A large impact crater beneath Hiawatha Glacier in northwest Greenland

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Dokumenter

Kurt H. Kjær, Nicolaj K. Larsen, Tobias Binder, Anders Anker Bjørk, Olaf Eisen, Mark Fahnestock, Svend Visby Funder, Adam A. Garde, Henning Haack, Veit Helm, Michael Houmark-Nielsen, Kristian Kjellerup Kjeldsen, Shfaqat Khan, Horst Machguth, Iain McDonald, Mathieu Morlighem, Jéremie Mouginot, John D. Paden, Tod Earle Waight, Christian Weikusat & 2 andre Eske Willerslev, Joseph MacGregor

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 impact-related 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.
OriginalsprogEngelsk
Artikelnummereaar8173
TidsskriftScience Advances
Vol/bind4
Udgave nummer11
Antal sider12
ISSN2375-2548
DOI
StatusUdgivet - 2018

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