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What caused terrestrial dust loading and climate downturns between A.D. 533 and 540?

By
Dallas H. Abbott
Dallas H. Abbott
Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York 10964, USA
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Dee Breger
Dee Breger
Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York 10964, USA
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Pierre E. Biscaye
Pierre E. Biscaye
Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York 10964, USA
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John A. Barron
John A. Barron
U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025, USA
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Robert A. Juhl
Robert A. Juhl
Independent researcher, 1-4-1 Rokko Heights 906, Shinkawa, Chuo-ku, Tokyo 104-0033, Japan
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Patrick McCafferty
Patrick McCafferty
Independent researcher, 7 Windsor Avenue North, Belfast BT9 6EL, Northern Ireland
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Published:
September 01, 2014

Sn-rich particles, Ni-rich particles, and cosmic spherules are found together at four discrete stratigraphic levels within the 362–360 m depth interval of the Greenland Ice Sheet Project 2 (GISP2) ice core (72.6°N, 38.5°W, elevation: 3203 m). Using a previously derived calendar-year time scale, these particles span a time of increased dust loading of Earth's atmosphere between A.D. 533 and 540. The Sn-rich and Ni-rich particles contain an average of 10–11 wt% C. Their high C contents coupled with local enrichments in the volatile elements I, Zn, Cu, and Xe suggest a cometary source for the dust. The late spring timing of extraterrestrial input best matches the Eta Aquarid meteor shower associated with comet 1P/Halley. An increased flux of cometary dust might explain a modest climate downturn in A.D. 533. Both cometary dust and volcanic sulfate probably contributed to the profound global dimming during A.D. 536 and 537 but may be insufficient sources of fine aerosols. We found tropical marine microfossils and aerosol-sized CaCO3 particles at the end A.D. 535–start A.D. 536 level that we attribute to a low-latitude explosion in the ocean. This additional source of dust is probably needed to explain the solar dimming during A.D. 536 and 537. Although there has been no extinction documented at A.D. 536, our results are relevant because mass extinctions may also have multiple drivers. Detailed examinations of fine particles at and near extinction horizons can help to determine the relative contributions of cosmic and volcanic drivers to mass extinctions.

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GSA Special Papers

Volcanism, Impacts, and Mass Extinctions: Causes and Effects

Gerta Keller
Gerta Keller
Department of Geosciences, Princeton University, Princeton, New Jersey 08544, USA
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Andrew C. Kerr
Andrew C. Kerr
School of Earth and Ocean Sciences, Cardiff University, Park Place, Cardiff CF10 3AT, Wales, UK
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Geological Society of America
Volume
505
ISBN print:
9780813725055
Publication date:
September 01, 2014

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