Little Bird Update:
A little bird called me to make a couple of points related to my blog last night regarding the (limited) Firestone quotes provided at Anthro.net.
1) Rick apparently used “we” inappropriately when claiming Surovell was biased. Other YD team members do not think Surovell was biased — and surely not malignly biased to the extent he would deliberately select a methodology that would fail to reveal the facts. Here is Rick’s quote:
We find these results biased towards a specific conclusion and inconsistent with a broad range of impact markers found at dozens of sites across North America and into Europe. Attempts by others to independently report results confirming our research have systematically been rejected by reviewers primary on the basis that no impact occurred.
— Rick Firestone (using an Imperial ‘We’?)
2) Paquay’s PNAS article does not refute the YDB hypothesis as thoroughly as reported by me and others. For one, his determination that the chemical anomalies were terrestrial is admitted by the YDB team (as they published here). Also, his results are consistent in several ways with the YDB hypothesis. A matter on which we will report more throughly in the future.
As described in my earlier re-cap of the Allen West presentation at San Francisco AGU, the YDB team disagreed that Surovell and Paquay‘s findings reliably refute the YDB hypothesis. Dr. West did a fine job explaining why this is so in person at AGU. But on Anthropology.net — linked here and excerpted below — Rick Firestone gives a written critique of the critics’ flawed methodology.
For what it is worth, the inspiration for the The Cosmic Tusk was in-part provided when I read this discussion on Anthropology.net late last year (Dec 16, 2009). I thought the editor at Anthoropolgy.net left out critical information in the blog discussion — and I can’t tell if Rick provided it. Regardless, they did not include the other confirming studies of the YDB at Fall AGU, particularly those from Tom Stafford, Marie-Agnes Courty, and Sharma. In other words, Anthropology.net addressed new science that was relatively critical of the YDB hypothesis — but ignored new science relatively supportive of it.
(I was also disappointed when I left two comments on Anthropology.net, offering links to the Stafford, Sharma and Courty papers — but the comments never appeared. I have no idea why. It could be a technical failure of the comments systems — or it could that the editors at Anthro.net just wanted to limit the discussion. I would love to hear from them on The Tusk.)
In any case, here are some excerpts from the discussion at Anthropology.net.
And coming soon: The next and 2nd installment of my re-cap of Fall AGU, concerning the presentation from Tom Stafford on the YDB at Hall’s Cave Clovis Site (which is out of order — but this is my playground).
Anthropology.net:Having already posted two articles which call into question the findings of Richard Firestone et al, in their 2007 paper Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling, I decided to contact Dr. Firestone to try and add some balance to the current debate; it’s all very well reporting on new research which appears to flatly contradict previously published work, but I think it very important to give the original research team an opportunity to voice their opinion of the new findings. Because there were differences in the various methodologies employed by the various teams of researchers, it should be no surprise that the findings were at variance with one another. However, it is unusual for subsequent research to completely contradict previous research conducted only a couple of years beforehand, so clearly there is need for further clarification from both sides.
Surovell et al failed to confirm the YD Impact data because their sampling methods were fatally flawed. We discovered that the impact layer was very narrow, often millimeters thick, and used painstaking microstratigraphy to find it. Although the impact layer initially was deposited just before the formation of the black mat, the magnetic and organic fractions containing the most compelling information often moved about due to turbation of the sediment following deposition.
Surovell et al did no microstratigraphy and analyzed substantially wider sediment layers that included mostly normal sediment. Thus their results greatly diluted the impact layer contribution to their samples. Also, Surovell et al chose to recognize only magnetic microspherules that are round and shiny. It is well known that meteoritic dust is generally not perfectly round, often pitted and dull, and generally weathered. Despite all of these failures the distributions of magnetic grains and microsph erules shown by Surovell et al at all of their sites do show increases at the time of the YD impact which are consistent with our own results after correction for the sampling dilution effects. Surovell et al’s conclusions are clearly influenced by their own bias and not by a fair analysis of their own data.
Paquay et al claim to find no evidence for PGE elements in there sediment samples. We too found much weaker evidence for iridium in the sediment samples than in the magnetic fractions because the iridium is only found in the magnetic material which is a small fraction by weight of the total sediment even in the best cases where microstratigraphy was applied. As was the case with Surovell et al, Paquay et al took very broad sediment samples diluting their results. They used a shotgun approach to sample selection with no assurance that they had even sampled the YD Impact layer. This is especially important because the thin impact layer often disappears from point to point due to the effects of wind, rain, and time.
Despite these experimental problems Paquay et al do report high concentrations of PGE elements at a site where we reported them and then dismiss them as normal despite the fact that their results were higher than were seen at some K/T sites. Before we publishe d our PNAS paper, Sharma et al (Dartmouth) independently found convincing evidence for large Osmium anomalies in Pacific Ocean sediments dated to about 12,000 years ago. His paper was rejected by PNAS because “no impact occurred at that time”. Sharma has since found additional evidence for PGE’s in the YD Impact layer which are reported at the SF AGU meeting this year. Weaker evidence of excess Iridium associated with the YD layer in Greenland ice has also been found by Paul Mayewski.
To summarize, the results published by Surovell et al and Paquay et al are both fatally flawed by their sampling techniques that failed utilize the microstratigraphy necessary to identify the YD impact layer. Both authors thus analyzed highly diluted samples, published data showing smaller peaks in magnetic grains, microspherules, and PGE’s consistent with our own results, and then persisted on describing their results as within normal variations. We find these results biased towards a specific conclusion and inconsistent with a broad range of impact markers found at dozens of sites across North America and into Europe. Attempts by others to independently report results confirming our research have systematically been rejected by reviewers primary on the basis that no impact occurred.