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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.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1110614109/-/DCSupplemental.
†Dates in calendar years before present, unless noted; ka = kiloannum, or 1,000 calendar years
‡Andronikov AV, Lauretta DS, Andronikva IE, Maxwell RJ, On the possibility of a late Pleistocene, extraterrestrial impact: LA-ICP-MS analysis of the black mat and Usselo Horizon samples, 74th Annual Meteoritical Society Meeting, August 8–12, 2011, London, UK, Supplement, #5008.
§Van Hoesel A, Hoek W, Braadbaart F, van der Plicht H, Drury MR, Nanodiamonds and the Usselo layer, INQUA XVIII, July 21–27, 2011, Bern Switzerland, #1556.
¶Higgins MD, et al., Bathymetric and petrological evidence for a young (Pleistocene?) 4-km diameter impact crater in the Gulf of Saint Lawrence, Canada, 42nd Lunar and Planetary Science Conference, March 7–11, 2011, The Woodlands, TX, 1504 LPI Contribution No. 1608.
**y = -5E-07x5 + 6E-05x4 - 0.0025x3 + 0.0366x2 - 0.0108x + 0.512; R2 = 0.946
††Petaev MI, Jacobsen SB, Basu AR, Becker L, Magnetic Fe, Si, Al-rich impact spherules from the P-T boundary layer at Graphite Peak, Antarctica, 35th Lunar and Planetary Conference, March 15–19, 2004, Houston, TX, 1216 (abstr.).
‡‡Masaitis VL, Impact diamonds from astroblemes, Mineralogical Society of America 1996 Spring Meeting, May 20—24, 1996, Baltimore, MD, abstract supplement to Eos Transactions, S142–S143.
§§Bunch TE, West A, Wittke J, Kennett JP, New physical evidence for a cosmic impact with the Earth at 129 ka, American Quaternary Association (AMQUA) 5, August 12–15, 2010, Laramie, WY, paper #3.
¶¶LeCompte MA, et al., Summary of unusual material in early Younger Dryas age sediments and their potential relevance to the YD Impact Hypothesis, INQUA XVIII, July 21–27, 2011, Bern Switzerland, (abstr.) 1813.
***Kimbel D, West A, Kennett JP, A new method for producing nanodiamonds based on research into the Younger Dryas extraterrestrial impact, AGU Fall Meeting, December 15–19, 2008, Eos Trans. AGU, 90(52), Fall Meet. Suppl., #PP13C-1470.
Freely available online through the PNAS open access option.
Evidence from central Mexico supporting the Younger Dryas extraterrestrial impact hypothesis
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