Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling

R. B. Firestone, A. West, J. P. Kennett, L. Becker, T. E. Bunch, Z. S. Revay, P. H. Schultz, T. Belgya, D. J. Kennett, J. M. Erlandson, O. J. Dickenson, A. C. Goodyear, R. S. Harris, G. A. Howard, J. B. Kloosterman, P. Lechler, P. A. Mayewski, J. Montgomery, R. Poreda, T. Darrah, S. S. Que Hee, A. R. Smith, A. Stich, W. Topping, J. H. Wittke, and W. S. Wolbach
PNAS October 9, 2007 104 (41) 16016-16021; https://doi.org/10.1073/pnas.0706977104

  1. Communicated by Steven M. Stanley, University of Hawaii at Manoa, Honolulu, HI, July 26, 2007 (received for review March 13, 2007)

Abstract

A carbon-rich black layer, dating to ≈12.9 ka, has been previously identified at ≈50 Clovis-age sites across North America and appears contemporaneous with the abrupt onset of Younger Dryas (YD) cooling. The in situ bones of extinct Pleistocene megafauna, along with Clovis tool assemblages, occur below this black layer but not within or above it. Causes for the extinctions, YD cooling, and termination of Clovis culture have long been controversial. In this paper, we provide evidence for an extraterrestrial (ET) impact event at ≅12.9 ka, which we hypothesize caused abrupt environmental changes that contributed to YD cooling, major ecological reorganization, broad-scale extinctions, and rapid human behavioral shifts at the end of the Clovis Period. Clovis-age sites in North American are overlain by a thin, discrete layer with varying peak abundances of (i) magnetic grains with iridium, (ii) magnetic microspherules, (iii) charcoal, (iv) soot, (v) carbon spherules, (vi) glass-like carbon containing nanodiamonds, and (vii) fullerenes with ET helium, all of which are evidence for an ET impact and associated biomass burning at ≈12.9 ka. This layer also extends throughout at least 15 Carolina Bays, which are unique, elliptical depressions, oriented to the northwest across the Atlantic Coastal Plain. We propose that one or more large, low-density ET objects exploded over northern North America, partially destabilizing the Laurentide Ice Sheet and triggering YD cooling. The shock wave, thermal pulse, and event-related environmental effects (e.g., extensive biomass burning and food limitations) contributed to end-Pleistocene megafaunal extinctions and adaptive shifts among PaleoAmericans in North America.

Footnotes

  • bTo whom correspondence should be addressed. E-mail.com rbfirestone{at}lbl.gov

  • Author contributions: R.B.F., A.W., J.P.K., L.B., and W.T. designed research; R.B.F., A.W., J.P.K., L.B., T.E.B., Z.S.R., P.H.S., D.J.K., J.M.E., O.J.D., A.C.G., R.S.H., G.A.H., J.B.K., P.L., P.A.M., J.M., R.P., T.D., S.S.Q.H., A.R.S., A.S., W.T., J.H.W., and W.S.W. performed research; R.B.F., A.W., J.P.K., L.B., T.E.B., Z.S.R., T.B., D.J.K., O.J.D., A.C.G., G.A.H., J.B.K., P.L., J.M., R.P., S.S.Q.H., W.T., J.H.W., and W.S.W. contributed new reagents/analytic tools; R.B.F., A.W., J.P.K., L.B., T.E.B., Z.S.R., P.H.S., D.J.K., J.M.E., R.S.H., G.A.H., P.A.M., R.P., T.D., S.S.Q.H., A.R.S., A.S., W.T., J.H.W., and W.S.W. analyzed data; and R.B.F., A.W., J.P.K., and P.H.S. wrote the paper.

  • The authors declare no conflict of interest.

  • This article contains supporting information online at www.pnas.org/cgi/content/full/0706977104/DC1.

  • ↵t Miura, Y., 37th Annual Lunar and Planetary Science Conference, March 13–17, 2006, League City, TX, Vol. 2441, pp. 1–2 (abstr.).

  • ↵u Rösler, W., Hoffmann, V., Raeymaekers, B., Yang, Z. Q., Schryvers, D., Tarcea, N. (2006) First International Conference on Impact Cratering in the Solar System, May 7–12, 2006, Noordwijk, The Netherlands, abstr. 295464.

  • Abbreviations:
    YD,
    Younger Dryas;
    YDB,
    YD boundary;
    ET,
    extraterrestrial.

  • Freely available online through the PNAS open access option.

  1. R. B. Firestonea,b,
  2. A. Westc,
  3. J. P. Kennettd,
  4. L. Beckere,
  5. T. E. Bunchf,
  6. Z. S. Revayg,
  7. P. H. Schultzh,
  8. T. Belgyag,
  9. D. J. Kennetti,
  10. J. M. Erlandsoni,
  11. O. J. Dickensonj,
  12. A. C. Goodyeark,
  13. R. S. Harrish,
  14. G. A. Howardl,
  15. J. B. Kloostermanm,
  16. P. Lechlern,
  17. P. A. Mayewskio,
  18. J. Montgomeryj,
  19. R. Poredap,
  20. T. Darrahp,
  21. S. S. Que Heeq,
  22. A. R. Smitha,
  23. A. Stichr,
  24. W. Toppings,
  25. J. H. Wittkef and
  26. W. S. Wolbachr
  1. aLawrence Berkeley National Laboratory, Berkeley, CA 94720;
  2. cGeoScience Consulting, Dewey, AZ 86327;
  3. dDepartment of Earth Sciences and
  4. eInstitute of Crustal Studies, University of California, Santa Barbara, CA 93106;
  5. fNorthern Arizona University, Flagstaff, AZ 86011;
  6. gInstitute for Isotope and Surface Chemistry, H-1525, Budapest, Hungary;
  7. hDepartment of Geological Sciences, Brown University, Providence, RI 02912;
  8. iDepartment of Anthropology and Museum of Natural and Cultural History, University of Oregon, Eugene, OR 97403;
  9. jEastern New Mexico University, Portales, NM 88130;
  10. kSouth Carolina Institute of Archaeology and Anthropology, University of South Carolina, Columbia, SC 29208;
  11. lRestoration Systems, LLC, Raleigh, NC 27604;
  12. mRozenstraat 85, 1018 NN, Amsterdam, The Netherlands;
  13. nBureau of Mines and Geology, University of Nevada, Reno, NV 89557;
  14. oClimate Change Institute, University of Maine, Orono, ME 04469;
  15. pUniversity of Rochester, Rochester, NY 14627;
  16. qDepartment of Environmental Health Sciences, University of California, Los Angeles, CA 90095;
  17. sP.O. Box 141, Irons, MI 49644; and
  18. rDepartment of Chemistry, DePaul University, Chicago, IL 60614

  1. Communicated by Steven M. Stanley, University of Hawaii at Manoa, Honolulu, HI, July 26, 2007 (received for review March 13, 2007)

Abstract

A carbon-rich black layer, dating to ≈12.9 ka, has been previously identified at ≈50 Clovis-age sites across North America and appears contemporaneous with the abrupt onset of Younger Dryas (YD) cooling. The in situ bones of extinct Pleistocene megafauna, along with Clovis tool assemblages, occur below this black layer but not within or above it. Causes for the extinctions, YD cooling, and termination of Clovis culture have long been controversial. In this paper, we provide evidence for an extraterrestrial (ET) impact event at ≅12.9 ka, which we hypothesize caused abrupt environmental changes that contributed to YD cooling, major ecological reorganization, broad-scale extinctions, and rapid human behavioral shifts at the end of the Clovis Period. Clovis-age sites in North American are overlain by a thin, discrete layer with varying peak abundances of (i) magnetic grains with iridium, (ii) magnetic microspherules, (iii) charcoal, (iv) soot, (v) carbon spherules, (vi) glass-like carbon containing nanodiamonds, and (vii) fullerenes with ET helium, all of which are evidence for an ET impact and associated biomass burning at ≈12.9 ka. This layer also extends throughout at least 15 Carolina Bays, which are unique, elliptical depressions, oriented to the northwest across the Atlantic Coastal Plain. We propose that one or more large, low-density ET objects exploded over northern North America, partially destabilizing the Laurentide Ice Sheet and triggering YD cooling. The shock wave, thermal pulse, and event-related environmental effects (e.g., extensive biomass burning and food limitations) contributed to end-Pleistocene megafaunal extinctions and adaptive shifts among PaleoAmericans in North America.

  • comet
  • iridium
  • micrometeorites
  • nanodiamonds
  • spherules

Footnotes

  • bTo whom correspondence should be addressed. E-mail.com rbfirestone{at}lbl.gov

  • Author contributions: R.B.F., A.W., J.P.K., L.B., and W.T. designed research; R.B.F., A.W., J.P.K., L.B., T.E.B., Z.S.R., P.H.S., D.J.K., J.M.E., O.J.D., A.C.G., R.S.H., G.A.H., J.B.K., P.L., P.A.M., J.M., R.P., T.D., S.S.Q.H., A.R.S., A.S., W.T., J.H.W., and W.S.W. performed research; R.B.F., A.W., J.P.K., L.B., T.E.B., Z.S.R., T.B., D.J.K., O.J.D., A.C.G., G.A.H., J.B.K., P.L., J.M., R.P., S.S.Q.H., W.T., J.H.W., and W.S.W. contributed new reagents/analytic tools; R.B.F., A.W., J.P.K., L.B., T.E.B., Z.S.R., P.H.S., D.J.K., J.M.E., R.S.H., G.A.H., P.A.M., R.P., T.D., S.S.Q.H., A.R.S., A.S., W.T., J.H.W., and W.S.W. analyzed data; and R.B.F., A.W., J.P.K., and P.H.S. wrote the paper.

  • The authors declare no conflict of interest.

  • This article contains supporting information online at www.pnas.org/cgi/content/full/0706977104/DC1.

  • ↵t Miura, Y., 37th Annual Lunar and Planetary Science Conference, March 13–17, 2006, League City, TX, Vol. 2441, pp. 1–2 (abstr.).

  • ↵u Rösler, W., Hoffmann, V., Raeymaekers, B., Yang, Z. Q., Schryvers, D., Tarcea, N. (2006) First International Conference on Impact Cratering in the Solar System, May 7–12, 2006, Noordwijk, The Netherlands, abstr. 295464.

  • Abbreviations:
    YD,
    Younger Dryas;
    YDB,
    YD boundary;
    ET,
    extraterrestrial.

  • Freely available online through the PNAS open access option.

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Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling
R. B. Firestone, A. West, J. P. Kennett, L. Becker, T. E. Bunch, Z. S. Revay, P. H. Schultz, T. Belgya, D. J. Kennett, J. M. Erlandson, O. J. Dickenson, A. C. Goodyear, R. S. Harris, G. A. Howard, J. B. Kloosterman, P. Lechler, P. A. Mayewski, J. Montgomery, R. Poreda, T. Darrah, S. S. Que Hee, A. R. Smith, A. Stich, W. Topping, J. H. Wittke, W. S. Wolbach
Proceedings of the National Academy of Sciences Oct 2007, 104 (41) 16016-16021; DOI: 10.1073/pnas.0706977104
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