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North America comet theory questioned. No evidence of an extraterrestrial impact 13,000 years ago, studies say by Rex Dalton, Nature News, Published
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
Surovell's co-author Vance Holliday, an archaeologist at the University of Arizona in Tucson, and his colleagues have an article in press at Current Anthropology that says the archaeological and geochronological records don't support a collapse of Clovis people at the time of the purported impact.
Shock-synthesized hexagonal diamonds in Younger Dryas boundary sediments
Douglas J. Kennetta,1, James P. Kennettb, Allen Westc, G. James Westd, Ted E. Bunche, Brendan J. Culletona, Jon M. Erlandsona,f, Shane S. Que Heeg, John R. Johnsonh, Chris Merceri,j, Feng Shenk, Marilee Sellerse, Thomas W. Stafford, Jrl, Adrienne Stichm, James C. Weavern, James H. Wittkee and Wendy S. Wolbachm
The long-standing controversy regarding the late Pleistocene megafaunal extinctions in North America has been invigorated by a hypothesis implicating a cosmic impact at the Ållerød-Younger Dryas boundary or YDB (≈12,900 ± 100 cal BP or 10,900 ± 100 14C years). Abrupt ecosystem disruption caused by this event may have triggered the megafaunal extinctions, along with reductions in other animal populations, including humans. The hypothesis remains controversial due to absence of shocked minerals, tektites, and impact craters. Here, we report the presence of shock-synthesized hexagonal nanodiamonds (lonsdaleite) in YDB sediments dating to ≈12,950 ± 50 cal BP at Arlington Canyon, Santa Rosa Island, California. Lonsdaleite is known on Earth only in meteorites and impact craters, and its presence strongly supports a cosmic impact event, further strengthened by its co-occurrence with other nanometer-sized diamond polymorphs (n-diamonds and cubics). These shock-synthesized diamonds are also associated with proxies indicating major biomass burning (charcoal, carbon spherules, and soot). This biomass burning at the Younger Dryas (YD) onset is regional in extent, based on evidence from adjacent Santa Barbara Basin and coeval with broader continent-wide biomass burning. Biomass burning also coincides with abrupt sediment mass wasting and ecological disruption and the last known occurrence of pygmy mammoths (Mammuthus exilis) on the Channel Islands, correlating with broader animal extinctions throughout North America. The only previously known co-occurrence of nanodiamonds, soot, and extinction is the Cretaceous-Tertiary (K/T) impact layer. These data are consistent with abrupt ecosystem change and megafaunal extinction possibly triggered by a cosmic impact over North America at ≈12,900 ± 100 cal BP.
Originally posted by bigfatfurrytexan
reply to post by Hanslune
it is always glad to read you, hans.
I am sure TWISI will turn up again some day.
Originally posted by Hanslune
New article on status of the clovis comet theory