[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Theories on the extinction of dinosaurs

In a message dated 11/16/99 7:20:05 AM EST, jbois@umd5.umd.edu writes:

<< There is _no_ precise timing for the faunal changes in western interior
 North America.  That is, the K/T happened only "approximately" at the same
 time as the Lancian/Puercan transition (quote from Lillegraven and Eberle
 1999 Vert Faun Cha through Lanc. and Pu.  Journal of Paleontology 73
 691--).  In other words, where dino extinction is well recorded, we're
 still guessing as to the exact time of disappearance.  And yes,
 the argument that a huge asteroid hit around then, and around then all
 dinos became extinct, so the asteroid must have hit at the same time--is
 circular. >>

Actually, we don't need a precise timing; all we need is to note that below 
K-T boundary clay there are plentiful dinosaur fossils, and above K-T 
boundary clay there are only reworked dinosaur fossils if any. This is what 
is found everywhere in the world so far, and it strongly suggests the 
boundary clay had something to do with dinosaur extinction. Boundary clay 
does have a pretty secure date (64.9-65.0 Ma or thereabouts) everywhere that 
it has been dated.

Asteroid impact theory of dinosaur extinction could be falsified by one 
decent dinosaurian fauna from above the boundary clay, but despite rumors 
such has not yet been found.