Just for info, i received this through"Newswise.
California's Channel Islands Hold Evidence of Clovis-age Comets
Newswise — A 17-member team has found what may be the smoking gun of a much-debated proposal that a cosmic impact about 12,900 years ago ripped through North America and drove multiple species into extinction.
In a paper appearing online ahead of regular publication in the Proceedings of the National Academy of Sciences, University of Oregon archaeologist Douglas J. Kennett and colleagues from nine institutions and three private research companies report the presence of shock-synthesized hexagonal diamonds in 12,900-year-old sediments on the Northern Channel Islands off the southern California coast.
Source: University of Oregon Mon 20-Jul-2009 Click here for more
See also the Scientific American summary on the same subject: Click here for more
I won't comment since this isn't my field of interest...