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I wrote:

<<Now, on a related note, so far I've seen mention of three formations
from the Sihetun site, one using a group alias (the Jehol Group) so
I'd like to know if any of you dino-enthusiasts or geo-nuts out there
have got a complete or fairly complete list of the geologic
separations at that most fascinating place?>>

Josh Smith wrote:

<Whatever the rocks at Sihetun are called, I haven't seen anyone argue
for them to be pulled out of the Jehol Group and put somewhere else,
so I am confident that we have virtually 100% agreement that these
rocks fall within the Jehol Group.

... snip...
As for this "Chaomidianzi Formation" that Ji et al. (1998) talk about
in the _Caudipteryx_ paper, it is a term that does not appear in print
anywhere nor is it in GEOREF.  It was cited in that paper in a
"Professional Papers on Stratigraphy" article that is in press.  I
assume from this (though we cannot be sure until that article comes
out) that Ji is feeling the pressure of those of us who are calling
for a Cretaceous age for Sihetun and is attempting to hold onto his
Jurassic age by dividing up the Yixian and creating a new formation;
one that he can then say is Jurassic in age, regardless of what we say
the Yixian is.  I would suspect that his reasoning for this centers on
the fact that up until the samples that I collected in July and those
that John Ostrom talked about last year at GSA, there were no
confident dates from Sihetun. Also, the stratigraphic information is
so bad in the Beipiao area that we are not certain of the relative
stratigraphic placement of the previous dating sites to the Sihetun

  This is pretty much what I needed. A clear-cut form on the Yixian
and Sihetun stratigraphy, and LO! Thanks, Josh.



  Couldn't agree more.

  Jaime A. Headden
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