^1,2Raiza R. Quintero,²Aaron J. Cavosie,^3,4Sanna Alwmark,⁵Peter W. Haines,⁶Martin Danišík,²Nicholas E. Timms,⁷David Lim
Meteoritics & Planetary Science (in Press) Link to Artticle [https://doi.org/10.1111/maps.14108]
¹Department of Geology, University of Puerto Rico at Mayagüez, Mayagüez, Puerto Rico
²Space Science and Technology Centre, School of Earth and Planetary Science, Curtin University, Perth,
Western Australia, Australia
³Department of Geology, Lund University, Lund, Sweden
⁴Niels Bohr Institute, University of Copenhagen, Copenhagen N, Denmark
⁵Geological Survey of Western Australia, East Perth, Western Australia, Australia
⁶John de Laeter Centre, Curtin University, Perth, Western Australia, Australia
⁷Maria Resources Pty. Ltd., Subiaco, Western Australia, Australia
Published by arrangement with John Wiley & Sons

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 {10⁢1¯⁢3}. A second grain contains three PDF sets parallel to {10⁢1¯⁢3} and one set parallel to {10⁢1¯⁢4}. 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.