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Tsagayan/Udurchukan age-Campanian?



  I've repeatedly argued against the putative late
Maastrichtian age of the Tsagayan or Udurchukan
formation. Logically, a unit with abundant lambeosaurs
of Campanian aspect should be older. Yesterday, while
going over recent JVP issues, I noted information
which suggests the Tsagayan actually IS of Campanian
age.

 Bolotsky and Godefroit (June 2004 JVP, page 351)
cited research by Markevich and Bugdaeva (and
Godefroit) which indicated that all three Tsagayan or
Udurchukan localities-Blagoveschensk, Kundur and
Jiayin-and the Miho Group of Sakhalin Island, which
yielded Nipponosaurus- are synchronous and belong to
the Aquilapollenites subtilis/Wodehousesia spinata
palynozone, spposedly indicative of a late
Maastrichtian age.

 But ammonite evidence indicates that the unit which
yielded Nipponosaurus is of early Campanian age, if
not older!(March 2004 JVP, page 146) Apparently the
Aquilapollenites subtilis/Wodehousesia spinata
palynozone, the basis for a putative late Mastrichtian
age, can be as old as basal Campanian, perhaps even
late Santonian, in Asia. In view of the primitive
state of Amurosaurus, an early Campanian age seems
perfectly plausible, far more so than the age
currently given. The Tsagayan/Udurchukan localities
are not necessarily as old as early Campanian, but I
think they may all be Campanian, judging by their
parasaurolophines etc and definitely predate the
Nemegtian. It was probably only by the latter period-c
mid Maastrichtian-that Wodehouseia spinata, long
established in east Asia, spread to America-via the
same Bering bridge which enabled Saurolophus to spread
to Asia- and became representative of the late
Maastrichtian of NA.


                
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