A Paleozoic age for the Tunnunik impact structure

1Camille Lepaulard,1Jérôme Gattacceca,2Nicholas Swanson‐Hysell, 1Yoann Quesnel, 1François Demory, 3,4Gordon R. Osinski
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13239]
1Aix Marseille Univ, CNRS, IRD, Coll France, INRA, CEREGE, , Aix‐en‐Provence, France
2Department of Earth and Planetary Science, University of California, , Berkeley, California, 94720–4767 USA
3Department of Earth Sciences, Centre for Planetary Science and Exploration, University of Western Ontario, , London, Ontario, N6A 5B7 Canada
4Department of Physics & Astronomy, University of Western Ontario, , London, Ontario, N6A 5B7 Canada
Published by arrangement with John Wiley & Sons

We report paleomagnetic directions from the target rocks of the Tunnunik impact structure, as well as from lithic impact breccia dikes that formed during the impact event. The target sedimentary rocks have been remagnetized after impact‐related tilting during a reverse polarity interval. Their magnetization is unblocked up to 350 °C. The diabase dikes intruding into these sediments retained their original magnetization which unblocks above 400 °C. The impact breccia records a paleomagnetic direction similar to that of the overprints in the target sedimentary rocks. The comparison of the resulting virtual geomagnetic pole for the Tunnunik impact structure with the apparent polar wander path for Laurentia combined with biostratigraphic constraints from the target sedimentary rocks is most consistent with an impact age in the Late Ordovician or Silurian, around 430–450 Ma, soon after the deposition of the youngest impacted sedimentary rocks. Our results from the overprinted sedimentary rocks and diabase dikes imply that the postimpact temperature of the studied rocks was about 350 °C.

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