A large impact crater beneath Hiawatha Glacier in northwest Greenland

Kurt Kjær , Nicolaj Larsen , Tobias Binder , Anders Björk , Olaf Eisen (1) , Mark Fahnestock , Svend Funder , Adam Garde , Henning Haack (2) , Veit Helm , Michael Houmark-Nielsen , Kristian Kjeldsen , Shfaqat Khan , Horst Machguth , Iain Mcdonald (3) , Mathieu Morlighem , Jérémie Mouginot (4, 5) , John Paden (6) , Tod Waight , Christian Weikusat , Eske Willerslev (7) , Joseph J Macgregor (8)

1 Abteilung Klinische Sozialmedizin, Berufs- und Umweltdermatologie
2 STARPLAN - Centre for Star and Planet Formation
3 JBCA - Jodrell Bank Centre for Astrophysics
4 IGE - Institut des Géosciences de l’Environnement
5 UC Irvine - University of California [Irvine]
6 CReSIS - Center for Remote Sensing of Ice Sheets
7 Section for GeoGenetics
8 Institute for Geophysics

We report the discovery of a large impact crater beneath Hiawatha Glacier in northwest Greenland. From airborne radar surveys, we identify a 31-kilometer-wide, circular bedrock depression beneath up to a kilometer of ice. This depression has an elevated rim that cross-cuts tributary subglacial channels and a subdued central uplift that appears to be actively eroding. From ground investigations of the deglaciated foreland, we identify overprinted structures within Precambrian bedrock along the ice margin that strike tangent to the subglacial rim. Glaciofluvial sediment from the largest river draining the crater contains shocked quartz and other impactrelated grains. Geochemical analysis of this sediment indicates that the impactor was a fractionated iron asteroid, which must have been more than a kilometer wide to produce the identified crater. Radiostratigraphy of the ice in the crater shows that the Holocene ice is continuous and conformable, but all deeper and older ice appears to be debris rich or heavily disturbed. The age of this impact crater is presently unknown, but from our geological and geophysical evidence, we conclude that it is unlikely to predate the Pleistocene inception of the Greenland Ice Sheet.

Domaines: Sciences de l'environnement; Milieux et Changements globaux

Kurt Kjær, Nicolaj Larsen, Tobias Binder, Anders Björk, Olaf Eisen, et al.. A large impact crater beneath Hiawatha Glacier in northwest Greenland. Science Advances , 2018, 4 (11), pp.eaar8173. ⟨10.1126/sciadv.aar8173⟩. ⟨hal-02392102⟩