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Leif Johansson

Leif Johansson

Professor emeritus

Leif Johansson

A Late Paleocene age for Greenland's Hiawatha impact structure

Author

  • 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

Summary, in English

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.

Department/s

  • Lithosphere and Biosphere Science

Publishing year

2022-03

Language

English

Publication/Series

Science Advances

Volume

8

Issue

10

Document type

Journal article

Publisher

American Association for the Advancement of Science (AAAS)

Topic

  • Geology

Status

Published

ISBN/ISSN/Other

  • ISSN: 2375-2548