At http://cosmictusk.com/surovell-comet-asteroid-impactyounger-dryas-edward… … however, the paper, lead author astrophysicist Malcolm LeCompte, stops short of saying there is positive evidence of a cosmic impact. What they had found, according to LeCompte, is evidence consistent with an impact but it does not yet prove one took place. There is a mystery contained in the Younger Dryas strata – what that is has yet to be established. The spherules in question are evidence of high temperature emlting followed by very rapid cooling, which is characteristic of debris ejected from an impact (or fireball). At the quarry site of Topper the event produced a dead zone of around 1000 years and this suggests something dramatic had occurred.
At http://phys.org/print267175370.html … the Topper site is once again the highlight of the posting on the second day of new releases and interviews on the PNAS paper, filtering in some further information. This piece also provides some archaeological data from Topper. We have a nice time line of what and when was found over the last few years, which includes evidence of human activity at the site (tool making) some 16,000 years ago, well in advance of the classic Clovis culture period. Secondly, even deeper strata has revealed burnt plant remains that have been dated 50,000 years ago. This indicates humans were in North America prior to the Late Glacial Maximum, the phase of the last Ice Age that involved an ice sheet reaching below the Great Lakes. In 2013, we are informed, as long away as next October, the pre Clovis activity at the Topper chert quarry will be discussed at a conference on peopling the Americas, 'Paleoamerican Odyssey (and there is even a web site on the conference, go www.paleoamericanodyssey.com). Another good overview, sent in by Lawrence Dixon (and please keep them coming people) is at www.sciencedaily.com/releases/2012/09/120918111320.htm)