Authors / CoAuthors
Collins, C.D.N. | Drummond, B.J.
Abstract
The thickness of the crust is usually defined seismologically by the depth to the Mohorovicic discontinuity or Moho. The Moho is defined as the boundary below which the seismic p-wave velocity of the rocks increases to values above about 7.8 km/s. These velocities are typical for mantle rocks under the expected temperature and pressure conditions. There are arguments that the Moho may not always be the base of the crust from a petrological point of view. In any case, the transition from crustal to mantle compositions may be gradational, and this is reflected by the common observation of a velocity gradient at the base of the crust.There are significant variations in the depth of the Moho under Australia. In general, within the Archean regions of Western Australia the Moho is relatively shallow with a large velocity contrast at the transition between the crust and the mantle. It is significantly deeper under the Proterozoic North Australian Platform, under Central Australia and Phanerozoic Southeastern Australia. Thicker crust in general is reflected in higher surface elevation, although the relationship between crustal thickness and elevation is not linear. Where the Moho is deep there is a very broad transition from crustal to mantle velocities. Other regions of Australia for which data exist generally have average depths to Moho.Crustal thickness patterns reflect the mechanisms of continental growth and tectonic evolution. The relative thickness of the upper and lower crust are characteristic of various styles of extensional or compressional tectonics and other processes such as underplating. Images across the Australian continental margin clearly demonstrate the role that upper and lower crustal extension have on crustal growth, by sedimentary deposition and magmatic emplacement on and within the attenuated crust.
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nonGeographicDataset
eCat Id
32946
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Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
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- External PublicationAbstract
- ( Theme )
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- geophysics
- ( Theme )
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- seismics
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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- Published_Internal
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2000-01-01T00:00:00
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