[meteorite-list] Paper Disputing Impact Origin of Coastal"Chevrons" Published

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Mon, 4 May 2009 14:54:04 -0500
Message-ID: <105740CC1529402694A8CBEF43FBA188_at_ATARIENGINE2>

Hi, Chevron Fans,

    The original paper's abstract reveals no
actual "shovel" geology had any part in this
work. First, they "reason that chevron-type
bed forms are common and are present far
enough from the coast to preclude tsunami
genesis." That is, they artibrarily preclude
any tsunamis "mega" enough to form chevrons,
but no one even knows how big tsunamis
have been in such rare events. That is, they
guarantee their conclusion by their choice
of initial conditions.

    Second, they evaluate "by modeling." They
"model the southern Madagascar case." They
"show that a modeled wave approach is inconsistent"
with chevrons. Computer models are, of course,
very useful, but due their extreme susceptibility
to their creator's bias, desires, and tweaking, they
prove largely nothing.

    Models convince the already-convinced and
are dismissed by the unconvinced (like me). I
at least am willing to say we don't know. I note
that they offer no suggestions as to how "large-
scale coastal bed forms" are created. Is there
any other demonstrated cause?

    The authors believe they are formed by winds.
The presence of marine fossils in the chevrons is
dismissed as being due to wind-transport of marine
fossils. Interesting. (Please, everybody who lives
in a windy area far from the sea, go out right now
and collect the seashells in your front yard; there
should be plenty of them.)

    There are ways to actually find out. They require
money, time, and a huge amount of excavating,
sedimentography, grain dating, lots of trained
people, years of work. Using that big computer
over in Building 7 is much faster and cheaper.

    In the press stories (which are just endless copies
of the same press release), the author mentions the
Washington State Palouse chevrons which are blythely
dismissed as impossible for a mega-tsunami to reach.
Hmm, are they part of the Cheney Palouse Scabland
Tract that was formed by sudden and immense mega-
floods that are the precise dynamic equivalent of a
mega-tsunami? Nice photos and dynamics from Bretz:
http://geology.isu.edu/Digital_Geology_Idaho/Module13/MissoulaFloodbyKeenanLee.pdf

    Whoops! Guess you shouldn't have mentioned
those Palouse ripples...


Sterling K. Webb
----------------------------------------------------------------------
----- Original Message -----
From: "Paul" <bristolia at yahoo.com>
To: <meteorite-list at meteoritecentral.com>
Sent: Monday, May 04, 2009 1:17 PM
Subject: [meteorite-list] Paper Disputing Impact Origin of
Coastal"Chevrons" Published


>
> The paper that diisputes the impact origin of coastal "chevrons" is:
>
> Bourgeois, J., and R. Weiss, "Chevrons" are not mega-tsunami
> deposits?A sedimentologic assessment. Geology. vol. 37,no.5,
> pp. 403-406.
>
> http://geology.gsapubs.org/cgi/content/abstract/37/5/403
>
> Previously noted popular news articles about this paper are:
>
> Past Tsunamis? Contrary To Recent Hypothesis, 'Chevrons'
> Are Not Evidence Of Megatsunamis, Science Daily, April 30, 2009,
> http://www.sciencedaily.com/releases/2009/04/090429091637.htm
>
> Contrary to recent hypothesis, 'chevrons' are not evidence
> of megatsunamis by Vince Stricherz, University of Washington,
> http://uwnews.washington.edu/ni/article.asp?articleID=49190
> http://www.eurekalert.org/pub_releases/2009-04/uow-ctr042409.php
>
> Ancient mega-tsunamis did not create mysterious chevrons,
> researchers say, Fish and Aquatic News, May 1, 2009
> http://www.aquaticcommunity.com/news/lib/246
>
> Coastal Formations Not Result of Asteroid Impact by Nancy
> Atkinson, Universe Today, May 1, 2009
> http://www.universetoday.com/2009/05/01/coastal-formations-not-result-of-asteroid-impact/
>
> Yours,
>
> Paul H.
>
>
>
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Received on Mon 04 May 2009 03:54:04 PM PDT