The Late Ordovician (Sandbian) Glasford structure: A marine‐target impact crater with a possible connection to the Ordovician meteorite event

1,2Charles C. Monson,3Dustin Sweet,3Branimir Segvic,3Giovanni Zanoni,2Kyle Balling,2,4Jacalyn M. Wittmer,5G. Robert Ganis,6Guo Cheng
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13401]
1Illinois State Geological Survey, University of lllinois at Urbana-Champaign, 615 East Peabody Drive, Champaign, Illinois
61820, USA
2Department or Geology, University of Illinois at Urbana-Champaign, 1301 West Green Street, Urbana, lllinois 61801, USA
3Department of Geosciences, Texas Tech University, 1200 Memorial Circle, Lubbock, Texas 79409, USA
4Department of Geological Sciences, State University of New York at Geneseo, 1 College Circle, Geneseo, New York
14454, USA
5Consulting Geologist, 749 Burlwood Drive, Southcrn Pincs. North Carolina 28387, USA
6Department of Earth and Environmental Sciences, 115 Trowbridge Hall, Jowa City, Iowa 52242, USA
Published by arrangement with John Wiley & Sons

The Glasford structure in Illinois (USA) was recognized as a buried impact craterin the early 1960s but has never been reassessed in light of recent advances in planetaryscience. Here, we document shatter cones and previously unknown quartz microdeformationfeatures that support an impact origin for the Glasford structure. We identify the 4 kmwide structure as a complex buried impact crater and describe syn- and postimpact depositsfrom its annular trough. We have informally designated these deposits as the KingstonMines unit (KM). The fossils and sedimentology of the KM indicate a marine depositionalsetting. The various intervals within the KM constitute a succession of breccia, carbonate,sandstone, and shale similar to marine sedimentary successions preserved in other craters.Graptolite specimens retrieved from the KM place the time of deposition at approximately4552 Ma (Late Ordovician, Sandbian). This age determination suggests a possible linkbetween the Glasford impact and the Ordovician meteorite shower, an increase in the rateof terrestrial meteorite impacts attributed to the breakup of the L-chondrite parent body inthe main asteroid belt.

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