Evidence for Widespread Fires at the End Pleistocene

Evidence for Widespread Fires at the End Pleistocene

A. Stich1, G.A. Howard2, J.B. Kloosterman3, A. West4, R.B. Firestone5, J.P. Kennett6, D.J. Kennett7, T.E. Bunch8, W.S. Wolbach1

1DePaul University, Department of Chemistry, 1036 W. Belden Ave., Chicago, IL 60614
2Restoration Systems, L.L.C., 1101 Haynes Street Suite 107, Raleigh, NC 27604
3Rozenstraat 85, 1018 NN, Amsterdam, Netherlands
4GeoScience Consulting, P.O.Box 1636, Dewey, AZ 86327
5Lawrence Berkeley National Laboratory, 1 Cyclotron Road Mail Stop 88R0192, Berkeley, CA 94720
6University of California, Santa Barbara, Institute of Crustal Studies, Santa Barbara, CA 93106
7University of Oregon, Dept. of Anthropology, Eugene, OR 97403
8Northern Arizona University, Dept. of Geology, Flagstaff, AZ, 86011

Accumulating data support an extraterrestrial contribution to the End Pleistocene extinctions. Sediments at the base of a carbon-rich, dark layer, called the YDB, dating to ~12.9 ka contain magnetic grains, microspherules, elevated iridium, nanodiamonds, and other evidence consistent with extraterrestrial impact [1,2]. We further tested the possibility that combustion of the impactor, carbon-bearing rocks, or biomass might have been triggered by the impact, as hypothesized at the End Cretaceous 65 Ma ago [4]. Previous analysis of samples from North America, Germany, and Belgium yielded YDB soot at two sites in North America: Murray Springs, AZ, with a soot content of 20 ± 2 ppm; and a Carolina Bay, Blackville, SC, with a soot content of 2000 ± 200 ppm [5].

In this study, we report results from twenty-three additional samples from seven sites in North America, Belgium, and the Middle East: Arlington Canyon, CA; Arlington Springs, CA; Bull Creek, OK; Hall’s Cave, TX; Murray Springs, AZ (new sampling); Lommel, Belgium; Abu Hureyra, Syria. Dissolution and analysis procedures were based on those used successfully for detecting soot from impact- produced wildfires at the Cretaceous-Tertiary (K/T) boundary and have previously been described [5].

Four of these sites (nine total samples) contained significant quantities of YDB soot: Arlington Canyon, CA, with a soot content of 2000 ± 200 ppm; Bull Creek, OK, with a soot content of 500 ± 50 ppm; Hall’s Cave, TX, with a soot content of 2000 ± 200 ppm; and Murray Springs, AZ, with a soot content of 6000 ± 600 ppm, ~30x times higher than observed previously at this location. None of the remaining End Pleistocene samples studied showed significant soot contents, including all non-impact layers above or below the YDB. The absence of YDB soot at other locations could indicate absence of burning in those regions, lack of soot transport to and/or deposition, or local depositional conditions that were too oxidizing to support soot preservation.

The presence of significant YDB soot at five separate locations across North America (CA, AZ, OK, TX, and SC) suggests significant, widespread burning and aeolian transport of soot across North America ~12.9 ka ago. These results support a size and energy of impact sufficient to ignite continental-scale fires.

[1] Firestone R.B., West A., Kennett J.P., Becker L., Bunch T.E., et al. (2007) Proceedings of the National Academy of Sciences 104, 16016-16021.
[2] Kennett, D.J., Kennett, J.P., West, A., Mercer, C., Que Hee, S.S., et al., Science, submitted.
[3] Kennett, D.J., Kennett, J.P., West, A., West, J., Bunch, T.E. et al., Science, submitted.
[4] Wolbach W. S., Lewis R. S., and Anders E. (1985) Science 230, 167-170.
[5] Wolbach, W.S., Stich, A., Kloosterman, J.B., Becker, L., Kennett, J., et al. (2007) Eos Trans. AGU, 88 (23), Jt. Assem. Suppl. Abstract PP43A-03.
[6] Wolbach W.S., Gilmour I., Anders E., Orth C.J., and Brooks R.R. (1988) Nature 334, 665-669.
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