Academic Bun Fight: Chobot Lake (Canada) Evdience for a Younger Dryas Impact?

Reply to Ives and Froese: Regarding the impact-related Younger Dryas boundary layer at Chobot site, Alberta, Canada

Authors:

James H. Wittke, Ted E. Bunch, Kenneth B. Tankersley, I. Randolph Daniel, Jr., Johan B. Kloosterman, Gunther Kletetschka, Allen West, and Richard B. Firestone

Excerpt:

Ives and Froese (1) challenge the identification of the Chobot black mat layer at the Younger Dryas (YD) boundary (YDB), claiming that no black mats have been documented in western Canada (2). To the contrary, Haynes, a lead investigator of YD-age black mats, mapped two YD-age mat sites in western Canada (figure 1 in ref. 3): one ∼200 km south of the Chobot site at Vermillion Lakes in Alberta (12,719 ± 156 cal BP) and another at the Niske site in Saskatchewan (12,748 ± 020 cal BP).

Furthermore, Ives and Froese (1) claim the Chobot black mat is simply an organic layer of “surface leaf litter and humic materials” with no evidence for a “black algal mat.” We do not claim that the mat is algal in origin (2), nor is that a requirement. Haynes (3) describes YD black mats as being “dark gray to black because of increased organic carbon (0.05–8%)” and that sometimes, the mats are algal, but, often, the mats are simply enriched in charcoal, humates, diatomite, and other organics. Nonalgal black mats are present at Folsom, NM (3); Arlington Canyon, CA (2, 3); Sheriden Cave, OH (2); Lommel, Belgium (2); and Abu Hureyra, Syria (2); as well as at the Chobot site (2).

and in reply...

The Chobot site (Alberta, Canada) cannot provide evidence of a cosmic impact 12,800 y ago

Authors:

John W. Ives and Duane Froese

Excerpt:

Continued reference in the paper by Wittke et al. (1) to the Chobot site regarding an impact occurring at the Younger Dryas boundary (YDB) concerns scientists familiar with this region. The authors claim that no radiometric dating at the site is possible but have previously reported ages that are not consistent with their interpretation. They also claim that abundant Clovis points are present to justify the age of the site and associated impact spherules.

Chobot and other sites surrounding Buck Lake have been investigated by professional archaeologists within the provisions of the Historical Resources Act of Alberta. The Chobot site is thinly stratified: artifact bearing deposits are within 50 cm of the surface. Critically, the Chobot collection contains a record of the entire Holocene cultural sequence, with rare Early Prehistoric and more common Middle and Late Prehistoric diagnostic projectile points. Spatial analytical approaches can be applied to disentangle such records to a degree but require rigorous analysis of provenience data, a measure not applied at this site. The statement by Wittke et al. (1) that there are abundant Clovis points is not accurate: The fluted point they illustrate is one of three known from the site (2). Similarly, the assertion that there are “tens of thousands of Clovis-age flakes and tools” (1) is unsubstantiated. Because the great majority of diagnostics postdate the Clovis era, most accompanying artifacts are undoubtedly from later time intervals too (e.g., ref. 3). Charlie Lake Cave has provided the only radiometric dates for fluted points in western Canada (4). There, fluted points postdate the YDB; this could also be true of the Chobot fluted points.