Re: EXTINCTION

[Scott <HORTON@BCRSSU.AGR.CA>]

  I had mostly accepted the impact theory based on:
1. The presence of iridium at the K/T boundary
2. The dinosaur fossil record ending abruptly at the iridium layer
3. The Chixulub crater being of more than sufficient size and the correct age
   (if you find someone standing over a dying body, with a smoking gun in his
   hand, what conclusion would you come to?)
4. There are no other convincing theories to explain the extinction of large
   reptiles (land, air, and sea) while preserving mammals, birds, amphibians,
   crodilians.

  Recent postings on the list have attacked points 2, 3, and 4. I think that
points 2 and 3 are still controversial. As for point 1, it has been suggested
elsewhere that iridium could have been produced by volcanic events such as the
Deccan Traps. That leaves point 4, and I am still not convinced by alternate
theories. Therefore I find the best solution to be:
a) suspect that reports of dinosaur dwindling prior to the K/T boundary to be
   a systematic error
b) _IF_ the Chixulub crater turns out not to be an astrobleme, consider that
   the impact occurred in deep ocean (where it would be covered in sand and
   virtually invisible), or that the impact was a volatile comet (that left no
   crater)

Scott Horton
Geophysicist/Computer Programmer