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


Jaime A. Headden wrote:
> 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
> quarries.>
>   This is pretty much what I needed. A clear-cut form on the Yixian
> and Sihetun stratigraphy, and LO! Thanks, Josh.
        I suspect that is as clear-cut as it is going to get for a little 
while, anyway....(I need a vacation).


Josh Smith
Department of Geology
University of Pennsylvania
471 Hayden Hall
240 South 33rd Street
Philadelphia, PA  19104-6316
(215) 898-5630 (Office)
(215) 898-0964 (FAX)