Forgive me if I'm repeating something already covered on this list, but in case it has not been referenced, for those of you interested in examining continuing evidence that the Cretaceous-Tertiary extinction event was the result of the impact of a cosmic (extra-terrestrial) body or bodies, instead of being due to volcanic activity such as the Deccan traps, new evidence is reported by A. Shukolyukov and G.W. Lugmair in SCIENCE, Vol. 282, pages 927 through 929, October 30, 1998.
The authors report that high-precision mass spectrometric analysis of chromium in sediment samples from the K - T boundary, to quote, "...coincident with the extinction of numerous organisms on Earth...", from Stevns Klint, Denmark, and from Caravaca, Spain, "...is different from that of Earth and indicates its extra-terrestrial source".
We are told that, "...the chromium isotopic signature is consistent with a carbonaceous chondrite-type impactor."
The quotes herewith are from the abstract, page 927.
If any listers wish to discuss this matter on the list, please take time to read the referenced article FIRST, as the evidence is carefully described and discussed therein. Accordingly, please address the report's contents and not my reporting of it. If you're anti impact-extinction, please don't try to shoot the messenger, as I'm only passing along something that could be of interest. SCIENCE's web site is www.sciencemag.org.
For those of you who may not be very familiar with meteorites, carbonaceous chondrite impactors (meteorites) have been compared to the very dark, evidently carbonaceous asteroids that tend to range farthest out (relative to earth's orbit), but indisputable aqueous alteration within some carbonaceous chondrites (meteorites) strongly suggests melt conditions such as are encountered at and near perihelion by comets.
Food for thought, "Was earth -- in the K - T event-- struck by a comet or cometary debris similar to what happened to Jupiter recently, but not on such a grand scale?" I know, that's not a new idea.
Thanks for listening,