Re: Re: The End of Dinosaurs

[Thomas_R_HOLTZ@umail.umd.edu (th81)]

William Olewiler writes of Charles Pellegrino's ideas:

>>     During the dino era much of N. America, Europe, Asia, and Africa
>>were under water. And this high ratio of water to land surface
>>established a mild climate that dinos thrived in.

This has been a long established fact.  It is also the reason the
Cretaceous is called "Cretaceous" (i.e., the warm, shallow,
epicontinental seas provided for wonderful chalk-forming conditions).

>>    Then volcanic activity at the mid sea ridges subsided. The ridges
>>began to sink under their own weight, draining water from the
>>continents. As sea levels fell, oceanic and air currents were changed
>>drastically by the newly exposed land, with dramatic effects on
>>climates. This might have been a "major cofactor" in dinosaur
>>extinction.

The Maastrichtian Regression (regression = sea level fall) is also an
established fact.  North America, which was bisected into eastern and
western divisions by the Great Interior Seaway for much of the
Cretaceous, became a single landmass as the seaway retreated almost as
far as the current coastline on the Gulf Coast.  For this reason, the
uppermost ammonite zone for western North America is the "Triceratops
zone".

Similar events occured in the Turgai Straights (separating Europe and
Asia), within the European Archipelago, etc.

This would have had considerable effect on the climate, as can be
demonstrated by Climate Modeling programs.  The global albedo would
have dropped like a stone, the circulation patterns would be all
honked up, and both the sea conditions and terrestrial weather
patterns would be altered.  These changes may have had something to do
with the mid-Maastrichtian extinctions of rudists and North American
floral changes.  Bakker, of course, uses the Maastricthian Regression
as the key to his extinction theory, allowing previously separated
dinosaur populations to infect each other.  Regardless of the severity
of those effects, there are observable changes in dinosaur faunas at
this time (e.g., the arrival of Alamosaurus into the southern U.S.,
assuming that it is a migrant).

>>    Then volcanic activity at the mid sea ridges subsided. The ridges
>>began to sink under their own weight, draining water from the
>>continents. As sea levels fell, oceanic and air currents were changed
>>drastically by the newly exposed land, with dramatic effects on
>>climates. This might have been a "major cofactor" in dinosaur
>>extinction.

Leading Nick Reiman to ask:

>        Is there anyone out there who knows much about
> plate-techtonics?  Is this continetal movement recorded in the
> history of our planet?

Although the regression itself is a fact, the cause is still uncertain.
Changes in sea ridge volcanism is a major candidate.

> Plus, the dinosaurs were tough.  Spartans.  Virile.  I don't think
>that minor climate changes (the dropping of the continents) would
>have killed off the dinosaurs.

Minor changes, probably not.  The most extreme changes in the whole of
the Mesozoic, maybe.

Also, the climate changes per se may not be the killing mechanism.
Instead, changes (or extinction) of fodder, of previous habitat
ranges, etc., may have been the immediate killers.

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661

"There are some who call me...  Tim."