RE: Why non-avian dinosaurs weren't able to survive

["Thomas R. Holtz, Jr." <tholtz@umd.edu>]

> From: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu] On Behalf Of 
> Ruben Safir
> Sent: Tuesday, November 24, 2015 1:52 AM
> To: frank@blissnet.com; dinosaur@usc.edu
> Subject: Re: Why non-avian dinosaurs weren't able to survive
> 
> On 11/24/2015 12:59 AM, frank bliss wrote:
> > I’m still having trouble understanding why there aren’t massive beds
> > of dinosaurian bones at the top of the K sediments.  No such thing
> > here on my ranch.  I see fewer and fewer bone sites as I get closer to
> > the top
> 
> Easy answer.  Every spot in the strata where you have bones is a result of a 
> statistical probability of fossilization from before and after
> a specific time.  As you aproach the top, especially if it is a sudden die 
> off, you lose the source of half your probably candidates for any
> exact spot... and so you get the illusion of thinning population.
>
The Signor-Lipps effect

> Additionally, there was a great physical destruction.  Not much sediment.

Exactly: you only get fossils in a depositional environment. The effects of the 
Chicxulub impact didn't increase rates of sedimentation (well, except for 
tsunami deposits along the Gulf...), so you don't get any more chance of 
fossilization than other times.

Terrestrial deposition is very episodic and spotty: it isn't like deep sea or 
lake sedimentation. You only get overbank deposits when the river floods; you 
only get channel deposits when the channel is RIGHT at that spot, etc.

Thomas R. Holtz, Jr.
Email: tholtz@umd.edu         Phone: 301-405-4084
Senior Lecturer, Vertebrate Paleontology
Office: Geology 4106, 8000 Regents Dr., College Park MD 20742
Dept. of Geology, University of Maryland
http://www.geol.umd.edu/~tholtz/
Phone: 301-405-6965
Fax: 301-314-9661              

Faculty Director, Science & Global Change Program, College Park Scholars
Office: Centreville 1216, 4243 Valley Dr., College Park MD 20742
http://www.geol.umd.edu/sgc
Fax: 301-314-9843

Mailing Address:        Thomas R. Holtz, Jr.
                        Department of Geology
                        Building 237, Room 1117
                        8000 Regents Drive
                        University of Maryland
                        College Park, MD 20742-4211 USA