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Re: Paleocene hadrosaurs?



----- Original Message -----
From: <bh480@scn.org>
To: <dinosaur@usc.edu>
Sent: Saturday, December 21, 2002 3:37 AM
Subject: Paleocene hadrosaurs?


From: Ben Creisler bh480@scn.org
>In case this ref has not been mentioned yet:

Fassett, J, R.A. Zielinski, & J.R. Budahn, 2002. Dinosaurs
that did not die; evidence for Paleocene dinosaurs in the
Ojo Alamo Sandstone, San Juan Basin, New Mexico.
 In: Catastrophic events and mass extinctions; impacts and
beyond. (Eds.  Koeberl, C. & K. MacLeod): Special Paper -
Geological Society of America 356: 307-336. (2002).<

>SNIP<

>...These data show that a relatively diverse
assemblage of dinosaurs survived the end-Cretaceous
asteroid-impact extinction event of 65.5 Ma. The San Juan
Basin's Paleocene dinosaur fauna is herein named the
Alamoan fauna. Magnetic-polarity chronology shows that
these survivors lived for about one million years into the
Paleocene and then became extinct around 64.5 Ma....<

    Isn't there a fly in the "Paleocene hadrosaurs" ointment here, in that
the K/T impact was NOT 65.5 Ma, as alleged above, but was, according to the
dating I've seen for the impact event, 64.5 to 65 Ma?

    And does "palynologic and paleomagnetic" dating really provide the kind
of accuracy one needs to successfully allege the survival of non-avian
dinosaurs at any appreciable time beyond the K/T impact event(s)?

    One might also wonder what effect a K/T impact-created tsunami (which
conceivably might have reached into that area of New Mexico) could have had
upon the items and area under discussion, especially if 'pooling' (on a
quite large scale) of water might have occurred that later broke through its
confines and re-buried or re-deposited bones dislodged from the Late
Cretaceous, thereby also distorting their isotopic signature to more
resemble Paleocene material.

    If what Fassett,  Zielinski, and Budahn seem to be asserting (Note that
I've only read the referenced post, not the paper.) is true, it would be
exciting and important news; but I suspect the jury is still out on this one
and that, when a consensus comes, it may provide a disappointment for the
authors.

    Ray Stanford
    Mesozoic Track Project
    Maryland, USA

"You know my method.  It is founded upon the observance of trifles." --
Sherlock Holmes in The Boscombe Valley Mystery