TY - JOUR
T1 - A Miocene impact ejecta layer in the pelagic Pacific Ocean
AU - Nozaki, Tatsuo
AU - Ohta, Junichiro
AU - Noguchi, Takaaki
AU - Sato, Honami
AU - Ishikawa, Akira
AU - Takaya, Yutaro
AU - Kimura, Jun Ichi
AU - Chang, Qing
AU - Shimada, Kazuhiko
AU - Ishibashi, Jun ichiro
AU - Yasukawa, Kazutaka
AU - Kimoto, Katsunori
AU - Iijima, Koichi
AU - Kato, Yasuhiro
N1 - Funding Information:
We thank Yukari Otsuki and Hideo Yamamoto of JAMSTEC for supporting the Re-Os isotope and PGE analyses and Yayoi Itabashi of the University of Tokyo for assistance with the XRF and ICP-QMS analyses. Toru Matsumoto and Minako Takase of Kyushu University supported the focused ion beam cutting and ion milling of the spinel grains. Nobuhiro Hayami and Kazuhide Hirano of Carl Zeiss Co. arranged and performed micro-XCT analysis at Research Microscopy Solutions Tokyo, Carl Zeiss Co. We also thank Yuriko Nakamura of JAMSTEC for supporting the micro-XCT analysis at JAMSTEC. Some figures were improved by Koichiro Fujinaga of Chiba Institute of Technology. This work was supported by the Japan Society for Promotion of Science through KAKENHI grants-in-aid Nos JP16K13895 to T.Noz., JP14J10351 and JP16J07136 to J.O. and JP15H05771 to Y.K. Mass spectrometry at JAMSTEC was supported by KAKENHI grants-in-aid Nos JP15H02148, JP16H01123 and JP18H04372 to J.-I.K.
Publisher Copyright:
© 2019, The Author(s).
PY - 2019/12/1
Y1 - 2019/12/1
N2 - Meteorite impacts have caused catastrophic perturbations to the global environment and mass extinctions throughout the Earth’s history. Here, we present petrographic and geochemical evidence of a possible impact ejecta layer, dating from about 11 Ma, in deep-sea clayey sediment in the Northwest Pacific. This clay layer has high platinum group element (PGE) concentrations and features a conspicuous negative Os isotope anomaly (187Os/188Os as low as ~0.2), indicating an influx of extraterrestrial material. It also contains abundant spherules that include pseudomorphs suggestive of porphyritic olivine as well as spinel grains with euhedral, dendritic and spherical forms and NiO contents as great as 23.3 wt%, consistent with impact ejecta. Osmium isotope stratigraphy suggests a most plausible depositional age of ~11 Ma (Miocene) for this layer, as determined by fitting with the seawater evolution curve. No large impact crater of this age is known on land, even within the relatively large uncertainty range of the relative Os age. Thus, we suggest that an unrecognised impact event in the middle or late Miocene produced the impact ejecta layer of the Northwest Pacific.
AB - Meteorite impacts have caused catastrophic perturbations to the global environment and mass extinctions throughout the Earth’s history. Here, we present petrographic and geochemical evidence of a possible impact ejecta layer, dating from about 11 Ma, in deep-sea clayey sediment in the Northwest Pacific. This clay layer has high platinum group element (PGE) concentrations and features a conspicuous negative Os isotope anomaly (187Os/188Os as low as ~0.2), indicating an influx of extraterrestrial material. It also contains abundant spherules that include pseudomorphs suggestive of porphyritic olivine as well as spinel grains with euhedral, dendritic and spherical forms and NiO contents as great as 23.3 wt%, consistent with impact ejecta. Osmium isotope stratigraphy suggests a most plausible depositional age of ~11 Ma (Miocene) for this layer, as determined by fitting with the seawater evolution curve. No large impact crater of this age is known on land, even within the relatively large uncertainty range of the relative Os age. Thus, we suggest that an unrecognised impact event in the middle or late Miocene produced the impact ejecta layer of the Northwest Pacific.
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U2 - 10.1038/s41598-019-52709-1
DO - 10.1038/s41598-019-52709-1
M3 - Article
C2 - 31748510
AN - SCOPUS:85075378612
SN - 2045-2322
VL - 9
JO - Scientific Reports
JF - Scientific Reports
IS - 1
M1 - 16111
ER -