Pleistocene organic matter modified by the Hiawatha impact, northwest Greenland
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Pleistocene organic matter modified by the Hiawatha impact, northwest Greenland. / Garde, Adam A.; Søndergaard, Anne Sofie; Guvad, Carsten; Dahl-Møller, Jette; Nehrke, Gernot; Sanei, Hamed; Weikusat, Christian; Funder, Svend; Kjær, Kurt H.; Larsen, Nicolaj Krog.
In: Geology, Vol. 48, No. 9, 2020, p. 867-871.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - Pleistocene organic matter modified by the Hiawatha impact, northwest Greenland
AU - Garde, Adam A.
AU - Søndergaard, Anne Sofie
AU - Guvad, Carsten
AU - Dahl-Møller, Jette
AU - Nehrke, Gernot
AU - Sanei, Hamed
AU - Weikusat, Christian
AU - Funder, Svend
AU - Kjær, Kurt H.
AU - Larsen, Nicolaj Krog
PY - 2020
Y1 - 2020
N2 - The 31-km-wide Hiawatha impact crater was recently discovered under the ice sheet in northwest Greenland, but its age remains uncertain. Here we investigate solid organic matter found at the tip of the Hiawatha Glacier to determine its thermal degradation, provenance, and age, and hence a maximum age of the impact. Impactite grains of microbrecchia and shock-melted glass in glaciofluvial sand contain abundant dispersed carbon, and gravel-sized charcoal particles are common on the outwash plain in front of the crater. The organic matter is depleted in the thermally sensitive, labile bio-macromolecule protohydrocarbons. Pebble-sized lumps of lignite collected close to the sand sample consist largely of fragments of conifers such as Pinus or Picea, with greatly expanded cork cells and desiccation cracks which suggest rapid, heat-induced expansion and contraction. Pinus and Picea are today extinct from North Greenland but are known from late Pliocene deposits in the Canadian Arctic Archipelago and early Pleistocene deposits at Kap Kobenhavn in eastern North Greenland. The thermally degraded organic material yields a maximum age for the impact, providing the first firm evidence that the Hiawatha crater is the youngest known large impact structure on Earth.
AB - The 31-km-wide Hiawatha impact crater was recently discovered under the ice sheet in northwest Greenland, but its age remains uncertain. Here we investigate solid organic matter found at the tip of the Hiawatha Glacier to determine its thermal degradation, provenance, and age, and hence a maximum age of the impact. Impactite grains of microbrecchia and shock-melted glass in glaciofluvial sand contain abundant dispersed carbon, and gravel-sized charcoal particles are common on the outwash plain in front of the crater. The organic matter is depleted in the thermally sensitive, labile bio-macromolecule protohydrocarbons. Pebble-sized lumps of lignite collected close to the sand sample consist largely of fragments of conifers such as Pinus or Picea, with greatly expanded cork cells and desiccation cracks which suggest rapid, heat-induced expansion and contraction. Pinus and Picea are today extinct from North Greenland but are known from late Pliocene deposits in the Canadian Arctic Archipelago and early Pleistocene deposits at Kap Kobenhavn in eastern North Greenland. The thermally degraded organic material yields a maximum age for the impact, providing the first firm evidence that the Hiawatha crater is the youngest known large impact structure on Earth.
U2 - 10.1130/G47432.1
DO - 10.1130/G47432.1
M3 - Journal article
AN - SCOPUS:85090563679
VL - 48
SP - 867
EP - 871
JO - Geology
JF - Geology
SN - 0091-7613
IS - 9
ER -
ID: 248774543