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Evidence from central Mexico supporting the Younger Dryas extraterrestrial impact hypothesis

  1. Wendy S. Wolbachn
  1. aDepartamento de Geología y Mineralogía, Edif. U-4. Instituto de Investigaciones Metalúrgicas, Universidad Michoacana de San Nicólas de Hidalgo, C. P. 58060, Morelia, Michoacán, México;
  2. bUS Geological Survey, Menlo Park, CA, 94025;
  3. cFacultad de Biología, Universidad Michoacana de San Nicólas Hidalgo C. P. 58060, Morelia, Michoacán, México;
  4. dDepartment of Geosciences, National Taiwan University, Taipei 106, Taiwan, Republic of China;
  5. eSRI International, Menlo Park, CA 94025;
  6. fGeology Program, School of Earth Science and Environmental Sustainability, Northern Arizona University, Flagstaff AZ 86011;
  7. gWyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, MA 02138;
  8. hLawrence Berkeley National Laboratory, Berkeley, CA 94720;
  9. IGeoScience Consulting, Dewey, AZ 86327;
  10. jDepartment of Earth Science and Marine Science Institute, University of California, Santa Barbara, CA 93106;
  11. kNational Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047, Japan;
  12. lCAMCOR High Resolution and MicroAnalytical Facilities, University of Oregon, Eugene, OR 97403;
  13. mMaterials Science Institute, University of Oregon, Eugene, Oregon 97403; and
  14. nDepartment of Chemistry, DePaul University, Chicago, IL 60614
  1. Edited by* Steven M. Stanley, University of Hawaii, Honolulu, HI, and approved January 31, 2012 (received for review July 13, 2011)

Abstract

We report the discovery in Lake Cuitzeo in central Mexico of a black, carbon-rich, lacustrine layer, containing nanodiamonds, microspherules, and other unusual materials that date to the early Younger Dryas and are interpreted to result from an extraterrestrial impact. These proxies were found in a 27-m-long core as part of an interdisciplinary effort to extract a paleoclimate record back through the previous interglacial. Our attention focused early on an anomalous, 10-cm-thick, carbon-rich layer at a depth of 2.8?m that dates to 12.9?ka and coincides with a suite of anomalous coeval environmental and biotic changes independently recognized in other regional lake sequences. Collectively, these changes have produced the most distinctive boundary layer in the late Quaternary record. This layer contains a diverse, abundant assemblage of impact-related markers, including nanodiamonds, carbon spherules, and magnetic spherules with rapid melting/quenching textures, all reaching synchronous peaks immediately beneath a layer containing the largest peak of charcoal in the core. Analyses by multiple methods demonstrate the presence of three allotropes of nanodiamond: n-diamond, i-carbon, and hexagonal nanodiamond (lonsdaleite), in order of estimated relative abundance. This nanodiamond-rich layer is consistent with the Younger Dryas boundary layer found at numerous sites across North America, Greenland, and Western Europe. We have examined multiple hypotheses to account for these observations and find the evidence cannot be explained by any known terrestrial mechanism. It is, however, consistent with the Younger Dryas boundary impact hypothesis postulating a major extraterrestrial impact involving multiple airburst(s) and and/or ground impact(s) at 12.9?ka.

Footnotes

  • ?1To whom correspondence should be addressed. E-mail: jbischoff{at}usgs.gov.
  • I.I.-A., J.L.B., G.D.-V., H.-C.L., T.E.B., A.W., S.X., and W.S.W. designed research; I.I.-A., J.L.B., G.D.-V., H.-C.L., T.E.B., J.H.W., J.C.W., A.W., S.X., E.K.R., C.R.K., and W.S.W. performed research; I.I.-A., J.L.B., G.D.-V., H.-C.L., P.S.D., T.E.B., J.H.W., J.C.W., R.B.F., A.W., J.P.K., C.M., S.X., E.K.R., and W.S.W. analyzed data; and I.I.-A., J.L.B., G.D.-V., P.S.D., R.B.F., A.W., J.P.K., and C.M. wrote the paper.

  • The authors declare no conflict of interest.

  • *This Direct Submission article had a prearranged editor.

  • See Author Summary on page 4723 (volume 109, number 13).

  • This article contains supporting information online at www.danielhellerman.com/lookup/suppl/doi:10.1073/pnas.1110614109/-/DCSupplemental.

Freely available online through the PNAS open access option.

Online Impact

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