RE: Extinction

[Phillip Bigelow <bh162@scn.org>]

Uhhh...  Not to throw a wrench into the smoothly running machinery of this
discussion, but, question:  Was the trackway located below a known K-T
boundary layer (~2 cm-thick layer containing iridium spike, shocked
quartz, spherules, soot, etc.), OR was the trackway found in a zone that
is *inferred* to be at K-T boundary because it appears to be at the same
stratigraphic level as other known boundary layers in the formation?

A BIG difference in terms of the recoverable science (and as you can tell
from my question, I haven't read this particular Lockley book!)

In the vast majority of the uppermost section of the Hell Creek Formation,
the K-T boundary bed is missing, either because of Paleocene bioturbation,
or because of localized intraformational unconformities (intervening
erosion after the fallout layer was deposited).  Therefore, for the vast
majority of the biostratigraphy of the Hell Creek Formation, the exact
TIME boundary is unknown, and is instead extrapolated.  High-resolution
biostratigraphers are old friends with this phenomenon, particularly those
people who work on centimeter-scale stratigraphy. Few other
biostratigraphers totally grasp the concept as readily, particularly those
who work on paleo-megafauna in terrestrial settings. 

                     <pb>
--
"Gentlemen!  You can't fight in here!  This is a war room!"
>From Dr. Strangelove



On Fri, 24 Mar 2000, Steve  Brusatte wrote:

> On Fri, 24 Mar 2000 07:31:08   Nathan Myhrvold wrote:
> >I believe that there is trackway evidence even closer that 1 meter to the KT
> >boundary.
> >
> >Nathan
> >
> 
> Yes, Nathan is correct.  This is spelled out in Lockley's book The Eternal 
> Trail.  The tracks were actually found much less than 1 meter, as Nathan 
> specified.  In 1990, on a field trip to southern Colorado, Lockely discovered 
> tracks 15 inches (37 cm) below the boundary.  He didn't specify what dinosaur 
> these tracks came from, but regardless they are a good indication that 
> dinosaurs (at least some of them) were still thriving close to the KT 
> boundary.
> 
> Steve
> http://www.geocities.com/stegob
> 
> >-----Original Message-----
> >From: Dinogeorge@aol.com [mailto:Dinogeorge@aol.com]
> >Sent: Thursday, March 23, 2000 11:29 PM
> >To: philidor11@snet.net
> >Cc: dinosaur@usc.edu
> >Subject: Re: Extinction
> >
> >
> >In a message dated 3/24/00 0:34:28 AM EST, philidor11@snet.net writes:
> >
> ><< Please remember that no dinosaur fossils have been found close to the K/T
> > boundary.  A mathematical analysis has demonstrated that there might still
> > have been dinos extant to go extinct at impact, but the same analysis
> > demonstrates equally that some remnants might have survived for some time
> > afterwards. >>