Age division?

["Jordan Mallon" <j_mallon@hotmail.com>]

I've heard things like "_T. rex_ was from the Late Maastrichtian," but does 
this really mean anything quantitatively?  Are geological ages separated 
according to time like that?  (i.e., would "Late Maastrichtian" mean 
something like 68-65 Ma?)  I'm just looking to put some numbers to these 
distinctions.  I get the impression that anything past the Age category is 
fairly subjective.
Thanks,

Jordan Mallon

http://www.geocities.com/paleoportfolio/
AIM: jslice mallon


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