Re: Gondwana Buster!

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George wrote:
>To add my two-cents-of-data worth to the original request for literature
>citations concerning the GB, I note that on the A CORRELATED HISTORY OF
>EARTH color wall-chart (which is otherwise very nice; produced ty Pan
>Terra Inc of Afton MN, USA) the GB appears as a 300+ crater producer right
>at the Permian/Triassic boundary.  Thus the GB may have "busted" (ouch!)
>more than Gondwana -- it may have produced the "Mother of all Mass Extinctions"
>(to paraphrase the title of chapter 9 in Doug Erwin's excellent book on the
>same).
>
>Unfortunately for those of us who like to see some hard citations, there
>is no specific literature citation given for the GB on the one-page list
>of literature which accompanies the wall-chart (alas!), else I would be
>happy to pass it on in response to the original request for info.
>
>Please reply ON NET -- things have been a bit quiet lately, and this might
>be fun during Final Exam Season.
>
>George McGhee

Greetings George,

Thanks for the kind words about the "A Correlated History of Earth" wallchart.
It's kind of a touchy situation for me to offer comments on this since:
a) I am the president of the company that markets this product.
b) I am the author/designer of this particular product.
c) I respect the netetiquette of not being "commercial" on science groups,etc.
Having said that, I hope the net police will indulge me just this once so 
that I can respond to the request for refs. 
---
The refs that pertain to the P/Tr events (on the list that
comes with the wallchart) are:

- Earth's Near Death Experience, J. Alper, Earth Magazine, Jan. 1994.

[Probably the best piece to date describing Michael Rampino's P/Tr
model of a massive impact in southern Gondwana which may have
initiated the rifting of Gondwana and induced or intensified the huge
volcanic eruptions known as the Siberian Traps. The location of the
proposed 300km crater is shown as a circular gravity anomaly on
the ocean floor near the Falkland Islands. Metamorphic fold belts
surround ground zero and date to ~250mya. The wavelike rockforms
of the Cape Fold Belt in Africa(also dating to ~250mya)are viewed as
impact shockwave induced. The Siberian Traps eruptions(~250mya)
also accurred at that time. Disclaimer: I know Earth mag is not 
a peer reviewed journal but prudent information farmers harvest good
data wherever they can find it :-) Besides, I like the mag!]

-Astrogeological Events in China, Xu Dao-Yi, Yan Zheng, Qin-Wen,
Chai Zhi-Fang,Sun Yi-Win, He Jin-Wen,
Geological Publishing House, Beijing China,
Van Norstrand Reinhold, N.Y., Scottish American Press, 1989.
[Analysis (and pictures) of some P/Tr sections in China. Since
most of the P/Tr sections in North America are unconformities,
you have to look elsewhere to get a closer look at the actual
boundary interval. There is an exposure at Meishan which is
reminiscient of the Gubbio K/T section. A dark black siderophile
rich clay layer separates light colored Permian marine sediments
from Triassic and appears to preserve a record of contiguous
deposition across the boundary. The authors present lots of data
(extinction and geochemical) from Chinese sites and conclude the
a large impact event at the P/Tr is indeed an attractive model.]

-Geological and Biological Consequences of Giant Impacts,
D. J. McLaren, W.D. Goodfellow,
Ann. Rev. Earth Planet. Sci., vol. 18:123-171, 1990.
[A good overview of the major extinction horizons with evidence for
astrogeological components at many of them (including the P/Tr).
Includes data from other P/Tr areas such as Salt Range in Pakistan.]
 ---
I'm not sure who coined the term "Gondwana Buster" but I kinda
like it and hope it sticks. It has that nice ominous ring to it that
can stir imaginations. To contemplate an impact of this magnitude
is to envision Armageddon, the great and terrible Day of the Lord,
Ragnarok, the end of the Mayan Calendar, gourdes of ashes being
poured, Nostradamus' quatrains being fulfilled, an attack by malevolent
aliens, all out thermonuclear and biological war, and an IRS audit....
...all happening on the same day. The whole topic of astrogeological
events and their correlation to major extinctions is renowned for
sparking hot debates and getting lots of mammal fur flying! 

Every person be they a scientist or amateur has a different standard
of evidence before their "scale" is tipped in favor of some view. The
reason I included the GB structure as a crater on the "A Correlated
History of Earth" wallchart is that my "scale" was tipped in Jan.,1994.
This was one of the most controversial questions rumbling through
my mind as I prepared to go to press. Right up until the last day
I had the GB listed as a "possible major impact" ( just like the
Ordovician/Silurian boundary on the wallchart).

 I had recently received my copy of Earth Magazine in the mail and
read Joseph Alper's piece on Rampino's views...over and over...
I pulled out my P/Tr file and reviewed all the literature I had. I have 
access to the library at the U of MN and pulled virtually everything I
could find.  Literally, at the last minute, I concluded that Rampino's
GB model had a greater than 50/50 chance of being essentially correct.
There will obviously be challenges and refinements as new data comes
in but my current view is that any P/Tr extinction model that doesn't
include at least one mega-impact is inadequate. The energy release
of this impact most likely dwarfed the K/T-Chicxulub event.

I acknowledge that Rampino's GB crater would probably not get
"majority support" in mainstream science if you took some sort
of vote, whereas the K/T-Chicxulub structure probably would.
In most cases on the wallchart, I stuck with mainstream scientific
interpretations, while allowing a few controversies in for spice.
For instance, I took the liberty of graphing _Protoavis_ on the chart
as a triassic bird. In that case, I didn't agree with all of Chattergee's
interpretations, but it became clear in product reviews that it belonged
there for reference purposes and as a stimulus for discussing dino-bird
relationships in my most important market, i.e. the classroom.

To summarize some of the evidence for a major P/Tr impact:
-a very severe global mass extinction event featuring abrupt,
 conspicuous faunal changes in the fossil record.(Worldwide)
-siderophile/geochemical anomolies with probable astrogeological
 causes. (China, Pakistan, South. Alps)
-shifts in stable carbon isotope perturbation. (China and South. Alps)
-a sharp peak in microspherules of probable impact origin(China)
-a possible smoking cannon(crater) in the South Atlantic with unusual
 coeval metamorphism and folding in the surrounding area. This is
 *not* the Aranguainha Dome structure which at only 40km diameter
 was only a bump in the road in comparison, although the "Dome" might 
 be a related impact site from the same parent body(S/L 9 style).
-possible induced volcanism. The time correlation and relationship
 between GB and the Siberian Traps might be analagous to Chicxulub
 and the Deccan Traps.

As timing would have it, I am preparing some web material right
now on geologic boundaries, which will be available on June 1.
I am particularly interested in finding others (pros and amateurs)
who would like to work on a research project on geologic boundaries.
If you're interested, send me your email address, geographic locality
and area of interest, and I'll notify you when the webpage is ready and
furnish details about our research project. P.S. Please don't clog up the
list with responses, just send private email to pjanke@maroon.tc.umn.edu
and I'll inform you when everything is accessible. Perhaps some of us 
"believers" can develop a mechanism for productive research and avoid
yet another round of degenerate impact-theory flamewars which seem 
inevitable on the public lists.

---
Paul R. Janke
President, Pan Terra, Inc.
PO Box 392
Afton, MN 55001
fax (612)436-5292
pjanke@maroon.tc.umn.edu