A Late Paleocene age for Greenland's Hiawatha impact structure

Gavin G Kenny; William R Hyde; Michael Storey; Adam A Garde; Martin J Whitehouse; Pierre Beck; Leif Johansson; Anne Sofie Søndergaard; Anders A Bjørk; Joseph A MacGregor; Shfaqat A Khan; Jérémie Mouginot; Brandon C Johnson; Elizabeth A Silber; Daniel K P Wielandt; Kurt H Kjær; Nicolaj K Larsen

doi:10.1126/sciadv.abm2434

A Late Paleocene age for Greenland's Hiawatha impact structure

Sci Adv. 2022 Mar 11;8(10):eabm2434. doi: 10.1126/sciadv.abm2434. Epub 2022 Mar 9.

Authors

Gavin G Kenny¹, William R Hyde², Michael Storey³, Adam A Garde⁴, Martin J Whitehouse¹, Pierre Beck⁵, Leif Johansson⁶, Anne Sofie Søndergaard^{7

8}, Anders A Bjørk⁹, Joseph A MacGregor¹⁰, Shfaqat A Khan¹¹, Jérémie Mouginot^{12

13}, Brandon C Johnson^{14

15}, Elizabeth A Silber^{16

17}, Daniel K P Wielandt³, Kurt H Kjær², Nicolaj K Larsen²

Affiliations

¹ Department of Geosciences, Swedish Museum of Natural History, SE-104 05 Stockholm, Sweden.
² Globe Institute, University of Copenhagen, Øster Voldgade 5-7, 1350 Copenhagen K, Denmark.
³ Quadlab, Natural History Museum of Denmark, Øster Voldgade 5-7, 1350 Copenhagen K, Denmark.
⁴ Geological Survey of Denmark and Greenland, Øster Voldgade 10, 1350 Copenhagen K, Denmark.
⁵ Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France.
⁶ Department of Geology, Lund University, Sölvegatan 12, 223 62 Lund, Sweden.
⁷ Department of Geoscience, Aarhus University, Høegh Guldbergs Gade 2, 8000 Aarhus, Denmark.
⁸ Laboratory for Ion Beam Physics, ETH Zürich, Otto-Stern-Weg 5, 8093 Zürich, Switzerland.
⁹ Department of Geoscience and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, 1350 Copenhagen K, Denmark.
¹⁰ Cryospheric Sciences Lab, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA.
¹¹ Department of Geodesy, National Space Institute, Technical University.
¹² of Denmark, Kongens Lyngby, Denmark.
¹³ Institut des Géosciences de l'Environnement, CNRS, Université Grenoble Alpes, Grenoble, France.
¹⁴ Department of Earth System Science, University of California, Irvine, Irvine, CA 92617, USA.
¹⁵ Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN 47907, USA.
¹⁶ Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907, USA.
¹⁷ Department of Earth Sciences, Western University, London, ON N6A 5B7, Canada.

Abstract

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 ⁴⁰Ar/³⁹Ar 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 ⁴⁰Ar/³⁹Ar 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.