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Re: Asian end-Cretaceous extinction and other news stories



On Mon, August 22, 2011 5:41 pm, Saint Abyssal wrote:
> How much cooler could northeast Asia be compared to the North Slope of
> Alaska? Evidently dinosaurs were doing just fine there during the
> Maastrichtian, if judged by the Pachyrhinosaurus bonebeds of the Prince
> Creek Formation. Not to mention Antarctica. I'm not sure I buy the cooling
> climate hypothesis as a credible means of dinosaur extinction, local or
> otherwise.

Don't know of too many people who take the idea of a general cooling as an
extinction agent for the K/Pg. However, an extended planetary cooling
(with cascading effects throughout the food web) is a different matter.
After all, wildlife does well enough at the latitude of Washington, DC
where we might get a a few weeks where the highs are below freezing every
year, but if it extended to months or years, that would be a catastrophe.

> I'm even more dubious about the sea level drop thing. Were dinosaurs
> really incapable of living in inland environments? The constant
> suggestions to the effect that sea level drops played a major role in
> dinosaur extinctions suggests that a lot of researchers seem to believe
> this, at least.

A) There is most definitely geological evidence for a eustatic regression
during the late Maastrichtian (granted, with some lower scale reversals
within it: this happens with all regressions). As a good reminder: the
youngest ammonite zone in the western U.S. is the Triceratops zone...

B) Nearly everyone who considers the Maastrichtian Regression as a serious
factor in the extinction doesn't think that the effects are direct onto
the dinosaurs. Rather, global and regional changes of climate (radically
different albedos & rainfall patterns; increased continentality of climate
[extremes of winter and summer]) and oceanography (huge reduction in
shallow marine surface area with corresponding smaller area for algal
productivity [and thus reduction in food available in the marine
ecosystems]; change in shallow circulation patterns, etc.) are the
suspected culprits.

And don't forget (as the authors of that news article seem to have): the
terminal Cretaceous event is SO MUCH MORE than the loss of non-avian
dinosaurs.

Thomas R. Holtz, Jr.
Email: tholtz@umd.edu   Phone: 301-405-4084
Office: Centreville 1216
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
http://www.geol.umd.edu/~tholtz/
Fax: 301-314-9661

Faculty Director, Science & Global Change Program, College Park Scholars
http://www.geol.umd.edu/sgc
Fax: 301-314-9843

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