Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling
Description/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 environmentalchanges 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.
| Creator/Author: | Firestone, Richard B ; Firestone, R.B. ; West, A. ; Kennett, J.P. ; Becker, L. ; Bunch, T.E. ; Revay, Z.S. ; Schultz, P.H. ; Belgya, T. ; Kennett, D.J. ; Erlandson, J.M. ; Dickenson, O.J. ; Goodyear, A.C. ; Harris, R.S. ; Howard, G.A. ; Kloosterman, J.B. ; Lechler, P. ; Mayewski, P.A. ; Montgomery, J. ; Poreda, R. ; Darrah, T. ; Hee, S.S. Que ; Smith, A.R. ; Stich, A. ; Topping, W. ; Wittke, J.H. ; Wolbach, W.S. |
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| Publication Date: | 2007 Mar 13 |
| OSTI Identifier: | OSTI ID: 935340 |
| Report Number(s): | LBNL-690E |
| DOE Contract Number: | DE-AC02-05CH11231 |
| Other Number(s): | TRN: US200815%%656 |
| Resource Type: | Journal Article |
| Resource Relation: | Journal Name: Proceedings of the National Academy of Science (PNAS); Journal Volume: 104; Journal Issue: 41; Related Information: Journal Publication Date: October 2007 |
| Research Org: | Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US) |
| Sponsoring Org: | Nuclear Science Division |
| Subject: | 59; 54; 58; 79; AGE ESTIMATION; BIOMASS; CARBON; CHARCOAL; ENVIRONMENTAL EFFECTS; FOOD; FULLERENES; HELIUM; IRIDIUM; NORTH AMERICA; SHOCK WAVES; SOOT |
| Related Subject: | comet, iridium, micrometeorites, nanodiamonds, spherules |
| Country of Publication: | United States |
| Language: | English |
| Format: | Size: 6 |
| Update Date: | 2009 Dec 16 |
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