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Re: Everything you know about the Iren Dabasu age is wrong...

--- "Thomas R. Holtz, Jr." <tholtz@geol.umd.edu wrote
> van Itterbeecka, J., D.J. Horne, P. Bultynck, and N.
> Vandenbergh. 2005.
>Four species of charophytes are described and
> illustrated from the Iren Nor site, together with
> eight species of ostracods,
> one of which (Cypridea irennorensis sp. nov.) is
> new. Contrary to the vertebrate data, both groups of
> microfossils indicate a latest
> Cretaceous age (Campanian?Maastrichtian) for the
> Iren Dabasu Formation, and suggest a possible
> correlation with the Nemegt
> Formation,

  What about gastropods? Is Mesolanistes present? And
Nemegtian turtles like Mongolemys? Are they present at
Iren Dabasu?

 which would allow the age estimation to
> be refined to latest Campanian?Early Maastrichtian.
> Possible correlation with the Nemegt?!?

 I don't believe it. There are radiometric dates
indicating a late Campanian age for Djadokhtan beds.
Russell and Jerzykiewicz  estimated the Nemegt was of
mid Maastrichtian age. AFAIK the Iren Dabasu and the
Nemegt have no large dinosaurs in common even though
the distance between the two formations is not very
great, and the Nemegt fauna  seems fairly widespread,
not just in Omnogov.

> Yeah, I knew
> the stratigraphy there was poorly understood, but
> the Iren Dabasu and Nemegt
> were traditionally considered as opposite ends of
> the stack of dinosaur bearing Late K sediments.

 Note that one of the authors above, van
Itterbeecka,is the same person who persuaded Godefroit
that the Tsagayan, with all its primitive or Campanian
aspect hadrosaurs, is late Maastrichtian in age i.e.
younger than the Nemegt, which seems roughly
equivalent to the upper Horseshoe Canyon. These age
estimates just don't make sense.

> Ah, well...
>               Thomas R. Holtz, Jr.
>       Senior Lecturer, Vertebrate Paleontology
> Department of Geology         Director, Earth, Life & Time
> Program
> University of Maryland                College Park Scholars
>       Mailing Address:
>               Building 237, Room 1117
>               College Park, MD  20742
> http://www.geol.umd.edu/~tholtz/
> http://www.geol.umd.edu/~jmerck/eltsite
> Phone:        301-405-4084    Email:  tholtz@geol.umd.edu
> Fax (Geol):  301-314-9661     Fax (CPS-ELT):
> 301-405-0796

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