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

Re: Paleocene dinos

Peter S. et al on this string -

        Keith Rigby, Jr. is at it again with his claims of Paleocene dinosaurs!
But instead of isolated teeth from Montana, this time he and his Noter Dame crew
claim to not only have articulated hadrosaur skeletons above the K/T boundary
layer, but eggs and nests, as well!  They are from a region of southwest China
(as I understood it); he and his workers have published only two abstracts
(sorry, I don't have refs handy!) on this.  Apparently, given the nature of the
beating his arguments took based on his Montana teeth, he's being ultra-cautious
before really announcing this one.  He claims that he and his workers are doing
the dating work (based on, he says, over 40 ash beds in the region) to insure
they are correct before publishing, but he mentions that the fossils are 500,000
years into the Paleocene.

        There are some problems with the tidbits of information I have on this:
Rigby mentioned that the ash beds are located on either side of the basin in
which the fossils were found; he made no mention of ash beds IN the basin itself
(I don't pretend to understand this one).  Before the ash beds, his claims of
Paleocene dinosaurs were based on the sematically ambiguous "they were found
associated with definite Paleocene mammal fossils."

        In discussion with Kirk Johnson, Denver Museum paleobotanist and also 
boundary worker, what this situation _really_ is, is this:  There is a layer of
sediment in which all the hadrosaur fossils were found; above that,
stratigraphically, are some "blank" layers, then a layer in which the Paleocene
mammal fossils were found.  No iridium layer, no boundary clay is apparently
preserved here, so drawing a definitive line at the boundary is difficult at
best!  Rigby thinks this means that the dinosaurs are Paleocene; most others,
I'm finding, are ambiguous, at least until he publishes.  (Notice also that in
this, the ash beds are missing.)

        Rigby hinted at his finds at a 1994 AAPG symposium on the K/T boundary 
Denver; I was fortunate enough to chat with him about it afterwards:  that's the
source of this information.  

                                                -- Jerry Harris
                                                Denver Museum of Natural History