[meteorite-list] The Manuel Benavides Craterwrong and Cratermania

From: Paul H. <oxytropidoceras_at_meteoritecentral.com>
Date: Fri, 19 Nov 2010 23:44:12 -0600
Message-ID: <20101120004412.5INZ1.125728.imail_at_eastrmwml38>

People having been using Google Earth for a number of purposes,
including the search for impact craters. Although Google Earth
has been useful in the search for impact structures and craters,
some people have been indulging in a cratermania in which any
circular feature and even a number of noncircular features are
instantly claimed to be either impact structures and craters
without a single shred of either ground truthing, literature review,
or hard evidence. One specific example is:

1. The Benavides Impact Structure: A large, multiple airburst,
geo-ablative impact structure.
http://craterhunter.wordpress.com/the-planetary-scaring-of-the-younger-dryas-impact-event/the-benivides-impact-structure/
http://tiny.cc/Benavides

This feature is described as:

"The semi circular ring of The Benavides Impact Structure
is 17 miles wide. Just across the border from Terlingua, Texas,
and Big Bend National Park, USA. "

and it is stated, "There is no volcanic vent here."

Unfortunately, recently published and very, very detailed
geologic mapping demonstrates beyond any shadow of a
doubt that the above statements are completely wrong.
The so-called "Benavides Impact Structure" is in fact a
volcanic caldera and would be more correctly called the
"Benavides Craterwrong."

This detailed geologic mapping, McDowell (2010), states
about the Benavides structure;

"The caldera is an unusual trap-door type with a hinge zone
on the southwest and two separate collapse and eruption
margins around the north and east. Its outer diameter is
approximately 25 km, which is unusually large for the
tuffs that erupted from it, suggestive of a shallow collapse.
Inflation or tumescence prior to the eruptions modified
a preexisting Laramide fold by bowing it outward toward
the north and east; a 31.5 Ma granitoid was intruded
into the fold axis, resulting in the formation of skarn
deposits in the surrounding limestones of the fold."

References Cited;

McDowell, F. W., 2010, Geologic Map of Manuel Benavides area,
Chihuahua, Mexico. Map and Chart no. 99. Geological Society of
America, Boulder, Colorado.
http://rock.geosociety.org/Bookstore/default.asp?oID=0&catID=2&pID=MCH099F

Yours,

Paul H.
Received on Sat 20 Nov 2010 12:44:12 AM PST