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

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 Hiawath...

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Bibliographic Details
Published in:Geology (Boulder) 2024-07, Vol.52 (7), p.517-521
Main Authors: Hyde, William R., Kenny, Gavin G., Jaret, Steven J., MacGregor, Joseph A., Beck, Pierre, Whitehouse, Martin J., Larsen, Nicolaj K.
Format: Article
Language:English
Subjects:
Den föränderliga jorden
Geochronometry
Glaciation
Glaciers
Grains
Greenland ice sheet
Hypervelocity impact
Ice sheets
Impact melts
Mass spectrometry
Mass spectroscopy
Precambrian
Radiometric dating
Rock
Rocks
Secondary ion mass spectrometry
Sediment samples
The changing Earth
Zircon
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Summary: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.
ISSN:0091-7613
1943-2682
1943-2682
DOI:10.1130/G51876.1