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Sanna Alwmark

Sanna Alwmark

Postdoctoral fellow

Sanna Alwmark

Shocked quartz in sandstone from the buried Ilkurlka impact structure, Officer Basin, Western Australia

Author

  • Raiza R. Quintero
  • Aaron J. Cavosie
  • Sanna Alwmark
  • Peter W. Haines
  • Martin Danišík
  • Nicholas E. Timms
  • David Lim

Summary, in English

The Ilkurlka structure is an ~12 km diameter buried circular aeromagnetic anomaly within the Officer Basin in Western Australia. Prior studies postulated a range of origins, including meteorite impact. We report the presence of pervasive deformation in the first drill cores from the structure. Brecciated sandstone and siltstone contain arrays of quartz grains with concussion fractures and rare shocked quartz grains with planar deformation features (PDF). Universal stage measurements of two quartz grains reveal one grain with PDF parallel to (0001) orientation and three PDF sets parallel to (Formula presented.). A second grain contains three PDF sets parallel to (Formula presented.) and one set parallel to (Formula presented.). The shocked grains are interpreted to have formed in situ, rather than representing transported detrital shocked grains. These results suggest local shock compression of at least 10 GPa; however, preservation of primary porosity and overall paucity of shocked grains may indicate lower mean shock pressures. (U-Th)/He dating of 58 apatite grains from four samples across both cores shows a dominant age population at ~265 Ma and a minor age population at ~135 Ma. These dates overlap with regional events and thus do not provide an unambiguous impact age. An upper Carboniferous to lower Permian maximum impact age is provisionally proposed based on inferred missing target rock stratigraphy.

Department/s

  • Lithosphere and Biosphere Science

Publishing year

2023

Language

English

Pages

68-87

Publication/Series

Meteoritics and Planetary Science

Volume

59

Issue

1

Document type

Journal article

Publisher

Wiley-Blackwell

Topic

  • Geology

Status

Inpress

ISBN/ISSN/Other

  • ISSN: 1086-9379