Research Article| April 01, 2015 Nanoscale records of ancient shock deformation: Reidite (ZrSiO4) in sandstone at the Ordovician Rock Elm impact crater Aaron J. Cavosie; Aaron J. Cavosie 1Department of Applied Geology, Curtin University, Perth, WA 6102, Australia2Department of Geoscience, University of Wisconsin–Madison, Madison, Wisconsin 53706, USA3Department of Geology, University of Puerto Rico–Mayagüez, Mayagüez, Puerto Rico 00681, USA Search for other works by this author on: GSW Google Scholar Timmons M. Erickson; Timmons M. Erickson 1Department of Applied Geology, Curtin University, Perth, WA 6102, Australia Search for other works by this author on: GSW Google Scholar Nicholas E. Timms Nicholas E. Timms 1Department of Applied Geology, Curtin University, Perth, WA 6102, Australia Search for other works by this author on: GSW Google Scholar Author and Article Information Aaron J. Cavosie 1Department of Applied Geology, Curtin University, Perth, WA 6102, Australia2Department of Geoscience, University of Wisconsin–Madison, Madison, Wisconsin 53706, USA3Department of Geology, University of Puerto Rico–Mayagüez, Mayagüez, Puerto Rico 00681, USA Timmons M. Erickson 1Department of Applied Geology, Curtin University, Perth, WA 6102, Australia Nicholas E. Timms 1Department of Applied Geology, Curtin University, Perth, WA 6102, Australia Publisher: Geological Society of America Received: 28 Nov 2014 Revision Received: 22 Jan 2015 Accepted: 27 Jan 2015 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2015 Geological Society of America Geology (2015) 43 (4): 315–318. https://doi.org/10.1130/G36489.1 Article history Received: 28 Nov 2014 Revision Received: 22 Jan 2015 Accepted: 27 Jan 2015 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Aaron J. Cavosie, Timmons M. Erickson, Nicholas E. Timms; Nanoscale records of ancient shock deformation: Reidite (ZrSiO4) in sandstone at the Ordovician Rock Elm impact crater. Geology 2015;; 43 (4): 315–318. doi: https://doi.org/10.1130/G36489.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The terrestrial record of meteorite impacts is difficult to decipher because unequivocal evidence of impact is increasingly destroyed with time by erosion, burial, and tectonics. Zircon survives these processes as a shocked mineral, and above 20 GPa transforms to reidite, a high-pressure ZrSiO4 polymorph diagnostic of impact. However, the utility of reidite has been limited by its occurrence; it has only been reported from three relatively young (<36 Ma) impact craters globally. Here we report a new occurrence of reidite in brecciated sandstone from the Ordovician Rock Elm impact crater in Wisconsin, United States. Electron backscatter diffraction mapping was used to identify reidite and microtwins within shocked zircons smaller than 50 µm in diameter. Reidite occurs both as 200–500-nm-wide lamellar intergrowths and as nanoparticulate grains, and not only provides the first diagnostic evidence for ultrahigh-pressure shock metamorphism at Rock Elm, but is also the oldest reported occurrence of reidite. Considering its small size, and the ubiquitous presence of detrital zircon in siliciclastic rocks, reidite may be more common in the rock record than has been reported but has potentially gone undetected. The recognition that nanoscale reidite can be preserved over deep time within zircon in shock-metamorphosed sandstone presents new opportunities for investigating Earth’s impact record, as it could potentially preserve nanoscopic evidence of impact events much older than the one that formed Rock Elm. Given that shocked zircons have been shown to survive sedimentary cycling, the identification of reidite within zircons in siliciclastic rocks could facilitate investigating the impact chronology over much of the geological time scale, as the oldest terrestrial minerals known are detrital zircons. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.