney basin was situated within a depositional basin. The Ashfield Shale, which overlies the Sydney sandstone, indicates an alteration in river flow direction and its depositional style. That was when southeast-streaming rivers deposited fine grained sands and muds within a river delta which settled on a shallow sea's shore.[11]
  • 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,[12] 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.[13]
  • Cainozoic (Tertiary and Quaternary): 66 million years to present; Gondwana broke up around 40 to 60 million years ago. That is when the Australian continent started to form where it drifted and rifted, where Sydney's rocks were elevated, canted and then later eroded by the weather. Sydney's sedimentary rocks were shaped into a landscape that was defined by bedrock valleys exposed into a raised plateau. Sydney's largest rivers, such as the Hawkesbury, Parramatta, Georges and Hacking Rivers eroded the region's deepest valleys. In this period, the Ashfield Shale got weathered to create a flatter landform with low, undulating topography and reasonably fertile soils, which heavily contrasted the plateaus, cliffs and gorges on the sandstone areas in the Sydney Region.[11] The Botany Bay Basin was also developed at that time, which is infilled with sand.
  • Late Pleistocene: 12 000 years ago; Submerging the Sydney river valleys with the post-glacial sea level rise where estuaries and deep harbours were formed.[14]

Hydrology

The hydrology of the basin comprises three main drainage basins as defined by the New South Wales Office of Water that lie entirely or mainly within the geography of the basin; namely the Central Coast catchment, the Hawkesbury-Nepean catchment, and the Sydney Metropolitan catchment.

In addition, some of the rivers of the Hunter-Central Rivers catchment and the Southern Rivers catchment also lie mainly in the basin. In the Hunter-Central Rivers catchment, the Hunter River sub-catchment forms the northern boundary of the basin. In the Southern Rivers catchment, the Illawarra sub-catchment and the Shoalhaven sub-catchment forms the southern boundary.

See also

References

  1. ^ a b c "Sydney Basin bioregion". Bioregional assessments. Australian Government. 28 September 2016. Retrieved 25 March 2018.
  2. ^ a b c "Sydney Basin". Geoscience Australia. Australian Government. 2018. Retrieved 25 March 2018.
  3. ^ Herbert, C., 1983. Geology of the Sydney Basin 1: 100 000 sheet 9130. New South Wales Department of Mineral Resources, Sydney.
  4. ^ "Sydney Basin Structure Diagram". NSW Primary Industries. Retrieved 24 March 2008.
  5. ^ "Development of the Sydney Basin". NSW Primary Industries. Retrieved 24 March 2008.
  6. ^ "Sydney Basin – Geological Overview". Australian Museum. Retrieved 24 March 2008.
  7. ^ "Australia's bioregions (IBRA)". Department of Sustainability, Environment, Water, Population and Communities. Commonwealth of Australia. 2012. Retrieved 13 January 2013.
  8. ^ Jones, I., and Verdel, C. (2015). Basalt distribution and volume estimates of Cenozoic volcanism in the Bowen Basin region of eastern Australia: Implications for a waning mantle plume. Australian Journal of Earth Sciences, 62(2), 255–263.
  9. ^ Robert Wallace Johnson (24 November 1989). Intraplate Volcanism: In Eastern Australia and New Zealand. Cambridge University Press. pp. 4–. ISBN 978-0-521-38083-6.
  10. ^ Crawford, E. A., Herbert, C., Taylor, G., Helby, R., Morgan, R. & Ferguson, J., 1980 – 15. Diatremes of the Sydney Basin, p. 295-323., In Herbert, C. & Helby, R. (Editors.) – A Guide to the Sydney Basin. Geological Survey of New South Wales, Bulletin 26.20(1),25–33.
  11. ^ a b Geological History by Sydney Olympic Park.gov.au
  12. ^ Jones, I., Verdel, C., Crossingham, T., and Vasconcelos, P. (2017). Animated reconstructions of the Late Cretaceous to Cenozoic northward migration of Australia, and implications for the generation of east Australian mafic magmatism. Geosphere, 13(2), 460–481.
  13. ^ Wilshire: Wilshire, H.G., The Prospect alkaline diabase-picrite intrusion, New South Wales, Australia in Journal of Petrology, Vol. 8 (1), pp 97–163, 1967.
  14. ^ Branagan, D.F., and Packham, G.H., 2000. Field Geology of New South Wales. 3rd Edition. New South Wales Department of Mineral Resources, Sydney.

Attribution

  This article incorporates text by Commonwealth of Australia (Geoscience Australia) 2018., available under the CC BY 4.0 license. (accessed on 25 March 2018).

External links

  • NSW National Parks and Wildlife Service – Sydney Basin Bioregion
  • NSW Department of Primary Industries – Sydney Basin – Geological Overview
  • NSW Office of Water – Basins and catchments

February 28, 2023
sydney, basin, interim, australian, bioregion, both, structural, entity, depositional, area, preserved, east, coast, south, wales, australia, with, some, eastern, side, subsided, beneath, tasman, basin, named, city, sydney, which, centred, south, walesmap, int. 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 Sydney Basin New South WalesMap of the Sydney BasinThe interim Australian bioregions with the Sydney Basin in redCoordinates33 56 53 S 150 45 36 E 33 94806 S 150 76000 E 33 94806 150 76000 Coordinates 33 56 53 S 150 45 36 E 33 94806 S 150 76000 E 33 94806 150 76000Population5 000 000 1 Density78 km2 202 sq mi Area64 000 km2 24 710 5 sq mi 2 Mean max temp Mean min temp Annual rainfall 1 650 1 300 mm 598 8 inLocalities around Sydney Basin South Eastern Highlands North Coast Tasman SeaSouth Eastern Highlands Sydney Basin Tasman SeaAustralian Alps South Coast Tasman SeaAround 5 000 metres 16 000 ft 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 3 Contents 1 Geography 2 History and formation 2 1 Timeline 3 Hydrology 4 See also 5 References 5 1 Attribution 6 External linksGeography EditAccording to NSW Primary Industries the basin extends through approximately 350 kilometres 220 mi of coastline from Newcastle in the north to Durras Lake near Batemans Bay in the south From Durras Lake the western boundary continues in a line through Lithgow to around Ulan near Mudgee To the north the boundary extends 120 kilometres 75 mi along the Liverpool Range to a point 80 kilometres 50 mi north of Muswellbrook and then runs 200 kilometres 120 mi back to the coast at Newcastle To the east the basin continues to the edge of the continental shelf 4 The total area of the basin is approximately 44 000 square kilometres 17 000 sq mi onshore plus 5 000 square kilometres 1 900 sq mi offshore 5 The centre of the basin is located around 30 kilometres 19 mi west of the Sydney central business district at Fairfield though only the youngest Triassic middle Triassic rocks are exposed in the Sydney area 6 The Australian Government Department of Agriculture Water and the Environment classifies the basin as an interim Australian bioregion consisting of 3 629 597 hectares 8 968 930 acres 7 Meanwhile according to Geoscience Australia the basin covers 64 000 square kilometres 25 000 sq mi of which 36 000 square kilometres 14 000 sq mi is onshore and 28 000 square kilometres 11 000 sq mi is offshore with water depths of up to 4 500 metres 14 800 ft 2 Another Australian Government agency classifies that the basin covers approximately 25 000 square kilometres 9 700 sq mi 1 History and formation Edit The majority of Sydney Basin is raised sandstone plateau with the exclusion being the Hunter Valley and the low lying Cumberland Plain Minor igneous activity took place in the basin during the Early Jurassic i e 210 million years ago Late Mesozoic i e 100 90 million years ago and Cenozoic eras i e 65 million years ago The Early Jurassic activity resulted in the formation of the Prospect dolerite intrusion in Prospect Hill 8 Although Jurassic sedimentation is not observed in the Sydney Basin there are Jurassic volcanic breccia pipes diatremes 9 The Sydney Basin is part of a major basin system that extends over 1 500 kilometres 930 mi from the Bowen Basin in Queensland through to the Gunnedah Basin in NSW Onshore the basin contains 4 500 metres 14 800 ft of Permo Triassic clastic sediments while the offshore basin contains 6 000 metres 20 000 ft of sediments The basin overlies the Lachlan Fold Belt and Late Carboniferous volcanoclastic sediments The basin formed during extension in the Early Permian with half graben infilled with the Dalwood and Talaterang Groups Foreland loading followed with the compression of the Currarong Orogen in the Early Permian 10 Late Permian uplift associated with the New England foreland loading phase resulted in the formation of depocentres with the northeast Sydney Basin with best preserved marine fossils These depocentres filled with pyroclastic and alluvial paludual sediments of the Newcastle Coal Measures In the Triassic uplift of the offshore basin resulted in reworking of Permian sediments in fluvial environments The basin underwent a final phase of deformation thrusting in the Middle Triassic where it was uplifted to become dry land with an erosion occurring from this time to the present Extension and breakup in the Tasman Sea beginning in the Late Cretaceous resulted in the current structural boundaries of the basin s eastern margin In the south and west the Basin finishes in cliff lines formed on sandstones and conglomerates of the primary Permian sediments with waterfalls being widespread on all escarpments 2 Timeline Edit The Prospect dolerite intrusion in Greater Western Sydney 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 The Australian continent was part of the Gondwana supercontinent and the Sydney basin was situated within a depositional basin The Ashfield Shale which overlies the Sydney sandstone indicates an alteration in river flow direction and its depositional style That was when southeast streaming rivers deposited fine grained sands and muds within a river delta which settled on a shallow sea s shore 11 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 12 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 13 Cainozoic Tertiary and Quaternary 66 million years to present Gondwana broke up around 40 to 60 million years ago That is when the Australian continent started to form where it drifted and rifted where Sydney s rocks were elevated canted and then later eroded by the weather Sydney s sedimentary rocks were shaped into a landscape that was defined by bedrock valleys exposed into a raised plateau Sydney s largest rivers such as the Hawkesbury Parramatta Georges and Hacking Rivers eroded the region s deepest valleys In this period the Ashfield Shale got weathered to create a flatter landform with low undulating topography and reasonably fertile soils which heavily contrasted the plateaus cliffs and gorges on the sandstone areas in the Sydney Region 11 The Botany Bay Basin was also developed at that time which is infilled with sand Late Pleistocene 12 000 years ago Submerging the Sydney river valleys with the post glacial sea level rise where estuaries and deep harbours were formed 14 Hydrology EditThe hydrology of the basin comprises three main drainage basins as defined by the New South Wales Office of Water that lie entirely or mainly within the geography of the basin namely the Central Coast catchment the Hawkesbury Nepean catchment and the Sydney Metropolitan catchment In addition some of the rivers of the Hunter Central Rivers catchment and the Southern Rivers catchment also lie mainly in the basin In the Hunter Central Rivers catchment the Hunter River sub catchment forms the northern boundary of the basin In the Southern Rivers catchment the Illawarra sub catchment and the Shoalhaven sub catchment forms the southern boundary See also Edit New South Wales portal Geography portal Geology portal Cumberland Plain Geography of Sydney Geology of Australia Illawarra Coal Measures Mittagong Formation Narrabeen group Sydney sandstone Wianamatta ShaleReferences Edit a b c Sydney Basin bioregion Bioregional assessments Australian Government 28 September 2016 Retrieved 25 March 2018 a b c Sydney Basin Geoscience Australia Australian Government 2018 Retrieved 25 March 2018 Herbert C 1983 Geology of the Sydney Basin 1 100 000 sheet 9130 New South Wales Department of Mineral Resources Sydney Sydney Basin Structure Diagram NSW Primary Industries Retrieved 24 March 2008 Development of the Sydney Basin NSW Primary Industries Retrieved 24 March 2008 Sydney Basin Geological Overview Australian Museum Retrieved 24 March 2008 Australia s bioregions IBRA Department of Sustainability Environment Water Population and Communities Commonwealth of Australia 2012 Retrieved 13 January 2013 Jones I and Verdel C 2015 Basalt distribution and volume estimates of Cenozoic volcanism in the Bowen Basin region of eastern Australia Implications for a waning mantle plume Australian Journal of Earth Sciences 62 2 255 263 Robert Wallace Johnson 24 November 1989 Intraplate Volcanism In Eastern Australia and New Zealand Cambridge University Press pp 4 ISBN 978 0 521 38083 6 Crawford E A Herbert C Taylor G Helby R Morgan R amp Ferguson J 1980 15 Diatremes of the Sydney Basin p 295 323 In Herbert C amp Helby R Editors A Guide to the Sydney Basin Geological Survey of New South Wales Bulletin 26 20 1 25 33 a b Geological History by Sydney Olympic Park gov au Jones I Verdel C Crossingham T and Vasconcelos P 2017 Animated reconstructions of the Late Cretaceous to Cenozoic northward migration of Australia and implications for the generation of east Australian mafic magmatism Geosphere 13 2 460 481 Wilshire Wilshire H G The Prospect alkaline diabase picrite intrusion New South Wales Australia in Journal of Petrology Vol 8 1 pp 97 163 1967 Branagan D F and Packham G H 2000 Field Geology of New South Wales 3rd Edition New South Wales Department of Mineral Resources Sydney Attribution Edit This article incorporates text by Commonwealth of Australia Geoscience Australia 2018 available under the CC BY 4 0 license accessed on 25 March 2018 External links EditNSW National Parks and Wildlife Service Sydney Basin Bioregion NSW Department of Primary Industries Sydney Basin Geological Overview NSW Office of Water Basins and catchments Retrieved from https en wikipedia org w index php title Sydney Basin amp oldid 1090264930, wikipedia, wiki, book, books, library,

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