Evidence for ca. 1 Ga hypervelocity impact event found in northwest Greenland

Author:

Hyde William R.1ORCID,Kenny Gavin G.2,Jaret Steven J.3,MacGregor Joseph A.4,Beck Pierre5,Whitehouse Martin J.2,Larsen Nicolaj K.1

Affiliation:

1. 1Globe Institute, University of Copenhagen, 1350 Copenhagen, Denmark

2. 2Department of Geosciences, Swedish Museum of Natural History, 114 18 Stockholm, Sweden

3. 3Department of Physical Sciences, Kingsborough Community College, City University of New York, Brooklyn, New York 11235, USA

4. 4Cryospheric Sciences Laboratory, National Aeronautics and Space Administration (NASA) Goddard Space Flight Center, Greenbelt, Maryland 20771, USA

5. 5Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), CNRS, Université Grenoble Alpes, 38058 Grenoble Cédex 9, France

Abstract

Abstract There are likely many undiscovered impact structures on Earth, but several challenges prevent their detection, including possible concealment beneath large ice sheets. In recent years, geophysical, geochemical, and microphysical evidence has mounted for a ca. 58 Ma impact structure under the Hiawatha Glacier, northwest Greenland. Here, we report evidence for a second, much older hypervelocity impact event in this region, recorded in an impact melt rock sample collected from a glaciofluvial deposit in Inglefield Land. Secondary ion mass spectrometry U-Pb analyses of shock metamorphosed zircon grains yielded a previously unrecorded, Proterozoic best estimate impact age of 1039 ± 16 Ma (mean square of weighted deviates = 2.9). Based on Archean–Proterozoic target rock U-Pb ages obtained from unshocked zircon grains and the location of the melt rock sample along the ice margin, we suggest this sample was derived from a hypervelocity impact structure farther inland, concealed by the Greenland Ice Sheet. This study demonstrates the ability to uncover new impact events in some of the most inaccessible areas on Earth and the possibility of sampling multiple impact structures from one location when examining ex situ material. Our results have implications for current and future Martian and lunar returned samples that demonstrably bear complex impact histories.

Publisher

Geological Society of America

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