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Re: Barungoyotian/Nemegtian environments and ages

--- "Jaime A. Headden" <qilongia@yahoo.com> wrote:
>   Barungoyotian is an AGE name, as in a Land Mammal
> Age, it doesn't refer
> to a period in which environment was stablem but
> through which faunal
> successions occured.

 Pinacosaurus was apparently replaced by Saichania and
Tarchia, but I don't think there was much faunal
succession until the Nemegtian.

> Formations through which are
> Barungoyotian are the
> Djadokhta Formation (Senonian or as young as lower
> Campanian) 

 As young as late or latest Campanian. The
Baynshirenian may not have ended until the end of the

.and the
> overlying (though not actually conforming in the
> various type sections
> which can be directly compared -- rather that
> "guessed" at as some have
> done) Barun Goyot Formation, which directly
> underlies the Nemegt Formation
> (both of which are Campanian and with possible
> Maastrichtian transition in
> the latter 

  Even the Barun Goyot is probably Maastrichtian, the
Nemegt almost certainly is, as Shuvalov wrote in The
Age of Dinosaurs in Russia and Mongolia. There are
Djadokhtan age beds in Borzongiin Gobi dated at c 73
Ma. Even the Djadokhtan period may extend to the end
of the Campanian. The overlying units, especially the
Nemegt, are Maastrichtian.

>given Faunal similarities to the upper
> Campanian Dinosaur Park
> and the lower Maastrichtian Horseshoe Canyon
> Formations.
>   The environments of the Djadokhta change from
> aeolian (arid, dominated
> by sand dunes -- imagine the smaller "ergs" of the
> Sahara, mostly flat
> rocky soil with sand dunes everywhere) intermixing
> with ponds and streams,
> towards a wetter estuarine yet still sandy
> environment. 
>   The Barun Goyot geologically resembles a wetter
> Djadokhta, but shows
> larger water activity and is typically more
> "muddier" in nature. 
>   The Nemegt would resemble a wetlands, which the
> Barun Goyot appears to
> transition into at Hermiin Tsab 

And at the type locality.

> svita in Russian),
> though both are dominated by sandstones, and the
> younger the more finely
> grained and more water-dominated they become.
>   Cheers,
> =====
> Jaime A. Headden
>   Little steps are often the hardest to take.  We
> are too used to making leaps in the face of
> adversity, that a simple skip is so hard to do.  We
> should all learn to walk soft, walk small, see the
> world around us rather than zoom by it.
> "Innocent, unbiased observation is a myth." --- P.B.
> Medawar (1969)
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