Paleocene Dinosaurs

[DeepTimeIsotopes]

So I was looking through some “older” papers and found this one by Rigby et al. (1987)(pdf attached). They were looking at some of the rock formations specifically members of the Hell Creek Formation. In one area, they have a lot of river deposits from before and after the K-T boundary. In one of the river deposits from the Paleocene as dated by pollen fossils, contains ungulate mammal fossils and some dinosaur teeth specifically ceratopsian and theropod teeth as far as I understood. They recognize that the dinosaur fossils could have been eroded from the bank and fallen in but the fossils aren’t weathered like they should have been and the river wasn’t the right kind that would rework sediments. I’m not sure I believe their arguments but what do you guys think?

Rigby-et-al_1987_Paleocene-dinos.pdf

[Troodon]

Here is a 1990 paper that refutes this type of analysis at says its reworked which makes more sense

 

https://www.osti.gov/biblio/6212694-reworking-cretaceous-dinosaurs-paleocene-channel-deposits-upper-hell-creek-formation-montana

 

 

 

[DeepTimeIsotopes]

7 hours ago, Troodon said:

Here is a 1990 paper that refutes this type of analysis at says its reworked which makes more sense

 

https://www.osti.gov/biblio/6212694-reworking-cretaceous-dinosaurs-paleocene-channel-deposits-upper-hell-creek-formation-montana

 

 

 

Thanks, I thought the weathering argument was funky. 

[siteseer]

On 12/15/2019 at 8:19 AM, UtahFossilHunter said:

So I was looking through some “older” papers and found this one by Rigby et al. (1987)(pdf attached). They were looking at some of the rock formations specifically members of the Hell Creek Formation. In one area, they have a lot of river deposits from before and after the K-T boundary. In one of the river deposits from the Paleocene as dated by pollen fossils, contains ungulate mammal fossils and some dinosaur teeth specifically ceratopsian and theropod teeth as far as I understood. They recognize that the dinosaur fossils could have been eroded from the bank and fallen in but the fossils aren’t weathered like they should have been and the river wasn’t the right kind that would rework sediments. I’m not sure I believe their arguments but what do you guys think?

Rigby-et-al_1987_Paleocene-dinos.pdf

 

 

I remember that article and the nicely-illustrated volume that contains it.  Several years ago, i asked a paleontologist familiar with Hell creek in particular about that paper and he also said that the material had been reworked.  The odd thing I kept thinking about, though, was that the Paleocene-considered material they found contained only a subset of the diversity collected in the latest Cretaceous layer.  In other words if the fossils were reworked, why weren't any latest Cretaceous mammals found with the Paleocene ones?  Why were only a few of the dinosaur taxa found ?  There should have been more of a sample of most of the latest Cretaceous fauna rather than just a few of them.  Why would rare teeth be found and not even a few of the common ones if it was a random reworking.  The article also  brought up that they found a complete turtle shell, carapace and plastron, in that Paleocene deposit.  Anyone who has ever found turtle material knows that what you almost always find are just individual shell elements (or pieces of them).  For a complete shell to stay intact there couldn't have been much, if any, transport.

 

I remember Keith Rigby talking about this on a documentary not long after the publication of the volume.  He was already getting hammered because he was finding only isolated teeth and bones.  Even a partial skeleton would have bolstered his view and he said something like he would've loved to have delivered a dinosaur skeleton on the half-shell but they were rare anywhere in his study area (the layers) for that paper.

 

Jess

[doushantuo]

e.g:

 

Tertiary_Dinosaurs_in_the_Nanxiong_Basin_Southern_.pdf

 

e262.pdf

Direct U-Pb dating of Cretaceous and Paleocene dinosaur bones,San Juan Basin, New Mexico

Alan E. Koenig, Spencer G. Lucas, Leonid A. Neymark,Andrew B. Heckert, Robert M. Sullivan, Steven E. Jasinski,
and Denver W. Fowler

fasserepkydiscusKPG260.pdf

 

rsbl.2011.0470.pdf

Dinosaur extinction:closing the ‘3 m gap’
Tyler R. Lyson, Antoine Bercovici,Stephen G. B. Chester, Eric J. Sargis,Dean Pearson and Walter G. Joyce

Biol. Lett. (2011) 7, 925–928
doi:10.1098/rsbl.2011.0470

[DeepTimeIsotopes]

On 12/18/2019 at 11:52 PM, doushantuo said:

 

e262.pdf

Direct U-Pb dating of Cretaceous and Paleocene dinosaur bones,San Juan Basin, New Mexico

Alan E. Koenig, Spencer G. Lucas, Leonid A. Neymark,Andrew B. Heckert, Robert M. Sullivan, Steven E. Jasinski,
and Denver W. Fowler

fasserepkydiscusKPG260.pdf

Having done U-Pb dating on other material under some of the most ideal conditions, I agree with the comment on that paper. Another independent dating method would be needed.

[DeepTimeIsotopes]

On 12/18/2019 at 11:52 PM, doushantuo said:

 

Tertiary_Dinosaurs_in_the_Nanxiong_Basin_Southern_.pdf

 

rsbl.2011.0470.pdf

Dinosaur extinction:closing the ‘3 m gap’
Tyler R. Lyson, Antoine Bercovici,Stephen G. B. Chester, Eric J. Sargis,Dean Pearson and Walter G. Joyce

Biol. Lett. (2011) 7, 925–928
doi:10.1098/rsbl.2011.0470

But these two do bring up good points.