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RE: My comments on pterosaur extinction



> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> David Marjanovic
>
> The volcanoes -- well. There's a wonderful book from I think 1998, called
> Night Comes To the Cretaceous, which says that in the Deccan, the
> iridium-containing K-T boundary layer lies in the middle of a sedimentary
> layer between two basalt beds, and the dinosaur fossils continue
> right up to
> it and stop there. There were no eruptions tens of thousands of
> years before
> and after the boundary. While global climate and suchlike was probably
> affected by the volcanoes, they apparently didn't cause the K-T mass
> extinction. _Basta_. =8-)
>
The data in Night Comes to the K is out of date.  More recently the
following has been published:
Hofman, C., G. Féraud & V. Courtillot.  2000.  40Ar/39Ar dating of mineral
separates and whole rocks from the Western Ghats lava pile: further
constraints on duration and age of the Deccan traps.  Earth and Planetary
Science Letters 180: 13-27.
(available online at
http://www.elsevier.nl/gej-ng/10/18/23/84/25/26/article.html).

(My initial dinolist posting about this can be found at:
http://www.cmnh.org/fun/dinosaur-archive/2000Aug/msg00090.html)

There's a lot of info in this paper, and in others on the Deccan, that
discuss that it is a complex series of units.  It wasn't an "all on/all off"
volcanic system; rather, there were eruptions going on in one part of the
field at one point, and another elsewhere later, with intertrappean
sediments being deposited in the meantime.  Thus, it is not appropriate to
say that there were no eruptions tens of thousands of years on either side
of the iridium spike: it may be true for one local spot, but not for the
whole of the Deccan field (and thus, not for the globabl effects).

Also, just as a reminder, were it not for the strong evidence of the K/T
impact the Deccan Traps would be the clear major player in the extinction,
especially as no other major mass extinction can be directly tied to a
bollide impact, whereas several other mass extinctions DO coincide with
other flood basalts.  Most notorious, of course, is the Permo-Triassic
event, when the largest mass extinction of the Phanerozoic coincides with
the largest flood basalt in the Phanerozoic.

> BTW, off-topic: The 6-million-year-old human has been named *Millennium
> ancestor*

Where was this published?  I hadn't heard that there had been anything more
than a news report on it (i.e., no scientific paper).

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796