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Gravity evidence for abrupt changes in mean crustal density at the junction of Australian crustal blocks

Created 17/10/2025

Updated 17/10/2025

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The major gravity anomalies in central and western Australia occur as elongate dipoles, either in isolation or in a series. Each dipole is thought to be caused by an abrupt change in mean crustal density at the junction of two crustal blocks and by the associated isostatically compensating masses. Typically one block has along its margin a strip with anomalously high mean crustal density, and the other block has normal density crust covered by several kilometres of low density sediment. The observed anomalies are consistent with the anomalous masses being isostatically compensated by variations in the thickness of the crust, the crustal thickness variations being gradual and extending to about 100 km from the boundaries of the anomalous bodies. The crustal block boundaries inferred from dipole anomalies correspond in position with the crustal block boundaries inferred from geology, and approximately with the position of block boundaries inferred from changes in the gravity trend pattern. Usually the block with younger basement has high density material along its margin, and the other, older block is covered with sediment; both these features are likely to be caused by the process that created or emplaced the younger block. The presence of relatively dense material high in the crust along the margins of the younger blocks suggests that younger blocks are not superficial features on a uniform old crust. The dipole anomalies on the Australian Precambrian crust are similar in magnitude and tectonic position to those recognised at Precambrian province boundaries in Canada.

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Field Value
Title Gravity evidence for abrupt changes in mean crustal density at the junction of Australian crustal blocks
Language eng
Licence Not Specified
Landing Page https://data.gov.au/data/dataset/541d8a0a-c218-46cd-974c-9b27cd30daba
Contact Point
Geoscience Australia Data
clientservices@ga.gov.au
Reference Period 20/04/2018
Geospatial Coverage
Map data © OpenStreetMap contributors
{
  "coordinates": [
    [
      [
        110.0,
        -40.0
      ],
      [
        140.0,
        -40.0
      ],
      [
        140.0,
        -10.0
      ],
      [
        110.0,
        -10.0
      ],
      [
        110.0,
        -40.0
      ]
    ]
  ],
  "type": "Polygon"
}
Data Portal Geoscience Australia

Data Source

This dataset was originally found on Geoscience Australia "Gravity evidence for abrupt changes in mean crustal density at the junction of Australian crustal blocks". Please visit the source to access the original metadata of the dataset:
https://ecat.ga.gov.au/geonetwork/srv/eng/csw/dataset/gravity-evidence-for-abrupt-changes-in-mean-crustal-density-at-the-junction-of-australian-crust