TY - ABST

T1 - A large impact crater beneath the ice in northwest Greenland

AU - MacGregor, J. A.

AU - Kjær, K. H.

AU - Larsen, N. K.

AU - Binder, T.

AU - Bjork, A. A.

AU - Eisen, O.

AU - Fahnestock, M. A.

AU - Funder, S.

AU - Garde, A. A.

AU - Haack, H.

AU - Helm, V.

AU - Houmark-Nielsen, M.

AU - Kjeldsen, K. K.

AU - Khan, S. A.

AU - Machguth, H.

AU - McDonald, Iain

AU - Morlighem, Mathieu

AU - Mouginot, J.

AU - Paden, J. D.

AU - Waight, T. E.

AU - Weikusat, C.

AU - Willerslev, E.

PY - 2018

Y1 - 2018

N2 - A rarely considered element of Arctic system change in the Pleistocene is the possibility and consequences of any large high-latitude impact. We report the discovery of a large impact crater hidden 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.

AB - A rarely considered element of Arctic system change in the Pleistocene is the possibility and consequences of any large high-latitude impact. We report the discovery of a large impact crater hidden 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.

KW - 9315 Arctic region

KW - GEOGRAPHIC LOCATIONDE: 1621 Cryospheric change

KW - GLOBAL CHANGEDE: 1630 Impacts of global change

KW - GLOBAL CHANGEDE: 1637 Regional climate change

KW - GLOBAL CHANGE

M3 - Conference abstract for conference

ER -