A Late Paleocene age for Greenland’s Hiawatha impact structure

The ~31-km-wide Hiawatha structure, located beneath Hiawatha Glacier in northwestern Greenland, has been proposed as an impact structure that may have formed after the Pleistocene inception of the Greenland Ice Sheet. To date the structure, we conducted 40 Ar/ 39 Ar analyses on glaciofluvial sand an...

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Bibliographic Details
Published in:Science Advances
Main Authors: Kenny, Gavin G., Hyde, William R., Storey, Michael, Garde, Adam A., Whitehouse, Martin J., Beck, Pierre, Johansson, Leif, Søndergaard, Anne Sofie, Bjørk, Anders A., MacGregor, Joseph A., Khan, Shfaqat A., Mouginot, Jérémie, Johnson, Brandon C., Silber, Elizabeth A., Wielandt, Daniel K. P., Kjær, Kurt H., Larsen, Nicolaj K.
Format: Article in Journal/Newspaper
Language:English
Published: American Association for the Advancement of Science (AAAS) 2022
Subjects:
East Greenland
glacier
Greenland
Ice Sheet
Online Access:http://dx.doi.org/10.1126/sciadv.abm2434
https://www.science.org/doi/pdf/10.1126/sciadv.abm2434
Description
Summary:The ~31-km-wide Hiawatha structure, located beneath Hiawatha Glacier in northwestern Greenland, has been proposed as an impact structure that may have formed after the Pleistocene inception of the Greenland Ice Sheet. To date the structure, we conducted 40 Ar/ 39 Ar analyses on glaciofluvial sand and U-Pb analyses on zircon separated from glaciofluvial pebbles of impact melt rock, all sampled immediately downstream of Hiawatha Glacier. Unshocked zircon in the impact melt rocks dates to ~1915 million years (Ma), consistent with felsic intrusions found in local bedrock. The 40 Ar/ 39 Ar data indicate Late Paleocene resetting and shocked zircon dates to 57.99 ± 0.54 Ma, which we interpret as the impact age. Consequently, the Hiawatha impact structure far predates Pleistocene glaciation and is unrelated to either the Paleocene-Eocene Thermal Maximum or flood basalt volcanism in east Greenland. However, it was contemporaneous with the Paleocene Carbon Isotope Maximum, although the impact’s exact paleoenvironmental and climatic significance awaits further investigation.

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