New Papers a nd Talks Dispute Younger Dryas Extraterrestrial Impact Hypothesis

[Paul <bristolia@yahoo.com>]

A number of new papers and talks dispute the Younger Dryas 
Extraterrestrial Impact Hypothesis. They are:

North America comet theory questioned. No evidence of an 
extraterrestrial impact 13,000 years ago, studies say by Rex 
Dalton, Nature News, Published online October 12, 2009, 
doi:10.1038/news.2009.997.

http://www.nature.com/news/2009/091012/full/news.2009.997.html 

The paper is: 

Surovell, T. A., V. T. Holliday, J. A. M. Gingerich, C. Ketron, C. Vance 
Haynes, Jr., I. Hilman, D. P. Wagner, E. Johnson, and P. Claeyse. 2009, 
An independent evaluation of the Younger Dryas extraterrestrial 
impact hypothesis. Published online before print October 12, 2009, 
doi: 10.1073/pnas.0907857106

http://www.pnas.org/content/early/2009/10/09/0907857106

Another recent paper disputed the Younger Dryas impact hypothesis. 
It is:

Marlon, J. R., P. J. Bartlein, M. K. Walsh, S. P. Harrison, K. J. 
Brown, M. E. Edwards, P. E. Higuera, M. J. Power, R. S. Anderson, 
C. Briles, A. Brunelle, C. Carcaillet, M. Daniels, F. S. Hu, M. 
Lavoiem, C. Longn, T. Minckley, P. J. H. Richard, A. C. Scott, 
D. S. Shafer, W. Tinners, C. E. Umbanhowar, Jr., and C. Whitlock, 
2009, Wildfire responses to abrupt climate change in North 
America. Proceedinds of the National Academy of Sciences. 
vol. 106, no. 8, pp. 2519-2524. doi: 10.1073/pnas.0808212106 

http://www.pnas.org/content/106/8/2519 .

The abstract in part states: 

"We also test the hypothesis that a comet impact initiated 
continental-scale wildfires at 12.9 ka; the data do not support 
this idea, nor are continent-wide fires indicated at any time 
during deglaciation." 

and 

"Biomass burning gradually increased from the glacial period to 
the beginning of the Younger Dryas. Although there are changes 
in biomass burning during the Younger Dryas, there is no 
systematic trend. There is a further increase in biomass burning 
after the Younger Dryas. Intervals of rapid climate change at 
13.9, 13.2, and 11.7 ka are marked by large increases in fire 
activity." 

This paper conclu
wide fire response is observed at the beginning 
of the Younger Dryas chronozone, the time of the hypothesized 
comet impact. The results provide no evidence of synchronous 
continent-wide biomass burning at any time during the LGIT." 

Note "LGIT" = last glacialâinterglacial transition.

Four papers about the Younger Dryas Impact Hypothesis were 
presented at the 2009 GSA Meeting in Portland, Oregon "T94. Impact 
Cratering from the Microscopic to the Planetary Scale II (GSA 
Planetary Geology Division; International Continental Scientific 
Drilling Program [ICDP]; GSA Sedimentary Geology Division; GSA 
Structural Geology and Tectonics Division; GSA Geophysics Division; 
Paleontological Society; GSA International Division) at

http://gsa.confex.com/gsa/2009AM/finalprogram/session_25177.htm

They are:

1. Dryas. Pinter, N., A. C. Andrew, and D. Ebel, 2009, 
Extraterrestrial and Terrestrial Signatures at the Onset of 
the Younger Geological Society of America Abstracts with 
Programs. 

http://gsa.confex.com/gsa/2009AM/finalprogram/abstract_162563.htm

2. Holliday, V. T., and D. J. Meltzer, 2009, Geoarchaeology 
of the 12.9ka Impact hypothesis. Geological Society of 
America Abstracts with Programs. 

http://gsa.confex.com/gsa/2009AM/finalprogram/abstract_160959.htm

3. Paquay, F., S. Goderis, G. Ravizza, and P. Claeys, 2009, No 
evidence of of extraterrestrial geochemical components at the 
Bolling-Allerod/Younger Dryas Transition. Geological Society 
of America Abstracts with Programs. 

http://gsa.confex.com/gsa/2009AM/finalprogram/abstract_163154.htm

4. Surovell, T. A., and V. T. Holliday, 2009, Non- 
reproducibility of Younger Dryas Extraterrestrial Impact 
Results. Geological Society of America Abstracts with 
Programs. 

http://gsa.confex.com/gsa/2009AM/finalprogram/abstract_163912.htm

Finally, two recently published papers related to the Younger 
Dryas Impact Hypothesis are:

Woodman, N., and N. B. Athfiel, 2009, Post-Clovis survival of 
American Mastodon in the southern Great Lakes Region of North 
Ame
ry Research. vol. 72, no. 3, pp. 359-363.

http://dx.doi.org/10.1016/j.yqres.2009.06.009

One statement in the paper is:

"Previous study of relative numbers of preserved spores of 
the dung fungus Sporormiella, used as a proxy for megafaunal 
biomass, suggests that populations of large mammals were in 
steep decline in northeastern North America before the onset 
of the YDC."

Another paper with a related topic is:

Newby, P., J. Bradley, A. Spiess, B. Shuman, and P. Leduc, 2009, A 
Paleoindian response to Younger Dryas climate change.Quaternary 
Science Reviews. vol. 24, no. 1-2, pp. 141-154. 
doi:10.1016/j.quascirev.2004.04.010 

http://dx.doi.org/10.1016/j.quascirev.2004.04.010

This reminds me of the claims made by a group of researchers, which 
included Luann Becker, for indicators of an extraterrestrial impact 
at the Permian - Triassic and the Bedout High structure being the 
impact crater. Papers were published arguing that evidence of 
extraterrestrial impact, including fullerenes containing  extraterrestrial 
3He, are found at the Permian - Triassic boundary. Later researchers, who 
restudied various Permian - Triassic boundary outcrops, including the 
ones studied by Becker, and could not replicate their findings. The 
evidence used to argue for Bedout High being an impact structure either 
could not be replicated or turned out to be open to alternative 
interpretations. 
Finally, there is a considerable amount of controversy whether the
fullerenes found in these sediments are even of extraterrestrial origin. 

It would be revealing to have a neutral third party collect samples 
for both sides of the Younger Dryas extraterrestrial impact 
hypothesis to analyze from critical outcrops or cores containing a
well-preserved and continuous record including the time of this 
hypothesized event. In addition, the samples would be coded by 
the neutral third party such that neither side would know the 
depth and stratigraphic position of the sample until after they 
had conducted their analyzes as a form of a do
tp://en.wikipedia.org/wiki/Blind_experiment .

Your,

Paul H.