Fungus, not comet or catastrophe, accounts for carbonaceous spherules in the Younger Dryas "impact layer"

Scott, Andrew C. and Pinter, Nicholas and Collinson, Margaret E. and Hardiman, Mark and Anderson, R. Scott and Brain, Anthony P.R. and Smith, Selena Y. and Marone, Federica and Stampanoni, Marco (2010) Fungus, not comet or catastrophe, accounts for carbonaceous spherules in the Younger Dryas "impact layer". Geophysical Research Letters, 37. L14302. ISSN 1944-8007

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Abstract

A claim attributes the onset of the Younger Dryas climate interval and a range of other effects 12,900 years ago to a comet airburst and/or impact event. One key aspect of this claim centers on the origin of carbonaceous spherules that purportedly formed during intense, impact-ignited wildfires. Samples from Pleistocene-Holocene sedimentary sequences in the California Channel Islands and other sites show that carbon spherules and elongate forms are common in samples dating to before, during, and well after the 12,900-year time horizon, including from modern samples. Microscopic studies show that carbon spherules have morphologies and internal structures identical to fungal sclerotia (such as Sclerotium and Cenococcum). Experimental charring of fungal sclerotia shows that their reflectance increases with temperature. Reflectance measurements of modern and late Pleistocene spherules show that the latter indicate, at most, low-intensity burning. These data cast further doubt upon the evidence suggesting a catastrophic Younger Dryas impact event. Copyright 2010 by the American Geophysical Union.

Item Type:	Article
Publisher’s Statement:	© 2010. American Geophysical Union. All Rights Reserved.
ID number or DOI:	10.1029/2010GL043345
Keywords:	extraterrestrial impact; Lithium batteries; Reflection; soils; transition; Wildfire
Subjects:	Q Science > QH Natural history
NAU Depositing Author Academic Status:	Faculty/Staff
Department/Unit:	College of Engineering, Forestry, and Natural Science > School of Earth Sciences and Environmental Sustainability
Date Deposited:	16 Oct 2015 21:06
URI:	http://openknowledge.nau.edu/id/eprint/721

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