TY - JOUR

T1 - Evidence for ca. 1 Ga hypervelocity impact event found in northwest Greenland

AU - Hyde, William R.

AU - Kenny, Gavin G.

AU - Jaret, Steven J.

AU - Macgregor, Joseph A.

AU - Beck, Pierre

AU - Whitehouse, Martin J.

AU - Larsen, Nicolaj K.

PY - 2024

Y1 - 2024

N2 - There are likely many undiscovered impact structures on Earth, but several challengesprevent their detection, including possible concealment beneath large ice sheets. In recentyears, geophysical, geochemical, and microphysical evidence has mounted for a ca. 58 Maimpact structure under the Hiawatha Glacier, northwest Greenland. Here, we report evidence for a second, much older hypervelocity impact event in this region, recorded in animpact melt rock sample collected from a glaciofluvial deposit in Inglefield Land. Secondary ion mass spectrometry U-Pb analyses of shock metamorphosed zircon grains yielded apreviously unrecorded, Proterozoic best estimate impact age of 1039 ± 16 Ma (mean squareof weighted deviates = 2.9). Based on Archean–Proterozoic target rock U-Pb ages obtainedfrom 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 newimpact events in some of the most inaccessible areas on Earth and the possibility of samplingmultiple impact structures from one location when examining ex situ material. Our resultshave implications for current and future Martian and lunar returned samples that demonstrably bear complex impact histories.

AB - There are likely many undiscovered impact structures on Earth, but several challengesprevent their detection, including possible concealment beneath large ice sheets. In recentyears, geophysical, geochemical, and microphysical evidence has mounted for a ca. 58 Maimpact structure under the Hiawatha Glacier, northwest Greenland. Here, we report evidence for a second, much older hypervelocity impact event in this region, recorded in animpact melt rock sample collected from a glaciofluvial deposit in Inglefield Land. Secondary ion mass spectrometry U-Pb analyses of shock metamorphosed zircon grains yielded apreviously unrecorded, Proterozoic best estimate impact age of 1039 ± 16 Ma (mean squareof weighted deviates = 2.9). Based on Archean–Proterozoic target rock U-Pb ages obtainedfrom 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 newimpact events in some of the most inaccessible areas on Earth and the possibility of samplingmultiple impact structures from one location when examining ex situ material. Our resultshave implications for current and future Martian and lunar returned samples that demonstrably bear complex impact histories.

U2 - 10.1130/G51876.1

DO - 10.1130/G51876.1

M3 - Journal article

JO - Geology

JF - Geology

SN - 0091-7613

ER -