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re:re:Extinction (was Religion)



John Alroy, et al.

Selected responses to last post (and I'm truly awed by the volume
and rapidity of responses!)
                  ____________________

>>>>" Dr. Schwimmer seems to have taken offense..."<<<<

Not in the least.


>>>>>" Before I start I should note that I have
passed my Ph.D. defense and finished my thesis.... "<<<<

Congratulations. (no cynicism meant)



>>>>"My quote of the Kerr article was just that, a direct quote.
Why slam me over it? The occurrence of a seismically-produced
tsunami on an enormous scale exactly at the K-T boundary seems
like an improbable coincidence to me, but, of course, this sort
of ad hoc, case by case assault on the data is exactly what you
should expect in phase d of a debate like this...."<<<<

One cannot quote a source in an argument without taking
responsibility for the intent.  I recall well that Duane Gish
frequently did this in a debate I had with him.



>>>>"I have checked the McLean letter (on volcanism for the K/T),
which you said was "a good starting place," and found it to be
very telling. His main point is that Science published 61
pro-impact papers from 1980 to 1993 and four "stricly nonimpact
items" in that interval..."<<<<

I know what is in the letter. I suggested this as a starting
point simply to frame the context. Read Jaeger's article, and the
others, and we can discuss substantial data.



>>>>"... I do have a recent reference on the Tornillo Formation
(Schiebout et al. 1987: J Geol 95,359), which specifically notes
that there is a 35 m barren zone devoid of known terrestrial
vertebrates that spans the boundary. Therefore, the Tornillo
Formation has nothing to do with this discussion.
It seems to me that Stan Friesen was correct in the first place
in noting that the only field area in which anything resembling a
true "gap" has been found is the Hell Creek area."<<<<

I have a paper at school (I believe by Tom Lehman, published
subsequent to Schiebout et al), showing that the Tornillo (Gp.)
straddles the boundary .  Lehman led an SVP field trip in Big
Bend in 1989 which I attended and demonstrated that there was
no apparent unconformity.  I will be glad to send the reference
tomorrow: I'd like to get this response posted tonight, so
forgive the lack of a citation here.



>>>>"It's hard to believe that after all this discussion I still
have to field casual ad hominem attacks like "I believe Mike
Williams has spent a lot of time in the Hell Creek outcrop and
has seen the evidence first hand.  Have you?""<<<<

You're right, I have been undiplomatic here.  My point was that
Williams and many others arguing for the apparent decrease in
dinosaur diversity are working from observations quite evident in
the field.  Literature argument has its limitations, as does
purely empirical field work.


>>>>"My point about sedimentation rates was that the MAXIMAL
duration of the 2 meter "gap" was on the scale of 40,000 years,
UNLESS there is a major hiatus in that interval..."<<<<

Not at all true.  Ager, and most modern sedimentologists, find
that there is NO NET GAIN IN SEDIMENTARY STRATA under normal
conditions.  Phrased otherwise, Ager shows that the stratigraphic
record is full of undetectable sedimentation gaps (diastems).
This is based on good actualistic data from modern coastal and
fluvial sedimentary environments.  The point is that it is naive
to assume any temporal rate for sedimentation.  Often, there is a
net *loss* over time in degrading alluvial environments, without
apparent signs.

Don't take my word for this, ask a clastic sedimentologist at
your school.


>>>>"I just came across an interesting quote in Raup's Nemesis
book to the effect that 61% of 500 professional geologists and
paleontologists in a 1984 poll accepted the evidence for an
impact at the K-T...."<<<<

Perhaps, but first, science does not procede by polls, and
second, I recall a poll taken at the SVP meeting in Rapid City,
1985(6?) by the NY Times on the same query. As I recall, of over
200 vertebrate paleontologists responding, fewer than a dozen
believed the impact scenario explained dinosaur extinction. Polls
will tell one what one wishes to interpret: ask any politician.



>>>>"This figure would surely be much higher in 1994, because
there wasn't even a decent candidate crater 10 years ago..."<<<<

Yes there was, the Manson structure in Iowa, subsequently
discredited.


>>>>"The comment on Meyerhoff is hardly worth replying to. At
this point I am starting to get the impression that Dr. Schwimmer
believes that "expert opinions" are not to be questioned by
anyone, regardless of how old the data are or whether they are
even published!"<<<<

This seems a bit ad hominem, but I'll skip that.  Meyerhoff's
paper is based on old data, but the interpretation is new. As I
stated, data are not subject to aging if they are originally
valid: opinions and interpretations should be current.  Nothing
said here or in press refutes their basic claim that Chicxulub is
volcanic and contains Cretaceous material inside.  This is not my
opinion, note, just a current, refereed paper in a leading
journal.



 >>>>"I am not comfortable with a vision of science that views
decision-making as an exclusive right of empiricists with
so-and-so many years of field experience, and theorists as
beneath contempt. This is made clear in Schwimmer's insulting
comment that I should "try doing some alpha field work"
myself...."<<<<

Again, I apologize for any insult given or taken.  My point is
that pure theoretics without any ground-truthing seems to me a
bit hollow. I have written a few things that would be considered
in part theoretical in my career too. I admit to a prejudice
against paleontologists presuming to describe events in times and
places they have never sampled. Call me old-fashioned.


>>>>"I agree that the K-T marine regression may have been an
important contributing factor in the extinction event. However,
it fails to explain the extremely rapid and severe extinction of
terrestrial mammals and plants at that time. Regressions of
similar magnitude occurred several times during the
Cenozoic..."<<<<

Not at all true.  The Paleocene Cannonball transgression down
Canada into the Dakotas was the last time marine waters entered
the craton beyond the marginal Gulf and Atlantic Coastal Plains.
(I might humbly suggest you check p. 532 in my book "Regional
Stratigraphy of North America,", W.J. Frazier and D.R. Schwimmer,
Plenum, NY 1987, 718p.)  Where did you get this notion?  The rest
of your discussion here is bottomless because the premise above
is false.
               __________________________________

Well, its been fun.  I have my first summer classes tomorrow, so
I'll give it a rest and let others respond at will.

David Schwimmer
Columbus College
schwimm@uscn.cc.uga.edu