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A sandstone breccia, formed by quasi-liquid deformation, from the Amadeus Basin, Northern Territory

Created 16/10/2025

Updated 16/10/2025

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A prominent sandstone breccia crops out in the Pacoota Sandstone, Western MacDonnell Ranges, Northern Territory. The breccia occurs as discontinuous lenses which grade laterally, through incipient breccia and disrupted sandstone beds, into the enclosing sandstone sequence. This sequence consists of interbedded well-sorted silicia-cemented and poorly sorted friable quartzose sandstones; these two sandstone types also constitute, respectively, the clasts and matrix of the breccia. The clasts are rectangular (joint-bounded) and broken rectangular in shape, ranging up to 1 m in length. The matrix is predominantly massive, but convolute bedding is locally present. Similar sandstone breccias are known from three other localities in the region, all at the same stratigraphic level within the Pacoota Sandstone. Petrographic data indicate that the clast sandstone was cemented and strained prior to brecciation, whilst the matrix sandstone retained a largely cohesionless state and failed in a quasi-liquid manner. It is concluded that the brecciation occurred in situ at a considerable depth in a sedimentary pile, and resulted from the rotation and fragmentation of joint blocks of silica-cemented sandstone in the interbedded mobile matrix sandstone. Pore-water pressures are thought to have played an important role in the mobilization of the matrix sandstone.

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Field Value
Title A sandstone breccia, formed by quasi-liquid deformation, from the Amadeus Basin, Northern Territory
Language eng
Licence Not Specified
Landing Page https://data.gov.au/data/en/dataset/89679be8-3c68-4031-a79b-2996502f4451
Contact Point
Geoscience Australia Data
clientservices@ga.gov.au
Reference Period 20/04/2018
Geospatial Coverage
Map data © OpenStreetMap contributors
{
  "coordinates": [
    [
      [
        132.0,
        -24.5
      ],
      [
        133.2,
        -24.5
      ],
      [
        133.2,
        -23.5
      ],
      [
        132.0,
        -23.5
      ],
      [
        132.0,
        -24.5
      ]
    ]
  ],
  "type": "Polygon"
}
Data Portal Geoscience Australia

Data Source

This dataset was originally found on Geoscience Australia "A sandstone breccia, formed by quasi-liquid deformation, from the Amadeus Basin, Northern Territory". Please visit the source to access the original metadata of the dataset:
https://ecat.ga.gov.au/geonetwork/srv/eng/csw/dataset/a-sandstone-breccia-formed-by-quasi-liquid-deformation-from-the-amadeus-basin-northern-territor