The East and West Cleawater Lake impact structures (Wiyâshâkimî Lake, Québec), ∼26 and 32 km in diameter, respectively, have been proposed to represent an impact doublet. We investigated their paleomagnetism to contribute to this debate. The paleomagnetic directions of the impact melt rocks and impact melt-bearing breccias from the West Clearwater structure are compatible with the radiometric age of 280–290 Ma previously determined for this structure and indicate that the impact occurred during a reverse polarity interval of the geomagnetic field. A similar remagnetization direction is found in the basement within 10 km of the structure center, whereas basement farther away from the center has escaped remagnetization by the impact. Samples for the East Clearwater structure come from two holes drilled in 1963 and 1964. Unfortunately, the drill hole through the melt rocks is tilted by 30° from the vertical with an unknown azimuth. The paleomagnetic inclination of these melt rocks cannot be constrained to better than between −28° and +32°. This is, however, distinct from the inclination of the melt rocks of the West Clearwater Lake impact structure (−27.8° ± 3.7°), suggesting that the two structures do not represent an impact doublet, in agreement with recent radiometric dating. The basement rocks and the melt rocks within 10 km of the center of the West Clearwater Lake impact structure show a magnetic signature of titanohematite that crystallized during postimpact hydrothermal activity under oxidizing conditions. This is not observed in the basement or the melt rocks from the East Clearwater Lake impact structure.
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Research Article|
August 14, 2019
Paleomagnetism and rock magnetism of East and West Clearwater Lake impact structures1
Jérôme Gattacceca;
a
Aix Marseille Univ, CNRS, IRD, Coll France, INRA, CEREGE, Aix en Provence, France.Corresponding author: Jérôme Gattacceca (email: gattacceca@cerege.fr).
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William Zylberman;
William Zylberman
a
Aix Marseille Univ, CNRS, IRD, Coll France, INRA, CEREGE, Aix en Provence, France.b
Department of Earth Sciences, University of Western Ontario, London, ON N6A 5B7, Canada.c
Centre for Planetary Science and Exploration, University of Western Ontario, London, ON N6A 5B7, Canada.
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Adam B. Coulter;
Adam B. Coulter
b
Department of Earth Sciences, University of Western Ontario, London, ON N6A 5B7, Canada.c
Centre for Planetary Science and Exploration, University of Western Ontario, London, ON N6A 5B7, Canada.
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François Demory;
François Demory
a
Aix Marseille Univ, CNRS, IRD, Coll France, INRA, CEREGE, Aix en Provence, France.
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Yoann Quesnel;
Yoann Quesnel
a
Aix Marseille Univ, CNRS, IRD, Coll France, INRA, CEREGE, Aix en Provence, France.
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Pierre Rochette;
Pierre Rochette
a
Aix Marseille Univ, CNRS, IRD, Coll France, INRA, CEREGE, Aix en Provence, France.
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Gordon R. Osinski;
Gordon R. Osinski
b
Department of Earth Sciences, University of Western Ontario, London, ON N6A 5B7, Canada.c
Centre for Planetary Science and Exploration, University of Western Ontario, London, ON N6A 5B7, Canada.
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Brenuchon Edwige
Brenuchon Edwige
a
Aix Marseille Univ, CNRS, IRD, Coll France, INRA, CEREGE, Aix en Provence, France.
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Canadian Journal of Earth Sciences (2019) 56 (9): 983–993.
Article history
received:
20 Nov 2018
accepted:
20 Feb 2019
first online:
01 Oct 2019
Citation
Jérôme Gattacceca, William Zylberman, Adam B. Coulter, François Demory, Yoann Quesnel, Pierre Rochette, Gordon R. Osinski, Brenuchon Edwige; Paleomagnetism and rock magnetism of East and West Clearwater Lake impact structures. Canadian Journal of Earth Sciences 2019;; 56 (9): 983–993. doi: https://doi.org/10.1139/cjes-2018-0291
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